A COMPARISON OF 20 deg. C. BIOCHEMICAL OXYGEN DEMAND AND 37 deg C. BIOCHEMICAL ‘ OXYGEN DEMAND Thesis fOr the Dcérée of B. 5., Richard W, Colina. _ ‘,1936.' ' IIIIIIIIIIIIIIIIIIIIIII 93 00999 0528 PLACE IN RETURN BOX to remove this checkout from your record. To AVOID FINE return on or before date due. MAY BE RECALLED with earlier due date if requested. DATELPUE DATE DUE DATE DUE A.Gamparieon of 20 deg. 0. Biochemical Oxygen Demand and 57 deg. C. Biochemical Oxygen Demand A fheais Submitted to The Inculty of .IICHIGAH SIAEE COLLEGE of AGRICULTURE AND APPLIED SCIENCE By Richard I. 9113:. Candidate for the Degree of Bachelor of Science June 1956 IABLE OF CONTENTS INTRODUCTION ................................................. The B.0.D. Determination ................................ Relation of Time and Temperature ........................ Dilutingilater'.......................................... Objections to Present Hath“ 0.0.0.0....OOOOOOOOOOOOOOOOO W 0......0.0.0.0000...OOOOOOOOOOOOOOOOOOO0.00...0.. Fromm OOOOOOOOOOOOOOOIOOO0..O...OOOOOOOOOOOOOOOOOOOOO Raul“ 0......OOOOOUOOOOOOOOOIOOO-OOOOOOOOOOOOOOOOOOOOOOO conclmim OOOOOOOOOOOOOOOOOO0.0.0.....00...00.000.00.00 MIM OOOOOOOOOOOOOO0.0....0.000000000000000.0.0.000... 1033 3:5 Page 10 15 16 ACKNOELEDGIENT The writer wishes to express his sincere appreciation to Ir. E. F. Eldridge for his guidance and helpful suggestione . sum 0F PROBLN The object of this problem is to develop a 57 deg. C. biochemical hunch demand test which 1-111 be comparable to the 20 deg. C. biochemical oxygen domed but at the same time decrease the time of incubation. INTRODUCTION The biochemical demand test (B.0.D.) is a valuable determination for measuring the degree of purification in sewage treatment and in making stream pollution surveys. It may be defined as the amount of ouygen required by aerobic bacteria to oxidize the organic matter in the sewage or stream water. Because of the dis- crepancies which may arise during this detemination, there has been a great deal of experimentation and discussion regarding the factors influencing this test. ODDe Before discussing these factors, the standard technique and procedure will be explained. In obtaining samples from streams, ponds or rivers a special typeofsamplingapparatusmustbeused. Thisequipmsntshouldbesuch that the liquid in the sampling bottle is collected without entrainment of air bubbles. Tests should be run as soon as possible after collection. 1! normal songs is being tested, it is necessary to dilute the samples tosuchanutentthattheoxygenmillnotbedepletedbeforetheendof the period of incubation. In preparing the desired dilutions, the essential requirement is to obtain samples that are uniform in regard both to distribution of the waste and to dissolved oaygen content. A very simple method of dilution is obtained by adding suitable Imotmts of se-age directly to bottles of known capacity. Dilution ester is first siphoned from its container to the bottles, each bottle being fibouthaleined. Therequiredamountsofsewageareaddedandthe reminder of the bottle filled ‘with more diluting water. The bottles arethensealedbymeansofawater sealandplacedinaZOdeg. 0. incubator for a definite period of incubation. The time of incubation is usually 5 days, after which each dilution and the diluting water is tested for dissolved ocygen content. The difference between the d.o. of the diluting water and that of the dilution is the B.O.D. This determination is based upon the fact that a polluted eater cmtaining bacteria, if exposed to ongen will eventually become completely purified. During this time period, definite amounts of dissolved ocygen are absorbed, and since this rate of absorption of the mgen by the polluted water is very slow , the incubation period is ‘ extended over a number of due. Also, since the reaction is biochemical, the temperature at which the test is run is carefully controlled. A variation in temperature of one degree causes a change ofabout 5 per cent in the specific rate of deomygenation. Therefore, in order to obtain consistent results the temperature of incubation must be kept constant. Experiments were