The role of elemental oxygen demand in total oxygen demand for water pollutants

14.'uter Re,. Vol. 16. pp. 1003to 100q. 1982 Printed in Great Britain.All rights reserved

0043-135482 061003-07503.000 Copyright ~ 1982 PergamonPress Ltd

THE ROLE OF ELEMENTAL OXYGEN DEMAND IN TOTAL OXYGEN DEMAND FOR WATER POLLUTANTS KUNIO NAKAJIMAt, TOSHIO ISHIZUKAt and HIROSHI SUNAHARA 2 tGovernment Industrial Research Institute, Nagoya. Hirate-machi, Kita-ku, Nagoya 462 and ZDepartment of Industrial Chemistry. Hiroshima University. Scnda-machi. Hiroshima 730, Japan (Receieed October 1981)

Abstract--For an advanced evaluation of water pollutants. EOD (elemental oxygen demand) was proposed, and the relation between EOD and TOD (total oxygen demand) was discussed. The EOD was defined as the oxygen demands of each element in the pollutants. A generalized equation of combustion reaction for compounds was proposed. The observed TOD values of various organic and inorganic compounds, except a few inorganic compounds, showed good agreement with the theoretical values calculated from the equation, and the TOD.value was the summation of the amounts of EOD by each constituent element. The degrees of COD (carbon oxygen demand). EOD of carbon, and NOD (nitrogen oxygen demand), EOD of nitrogen, in TOD were investigated by using several organic compounds. The ratios of CODfI'OD and NOD/TOD were generally above 0.5 and below 0.25. respectively, in an activated sludge pilot plant, the ratio of COD/rOD in influent was 0.76 and that of NOD/q'OD 0.075; and in effluent, the NOD/TOD value was larger than the COD/TOD value.

INTRODUCTION The water quality for environmental water, industrial wastewater, sewage, etc. has been estimated with biochemical oxygen demand (BOD) or chemical oxygen demand (COD) for many years. Recently, total organic carbon (TOC) and total oxygen demand (TOD) (Clifford, 1968) have been proposed and the studies on the relationships among BOD, COD. TOC and TOD have been evaluated (Davis, 1971). It is difficult to clarify these relations, because BOD, COD, TOC and TOD are based on different principles. BOD and COD tests are used to determine the oxygen consumption by organic pollutants in waters and the TOC test is used to determine only the amount of organic carbon. The TOD test is based on measurement of the amount of oxygen consumed when organic and inorganic pollutants in waters are oxidized at about 900:C using a catalyzer. It has been understood that a TOD value is a summation of the amounts of oxygen demanded by each constituent element of the pollutants, but the degree of the amounts of oxygen demanded by each element in the TOD value has not so far been elucidated. When each amount of the constituent elements of the pollutants are known, the oxygen demands of each element must be evaluated. When the oxygen demand is defined as elemental oxygen demand (EOD). EOD can be used in the evaluation of TOD as a polluted-water quality. in this report, the fundamental relationship between TOD and EOD to various organic and inorganic compounds in water was studied using a TOC-TOD analyzer and a TN (total nitrogen) analyzer and the influent and effluent in an activated sludge pilot plant were analyzed as practical samples, The EOD values of carbon and nitrogen in the con-

stituent element of water pollutants were measured and the degrees of those in T e D were discussed. EXPERIMENTAL Apparatus

A TOD analyzer (Ionics` U.S.A., model 225) was reconstructed with a NDIR (nondispersive infrared, Hartman & Braun, West Germany. model URAS-2), a low-temperature furnace, etc., so that TOD and TOC were simultaneously measured. Figure I shows 2oo ~m o2/a~

~ 2"~ ,

~

~ .I =---~-~

~-

) (~l ~ [IA,

a_.. [~.~

• s,mpJ, [~

~ s

~

~-

a

r,p ,,~r Fig. I. Schematic diagram of TOC-TOD analyzer. I and I': flow meter: 2: automatic slide injection valve: 3: hightemperature furnace tube (quartz. 2.-cm dia. 40-cm length); 4: high-temperature electric furnace; 5: low-temperature furnace tube (quartz. 2-cm dia. 40-cm lengthl; 6: Iow-temp.'rature electric furnace; 7: condenser (glass): 8: filter (Nupro 4FR-7); 9: NDIR: 10: oxygen detector: 11: chart recorder; V~ and V,: three-way ball valve (Whity 43XS4-316).

