Assessment of Endotoxin Removal from Reclaimed Wastewater Using Coagulation-Flocculation

Abstract

Following biological treatment, wastewater continues to have endotoxic active materials. However, because there is a trend of potable reuse and because endotoxic active materials potentially have harmful effects on human health, their removal from water is crucial. Lipopolysaccharide endotoxin has hydrophobic groups, and their removal using a coagulation-flocculation alternative is believed to be efficient. Thus, their removal from reclaimed wastewater using the coagulation-flocculation process was assessed. Secondary effluent samples from a wastewater treatment plant located in Sapporo, Japan, were investigated. It was found that this process gave satisfactory results in removing endotoxins, with an optimum removal rate of up to 40.5%. The endotoxin removal was maximized by adjusting the pH at the low range 4 - 5.5, with an aluminum sulfate dose of 80 mg/L. Further increases of the coagulant dose did not improve the removal efficiency. DOC and turbidity removal were at their optimum at higher pH range 5.5 - 6.5. Thus coagulation and flocculation could be considered as the first barrier and should be followed by other treatments to safely reuse reclaimed wastewater.