HHlHHHHlH

I-J—A
1C/DKJCA)

fif' 1
'f; 9
I

THE UTILIZATION OF DISSOLVED
OXYGEN AND NITRATES IN
POLLUTED WATER

_ Thesis for the Degree of B. S.
R. F. Killeen ~
1935

 

 

 

b
a

.1' ll

 

. . . . . 1. .. 11.x 1 1 31.1.. 1.411 .1:
1 . .. 1... .. ., . .... .co- ...1. ,.1 . , 1 . .. .... - . ,1. .. .... . . 1. _ -.. 1
t “1»! . «.V. .11 '4 w. .é1H‘ . ..u wt . .1
. 1 ... .1..- 4.30». . . . . J .1.
. 4.3094193? Fit-l.) . .

u... 14"

u 1!.wvnxnaww..1rr... .
a. . ... .. fl; .. . ..IO.
..l J\ l .

        

   

17”» IO?" "M”
. 1AM? "O ...”.

 

An Exeerimentel Study of the Relation Between
the Time of Utilization of Dissolved Oxygen

anq_Nitretes in Polluted Water

A Thesis Submitted to
The Faculty of
IICHIGAN STATE COLLEGE
OF
AGRICULTURE AND APPLIED SCIENCE

 

Canididate for the Degree cf

Bachelor of Science

June 1935

TABLE OF CONTENTS
Page

Puroose of Project ~ - — - - - - ~ — - ~ - 1
Discussion of the problem - — - - — — - - 1
Excerimentel - - - — - — - ~ ~ - - - - - - 9

Proceedure of tests - — - - - - — — - — - 11

Data - — — - — - - — - - - - - - ~ — - -— 14
Granhs - - - - - - - — - — - - - - - — - 14
Discussion of results - - — - — — — - - - 15

Bibiiogranhy — — — — - ~ — — - - - - - - 16

i 5
Eu
.1 ‘5
is:
I'M
d

'Puroose of Project
The ournose of this exoeriment is to find the relation be-
tween the time of utilization of nitrates and dissolved oxygen
in the decomoosition of polluted water. In the aerobic stabil—
ization of sewage by oxidation;the oxygen sunoly may be obtain—
ed from several sources: (1) The oxygen of the atmosnhere is
absorbed by the water the amount deoending mainly on the temner—
ature. (2) Certain slants will give off oxygen that is dissolved
in the water. (8) The presence of certain salts such as nitrates
in the water will aid in the nrocess of oxidation. The relation
of these oxygen resources concerning the time of utilization is
important in the control of the nolluted stream.
Discussion of the nroblem

Few references concerning this question were found. Fuller,(I)
states; "With respect to gaurdina against objectionable odors, I
think it is clearly necessary for the chemists an bacteriolosists
to keen in mind that putrefaction does not exist so long as oxy—
gen remains at all. In fact you can go further than that, and
say that so long as oxygen is available from nitrates, nitrites
or other oxidized salts there is substantially no nutrefaction."

It will be noted that nothing is said about which is used
first the dissolved oxygen of the oxidized salts. However it is
made clear that nutrefaction does not begin until both the dies—
olved oxygen content and the nitrates have been used by the sew-
age. The word "substantially" infers that there is little if any
outrefaction at the denletion of the oxygen sunnly. This there—

fore does not set any limit as to the beginning of outrefaction.

(2)

From data given by Fuller(lI), it was shown that there were

nitrates present in sewage samples where dissolved oxygen has
not
been deoleted. It canAbe determined from this data, however,
just when the nitrate and nitrite content are reduced. That is,
it may have started at depletion of the dissolved oxygen or per—
haps it may have depleted at the same time the dissolved oxygen
was reduced.
(III

The information given by H. Heukelekianxdoes not settle the
question as to the time relation of the utilization of nitrates
and dissolved oxygen and nitrites. He states: " The nitrates and
nitrites were added as a potential source of oxygen and compared
with actual amounts of dissolved oxygen. The nitrates and nitritee
increased as the oxygen saturation was eighty percent or more.
It would appear that pollution up to this point was not suff‘
icient to have a detrimental effect on nitrification. When the
average dissolved oxygen content drooped to sixty percent satur—
ation there was a loss of nitrates. Probably not only was nitri—
fication retarded but an actual loss of nitrates due to reduction
might have taken place. Althoush it has been shown that the nitr—
ates are not utilized until practically all the dissolved oxygen
is consumed, it is possible, as indicated in the above discussion
that localized anaerobic zones might be established in a medium
which is not entirely defecient in dissolved oxygen."

