Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, 12489, Berlin, Germany.
Environ Sci Pollut Res Int. 2021 Dec;28(45):63878-63893. doi: 10.1007/s11356-021-12440-9. Epub 2021 Jan 26.
A growing literature indicates that untreated wastewater from leaky sewers stands among major sources of pollution to water resources of urban systems. Despite that, the quantification and allocation of sewer exfiltration are often restricted to major pipe areas where inspection data are available. In large-scale urban models, the emission from sewer exfiltration is either neglected (particularly from private sewers) or represented by simplified fixed values, and as such its contribution to the overall urban emission remains questionable. This study proposes an extended model framework which incorporates sewer exfiltration pathway in the catchment model for a better justified pollution control and management of urban systems at a nationwide scale. Nutrient emission from urban areas is quantified by means of the Modelling of Nutrient Emissions in River Systems (MONERIS) model. Exfiltration is estimated for public and private sewers of different age groups in Germany using the verified methods at local to city scales, upscaling techniques, and expert knowledge. Results of this study suggest that the average exfiltration rate is likely to be less than 0.01 L/s per km, corresponding to approximately 1 mm/m/year of wastewater discharge to groundwater. Considering the source and age factors, the highest rate of exfiltration is defined in regions with significant proportions of public sewers older than 40 years. In regions where public sewers are mostly built after 1981, the leakage from private sewers can be up two times higher than such from public sewers. Overall, sewer exfiltration accounts for 9.8% and 17.2% of nitrate and phosphate loads from urban systems emitted to the environment, which increases to 11.2% and 19.5% in the case of no remediation scenario of projected defective sewer increases due to ageing effects. Our results provide a first harmonized quantification of potential leakage losses in urban wastewater systems at the nationwide scale and reveal the importance of rehabilitation planning of ageing sewer pipes in public and private sewer systems. The proposed model framework, which incorporates important factors for urban sewer managers, will allow further targeting the important data need for validating the approach at the regional and local scales in order to support better strategies for the long-term nutrient pollution control of large urban wastewater systems.
越来越多的文献表明，渗漏污水未处理的废水是城市系统水资源的主要污染源之一。尽管如此，下水道渗出物的量化和分配通常仅限于有检查数据的主要管道区域。在大规模城市模型中，下水道渗出物的排放要么被忽略（特别是来自私人下水道），要么用简化的固定值来表示，因此其对城市总排放量的贡献仍然存在疑问。本研究提出了一个扩展的模型框架，该框架将下水道渗出物路径纳入集水区模型，以便更好地在全国范围内对城市系统进行污染控制和管理。通过河流系统营养物排放模型（MONERIS）模型来量化城市地区的营养物排放。使用在当地到城市规模上经过验证的方法、上推技术和专家知识，对德国不同年龄组的公共和私人下水道的渗出物进行了估计。本研究结果表明，平均渗出率可能小于 0.01 升/秒/公里，相当于每年约有 1 毫米/米/年的废水排入地下水。考虑到来源和年龄因素，在公共下水道中有相当比例的下水道超过 40 年的地区，渗出率最高。在公共下水道主要建于 1981 年以后的地区，私人下水道的泄漏量可能比公共下水道高两倍。总的来说，下水道渗出物占城市系统排放到环境中的硝酸盐和磷酸盐负荷的 9.8%和 17.2%，如果不修复由于老化效应而预计增加的有缺陷下水道，则增加到 11.2%和 19.5%。我们的研究结果首次在全国范围内对城市污水系统的潜在泄漏损失进行了协调一致的量化，并揭示了公共和私人下水道系统中老化下水道管道修复规划的重要性。该模型框架纳入了城市下水道管理者的重要因素，将允许进一步针对区域和地方尺度验证方法的重要数据需求，以支持对大型城市污水系统的长期营养物污染控制的更好策略。
