AWWA ACE54320

Inactivation of microorganisms by chemical disinfectants is influenced by disinfection, microbial, and water quality factors. Water quality conditions such as pH, temperature, ionic strength, hardness, turbidity, and natural organic matter (NOM) as well as other constituents that exert a demand for the disinfectant can have a significant influence on the level of inactivation. Inorder to study the impact of water quality parameters (e.g. turbidity, NOM, pH), disinfection biossays were carried out in true-batch reactors (TBRs) with MS2 and Bacillus subtilis spores as microbial indicators and free chlorine as a disinfectant. Preliminary results obtained with chlorine show that temperature and pH have a pronounced effect on the inactivation of MS-2. The CT value required for comparable levels of inactivation is directly proportional to pH and inversely proportional to temperature. Similar results were observed while studying the inactivation of Bacillus subtilis spores with free chlorine. The CT value increased 2-3 times when temperature was lowered from 22 degrees C to 7 degrees C. It was also observed that Bacillus subtilis spores were approximately 700 times more resistant than MS-2. The results also showed that DOC exerts asignificant impact on the CT value while turbidity (induced with kaolin) had a negligible impact. Includes 10 references, tables, figures.