This information is rather indefinite as to just when the
nitrates are reduced. The author explains the discrepancy between

the data concerning the loss of nitrates and the accepted fact

that the nitrates are not utilized until the dissolved oxygen is

depleted, by a theory that "localized anaerobic" conditions
exist in which nitrates are reduced but no dissolved oxysen is
utilized. It is possible however that the actual loss of nit~
rates might have commenced anywhere below the sixty percent sat~
uration point, had there been no " anaerobic zones ".

It has been pointed out in the above discussion: (1) That put-
refaction cannot exist until the dissolved oxygen and the nit—
rates have been reduced. (2) That nitrates are present after the
dissolved oxygen has been exhausted. (3) There is evidence that
below a sixty percent dissolved oxygen saturation point nitrates
are reduced although it is commonly accepted that reduction does
not begin until the dissolved oxygen is depleted.

Any conclusion as to the cuestion under discussion would have
to be indefinite if based upon the above references. Although the
statements may be regarded as true they do not cover the same
scope as would be desired. The statement made by Heukelekian that
the nitrates are slowly used, reduction starting when the dies—
olved oxygen is less than sixty percent saturation is contrary
to the other data found which seems to show that the nitrates were
not used until possibly all the dissolved oxygen is depleted.

It seems cuite possible, however, that “anaerobic zones " might
have been established around some of the larger particles, or in
certain areas where contamination was especially heavy. That is,
nitrates might have been used in these zones while there was dis-
solved oxygen'present in the water as stated by Heukelekian above.

There are several practical points that hinge on the question

under discussion- the relative time of the utilization of dissolved

oxygen and nitrates also the onset of septic or anaerobic cond-

(4)

itions. (Hydrogen sulnhide gas is commonly used as an index of
sentic conditions.) I
Probably the most likely noint in this connection is the devel—
cpment of anaerobic conditions in a nolluted stream. The stream
Drovides a natural means of disnosing of sewage and industri al
wastes by dilution, allowing the wastes to decomnose with the aid
of oxygen then to become inert. At times, esoecially during low
flow oeriods of the stream, sentic conditions will occur causing
an odor nuisance as well as becoming unsightly. Often the stream
is used in many ways, both oublicly and commercially and thereby
affected seriously with the develonment of sentic conditions.
Some of the considerations that must be keot in mind in the reg-
ulation of a Dolluted stream as given by Metcalf and Eddy (IV):
A. Hygienic considerations.
1. Contamination of
a. Private and nublic water sunnly.
b. Natural ice.
c. Shell fish.
d. Water and bathing beaches.
2. Pollution resulting in
a. Nuisance affecting public health and comfort.
b. Imoairment of recreational facilities.
B. Esthetic considerations, creation of conditions offensive to
l. The eye.
2. The sense of smell.
C. Economic considerations, damage to

1. Industrial water sunnlys.

2. Live stock.

(23

. Fish and other useful aquatic life.

Property,with resulting depreciation of values.

0'1 r?»
0

Private and public river and harbor improvements and
navigation. ( such as silting due to sewage deposits)
D. Legal considerations, interference with

1. Riparian owners.

In the development of septic conditions , the last three con—
siderations (B,C,D) are all affected to some degree. It can be
seen from this outline that the prevention of septic conditions
is important to a variety of considerations. Therefore in streams
where this consideration must be met it is important to prevent
these anaerobic conditions from forming if possible.

A second point to be considered in the allowable pollution
of a stream is the maintainance of fish life. The degree of pol~
lution necessary to keep a stream fit for fish life may not nec—
essarily be the same as that necessary to develop anaerobic con-
ditions as mentioned above. That is, the condition of pollution
of a stream is important concerning the fish life, as well as the
prevention of septic conditions and the consequences that follow.
Rudolfs, Heukelekian,Lackey, Zeller and Lacyvfrom studies on the
Raritan river report as follows concerning fish life:"As long as
pollution only is limited, that is, when the dissolved oxygen con—
tent of the river does not fall below sixty percent saturatwon at
any time of the year, conditions are favorable for fish life, pro—
vided sludge deposits in the river or alone the banks are of slight
extent.

When the disrolved oxygen in the stream has reached about fifty

percent saturation and sludge deposits are being formed below

(6)

sewer outfalls and on shallow places, fish life will still exist
to a more or less limited extent, althoush they will not multiply
except in rather limited places. The more susceptible fish migr-
ate.

