Composition and Abundance Changes of Invertebrates in Biological Activated Carbon (BAC) Filters

Biological Activated Carbon Filter (BACF) could provide ideal habitats for invertebrates, which may leads to aesthetic problems and adverse health effects on drinking water.The invertebrates in BACF in a water plant of south China have been studied from Sep. 2006 to Sep. 2007. 23 species (genera or group) of invertebrates were found. The Dominating organism group was rotifer , others included Copepoda, Cladocera, Oligochaeta, Nauplii and Nematoda. The average density of invertebrates in collected filtrate was 6.8 times as many as that in main ozonation water. After BAC filters were used for 13 months, the density of invertebrates in the filtrate, the carbon layer and the BACF collecting main increased by 3~17 times. There were abundant invertebrates in carbon layers, in which the maximum value up to 52645 ind./kg. Water temperature (WT) is a important factor of affecting the growth of invertebrates in BAC filters. These results indicate that a complex food chain may establishes and result in potential risk of invertebrates to the safety of drinking water in BAC filter.