PREDICTION OF POLLUTANT DISTRIBUTION IN ESTUARIES

Abstract

A method was developed for predicting the distribution of sewage constituents which would result from a proposed sewage outfall in estuaries or coastal seas. The method is based on the mathematical relationship between the solutions of the mass-balance equations with and without a decay term and on the assumption that both the dispersion and decaying processes are linear, acting independently. The application of the method requires dye dispersion experiments and a numerical model employing the results of the experiments. This approach makes it possible to predict the concentration field of sewage constituents with differing decay rates by using tracer release experiment employing a conservative tracer. The method has been applied to assess the environmental impact of a proposed sewage outfall in Hampton Roads, Virginia. Two dye dispersion experiments were performed, one a continuous release over a flood tide cycle and the other over an ebb tide cycle. Horizontal distributions of dye were measured at subsequent slack waters before flood and ebb. The results were used to predict the concentration fields of total nitrogen, total phosphorus, coliform bacteria, biochemical oxygen demand, dissolved oxygen deficit and chlorine residuals, which would result from the proposed sewage outfall.