| This study was performed to examine the validity for the practical application of chemical precipitation treatment in D wastewater treatment plant. The content rate of Soluble COD/ Total COD was characteristically high in the influent and the current removal efficiencies of BOD, SS and COD by primary sedimentation and activated sludge process were 89%, 84% and 65% respectively. In jar test for the influent to the reservoir tank and the effluent from the aeration tank, alum generally showed the better removal efficiencies of COD, SS, turbidity and, especially T-P than FeCl₃, as compared on the basis of metal content, and there was no significant difference in the removal efficiency between Alum and PAC as compared on the basis of Al₂O₃ content. In pilot test for primary chemical treatment, using 120㎕/ℓ of chemical dosage, alum showed much enhanced removal efficiencies of BOD, SS and T-P but COD and T-N as compared with the removal efficiencies by current mechanical treatment. The levels of treated-water quality satisfied the permitted limit for discharge, but COD. In pilot test for the application of chemical precipitation treatment linked to the current activated sludge process, the removal efficiencies of BOD, COD and SS were not enhanced by the addition of alum for primary chemical treatment. The removal efficiency of T-P was significantly increased by the same treatment, but that of T-N was not effected. These results suggest that, to maximize the usefulness of the chemical upgrading technologies(CUT) in the wastewater treatment, we should consider many factors, such as the compositional variations and pollution degree of wastewater, the mixture of industrial and domestic sewage and the type of technologies in use. |
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