USE OF MONTE-CARLO TECHNIQUES TO ASSESS POTW COMPLIANCE WITH EPA WATER-QUALITY CRITERIA FOR HEAVY-METALS

This paper presents the results of a study (Larry Walker Associates, 1 990) to determine the nature of additional controls necessary for the Sacramento Regional Wastewater Treatment Plant (Regional Plant) to com ply with the numeric water quality objectives for metals recently adop ted by the State of California. In addition, the impact of Regional Pl ant effluent on Sacramento River metals concentrations is examined, an d the costs of compliance with the new objectives are estimated. Monte Carlo techniques are used to determine the ability of the Regional Pl ant to achieve the metals objectives and the effects of treatment plan t discharge on receiving water metal concentrations. Frequency distrib utions of advanced treatment efficiencies, such as lime precipitation and reverse osmosis, are used to simulate effluent concentration reduc tions that are potentially achievable. The costs associated with the a dditional treatment required to meet objectives are estimated using pu blished cost estimates for advanced treatment plants of similar size. Results show that currently, the Regional Plant does not meet objectiv es for cadmium, copper, mercury, and zinc. Furthermore, the additional treatments evaluated would not completely eliminate violations of the copper and mercury objectives.