run by the U. 8. Public Health Service“) primarily for the purpose of confirming the accuracy of various time md temperature correction formulas. These superiIents also proved that factors other than time and temperature mat be considered before a reasonable interpretation of results can be made. Representative samples for the experiments were taken from the Ohio River. From these samples, sub-samples were made up by siphoning into 550 c. c. capacity bottles. The initial ongen content was then determined, and the examples were incubated at 9 deg., 20 deg., or 50 deg. C. The observed oxygen demand values for the different temperatures were plotted against the period of incubation. These results, as shown in Big. 1, showed quite a similarity between the results obtained at the different temperatures of incubation. In order to illustrate the rate of deocxygenation, the 20 deg. 0. (middle curve) will be used. It is evident that the rate of de- mgenation decreased uniformly during the first nine or ten days. During the next five or six days small quantities of oxygen were absorbed, but it was noted that after the sixteenth day, there was a marked increase in the rate of deocxygenation. This increase bears out a view expressed by Adeney and other British experimenters (1) , that under aerobic conditions the stabilisation of organic matter proceeds in two different and con- secutive stages - the carbonaceous matter is first oxidised; then nitrification sets in. This second point of inflection cm the curve marks the onset of the nitrification stage. In confirming the formulas, only the average oxygen demand values corresponding to the first stage were considered. The results obtained were then compared with a formula preposedoby Phelps“). This formula is based on the assumption that the rate of deocygenation at any instant is directly proportional to the amount of organic matter present in the sample. Expressed as a formula: Rate of demgenation = sLiLqu. zit: = x1 t. (1) dt (11: where , MICHIGAN STATE COLLEGE Ir" o (If-l . . 4., “sentient, ., serenade n l ‘QQ'sva i iv a . i r La = oxygen absorbed during first stage L orygen requirement of the sample at time, t K1 a constant at given temperature The integration of expression (1) leads to the equation La La 1°: T where, I =orygenabsorbedin t days I = 0.4545 K1 = deoxygenation constant Solving for I in equation (2) , the following equation is obtained, 1 = La (1 - 10" K1") (5) The results of the observed and computed values are shown graphicallyinrig. 2. Inordertoplaceallthevalues ona comparable basis, the data has been plotted as a percentage of oxygen absorbed during the first stage of deozygenation instead of in parts per million. For periods of incubation of less than 8 days at 50 deg. 0., 10 days at 20 dog. 0., or 15 days at 9 deg. 0., the agreement between the observed and the computed percentage values is very good. In plotting the curves representing the computed values, the valueof I wascomputedbytheequation: Kr = 320 (hour-2°) (4) where, «IlI «I‘M. inn-1.. Ilse-III- .... m, _. _. .. . .ve..e-<.vo .4 I... . .4 III, I . ... .2. . ..v . :3... VI oi MICHIGAN STATE COLLEGE inexohbbotnwu .. .. Hunteiubnenth ,5 a6 . . . I, = the deoxygenation constant at T deg. 0. x20 = “‘9 dam‘Fgenation constant at 20 deg. c. = 0.100. If these formulas are applied to heavily polluted waters, it is possible, within certain limits, to convert the ocygen value obtained at on temperature over an period of incubation into terms of the oxygen demand value which would have been obtained under any given set of conditions. for samples which have-reached a higher degree of purification, Fig. 1, will again be used with the assumption that the five-day oxygen demand of the sample at 20 deg. C. , had been determined after a pre- liminary conditioning period of 7 days. Under this assumption the ob- served depletion would have been about (2.8 - 2.5) = 0.5 parts per million. If the test had been delayed for 15 days, so that nitrification was about ready to set in, the observed loss of orygen would have been about (4.1 - 5.1) = 1.0 parts per million. If a sewage effluent has been