Fractionation and Treatability Assessment of Phosphorus in Wastewater Effluents – Implications on Meeting Stringent Limits

Increasing demand to achieve very low effluent total phosphorus due to more stringent discharge limits have raised questions on the limits of technologies (LOT) and presented challenges of how to further the removal of phosphorus to extremely low levels (e.g 10 mg/L). This study presents and reviews the recent studies on the efficacy of different available treatment technologies and processes for removing different fractionation of phosphorus in the wastewater, and the treatability and susceptibility of various forms of phosphorus to different phosphorus removal technologies and mechanisms. Phosphorus speciation analysis in effluents from different treatment processes showed varying fractions and composition that seem to be associated with fundamental mechanisms of each processes. Effluent from chemical P removal process consists mainly of soluble reactive P and refractory organic P, while effluent from biological P removal process (EBPR) showed presence of soluble acid-hydrolysable polyP at nearly 20% in the effluent, in addition to the other two fractions. Advanced tertiary treatment process that have multiple stages and apply filtration, coagulation and adsorption, showed very efficient TP removal down to approximately 20 μg/L level. P speciation analysis of these tertiary effluents shows that dissolved (soluble) refractory organic P (rDOP) (0.01 to 0.07 mg/L) is the dominant component in all tertiary effluents studied and they are more resistant to available treatment processes. On-site short-term bench scale and pilot-scale adsorption column tests were conducted to investigate the potential of applying different adsorptive media to further remove phosphorus in secondary and tertiary effluent to levels lower than the current limits of technologies in practice. The results demonstrated that the adsorption column process can effectively remove soluble non-reactive P (include rDOP) in the wastewater down to