| The novel BNR system, Advanced Step Aeration (ASA) system consisting of anoxic sludge tank, anaerobic, aerobic, anoxic, and aerobic tank in series with step feed was used for the study. Nutrient removals through ASA system were considerably excelent: at influent levels of T-N 40∼80㎎/ℓ, T-P 4.0∼8.0㎎/ℓ, respectively, removal efficiencies for T-N and T-P are 70∼85% and 90% and effluent level for T-N and T-P are 10∼15㎎/ℓ and 0.4∼0.6㎎/ℓ. Step-feeding raw wastewater to anaerobic and anoxic tank and using raw wastewater as external carbon source have brought about the improvement of denitrification capacity. Anoxic sludge tank minimized the nitrite and nitrate inhibition in the return activated sludge and maximized phosphorus release through the stable DO control. Experimental study of Pilot-plant scale has been performed with ASA system connected with Sand filter, GAC, and RO as wastewater reusing system. As the results of the batch test performance of ASA+Sand filter+GAC connecting with RO, Cl^-, COD, NH₄-N and PO₄-P were over 99% in all cases of 20bar, 30bar and 40bar. Especially, Cl^- level was shown with excellent removal rate of over 99%. It was sure that all the items had over 90% removal. 20bar selected in RO batch test was adopted to continuous test. The results have it that Cl^-, COD, NH₄-N, PO₄-P and Ca^(2+) except for turbidity were over 91%. Through the assessment of wastewater reuse, only the treatment by ASA+Sand filter or ASA+Sand filter+GAC system is applicable to toilet flushing or cleaning. Particularly, it is considered that ASA+Sand filter plus RO system is very effective as dyeing industy water which need high water quality. |
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