Estimation of septic tank setback distances based on transport of E. coli and F-RNA phages.
Estimation of septic tank setback distances based on transport of E. coli and F-RNA phages.
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DOI：
10.1016/s0160-4120(03)00054-0
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发表时间：
2004
影响因子：
11.8
通讯作者：
L. Pang;M. Close;M. Goltz;L. Sinton;H. Davies;C. Hall;G. Stanton
中科院分区：
文献类型：
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作者：
L. Pang;M. Close;M. Goltz;L. Sinton;H. Davies;C. Hall;G. Stanton
新西兰Okareka湖的化粪池系统和海岸线之间的后退距离是根据最坏情况下的模型模拟确定的，使用现场测量的最高水力传导率和梯度，微生物指标的去除率（大肠杆菌和F-RNA大肠杆菌）从柱实验确定，和最大值的设计标准的处置系统，假设没有不饱和带，从失效或不符合要求的处理系统中连续排放未经处理的污水（两种指标的浓度均为1× 107个/100 ml）进入地下水，含水层中没有病原体吸附。模拟结果表明，最小后退距离为16米，以满足新西兰Recommendation水质指南为E。大肠杆菌<126/100毫升（环境部，1999年）和48米，以满足2000年新西兰饮用水标准，肠病毒<1/100升（卫生部，2000年）。这些距离可能适用于地下水流速<7米/天的浮石砂含水层中的其他湖岸。实验室柱和批实验的结果提供了一个深入了解微生物衰减和迁移过程中的浮石砂含水层。细菌去除主要通过过滤（87-88%），部分通过死亡（12-13%），而病毒去除通过死亡（45%）和过滤（55%）。此外，没有含水层物质的地下水中微生物的死亡（即，游离微生物）远低于具有含水层物质的地下水中的死亡（即，吸附的微生物），并且仅占总去除量的2-6%。这意味着，在实验室中确定的游离微生物的死亡率估计的后退距离，而不考虑含水层介质和其他去除过程，这是经常在文献中报道，可能会大于必要的。
Setback distances between septic tank systems and the shorelines of Lake Okareka, New Zealand were determined from model simulations for a worst-case scenario, using the highest hydraulic conductivity and gradient measured in the field, removal rates of the microbial indicators (Escherichia coli and F-RNA phages) determined from a column experiment, and maximum values of the design criteria for the disposal system, and assuming an absence of an unsaturated zone, a continuous discharge of the raw effluent from a failed or non-complying treatment system (both indicators at concentrations of 1×107counts/100 ml) into the groundwater and no sorption of pathogens in the aquifer. Modelling results suggest that the minimal setback distances were 16 m to satisfy the New Zealand Recreational Water Quality Guidelines for E. coli <126 per 100 ml (Ministry for the Environment, 1999) and 48 m to meet the Drinking-Water Standards for New Zealand 2000 for enteric virus <1 per 100 l (Ministry of Health, 2000). These distances may be applicable for other lakeshores in pumice sand aquifers with groundwater velocities <7 m/day. Findings of laboratory column and batch experiments provided an insight into the microbial attenuation and transport processes in pumice sand aquifers. Bacterial removal was predominately through filtration (87–88%) and partially by die-off (12–13%), while viral removal was by both die-off (45%) and filtration (55%). In addition, microbial die-off in groundwater without aquifer material (i.e., free microbes) was much lower than die-off in groundwater with aquifer material (i.e., sorbed microbes) and contributed only 2–6% to the total removal. This implies that the setback distances estimated from die-off rates for the free microbes, determined in the laboratory without considering aquifer media and other removal processes, which are often reported in the literature, could be larger than necessary.