CHEMICAL COAGULATION AND THE
ELECTROKINETIC POTENTIAL
OF SUSPENDED
PARTICLES IN WATER AND SEWAGE

Thesis for the Degree of M. S.
MICHIGAN STATE COLLEGE

Dorian H. Dickman ' '
1938

 

 

 

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CHEMICAL comumxon .,
AND THE
Emeraoxmmxc POTENTIAL
or
SUSPENDED PARTICLES
IN

WATER AND SEWAGE

h I

THE-.2946

 

 

1.133818

Submitted to the Graduate Faculty
at the

MICHIGAN STATE COLLEGE
of
AGRICULCURE AND.APPLIED SCIENCE

1n
Partial Inltillment at the Requirements for

tho Dogroo
[ASTER or SCIENCE
by

Dorltn.Honzy.2;ggnan
1930

11 53330-1.

TABLE OF CONTENTS

Page
Acknowledgment ..................... 1
Introduction ....................... 3
Scope of the Problem ............... 5
Survey of the Literature ........... 8
Iheory ............................. 18
Experimental ....................... 69
Results ............................ 89
Discussion ......................... 146
Summary ............................ 155

Bibliography

ACKNOWLEDGMENT

10 Ir» 3. I. Eldridge for his guidance and his
thoughtful and timely suggestions in connection with
the experimental aspects of this problem and for his
kindness and patience during the long months when
little progress seemed to be made; to Prof. H. E.
Publow whose keen appreciation of the problems and
opportunities existing in the field of Chemical
Engineering and whose years of close, friendly contact
with students has rendered his advise and suggestions
in the choice of a problem of great value and for his
generous cooperation in arranging schedules and
credits; to Dr. W. L..Mallmann tor the use or his
electrophoresis equipment; to the Dean 01 Engineering
for his permission to use laboratories at various
hours of the day or night; to the Department of
Chemistry, the Department of. Chemical Engineering
and the Department of Sanitary Engineering for the
use of chemicals, instruments and laboratory facili-
ties, without all 01 Which this work would have been
impossible, the writer wishes to express his sincere
appreciation.

The infinitesimal contribution which this work
makes to the limitless knowledge already compiled

before this writer knew the light of day, will

scarcely be noticed, but he will remember the priceless
lessons gleaned Irom hours in the laboratory and will

w carry the memories of. those associations close to his

heart until these pages are yellowed by time.

INTRODUCTION

Although the clarification of water and sewage
by means of chemical agents is an old and well
established process, there still remains a great
number of perplexing problems. Satisfactory solutions
to these problems grow increasingly desirable as the
return to chemical coagulation practice becomes more
general from,year to year. Of primary importance is
the problem of being able to predict what conditions
are optimum.for the clarification of any particular
sewage or water. Heretofore however, the prediction
of optimum conditions even for specific waters or
eewages has been an impossibility.

Since the present costly and inconvenient cut
and try methods are manifestly very unsatisfactory (8).
it was suggested by Mr. E. F. Eldridge, the writer's
adviser in this work, that perhaps a detailed study
of the fundamental mechanics actually taking place
in coagulation processes would lead to a satisfactory
solution of this problem. Now it is a matter of
common knowledge that the flocculation of suspended
materials by the use of chemical agents is a typical
colloidal phenomina (1) (at (a) (4); so it is only
legical to assume that the application of the

theoretical principles and well established practices
of colloidal chemistry to the study of'this problem
would serve to explain more clearly what does actually
happen during the clarification of water or sewage by
chemical means.

.A study of the theory of colloidal suspensions
reveals that their stability is dependent upon the
intensity of an electrical charge surrounding each
tiny suspended particle (5) (6) and that the addition
of coagulants alters this charge permitting floccu-
lation of the particles and subsequent precipitation.
.Apparently then, the fundamentals of clarification
are tied up with this charge, hence a study of its
behavior during the addition of coagulants would
serve as an excellent guide in attempts to discover
a solution to the problem of predicting optimum
conditions for the coagulation of suspended matter

in.water or sewage.

80023 01 THE PROBLEI

Since this problem undertakes the study of the
charge on suspended particles, it becomes necessary
to develop a means of measuring its intensity.
Though this matter is mentioned frequently in
theoretical discussions and is treated with rather
matter of fact unconcern, still the development of
a practical arrangement suitable for the investi-
gation of turbid waters or sewages requires some
little thought and study. It becomes the first
major objective to be included in this work.

Upon the development of a satisfactory
arrangement for the measurement of the charge, the
study of a second and more important phase,
centered around the addition of coagulants and the
resultant change in electrokinetic potential of
the suspended particles in sewage, is undertaken.
Due to its apparent importance in explaining the
actual mechanics of coagulation, the greatest
portion of time spent in the laboratory was devoted
to study of this phase.

Isny workers have given this problem of
predicting optimum conditions for coagulation a

great amount of study, consequently it seemed

desirable to attempt to correlate such of their
results as were well established and commonly
'accepted with any that might be developed in the
present work. This third important point therefore,
is carried out simultaneously with the second phase
of the work insofar as practicable. I

How in dealing with highly technical problems
involving the application of numerous theories and
mathematical principles, there is a tendency to
forget the practical or useful aspects. Many
workers are satisfied with merely proving the
correctness of theoretical assumptions or developing
new theories from work carried out in the laboratory.
Although efforts of this nature are very commendable,
still there remains the equally essential task of
utilizing these theoretical principles to the
greatest possible extent in practical everyday
processes. It is to this latter task that the
engineer has dedicated himself. Therefore, the
fourth important matter to be emphasized throughout
this work is the visualization of any practical
applications as might possibly be developed from
such theoretical principles as might be established.

Summarised briefly then, the scope of this work

consists of:

I.

II.

III.

IV.

Measurement of the electrokinetic potential
of suspended particles in water and sewage.
Observation of its behavior during
coagulation.

Correlation of changes in various other
conditions with change of the electrokinetic
potential.

Visualization of practical applications.

6031'! 03 Ill LIIIBAIUEI

HISTORY
Ancient: ‘

Water purification.by chemical agents is so
ancient that its origin is completely obscured by
the shadows of time. Records indicate that the
practice was well known in China and India thousands
of years ago. Indeed it was the common custom for
the ancient Chinese and Egyptians to put alum in
their water tube for clarification purposes (9).
Beautiful artistry which the Egyptians loved to
place in their magnificient temples and elaborate
tombs frequently depicts the treatment of water with
chemical agents. From the diligently prepared
medical lore of the Sanskrit, methods of purification
employing the use of sunlight, charcoal filters and
treatment with copper are set forth in great detail.
Also in the Bible water purification by the addition
of salt is mentioned (10).

llarly:
lrom the time of the ancients until 1762, water
purification was not mentioned in literature. In that
year'an.English.patent was granted to de Boissieu for

the purification of dirty water by a chemical process,
which is the first record of any patent being granted
fer obs-deal coagulation, although during the next
hundred years a great number of similar patents were
granted indicating the rapid gain in favor which the
process had achieved. is a matter of fact, the process
spread with such rapidity throughout the various
eivilised countries of the world that its further
dcvelcpmcnt can best be traced.by following the
progress in each individual country.

mm:

The peculiar combination of circumstances,
such as Lord Lister's momentous work.with disinfec-
tants and Koch's remarkable discovery of pathogens
and their presence in water and sewage, together with
the concentration of population served to arouse
English public opinion first of all, to the necessity
of reform in public sanitation. Ii report from the
Emyal Sewage Commission in 1865 recommended land
treatment and stated that chemicals could not render
sewage non-putrescible although they could make it
clear. The Second Royal Commission on Rivers
Pollution in 1870 ranked in order, filtration,

irrigation and chemical processes in the removal of

suspended organic matter, but pointed out that land
treatment removed twice as much disolved organic
matter. Plain sedimentation was used for most
treatment, but in some instances chemical methods
were recommended, lime being most frequently
mentioned.as a coagulant.

.During the next forty years the process changed
but little although Sanford tried ten different
methods, Birmingham seven and almost every large
city several. In 1870 an "A B 0" process, using
alum, blood, charcoal and clay was boomed because
of the high fertilizer value of the sludge and soon
there were two hundred plants in England using this
"A B 0" type of treatment. Unfortunately however,
the effluent while clear was still putrescible and
the fertilizer value of the sludge was lost due to
high costs of drying. Up to this time the city of
Iondon had been discharging its sewage into the
Thames River, but this practice became so objection-
able that public sentiment was aroused and a
chemical precipitation plant was built. the solids
removed.by this method were hauled to sea and dumped.
Though not entirely satisfactory this method was
utilised until the World war. it that time however,

it was abandoned because of the high cost and lack

10

ll

of chemicals. Glasgow with its free acid and iron
wastes from wire mills found that an alum-lime
system worked efficiently. While at Salford a crude
alum, "Alumina-ferric", was used until 1926, when
trickling filters were adopted. Leeds with peculiar
trade wastes found septic tanks unsatisfactory and
abandoned them in favor of chemical precipitation
combined with trickling filters.

Although a great many English cities had adopted-
chemical methods for treatment of sewages, still the
results were not entirely satisfactory. The partial
failure of sedimentation and blasted hopes of
financial gain through sludge recovery led the
Second Royal Commission in 1908 to limit the use of
chemical processes to strong sewagee and those
containing trade wastes. By 1910 the process had
passed from favor and most plants were converted to

biological and settling processes.

NW:

The development of chemical coagulation processes
in France were very similar to those in England,
except that in France the practice never became so

general. In 1874 the Seine Pollution Commission
reported that chemical methods, particularly with

12

alum, were unsatisfactory. However, the French
favored the adoption of sewage farming methods
rather than the biological methods which were
developed in England.

9.2mm:

Germany in 1890 following the English example,
adopted chemical methods in several plants. At
Leipzig, an iron salt was employed which gave better
results than at either Glasgow or London, because of
the nature of the sewage. Frankfort-on-thaeflain and
. leisbaden were both operating chemical treatment
plants by 1890. Unlike the French, or the English,
the Germans took to mechanical methods such as
channical screening and sedimentation when chemical

methods were found to be unsatisfactory.

Mme =

The first chemical precipitation plant to be
used in the United States was completed in 1886, and
several plants were installed during the next ten
years. Worohester, Mass. was the first.American city
to treat sewage before it was discharged into streams.
This particular sewage contained iron trade wastes,

making it ideal for lime treatment. The process was

 

 

.3. ‘W H, fig”:

 

13

used from 1890 until 1925, when Imhoff tanks and
trickling filters were adopted. The first alum

plant was built at Somersville, N. J. in 1887, and
that same year.Alpheus Hyatt was granted a United
States Patent for the alum process. Providence, B. I.
built the largest chemical coagulation plant in the
United States. This plant remained in use for thirty
years or until 1931, at which time it was remodeled
to an activated sludge system. Some of the other
American cities that have used chemical precipitation
at one time or another are East Orange, Long Branch,
mystic Valley, White Plains, Sheepshcad Bay, Canton,
Chatauqua and the Chicago Fair of 1893. But due to
the rapid development of biological methods, chemical

treatment never gained much favor in this country.

Recent:

During the recent years due to improved methods
of handling and decreased costs, chemical methods have
been more widely used (12). It has been found, too,
that the use of chemical ccagulants is imperitive at
many water supply and sewage disposal plants during
certain annual critical periods in order to remain

within certain prescribed limits (13).

l4

GIJIO! OI'BEUD!

a brief discussion of the object or purpose of
sewage disposal and water treatment would doubtless
lead to a better understanding of the problems
involved; therefore a few of the more important
aspects will be considered although it must be
remembered that in no way can such brief treatment
be considered complete.

Originally it was the custom.for nearly every
.American city to discharge its sewage directly into
convenient streams without any attempt at treatment
whatsoever. This process was entirely satisfactory
during the pioneer days when the population was not
so dense, because at that time streams were able to
undergo a natural process of self purification,
since they were not ever burdened with organic matter.
Ior instance, the sewage from Chicago, after passing
successively through the Drainage Canal, the Des
Plains, Illinois and Mississippi Rivers, reached
at. Louis, a distance of 270 miles, in fairly
satisfactory condition due to the self purifying
action of these waters (16).

Because of the concentration of american population

into more limited areas however, the discharge of

ill}! I! nlwrr clungfiinuq 4.. .

15

organic matter into streams has become so great that
.they have become greatly overburdened. The former
se1f~purification processes have been greatly
hampered, or in many cases entirely halted and in
their place noxious, unpleasant and truly dangerous
partial decomposition processes have developed. I
Through experience it has been found that more than
one part of sewage in forty parts of water dangerously
overloads a stream. Another serious effect of this
promiscious discharge of sewage has been to render
practically every source of surface water unsafe for
human consumption without preliminary treatment.
Iron bacteriological studies, it has been well
established that polluted water supplies are the
source of a great number of diseases (14). The
diagram ( on the following page) serves very aptly
to illustrate this fact (15).

Moreover, Sanitary Engineers have shown that
deaths and sickness from other than water-borne
origin, are also prevented by water treatment. In
the diagram for instance, if the death rates for
other diseases (represented.by Aland B) were plotted
'along with that'for typhoid fever, they would show
marked decreases very closely parallel to the decreases

in the typhoid fever death rate. This has been termed

 

. ides vi.‘n.

 

ii...

16

the Kills-Reinke phenomenon and when reduced to
mathematical terms it has been found that as a result
of each death from typhoid fever that can be prevented,
three or four deaths from non-water-borne diseases are
are avoided. 'This mathematical principle is known as

Karen's theorem.

Deaths from Typhoid Fever
at
.Albany, New York

 

 

 

 

 

 

 

water ********xxxxxxxxoooooooo
Supply"
800
-Deaths per _
604*______,_____._-_I
100 ' .
l— - — --.
Thousand ‘0‘}________i,: L - ___.- _
--.....-....1
L-.. --.....---
20w 1
Year‘y*
1890 1900 1910 1920 1930
myphoid deaths. *** Impure water.

-»-u—- Deaths from disease A.* xxx Over half supply clarified.
-------- Deaths from disease B.* ooo Clarified water (filtered).

l"lion-waterborne.

 

 

17

lrom.the preceding considerations, it is not
difficult to understand the necessity of processes
which will remove dangerous pathogens from water
supplies or which lessen the over burdening discharge
of organic matter into streams that later possibly
become sources of water supply themselves. In this
letter connection, Mahr has pointed out that sludge
is a great deal more difficult for a river to take
care of than the same quantity of organic material
in disolved form. He also emphasizes the necessity
of preventing a river or stream from being over

loaded with sewage (17).

18

euros:
CHEMICAL COHEIDERAIIOHS

Methods of Coagulation

In 1901, Biltz and Krohnke divided the methods
of clarification of water and sewage into three
classes namely, (a) mechanical, (b) biological and
(0) chemical. Since the scope of this work includes
only the chemical—processes, no attempt is made to
develop the theories relating to the other methods.
furthermore since, in order to prevent this problem
from becoming too involved and also for the sake
of uniformity, the later investigations included in
this work are limited to the studies of sewage
coagulation and therefore most of the theories
discussed are those which relate more or less to
sewage clarification, although they are equally

applicable to water clarification processes.

