Comparison of invertebrate removal by traditional-BAC and pre-BAC treatment processes: verification in a full-scale drinking water treatment plant

Abstract

Invertebrate removal by traditional biological activated carbon (tra-BAC) and pre-BAC treatment processes was investigated in a full-scale water treatment plant. The results showed that invertebrate reproduction occurred in both BAC filters, but the invertebrate abundance in the finished water processed by tra-BAC was about 15 times greater than that processed using the pre-BAC process. In the pre-BAC process, the sand filter was placed after the BAC filter, and sand filtration removed most of the invertebrates, with an average removal efficiency of 91.1%. However, the pre-BAC filter, which was positioned behind the sedimentation tank, needed to be backwashed more frequently than the tra-BAC filter because of the high turbidity of the inlet water. The frequent backwashing reduced the biomass on the activated carbon and decreased the invertebrate reproductive rate. The results of this study are helpful for evaluating the pre-BAC treatment process in drinking water treatment plants.

Passability of Chironomid Larvae in Granular Activated Carbon

“…The problems associated with occurrence of invertebrates in drinking water have received increasing attention in recent years. The occurrence of visible invertebrates in tap water causes psychological discomfort to consumers and decreases consumer confidence in tap water quality [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. In addition, it can lead to indirect negative effects such as microbial regrowth [ 11 , 12 ].…”

“…The occurrence of visible invertebrates in tap water causes psychological discomfort to consumers and decreases consumer confidence in tap water quality [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. In addition, it can lead to indirect negative effects such as microbial regrowth [ 11 , 12 ]. In the case of benthic macroinvertebrates, most of these are eliminated during the filtration of the surface water, but it has been reported that some remain in the GAC or biological activated carbon (BAC) filter layer and can survive.…”

“…The presence of living macroinvertebrates in filters in water treatment plants has been reported worldwide. Copepoda, Rotatoria, and Diptera are the most common taxa in water treatment plants [ 9 , 12 , 13 , 16 , 17 , 18 ]. However, most previous studies have confirmed the presence of invertebrates in filters, and few studies have been conducted on the possibility of physical filtration of larvae in water treatment plants, along with their ecological aspects.…”