1003

KL "MO N~.KAJIMA t,r ~I/

1004

a schematic diagram. A condenser (71. a filter (8) and the NDIR unit 19) were arranged in a series on the lines from the high-temperature furnace tube 13) (line A) and the low-temperature furnace tube (3) (line B) to the oxygen detector (I0) in the TOD analyzer. Line A was used for the measurement of TC (total carbon) and TOD, and line B for IC (inorganic carbon). Lines A and B were controlled with two three-way ball valves, V~ and V,,. The TOC value is obtained by the subtraction of the IC value from the TC value. For TC and TOD measurement (line A), the flow rate of carrier gas (200 ppm oxygen in nitrogen balance) was controlled at 200 ml min- t (line A z) and 2 ml min- ~ (line A,); and for IC measurement (line B), it was controlled at 200 ml min-t. Tubes (3) and (5) contained catalyzers of platinum gause pellets and phosphoric acid-wetted quartz-chip packing, respectively. Furnaces (4) and (6) were maintained at 900 and 150°C. respectively. Sample injection was carried out with a slide injection valve (2) for the measurement of TC and TOD and with a microsyringe for that of IC. A TN analyzer constructed by Miyagi et al. was used. The instrument is described in detail elsewhere (Miyagi et al., 1976).

ford. 1968L Other constituent elements of the organic pollutant such as sulphur, phosphorus, hatogenetic. must relate to the consumption of oxygen. However. the final oxidation state of those elements is not wellknown. Therefore, TOD for various organic compounds containing sulphur, phosphorus and halogen was measured and the observed values were compared with the theoretical values calculated from following the assumed reaction equation in the combustion of organic compounds. S + 02 = SO,, 4P + 5 0 , = 2P,O5. X + H = HX, where S is sulphur, P phosphorus, X halogen, O oxygen and H hydrogen. The results are shown in Table 1. Each value is the average of five measurements and the results agreed well with the theoretical TOD values calculated from the following assumed combustion equation: 2C, HbO, N4S,P/XgM~' -,- nO2 = 2 a C 0 2 + (b - g)H20 + 2dNO + 2 e S 0 2

Reagents

A standard solution of potassium biphthalate (KHP) was prepared by dissolving the Reagent Grade KHP (Wako Pure Chemical, Japan) in CO,-free distilled water, and the solution was used for the calibration of TC and TOD. The standard solutions of sodium carbonate (Wako Pure Chemical. Reagent Grade) and sodium bicarbonate (Wako Pure Chemical, Reagent Grade) were used for that of IC. Caffein (Kishida Chemical, for organic micro-analytical use) was used as the standard solution for the measurement of TN. The solutions of the other organic and inorganic compounds were prepared from the organic micro-analytical reagent grade chemicals (Kishida Chemical) or reagent grade chemicals (Wako Pure Chemical). RESULTS AND DISCUSSION T O D o f organic compounds

It is considered that each constituent element of the organic pollutant in water is converted to the corresponding oxides, and then oxidized at 900°C in the presence of a platinum catalyzer, If the amounts of each element constituting the organic pollutant are known, the oxygen demand of the elements can be estimated. Therefore, the TOD value of the organic pollutant can be estimated as a summation of the oxygen demands of each element. In the combustion reactions of organic pollutants containingcarbon, nitrogen, hydrogen, metals, etc., it has been assumed that carbon is converted to carbon dioxide, nitrogen to nitrogen monoxode, hydrogen to water and metal to metal oxides such as sodium to sodium oxide and potassium to potassium oxide (Clif-

+fl:~O~ + 2 g H X + 2 h M O o . s , , ,

(1)

where subscripts a - h in the general formula C,,HbO, N,fS,.P/.X~M~ are the numbers of each element, M metal, m the valence of M. and n is mot of 02 gas. As H and X is converted to HX. the second term on the right side of equation (i) is expressed as (b - gl. n is given by n = 2a + 0.5(b - g) + d + 2e + 2.5f + 0.5mh - c (2) The amounts of each constituent elements of the organic compound are shown as TOTS. TOH Itotal organic hydrogen), TOO (total organic oxygen), TON (total organic nitrogen), TOS (total organic sulphur), TOP (total organic phosphorus), TOX (total organic halogen) and TOM (total organic metal). When 1 mot of the organic compound is oxidized, the numbers of grams of TOD, TOC. TOH. etc. are written from equation (1) as follows:

