Issued 2012 4.A.1 

(Last Updated March 2012) 

ncasi

Pulp and Paper Mills 

ESTIMATIONS OF THE FATE OF ORGANIC COMPOUNDS IN 

WASTEWATER TREATMENT PLANTS (WWTP) 

1.0 EPA WATER9 MODEL 

Estimates for the partitioning of chemical species in industrial wastewater treatment plants 

(WWTP) have been developed from the use of EPA’s WATER9 software. The following is a 

brief description of WATER9 extracted from the EPA website 

(http://www.epa.gov/ttn/chief/software/water/index.html).

WATER9 is a Windows based computer program and consists of analytical expressions for 

estimating air emissions of individual waste constituents in wastewater collection, storage, 

treatment, and disposal facilities; a database listing many of the organic compounds; and 

procedures for obtaining reports of constituent fates, including air emissions and treatment 

effectiveness. 

WATER9 is a significant upgrade of features previously obtained in the computer programs 

WATER8, Chem9, and Chemdat8. WATER9 contains a set of model units that can be used 

together in a project to provide a model for an entire facility. WATER9 is able to evaluate a full 

facility that contains multiple wastewater inlet streams, multiple collection systems, and complex 

treatment configurations. WATER9 provides separate emission estimates for each individual 

compound that is identified as a constituent of the wastes. The emission estimates are based upon 

the properties of the compound and its concentration in the wastes. To obtain these emission 

estimates, the user must identify the compounds of interest and provide their concentrations in 

the wastes. The identification of compounds can be made by selecting them from the database 

that accompanies the program or by entering new information describing the properties of a 

compound not contained in the database. 

WATER9 has the ability to use site-specific compound property information, and the ability to 

estimate missing compound property values. Estimates of the total air emissions from the wastes 

are obtained by summing the estimates for the individual compounds. 

The EPA document, AIR EMISSIONS MODELS FOR WASTE AND WASTEWATER,

includes the equations used in the WATER9 model (EPA 1994). 
Issued 2012 4.A.2 

(Last Updated March 2012) 

ncasi

Pulp and Paper Mills 

1.3 Waste Treatment Plant (WWTP) Characteristics used as Model Inputs in the 

WATER9 Model 

Table 1 provides the characteristics of the example Activated Sludge Treatment (AST) used as 

model inputs in WATER9. 

TABLE 1 CHARACTERISTICS OF ACTIVATED 

SLUDGE TREATMENT (AST) SYSTEM

Flow, MGD 20 MLVSS, mg/L 2,000

Basin Volume, Gallons 20 x 106 Effluent TSS, mg/L 100

Basin Area, Acres 1 Effluent BOD5, mg/L 250

Basin Depth, ft 61.2 Wind Velocity, mi/hr 5

Temperature,  ̊C 30 Aeration HP 1,400

O2 Transfer Rate, lb/HP/hr 2.5

Tables 2 to 4 provide the characteristics of three example Aerated Stabilization Basins (ASB) 

used as model inputs in WATER9. Three different scenarios have been considered while 

generating the partitioning estimates for ASBs. The one-basin model treats the ASB as one wellstirred tank (Table 2). The two-basin model treats the first three-quarters of the WWTP as well 

stirred (with all the aeration HP) and the last quarter as a quiescent section (zero HP) (Table 3). 

The three-basin model treats the first 35% of the WWTP to be stirred with 50% of total HP, the 

next 40% to be stirred with the remaining 50% of total HP, and the last 25% to be quiescent 

(Table 4). The two-basin and three-basin models are perhaps better representations of actual 

WWTP operation. 

