Water quality is of a great importance for every being. Because of its importance, the present work is planned to evaluate water quality in the WTPs, survey WTPs? quality focusing on the study of the differences among the different WTPs, and study the effect of the WTP?s design on the water quality and the effect of water treatment on the health. For this reason, 3 different WTPs were chosen from Damietta Governorate. These WTPs were chosen on the basis of their design differences.To achieve our aim, control fish were collected from a private fish farm in El- Manzalah Lake representing control group In conclusion 1- There are significant differences and improvement in water quality between before and after treatment, these show the role of the WTPs in removing or reducing turbidity, bacteria and some heavy metals not all.2-In the same time, biochemical and histological analyses of Oreochromis niloticus were done.