Background : Pending solids concentration and turbidity are the main drawbacks of waste water stabilization ponds used in hot climates for sewage treatment to reuse effluent. The effectiveness of chemical coagulation and lime addition in upgrading the ponds effluent quality is the purpose of this study.

Materials and Methods : The e ffects of three coagulants including Alum, Ferric sulfate, and Ferric chloride and Lime with variable dosages on suspended solid and turbidity were studied in Kashan University of Medical Sciences living compounds stabilization ponds during the summer 2005. Data were analyzed using Jar test.

Results: F erric sulfate 20 mg/l^�dosage reduced suspended soil concentration from 215 to 11.8 mg/ l^�and turbidity from 189 to 14.9 NTU (Nephelometric Turbidity Unit). Maximum TSS (Total Suspended Solid) and turbidity removal was 94.5 % and 92.1 %, respectively .

Conclusion: Chemical coagulation can efficiently upgrade the ponds effluent quality compared with Iranian organization of environmental health standards (TSS and turbidity less than 100 mg/l^�and 50 NTU).