BOD Mass Balance and Water Quality Standards

To establish appropriate water quality controls, the magnitude of the gross pollution load of a basin should be known. Usually it is not. Mathematical modeling of basinwide BOD relationships can be greatly facilitated by applying known equations on a basis of BOD mass loading rather than of BOD concentration. The necessary hydrologic basis includes travel time dye tests, data as to slopes and distances, and computation of travel times for all parts of the basin at various stages. Treatment plant and instream BOD records are essential. The basic BOD removal parameter must be computed and adjusted for different conditions. The remaining computations require a computer but are not especially difficult. The principal reservation as to accuracy of the results consists of the allowance that must be made for nitrogenous BOD. Applications of this method to three New Jersey basins indicate that in each case the recorded BOD data from treatment plants account for less than half of the total pollution loading entering the stream. The policy implication is that it is inappropriate to plan water quality standards and programs of corrective measures on the assumption that recorded effluents constitute the only major source of pollution.