고농도 분말활성탄 첨가 침지식 막분리 바이오리액터에 의한 하수 2차 처리수 중의 유기물 처리특성
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This study focuses on the experimental investigation for residual organic removal by the powdered activated carbon coupled membrane bio-reactor (MBR). The study was conducted in three parts, such as analysis of organic matters of 2nd. sewage effluent, design and operation parameter evaluation and the organic removal characteristics in the system. The system consists of single reactor with high concentration PAC (80g/L) and submerged membrane module. The membrane used in the experiment was Polyethylene hollow fiber MF with nominal pore size of 0.1㎛ and filtration area, 0.02㎡ and 4㎡. Diffuser was installed under the membrane to supply oxygen and to prevent cake accumulation on the membrane surface. The organic concentration was 15.4~42.7 mgCODcr/L and 25.2~80.2 mgCODcr/L for the 2nd effluent of 3 sewage treatment plants and 3 domestic treatment plants, respectively. Around 50~75% of organic concentration was low molecular substance less than 500 dalton for the secondary effluents. The organics was removed more than 80% in biodegradability test in 2.4 hour contact. 74% was removed in the first 2 minutes by PAC adsorption. The saw dust PAC was estimated to be proper adsorbent for organics in the 2nd. effluent. Its Freundlish constant, K value was 5.847 and 1/n, 0.36. Design and operation parameters were obtained from the bench scale experiment, such as HRT of the bioreactor(2.5hour), PAC concentration (80g/L), the initial Flux (5.0 m/day) and intermittent suction cycle (12 min. suction and 3 min. idling). Organic removal by the system was high enough to produce a reclaimed water for domestic reuse. Organic concentration of the treated water was maintained at the level of 2mg/L in terms of TOC (around 5mg/L as CODcr). The high concentration of PAC was major parameter to keep stable organic removal and operation of the system. Substances of molecular weight less than 500 dalton were removed by the absorption and biodegradation in the system. On the other hand, those over 500 dalton were rejected at PAC cake layer on the membrane and gradually degraded by microorganisms during extended contact.