Colloidal Nature of Sewage
A review of the literature reveals a great
number of investigations which indicate the colloidal
nature ef sewage. Biltz and Krohnke held that sewage
particles are negatively charged while such

lull-III is apt» .:..

n“ .l on

 

 

19

ooagulants as ferric chloride are positively charged.
Dunbar, Jones and Travis ascribe the phenomina of
coagulation to surface attractions. Harrison points
out that color in water is due to colloidal solutions
of organic matter such as humic acids, gallates,
tannates, or salicylates or in many cases due to the
combination of high alkalinity and high iron content.
. He also states that these colloidal materials may be
either positively or negatively charged (18); Seville
also obtained similar results from his work(l9).
Upon investigation of the humic acid type of coloring
matter in water, Miller found that it was due to
negatively charged colloids (20). Spencer's theory
is that to render particles mutually attractive is

to end their colloidal state.

As soon as mutual attraction arises, agglomeration
takes place and the colloidal solution becomes a full
flee that steadily shrinks by packing together and
preciptates because the mutual attraction of the
particles in the flee is so great that their "gluey"
er stabilizing properties vanish. He points out i
that particles in colloidal solutions have electrical
charges either positive or negative, but mmtually
repellent: if they are'positive they can be
precipitated with anions, and if negative with

 

. Bil...

 

20

cathicns (as).

Babbitt and Doland suggest that the addition
of chemicals to water form an insoluble precipitate
which adsorbs and entrains suspended colloidal
' matter (8). Prom summaries of previous studies
of clarification, Norgard.ccncludes that coagulation
with IeGlg is the reduction of the charge upon the
suspended particles by colloidal ferric oxide,
which has a positive charge due to the adsrption
of ferric ions; the mutual neutralization of the
charges causes coagulation (23). Eldridge points
out that the object of chemical coagulation of
sewage is to remove colloidal material by
flocculation. Upon addition to water, various
ferric oxide hydrates are formed which carry a
positive charge in acid and a negative charge in
alkaline medium. River water, containing negative
cellcids, requires the addition of an excess of
positively charged ferric oxides (12). In detailed
studies of natural coagulation of river water, Mom
found that colloidal aluminum oxide in the clay of
the TJiliwcng River (Dutch Indies), was the
coagulating factor proper and concluded that since
this agent has only a weak discharging power, its
effect has to be ascribed to its strong coalescing

21

or flocculating power (24).

Charge on Suspended Particles

Irom the foregoing considerations, there can be
little doubt as to the colloidal nature of chemical
clarification processes employed in the treatment of
water and sewage. The next logical step therefore
in the study of this problem.is the investigation
of the pertinent theories and practices of colloidal
chemistry. Gortner has termed the minute suspended
particles in a colloidal system, micelles, and'
assumes that they possess either a negative or

positive charge (1).

wmmm:

According to the almost classical Helmholtz
double layer theory, on the surface of each tiny
micelle is a layer of electrical charges, which,
being alike are mutually repellent and tend to
hold the particles in a state of suspension.
Very near and surrounding this first layer, but
contained in the dispersing medium, is a second
layer opposite in charge from the first. This
may be graphically illustrated as follows:

Helmholtz Double Layer Theory
Illustrated

E:
I

Micelle.

E3 - Di spersing medium.
- - Negative charge.

- - Positive charge.

Baum:

The causes of this charge have long been a
matter of controversy, but the most plausible
explanation has been offered by.Michaeli (1), who
classifies them as being due to: I .

I. Teresa of residual valence which cause
oriented absorption: for instance it is well known
that a very stable sol can be readily prepared from
silver bromide. eAlso the charge on these silver
bromide micelles can be reversed through their

isoelectric point by the addition of certain ions.

82

 

., all. r Ann... .11

 

23

lichaeli explains incidentally, that the isoelectric
point is that particular state at which there is

no difference in potential between the solid phase
(surface of the micelle) and the liquid phase
(dispersing medium). Now this charge may easily be
explained by assuming in the case of the silver
bromide sol, that the crystals of silver bromide
composing the micelle possesses residual valence
forces which serve to absorb either negative bromide
ions, if they are in excess, or positive silver ions
if they are in excess and which gives the micelle
its charge.

Cause of Micelle Charge

Illustrated
:3: ‘B.’

r’B;
as 3".

3‘1
4

‘\3:

 

 

3: ’4 :1.- h;
«a - Residual valence forces.
1 - ‘Bromine atoms.
0 - Silver atoms.

Br‘ - Bromide ions.

24

II. Forces of dissociation which causes exchange
adsorption: As an example in the dissociation of
ferric hydorxide, negative hydroxyl ions are given
into solution and the corresponding positive charge
of the ferric ion remains on the micelle. Since
the negative charge must remain in the vicinity of
the positive due to mutual attraction, a double
layer is set up.

III. Spontaneous distribution of ions at the
free surface which comes into play in these substances
incapable of dissociation and which do not react
chemically: Of such nature is cellulose, collodian,
air bubbles, colloidal carbon, and various hydro
(carbons. Michaeli assumes that there is a
selective adsorptivc influence on the part of the
aqueous phase (dispersing medium). Also by assuming
that the hydroxyl ion is more capillary active than
the hydrogen ion. In this phase certain hydroxyl
ions should enter more clOsely to the dispersing
phase so that there would be a greater concentration
of hydroxyl ions at this point, thereby setting up
a double layer.

Summarised briefly then the cause of the charge

present in a micelle is due to:

25

1. Capture of ions by micelle (adsorption).
II. Ionization of material composing the particle.
III. Electrification by contact with dispersing

medium similar to wax rod and wool phenomena.

Was:

Here important than the cause however, is the
significance of the charge on suspended particles,
because it has been found through experimentation
that the stability of a colloidal system is closely
related to the intensity of the charge on the
suspended particles. The next logical step in the
study of the colloidal aspects of sewage therefore
is to review the work that has been done toward
measuring the intensity of this charge. Among the
first scientists to investigate this particular
aspect of colloid chemistry was H. Freundlich, who
termed the double layer properties and behavior of
electrokinetic phenomina in order to differentiate
between thermo-dynamic phenomina, which is entirely
different. He pointed out that in a heterogeneous
system, having at least one liquid phase, relative
mechanical motion occurs at the phase boundaries

upon the application of an electromotivc force or

26

conversely, an e. m. f. will be produced as a result
of relative mechanical motion between the two phases.
A colloidal suSpension in reality then becomes an
electric motor or generator; movement between the
oppositely charged layers being either the cause

or the result of an electromotivc force. In his
early investigations, Freundlich found that the

e. m. f. varied directly with the velocity of the
interphase and also varied directly with the
intensity of the electrokinetic potential across

the interphasetl). From this work a number of
methods were divised for measuring the charge on

suspended particles.

mm:
'tl). Streaming Potential.
In experiments conducted by Ereundlich
and his co~workers, liquid was forced through
capillary tubes under measured hydrostatic pressure
and the resulting difference in potential across the
ends of the tubes was measured by means of a potentio-
meter. The e. m. f. thus obtained was called, "streaming
potential" by Freundlich, and.was found to vary
directly with the hydrostatic pressure and kind of

27

glass used, but was constant for all sizes, shapes
and lengths of capillaries (25) (26) (27).
Iheoretically the charge on the glass was
closely held while that on the liquid phase was
carried along with the liquid; thus producing
motion at the interphase and the resultant e. m. f.
or streaming potential. Since this s. m. f. is
directly proportional to the charge on the
capillary, the streaming potential method is most
useful for determining the charge on porous or
fibrous material through which liquid can be

forced.

(B). Electroendosmosis.

Many times instead of forcing liquid
through the-capillary openings in porous or fibrous
material, it is desirable to hold them regidly in
place in form of a diaphragm and by means of an
applied electromotive force and cause the liquid to
move through them. This process is known as
electroendosmosis, and besides being useful in the
study of electrokinetic potentials, it has
ccmmereiel use in treating photographic emulsions
(28), also for electrical dewatering of clay and
slurry (29).

28

(0). Sedimentation potential.

In most colloidal systems, instead of
being held in one continuous surface, as for instance
on glass capillaries, the charge are held at the
interphase between the liquid and tiny particles in
suspension. If such a suspension were to be placed
into a tube and allowed to settle, a difference in
‘ potential would be set up between the top and the
bottom of the tube due to the movement of the
particles through the liquid as they settle. This
e. m. f. has been termed sedimentation potential,
and although directly proportional to the charge
on the particles, this streaming potential method
is not widely employed because of the experimental

difficulties involved.

(D). cataphoresis.

More practical than sedimentation
potential methods, in fact the most widely used of
any of the methods for studying the charge on
suspended particles, is the process known 3'

cataphoresis. Though many variations have been
develcped, the process fundamentally consists of

measuring the velocity of suspended particles

through the dispersing medium when an electromotivc

29

force is applied to the system. The velocity of
migration when other things are constant, is
directly proportional to the intensity of the
electrokinetic potential across the interphase.

Summarized briefly then, the various methods
for determination of the charge on a colloidal
surface are:

(A). Streaming potential.

(B). Electroendosmosis.

(G). Sedimentation potential.

(D). Cataphoresis.

“THEME IGAI. 00] 311mm ION 3

Because of their greater usefulness any
theories or principles which might be developed
are reduced to mathematical terms. Thus, in the
ease of theories relating to the electrokinetic
phenomins of suspended particles,.all the
experimental work conducted regardless of the
method chosen was reduced to mathematical terms.
In the gradual evolution of various principles a
great number of formulae were prbposed and many

were discarded. From the perplexing maize Perrin,

30

perhaps, has developed the most complete and logical
formula for measuring the electrokinetic potential of
suspended particles (30).

38477ng
”H

Where: z : Botcntial difference at the interphase
(Zeta potential). . -
n a Coefficient of viscosity of the liquid
phase.
k s Specific conductivity of the liquid.
V . Volume of liquid emitted from capillary.
i c.0urrent in amperes.

t n Dielectric constant.

The following formulae for the electrokinetic
potential on suspended particles by cataphoretic
migration methods have been derived.

After m (31):

5 = 2l__flJtn
H-D

Where: 2 s Electrokinetic potential.

u : Electroendosmotic velocity.

50

perhaps, has developed the most complete and logical
formula for measuring the electrokinetic potential of

suspended particles (30).

a a EIILEJE_E
‘ i 9
Where: z : Botsntial difference at the interphase
(Zeta potential). ' .
n . Coefficient of viscosity of the liquid
phase.
k a Specific conductivity of the liquid.
V s Volume of liquid emitted from capillary.
i :.Gurrent in amperes.

t a Dielectric constant.

The following formulae for the electrokinetic
potential on suspended particles by cataphoretic
migration methods have been derived.

After £12.11 (31):

5 = sliansgn
H-D

Where: 2 e Electrokinetic potential.

u 3 Electroendosmotic velocity.

,

 

 

 

51

n .. Viscosity of. the liquids
H a Potential gradient.
D a Dielectric constant cf liquid.

After W (32):

s g QZILRJE
-k x
‘lhere: s a Electrokinetic potential in volts.
n = Viscosity of medium thru which the
particles move.
u 3 Velocity of particles in cm/sec.

Dielectric constant of medium between

charged layers.
a 3 Applied field (volts/cm) -- Potential
gradient.

§113ggiggrpqu equation (after Northrup):

PD.”
k x-r
'here: 2 D : Electrokinetic potential (in volts).

n Viscosity of liquid : .009.

V

Velocity of particles in cm/sec.

k 3 Dielectric constant of solution a 80.

Potential gradient (drop in esu/cm).

‘All units are electrostatic and must be converted
to practical units by substituting proper values for

the constants:

p p . 12 6 crons er seco d

volts per cm.

0r: 2133mm

volts per cm.

Assumptions:

There is no way of measuring either the density
or the viscosity of the liquid at the interphase,
although there is no evidence to indicate that these
constants are different at that point. It is there-
fore assumed that they are the same as for the bulk
of the liquid and the calculation of the z—potential
iis based on that assumption.

Finally, all the methods require the use of the
dielectric constant of the liquid phase. In most
of the experimental work the value is assumed to

be 80, although it is known that variations in the

33

concentration of salts present or in the intensity
of the electrical field, will cause perceptible

variations from this value.
IBOEHIQAD OOISIDEBATIONS

Now that the chemical and mathematical theories
have been considered, it must be remembered that they
are the result of work carried out in the laboratory.
As is true in all research, the first step is the
collection and development of all the pertinent facts.
It is therefore desirable to review the technical or
laboratory aspects of the work done by various.
investigators in developing the theories and formulae
pertaining to the electrokinetic potential of suspended

particles in water and sewage.

Streaming potential:

212L931 2-9113: Records indicate that the first
attempts to measure the electrokinetic potential on
suspended particles was through the use of a
streaming potential arrangement. In literature
explaining his experiments, Ireundlich, the pioneer
in this work, describes a process whereby liquid

was forced through various lengths, sizes and shapes

of capillary tubes and the resultant e. m. f. was
measured (27). As more knowledge was gained, a
gradual evolution in the types of apparatus took
place until few of the original characteristics of
the early arrangements remain, although the basic
principles upon which they operated have not been
altered.

Of particular interest is a cell developed
by Gee, Harrison and Harrison for the measurement
of the charge on various firbres used in the textile
industry (34). In their apparatus, fibres were
packed into a cell between two platinum electrodes
and the electromotivc force was measured when liquid
was forced through. Due to polarization of electrodes,
they could not use the ordinary potentiometer arrange-
ment, but had to measure the electromotivc force
in a manner which called for no flow of current.

to accomplish this, a condenser was charged
and caused to actuate a ballistic galvonometer.
They determined the specific conductivity by means
of a conductivity cell arranged to utilize the
liquid after it had passed the diaphragm.

U-tube with chamber in the horizontal section
was filled with fibres retained at each end with

55

porous platinum plates (D a D'). Platinum electrodes
(3 a 3') which were formerlyconnectcd with a source

of potential could be brought to a galvanometer.

Sketch of Goo, Harrison and Harrison's
Streaming Potential Cell

 

 

 

 

 

 

 

 

 

 

 

 

u)
liquid was forced from A to.A' through the fibres (I).

 

 

 

Since a Leeds and Northrup (type K) potentiometer
weuld not measure the potential set up across the
diaphragm because of polarization of the electrodes,
a quadrant electrometer was substituted as a voltage
measuring apparatus. Polarisation decreased to a
minimum and the original platinum electrodes were
used by utilisation of the electrometer.

A soil similar to that of Gee, Harrison and

 

 

35

Harrison was developed by Briggs for the determination
,cf the electrokinetic potential on cellulose (33).

His cell consisted of a glass center compartment into
which the diaphragm material is packed, two perforated
gold electrodes and two glass and compartments with
hoary glass flanges fitting against the electrodes,
which serve as supports for a clamp which holds the
whole cell tightly together. In order to make the
cell water tight, thin rubber washers out from

dental dam rubber were passed between the electrodes
and the glass, care being taken not to cover any of
the surface of the electrodes.

