Comparative Removal of Toxic Pollutants by Six Wastewater Treatment Processes

Five pilot-scale wastewater treatment processes that provided less than secondary treatment-primary clarification plus filtration, chemical clarification, high-rate trickling filter, aerated lagoon, and facultative lagoon-were evaluated for removal of priority pollutants from municipal wastewater. A conventional activated sludge system was operated in parallel as a control. Wastewater feed was spiked with 21 organics dissolved in toluene. Removal of ambient concentrations of five metals was also evaluated. The control typically removed 80 to 90% of volatiles and 85 to 95% of semivolatiles. The facultative lagoon was the best alternative process, followed by the aerated lagoon. Removals of a specific toxic pollutant depended on the properties of the chemical and its interactions with removal mechanisms used in each treatment process.