TABLE 2 CHARACTERISTICS OF AERATED STABILIZATION BASIN (ASB)

ONE BASIN MODEL

Flow, MGD 20 MLVSS, mg/L 100

Basin Volume, Gallons 160 x 106 Effluent TSS, mg/L 100

Basin Area, Acres 30 Effluent BOD5, mg/L 250

Basin Depth, ft 16.4 Wind Velocity, mi/hr 5

Temperature,  ̊C 30 Aeration HP 1,000

O2 Transfer Rate, lb/HP/hr 2.5
Issued 2012 4.A.3 

(Last Updated March 2012) 

ncasi

Pulp and Paper Mills 

TABLE 3 CHARACTERISTICS OF AERATED STABILIZATION BASIN (ASB)

TWO BASIN MODEL

Basin 1 Basin 2

Flow, MGD 20 20

Basin Volume, Gallons 120 x 106

40 x 106

Basin Area, Acres 22.5 7.5

Basin Depth, ft 16.4 16.4

Temperature,  ̊C 30 25

MLVSS, mg/L 100 50

Effluent TSS, mg/L 100

Effluent BOD5, mg/L 250

Wind Velocity, mi/hr 5 5

Aeration HP 1,000 0

O2 Transfer Rate, lb/HP/hr 2.5 --

TABLE 4 CHARACTERISTICS OF AERATED STABILIZATION BASIN (ASB)

THREE BASIN MODEL

Basin 1 Basin 2 Basin 3

Flow, MGD 20 20 20

Basin Volume, Gallons 56 x 106

64 x 10640 x 106

Basin Area, Acres 10.5 12.0 7.5

Basin Depth, ft 16.4 16.4 16.4

Temperature,  ̊C 30 30 25

MLVSS, mg/L 100 100 50

Effluent TSS, mg/L 100

Effluent BOD5, mg/L 250

Wind Velocity, mi/hr 5 5 5

Aeration HP 500 500 0

O2 Transfer Rate, lb/HP/hr 2.5 2.5 --

The WWTP characteristics provided in Tables 1 to 4 were used to predict typical partitioning of 

organic compounds in this handbook. It has been noted that the depth of the ASBs used in these 

examples is perhaps too high compared to most current operating systems while the total surface 

area and aeration horsepower used in these examples are perhaps too low compared with many 

currently operating systems. It is recommended that a mill use its own WWTP characteristics 

when running the WATER9 model in order to obtain site-specific estimates of partitioning for 

organic compounds. 
Issued 2012 4.A.4 

(Last Updated March 2012) 

ncasi

Pulp and Paper Mills 

2.0 ESTIMATING FATE OF ORGANIC COMPOUNDS IN SECONDARY WWTP 

USING WATER9

Fugitive emissions from secondary WWTP are a function of the WWTP characteristics, wind 

speed, and organic compound properties. Table 5 provides typical results obtained on the fate 

(volatilized, biodegraded or released) of organic compounds when applying the WATER9 model 

to predict organic compound partitioning in an example Aerated Stabilization Basin (ASB) and 

an Activated Sludge Treatment (AST) system. The characteristics of the ASB and AST used as 

model inputs are provided in Tables 1 through 4 and described in Section 1.3. As mentioned 

earlier, more recent site-specific data on the biodegradability of methanol in ASBs has been 

obtained from several “hard-piping” mills and this information is used to predict the fate of 

methanol in pulp mill ASBs (see chemical specific information sheets for methanol). It should 

be noted that in Table 5 the WWTP inlet concentration assumed is for calculation purposes only. 

It has does not reflect the actual inlet concentration of a WWTP. The partitioning fractions 

estimated using the model are more or less independent of the magnitude of the assumed inlet 

concentrations. 

3.0 ESTIMATING EMISSIONS FROM PRIMARY CLARIFIERS USING WATER9

Fugitive emissions from primary clarifiers are a function of the effluent flow rate, residence time, 

temperature, clarifier diameter, weir drop height, wind speed, and compound properties. 

Although WATER9 can estimate fugitive emissions from clarifiers, estimates have not been 

verified by field data and thus the reliability of the estimates is unknown at the present time. 