If the dissolved oxygen content in the river during any time of
the year falls below thirty percent saturation and sludge deposits
become more or less permanent durins the summer or at lower water
flow so that local nuisance might be expected on account of odor,
still a few fish like eels, which are able to exist on little
oxygen would be present but all other types would disappear."

From this discussion it seems that the welfare of the fish
depend on the dissolved oxygen content of the stream as well as
the surrounding conditions of the stream bed. The limit thirty
percent dissolved oxygen saturation as the limit of pollution
that fish will endure appears to be senerally accepted. It is
important, then, that if the stream is to protect fish liIe this
limit of pollution be observed.

Two of the important problems in stream control, as pointed out
above, are the prevention of septic conditions and the maintainance
of fish life by keeping the minimum requirements of dissolved ox—
ygen present at all times. The question of meeting th as require-
ments bears directly on the relation of the time of utilization of
nitrates and dissolved oxygen.

This relation is of importance caperning septic conditions as

the time of utilization of the oxysen resources may help in pre~

venting these conditions from developing. That is if the nitrates

and dissolved OXygen are used prior to septic conditions then they

(7)

will aid in the prevention of septic conditions and in some
cases would no dOubt actually prevent these conditions if present
in large enough amounts. As stated by Fuller above, this is what
likely happens. However, it is not stated definitely that some of
these resources might not remain after septic conditions commence
nor is there any reference as to which potential oxygen supply is
first utilized, this point however is not important in this con—
nection. It is evident that in this first' case the full oxya—
en supply would not be available to prevent anaerobic conditions.
The time of utilization of oxygen resources, however, is import—
concerning the question of fish life. That is,it is desirable
to maintain a certain definite limit of dissolved oxygen but as
the relative time of utilization of the nitrates is unknown, it
is not known whether their presence will aid the fish by giving
up its oxygen to the dissolved oxygen present or not. Conditions
would be favorable to fish life if the nitrates were reduced
wholly or partially before the dissolved oxygen was used up.
Another reason for the importance of thee relation is as an
indicator of pollution. It is common to use either the dissol—
ved oxygen content or th. nitrate content as an index of poll-
ution without restrd to the condition being investigated. How—
ever if these two oxygen supplies are not utilized at the same
time in the decomposition of sewage then each will be an indie—
ator of a different stage of pollution. For example, if the dis~
solved oxygen is used up completely prior to the use of nitrates
after which septic condi+ions follow, then the dissolved oxygen

content would be a better index of pollution during the early

(a)

stage, the nitrates during the latter stage of decomposition.
If, however, the order of utilization is reversed, the cocoa-
ite would be true concerning the proper index of pollution.
Also, if the two oxygen supplies are used together then either
one would be an index of the conditions being studied. If sep—
tic conditions ocour before the entire utilization of nitrates,
the oxygen control would be the best indicator as to when an-
aerobic conditions might be expected. If nitrates are used
after the dissolved oxyqen, the nitrate index would be incorr-
ect, however it is not usually used.

It is the purpose of the séwage disposal plant to prevent
these conditions, as well as other considerations mentioned
in the outline given above. That is, to prevent the develon—
ment of septic conditions and to protect the fish life. Of
course the sewage plant is not entirely responsible for the
prevention of the undesirable conditions. Other factors that
also govern the stream conditions are: (l) The volume of flow.
(2) The amount of aeration due to rapids, dams etc. (3) The
presence of certain green plants that supply oxygen. (4) The
surface area available for oxygen absorption the amount de—
pendinr upon the temperature and the dissolved oxygen already
present. In many streams these factors aiding purefication.are
enough to handle comparitively heavy loads with no undesirable
conditions resulting. However the anoint of purification accom-

plished by the sewage plant is often the element that controls

d'

the condition of the r

5D

am. It seems then, that the degree of

0)

the purification of the sewage plant effluent is an important

factor in the control of the sanitary conditions that are foumj

(9)

in the water way. Some of the important tests of sewage effluent
which indicate river conditions are: The reduction of solids,
the reduction of bacteriological oxygen demand, the reduction

in bacteria count and the increase of oxidized salt content as
well as the development of a dissolved oxygen in some cases. The
first three tests indicate .he plant effeciency conce rning the
pollution to be added to the water while the latter potential
oxygen resources indicate the amount of pollution that may be
expected to be combatted. It is through the utilization of these
last named tests that the experiment is involved. Included in
the group of oxidized salts are the nitrites and nitrates which

.3 respect. The control of these

DJ
H.

are the most important in t
conditions from the sewage plant depend somewhat on the relation
of the time of utilization of the oxygen resources.