TOD = 16n. TOC = 12a, TOH = b, TOO = 16c. TON = 14d, TOS = 32e. TOP = 31]:. TOX = AW(X)a, TOM = AW(M)h, (3) where AW(X) and AW(M) are the atomic weig#ts of halogen and metal, resl:mctively. Equation (4) is derived from equations (2)and (3): T O D = 16n = (8/3)TOC + 8TOH + (8/7)TON + TOS + (40/41)TOP + [gm/AW(M)}TOM - TOO - 18/AW(X),WOX. (4) From equation (4), it is found that the less the TOD and/or the TOX is. the larger the TOD becomes

Role of elementaloxygen demand

1005

Table l. TOD of various organic compounds Sample No.

Compound

Conch (ppm)

1 2 3 4 5 6 7 8 9 10 II 12 13 14

CjH60 C3HIO C3HsOz C.)HsO2 C~HIO3 CoHsOzNzS CH,NzS C3HvOzNS C~H~O,P C~H~OzF~ CbHsOCI C2HO2C1~ Cz, H,~OsBr4SNa C~HsOzl

100 100 100 100 100 60 60 101 97 143 62 102 102 111

TOD (ppm) Th¢o. Obs. 220 240 168 168 122 lO0 100 140 100 93 100 100 100 100

215 233 162 170 119 103 104 140 100 88 97 106 103 95

Recovery (%) 98 97 96 101 98 103 104 100 100 95 97 106 103 95

Sample No. I: Acetone: 2: n-propyl alcohol: 3: Propylene glycol: 4: methyl c¢llosolve: 5: glycerin: 6: sulfanilamide: 7: thiourea: 8: L-cysrein: 9: trimethyl phosphate: 10: heptafluorobutanol : I 1: o-chlorophenol. 12: trichloroacetic acid; 13: bromocresol green sodium salt: 14: o-iodobenzoic acid. For example, the reaction of C2~HI~OsBr,)SNa in

TOD of inorganic compounds

Table 1 is 2CzlHt~OsBr,SNa + 44Oz = 42CO2 + 9HzO + 2SO2 + 8HBr + NazO.

As many kinds of inorganic compounds exist in industrial wastewater and environmental water, their oxygen demands should be considered. If inorganic compounds are included in a sample which was From the above equation, the theoretical value of injected into a platinum catalyzed combustion tube TOD of 102ppm C21H~3OsBr4SNa is 100ppm. The' maintained at 900:C. it is difficult to explain their observed value agreed with the theoretical value, pyrolytic reaction.

Table 2, TOD of solution containing 85 ppm KHP and 100 ppm inorganic compound Sample No.

I

Addedinorg. T e D (ppm) compound Thee. Obs.

Recovery (5~)