diluted 50 times before conducting the test, the oxygen demands would be 25 or 50 parts per million, depending on how much preliminary purification the sample had received. Under these conditions the five—day oxygen demand ofthemorehighlyoridizedsamplewasapparentlytwiceasgreatasthat of the same sample in a less highly purified state. This discrepancy may be due to the fact that one set of values were selected from the flat portion ofthecurve. Thus, afive-day oaygendemandof, say,.20parts per million is not of much value unless a great deal is known concerning the state of oxidation of the sample. The conclusions as given by the writer of the report, Emery J. Thoriault are as follows: 1. 'The Phelps formula holds with reasonable accuracy when applied to samples recently polluted with organic matter. " 2. "For periods of incubation of less than 10 days it is possible to refer the results obtained under standardised laboratory conditions to the actual times of flow and temperatures of a stream." 5. 'Under aerobic conditions the stabilization of organic matter apparently proceeds in two distinct stages.‘I 4. "The rate at which a polluted water is deoxygenated depends largely on the condition of the sanple with respect to its state of oxidation.‘ 5. “It is necessary to exercise considerable caution in interpreting the results of analyses when the nitrification stage has almost been reached.‘I W An important factor which must be considered in the B.O.D. determination is the type of diluting water used. Because of the various diluting waters used new discrepancies arise. Usually the diluting tater is obtained from the stream being studied, but the results obtained Vith the water from one stream will not be comparable with the results from another stream. is a result of the lack of uniformity in the use or various diluting waters, there has been much experimentation and cl‘lascussion on the subject in order to obtain a standard diluting water. The factors affecting the water are the influence of pH on oxygen demand and bacterial count, and the influence of the mineral constituents °r the diluting water on the oxygen demand and bacterial count under canatent pH conditions. A study of various diluting waters was made by Messrs. E. F. Eldridge and I. L. Hallmann (2). In this study, the college tap water was used as a standard to measure the other waters, because it gave the highest B.O.D. reading in the five—day period of incubation. The diluting water, according to the above writers, should be a mineral containing medium which has no oxygen demand, but which does furnish the proper mineral requirements and hydrogen ion concentration for the growth of the bacteria. Five diluting waters with different pH values were used in these studies. 'The first was tap-water with a pH of 7.5; the second, distilled water, pH 6.2; the third, distilled water with 500 parts per million, lag 005, pH 8.5; the fourth, distilled water with 300 parts per million, Na 3005, pH 7.5; and the fifth, distilled water with 500 parts per million, lag ml, pH 7.6.' These waters were first drawn into five gallon bottles, one c.c. of sewage being added to each bottle, and the contents were then aerated for five hours. This was then allowed to stand two weeks to satisfy the natural demand of the water. The sewage used was obtained from the East Lansing Imhoff tank. Dilutionsonpercentand5percentweremadeofthissewagein4 liter quantities. These dilutions were then siphoned into 250 c.c. bottles which were sealed with a water seal to prevent aeration during the determination. These samples were incubated at 20 deg. C. for a definite POriod of time. The pH was determined at the start of the incubation, halt us through the series and at the end. The B.O.D. were calculated and the results shown in graphical form in Chart 1. The tap water curve is smooth as compared to the other waters MICHIGAN STATE COLLEGE which had a considerable lay in the oxidation. This was primarily due to the effect of the lydrogen ion concentration on the growth and activity of the bacteria. The pH determinations which were made at varying intervals showed very little