Effluent Particulate Phosphorus Fractionation and Coagulation by Optimized Chemical Dosing

The objective of this research was to characterize the dissolved particulate matter (ie, less than 0.45 μm) in final effluent (FE) from a biological nutrient removal (BNR) wastewater treatment plant (WWTP) and to measure the efficacy of poly aluminum chloride (PACL) in combination with polyepiamine for coagulating dissolved phosphorus. As a follow-up to the lab characterization, coagulant dosing at a full-scale WWTP was conducted to test the applicability of the lab results and characterize the removal of micro-pollutants. The lab characterization shows that a significant proportion of the FE non-reactive dissolved phosphorus consists of colloidal particles, less than 0.10 μm in size. Ultrafiltration characterization further suggests that the dissolved colloidal phosphorus may be bound up with fulvic and humic substances. Batch testing showed that PACL and polyepiamine were effective at precipitating dissolved phosphorus and that removal could be correlated to zeta potential measurements. However, during full-scale coagulant dosing trials, the relationship between zeta potential and phosphorus removal was less clear.