ZHANGZhuo-qun,YANGXi,LI Ye,et al.Monitoring and Analysis of Septic Tank Influent and Effluent Quality in Chongqing Urban Residential Communities[J].China Water & Wastewater,2023,39(11):82-89.
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Monitoring and Analysis of Septic Tank Influent and Effluent Quality in Chongqing Urban Residential Communities

China Water & Wastewater[ISSN:1000-4062/CN:12-1073/TU] volume: 第39卷 Number: 第11期 Page: 82-89 Column: Date of publication: 2023-06-01
Author(s):
ZHANG　Zhuo-qun1; 2;  YANG　Xi1; 3;  LI Ye1;  JIANG　Wen-chao1;  DONG　Xiao-xia4
（1. College of Environment and Ecology， Chongqing University， Chongqing 400045， China； 2. Jinan Municipal Engineering Design & Research Institute Co. Ltd.， Jinan 250003， China； 3. Sinopharm Chongqing Pharmaceutical and Medical Industry Design Institute Corporation， Chongqing 400042， China； 4. Chongqing Jiulongpo District Committee of House and Urban & Rural Development， Chongqing 400050， China）
Keywords:
septic tank;  residential community;  domestic sewage;  drainage system;  carbon to nitrogen ratio
Abstract:
To determine the characteristics of domestic sewage and clarify the potential impact of septic tank on the drainage system, the influent and effluent quality of septic tanks in four typical residential communities in downtown of Chongqing was monitored and analyzed. The average COD, BOD5, TN, TP and NH3-N in influent of septic tanks were 373.83 mg/L, 200.45 mg/L, 64.85 mg/L, 3.95 mg/L and 38.55 mg/L, respectively, and those in effluent were 224.93 mg/L, 152.22 mg/L, 57.16 mg/L, 3.63 mg/L and 34.47 mg/L, respectively, indicating that these indexes decreased by 39.83%, 24.06%, 11.86%, 8.10% and 10.58% respectively after the septic tank treatment. The average ratios of BOD5/TN, BOD5/TP, BOD5/COD in influent were 3.50, 64.78, 0.53, respectively, and those in effluent were 2.68, 42.58, 0.67, respectively, indicating that BOD5/TN ratio and BOD5/TP ratio decreased by 23.43% and 34.27%, and BOD5/COD ratio increased by 26.42% after the septic tank treatment. The highest proportion of influent BOD5/TN ratio greater than 4 was only 40%, indicating that the carbon to nitrogen ratio of raw water was generally lower than the requirement of biological nitrogen removal. The concentrations of organic matter were higher at 12:00-14:00 and 18:00-20:00, while TN, TP and NH3-N were higher at 07:00-09:00. Septic tank resulted in the decrease of BOD5/TN ratio to a certain extent, and might improve the degradation of organic matter in the drainage system. However, it also promoted water quality homogenization and reduced impact load.
Last Update: 2023-06-01