The question to be answered,from a practical standpoint, is
whether or not the high nitrate content produced from certain
types of sewage plants is aiding in the prevention of the un—
desirable septic conditions anl if so to what degree. From the
material covered by the investigations given above, the answer
would seem to be that the nitrate content in polluted water
tends to retard septic conditions but does not help in maintain—
ing a high dissolved oxygen content, thus the fish life is not
aided by this potential oxygen supply. However, as pointed out
before these references do not answer the question satisfactor-

must'be
ily and the missing dataAsupplied experimental y.
Experimental
The sewage samples used were taken from the East Lansing

sewage plant effluent channel. This sewzge recieves only pri-

\‘."I

mary settling in Imhoff tanks.

The plan was to simulate polluted stream conditions where
both nitrates and dissolved oxygen are present. The sewage sam—
ples used contained no nitrates and little dissolved oxygen and
is generally considered weak in bacteriolosical oxygen demand.
The nitrates were added to the samples in the form of potassium
nitrate, the same amount being added to each. Various dilutions
of the original sample were made with dilutina water which had
been stabilized and thus contained a fixed amount of dissolved
oxygen. A wide range of dilutions was now available through
which the nitrate content was constant but the amount of poll—
ution was directly proportional to the dilution and the dissol—
ved oxygen was inversely proportional to the dilution. Each dil—
ution was tested immediately for dissolved oxygen content and also
the nitrate content was checked to see if the dilutions contained
the cemented amounts. Three other samples were drawn from each dil—
ution and were incubated for a period depending on the strength
of the sewage. The incubations were side in.closed bottles at
room temperature and tested after the period d’inoubation—
usually less than five days— for the same substances including
the test for hydrogen sulphide. It was desired that the oxygen
resource that was first depleted would occur in about the middle
dilution— in order of strength— so that the relation with the
other oxygen supply could best be observed. To do this it was
necessary to make a trial test to determine what range of dil-
utions would best fit this condition. An arbitrary scale of dil—

utions was chosen for the first trial and the experiment finish-

\ill

ed. It was found that the dilutions were too low for the stren—
gth of sewage that was used, that is, only a small amount of
dissolved oxvgen we used uo throughout the entire range of dil—
utions while none of the nitrates were used. A second trial was
run this time using a higher range of dilutions. However there
mist have been a variation in the strength of the sewage as the
range was asain too low . On the next trial , however, the dies-
olved oxvgen was utilized in all but the weaker dilutions and
the nitrates were used after the deoletion of the oxvsen. Al-
though no hydrogen sulohidd test was run the characteristic odor
indicatinv its presence was found in those dilutions in which
the nitrates had been utilized. Almost the same range of dil—
utions was run on the last test and the results were similar to
the previous test and in addition a hydrogen sulohide test was
made. The Droceedure of Theroux and Eldridse (V1) was followed
in making uo the solutions and performing the tests that were
made on each dilution. These were as follows:
(1) Dissolved oxygen (Winkler Method)
1. Add one c.c. of manganous sulnhate solution hv means of a
nipet+e.
2. Add one c.c. of alkaline potassium iodide solution.
3. Insert the stooner and mix by inverting the bottle several
times.
4. Allow the orecioitate to settle half way and mix a second
time.
5. Again allow to settle half way.
8. Add one 0.0. of concentrated sulphuric acid, insert the

stonoer and mix immediately. Do not allow the hot+le to

stand

8.

Note: This

(I?)

onen after the addition of the acid.
Allow the mixture to stand at least five minutes.
Ranidly withdraw one hundred c.c. of the samnle into a
flask and tiarate with twentv-five thousandths normal sod—
ium thiosulohate using starch as an indicator near the end
of the titratbon.

t

-itration should not require over two minutes after

the samnle has been removed from the bottle. Should the blue

color of the starch iodide return after once beina decolor—

108d, it should be disregarded.

Calculations:

c.c. thiosulohate x 8 equals p.p.m. dissolved oxygen.

(2) hitrate fiitrozen ( ohenoldisulnhonic Acid lethod)

1.

03

Filter about thirty or thirty—five c.c. of the sewage through~
a filter oaner.

Evanorate twentv-five c.c. of the filtrate to dryness on a
water bath. ( Use a smaller amount if the nitrate content

is high.)

