Bench to full-scale enhanced primary treatment of municipal wastewater under wet weather flow for minimized pollution load: evaluation of chemical addition and process control indicators

Abstract

The enhanced primary treatment of municipal primary influent under wet weather conditions was studied through a comprehensive approach from bench to full scale. The study delivered a practical solution for managing seasonal fluctuations in the influent wastewater by determining the most effective operation conditions for coagulation–flocculation. Three metal-based coagulants were tested through a series of jar tests. Alum outperformed other coagulants since 1 mg of Al added as alum with low mixing was able to remove 22 NTU, 19 mg COD, and 0.8 mg ortho-P. Three-factor analysis of variance (ANOVA) indicated that total suspended solids (TSS) removal depended mostly on rapid mixing while chemical oxygen demand (COD) and ortho-P removals depended on slow mixing and coagulant dose. In bench and full-scale operations, the addition of polymer did not lead to any pronounced improvements. Finally, turbidity and percent ultraviolet transmittance showed good correlation with TSS and ortho-P, which evokes their use as surrogates for micropollutants removal and online process control.