None HCI NaCI NH,CI CaCI2 CuCI2 FeCl3

100 100 100 17.S 100 100 100

t00 103 102 173 100 102 96

100 103 102 99 100 102 96

8 9 10 11 12 13

H2SO, NazSO4 K2SO, MgSO4 (NH,)zSO4 CuSO4

83 87 92 87 155 90

101 98 100 100 155 92

121 112 109 115 I00 102

14 15 16

HN03 KNO3 NH,NO3

62 76 120

54 69 ! 12

87 90 93

17 18

Na2CO3 NaHCO3

100 100

102 102

102 102

19 20

NaHzPO, NazHPO,

100 100

102 103

102 103

21

NaOH

I00

105

105

2 3 4 5 6 7

Some inorganic compounds, as well organic compounds, may be oxidized in the presence of a platinum catalyzer at 900:C, and oxygen may be consumed in the pyrolytic reactions. In order to study the degree of the oxygen demands of various inorganic compounds in water samples containing KHP. various inorganic salts, such as chloride, sulfate. nitrate, carbonate and hydroxide were examined. Test solutions were prepared by adding each of the inorganic compounds to KHP solutions. The concentrations of each inorganic compound and KHP were 100 and 85 ppm, respectively, and the T e D value of 85ppm KHP was 100ppm. The T e D values of the test solutions were measured, and the results are shown in Table 2. It was assumed that in the pyrolytic reactions of inorganic compounds, each constituent element of the compounds is converted to the final products mentioned in the previous section: C is converted to CO2, N to N O . H to HzO. M to metal " oxide. S to SO2. P to P2Os, and X to HX. The theoretical values in Table 2 are based on these pyrolytic reactions. For example, the pyrolytic reaction of NH,CI is: 4NH,,CI + 5Oz = 4NO + 6H20 + 4HCI. From the above equation, the theoretical T e D value of the solution containing 100 ppm NH,LC! is 75 ppm. In Table 2, the observed TOD value of the test solution containing NH,,CI agreed well with the theoretical value.

]04)¢3

K L % I O ~',~,KeJ[M ~, ~,J ~,

Table 3. Recoveriesof nitrates in three p~ro[~tlc reaction equanons Added inorganic compound

Obser',ed Theoretical TOD TOD ~alue value (ppm) Ippm) Equation 161 Equation 17~ Equation 181

HNO3 KNO3 NH.,NO3

5-1 69 112

62 76 120

37 60 80

49 68 110

Equation {61

Reco,, er.,, I~.l Equation ~71

Equation ~bl

8.7 91 93

l-t6 I [5 1.10

II0 09 102

Equations (6). 17) and ~8): Reaction based on N -.-, NO, N ~ N: and N --, NO + N,. respectively. In the pyrolytic reaction of CaCI,, Ca is converted to CaO and CI to HCI. Therefore, in order to produce CaO and HCI in the formation system, a compound consisting of oxygen and hydrogen is required in the original system. Water in the test solution is regarded as a suitable compound, and the water reacts with CaCIa as follows: CaCI2 + H20 = CaCO + 2HCI. Consequently, the theoretical TOD value of CaCl 2 is zero from the above equation. The pyrolytic reactions of NaCl. CuCI2 and FeCI 3 are the same as that of CaCI 2. Table 2 shows that the observed TOD values of the test solutions containing NaCI, CuCl> CaCI a and FeCI 3 were 100ppm which corresponded to the TOD value of 85 ppm KHP, and agreed well with the theoretical values, As shown in Table 2, the observed TOD values of the solutions containing ammonium and cupric sulphates closely agreed with the theoretical values. It is considered that the pyrolytic reaction of both ammonium and cupric sulphates is: (NH,,)2SO,~ + 202 = 4H20 + 2NO + SO,, 2CuSO.~ = 2CuO + 2SO2 + 02. For sulphuric acid and sulphates of sodium, potassium and magnesium, the observed TOD values were higher than the theoretical values in Table 2. The observed values were nearly equal to the TOD value of KHP alone: namely, the above four sulphates did not consume oxygen. It is considered that in the pyrolytic reactions of those sutphates, sulphur trioxide is generated, and the gas reacts with water to produce sulphuric acid. The reaction of magnesium sulphate is expressed as follows: MgSO., = MgO + SO3, S03 + H20 = H2SO,,. Consequently. MgSO, + H,O = MgO + H2SO4.

(5)

From these results, it is clear that the TOD values of sulphates depend on the kind of compound. From equation (1). the pyrolytic reactions of nitrates such as nitric acid and nitrates of potassium and ammonium are expressed as follows: For example, 4KNO3 = 2K20 + 4NO + 302. (6)

For HNO3, KNO~ and NH.tNOj. the observed TOD values were lower than the theoretical values obtained from the above equation. From equation (6}, the theoretical TOD value of the solution containing 85 ppm KHP and 100ppm KNO3 is 76 ppm. In Table 2, the observed TOD value was 69 ppm and the recovery was 907,0. In order to elucidate the slight difference between the theoretical and observed values, a few pyrolytic reaction equations of the nitrates were considered. The reaction of KNO3 is discussed below. If nitrogen in KNO3 is converted to nitrogen gas as follows: 4KNO3 = 2K20 + 2N2 + 502.

