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USING OZONE INSTEAD OF CHLORINE IN A TYPICAL WATER TREATMENT PLANT IN EGYPT : A CASE STUDY

Ozone is now used as an oxidant and disinfectant in water treatment plants worldwide. Ozone is extremely faster and more powerful than chlorine in removing organic and inorganic matter, bacteria, viruses, pesticides, turbidity, odour, taste and color from potable water production. Some of these substances exist as by-products of using chlorine such as trihalomethanes in the treatment process. In this paper, the use of ozone instead of chlorine in water treatment plants and associated processes has been discussed. The advantages of using ozone as an oxidant and disinfectant in the pre-oxidation process are detailed. The Mansoura city main water treatment plant (a typical Egyptian plant) has been taken as a case study. The concentration time value (CT) for both chlorine and ozone for cryptosporidium inactivation is represented graphically and in correlation form. Results have shown that the most suitable point of ozone injection is the same that of pre-chlorination and the suitable ozone doze is 3 mg/l. For a higher Log credit value of 4, the CT value will be 10.54 (mg/l) min; the required contact time is only 3.54 min which is very small compared to that of chlorine (27 min). However, the operating cost of ozone is 23.5 % larger than that chlorine. The operating ozone concentration and exposure time makes it safe in handling.