IMPACT OF POND-TYPE TREATMENT PROCESSES IN REDUCING BOTH AVERAGE AND PEAK CONCENTRATIONS OF DISSOLVED AND TOTAL RECOVERABLE PRIORITY POLLUTANT METALS

Ten priority pollutant metals, both total recoverable and dissolved, were monitored in untreated municipal wastewater, aerated pond secondary effluent, and maturation pond effluent to determine the impact of pond treatment on effluent average and peak concentrations. Concentrations were monitored to trace levels using “clean techniques,” on a biweekly basis for a one-year period. The aerated pond treatment process exhibited statistically significant reductions in the average total recoverable concentrations of aluminum, cadmium, chromium, copper, mercury, nickel, lead, and zinc. The aerated pond treatment process also exhibited statistically significant reductions in the average dissolved concentrations of aluminum, cadmium, chromium, copper, mercury, and lead. The maturation pond process received aerated pond effluent for additional priority pollutant “polishing.” The maturation pond process exhibited further, statistically significant, reductions in average total recoverable concentrations of aluminum, cadmium, chromium, copper, mercury, lead, and zinc. The maturation pond process also exhibited further, statistically significant, reductions in the average dissolved concentrations of aluminum, copper, lead, and zinc. This research did not investigate the pathways associated with removal of metallic contaminants. The pond processes were also observed to reduce the peak concentrations of most of the contaminants, presumably because increasing the hydraulic detention time of a process will lead to internal process contaminant equalization (i.e., reduction of variance) and thus a reduction in peak contaminant concentrations.