Journal of Korean Society of Water and Wastewater (상하수도학회지)

The Korean Society of Water and Wastewater (대한상하수도학회)
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Study to enhance the settleability of deep aeration tank MLSS (Mixed Liquor Suspended Solid) by air sparging

탈기에 의한 심층포기 호기조 MLSS (Mixed Liquor Suspended Solid) 침전성 향상 방안 연구

  • Jisoo Han (Department of Environmental Energy Engineering, Graduate School, Kyonggi University) ;
  • Jeseung Lee (Department of Environmental Energy Engineering, Graduate School, Kyonggi University) ;
  • Byonghi Lee (Department of Civil & Energy System Engineering, Kyonggi University)
  • 한지수 (경기대학교 대학원 환경에너지공학과) ;
  • 이제승 (경기대학교 대학원 환경에너지공학과) ;
  • 이병희 (경기대학교 사회에너지시스템공학과)
  • Received : 2024.03.26
  • Accepted : 2024.05.16
  • Published : 2024.06.15
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Abstract

The dissolved air at the bottom layer of the deep aeration tank transforms into fine gas bubbles within the MLSS (Mixed Liquor Suspended Solid) floc when exposed to the atmosphere. MLSS floc flotation occurs when MLSS from the deep aeration tank enters the secondary clarifier for solid-liquid separation, as dissolved air becomes fine air within the MLSS floc. The floated MLSS floc causes a high SS (Suspended Solid) concentration in the secondary effluent. The fine air bubbles within the MLSS floc must be removed to achieve stable sedimentation in the secondary clarifier. Fine bubbles within the MLSS floc can be removed by air sparging. The settleability of MLSS was measured by sludge volume indexes (SVIs) after air sparging MLSS taken at the end of the deep aeration tank. MLSS settling tests were performed at MLSS heights of 200, 300, 400, and 500 mm, and compressed air was fed at the bottom of the settling column with air flow rates of 100, 300, and 500 ml/min at each MLSS height, respectively. Also, at each height and air flow rate, air was sparged for 3, 5, and 7 minutes, respectively. SVI was determined for each height, air flow rate, and sparging time, respectively. Experimental results showed that a 300 mm MLSS height, 300 ml/min air flow rate, and 3 minutes of sparging time were the least conditions to achieve less than 120 ml/g of SVI, which was the criterion for good MLSS settling in the secondary clarifier.

Keywords

Acknowledgement

본 연구에 도움을 주신 수도권 J하수처리장 소장님과 관련 직원들, 그리고 (주) 유신 정승철 대리님께 감사를 표합니다.

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