EFFECT OF SUSPENDED-SOLIDS ON WASTE-WATER DISINFECTION EFFICIENCY BY CHLORINE DIOXIDE

Effluents enriched with high suspended solids concentration were teste d for disinfection with chlorine dioxide. Following disinfection with various chlorine dioxide concentrations from 0 mg/l to 52.78 mg/l and contact times from 2 up to 24 h, half of the experimental samples were crushed (by Ultra-Turax) and tested for survival of indicator microor ganisms. The crushing process revealed that a certain fraction of indi cator microorganisms were left intact as a result of chlorine dioxide disinfection. This fraction was found to be able to regrow as was show n for all bacterial indicators, such as coliforms, fecal coliforms, en terococci and heterotrophic count, despite high disinfectant concentra tions. The study results indicate that some microorganisms fraction en trapped into suspended flocs can survive disinfection with chlorine di oxide, depending also on indicator type, therefore their prior removal by coagulation, sedimentation and filtration is a major prerequisite for successful disinfection.