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Influence of Different Aeration Rates on Domestic Sewage Treatment in Purifying Tank Connecting Multiple Septic Tanks
  
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KeyWord:aeration rate; domestic sewage; purifying tank
Author NameAffiliation
WANG Chang Department of Marine Science & Engineering, Tianjin University of Science & Technology, Tianjin 300457, China 
WANG Ying Department of Marine Science & Engineering, Tianjin University of Science & Technology, Tianjin 300457, China 
YANG Xiao-jiao Department of Marine Science & Engineering, Tianjin University of Science & Technology, Tianjin 300457, China 
LI Lin Department of Marine Science & Engineering, Tianjin University of Science & Technology, Tianjin 300457, China 
TAN Yu-qin Wuxi Jinxin Group, Wuxi 214121, China 
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Abstract:
      One purifying tank for one septic tank is difficult to be implemented in rural area in China, owing to the cost. So it is necessary to develop one purifying tank for multiple septic tanks. In this study, an individual purifying tank was reformed to meet the treatment requirements for multiple septic tanks. The original process of two-stage anaerobic and one-stage aerobic digestion was changed into one-stage anaerobic and two-stage aerobic digestion. The ability of biological treatment for purification process was improved. For the new tank, sewage purifying capacity under different aeration intensities was investigated, and chemical oxygen demand(COD), five-day biochemical oxygen demand(BOD5), NH3-N and turbidity of effluent from different zones were measured. As aeration rates increased, the dissolved oxygen(DO) in the first aerobic and second aerobic zones increased rapidly at the beginning, then slowly, and finally rapidly again. The DO was 2.4 mg·L-1 and 3.1 mg·L-1 in the first and second aerobic zones respectively, at the aeration rate of 1.8 L·min-1. The values of COD, BOD5, NH3-N and turbidity of the effluent were 23 mg·L-1, 13 mg·L-1, 7.6 mg·L-1 and 9 NTU, respectively. However, further increasing aeration did not improve water quality much. The biodegradable substrates in the second aerobic zone were a major controlling factor due to low concentration. Therefore, the optimization of aerobic rates would be important for treating domestic sewage in purifying tank.