The electrodes were disks of 14k gold 1 mm thick
and 45 mm.in diameter. The portion which is exposed
to the center of the compartment was perforated with
1 mm holes as thickly as possible without lowering
its strength. At a point on the circumference of
the disk is soldered a platinum wire which dips into
caps of mercury from which contact is made with the
electrical equipment. Facility with which measurements
could be made was increased by the use of two six-
point double throw switches. To insure perfect
contact in switches, mercury cups and copper rockers

were used with a special switch, the cell could be

 

 

 

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37

connected either to conductivity apparatus or to

a potentiometer arrangement.

Sketch of Briggs'
Streaming Potential Cell

H
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- Gold electrodes.

coconut:

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59

lethod of measurement applied to Briggs cell.
In this particular cell it was necessary to
measure:
(A). The hydrostatic pressure upon the liquid
I as it was forced through the cell diaphragm,
(B). the electromotivc force set up across the
diaphragm,
(O). and the conductivity of the liquid within

the diaphragm.

Hydrostatic pressure: .As a source of pressure,
a tank of about 50 liters capacity was used. Air
was pumped into the tank until the desired pressure
was obtained. This air was then passed through
the diaphragm. Pressure on the surface of the
liquid in the reservoir was measured by a mercury
manometer; then to obtain the pressure on the
diaphragm, the pressure due to the column of water
between the level in the reservoir and the point
of emission from the cell had to be subtracted
from the reading of the manometer.

.A series of stop cooks were used to release the
pressure from the tank and the reservoir, to regulate
the flow through the cell and to provide for the

release of air entrapped in the cell chambers while

 

 

 

   

 

40

they were being filled.

Ior convenience in determining the specific
conductivity of the liquid in the diaphragm, the cell
could be used for either streaming potential or for

conductivity determinations.

Electromctive force: Early in his research,
Briggs found that the ordinary potentiometer could
not be used for measuring the streaming potential
in such a cell as he was using because of polari-
zation of the electrodes while the null point was
being sought. Attempts were made to use liquid
contacts and non-polarizing electrodes (calomel half
cells) with a potentiometer, but the added resistance
of the circuit was so great as to prevent any
deflection of the galvonometer needle or even the
needle of a capillary electrometer, which is more
sensitive than most galvonometers. In order to
overcome this difficulty a condenser and ballistic
galvonometer was substituted in place of the former
measuring devices. This instrument is a capillary
potentiometer and requires almost an infinitesimal

amount of electricity to charge it. Through its

use the polarizing trouble was either reduced to a

41

constant or eliminated entirely.

A switch connected the quadrant galvonameter
either to a strong potentiometer cell or to 3 Leeds &
Northrup Portable Potentiometer, which served as a
calibrating instrument. The deflection an a scale,
caused by light reflected from the mirror attached
to the needle of the quadrant potentiometer, could
be calibrated with the Leeds a Northrup Potentiometer.
The fibre used had a sensitivity of 125 mm per 100
millivalts at a scale distance of one meter,

making it possible to read to l millivalt.

Specific Conductivity: The value of the specific
conductivity is measured by the resistance across the
diaphragm while the liquid, against which the
z-potential is desired, is in the diaphragm pores.
Then after all the streaming potential measurements
'are made upon the sample, the "cell constant" of the
diaphragm is obtained by replacing all the liquid in
the diaphragm with I/lO K01 (or a more concentrated
solution if needed) and measuring the resistance
across it and calculating the cell constant in the
usual manner for any conductivity cell. Then from

the measurements of the resistance obtained while

the experimental liquid was present and the new cell
constant, the Specific conductivity of the liquid ray
be calculated. Care must be taken to use a standard
solution of KCl which is of sufficient strength to
eliminate all surface conductivity effects from the
diaphragm when it is present, in order that the value

of the cell constant will be correct.

Electra-osmosis:

Due to more rapid develOpment of other methods,
electro-osmosis has never been very widely used in
determining s-potentials, but practical applications
have been utilized to a great extent in various
purification and separating processes. Cne of the
numerous cells devised by Hattson, based upon the
principle of electro-osnosis, for purification and
separation of colloidal or insoluble materials has
come into wide use (35). It is employed for the
separation of exchangeable bases in soil suspensions,
for the removal of salts from insoluble materials
such as milk casein, for the preparation of photo-
graphic emulsions, for de-watering of slurry and in
general for the purification.of a wide variety of

materials including organicsq biologicals, alumina

43

and silica.

Mattson has also develOped an improved cylindrical
shell type of apparatus for z-potential measurements
by means of electro-osmosis (38). A specially arranged
optical system is used to measure the velocity of the
liquid flow through the diaphragm and from this
velocity the s-potential may be calculated. Due to
optical considtrations, the apparent or observed

velocity must be corrected by the following formula:
V a c (r2 ‘ 32)
‘2

Where: V 2 Velocity of the liquid.

0
II

A constant determined by the potential

difference at the double layer.

r a Distance from the point of observation
to the axis of the tube.

a a Radius of the tube.

The cell consists of three cells separated by
maubranes through which mobile soluble ions and liquids
may be transferred from the central charge cell to
their respective anode or cathode compartments under

the influence of an applied electromotivc force.

43

and silica.
Mattson has also develoPed an improved cylindrical

shell type of apparatus for z-potential measurements

by means of electro-osmosis (38). A specially arranged
optical system is used to measure the velocity of the
liquid flow through the diaphragm and from this
velocity the z-potential may be calculated. Due to
optical considérations, the apparent or observed

velocity must be corrected by the following formula:
V a c (r3 - 82)
2'

Where: V 2 Velocity of the liquid.
0 s A constant determined by the potential
difference at the double layer.
r a Distance from the point of observation
to the axis of the tube.
a a Radius of the tube.

The cell consists of three cells separated by
mmbranes through which mobile soluble ions and liquids
may be transferred from the central charge cell to
their respective anode or cathode compartments under

the influence of an applied electromotivc force.

The cell sections are composed of three U-shaped live
rubber sections within hard rubber and plates; U-shaped
sections being separated by the insertion of membranes
before tightening the assembly screws.

When the knurled screws are tightened on the end
plate, a liquid tight assembly is formed with three
compartments separated by two membranes. The two
outer compartments are then fitted with anode and
cathode and the center compartment is charged with
material to be purified. Anode and cathode chambers
are fitted with glass tubulatures closed by rubber
tubing and pinch cocks from which the cell contents
nmw'be drained. When the cell is operated
continuously, glass cooling grids are recommended
for immersion in each of the electrode compartments.
Each of the three chambers has a capacity of 250 ml
and the maximum recommended current through the cell
is 200 millamperes, which must be direct current.

In passing it will be remembered that due to
their similarity, any of the streaming potential
cells can be used for electro-osmosis experiments
by simply supplying an electromotivc force at the
electrodes and measuring the volume of liquid

passing through the diaphragm.

45

cataphoresis:

Because of its simplicity and convenience,
cataphoresis is the most widely used method for
z-potential determinations. Based upon the theory
that the velocity of migration is proportional to
the electrokinetic potential existing across the
double layer, the velocity of migration of the
particles through the dispersing medium due to an
imposed electromotivc force gives a measure of the
intensity of the charge on the particles. In
measuring the velocity of these particles, two
methods have been developed, (a) those consisting
of simple measurements of a moving boundry and (b)
those involving the use of the microsc0pe and

special cell arrangements.

Moving boundry method: In determinations
involving the moving boundry method, a U-tube is
cmplbyed with electrodes inserted in the upright
arms and side arms sometimes added for convenience
in filling. The colloidal sol is layered under-
neath a buffer solution of the same pH in such a
way as to leave a distinct boundry between the

two. Upon the application of an electromotivc

46

force, this boundry will migrate toward one of the
electrodes, depending upon the sign of the charge.
By simply measuring the velocity of this movement,
the z-potential on the suspended particles can be

calculated.

Cataphoresis Cell
U-tube Type (1)

 

 

 

 

 

El" LM
war” “is
GD GE
.4. .c.

 

 

 

 

\fij

. Buffer solution.
Colloidal solution.

9 Movable boundry.

bondh-
w

a Side arms with pinch cocks.

i=1
u

Electrodes.‘

47

Although very simple, the U-tube method for the
measurement of the cataphoretic velocities is rather
inaccurate. Indeed, unless special arrangements are
made, this method for measurement is used for little
more than determining the sign of the charge on the
suspended particles, or for very rough velocity
measurements. In a study of the various conditions
affecting the determinations of the cataphoretic
velocity by the U-tube method, Kcmagata proposed
that since diffusion plays an important and practicle
role in the moving boundry method, conditions for
measurement of cataphoretic velocities hy this method
should be more carefully investigated from the
theoretical standpoint (36). He found that except
in cases where the effect of diffusion is too great
to be able to measure the boundry movements, or in
cases of minor diffusion, more limited conditions
should be used to establish the required boundry
in the ascending branch of the tube. .

Numerous special U-tube arrangements have also
been made in order to correct or overcome various
errors and difficulties, Chouckoun, for instance

has provided for the movement of ions and suspended

particles in the colloidal sol, but at the same time

 

 

48

has prevented movement of the liquid, intermingling
of the colloidal and buffer solutions and has
eliminated the effects of polarisation or
electrolysis at the electrodes (37!.

Electrophoresis Arrangement
After Chouckoun

 

 

 

 

 

 
   

’ l’;
/r-—I

 

 

 

: U-tube containing colloidal solution.
3 Buffer solution.
Gelatin plug soaked in H Inl.

a Electrode.

U‘UOWF
II

N’Knl solution.

49

His arrangement consists of a U-tube, containing
the liquid to be studied, which is closed at both
ends with a membrane. The ends of the U-tube dip
into a liquid of the same pH.which is confined by
gelatin plugs soaked in N K01. Ends of these
plugs are bathed in N KCl which also a>vers the
electrodes. H and 0h ions are neutralized by
buffer solutions outside the U-tube, but the
colloidal solution is held motionless within the
U-tube while the boundry moves due to an electro-
motive force applied at the electrodes.

‘In order to overcome the difficulties involved
in accurately determining the velocity of the
movable layer in the U-tube method, Svedberg, Scott
and Arne used a photographic system (59) (40). In
their work with proteins, the position of the double
layer was determined by photographing its
floresoenoe when illuminated with ultra-violet
light. The device was used to measure the mobility
of egg albumin at various aoidities.

The source of light for this work was a quartz
mercury vapor lamp of the vertical type, requiring
220 volts for Operation. It was mounted on a
double walled iron box and was cooled by circulating

water. The light emitted from this lamp passed

 

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50

through a water filter where heat rays were absorbed,
through a chlorine screen.ibioh absorbed the rays of
ultra-violet between 500 and 580 millimiorons, through
a mat screen arrangement which could be used to out

off the light completely if desired, through the
oetaphoresis tube and finally through a bromine filter
which removed the rays between 380 and 530 millimicrcne

before entering the camera.

Sketch of Svedberg's Apparatus.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

F1
‘1 '1
a 0
LJ ...
W C! H 1' Br K

w - Water filter.

01 - Chlorine filter.
M - mat screen.

T - Cataphoresis tube.
Br - Bromine filter.

K " Smart e

 

 

 

 

 

 

 

 

 

51

The photographic equipment consisted of a camera
containing a lens of 205 mm focal length. From various
types of film used, best results were obtained from
Agfs extra rapid, which required an exposure of 90
seconds, or Imperial Eclipse film, which only required
from 15 to 20 seconds exposure.

The buffer mixture in the U-tube consisted of a
mixture of disodium hydrogen phosphate and citric
acid and was used over a pH range from 2.5 to 7.

By this method, Svedberg and his co-workers
found the following mobilities for egg albumin:

pH of 5.75 - 7.9 x.lO‘5 sz Sec‘1 Volt'l (toward the Anode)
pH of 3.4 - 15.5 x 10'5 sz See‘l Volt'l (toward the Anode)
pH of 2.93 - 21.79 x 10"5 0mg .‘iec’l ve1t’1 (toward Cathode)

Microscopic‘method: The numerous problems
involved in making correct z-potential determinations
by use of U-tube methods lead a number of workers in
the development of a more reliable and satisfactory
method. Mattson devised a rapid method for deter-
mining the velocity of individual colloidal particles
by the use of the ultramicroscope (41). Essentially

his arrangement consisted of the cell usually

' ’35.

7’
a7,

‘3‘

s

 

A
.
e
._ .
' _
p
n-
I
I
e
' -
.
.. . ‘ . ‘
-
s
F
‘ s .e
.-
.
.-
g.
u
.
e
l
-
o
' O
.
-
b
c
s
e
.
.o .—

 

 

52

employed with a slit ultramioroscope, except that it
was 22.5 cm long and the ends were enlarged into
chambers for containing electrodes. It was illuminated
the same as for the ultramicroscope. The time required
for a particle to traverse the micrometer eye piece
scale was noted and from these observations the
s-potential could easily be calculated. Observations
could be made in 10 to 20 seconds, whereas the
ordinary U-tube methods required several hours.
A.more simple cell was constructed by Northrup
from ordinary microscopic slides and glass tubing,
which proved very satisfactory and practical (42).
This cell was made of a thin cover slide resting on
strips of glass about 0.8 mm thick, cemented to a
thick glass slide. Two blocks of thick glass were
cemented on top of the cover slide at each end of
the cell for added strength. The ends of the cell
were ground smooth on an emery wheel and a piece of
thick walled glass tubing was widened and flattened
at one end so as to cover the ground ends of the cell.
The ends of these flattened tubes were ground smooth
and cemented to the ends of the cell. The best
cement material for this purpose was the soft grade

of De Ihotinsky cement. The glass was warmed to

53

80° C and a coating of cement was applied. The
surplus was removed with a wire and toluene. After
the Joints were cemented an extra coating was
applied with a small soldering iron for the purpose
of strengthening the cell.

Northrup Cell

fl!

 

\\\\\\\\\\\‘

I
|-| ..

 

---..-.- - --..--C‘

 

54

The cell was clamped under the microscope and
after filling the chamber with a sample solution and
the electrode compartments with saturated zinc sulphate
solution, the electrodes were connected to a source of
potential. The 3-way stop cocks were then turned so
as to close the circuit, and the time required for a
particle to cross a division of the micrometer eye
piece was measured with a stop watch. Owing to the
movement of the liquid itself, it was necessary to
measure the average velocity of the particles in the
cell as a whole. This was done by determining the
velocity at depths of .05 mm increments, plotting
curves from the values thus obtained and determining
the mean height of this curve from the area and length
of the base. It was found that this time consuming
procedure could be eliminated by measuring each 1/8
or 1/16 of the cross-sectional depth and calculating
the mean velocity from this data.

The apparent depth due to diffraction was 5/4 of
the actual depth and knowing this, it was possible to
find any desired depth by adjustment of the microscope
micrometer screw. Due to symmetry it was found that
(only four positions between the center and outside

were necessary to obtain the velocity at l/8 portions

55

of the cell depth. In making these velocity measure-
ments, it was found more convenient and accurate to
reverse the polarity of the electrodes occasionally.