change in the pH. The pH of the 5 per cent tap water dilution dropped from 7.5 to 7.1 at the end, and the distilled water from 6.2 to 5.7. The others remained approximately the same. The results of the determination showed that a water containing the mineral salts common to natural waters was superior to distilled, bicarbonate, carbonate and phosphate waters. The two limiting factors were found, the pH value and the mineral salt content. This study proved that the type of diluting water does greatly influence the B.O.D. results; this influence being due somewhat to the two factors mentioned above. Another stow of diluting waters was made by lessrs. H. Henkelehian and I. S. Chamberlinw). The following waters were used in their study: 1. "Stream water from Great Egg Harbor Creek, near Icy-mouth, in the southern section of New Jersey.'. 2. “Stream water from North Branch, a tributary to the Raritan, in the central section of the state“. 5. “Stream water from Pequest River, tributary to the Delaware, in the northern section of the state." 4. “Sodium bicarbonate water - 100 parts per million.‘' 5. 'Sodium bicarbonate water - 500 parts per million.‘ 6. 'Synthetic water of following composition, as suggested by Iohlnn.‘ w.(‘ u.‘ . .y Held! ‘ HeHGOs - 65partspermillion 0a 012 - 10 ' ' ' Ga 304 - 15 ' ' ' '8 30‘I _. 10 s w m 7. 'Phosphate water, as suggested by Theth - 42.5 parts per million of mg P04 neutralized with ll/l laOH.‘ s. "Distilled water.‘ Foreign matter was removed from the stream waters by filtering, thewaterthenbeingallowedtostandtwoweeks soastosatisfytheir original B.O.D. The waters were analyzed for B. Cali, dissolved oxygen, pH value, alkalinity, acidity, total solids, ash, chlorides, sulphates, and iron. The biochemical oxygen demand determination was made according to the 'Standard lethads.‘ The period of incubation was 5 days at 20 deg. C. for each type of water. A few cmclusions derived from the results of this experiment are as follows: 1. The B.O.D. values of the three stream waters used as diluting water were different in each. case. 2. The lowest B.O.D. value was obtained from the stream water with the lowest salt concentration. 5. then the artificial waters were used, the B.O.D. values were similar. 4. The B.O.D. value of distilled water was low. The results of this study were somewhat similar to those made by lea81‘s. Eldridge and llallmann. I new. .35..»9 ‘ 10 W The biochemical oxygen demand determination is a valuable test for measuring degree of pollution of streams and for the comparison of the relative strength of wastes. The test has some objections, the main one being the length of time required to complete the test. Twenty days usually is adopted as the period required for the almost complete oxidation of sewage dilutions when incubated at 20 deg. 0. Since this is too long a time to await for results, it is common practice to use the five-day demand for calculating the B.O.D. of given sample. Even the five-day period is too long a time to complete the test. .13 15A .mmnqaflfifi ‘ WMAL More. The original procedure planned was to run three series of tests, each series to be composed of 5 per cent and 10 per cent dilutions incubated at 20 deg. 0. However, it was found that the 10 per cent dilutions were not giving desired results. In order to have comparable results, two series were set up having dilutions of 5 per cent and 2 per cent. Each series was made up of forty bottles, eight bottles of each dilution incubated at 57 deg. 0., and eight at 20 deg. C. These were tested for B.O.D. at one, be, three, four, five, seven and fifteen days. Included in the series was a set of eight diluting waters. no B.O.D. was computed by taking the difference between the dissolved anygen of the diluting water and the dilution. . The dilutions were made up as explained in the introduction, the effluent from the East Lansing Imhoff tank being used. m The results of each series compared favorably with one another, the only series not giving a desirable outcome being lo. 2. no reason 0811 be given for this unless there was some carelessness in making up the dilutions or the sewage used had a greater oxygen demand. The values of the observed oxygen demand were plotted against the Period of incubation. The curves for each set are illustrated by charts shown below. Each chart has the set number designated. It may be MICHIGAN STATE COLLEGE . n . .., 'e '....,u no». a. .. a MICHIGAN STATE COLLEGE lll-l.nlll E 0 E L L O C E T A MICHIGAN :I .o -:.