Hoisten the residue with one c.c. of nhenoldisulohonic acid.
Dilute to about twenty c.c. with distilled water.

Add a fiftv oercent solution of sodium hvdroxide until the
maximum color is oroduced. ( Not over five or six c.c. will
be required.)

Filter into a Nessler tube and wash the never with water

m kins un fi“.lly to fiftv c.c.

make un color standrrds containing thfee tenths, five tenths,
seven tenths, one, one and one half and two c.c. of the

standard nitrate solution and add two cc. of ftfty nercent

sodium hydroxide to each.

8. Dilute each to fifty c.c. and select the standard comoarins
with the samole.
Calculations:

c.c. standard x 10 equals p.n.m. nitrate nitrogen.

 

c.c. sannle used
(Authors iote. A color disc was used in the exoeriment in

class of makinv no color standards as directed in steo seven.)

(3) Hydrogen sulohide.

1.

Syphon five hundred c.c. of the samnle into a graduated

cylinder.

r‘b

Pioette ten c.c. o the twenty—five thousandths normal iodine

solution into each of two erlenmeyer flasks.

3. Add one gram of notassium iodide to each flask.

4. To one add two hundred c.c. of distilled water.

5. To the other,syohon from the graduate two hundred c.c. of the
sanole.

5. Titrate both the distilled water blank and the samole with
twenty five thousandths normal sodium thiosulohate, using
starch as an indicator near the end of the titration.

Calculations:

c.c. iodine used for samole - c.c. deed for blank x .3409
equals U.D.m. of hydrosen sulohide.

Note : This method is for both free and combined hydrogen
sulohide.

( Authors note. Inasmuch as the samole used was only two hun‘
dred c.c. the calculation factor was changed when computins

the hydrogen sulnhide content.)

4
l

A...‘
’6;

'3
y , I 1-
. : ._

:VE

&

.74

A

!

t

MEN/1mm
- :
01?)?

1

l
'?
-.i
‘E

INCH

,4»
l
,._ Ax
H4
“——
l

A.

0N

+

B

i ‘
1mm

1

1

$750

_ !

l

i ; x h .

391:0
:QILUT/

     

I
l
.74.

- +
71 7. q

I

1 I. loll-Ill:
, _
4. p .
A L . e .I l
s N a
_
v
p i
.
I .L I . J r

_a_ an ,7 .

__.._.

l

I ... I .lji.t

t

ms:- gm 0mm

\
o

A

1

II

t

 

l

a 5n

4,»

i

t

V

45»
Ni 7/94 TEJ 5,5me

M a
1m.

,,

a *7, .

I!

AFTER

1

 

i. __,, h.
A

ll

!
“ E

II

II

I

 

 

 

 

 

 

. .nfl..alulb|...|.t 4-.. l...
.

 

 

 

WT?

WSU?
ENT:07LUiT/ONE

.1
..1!

 

,.

 

 

 

.IIII'IililT Till I o

’I
I
I
l

 

. , .
f . ... .
-Il‘! 1

 

VVV- ..-

 

u‘ A
. .
u
.
. .. .
a \ \—
_ a .
.
.l
. \ \4
K
C u
h ‘I
. .
. ~ / .
. u .
\
- _ s...
.
t f
. t. A
.
. A .
_§
.-
.
\ o .
. _
\ .
~ I \
. .
.
i _
_
. x
. A
...
.
. .
. y y .
.
\. §
. I \ .
.
. r
II \,
s O
. r.
I \
. \\
. x
. .-
i . ‘
.
. . r. .i . .
h
a _
ol
\
. .
h .
.
.‘V I .
. ~
.1 . ,
u.
A .
g. .
it ‘
. I (i g ,
A
.
_ .
.

Oflyl

x.‘ .r o :l.....,. II., I '

..-, _- m
,

l

\

 

- us.
i

,4

V

r

--

(14)

Data

Trial #1
sample 1 2 3 4
% dilution ;1 '5 410 15
N03 added 5.3 5.3 5,3 5.3

D.O. 8.7 8.5 8.4 8.2

Readings after incubation for two days.‘

no. 5.3 5.3 5.3 5.3

D.O. 7.7 7.5 6.7 5.9
Trial #2

samole 1 2 3 4

% dilution 1 5 10 15

N03 added 5.3 5.3 5.3 5.3

D.O. 8.6 8.6 8.2 8.2

Headings after five days of incubation.