Before the z-potential can be calculated, it is
necessary to know the drop in potential per centimeter
of the cell itself. Since the area of the connecting
tubes is different in general from the cell itself it
is necessary to compensate for this difference. If
the apparatus as a whole is filled with the same
solution, as in the case of Northrup's experiment,
the total resistance of the solution will be
proportional to the length and inversely proportional
to the cross-sectional area. It is known that the
drop in potential per centimeter of the tube is
proportional to the resistance per centimeter, so it
is possible to calculate the drop in potential in
the cell itself providing the dimensions of the
rest of the apparatus are known. In making these cell
calibrations, the total drop in potential was measured
by s voltmeter connected to the zinc electrodes and
the salt solutions were N/lo or less. -

In a similar apparatus,.Kunitz designed a
provision for illumination with a strong beam light
through the front edge of the cell (45).

56

no:

      
   

 

\\
\V

7 M. a

ZiflZfiZgéfifid

 

//////////l

 

 

7 SECTION as

 

 

 

 

 

 

 

 

 

 

The diagram of the cell is lettered alphabeticalr’
to show the order of cementing using De Khotineky cement.
The slide is perforated and made from an ordinary thick
slide which has a circular flat depression in the middle.
This depression is easily cut away with a glass cutter
and one edge ground off leaving a space of 1 mm between
the perforation and the edge.

In determining the drop in potential the following

formula is‘used:

E 15.60 (L0 L1 tn L2 f9 ..... )
l 2 ’

57

Where: Drop in potential per cm of length.

W
I

Total drop in potential.

h»
I

Area of cross-section of cell.

Area of cross-section of other parts.

ht»
H
I I

Length of cell.

I."
I

1 Length of other parts.

Working tagether, Kunitz and Northrup developed
a very simple cell from 1.5 cm test tube (44). The
tube was heated and drawn into a flat capillary, after
which it was straightened and cpened at both ends.
Either zinc sulphate electrodes could be connected
to the ends of this tube or platinum electrodes inserted

directly through its wall.

Cell from Test Tube

 

 

 

 

 

 

 

 

 

L f
i ;
L

 

58

They also develoPed another cell which is suitable
for a wide variety of cataphoretic determinations (45).
This particular cell is manufactured by Eimer and Amend

of New York and may be purchased from them.

V

This cell comes in sections which can be

 

 

 

 

 

assembled by means of ground glass Joints making it
more readily accessable for cleaning and filling
purposes. The electrodes are made of zinc and are
inserted in zinc sulphate vessels, which are Specially
constructed so that they may be filled.without
disturbing the sample liquid in the cataphoresis
chamber.

In order to compensate for movement of the liquid,

Smith and Lissa constructed a Special cell from glass

59

tubing (46). Their cell consisted of two sections
of 1.8 cm bore pyrex tubing 12 cm long, each having
a side tube closed by a stopcock and connected by
means of two capillary quartz tubes inserted in
rubber stoppers, which close the pyrex tubes. Side
tubes are attached to these pyrex tubes to permit
filling without dismantling the apparatus.

The relationships between the bores of the
capillary tubes are chosen so that there is no
liquid flow at the center of the smaller tube, and
theoretical matters are fully considered in the
construction of this tube. Three sides of the
smaller capillary tube are plans ground in order
'to make observations of velocities of microscopic
particles, and also for illumination purposes.
Experimental determinations of the mobility of
quartz particles in this tube and in a one tube
cell indicate that this new cell is superior.

Of particular interest in connection with the
technical considerations of cataphoresis devices,
is the work of Henry and Brittain, in comparing
U-tube with microscopic methods (47). They
gcncluded that one of the greatest advantages of

of the microscopic method, i.e., particles moving

.60

in the same ionic environment, was somewhat offset
by the following disadvantages:

(a). Error in calculating the potential
gradient in the cell.

(b). Unequal distribution of the electric
field near the electrodes.

(c). Polarization and electrolysis

disturbances.

(d). Adherence of particles to cell walls.
PRACTICAL CONSIDERATIONS

In a survey of the literature pertaining to
the prediction and control of optimum conditions
for chemical coagulation, it is essential to review
the practicle aspects as well as the theoretical, in
order to afford a means of correlating the existing
practices and method for control with any that
might be develOped in this work.

Method of plant operation:
Through experience, it has been found that the
most efficient and oonsistant coagulation can be

obtained by a thorough mixing for a period of from

61

10 to 20 seconds. After this mixing, it is the
general practice to allow a period of 15 to 50 minutes
for the floc to form. During this time, the velocity
of the liquid is maintained at approximately one foot
per second for light flocs and .6 foot per second for
heavy flocs.

For improvement upon the nature of the floc,
mechanical floculators are often used. These devices
are designed to prevent the floc from settling until
it is ready for the settling or filtration period.
After the addition of coagulants, the suspension is

often aerated in order to produce a better floc.

Control methods: The evanescent nature of
proper conditions for good coagulation has long been
a problem among water and sewage plant operators.
Without warning, formerly satisfactory coagulation
practices become ineffective and operators are
forced to resort to cut and try methods in attempts
to get back to normal operation. A typical example
is the water treatment plant at Flint, Michigan,
where unsatisfactory coagulation was obtained at
certain seasons regardless of the amount of

coagulants used (48).

62

Many methods have been tried in order to devise
a suitable means of control, but as yet none of them
have been entirely satisfactory. Birsall determined
the proper coagulant dosage by placing samples
containing various concentrations of coagulant into
bottles (49). The concentration indicated by this'
' method was selected as being most efficient for
plant operation. Carbonate hardness, pH and
reduction in turbidity was used as indices of
efficient coagulation by Egger (50).

To facilitate the recognition of floc in the
presence of amorphous material, Hale added sufficient
"Alissnin S" to give a slight color to the liquid
(51). The floc will take up this color from the
_ liquid whereas ordinary amorphous matter will not.

Nasmith has outlined a similar method in which
he assumes the quantity of the floc can be estimated
after it has removed a special color disolved in a
turbid solution.

Baylis found from microscopic studies of floc
formation that upon proper coagulation a "brush
heap" appearance was obtained due to adherence of

the coagulant to the suspended particle (52).

He also devised a special detector for the

fi

63

determination of the amount of sedimentation thrown

by oentrifugation in Goetz tubes (55).

 

. "saves am" APPEARANCE or OOAGULANT
‘ assessor ro sumnnsormicms

my use of three instruments, (a) a submarine
light in the bottom of the clear water reservoir,
(b) a floc detector as described above, and (c)

a specially calibrated turbidimeter, Baylis ...
able to check on the efficiency of both the
coagulant and the filter bed (67).

At practically every chemical coagulation
installation, a great deal of attention is given
to the maintenance of a proper pH. It has been
found that efficient flocculation is very closely
related to certain pH values depending upon the
nature of the material being clarified. ror

64

alum, this pH value has been found to be in the
neighborhood of 6 or 7 and for ferric chloride,

8 or 9. In clarification of colored waters the pH
is often carried to as low as 4.5. Hopkins has
developed a recording potentiometer system which makes
a continuous pH record of the liquid flowing through
the instrument (55). By means of this instrument,

it is possible to carefully regulate the pH of the
vater or sewage being clarified and is very

effective during critical periods when large changes
in pH occur, although the pH is not always a good
indicator in determining best coagulation conditions.

coagulants:

Iron a survey of the literature pertaining to
the coagulants used in clarification of water and
sewage, it has been found that from seventy different
installations throughout the United States, fourteen
were using ferric chloride, eighteen were using
chlorinated copperas, twenty were using alum and
eight were using sodium aluminate. Six plants were
using combinations of alum with other agents,

-chiefly sodium aluminate and four were using com-

binations with ferric chloride. The following

65

coagulants were recommended at other plants: lime
and chlorine (56), aluminum hydroxide (57), ferric

"hydroxide (58), calcium and magnesium hydroxides
(59), titanium sulphate and other titanium
compounds (60), bariom aluminate (61) and a special
sol composed of expanded starch cells (62).

Babbit and Doland list aluminum sulphate, lime,
ferric sulphate, sodium carbonate and sodium
aluminate as the most common chemicals used in
coagulation (65). Arranged according to their
value as coagulants, these authors have compiled

the following list of clarifying agents:

1. 512(304)3 (17 %.A) 9. Ca(3003)2
2. FeSO4-7H20 10. ugco5

3. Ca(OH)2 11. Ca805

4. Ba(0H)2 12. NaCl

5. Ca612 l5. Na2304

6. Hg304 14. NaHCOa

7. Ca304 l5. Hazcoz

e. Mg(3003)2 16. NaOH

hdroxides of Al, Mg, Fe, Th, Zr, Ti and Si
were precipitated from chlorides by the addition

 

 

66

of equivalent amounts of hydroxides and these agents
along with silicates of Ca and Mg were tested for
elficieney in coagulation of sewage by Brintzinger
and Schlegel (64). At 20° 0, various concentrations
ranging from 0 to 6 millimols of hydroxide per

100 cc of sewage were tried and it was found that
only hydroxides of Zr and Ti failed to settle
clearly. The Hg compound settled more rapidly

than Al or 3e and this factor somewhat overcomes
its lower efficiency in precipitation. Reynolds
lists lime, copperal and alum-lime as the most
widely used coagulants which he attributes to

their lower cost and rapid action (11).

Comparison of coagulants: According to their
cost in order from least to greatest, Babbit and

Doland have listed the following agents (65):

(a). Lime and iron.
(b). Alum alone.

(c). Alum and lime.
(d). Alum and soda ash.
(e). Sodium aluminate.

67

They point out that although ferrous sulphate
and chlorine produces a cheaper coagulant and a
heavier floc, still the use of lime is required
which introduces the danger of after-precipitation
between the surplus lime and the bicarbonate
alkalinity. The use of ferrous sulphate is limited
to highly alkalin water because of the undesirable
reaction between FeSO4 and the organic matters.
Insufficient alkali requires the addition of lime
to produce a good floc and also avoid the soluble
iron from remaining in the treated water. It is
also more difficult to use lime and iron than alum
because of the necessity for careful adjustment of
amounts. They point out that sodium aluminate is
often used as a water softening agent as well as
a coagulant. Its non-corrosive and quick
flocculation properties, however, are somewhat
offset by its high cost. Reynolds points out that
oopperas and lime saves in total cast and that the
precipation is more complete, while alum is more
. costly but more easily used in small plants (11).

In a report of the Bureau of Sanitary Engineering,
it was found that FeCl3 was slightly superior to alum
for coagulation, but due to its cost chlorinated

68

copperas was recommended instead (65).

The Russians, Krasikow and Lityago, found that
K11(SO4)3 ' 12320 proved to be a better coagulant
than Fe(804)3(NH4)2SO4 - 12320 (66). While Enslow
holds that chlorinated copperas has proved to be
more effective and cheaper than older coagulants

such as alum or copperas-alum (67).

Results:

In a rather detailed study of chemical pre-
cipitation, Reynolds found that under favorable
conditions the following removals were
accomplished from the addition of .25 to .75
tons of chemical per million gallons of sewage:

Suspended organic solids 80 to 90%,

disolved organic matter 20 to 50%,
total organic matter 50 to 60%,
bacteria 80 to 90%.

Brendlen points out that 60 to 70% of the
bio-chemical oxygen demand and suspended solids
can be economically removed by chemical precipi-

tation processes (68).

69

IIEEBIIENTAL
.HEASUREMENT OI POTENTIAL

The first work to be taken up in the laboratory
after reviewing the literature was that of developing
a practical means of measuring the z-potential of

the suspended particles in water and sewage.

Choice of method:

From the various methods developed for
measuring the intensity of the charge on suspended
particles, an attempt was made to choose a method
which would be practical enough to use in every
day routine work in a water or sewage plant.

A study of the various methods reveals that
streaming potential or electro-osmosis methods
would require more special equipment than ordinary
plants would find available. Furthermore, the
delicate instruments necessary for making the
potential determinations as well as the complicated
arrangement of incidental accessories, limit the
practicality of this method for rapid routine

work. The search was therefore directed toward

70

the more simple cataphoretic methods. It soon
became apparent that the U-tube method would be
unsatisfactory because of diffusion difficulties
and also because of the long time periods necessary
for velocity determinations. However, microscopic
methods did have great apparent possibilities. So
from a summation of experience with a few of the
commonly used measuring devices and descriptions
in literature of others, a cell was finally
fashioned which could be used in microscopic

determinations.

Design of cell:

This cell was designed to take advantage of
the more accurate and rapid qualities of the microscopic
methods, yet its simplicity corrected for the fragile,
costly and other objectionable properties of the cell
usually used in this method. Frequently mentioned in
the literature were problems caused by electrolytic
and polarization disturbances. Also it was found
that many particles adhere to the walls of the
chamber, eventually clouding the surface, rendering
migration incorrect due to the charge built up at

the walls. Proper illumination and readings were

71

also difficult to obtain due to this clouding.

In constructing this cell, two microscope
slides were cemented to stripe of glass such
that a chamber'ZO mm by 8 mm by 75 mm was produced.

After the various parts of the cell had been
cleaned and heated to approximately 90° C, they were
cemented together with De Khotinsky cement, this
cementing process required a great deal of skill
and patience in order to prevent the glass from
breaking, bubbles and leaks from forming, or the
cement from running into the cell chamber. After
the various parts had been fastened together, the
cell was reinforced on the outside with more
cement and any excess cement was removed with
toluene.

It was found that frequent wettings and
dryings caused this cement to deteriorate after
a time, allowing the cell walls to leak. When
this difficulty became too objectionable the
cell was dismanteled and the various parts were
again cleaned and cemented. This second time an
organic plastic disolved in other was used. Upon
drying this latter cement turns to a whitish

color and becomes hard like glass. It was

72

completely waterproof and for this particular
cell was very satisfactory. This cement is made
at Elkhart, Indiana by the Lux-Visel's
Metallic-I Corp. and is called "Metallic Liquid

lender" .

Diagram of the Cell Constructed

 

 

 

 

('1
I ,’
I
EL.

 

 

 

The ends of the cell were left open so that
any bubbles of gas formed at the electrodes could
easily escape, the eledtrodes could be inserted
and adjusted to give any desired potential gradient
and finally, the cell walls could be easily brushed

out and cleaned thoroughly. It was found that
surface tension held the liquid in the cell as long

 

73

 

 

 

unr-

Electrodes and Cell in Place

 

 

3t ing and Z-Potential Measuring Apparatus

 

(tit!

0")

1th E

litafi‘

..I-k)

‘ru\6

ee-w\
11% S

“no

a...

1
.-
‘b

1

I“)

,3‘In.

-,.‘

t...

a.“ |

74

as it was maintained at a reasonably level position.

Microscope:

The cell was small enough to conveniently fit
into slide holders provided on the ordinary
microscope stage. The usual mirror and condensor
functioned very satisfactorily in illuminating
the suspended particles. The particular
microscope used in this work was a Bosch and
Lomb, equipped with an 8 mm objective and a
No. 10 ocular containing a microscale. This
combination of lenses gives a magnification of

250 diameters.

Electrical Apparatus:

At first the source of potential was taken
from a 55 volt D. 0. generator but this voltage
was found to be too high because of the increased
electrolysis and polarization activity and also
because of difficulties in accurately measuring
the higher velocities of the particles. In order
to satisfactorily reduce the potential gradient
without making the distance between electrodes

too great, a special radio dry cell was purchased,

 

‘QI.

ll!-

ll“:
DUI-‘4

. A
a

In
4-

75

from which various voltages up to 225 could be
obtained by connecting to different binding posts.
The current consumption during the velocity
measurements was so small that by alternating
between two such dry cells, the cpen circuit
voltage did not drop appreciable in nearLy two
years of service.