Table 6 provides estimates of fugitive emissions obtained by applying the WATER9 models to a 

175 ft diameter primary clarifier (12 ft depth, effluent temperature = 36 C, weir drop height = 

10 inches, wind speed = 5 miles/hr) receiving 11 MGD of pulp mill effluent. It should be noted 

that site-specific parameters for the clarifier have a significant influence on these estimates for 

many compounds. Thus, the use of site-specific parameters to run these models is 

recommended. 

4.0 ESTIMATING EMISSIONS FROM SURFACE IMPOUNDMENTS AND FLOWTHROUGH SETTLING PONDS 

Fugitive emissions from surface impoundments or flow-through settling basins are a function of 

the organic compound properties and site-specific parameters like effluent flow rate, residence 

time, temperature, exposed surface area, and wind speed. The characteristics of surface 

impoundments, settling basins, and lagoons vary widely from one facility to the other. This 

inherent variability limits the utility of estimates generated by applying WATER9 models to 

example systems. The use of site-specific parameters in these models would therefore be more 

appropriate. 
Issued 2012 4.A.5 

(Last Updated March 2012) 

ncasi

Pulp and Paper Mills 

REFERENCES 

National Council for Air and Stream Improvement, Inc. (NCASI). 1986. Simulation of organic 

compound removal in biological wastewater treatment process. Technical Bulletin No. 

511. Research Triangle Park, N.C.:National Council for Air and Stream Improvement, 

Inc. 

 . 1990. Field verification of the NCASI predictive model for organic compound removal 

by biological wastewater treatment processes. Technical Bulletin No. 582. Research 

Triangle Park, N.C.:National Council for Air and Stream Improvement, Inc. 

 . 1994a. Quantification of methanol biodegradation rate during biological treatment of 

kraft mill wastewaters. Unpublished NCASI Report. Research Triangle Park, 

N.C.:National Council for Air and Stream Improvement, Inc. 

 . 1994b. The effectiveness of biological treatment in removing acetone and MEK from 

kraft mill wastewaters. Unpublished NCASI Report. Research Triangle Park, 

N.C.:National Council for Air and Stream Improvement, Inc. 

 . 1996. Treatability of selected RCRA-regulated compounds in pulp and paper mill 

wastewater treatment plants. Technical Bulletin No. 724. Research Triangle Park, 

N.C.:National Council for Air and Stream Improvement, Inc. 

Environmental Protection Agency (U.S.). 1994. Air emissions models for waste and 

wastewater. EPA-453/R-94-080A. OAQPS, Research Triangle Park, NC:U.S. 

Environmental Protection Agency. 
Issued 2012 4.A.6 

(Last Updated March 2012) 

ncasi

Pulp and Paper Mills 

TABLE 5 WWTP PARTITIONING OF ORGANIC CHEMICALS USING TYPICAL WATER9 PREDICTIONS

Aerated Stabilization Basin (ASB)a, b

Activated Sludge Treatment 

(AST)a

One-Basin Two-Basin Three-Basin

Chemical Name

Assumed inlet 

conc., g/L

d

% 

volatilized

% 

biodegraded

% 

in effluent

% 

overall removal

% 

volatilized

% 

biodegraded

% 

in effluent

% 

overall removal

% 

volatilized

% 

biodegraded

% 

in effluent

% 

overall removal

% 

volatilized

% 

biodegraded

% 

in effluent

% 

overall removal

Acetaldehyde 100 18.5 67.3 14.2 85.8 21.9 67.1 11.0 89.0 23.9 70.5 5.6 94.4 8.6 84.2 7.2 92.8

Acrolein 10 10.6 80.1 9.3 90.7 12.9 81.2 5.9 94.1 13.9 83.8 2.3 97.7 4.5 91.3 4.2 95.8

Acrylonitrile 10 8.7 86.5 4.8 95.2 10.7 87.2 2.1 97.9 11.5 88.0 0.5 99.5 4.0 93.9 2.1 98.0

Benzene 10 36.2 61.9 1.9 98.1 42.8 56.7 0.5 99.5 45.1 54.8 0.1 99.9 24.2 74.9 0.9 99.1

