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

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.

Automated summary

The study found that by determining the proper operation conditions, seasonal fluctuations in influent wastewater can be effectively managed; alum is the most effective coagulant, with the addition of polymer not leading to significant improvements in purification process; turbidity and percent ultraviolet transmittance show good correlation with TSS and ortho-P, suggesting their potential use as surrogates for micropollutants removal and online process control.