The electrodes were made of chromel wire
and were bent so as to fit into the ends of

the cell. In order to correct as much as possible

Electrodes Inserted Into Cell

 

for drops in potential gradient across the chamber,
the electrodes should be as wide as possible. In
a comparison of the proper width of a cell in
relation to its depth, Dr. Ewing of the Physical
Chemistry Department at Michigan State College,

76

recommends that the chamber be wide in relation to
the distance between electrodes and that the
observationtbe taken at the center in order that
the potential gradient variations between the

electrodes will not introduce any appreciable error.

Samples Used:

Fuller's Earth: In the initial determinations,
it was found necessary to make various adjustments
of the apparatus so that the velocity of the
suspended particles could be determined. For this
purpose artificial suspensions were made by
thoroughly shaking a mixture of 5 grams of Fuller's
Earth and 1 liter of water for a half hour. The
large particles were then allowed to settle for
several days after which the supernatant suspension
was withdrawn and used for calibration and adjust-

ment of the apparatus.

Beet Pulp Waste: At this period of the problem,
a few samples of beet pulp waste were brought to the
laboratory for another experiment, but being highly
turbid, they appeared to be ideally suited for

experimental z-potential measurements, so several

77

tests were run using this suspension. As expected,
the large particles could be very easily followed
during the velocity measurements and these samples
proved to be very useful in devising a means of
eliminating the effect of the liquid movement in
the cell.

Sewage: Although beet pulp waste and Fuller's
Earth were used in the first measurements, the true
object of the problem was to investigate either
turbid water or sewage. Consequently sewage from
the East Lansing disposal plant was selected as
the source of samples for the remainder of this
problem. This city of approximately 10,000,
chiefly a residential and college community,
disposes of its sewage by means of a small
Imhoff plant. The samples of raw sewage were
taken from this plant.

East Lansing sewage is moderately dilute and
since there are no industries, it is largely
domestic. It is rather uniform in composition
except during rainy weather. This uniformity
made it the most satisfactory source of samples

for this experimental work.

78

Experimental Clarification: In the first
coagulation experiments the chemical was added to
100 ml samples and after a thorough mixing was
allowed to settle for five minutes. Directly
after this settling period, z-potential measure-
ments were made. It was later decided that such
small samples would tend to introduce appreciable
error, so 5 liter samples were placed in battery-
jars where the coagulant could be thoroughly
mixed by means of a mechanically driven stirring
device. After a thorough five minute agitation,
the apparatus was set at 20 revolutions per minute,
which gave just enough gentle agitation for proper
flocculation. Samples taken from these larger
volumes gave more oonsistant results than did
the smaller samples.

In measuring the z-potential of suspended
particles, the cell was filled by means of a
pipette with a representative sample of the
suspension under observation, then it was care-
fully inserted into its proper position on the
microscope stage and clamped into position. A
little practice was necessary in placing the

cell into position without spilling some of the

'xz;sf*.-E' . ..

 

 

 

East Lansing

Sewage lreatment Plant

 

’79

80

 

 

“"73
Pump meters and Control Boards
at East Lansing
Sewage rreatment Plant
b
i \
vi

 

 

Imhoff. Tanks at East Lansing
Sewage Treatment Plant

 

 

81

liquid from the open ends of the cell, but after a
few tries and by using a little care, it became a
comparitively easy matter.

Although numerous workers recommended taking
observations at various depths of the chamber and
ccmputing the mean velocity from these observations,
for purposes of uniformity and practicality the
velocity measurement in this work was made upon
particles moving in the center or the cell. This
mean velocity method requires a great deal of time
and since there was no apparent change in the
velocity of the particles, except in the immediate
vicinity of the chamber walls, no appreciable
error in velocity was introduced by using the
velocity at the center of the chamber in computing
the s-pctential. In adjusting the microscope, it
,wae round that when the objective (8 mm) rested
lightly upon the outer wall or the cell, the
center or the chamber was brought into focus.

After the chamber had been filled and clamped
into position and the microscope preperly focused,
the electrodes were inserted into the ends of the
cell and set at such distance from each other as

to give a potential gradient of 3.6 volts per

82

centimeter, since this value proved most satisfactory
for this particular work. For uniformity in adjusting
the potential gradient, care was taken to keep the
electrodes equidistant from the point upon which the
microscOpe was focused.

With the apparatus in readiness, but without
the application of the electromotivc force, it was
found that the particles were set in motion by even
slight disturbances of the liquid and it soon became
apparent that there were a great number of disturb-
ances. Drafts from the laboratory ventilating
system, differences in the level of the ends of
the chamber, building and earth tremors, convection
currents from the heat of the illumination system
and even the breath of the observer while making
his observations introduced error of such
magnitude as to render the observed velocities of
little value.

In an effort to correct for these errors, the
equipment was shielded as much as possible from
drafts and breathe. It was even moved to a more
quiet laboratory and only used during the night
hours, but even so, the combination of disturbances

often caused a greater velocity than that obtained

83

from the application of the electromotivc force.

It soon became evident that such an arrangement
was of no value in z-potential determinations.
Closer observation revealed however, that the velocity
caused by this combination of disturbances always
remained practically constant for 3 or 4 minutes,
and sometimes longer, so that when the electromotivc
force was applied during this time the velocity of
the particles was made up of two componets. The
first, of course, was due to the application of
potential which alone gives a measure of the charge
on the particles. The second component was due to
a drifting movement of the liquid in the cell which
together with the first component gave the particles
under observation an apparent velocity from which
the true velocity, due to the application of potential,
could be obtained. Determination of this true velocity
was accomplished through the use of simultaneous
equations involving two unknowns. Measurement obser—
vations never required more than two or three minutes,
which was usually within the limits during which the
drift component remained constant. If there were any
great variations in velocity, the cell was refilled

and new measurements were made. In order to further

84

nullify the effect of liquid movement in the cell a
large number of readings were taken, averaged, and

from this average, the z-potential was computed.

EVALUATION OI COBSIANTS

The following equation, develOPed by Helmholtz
and modified by Lamb to suit electrocataphoretic

measurements has been used in this problem:

53m
k x

Where: 2 : Electrokinetic‘potential.
n . Viscosity of the solution.
v 2 Velocity of the particles.
k 2 Dielectric constant of the solution.

x a Potential gradient.

Determination of the true velocity was
accomplished by the use of simultaneous equations
' involving two unknowns as follows:
If: v a True velocity of the particles.

y 8 Velocity due to movement of the liquid.

85

Then: v +Iy c Apparent velocity = V

And since: V a 3

 

Where: 8 3 Observed distance traveled by particles.

t 3 Observed time required.
Then: 74y...E_

Simultaneous equations were obtained by reversing
the polarity of the electrodes inserted into the cell
and arbitrarily calling movement toward the positive

electrode positive. When this is done two equations

are derived:

Y+yu+

v-w—s-r

Where: t 3 Observed time of migration.

t' a Time of migration with reversed polarity.

Which may be solved simultaneously for v:

v 3 s (t + t')
2 t t'

 

 

 

Dy substituting this value for v in the Helmholtz-

Lamb equation it becomes:

477 n s (t + t')
kx(2tt’)

Since a great number of measurements were made
it was found convenient to evaluate all the constants
possible. Therefore in the preceding equation the

following substitutions were made:

n 3 OeOOge
s 3 .01275 or .007, depending upon

microscale in the ocular.

x : e in absolute units.
'Tafiflfif'

Where: e Voltage of cell.

d a Distance between the electrodes.

1:880.

And: 2 .-.- 411' x .009 x.01275x300xdxt - t' (Abvolts)
ZKBOIextt'
Since this value for s is in absolute units it

must be multiplied by 300 to be reduced to practical
units.

87

Therefore:

2 ,_. 471')! .009X.0;r275x SOOXEOO xdxt - t' (volts)
2J(802'tt'

By evaluating the constants:

 

 

_ .811122 Xd it + t') *
z “ e " MW “’1”
Or: z 2 .4453218)( d '11 + t') Volts’"
e (tt')

*Ihen one scale division of the ocular : .01275.cm.

*‘When one scale division of the ocular .007 cm.

In the tabulated data it has been found convenient
to let the constants be represented by the symbol K,

in which case:

K's .811122 when 1 scale division of
ocular equals .01275.

K = .445 when 1 scale division of ocular

equals .007.

88

In case of no perceptible movement in one

direction:

K a .2515 when 1 scale division of ocular
equals .01275.

K c.1275 when 1 scale division of ocular
equals .007.

It must be remembered that k is evaluated for
1 scale division, when multiples or fractions of

1 scale division are used, this constant becomes:
Ka<Number of Scale Divisions 3 r

. ._.(-'>m
Then. 3 I tt' (e)

89

RESULTS

The data and results obtained from the

orperimental work of this problem have been placed

into tables to show:

Initial determination of z-potential.
Effect of alum on z-potential.

Effect of ferric chloride on z-potential.
Effect of sodium hydroxide on z-potential.
Effect of sulphuric acid on z-potential.
Effect of time on z-potential.

Values of z-potential for various.

susPensions.

TABEE I

Initial Determination of Z-Potential

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

_ . ,
llSeries 11 a" 4:; =4. (ti—3:15:
1 52.5%” 5.0 55 18.88 18.88 .01155 57.5
2 .. 5.0 55 17.4 15.5 .01284 41.5
5 sgfii' 5.1 51 17.2 17.2 .0115 57.7
4 Ieete 5.85 55 15.5 15.5 .0155 49.5
5 .. 7.7 55 24.5 24.5 .0114 57.0
5 .. 7.5 55 17.7 25.0 .0152 42.8
7 .. 7.2 +55 25.5 25.5 .01024 55.2
8 .. 7.4 55 18.8 25.5 .0125 59.9
9. ‘H_ L. _m* 5.55w55“ 15:4“415.5 .01225 59.8
10 .. 5.0 55 18.1 18.1 .01205 59.2
11 .. 5.95 55 17.2 17.2 .0125 40.8
12 .. 5.55 55 20.5 20.7 .0115 57.4
15 .. 5.55 55 20.7 20.7 .00994 52.2
14 .. 5.85 55 19.5 19.5 .01105 55.8
15 .. 5.10 55 20.5 20.5 .0108 55.1
15 .. 5.25 55 18.8 18.8 .01015 52.9
17 .. 5.25 55 19.5 19.5 .0099 52.1
__18 .. 5.25 55 18.5 18.5 .01025 55.5
__19 .. 5.4 ‘54 19.14 19.4 .01045 55.9
_*§0‘ .. 5.5 p5 19.5 19.7 .01017 55.0

 

 

*1 2 .811122, scale division 2 4.

u}

 

 

TABLE I (Continued)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Series (t-t' d)
Number Sample;pfiw , 9n. t - t' Vt 1,9) 2
21* Sewage 5.4 54 15.5 22.5 .01095 55.5
22 .. 5.5 55 20.3 20.3 .00985 51.9
23 .. 4.6 55 20.2 20.2 .00828 26.9
24 .. 5.5 55 22.5 22.5 .00888 28.8
*k I .811122, scale division 2 4.
TABLE II

Effect of Alum on Z-Pctential

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.51.. Scale no.5: (¥-t';(d)
Number P.P.llfi,Div. pH Read. t t' . e) Z
25** 0.0 4 5.18 40 20.5 20.5 .00975 51.5
* 0.5 4 5.10 40 20.0 20.0 .0100 52.4
1.0 4 5.95 50 19.4 19.4 .0105 55.4
1.5 4 5.84 50 19.2 19.2 .0104 55.5
2.0 4 5.57 50 20.0 20.0 .0100 52.4
2.5 4 5.50 50 20.1 20.1 .00995 52.5
25* 0.0 1 5.18 40 15.58 15.58 .0574 50.5
0.0 1 5.18 50 15.9 14.0 .0409 55.2
‘*r . .011122, 1 a 5.52, e a 22.5 and sample 2 sewage.
‘k . .811122, a s 5.45, e 4 22.5 and sample 4 sewage.

 

 

TABLE II (Continued)

92

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Beriee Scale B0. of (j - ' d)
lumber 2.2.5. Div. pH Read. t t' (vi '31 g====,
25* 2.5 1 5.55 40 15.5 15.5 ..0574 50.5

5.0 1 5.27 40 14.8 14.8 .0585 51.5
7.5 1 5.27 40 15.9 15.9 .0559 29.1
10.0 1 5.45 40 15.7 15.8 .0541 27.7
12.5 1 5.27 40 15.5 15.5 .0547 28.1
15.0 '1 5.27 40 15.4 15.4 .0547 28.1

27* 0.0 1 5.9 40 15.9 15.9 .0412 55.4
2.5 1 5.9 55 14.5 14.5 .0599 52.4
5.0 1 5.9 50 ‘ 14.7 14.8 .0589 51.5
7.5 1 5.9 55 14.5 14.5 .0592 51.8
10.0 1 5.9 55 15.5 15.5 .0555 29.7
12.5 1 5.9 40 15.8 15.9 .0415 55.5
15.0 1 5.9 55 25.8 15.9 .0415 55.5
17.5 1 5.9 55 15.8 15.8 .0414 55.5
20.0 1 7.57 50 15.1 15.0 .0457 55.5
22.5 1 7.57 55 12.5 12.4 .0452 57.5
25.0 1 7.51 55 14.2 14.5 .0401 52.5
27.5 1 7.78 55 14.4 14.5 .0594 51.9
50.0 1 7.57 55 14.0 14.0 .0408 55.1
52.5 1 7.70 55 14.5 15.0 .0587 51.4
55.0 1 8.04 55 14.0 14.0 .0408 55.1
57.5 1 8.21 ‘55 15.5 14.7 .0418 55.9

 

*k s .811122, 4 s 5.45, e 2 22.5 and Sample 4 Sewage.

 

 

 

v .

' e - a . .
- . o e

e g g e
u a q o ,

u I v 0 C e .
. . , Q _ _ . a
7 -
O - - ' O .' e. ' . I
.I
. . . g ' .. a
. s - 1 , r v
.
l - ' C - . . ' .g e
- ,
5‘ . . . a e .. 0
'v
1.

