Microbiologic characterization of filter backwash water and assessment of some recycling scenarios

Abstract

The objective of the study was to characterize filter backwash water considering the turbity and microorganisms (Escherichia coli, Bacillus subtilis, Clostridium perfringens, Giardia spp. e Cryptosporidium spp.) and to analyze some possible recycling scenarios as a way of planning this operation with views to minimize health risks. Regarding the parameters analyzed in the clarification process, the best results were obtained when cationic polymer was used in comparison with other situations. The presence of resistant organisms in filter backwash water, even after clarification process, indicates the need of greater attention when considering recycling situation in water treatment plants. The results suggest that the clarification contributes to reduce the risks associated to filter backwash recycling. The best results found in the clarification processes suggest the use of the cationic polymer resulting in considerable reduction of organisms and consequent reduction of associated risks.