Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
Environ Sci Pollut Res Int. 2020 May;27(13):15674-15690. doi: 10.1007/s11356-020-08038-2. Epub 2020 Feb 20.
Rainfall can affect influent flow rate and compositions of wastewater, and thus further affect wastewater treatment performance and the effluent quality. This study aims to study the influence of rainfall on the environmental impacts of centralized wastewater treatment plants. The correlations between rainfall, and influent flow rate and compositions of wastewater in wet and dry seasons with two sewer systems, i.e. combined and separate sewer systems, were primarily established. Environmental impacts were assessed with life cycle assessment (LCA) to understand the temporal environmental burdens in wet and dry seasons. Functional units as per m treated wastewater (FU1) and as per kg PO-eq. removed (FU2), respectively, were used to evaluate impacts of wastewater treatment to the environment. Strong correlation between rainfall and the influent flow rate was found in the wastewater treatment plants with either a combined sewer system (with Pearson correlation coefficient r at 0.66) or a separate sewer system (with r at 0.84), where r represents the strength of the association between two variables. The rainfall effect is more obvious on the eutrophication potential and global warming potential than on other environmental indicators while sewer system, i.e. combined or separate, seems not important in the two cases studied. Both wastewater treatment plants (WWTPs) show a lower environmental burden in the wet season than in the dry season partially due to the dilution of wastewater by using FU1. The WWTP receiving high strength wastewater, however, demonstrates higher environmental impacts in the wet season by using FU2 than FU1, due to the less efficient treatment caused by heavy rainfall. Meanwhile, it is found that environmental impacts from the WWTP receiving low strength wastewater have no difference when using either FU1 or FU2. The results indicate that the environmental burdens particularly eutrophication and global warming caused by WWTPs are dependent on the correlations of rainfall intensity with wastewater quantity and quality instead of combined or separate sewer system. This could be used to guide a stricter control of eutrophication in a more sensitive season in more vulnerable receiving waters.
降雨会影响污水的流入速率和成分，从而进一步影响污水处理性能和出水质量。本研究旨在研究降雨对集中式污水处理厂环境影响的影响。主要建立了两个下水道系统（即合流制和分流制）在湿季和干季的降雨与污水流入速率和成分之间的相关性。通过生命周期评估（LCA）评估环境影响，以了解湿季和干季的时间环境负担。分别使用每处理废水立方米（FU1）和每去除公斤 PO-eq.（FU2）的功能单位来评估污水处理对环境的影响。在合流制或分流制下水道系统的污水处理厂中，发现降雨与流入速率之间存在很强的相关性（Pearson 相关系数 r 分别为 0.66 和 0.84），r 代表两个变量之间的关联强度。与其他环境指标相比，降雨对富营养化潜力和全球变暖潜力的影响更为明显，而下水道系统（即合流制或分流制）在这两种情况下似乎并不重要。两个污水处理厂（WWTP）在湿季的环境负担都低于干季，部分原因是使用 FU1 对污水进行了稀释。然而，接收高强度污水的 WWTP 在湿季使用 FU2 比 FU1 产生更高的环境影响，这是由于强降雨导致处理效率降低。同时，发现接收低强度污水的 WWTP 使用 FU1 或 FU2 时，环境影响没有差异。结果表明，污水处理厂造成的环境负担，特别是富营养化和全球变暖，取决于降雨强度与污水量和质量的相关性，而不是合流制或分流制下水道系统。这可以用来指导在更敏感的季节对更脆弱的受纳水体进行更严格的富营养化控制。