Biphenyl 10 2.2 97.1 0.7 99.3 2.9 97.1 <<0.1 100.0 3.0 97.0 <<0.1 100.0 1.1 98.6 0.3 99.7

n-Butyl Alcohol 500 5.8 68.4 25.8 74.2 6.7 68.9 24.4 75.6 7.4 74.8 17.8 82.2 1.5 85.5 13.0 87.0

Carbon Disulfide 20 55.1 42.9 2.0 98.0 61.7 37.6 0.7 99.3 64.4 35.6 <<0.1 100.0 41.1 57.8 1.1 98.9

Chloroform 60 47.0 50.3 2.7 97.3 53.8 45.2 1.0 99.0 56.7 43.2 0.1 99.9 33.5 65.1 1.4 98.6

Cresol 40 <<0.1 99.7 0.3 99.7 <<0.1 100.0 0.0 100.0 <<0.1 100.0 0.0 100.0 <<0.1 99.9 0.1 99.9

Cumene 500 23.8 75.1 1.1 98.9 29.3 70.6 0.1 99.9 31.0 69.0 <<0.1 100.0 14.9 84.6 0.5 99.5

Dazomet 300 0.1 98.5 1.4 98.6 0.1 99.7 0.2 99.8 0.1 99.9 <<0.1 100.0 <<0.1 99.4 0.6 99.4

Ethylene Glycol 250 <<0.1 59.5 40.5 59.5 <<0.1 58.5 41.5 58.5 <<0.1 63.7 36.3 63.7 <<0.1 78.5 21.5 78.5

Carbitol 10 <<0.1 91.3 8.7 91.3 <<0.1 94.5 5.5 94.5 <<0.1 98.0 2.0 98.0 <<0.1 96.3 3.7 96.3

Methyl Carbitol 10 <<0.1 87.7 12.3 87.7 <<0.1 90.8 9.2 90.8 <<0.1 95.7 4.3 95.7 <<0.1 94.7 5.3 94.7

Butyl Carbitol 10 <<0.1 95.7 4.3 95.7 <<0.1 98.3 1.7 98.3 <<0.1 99.6 0.4 99.6 <<0.1 98.2 1.8 98.2

Cellosolve 10 0.8 79.6 19.6 80.4 0.9 81.7 17.4 82.6 1.0 87.9 11.1 88.9 0.2 90.8 9.0 91.0

Methyl Cellosolve 10 0.7 79.6 19.7 80.3 0.8 81.7 17.5 82.5 0.9 88.0 11.1 88.9 0.1 90.8 9.1 90.9

Butyl Cellosolve 10 <<0.1 92.7 7.3 92.7 <0.1 95.8 4.2 95.8 0.1 98.6 1.3 98.7 <<0.1 96.9 3.1 96.9

Formaldehyde 1800 0.2 85.4 14.4 85.6 0.3 88.3 11.4 88.6 0.3 93.7 6.0 94.0 <0.1 93.7 6.3 93.7
Issued 2012 4.A.7 

(Last Updated March 2012) 

ncasi

Pulp and Paper Mills 

TABLE 5 (Cont’d) WWTP PARTITIONING OF ORGANIC CHEMICALS USING TYPICAL WATER9 PREDICTIONS

Aerated Stabilization Basin (ASB)a, b

Activated Sludge Treatment 

(AST)a

One-Basin Two-Basin Three-Basin

Chemical Name

Assumed inlet 

conc., g/L

d

% 

volatilized

% 

biodegraded

% 

in effluent

% 

overall removal

% 

volatilized

% 

biodegraded

% 

in effluent

% 

overall removal

% 

volatilized

% 

biodegraded

% 

in effluent

% 

overall removal

% 

volatilized

% 

biodegraded

% 

in effluent

% 

overall removal

Methanolc1E05 5.0 95.0 <A 100.0 5.0 95.0 <A 100.0 5.0 95.0 <A 100.0 <0.1 99.7 0.2 99.7