(7)

the theoretical TOD value of the above solution is 60 ppm. The observed TOD value of 69 ppm is higher than the theoretical value, and the recovery was 115%. If nitrogen in KNO3 was converted to nitrogen gas and nitrogen monoxide as follows: 4KNO3 = 2K,O + N., + 2NO + 402.

(8)

the theoretical TOD value of the solution is 68 ppm The value agreed with the observed TOD value of 69 ppm. and the recovery was 999o. The pyrolyttc reaction of KNO3 probably follows equation (81. Similarly, in the cases of HNO3 and NH4NO> the theoretical TOD values were calculated from the same equations as equations 17) and (81 and the recoveries were evaluated. In the reaction of NHaNO3. NH4-N was regarded as being converted to NO as well as NHa-N of (NH4)2SO, and NH,tCI and NO 3 to NO and N2 as described previously. The equation is: 4NH4NOa -,- 02 = N: + 6NO + 8 H , O The results for the nitrates are shown in Table 3. From Table3. it was found that in the three equations, the decompositions of nitrates, except HNO3, were expressed conveniently by equation (8). The TOD values for carbonates, phosphates, and sodium hydroxide calculated from equation (1) are zero. The theoretical TOD values for test solutions containing each of the above compounds depend on KHP alone. In Table 2. the observed TOD values closely agreedwith the theoretical values. From the results mentioned previously, it was found that equation (1) could be applied to organic and inorganic compounds, except for a few inorganic. compounds. The TOD value of polluted water is de-

Role of elemental oxygen demand

1007

derived from equation (4) as follows: T O D = 16n = (8/3)TC + 8TH + (8/7)TN + TS + (40/31)TP + '¢8m/AW(M)),TM - T O - [8/AW(X)),TX.

(4')

where TC is total carbon. TH total hydrogen. T N total nitrogen, TS total sulphur, TP total phosphorus, TM total metal, T O total oxygen and TX total halogen. It was found that the T O D value is expressed as a summation of the oxygen demands of each element constituting organic and inorganic pollutants in water, that is. a summation of E O D values. In equation (4'). oxygen and halogen in compound show negative demands o f oxygen. In other w o r d s , when the amount of each element in the compound, that is, TC, TO, TH. TN, TS, TP, TX and TM was measured, the T O D value could be obtained theoretically from equation (4').

O r'~ w'~ r ,~

~ _O ~ ~-

,-

~ .r° ~" ._.=

~

t~

~

~.~_O~

~

2: --

N O D = (8/7)TN.

(10)

O

F-.

H O D (hydrogen oxygen demand), O O D (oxygen oxygen demand). S O D (sulphur oxygen demand), P O D (phosphorus oxygen demand), X O D (halogen oxygen demand) and M O D (metal oxygen demand) are also defined in the same manner as C O D and N O D ; O O D and X O D have negative values. Equation (4') is rewritten using each E O D as follows:

o° .~ ~. .--~ .9 ~ ~ ~ ~ ~

As seen from Table 2, the T O D values of carbonates are zero. Therefore, in the subsequent experiments, the following equation was used instead of equation (9): C O D = (8/3)TOC.

r- ~ ,o

(14)

Compounds such as amino acid. carbohydrate and aliphatic acid were selected to determine the ratios of C O D / r O D and N O D f r O D . The results are shown in Tables4 and 5. respectively. In Table4. the ob-

~, o, . . . . .

~" Z

I

~ .

.

8 8

~ 8. ~. ~

g: .~ .-

.

OO ,--= , ~o " ~q

.

~

.

.

~

.o

.

O

g. g.

. ~ .g ~ o

~ 0 r- o ~ {- " "~ ~ ~ ~ i,,~-,, ~ o ,,= r~ -~ -

~ ,,~ ~ ~ "~ " ~. ~, o, ~

,,~ ~ ~ ~ ~

~ ~ •-, ; Z Z Z ~i ~ d

. ~ q .,

~ ' . ~

o ~

-, ~,-r: o0~

~ ~G

~ 00o0

- ~ ~

"* ~

"~ ~" ~ ~"

o ~

.,_o

z

,-

.~

o -~ v-

¢"1 r ~

~ ~r ~ ~ ~, ,~ _ "

o m

(12) (13)

'.-" ~' -=" "~

~ ~ ~ ~

O ~,. i ",-.-~ r - "0 i L~ !

(9)

N O D / T O D = d/n.

