Chemically Enhanced Primary

Abstract

The Chemically enhanced process is considered to be a physicochemical technology for domestic wastewater treatment. The objective of this paper is to improve the efficiency of primary treatment processes and reducing the Hazardous Material and cost of the secondary treatment stage either by eliminating a biological treatment, where conditions and standards allow or by reducing the secondary treatment requirements. Analysis of physicochemical parameters as well as the treatment efficiency of aluminum sulfate (alum), ferric chloride (FeCl3), lime (CaO), and seawater was used. The effect of pH and the coagulant dosages were studied as well as mixing and settling time. Conditions were optimized according to the removal efficiencies measured in terms of reduction in the concentration of total suspended solids (TSS), biological oxygen demand (BOD5), and chemical oxygen demand (COD). The optimum COD removal % was achieved at a settling time of 20 minutes, while at pH~6, alum gave a high turbidity % removal of approximately 90% at the dose of 70 mg/l. FeCl3 gave a high turbidity % removal of approximately 95% at the dose of 40 mg/l. Turbidity removal and TSS removal gave a similar pattern at a settling time of 10-20 minutes, where best results were achieved. The results also showed that at pH~4, FeCl3 gave high COD% removal of approximately 90% at the dose of 40 mg/l. By studying the effect of stirrers’ speed (rpm), the results showed that an increase in the mixing intensity, above 80 rpm decreases the removals of COD, Turbidity and TSS when using alum as a coagulant.