,_ n , 4 9 .9 e

' I ‘ - e

.
g 4 - . .
- e . . ' _ ‘, ,
u
a . . , . .
-. 4 w - . . _ _ .
e t - w -
e
. _ . u . - o
' t e . _ , .
,
- ' e e . .
v
' ‘ e . . . .
' . - — - 4 e V

 

TABLE II (Continued)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Series Scale No.0f (t-t'fifid)
Number P.P.M. Div. pH Read. t t' {ffi‘};§) §===j
27* 40.0 1 8.04 55 15.8 15.9 .0415 I 55.5
42.5 1 7.55 55 14.1 14.2 .0404 3 52.8
45.0 1 7.55 55 14.0 14.0 .0408 ‘ 55.1
47.5 1 7.45 55 14.5 14.5 .0599 I 52.4
50.0 1 7.57 _55 14.5 14.4 .0595 f 52.1
52.5 1 ‘4'7j70 ’ ~55 15.2 15.5 '_ .0575 ' 50.5
55.0 1 7.55 55 15.8 15.8 .0540 i 27.5
57.5 1"_ 7.78 55 15.5 15.7 .0555 T 29.7
F__g——IF*50.0'UL__1 _ ”7.57FF-_55 15.7 15.7““ .0554 7 29.5
, 52.5 A1 7.20 40 15.0 15.0 .0581 i 50.9
55T0“ ‘ ‘1’ '7.95 40 15.4 15.4 .0548 i 28.5
_W_57:5 ‘1 I 7.28 58 15.2 15.5 .0551 4 28.5
28* 0.0 ——i—mfl 5.50 . 12 14.4 14.5 .0595 52.1
-—E5H_Tww1"9 5.40 TW12 15.7 16.8 .0559 25.5
10 1 5.50 12 15.4 15.4 .0570 50.1
15 1 7.11 12 15.5 15.5 .0550 28.4
20 1 7.11 12 15.7 15.7 .0554 29.5
25 1 7.11 12 19.0 19.0 .0501 24.4
50 1 7.05 12 17.5 17.4 .0529 25.7
55 1 7.11 12 19.2 19.2 .0298 24.1
40 1 7.28 12 20.4 20.4 .0280 22.7
45 1 7.28 12 18.7 18.8 .0505 24.7
*K s .811122, 4 = 5.45, e = 22.5 and Sample : Sewage.

 

TABLE II (Continued)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Series Scale (t-t' d)
Number 2.2.14. Div. 35 t t' tt 0) z
20* 50 1 ; 5.45' 20.5 20.5 .0278 22.5
55 1 7.05 20.5} 20.5 .0254 20.5
50 1 . 7.871 21.5 21.5 _ .0255 21.5
55 1 N 7.57 24.4 24.4 .0254 19.1
70 1/2 I 7.51 12.8 12.9 I .0445 18.5
75 1/2 : 7.55 15.4 15.4 .0425 17.8
80 1/2 ? 7.40 15.8 15.8 .0525 15.1
55 1/2 7 7.51 14.7 14.7 .0589 15.5
90 1/2 ' 7.70 14.1 14.1 .0405 15.9
95 1/2* t 7.11 12:5 12.7 . .0448 18.2
100 *1/2‘ 1’7.05 19.5 19.5 I .0292 11.8
105 - 1/2 7.11 21.7 21.8 . .0255 10.7
** 110 1/2 7.00 14.5 i I 14.5-1 7.95
115 1/2 7.11 15.5 9 15.5'1 7.42
120 1/2 7.11 17.4 f 17.4“1 5.55
125 1/2 7.45 19.0 i 19.071 5.10
150 1/2-fidw7.40 21.5 f 21.5-1 5.44
155 1/2 9“ 7.45 25.7 i 25.7-1 4.5
140 1/10 7.05 5.2 y 5.2'1 7.15
* 145 1/10 7.05 4.5' 10.0 .0918 7.45
*k s .811122, a a 5.45, e a 22.5, No. of Readings a 12,

**k a .2315, d a 6.43, e 2 22.5, No. of Readings =
ft' 8 Infinity.

12.

 

 

 

 

b
e t ‘
‘\ .
1’.
e ‘ |
- e
9 .
‘o .L% I
III . .
.4
, e I
.
e. .
7“ g
"" 'eeI
-' er
0
I
. 4 .
, . ”4’. "h”.

..
o
e
-
. e

 

'-

TABLE II (Continued)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Series Scale . (t-t ' 0.;
Number 2.2.11. Div. pH t, f t' t e _8
28* 150 1/10 7.05 8.4 8.0 .0705 5.72
155 1/10 7.05 5.5 2.7 .182 14.8
150 1/10 7.05 4.1 5.5 .157 12.7
b___ 155 94*1}1097.02 45.77 5.5%"49 :i25flhflv 9.97
PW? @7790“ 1710 45795”) 5.7 4.5" ' :12—2 “ w 9.90
__H____ 175 1/10 7.05 4.5 4.7 _ .140 _J 11.4
—_1I_-__9_ 180 .1/10 _7.11 5.2 5.5 ‘4 .125 9.97
190 1/10 5.77 5.8 5.5 .127 10.5
200 1/10 5.77 4.7 5.5 .110 8.94
210 1/10 5.77 7.1 4.0 .112 9.08
220 1/10 6.80 5.9 8.9 .0805 5.55
250 1/10 5.50 5.8 5.5 .0957 7.5
240 1/10 5.95 5.7 8.4 .0852 5.57
250 1/10 7.05 5.1 5.4 .1005 8.15
250 1/10 5.45 5.9 5.5 .1002 8.15
270 1/10 5.55 5.2 5.9 .0944 7.55
280 1/10 5.55 5.5 5.2 .105 8.5
290 1/10 5.52 5.7 '9.5 .0715 5.81
500 1/10 5.52 7.5 8.5 .0715 5.77
510 1/10 5.9 5.9 15.8 .0515 5.00
520 1/10 7.05 y y .0000 0.00

 

 

 

 

 

 

 

 

 

 

*r s .811122, 4 = 5.45, e . 22.5, No. of Readings = 12.

{t a Infinity, t' n Infinity.

95

 

'-
I
.l
I
‘w

TABLI II (Continued)

96

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

__Beries Beale No.0f (t- ' i

umber P.P.M. Div. 453 Read. t t' e z
28* 550 1/10 7.50 12 11.9 15.5 -.041 -5.55'
540 1/10 7.50 I 12 7.1 :17.2 e -.0568 -4.52

550 1/10 7.2 by 12“%_3.9 18.5 -.0555 -4.57

29* 0 1/2 7.51 - 8 9.9 l 8.5 .0555 25.8

_‘10 9‘"i724‘7:456 8 ' ‘8.5 i 9.5 .0551 25.4

_—20m_9—i72_97.45' 8 912.4 i 7.5. .0505 24.5

+__*mr —_25i1/2 7.458 11.1; 7.8 .0520 25.2

27.5 1/2 73§717 8 9.8ifi9.0 .0505 24.5

50 1/2 7.45 8 14.1 7.7 .0574 25.5

_AF 52.5"_ ’1/2 “7.55- ' 8 “4'5.7 "18:1' «T0584 25.7

55 1/2 7 45 1118 7.7 10.1 .0552 25.5

::::f:f“’57.5 ’i72”y7.45gk 8, 9.5_H_9.2 .0508 24.7

_,__i__”. 50 I/IQJ 7.45 a. 81 g72.5 2.8‘ .215 17.5

** 100 1/10 7.11 8 5.5 y 5.5 5.5
##*§91§09j1]10 '9T20CL89' 8.25 -7.7 -.155 -1.55
** It 175 T1/10 5.95 8_*+ 5.8 ;1_ 5.8 -4.00
________ ’ ”GENT/”13 5 ‘93 .15.. “5' f“ 5.. -4.28

* 275 1/10 5.55 ‘8— -4.2 -5.4 -.121 -9.8

P——_‘— _500—9 17104m5.92i 9‘8MH‘Q5:8 -4.5 -.14 -11.5

[::::m_§25 17104 5:84“ I 8 -5.EWI§5.0"‘ 1.155 -11.2

550 1/10 5.55 8~ -5.7 -4.9 -.155 510.9

 

 

 

 

 

*k - .811122, 4 - 5.45, e- 22.5.
**k - .2515, 4 - 5.45, e - 22.5.
fit. . Infinity.

 

 

 

m"

TABLE II (Continued)

 

Series Scale bb. ofE E (t t-t ' e)

 

 

 

 

 

 

 

 

 

 

 

 

 

     

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RRumber 2.2.2. Div. --1P§_ 2444. _Fv_ii-5}__
50* ; 0 1/2 7. 57 E 8 11.1 8.5 . .0592
EEE190 EE 1/10E 7.25 a 5.7 7.5 .114
Efi—99_E EEE159“ } 1910 [7.10 'EE 8 EW5.4E E592EEE_E.128
175 E 1/10 E5.85 EEmEZEEE8949E 5.8 _.0945 E
51* i 0E E 1/2 E9999E E 8 10.5 9.4 .0570
E 50 E_1/2 - 5 .95 E EE8EE10E.8EEEEE8.E8EE .0585
E 100 EEE172E E8297E—" 8 12.2 14.4 .0410
J 150 *EH1710EH9I20EE9E89;:57 5.5 ::.154 E
{.1139 .79: 23321111140634 L
** E 225 g 1/10 5. 95 , 8 17. 4 4 17.4"1
* E 250EE 1710EE5. 45 iEE 8 E18E9El51E1 ”9‘ .00925
** E 275 IE1/10E5. 52 EEE 8 ~5. 9 4 EH— 5.9"1
_i_.___ _ -_1_ 1 --- &7 - _

52* EE 0 1 1/2 l7. 2 1 8 10. 2 5. 8 ’ .0505
99*E9E EE80 E 1/2 E7.11 E 8 §10. 9 8.8EEE, .0582
L—”9E_EEEEF78EEEE1/2E 7957 E 9 8E E14 2 12. 9 E E .0420

100 1715’ 7.59 ‘78 .1? I “azifaa
E129E EE1719EE9.48EE EE8EE5.8 5.9 E .145
_*EWE 150 E 1/10 E7.59 EE8 E 8.2E E8.5 E .098
WE‘VE 175 E1E/E1E0 5.5 8 EEE9E.4 E4 E 9:41:19“—
hfi—E* 200 1/10 8:95 8 10.2 -50.1 .0022

 

 

 

 

 

 

 

 

 

*k = .811122, 4 = 5.45, e 4 22.5.
**k . .2515, 4 e 5.45, e = 22.5.
fit' ’ Infinitye

 

TABLE II (Continued)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

       

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Series Scale (t-t')(d)
Number P.P.M. Div. pH t t' tt 8) Z
52* 250. 1/10E 5.2 5.5 -5.5 0 0
250 1/10E 5.01‘ 5.2E -7.4 .00181 E-o.145
270 1/10 5.55'-12.4E-10.1 E .0785 E-5.57
1155*E' 0 1/2 7.51 8.7E 7.5 E .0915E 29.1
Mfi_h_E— ”50 A 1/2 7.7 * 11.7E 5.7 E .0555“ E27. 0
111 W11: 1.11 1.1: 1.1 .111 T111
150 1/10E 7.28__E5.8E 5.7 1 .141 E10. 4
250 1}199M5H45 8. 2! 11.8 E .0585 E 4.75
275 L1/10:9E.—05~ 4.5E-11.2 E .0454 E 5.51
500 E 1/10E 7. 57 4.5E-9.5 E .0521 E 2.51
525 E 1/10E 5. 95 1;:6E_:5. 29“ .0118 E .95
__92‘_9E_01_E1/2 W 7 .57 E5 .5E 5:51E _99 E55.8
50 E 1/2 1 7.111 4. 8E 8.9 .0889 55.1
100 E'1/2Mf9 .28 8. 5 ”9.1 .0554 25.5
150 91/27 7.11E 5.9Eu1299mE .0552 22.8
____~# 1399 _E‘1{1o 7.20_ 2.7 :595_ .15 -_ 12.2
+___1, ! __250_ 1/10 7.05;_4.52_21:42 1. .0759 5.15
275 1/10 6.80; 5.5 4.1 .0559 2.99
L_! 500 1/10 5.95E 4.5 ~25.5 .0051 4.14
“' 525 1/10 5.59. 5.9 -28.1 .051 4.95
h—hE 550 1/10 5.951 8.1 -18.5 .0194 1.57
b-1~b_Efi.599"_E 1/10 5.50EWT~;"HE ; .0000 0.0

 

 

 

*‘t . .811122, d - 5.45,

i t' . Infinity;

e a 22.5, N0. of Readings a 12.

98

 

I?”

Q

. v 0 O

. I a
. .

. . . u

. u D .

24363 11 (Continued)

99

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8.1-1" ecu. 7N0. 617 (*1'771)
lumber 2.2.11. Div. fipfi 43.06% t t' o) z
36‘ 7 0 1.0 7. 30 . 16 7 13. 27 7.6 .0696 26.6
F 120 7 1/2 7. 30 T 16 ‘ 26. 4 6. 22 '7 .0449 i 20.0
~——n A ~ - 0- . + —7— --—— 7
160 1/2 -7. 30 g 16 L 17.7 11.7 '- .0612 7‘18. .1
-.L__ - - . 1 _ .. -1“- . 7
200 1/2 7.3 7 16 4. 6 -7. 6 7 .0616 7 11.6
___ -_L_ _. - 2 , .7 -. - - . r. 1_- _. __;, 1
36* 0 1.0 7.6 7 20 1 6 2 11.2 7 .0694 7 26.6
—'_ _‘206 71.0 77.6 2467 7.6 6.0 GP .0426 7 19.1
260 1/2 7.6 7 16 5 10.1: 9.1 7. .0292 13. 0
—————- —— - 7 e- 7 7 ~44; iL
. 300 1/2 7.6 7 16 7 13.67 12.7 7 .0217 g 9.66
———m——~—#—— 2-— ~ + ___TH-1_-_L_ 67v4~ — ~a——~—m~ 7
320 1/2 7.6 7 16 I 12.17 12.0 7 .0161 7 6.07
L _,_ ____, —L— _, - ____ '
7 330 1/2 7.6 7 16 13 .67 16.6 .0169 7 7.07
** I 340 1/2 77.6 7 16 710.07 7 10.0'1 ' 6.39
7 ~-— -+. A~~+ -
77 360 1/2 77. 6 7 16 7 16 .77 g 16.7 1 4.06
— ~‘r- - v—7—— — -,_ ,_ 7 r—~#~L ~
* 7 370 7 1/2 77.6 7 16 17. 4 7-17. 4 _7 0.0 0.0
37‘ 7 0 t 1.0 77.16 7 20 11.7 6.7 7 .0671 26.6
0 1.0 17.16 20 9.3 10.6 _7 .0674 26.6
60 1.0 6.7 20 9.6 9.9 .0679 26.3
7———~~—7-- -_, 7 7 ~a «- —~~—9 —9 ~—v
7 100 1.0 6.62 7 20 7 11.3 9.7 .0649 24.6
100 1. 0 6.62_ 20 13.3 9.1 .0629 23.6
r————_”**“—* _ 0.. 11,- __k .1n.__-1_1_
160 1.0 6.1 20 16.6 6.1 .0634 23.6
200 1/2 6. 76 20 13.1 7.2 .0617 13.6

 

*k . .446, a - 6.43, e = 22.6.
**k a .1276, a s 6.43, 0 . 22.6.

{t' u Infinitive.