,--,.,,

'~

,j

C O D = (8/3)TC,

C O D / r O D = 2a/n,

i.~

~

When the amounts of oxygen consumed by carbon and nitrogen, that is, the E O D values of carbon and nitrogen are shown as C O D (carbon oxygen demand) and N O D (nitrogen oxygen demand) respectively, C O D and N O D are derived from equation (4') respectively, asfollows:

Therefore, if each E O D value in a pollutant was measured, the degree of each E O D value in T O D can be clarified, The degrees of C O D and N O D in T O D are discussed below. From equations (3) and ( 4 l the ratios of C O D / r O D and N O D / r O D are

~

----~

~ ~ ~

O ~

E

(ll)

~,~ ~

o--

O

Relationship between TOD and EOD

TOD = COD + HOD + NOD + SOD +POD+MOD-OOD-XOD.

o~. ~ .

~o~

o •<~ ~

o ~ ~

,~'-o ~ ".~

~

.y, o ,_6 q: U .=

':";

,:4 b" ~ "=-~

I,'~)x

K I \ I O ,NAKAJIMA t'f ~I:

Table 5. Relationship between NOD and TOD in organomtrogen compounds Conch

Theoretical ~ppm) NOD TOD

Compound

(ppm)

TN

Thiourea (CH+N ,S)

.i 59

58

66

:~-Alanine (C~H,O,N)

318

50

Sulfanilamide (C6H 80:N.,S)

307

50

Observed (ppm) NOD TOD

NOD, T O D

TN

267

0.25

57

65

260

0.25

57

486

0.12

49

56

480

0.12

57

514

0.1 t

51

58

525

0.11

served C O D / r O D ratios of each compound of a m i n o acid. carbohydrate and aliphatic acid agreed well with the theoretical ratios. The degrees of C O D in T O D were over 50?0 for all test solutions. The C O D / T O D ratios of sample numbers (4), (5), (6) and (7) were over 1 because of the high O O D values. In Table 5, the observed N O D / T O D ratios of each organonitrogen compound agreed well with the theoretical ratios and the degrees of N O D in T O D were 11-25%. A generalized composition formula of organic pollutants in environmental water, industrial wastewater, sewage, etc. is not clear. A generalized composition of protein is regarded as C = 52.5, H = 7.0, O = 22.0, N = 17.0 and S -- 1.5°o (lwai et al.. 19711, and the ratios of C O D / r O D and N O D / r O D are 0.72 and 0.I0. respectively. Those ratios are nearly equal to those for alanine as shown in Tables4 and 5; namely, 0.71 for C O D / T O D and 0.12 for N O D / r O D . For microbes in activated sludge. Hoover et al. (19521 have presented a composition formula of CsH~NO2. For this. the ratios of C O D / T O D and N O D / r O D are 0.8 and 0.08, respectively, From Tables 4 and 5 and the results mentioned above, the ratios of C O D / r O D and N O D / T O D for the organic pollutants can be estimated to be above 0.6 and below 0.25. respectively,

NOD,TOD

TOD and EOD of practical samples

firm the above arguments, influent and effluent in a pilot plant with activated sludge were measured as practical samples and the E O D and T O D values are discussed, Artificial influent with the components shown in Table 6 was prepared. Loading to the actirated sludge was changed with a quasisinusoidal pattern over a period of 2 h. Phenol. acetic acid and ammonium sulphate in the influent have positive T O D values, and the T O D values of other compounds are zero as described in the previous section. C O D , N O D and T O D values at the minimum and maximum loading were calculated. The values are shown in Table 6. The mimmum and maximum T O D values were 521 and 1601 ppm, respectively, The C O D / r O D ratio is 0.75 and the N O D J T O D ratio 0.073. Water samples of influent and effluent in the pilot plant were taken. TOC. T N and T O D were measured. and C O D and N O D were calculated from equations (14) and (10). respectively. The results are shown in Table 7. The ratios of C O D / r O D and N O D / r O D for the influent were nearly constant. The average ratios were 0.76 and 0.075. respectively. These ratios closely agreed with the theoretical values in Table 6. The observed values of C O D and N O D for the effluent were constant. The averages of the C O D / r O D and N O D / T O D were 0.068 and 0.44, respectively. The C O D / r O D ratio for the influent decreased from

