Enhancement of Phosphorus Removal in a Polyurethane Compressible Media Filtration System with Coagulation

抄録

Reclaimed water for stream augmentation or landscape impound requires low phosphorus contents to avoid eutrophication. A synthetic compressible media filtration system was previously developed for the purpose of wastewater reclamation. However, the filtration system was limited for removal of soluble matters in secondary treated wastewater, such as phosphorus. The objective of this study is to evaluate the optimum coagulation conditions for removal of phosphorus in effluent from a wastewater treatment plant (WWTP) using the filtration system combined with coagulation. Coagulation conditions including selection of coagulant, coagulant dose, mixing conditions were determined through jar-test. Also a field-test with the coagulation–filtration system was conducted to evaluated operation factors such as compression rate of media and periodic backwash. Polyaluminum chloride (PAC) demonstrated the best performance in terms of total phosphorus (TP) removal efficiency and stability of pH among coagulant used in this experiment. Since the change in mixing conditions had little effect on TP removal, in-line coagulant supplying could be feasible for the coagulation–filtration system. Increasing the compression rate of the filter media from 0 to 50% increased the TP removal efficiency within only 10%. This made great changes in the filtration pressure and the flow rate, which is related to operating cost of the system, simultaneously. Compared to the filtration system with no addition of coagulation, the addition of coagulant enhanced the removal of phosphorus along with turbidity, but decreased the operation time between each backwashing cycle. One needs to consider the various operation parameters examined in this study as well as the requirement of phosphorus removal, when operating the coagulation–filtration system. Consequently, the coagulation–filtration system, which requires a small area, can effectively reduce the phosphorus contents of WWTP effluent, and make it suitable for reuse purposes.