-1LVH noted that there is a certain amount of parallelism between the results of different dilutions obtained at different temperatures. In order to obtain average values of all the sets, the results of each one were changed from.parts per million of oxygen consumed to a percentage of the oxygen consumed in ten days. Only the 5 per cent dilutions were used, because the results on these were more consistent. The percentages are shown in the following tables: SETID. I 20 deg. C. 57 deg. G -#7 1st Day 27.: per cent 44.8 per cent and - 52.0 a s 55.5 I - 5rd - 54.0 a a 55.0 n a 4th a 57.8 v s 58.4 - ' 5th n 49.0 v s 85.5 n a 7th v _ 54.7 n - 88.0 s . 10th " 100 ' I ' 100 " “ u. I! I» will} SET NO. III 20 deg. c . 57 deg. 0. 1st Day 18.7 per cent 48.9 per cent 2nd " 50.5 " " 67.5 " " 5rd " 56.4 " " 68.4 ' " 4th " 59.0 " " 75.5 ‘ " 5th " 42.4 " " 85.5 " " 7th " 86.5 " " 92.0 ' " 10th " 100 " ' 100 " ' SET ll). 1" 20 deg. Ge 57 daze Ge 1st Day 55.7 per cent 60.7 per cent and " 42.9 " " 85.0 " " 5rd " 57.2 " " 69.0 ' " 4th " 57.2 " " 76.0 " " 5th " 76.0 " " 88.0 ' ' 7th " 78.6 " " 95.0 " " 10th ' 100 ' ' 100 a a 15 .p'inr- ' OJ m. W”: L! ,I.. . 1". v. .. tin ‘ .. ..-..IJ 14 The average values of the three sets are: 20 deg. 0. 57 deg. 0. let Day 27.2 per cent 51.4 per cent 2nd ' 55.1 I - 67.9 s - 5rd ' 42.5 s s 64.1 sq ' 4th a 45.0 . '- 69.9 s . 5th ' ‘ 55.8 s s 79.0 a - 7th a 75.2 s s 91.0 - s 10th - loo ' s 100 s - There is some discrepancy in these results. The second day under 57 deg. 0., has a higher percentage of omygen consumed than the thirddq. The cause ofthis isnotknownastherearesomanytimes .duringthetestwhereanerrormayariseduetotechnique, etc. Promthese averagevaluesacurve, as shownbyrig. 5, was plotted. If you. take the five-day period of incubation and trace up tothe 20deg. 0., curveandthenovertothe57deg. 0. curve, the time period is decreased from five days to approximately two days. This ratioisfairlyconstantas canbeseenfromthecurvesaftera time period of two days has passed. The, by incubating the samples at 57 deg. 0., the time period is decreased. Just how this may be applied tothe standardbiochemicaloaygendemanddeterminationsoastomakee reasonably accurate and consistent procedure, it is hard to say. There are so mam other factors which enter in during the test. “mm a”.- - ‘d’hw .wu. ILL' _'~.-.-.‘ HIM. .LI\IIHI' E4 MICHIGAN STATF COLLEGE . T 7. _. . .2 g 7 _.H ..; .. a . ,:.,.V . . A“... A. , .M - a. .w :__: . . .., v . . .H. H .._. .«, u w.” .H . ,2 :._ t-.. names. y. . iv? I. .. ¢ .7 . . . 10.: hloi‘h...‘ 7... ...n ,. II.I..I|.|11.1!J.II¢I..I .. n'v-Anvulu‘i OP unwind nee w «gmuathhta «he: who. 0\ swam“ :x.-.r-.ul.: .MWL We 1. The tine period is shortened considerably using 57 deg. 0. incubation as compared to 20 deg. C. incubation. 2. The determination Inst be carefully run in order to obtain consistent results. 5. Inch depends on the condition of the sample with respect to its rate of deorxygenation. 15 (1) (2) (3) (4) (5) 16 BIBLIOGRAPHY "The Rate of Deoxygenation of Polluted Waters,“ by Mary J. Theriault, U. S. Public Health Reports, Vol. 41, No. 6. 'The Influence of Diluting later on the Biochemical Oxygen Demand," by E. F. Eldridge and I. L. W, Michigan Engineering Experiment Station Bulletin, Vol. 7, Ho. 1. 1951. 'The Effect of the Dilution Water on the Biochemical Oxygen Densnd Datamation," by H. Henkelekian and I. S. Chamberlin, Sewage Iorks Journal, Vol. 5, No. 2. 'Studies of Biochemical Oxygen Demand of Trade Wastes," by E. F. Eldridge, hgineering News Record, July 5, 1950. 'Becomended Uniform Procedure for B.O.D. Determinations,“l Sewage Works Journal, Vol. 4, lo. 5. September, 1952. 534‘ c”....‘- (It-(l, e trinil.Ltuln“f. ''''' LII? ' Nuum 05E ONLY NI CHIGRN .‘ TOTE UNIV LIBRQR IIIIII III I III 31293009990528