From the results described in the previous sections. it was found that E O D in T O D were important for the evaluation of water pollutants. In order to con-

0.76 to 0.068 as the result of the activated sludge process and the N O D / r O D ratio increased from 0.075 to 0.44. It is considered that organic carbon in the

Table 6. Theoretical EOD and TOD of artificial influent at minimum and maximum loading Component

Concn

Ct, HsOH CH~COOH (NH+)zSO+ Na2HPO., K:SO+ MgSO+ CaCI: FeCI3 Total

168 54.3 158 78.0 3.0 6.8 1.9 3.2

Minimum loading (ppm) COD NOD TOD 332 58 0 0 0 0 0 0 390 COD/TOD NOD, rOD

0 0 38 0 0 0 0 0 38 = 0.75 = 0.073

387 58 77 0 0 0 0 0 522

Concn 500 167 482 240 3.0 6.8 1.9 3.2 --

Maximum loading (ppm) COD NOD TOD .1020 178 0 0 0 0 0 0 1198 COD/rOD NODq'OD

0 0 117 0 0 0 0 0 117 = 0.75 = 0.073

1190 178 223 0 0 0 0 0 1601

Role of elemental oxygen demand

1009

Table 7. The ratios of COD/rOD and NOD/TOD of the inttuent and effluent in activated sludge process

Sample

Sampling time (rain)

COD

0 10 20 25 40 60 80

437 760 1120 1290 1030 781 624

45 73 113 125

tO0 120

517 485

54 46

0 30 60 90 120 (Mean)

4.5 4.3 4.3 4.3 4.8 4.5

29 29 31 29 29 29

lnfluent

Effluent

ppm NOD

influent was mostly decomposed in the process, but nitrogen was not completely removed: and in the elfluent, the relative amounts of nitrogen increased compared with those of carbon. For the influent, the summation of COD and N O D values were 84% of the T O D values: ancl for the effluent, they were 51%. The remaining T O D of the effluent must be

accounted for by HOD, SOD. MOD, etc. CONCLUSIONS EOD was proposed to characterize the T O D value for water pollutants, and a generalized equation of combustion reaction for the pollutant was discussed in an evaluation of the role of EOD in TOD. This paper mainly discussed the degree of COD and N O D in TOD. The C O D , f f O D and N O D / T O D ratios of several organic compounds, proteins, and microbes in activated sludge were above 0.6 and below 0.25, respectively. However, in the effluent of a pilot plant (activated sludge process), the N O D / T O D value was larger than the C O D / T O D value. This

104

76 56

TOD

COD/rOD

NOD/rOD

580 980 1550 1780 1390 tO00 795

0.75 0.78 0.72 0.72 0.74 0.78 0.78

0.077 0.074 0.070 0.070 0.075 0.076 0.070

680 600 (Mean)

0.76 0.81 0.76

0.080 0.076 0.075

0.073 0.063 0.065 0.064 0.073 0.068

0.47 0.43 0.47 0.41 0.44 0.44

62 68 66 70 66 66

means that N O D plays a more important role in the T O D value than in the C O D value. Further, the concept of EOD also serves to characterize the T O D of pollutants in environmental water such as river water, lake water, etc., which, however, were not discussed in this paper.

REFEeENCES Clifford D. A. (1968) Automatic measurement of total oxygen demand--A new instrumental method. Paper presented at the 23rd Annual Purdue Industrial Waste Conference. Indiana, U.S.A. Davis E. IVF.(1971) BOD vs COD vs TOC vs TOD. Water WastesEngng 8, 32-38. Hoover S. R. & Porges N. (1952) Assimilation of dairy wastes by activated sludge. If. The equation of synthesis and rate of oxygen utilization. Sewage /nd. Wastes 24, 306-312. Iwai S., Shin K. & Natori M. (1971) Treatment of Sewage and Waste-Sludge(in Japanese), p. 34, Corona. Tokyo, Miyagi H., Kaw~oe K., Takata T., Arikawa A. & Sakai K., (1976) An analytical method for simultaneous deterruination of total nitrogen and total organic carbon in water (in Japanese, summ. Eng.) Bunseki Kagaku (Japan Analyst) 25, 146-150.