High Pollution treatment necessities were aimed at on COD basis (8000 mg/l). Case studies include the treatability study, conceptual design and monitoring of the actual treatment plant performance. To reach a pretreatment standard value of 800 mg/l COD, chemical and biological treatment were necessary including chromium removal and sulfide oxidation. Results of the treatability tests indicate that chemical coagulation is efficient and reliable in terms of COD removal. However, materials used in the process such as sulfuric acid and sodium sulfate and adding of manganese sulfate as catalyst for sulfide oxidation increase the sulfate concentrations in the influent of the biological treatment In this case, lime was used for coagulation both to reach sulfate standard and to protect the biological system.