Seham, M. Shash1, Ahmad, Z. Al-Herrawy2, Mohammed, M. Kamel2 and Hamdy, A.El-Sadik3
1 Department of Botany, Faculty of Science, Benha University, Benha, 2 Water Pollution Research Department, National Research Center (NRC), 3 Water and Wastewater Regulatory Agency (EWRA), Egypt.
The principal factors that influence disinfection efficiency are disinfectant concentration, contact time, temperature and pH. The main objective of this study was to use chlorine gas for inactivation of four bacterial strains isolated from inlets of some drinking water treatment plants in Sharkyia governorate. The bacterial isolates were identified up to species level after being submitted to morpho- physiological as well as biochemical tests and confirmed by using BIOLOG GN III. The results revealed that the removal percentages of Escherichia coli O157:H7, Staphylococcus epidermis, Pseudomonas aeruginosa and Bacillus subtilis were 99.98, 100, 99.92 and 98.83% respectively, after 10 min contact time. The breakpoints of E. coli O157:H7, Staphylococcus epidermis, Pseudomonas aeruginosa and Bacillus subtilis were observed at chlorine doses 1, 2.2, 1.4 and 0.6 mg/L, respectively. Consequently, Staphylococcus epidermis and E. coli O157:H7 showed more resistant to chlorination than Pseudomonas aeruginosa and Bacillus subtilis.
Key words: disinfection, bacteria, chlorination, breakpoint, Nile water.