Migration and Control of Invertebrates in Waterworks with Advanced Treatment

Abstract

The migration of invertebrates at each step of the treatment process in four waterworks with advanced treatment in eastern China was investigated for the first time. Raw water quality and water temperature had a strong effect on invertebrate abundance and species. A combination of sedimentation with pretreatment, ozonation, and disinfection was able to remove or inactivate the invertebrates. Enhanced sand filtration combined with chlorine or micro-coagulation effectively promoted the removal of invertebrates by filtration. Invertebrates colonized both down-flow and up-flow biological activated carbon (BAC) filters; thus, fixation of a BAC filter as the penultimate process before disinfection was inadequate. The addition of a persistent disinfectant before the clear water tank and regular flushing and washing of the clear water tank were essential. The total abundance of invertebrates in the clear water tank could be as high as 13–14 ind./m3; rotifers and nematodes were the dominant species and accounted for 85.9–1% of total invertebrates. As a result, future studies should focus on the removal and control of rotifers and nematodes in waterworks.