N03 5.3 5.3 5.3 5.3

D.0. 6.7 6.6 4.0 8.3
Trial #3

sample 1 2 3 4

% dilution 10 l5 20 85

N03 added 4.4 4.4 4.4 4.4

D.0. 8.5 7.6 7.4 6.9

Reading after five days of incubation.
N03 4.4 3.5 8.6 0.0
D.0. .4 0.0 0.0 0.0
Hts (Odor detected) x

()1

x]
o
O) ()1

(II

Cr!

.01
,p.

20
5,3

7.8

4.4
6.4

0.0
0.0

U1
0
‘34

‘Q
o
(D

0.0
0.0

(’3
(I1 \1

(11
0

J
O 03

2.6

0.0

(15)

Trial # 4
sample 1 2 3 4 5 s 7
% dilution 1 2 5 10 so 30 50
N03 added 4.4 4.4 4.4 4.4 4.4 4.4 4.4
0.0. 8.4 8.3 7.7 7.4 6.4 5.2 2.8

Reading after four days of incubation.

30. 4.4 '4.4 0.5 0.1 0.0 0.0 0.0
0.0. 3.8 3.4 0.0 0.0 0.0 0.0 0.0
H38 0.0 0.0 0.0 .8 .5 .8 1.3

Note all readings of D.O., No.4 st are in o.n.m.
See graphs for results of trials no. 3 & 4.
Discussion of results
The data may be interpreted from the experimental data with
the aid of the graphs as follows:
(1) All the dissolved oxygen was utilized before any reduction
to the nitrates took place.
(2) Immediately after all the dissolved oxygen was used the
nitrates were reduced.
(3) Inmedietely after all of the nitrates were utilized, septic
conditions followed.
Inasmuch as all nitrates Dresent in the sewage were in sol—
ution and not contained in suspended or settled solids there
was no oossibility for "localized anaerobic zones" to develon.
This,therefore would not lead to false conclusions of sunoos—
ing that the nitrates were utilized before any oxygen was used,
as observed by Heukelekian, mentioned above. Also this nroves
that his as umotion was correct concerning the fact that

nitrates were not used orior to the use of dissolved oxygen

(16)

as his data seemed to indicate.

Another point brought out by the exnerimental data, is that
nitrates and dissolved oxygen must be utilized comnletely be—
fore the undesirable sentic conditions will result. As-a prac—
tical noint this shows that all of the nitrates nresent in the
effluent of a sewage slant will be utilized prior to the devel—
ooment of these conditions.

However, as it was nointed out in the data the nitrates are
used after the dissolved oxygen is deoleted and thus are unable
to give uo there ootential oxygen until after the criticai dis.—
olved oxygen saturation noint of about thirty Dercent has been
reached, thus not aiding fish life.

The nractice of using the dissolved oxygen content as an in-
dex of pollution is sound but it would not be exactly nroner to
use this test as an index of when septic conditions might be ex-
pected, but the nitrate test would show the true conditions. In
general, the nractical results might be summarized by stating
that the nresence of nitrates in a polluted stream will give no
its oxygen sunnly to aid the prevention of anaerobic conditions
but would not be available to aid in the protection of fish life.

Bibliograohy
(I) "Sewage Disnosal by Dilution", by Fuller ( a quotation ),
"Seweraee and Sewage Disoosal", by Metcalf and Eddy;2 ; 416; 1930
(II)”Chanaes occurring in fresh Lawerence sewage upon standing
in a bottle in laboratory", by Fuller, "Sewage Disoosal";a.text~
book; 67; 1912.

(III) "Some Biochemical Relationships in a Polluted Stream", by

(l7)

Heukelekian, " Treasury Denartment U.S.P.H.S."; 44,9«10~ll,
June as, 1929.

(Iv) "Sewage Disoosal by Dilution", Metcalf and Eddy, "Sewer—
age and Sewage Disnosal", 2; 389; 1930.

(V) "Study on Raritan River Pollution", William Rudolfs, H.
Heukelekian, J.B. Lackey, P.J.A. Zeller, 1.0. Lacy; 31; 1927-
1928.
(VI) "Recommended Laboratory Methods of Analysis for Michigan
Sewage Treatment Plants", E.F. Eldridge, F.R. Theroux, W.L.

Hallmann; Bulletin No. 49; January, 1933.

.v.‘l

~\l.

-1". I.

 

.5“ _ . n I . . _
. . . o .
.IIOI (It; rib 1'- .v.

 

CAN STATE UNIVERSITY LIBIRARJ E5

H J JJ JJJ'JJ JIH I

02306