 

 

v o J 0 J94

. . o u
. . 3 o
.
I O o .
, . ' .
‘ O a . ‘ n
t o c
O ' O .
O I I ’ 1 I
. 7 I ' V
r. O ‘ . o n
. __ .
' I ~ 0
a
-. v p . - . I
I I C o 0
. a O 5 I
o O - O O
n n o t a
. . u 0 '
0 o . C
O O

14515 11 (Continued)

100 '

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

# t - Infinity, t' - Innmty.

 

 

 

 

3011“ ,[ I 80510 No. 01T T [(t-t ' [
lumber 22.2.11. Div. pH .§3§.°.;_t__ _t' , t 3 Z
37** V 250 12575.5—fl 20 5.7 3 » .0250 ; 5.25
'-—‘ -275 1/2 5.92 20 I 12.9 _ i 5 .02154ZL72
[Til __ #300 1/2 1 5.5 20 i 14.7-1 (C, 14.7-ij*-4.35
‘ 320 1/2 5.55 20 '-10.9 5.1 .0205 4.55
——h_‘540 fi—1/2 4 5.5 20 f-12.9 -5 7. 55 #:0155 L 3.47
350 ”1/2 7 5.55% —20 5 fly 7d—~0_M 0
35* 0 1.0 l 7.11 E32 5 10.4 A ~“59'9“.04—‘T05—191—“V2.54
50 51.0 I 5.59 1 32 +$5.5 10.4T .0512 i27.3
_——_~"—a_5100 F 1/2; 5.52 g ”32 7 5.0_' 4.3j’ .113 25.5
::f*.— -150 “1/2 3-5.43 i 32 1 5.2 ‘5.1' .1005 22.5
200 1/2 » 5.15 32 a 5.7 i 5. 5! .0520 15.7
H—“ 250 1/2 ' 5.05 f 32' 11.5 ¥ 5. 7 .0555‘*_i5.0
—~*_** 300 1/2 t 5.03 l 32 1 9.7 ‘3'. 9.7-1 fiw_5.55
.~_5;_h - 325 1/2 4‘5.54 i 32 13. 9 10.1; .045” 5M10.5
::f k 350 1/2 5 5.01 f 32 ,14.2l-17. .9: .0042455 .945
_ _ A 350 11 1/2 E 5.05 I 32“} j y i. '5 0 0 '
_1;;;u,4_ 0 $1.0 .5.55 24 , 5:4“m5 10.3} .0515‘-—27.5~—+
““‘ 7 ’ 50 71.5 75.25 ‘ "a. $11.5 "‘9. 5* 15555337“
;H; ;_T 100 I 1/2 5.15 _24fiL 5.5'_T 5. 2 . .0515 15.2
T” 150 L1/2 5.54 24 5.0 7. 7 .0745 15.5
k - .445, 5 . 5.43, 0 - 22.5.
** k a .1275, d .. 5.43, a . 22.5.

 

 

I"

11513 11 (Continued)

101

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

801-155 $05.15 No. or (t-t ' g (d)
Bumbor P.P.M. Div. pH Bead. t t' tt 5) Z
39* 200 n 1/2 “5.54 24 10.5 "11.2 4.0525311;
250 1/2 5.75 20 16.7 18.0 .0332 7.4
275 1/4 5.67 20 10.1 11.5 .0528 5.9
300 1/4 5.58 20 13.4 24.9 .0328 3.56
325 1/4 5.50 20 y y 0 0

J 1- 151'". . ".4

 

 

 

.* k - .445, 4 - 5.43, e 4 22.5.
f t a Infinity. t' 2 Infinity.

TABLE III

Effect of ferric Chloride 0n Z-Potential

102

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sorioa Scale 13.51 (t-t' 0)
Number 2.2.14. Div. pH Read. ‘5 t' t a) Z
40* 0 1.0 5.52 35 5.9 9.4 .0524 27.5
100 1.0 5.01 24 5.9 9.7 .0514 27.4
200 1/2 5.33 25 5.5 7.5 .0555 19.7
300 1/2 4.74 15 9.5 11.2 .0545 12.2
350 1/2 4.23 L 5 y y 0 0
41* 0 1.0 5.35 i 20 10.4 10.4 .055 24.9
50 1.0 5.35 g 24 12.2 9.0 .0551 24.5
100 1.0 24 12.5 5.7 .0549 24.5
150 1.0 5.92 20 5.9 11.5 .0554 25.1
200 1/2 5.57 15 7.0 5.7 .0535 15.5
250 1/2 5.42 20 10.0 7.5 .0555 14.5
300 1/2 5.05 20 -5.2 3.3 .0517 11.5
350 1/2 4.91 4 5 ¢ 0 0

 

 

 

 

A

 

 

 

 

 

 

* k . .445, d 4 5.43, 5 . 22.5.
f t . Infinity, t' g Infinity.

103

TABLE IV

Enact 01 Sodium Hydroxide 0n 17.-Potential

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Series 30:15 No.01 (t-t' (d)

"“1”” 25341—21131..-£31,393“..._j__11f‘ L 3’ z
‘ 1 /_. 4 .0221
____30 1/2’ . 12 6-2 1.9-1 __-_9?§§_.3_0_-1
h__ 100 1/2 12 ; 5.9 | 9.5 + .0715_ 29.04
___________150 f} 1/2,. 4,. 12‘ 5.5' 8°§_.1_i93§§ 30.1
43* i °.H4_3/2.;~_---.__}?-j9°§._}9'9_1 .0570 23.1
_. 200__{ 1/2 -1 ___4 12 ; 7°62._7‘8.l .074 30.0
400 i_§/22-2 .__‘1 12‘; 5.7*__5.9 ' .0551 25.5
[ 500_'.1/2_~ «#_ 12j_7#1 5.5 .071 29.2
_____ T 500 I 1/2 1 fi—_12 l 5 2 1 7.5 .0534 33.5
44*”: ___0—:; 1/203’__ 125-7:43'13.7fi .0555 23.5
! 50 ' 1/2 T 12 9.5 5.0 .0555 25.5
E _200‘i1/2 _‘h_ri 12_+9.4__5.4 4 .0745 30.3
+4 300 1 1[2_+v_ 12 L_5__.9 9.3" .0720 29.2
45* 0 ‘ 1/2 9.0 12 7.5 5.4 .0520 33.3,
___ +—5o+1/29.5 7‘ ‘12 '5.2'j5.5”4_ .0950 39.5
100* 1/2 10.0 3‘ 123 5.0—3 5.3—3 .0920 37.4
163-- "13139-9 . 113 2715-9 .101. .0...
__+ 299_.L_1/3 10.75 q 12 5.3 y 5.5 + .0970 39.3
_~__‘~__fi“2504 1/2 %10.5fi--12- 5:9L_5.1‘ '09731_139°5
f- 300 1/2 10.9 12 5.2 7.0 .0930 37.5

 

 

 

 

 

 

 

 

* k 4 .511122, 5 = 5.43, o = 22.5.

IABLE IV (Cont inued)

104

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Series 80515 No. 01 (t—t' d)

Number 2.2.3. Div. pH Read. t t' tt e) z
45* 590 1/4111942“ ____.15.1__9_-_z_._ 5:1_-__;,9990 39-7
400 1/2 11.0 12 5.1 5.2 .0940 35.1
450 1/2 11.0 12 5.5 5.1 .0954 39.9
45** 0 1.0 7.5 15 9.9 5.5 .052 27.5
13.33 1.0 5.0 15 5.5 7.5 .070 31.2
33.3 1.0 5.4 15 5.0 5.4 .0554 29.5
47*‘ 0 1.0 7.5 20 7.1 5.9 .0555 39.4
14.2 1.0 7.5 20 9.1 4.5 .0935 41.5
25.4 1.0 5.2 20 9.5 4.7 .0900 40.1
42.5 1.0 5.5 15 5.5 5.5 .0551 37.9
55.5 1.0 5.5 24 5.0 5.2 .0905 40.4
99.4 1.0 9.0 15 5.7 5.1 .0957 43.1
___ 142.5 1.0 9.5 15‘ 5.5 5.0 .0957 43.1
___, 311 1.0 10.0 5 5.4 5.2 .0995 44.4
fi____ 354 '1.0 10.5 5 5.0 5.0 .1141 50.9
~‘____ 751 1.0 11.0 5 5.3 3.5 .129 57.5
1055 1.0 12.0 5 2.5 4.9 .155 74.9
L___, 2050 1.0 12.5 .5 3.5 2.3 .2034 90.7

 

 

 

* k 4 .445, 4 4 5.43, e 4 22.5.

an
k 4 .511122, 4 4 5.43, a 4 22.5.

Luna 3 my; " “’1' 1‘ .1

 

 

105

TABLE V

Direct 01 Sulphuric Acid 0n Z-Potontial

 

 

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106

TABLE VI

Effect of Time In Contact with Alum on Z-Potential.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Series 34514 N» of (t-t' 4)
Number Time D5Y:__,FP31_LE9?d° t t' ( t e _Z
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__ , quijé 5-0’ 8- 2M 5.3-.2 9869 27-4
__”_qw L45"fl__2.5 .3.0 . 5 '27.4 _27.1___.0755 23.4

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r 5' 1.0 r 7.3 12 13.1 11.3 .0474 21.1
:::1_1. 3‘1273531103337.3 "nu—12 '15.7 13.1 .0401 17.9
3—301353473333373“ “12 11.7 11.5 .0495 22.1
30' 1.0 7.3 12 11.5 11.4 .0495 22.2

* k 4 .445, 4 4 5.43, a 4 22.5, 2.2.x. 4 30.

5.43, 0 4 22.5, 2.2.11. 4 50.

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at
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ll

TABLE VII

7514.. of Z-Potential for Various Substances

107

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Z-Potential Method of
Substance Millivolts Determination Investigator Remarks
cellulose 21.4 Streaming Briggs variations
due to com-
16.1 Potential Briggs pactness 01
fibres dur-
8.3 Briggs ing measure-
m_ ._m_._ fig msnt.
Egg Albumin 10.035 Moving Svedberg, variations
due to
17.3 Boundry Arne and change in
‘ pH.
i 27.6 Scott
T n__“w”_ _._____.hni_ .
luller'e Microscopic Dickman Average 01
3 determin~
Barth Cataphoresis ation.
Suspension ” BB .9 g Hi _,-1___
Beet Pulp Microscopic Dickman Average 01
17 determin-
Waete Cataphoresis ations.
Suspension _ _§§:Ei1__. -m..,1
Sewage 27.9 Microscopic Dickman Average 01
41 determin-
cataphorelis ations.

 

 

 

 

 

 

108

15. curves which follow were prepared to show
the relationship existing between some of the factors
influencing the z-potsntial of the suspended particles
in sewage. For instance, the effect of the addition
of aluminum sulphate upon the z-potential 0f the
particles is shown by curves derived from plotting
parts per million of aluminum sulphate against
millivolts 0f l-potential. Similarly the effect of
ferric chloride, acid, alkali, pH and time upon the

charge of the suspended particles is shown.

1. P55 rnewmm.ummn\-fi 4
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EFFECT OF ALUMINUM SULPHATE

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151

EFFECT OF SODIUM HYDROXIDE
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SUSPENDED PARTICLES IN RAW SEWAGE

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146

DISCUSSION

Effect 01 Aluminum Sulphate on Z-Potential:

A study of the curves reveals that from 250
to 560 parts per million of aluminum sulphate are
required to reduce the z-potential to the iso-
electric point. This variation is evidently due
to differences in the composition of the sewage
from time to time as indicated by the comparitively
small amount (150 ppm) required for a very turbid
sample taken during a thunder shower (Series No. 29)
and the similarly low amounts required for other
highly turbid samples (Series No. 51, 32). In this
connection it is probable that colloids of other
than sewage origin are partly responsible for
lowering the z-potential.

For the most part however, the amount of
aluminum sulphate required to reach the iso-
electric point ranged from 525 to 360 parts per
million and the average value for all the
determinations was found to be 520 parts per
million. The addition of more of the coagulant

caused a reversal of the charge which increased

in intensity as greater amounts of coagulant were

‘I'. : .‘ -

Wth iii-{157’

' Tr in").

F

added (Series No. 28 c, 29, 51, 52).

From the curves obtained, it is evident that
the addition of small amounts of aluminum sulphate
cause a slight but definite increase in the
z-potential (Series No. 25, 29, 51, 54, 57, 58).

It was further found that, contrary to theory, at
the point of maximum charge (50 to 50 ppm) optimum
floc formation occured. This tendency was not
discovered at first, but in later work, practically
every curve indicates that such a point does exist.
After passing the point of maximum charge, the
z-potential decreased rather sharply until the iso-
electric point was approached (Series No. 29, 51,
52, 55, 54, 56, 57). During this decrease, the floc
particles became smaller and heavier, but had so
much less tendency to adhere to each other that
often a slight turbidity remained in the supernatant
liquor after the floc had completely settled. This
residual turbidity might have been partially due to
the presence of colloidal aluminum coagulant.

Upon approaching the iso-electric point, additional
aluminum sulphate causes a second marked decrease in
z-potential during which the charge passes through the

iso-electric point and became negative (Series No. 55, 54,

56, 57, 58).

 

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-11 A

148

Effect of Ferric Chloride Upon Z-Potential:

The curves from ferric chloride coagulation data
do not show such a marked maximum point as do the
alum curves; further, the subsequent abrupt decline,
instead of occuring directly after reaching a
maximum, takes place upon approaching the iso-
electric point. In general the ferric chloride
curves were smoother than the alum curves and more
nearly approached in form a parabolic segment.
Although a heavier and bulkier floc was produced
than was obtained with alum, the iso-electric point
was not reached until 550 parts per million of
coagulant had been added to the sample (Series No.
40, 41). Optimum floc formation, like that from
alum, occured between 50 and 50 parts per million
and, like alum, a slight turbidity was evident
at the lac-electric point.

Relation of pH to Z-Potential: .

The pH alone apparently had no direct relation
to z-potential but it does have an indirect relation
in that different salts exist at different pH values.

The presence of combinations of these salts with their

tendencies to peptize or coagulate would have an

bi!

’- lv chill--

...-J

149

appreciable effect on the z-potential. It can be seen
from the curves, however, that although both alum and
ferric chloride have a tendency to lower the pH, there
is no definite rate of decrease (Series No. 25, 29, 51,
34, 37, 58, 39, 40, 41). In fact the pH values seem to
very or fluctuate a great deal as the concentration of
coagulant is increased (Series No. 28 B, 28 C, 52, 55).
These fluctuations may be due to the fact that, as a
rule, sewage is very well buffered and consequently
resists changes in pH. At any rate there is no
evidence of a parallel relationship between pH and

z-potential.

Effect of NaOH on Z-Potential:

The addition of alkalinity in the form of sodium
hydroxide increases the z-potential. Although no
great increase is evident, the sharpest rise occurs
between pH values of 7.0 and 9.5 (Series No. 45, 46,
47). After which the curve rises very gently, at
least up to values of 12.5 and perhaps higher. No

investigation was made beyond this value.

‘Effect of H2304 on Z-Potential;

As could be expected, acidity in the form of
sulphuric acid acts oppositely from sodium
hydroxide in that the acid lowers the z-potential

150

slightly. This decrease is not very marked,
however, and even though the pH was lowered to
less than 5, the z-potential was decreased but

little (Series No. 48, 50).

Effect of Time on Z-Potential:

It was assumed before making any determinations
that since turbid liquids such as sewage would
eventually clarify themselves, the z-potential
must gradualky decrease until, when the sus-
pension became clear, the z-potential becomes
zero. Experiments show that such is not the case,
for when a suSpension containing Just enough alum
for optimum floc formation was measured hourly
for z-potential, it was found that a small
decrease occured during the first few hours, but

from thenon, no appreciable decrease took place.