Methyl Ethyl Ketone 150 19.8 66.4 13.8 86.2 23.5 65.8 10.7 89.3 25.9 68.8 5.3 94.7 10.3 82.8 6.9 93.1

Methyl Isobutyl Ketone 10 22.0 71.5 6.5 93.5 26.6 69.7 3.7 96.3 29.0 70.0 1.0 99.0 13.0 83.9 3.1 96.9

NABAM 10 <<0.1 43.5 56.5 43.5 <<0.1 41.2 58.8 41.2 <<0.1 44.1 55.9 44.1 <<0.1 65.7 34.3 65.7

Naphthalene 100 13.2 83.3 3.5 96.5 16.5 82.2 1.3 98.7 17.8 82.0 0.2 99.8 7.4 91.0 1.6 98.4

Phenol 50 <<0.1 99.7 0.3 99.7 <<0.1 100.0 0.0 100.0 <<0.1 100.0 0.0 100.0 <<0.1 99.9 0.1 99.9

Propionaldehyde 10 11.5 75.8 12.7 87.3 13.7 76.8 9.5 90.5 15.0 80.5 4.5 95.5 4.6 89.3 6.1 93.9

Styrene 10 78.0 16.0 6.0 94.0 81.5 13.8 4.7 95.3 86.0 12.9 1.0 99.0 69.8 26.2 4.0 96.0

Toluene 30 25.5 73.3 1.2 98.8 31.1 68.7 0.2 99.8 32.9 67.1 <<0.1 100.0 16.0 83.4 0.6 99.4

Vinyl Acetate 10 33.1 58.9 8.0 92.0 38.7 56.1 5.2 94.8 42.2 56.1 1.7 98.3 21.4 74.6 4.0 96.0

Xylene 300 27.1 71.3 1.7 98.3 32.8 66.8 0.4 99.6 34.8 65.1 0.1 99.9 17.1 82.1 0.8 99.2

a

 see Tables 1, 2 and 3

b The one-basin model treats the WWTP as one well-stirred tank. The two-basin model treats three quarters of the WWTP as well stirred (with all the 

aeration HP) and the last quarter as a quiescent section (zero HP). The three-basin model treats the first 35% of the WWTP to be stirred with 50% of total 

HP, the next 40% to be stirred with the remaining 50% of total HP, and the last 25% to be quiescent. The two-basin and three-basin models are perhaps 

better representations of actual WWTP operation. 

c

 see chemical-specific information sheets for methanol for more details 

d

the assumed inlet concentration shown here is for demonstration purposes only - it is not the actual inlet concentration in the WWTP. In fact, the 

partitioning fractions estimated here using the model should be more or less independent of the magnitude of the assumed inlet concentrations. 
Issued 2012 4.A.8 

(Last Updated March 2012) 

ncasi

Pulp and Paper Mills 

TABLE 6 WATER9 ESTIMATES OF FUGITIVE EMISSIONS 

FROM EXAMPLE PRIMARY CLARIFIER1

Chemical Name

% Volatilized

WATER9

Acetaldehyde 5.0

Acrolein 6.4

Benzene 9.5

Biphenyl 7.6

n-Butyl Alcohol 0.9

Carbon Disulfide 7.8

Chloroform 9.8

Cresol 0.1

Cumene 8.1

Dazomet 0.1

Ethylene Glycol <0.1

Carbitol <0.1

Methyl Carbitol <0.1

Butyl Carbitol <0.1

Cellosolve 0.1

Methyl Cellosolve 0.1

Butyl Cellosolve <0.1

Methanol 0.7

Formaldehyde <0.1

Methyl Ethyl Ketone 5.6

Methyl Isobutyl Ketone 7.5

NABAM <<0.1

Naphthalene 7.6

Phenol 0.1

Propionaldehyde 4.6

Styrene 8.9

Toluene 8.5

Xylene 9.2

1

 175 ft diameter primary clarifier (depth = 12 ft, effluent temperature = 36 C, 

weir drop height = 10 inches, wind speed = 5 miles/hr) receiving 11 MGD of pulp mill effluent