Applied Chemistry for Engineering (공업화학)

The Korean Society of Industrial and Engineering Chemistry (한국공업화학회)
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The Predilution Effect of Al-based Liquid Coagulants for the Optimal Efficacy

최적 응집 효율을 위한 Al계 액상 응집제의 희석 효과

  • Heo, Jae-Yong (Department of Chemical and Bio Engineering, Kyungwon University) ;
  • Lee, Sang-Wha (Department of Chemical and Bio Engineering, Kyungwon University)
  • 허재용 (경원대학교 화학생명공학과) ;
  • 이상화 (경원대학교 화학생명공학과)
  • Received : 2005.08.30
  • Accepted : 2005.12.06
  • Published : 2006.02.10
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Abstract

The coagulation efficacy of Al-based coagulants (such as Alum, PACS, and PACC) was investigated to ascertain removal efficiencies of turbidity and phosphate with variation of solution pH, coagulant dosages, and pre-dilution ratios. The efficacy of Al-based coagulants was maximized in the pH range of 6~9. Under the initial condition of pH 8, $10mg/L\;{PO_4}^{3-}$, and 20 NTU, Al-based coagulants exhibited a similar efficacy in the removal of turbidity, whereas the removal efficiency of phosphate was clearly dependent on the basicity of coagulants: Alum (0%) > PACS (45~50%) > PACC (70%). At high initial turbidity of 100 NTU, polymeric coagulants, such as PACS and PACC, exhibited a higher removal efficiency of turbidity compared to Alum. In comparison to direct injection of coagulants at low initial turbidity (20 NTU), 500~2000 times pre-diluted Alum, exhibited reduced coagulation efficacy; however, removal efficiencies of turbidity and phosphate increased with the increase of retention time. Pres-diluted PACC exhibited the enhanced coagulation efficacy followed by silght decrease of the removal efficiencies with increase of the retention time. At high initial turbidity of 100 NTU, pre-diluted Alum and PACC exhibited higher removal efficiencies of turbidity and phosphate.

원수의 pH, 응집제의 주입량, 희석배수에 따라 알루미늄계 응집제(Alum, PACS, PACC)의 원수내 인과 탁질의 제거효과를 고찰하였다. 저탁도(20 NUT) 및 적정 pH 6~9하에서 알류미늄계 응집제간의 탁도 제거율의 차이는 뚜렷하게 나타나지 않았다. 그러나 인의 제거율에 있어서는 20~40 ppm의 주입량에 대해서 응집제의 염기도가 증가할수록 감소함을 알 수 있었다. Alum (0%)>PACS (45~50%)>PACC (70%), 고탁도(100 NUT) 하에서는 고분자 응집제인 PACS와 PACC의 응집성능이 단분자 응집제인 Alum보다 뛰어남을 알 수 있었다. 20 NUT의 저탁도에서 직접 주입한 경우와 비교해서, 500~2000배로 희석한 Alum의 경우에는 응집효율의 감소가 나타났으나 희석된 응집제의 체류시간이 증가함에 따라 탁도 및 인의 제거율이 증가하는 경향을 나타내주었다. 반면에 희석된 PACC의 경우에는 분산도의 증가에 기인한 응집성능의 향상이 나타났으나 희석된 응집제의 체류시간이 증가함에 따라 응집효율의 감소가 나타났다. 100 NTU의 고탁도 조건하에서는 Alum과 PACC를 희석하여 주입시 모두 응집성능이 향상됨을 알 수 있었다.

Keywords

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