The Water Institute at UNC, Department of Environmental Sciences and Engineering, The Gillings School of Global Public Health, University of North Carolina at Chapel Hill, 4114 McGavran Hall, Campus Box # 7431, NC, 27599, Chapel Hill, NC, USA; Department of Construction Economics and Management, College of Engineering, Design, Art and Technology (CEDAT), Makerere University, P.O. Box 7062, Kampala, Uganda.
The Water Institute at UNC, Department of Environmental Sciences and Engineering, The Gillings School of Global Public Health, University of North Carolina at Chapel Hill, 4114 McGavran Hall, Campus Box # 7431, NC, 27599, Chapel Hill, NC, USA.
Int J Hyg Environ Health. 2022 Jun;243:113987. doi: 10.1016/j.ijheh.2022.113987. Epub 2022 May 25.
Sanitation is intended to reduce the spread and burden of diseases transmitted from excreta. Pathogen reduction from excreta before sludge or effluent discharge to the environment would seem a logical and useful performance indicator for sanitation systems. However, the relative magnitudes of pathogen release from common sanitation technologies are not well understood. We, therefore, investigated the feasibility of performance measurement of different sanitation technologies in Tamil Nadu, India in reducing the release of the pathogen indicator Escherichia coli (E. coli). After conducting users' surveys and technical assessments of the locally prevalent sanitation systems, we classified them into 7 distinct categories (based on both observed physical characteristic and usage) within a widely-accepted physical typology. Faecal sludge and wastewater samples were collected and analysed for E. coli and total solids from 136 household systems, 24 community systems, and 23 sanitary sewer oveflows. We estimated the average volumetric release rates of wastewater and faecal sludge from the different sanitation technologies. Average daily per capita E. coli release was computed, and used as one indicator of the public health performance of technologies. We found that on-site installations described by owners as "septic systems" included diverse forms of tanks and pits of uncertain performance. We observed a statistically significant difference in the average daily per capita E. coli release from different sanitation technologies (p = 0.00001). Pathogen release from the studied on-site sanitation technologies varied by as much as 5 orders of magnitude from "lined pits" (5.4 Log10 E. coli per person per day) to "overflowing sanitary sewers" and "direct discharge pipes" (10.3-10.5 Log10 E. coli per person per day). Other technologies lay between these extremes, and their performances in E. coli removal also varied significantly, in both statistical and practical terms. Our results suggest that although faecal sludge management along the sanitation service chain is important, sanitation planners of the observed systems (and probably elsewhere) should direct higher priority to proper management of the liquid effluents from these systems to minimize public health hazards. We conclude that (i) the work demonstrates a new and promising approach for estimating the public health performance of differing sanitation technologies, (ii) if E.coli is accepted as an indicator of the public health hazard of releases from sanitation systems, our results strongly suggest that safe containment of excreta for an extended period substantially reduces pathogen numbers and the risk of pathogen release into the environment; and (iii) there are some simple but little-used technical improvements to design and construction of on-site sanitation systems which could significantly reduce the release of pathogens to the environment.
卫生设施旨在减少粪便传播的疾病的传播和负担。在将污泥或污水排放到环境之前，从粪便中减少病原体，这似乎是卫生系统的一个合理且有用的性能指标。然而，常见卫生技术从粪便中释放病原体的相对程度尚不清楚。因此，我们在印度泰米尔纳德邦调查了不同卫生技术在减少病原体指示物大肠杆菌（E. coli）释放方面的性能测量的可行性。在对当地普遍存在的卫生系统进行用户调查和技术评估后，我们根据广泛接受的物理类型学，将它们分为 7 个不同类别（基于观察到的物理特征和使用情况）。从 136 个家庭系统、24 个社区系统和 23 个卫生下水道溢出中收集并分析粪便污泥和废水样本，以检测大肠杆菌和总固体。我们估计了不同卫生技术从污水和粪便污泥中的平均体积释放率。计算了每个技术的平均人均日大肠杆菌排放量，并将其用作技术公共卫生性能的一个指标。我们发现，所有者描述为“化粪池系统”的现场安装包括各种形式的性能不确定的水箱和坑。我们观察到不同卫生技术的人均日大肠杆菌排放量存在统计学上的显著差异（p = 0.00001）。从研究的现场卫生技术中释放的病原体数量相差多达 5 个数量级，从“衬里坑”（每人每天 5.4 对数大肠杆菌）到“溢出的卫生下水道”和“直接排放管”（每人每天 10.3-10.5 对数大肠杆菌）。其他技术介于这两个极端之间，它们在去除大肠杆菌方面的性能也存在显著差异，无论是在统计学上还是在实际应用中。我们的结果表明，尽管粪便污泥管理沿着卫生服务链很重要，但观察到的系统的卫生规划者（可能在其他地方也是如此）应将更高的优先级放在适当管理这些系统的液体废水上，以最大程度地减少公共卫生危害。我们得出结论：（i）这项工作展示了一种估计不同卫生技术公共卫生性能的新的有前途的方法；（ii）如果大肠杆菌被接受为粪便系统释放的公共卫生危害的指示物，我们的结果强烈表明，安全地长时间储存粪便会大大减少病原体数量，并减少病原体释放到环境中的风险；（iii）现场卫生系统的设计和施工有一些简单但很少使用的技术改进，可以显著减少病原体向环境的释放。
