Industrial and municipal loads of BOD5 and TSS estimated as million pounds per year for 1973 for the 48 States (see Table B-1 in Luken et al., 1976) for the National Commission on Water Quality.

Industrial Loads Influent and effluent loads for numerous industrial categories were estimated based on residual generation coefficients that defined industrial wastewater flow and residual loads per unit of product output or per unit of raw material processed. Industrial categories that accounted for the majority of process water use were investigated in greater detail (in-depth) than other categories (general). Industries evaluated in-depth included pulp and paper; petroleum refining; textiles; iron and steel; plastics and synthetics; organic chemicals; and inorganic chemicals. Effluent loads for the 1973 industrial inventory were based on removal efficiencies of BOD and TSS assigned for unit processes associated with primary, secondary, and tertiary industrial waste treatment. Total residual generation loads were reduced to total effluent discharge loads of 4,350 million lb BOD per year and 722,610 million lb TSS per year for all industrial categories.

Municipal Loads Population served in 1973 (ca. 156 million) by municipal wastewater treatment plants (24,209) is based on data obtained from the USEPA 1974 Needs Survey (USEPA, 1975). National municipal wastewater flow (~ 20,300 mgd; ~ 130 gpcd) was estimated as the sum of industrial flow reported to municipal facilities and population served multiplied by a constant 97.85 gpcd that accounted for residential, commercial, and institutional discharges. National influent loads were based on 1974 Needs Survey data where population served data were available for municipal facilities; otherwise, influent levels were assigned as follows: BOD5 = 200 mg/L; TSS = 230 mg/L; TN = 40 mg/L, and TP = 10 mg/L.

Estimates of national municipal effluent loads of 5,740 million lb BOD5 per year and 6,060 million lb TSS per year were based on removal efficiencies given in Luken et al. (1976) as:

Removal Effiency (%)

Type of Treatment BOD5 TSS TN TP

Conventional Treatment

Primary 33 52 10 9

Activated sludge 78.6 73 20 20

Trickling filter 78.6 68.2 20 10

Lagoon 78.6 68.2 20 10

Disinfection 0 0 0 0

Advanced Treatment

P removal 67 71 0 94

Nitrification 70 57 0 0

Nitrification and denitrification 0 0 90 0

Organics removal 60 60 0 20

Polishing lagoon 78.6 68 20 10

Carbon adsorption 50 72 0 50

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