Relation Between Z-Potential and P.P.M. of

Coagulant:

According to the theory of chemical
coagulation, it should require more coagulant to
reach the iso-electric point in a highly charged

suspension than in one less highly charged.

151

In other words the ratio between parts per million of
coagulant required to reach the iso-eleotric point
and the millivolts of z-potential in the untreated
suspension should be a constant. In the following
table parts per million of coagulant required to
reach the iso-electric point are divided by the

charge on the particles in the untreated suspension.

Relation Between.Amount of Coagulant
And Z-Potential

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

P.P.M.
Coagulant P.P.M. z I

Alum 520 52.1 9.96
.. 150 25.8 6.20*
.. 200 24.0 8.55
.. 290 25.1 8.22
525 27.6 11.81

.. 570 25.6 14.55
.. 560 25.5 14.11
.. 560 26.4 15.71
Ferric Chloride 550 27.8 12.60
.. 550 24.9 14.06

 

 

*Sample very turbid due to thundershower.

152

Prom this table it may be seen that the ratio
varies somewhat, probably due in part to the
variations in the nature of the sample and to

experimental error.

COIOLUSIOBS

At the outset of this work, it was conceived
that, if the point of optimum coagulation was found
to be at the lac-electric point and further, if the
z-potential was found to be a straight line function
of the parts per million of coagulant, it would be
a very simple matter to accurately predict from two
or three points on such a line, exactly what
amount of coagulant would be necessary to reach the
optimum point; Furthermore, if this straight line
should be found to have a constant slope, (1.6. the
parts per million required to reach the iso-electric
point divided by the millivolts of z-potential)
then all that would be necessary to predict the
Optimum coagulating point would be the original
z-potential of the untreated sample.

Prom colloidal theories of chemical coagulation
it is indicated that the optimum condition for

flocculation and clarification is at the iso-electric
point, but from the experimental results obtained in
this work, it is very evident, as shown by the curves,
(that such is not the case. The evidence from this
work does indicate that there is an Optimum point for
coagulation and that it lies very near if not directly
on the point of maximum intensity of the z-potential.
Besides being in direct opposition to the theories
concerning chemical coagulation, such evidence makes
the problem of predicting optimum coagulation
conditions more complex.

Not only was it found that the optimum point and
the iso—electric point do not coincide, but it was
also found that the curve is not a straight line
function and does not have a constant slepe. Thus,
the results have indicated that any prediction, through
the use of the iso-electric point, is impossible. It
has, however, served to reveal the actual mechanics of
coagulation. It becomes apparent that chemical
coagulants serve a dual purpose in the process of
clarification. First the coagulant in contact with
water forms a heavy, bulky, flocculant, highly
adsorptive hydrate. Then, since its charge is

opposite to that on the particles, it serves to draw

..‘culllillllin'l n

K

154

them to it although they do not become completely
neutralized. In this way as the flocculant coagulant
settles, it draws the suspended particles together
and at the same time mechanically sweeps the liquid
clear of them. _
Although the iso-electric point has been found
to be unsatisfactory as a point from which to base
predictions, there is a point that may be the key
to the solution of this problem. This point is the
maximum z-potential reached as coagulant is added
to the suSpensions. In the present work, this
point was not investigated as thoroughly as was
desired because of lack of time. Moreover, it
would be desirable to improve the experimental
apparatus by elimination of the sources of error
so that more accurate z-potential measurements
could be made. With this improvement, the maximum
point could be precisely located and then by
correlation with visual clarification, a method of
predicting the required quantity of coagulant might

be developed.

155

Summarized briefly under the four main objectives

outlined under the scope Of this problem, the following

results were obtained.

I

II

Meagurgment g; Electrokigetic Pgtgntial.
Z-potential of particles in:

luller‘s earth suspension - 58.9 millivolts.
Beet pulp waste suspension - 56.9 millivolts.
Sewage - 27.9 millivolts.

All particles carried negative charges.

Behavig: During Cgagulgtigg.
Aluminum sulphate:

Aluminum sulphate requires 520 parts per
million to reach the iso-electric point, but at
50 to 60 parts per million is a point of
optimum flocculation and maximum z-potential.
Ferric chloride:

Similar to alum, ferric chloride requires
550 parts per million to reach the iso-electric
point. Also the coagulation curve is smoother

and breaks off more sharply at the lac-electric

point.

III

IV

156

0 n O Z-P t
Wilson.

The pH has no direct effect upon the z-pctential.
Sodium hydroxide alkalinity raises the
z-potential; sulphuric acid acidity lowers it.
Upon standing, the a-potential drops slightly
during the first few hours, but does not change
appreciably in the following 24 hours.

MW.

Ho practical application can be visualized from
the present work'except from the determination
of the point of maximum z-potential. This
point probably indicates the optimum.oondition
for coagulation.

(1)

(2)

(5)

(4)

(5)

(6)

BIBLIOGRAPHY

"Outlines of Biochemistry"

Gortner, Ross Aiken - Prof. of Ag. Biochem., U. of
hinn., Chief of Div. of Ag.
at U. of Kinn. and the Minn.

Ag. Bxpt. Sta.

"Colloid Chemistry” - Andresen Ch. V1 p. 471
Prof. Leoner Michaelis - U. of Berlin
how at Aichi hed.

Faculty, Nagoya, Japan

"Theory of Coagulation" - Sew. Wks. J. 7:584-89 (1955)
Emery J. Theriault - Brin. Chem., U. S. Pub.

Health Service

"Coagulation and Color Removal" - Paper presented by

Louis B. Harrison - Supt. of Filt., Bay City, Mich.

"Electrocinetic Phenomina of Colloidal Systems"

from "Outlines of Biochemistry“, Gortner.

"Helmholtz Double Layer Theory" - from
"Outlines of Biochemistry", Gortner.

(7)

(e)

(9)

(10)

(11)

(12)

(15)

"Physical Unreliability of Terms Used in
Cataphoresis and Fictitious Z-Pctential" -
James W. Mb Bain, J. Indian Chem. 800.,
Prafulka Chandra Ray Commentation
vol: p67-72 (1933)

"Water Supply Engineering" - Textbook p.568-71
Babbitt & Poland

"Water Supply Engineering" - Textbook p. 561-4
Babbitt & Deland

"Bible" - 11 Kings 2: 19—22

"History of Chemical Precipitation of Sewage" -
Sew. Wks. Journal 15: see-9 ‘
Leon B. Reynolds - Prof. San. Eng., Stanford
Univ., Palo Alto, Calif.

"Notes on Ferric Chloride Coagulation of Sewage" -
Water Wks. and Sewerage S. 1955
E. F. Eldridge - Eng. Expt. Sta. -
E. Lansing, Mich.

"A Study of Ferric Chloride Treatment of Sewage
at Grand Rapids" - Water Wks. and Sewerage
80: 207-10 (1933)
E. F. Eldridge and N. G. Damoose

(14)

(15)

(16)

(17)

(18)

(19)

(so)

"Textbook of General Microbology" - Chap. XIII
Ward Giltner - Prof. of Bacteriology and

Eygene

"Engineering Bulletin # 9, Rich. Dept. of
Health" - 001. E. D. Rich, Dir. of Eng.,
Mich. Dept. of Health

"Water Bacteriology" - Lecture notes - Course
#301 l. 8.0., Dr. 17. L. Mallman,
Assoc. Prof. Bacty., M. S. C.

"Sewage Clarification of Rivers" - wasser
und Abwasser 27: 510 (1950)
lahr

"Coagulation and Color Removal" - A paper
Louis B. Harrison - Supt. of Filt.,
Bay City , Mich.

"Color in Natural Waters" - J. B. E. W. W. A.
31:79 (1917)
Seville

"clarification of Colored Waters" -
Pub. Health Repts. 40:1472 (1925)
Lo Be Miller - U0 Se Po He Se

(21)

(22)

(25)

(24)

(25)

(26)

"Formation of floc by A12(SO4)5" -
P. H. Repts. 59:1502 (1924) and
40:331 and 147 (1923)
Miller

"Properties and Uses of Colloidal Aluminum
Hydroxide" - Chem. Age 52:51 (1924)
H. M. Spencer - Dir. of Research Lab.,
Saydel Chem. Co.

"A Study of Plocculaticn With Terrie Chloride" -
Thesis for B. 8. Degree from it 8. C.
J. T. Norgaard

"coagulation Process During Purification of
River Water" - Redeel Burgerlijken Ceneeskund
Nederland Indie Pt. 1:27 (1927)
0. P. Mom

"Streaming Potential" - Sitz Preuss, Akad Wise
20:397 (1926)

Rona & Ireundlich

"Streaming Potential" - Kolloid 2 20:81 (1918)
Ireundlich

(27)

(28)

(29)

(50)

(51)

(52)

(55)

"Colloid and Capillary Action" - Kolloid Z (1926)
Preundlich

"Increase in Sensitivity of Photographic
Emulsions by Electrophoresis" -
Compt. Bend 196: 1880-2 (1955)
Andre Charriou

"Electrical De-Watering of Slurry" -
1 Concrete (Mill Sect.)
40 §6:55-7 (1933) #4: 56-9
Hewitt Wilson & H. H. Wilcox

”Development of Electra-osmosis Icrmula" -
Journal of Phys. Chem. 52:641 (1928)

Perrin

"Colloids" - Textbook

Kruyt

"Colloid Chemistry" - Textbook

Thomas

"Determination of Z-Potential on Cellulose" -
J. Phys. Chem. 32: 641 (1928)
David R. Briggs

(34)

(55)

(56)

(37)

(38)

(59)

(40)

"Z-Potential on Fibres" - J. Soc. Dyers and
Colorists 27:278 (1911)

Gee, Harrison and Harrison

"Electro-osmosis Cell" - E. H. Sargent a 60., Cat. 50
‘ Sante lattson - Bureau of Chem., U. 3. Dept. of.Ag.

"Determination of Cataphoretic Velocities by
U-tube Method" - J. Inst. of Elec. Eng., Japan
55: 59 (1955)

Sakuji Komagata I

"Correct Arrangement for Electrcphcresis" -
" Compt. rend 196: 777-80 (1933)

Chcuckoun

"An Improved Cylindrical Cell" - J. Phys. Chem.
‘ 37:223-7 (1933)
Santa Nattson

"A New Method for the Determination of the
Ebtility of Proteins" - J. Am. Chem. Soc.
46:2700-2 (1926)
Svedberg 8 Scott

"New Method for Determination of the mot111ty 01
Proteins" - J. Am. Chem. Soc. 48(2):2272-8 (1926

Svedberg a Arne

(41)

(42)

(43)

(44)

(46)

(46)

"Cataphoresis and Electrical Neutralization
of Colloidal Material" - J. Phys. Chem. 52
of Chem. Abs. 22:4507
Santa Mattson

"A Convenient Cell for Microscopic
Cataphoresis Experiments'I - J. Gen. Physiol.
‘ 4:629-52 (1921-22)
John H. Northrup - Lab. of Rockerfeller Inst.

for ledical Research

”Cell for Measurement of Cataphoresis of

Ultra-Microscopic Particles" - J. Gen. Phys.

6 :415-16 (1925-24)
Kunitz

”Improved Type of Microscopic Cataphoresis
0611' - J. Gen. Phys. 7:729 (1924-25)
Northrup 8: Iunitz _ I

"Catapheresis Apparatus" - Eimer 8: Amend, N. I.
~ Northrup 8c Kunits ‘ .

"A New Cell for Microscopic Observations of
cataphoretic" - J. Phys. Chem. 40:399-412 (1956)
llargaret E. finith and Martin W. Li see I

 

(47)

(4e)

(49)

(50)

(51)

(62)

"Macroscopic Methods for the Determination of
Cataphoretic Velocities" - J. Phys. Chem.
56:602 (1932)
D. 0. Henry and John Brittain

I'Experiences in Application of Alum in
Coagulation" - W. W. Eng. 82:1629-50 (1929)
C. H. Burdick

"Determining Coagulant Dosage by Bottle Tests" -
Lewis I. Birdsall

"Control of Alum Dosage in Water Purification" -
Chem. 2. + c. 50:16? (1926) ,
1- Essor

"Simple Test for Delayethlum Iloc in
iilter Water" - Am. J. P. Health
- Prank E. Hale

"Study of Iloculation Phencmina With the
Hieroscope“ - Eng. News Record 92:768 (1924)
J. R. Baylis - Prin. Sanitary Chemist, City
water Dept., Baltimore, Md.

 

(63)

(64)

(66)

(56)

(57)

(58)

“Measuring the Volume of Coagulated liaterial
Passing lilter Beds“ - w. w. 3 Saw. 78:55-6 (1931)
J. R. Isylis

l'Signficance and Methods for Determination of
Pilter Plant Turbidities" - Hunic laws :- I. I.
76:166-9 (1929)
John R. Bulls

"Coagulation Control with Record Potentiometer" -
' J. A.W. w. 1. 27:91 (1935)
n. 3. Hopkins - Prin. San. Chem.,.lbntebello
Pilters, Bureau of later Sup.,
Baltimore, Md.

'Ooagulat ion with Lime and Chlorine" -
’ J. A. w. v. A. 24:755-6 (1932)
E. I. Ventre *

"Use of Aluminum Hydroxide Solution in Waters hf
Dow Alkalinity" - can. sag. 60:940 (1926)
E. I. Johnson '

"Composition of Perrie Hydroxide as a
coagulant" - Ind. Eng. Chem. 21:268 (1929)
Ed. 8. Hopkins . -

(59)

(60)

(61)

(62)

(63)

(64)

(65)

"Calcium and Magnesium as Coagulating Agents" 4
J. w. w. A. 17:255-60 (1927).
Es Me 316111516

"Purifying Water" - U. S. Pat. 1,175,698 (1917)
- J. W. Bloc "

"Barium Aluminate and Its Use in Water
Purification" - Chimie 2 Industry 22:1067-85
‘ (1929)
R. Stumper I

"3018 for Clarifying Liquids Such As Coal
Wash Waters and Sewage" - U. 3. Pat. 1,942,507
Curtis and Q. M. Campbell

"Coagulants" - Prom.Textbcok "Water Supply
' Engineering", p. 568
Babbitt and Doland '

"Purification of Sewage by Hydrogels" -
' Kolloid z 70:321-3 (1935)
H. Brintzinger andH. Schlegel A

"Report of the Bureau of Sanitary Engineering,
Maryland Dept. of Health" - 19 pp. mimeo (1950)

(66) "The Problem of Purifying Water by Coagulation" -
Zapiski Belorusskoi Gosudarstv
Akad. Selskogokhozyiastva
4:261 (1927)
I. I. Krasikow and A. Lityago

(67) "Chlorinated oopperas and rerrie Chloride
as coagulants" - Manic. News a W. W. 76:227-9
(1929)
L. H. Enslow

(68) "Present Status of Chemicals in Sewage
Treatment" - Sew. Wks. J. 6:920-7 (1934)
J. H.Brendlen .

 

 

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