Coagulation and Disinfection Efficiency of an Electrochemically Prepared Dual-Function Reagent in Municipal Wastewater

Abstract

A novel dual-function chemical reagent was successfully prepared by electrolysis process. With high content of Al₁₃ species and active chlorine, the electrochemically prepared polyaluminum chlorine (E-PACl) as the dual-function chemical reagent presented the integrated properties of coagulation and disinfection in water treatment. The results obtained from jar tests in municipal wastewater and hydrolyzed Al (III) speciation distribution characterization confirmed that the Al₁₃ species was the most effective polymeric Al species in PACl responsible for coagulation. The solid-state ²⁷Al NMR spectra for precipitates revealed that the precipitates structure formed from Al coagulants with various pre-hydrolysis degrees were significantly different, and proved that the preformed Al₁₃ polymer is quite stable during the coagulation process. E-PACl performed well on both particulate and organic matter removals in municipal wastewater treatment. The higher the degree of pre-hydrolysis, the lower the efficiency of the coagulant removed phosphorus from water. The active chlorine in E-PACl was an effective disinfectant to inactivate fecal coliforms. When dosed 24 mg Al/L E-PACl, effective coagulation and disinfection in municipal wastewater could be achieved simultaneously. E-PACl may have a great potential to domestic use and small treatment plants for municipal wastewater reuse.

Key Words :

• Polyaluminum chloride
• Active chlorine
• Al₁₃ species
• Flocculation
• Water reuse

ACKNOWLEDGMENTS

The authors are grateful for financial support from the National Natural Science Foundation of China (50238050) and the National Science Fund for Distinguished Young Scholars (50225824).