Weighted Coagulation with Glass and Diatomite for Storm Water Treatment and Sludge Disposal

Abstract

Biological municipal wastewater treatment can be adversely affected in combined sewage system by highly loaded storm water when the heavy rainfall events. To resolve the problem, a flexible treatment system is additionally required, and in this study, a rapid coagulation process was introduced: the treatment capacity in the system was maximized by weighted coagulant additives, sludge return, and lamellar plates in settling tank. Through the jar test, it was found that the weighted coagulant additives (WCA) primarily performed a role of seed for chemical floc in coagulation step, and sludge return was a predominant parameter to improve floc aggregation and its settling properties. In the pilot test, the weighted coagulation process removed suspended solids (SS), chemical oxygen demand (COD), and total phosphorus (T-P) at the highest of 95.4, 88.0, and 95.6%, respectively, in only 17 min (25 m³/m²/h). The chemical sludge produced from the system was effectively dewatered ranging from 55 to 74% of water content, and reutilized as a soil conditioner by heat treatment in the temperatures of 750 to 800°C. Conclusively, the weighted coagulation process could be proposed as one of the alternatives to economically treat the highly unsuitable loading from rainfall events in municipal wastewater treatment plant.