Department of Civil, Structural and Environmental Engineering, Trinity College, Dublin 2, Ireland.
Water Sci Technol. 2011;64(3):677-83. doi: 10.2166/wst.2011.685.
The performance of six separate percolation areas was intensively monitored to ascertain the attenuation effects of unsaturated subsoils with respect to on-site wastewater effluent: three sites receiving septic tank effluent, the other three sites receiving secondary treated effluent. The development of a biomat across the percolation areas receiving secondary treated effluent was restricted on these sites compared to those sites receiving septic tank effluent. This created significant differences in terms of the hydraulic loading on the percolation areas with implications for the transport and attenuation of indicator microorganisms and nitrogen down through the subsoils and into the groundwater. The results of this work have formed a large input into the production of a new Code of Practice Wastewater Treatment and Disposal Systems Serving Single Houses. This has led to changes in the design of on-site hydraulic loading from 180 L per capita per day (L/c.d) down to 150 L/c.d. The range of acceptable subsoils receiving septic tank effluent has narrowed for more highly permeable subsoils following a series of tracer studies using bacteriophages. However, the range has been extended for lower permeability subsoils (range 0.08 down to 0.06 m/d) receiving secondary treated effluent in order to encourage the effluent to spread further along the trenches. The maximum individual length of percolation trenches receiving secondary effluent has also been reduced to 10 m to encourage dispersion on a wider area. This paper thus highlights how research can directly feed into a Code of Practice.
六个单独的渗滤区的性能得到了密集监测，以确定不饱和底土对现场废水排放的衰减效果：三个场地接收化粪池污水，另外三个场地接收二级处理污水。与接收化粪池污水的场地相比，接收二级处理污水的渗滤区的生物膜发展受到限制。这在渗滤区的水力负荷方面造成了显著差异，对指示微生物和氮通过底土向下运移和衰减以及进入地下水产生影响。这项工作的结果为制定新的《单户污水处理和处置系统实用规范》提供了大量投入。这导致现场水力负荷的设计从每人每天 180 升（L/c.d）降至 150 L/c.d。在使用噬菌体进行了一系列示踪研究之后，可接受的接收化粪池污水的底土范围已针对渗透性更高的底土缩小。然而，为了鼓励废水在沟渠中进一步扩散，接收二级处理污水的低渗透性底土（范围为 0.08 至 0.06 m/d）的范围已扩大。接收二级处理污水的渗滤沟的最大单个长度也已减少到 10 m，以鼓励在更大的区域内分散。因此，本文强调了研究如何直接纳入实用规范。
