Zeolite를 주입한 활성슬러지 공정에서, 열건조를 이용하여 잉여 슬러지내 포함된 zeolite의 재사용 가능성을 평가하였다. 실험결과, 잉여 슬러지내 zeolite의 NH4(+)-N 이온교환능에 대한 최적 재생온도 및 시간은 각각 500 ℃와 1시간으로 결정할 수 있었으며, 이 때 재생효율은 88%를 나타냈다. Zeolite를 주입한 반응기는 주입 zeolite에 따라 두 단계(I-새로운 zeolite 주입, II-재생 zeolite 주입)로 구분하며, 동일한 운전조건아래 표준 활성슬러지와 비교하였다. 이 때 폭기조내 zeolite농도를 4,000 mg/l로, 유입수의 평균 COD, T-N, T-P는 각각 150 mg/l, 40 mg/l, 3 mg/l 유지하였다. 이외에, 운전기간 88일과 96일(운전조건 II)에서 유입 NH4(+)-N 농도를 40 mg/l에서 각각 90 mg/l와 135 mg/l로 상승시키며 질산화효율을 관찰하였다. 실험결과, 용존 유기물과 달리 총 유기물 제거효율은 zeolite를 주입한 반응기가 표준 활성슬러지보다 평균 28% 더 높았는데, 이는 zeolite가 슬러지 침전성을 향상시켜 처리수 SS(Suspended Solids)농도가 2-12 mg/l로 향상되었기 때문이다. 한편, 표준 활성슬러지 반응기가 평균 58%의 질산화효율을 보인 반면, zeolite를 주입한 반응기에서 운전조건 I과 II에서 각각 74%와 76%의 높은 질산화효율이 관찰되었다. 질산화율, 미생물 농도, 질산화효율의 상관관계를 평가한 결과, 이는 zeolite 반응기내 고농도의 질산화균이 성장했기 때문이라고 판단할 수 있었다. 또한, 유입 NH4(+)-N농도를 90 mg/l와 135 mg/l로 상승시킨 결과, zeolite 반응기에서 표준 활성슬러지보다 16-20% 높은 질산화효율이 관찰되었고, 이로부터 재생된 zeolite를 주입한 반응기에서 높은 활성의 질산화 반응이 이루어짐을 확인할 수 있었다.

A feasibility of zeolite reuse by thermal treatment of excess sludge in zeolite added activated sludge(AS) was evaluated. Optimal regeneration conditions for NH4(+)-N ion exchange property of zeolite in excess sludge was decided at 500 ℃ of temperature for 1 h, which corresponded to 88% of regeneration efficiency. The reactor of zeolite dose, run in two models according to zeolite dosed(model I-original zeolite dose and model II-regenerated zeolite addition), was compared to conventional AS under equivalent operating condition. The concentration of zeolite in aerobic_x000D_ basin was maintained at 4,000 mg/l, and the average concentrations of COD, T-N and T-P in influent were 150 mg/l, 40 mg/l and 3 mg/l, respectively. Besides, influent NH4(+)-N concentration was increased from 40 mg/l to 90 mg/l and 135 mg/l, separately, in 88 d and 96 d of operating duration (model II). Though the removal efficiency in soluble organic compounds was similarly observed between two reactors, the removal efficiency of total organic compounds in AS of zeolite addition was improved by 28%, compared to conventional AS. The result was attributed that zeolite progressed sludge settling property followed by enhancing SS(Suspended Solids) concentration from 2 to 12 mg/l in effluent. While, AS reactor with zeolite addition averagely showed high nitrification efficiencies of 74% and 76% in model I and II, respectively, although conventional AS averagely revealed only 58% of nitrification efficiency. As a consequence of evaluating a mutual relationship among nitrification rate, microbial concentration and nitrification efficiency, the enhancing nitrification in AS of zeolite dose was ascribed to high concentration of nitrifying bacteria. In addition, at 90 mg/l and 135 mg/l of increased NH4(+)-N concentration, the reactor with zeolite application showed 16 to 20% of nitrification efficiency higher than that in conventional AS, and hereby it was validated that nitrification of high activity was accomplished in AS with regenerated zeolite dose.

Zeolite Regeneration Thermal Treatment Nitrification Activated Sludge

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