Butte G, Niwagaba C, Nordin A
School of Engineering, Newcastle University, Newcastle Upon, Tyne, UK.
Department of Civil and Environmental Engineering, College of Engineering, Design, Art and Technology (CEDAT), Makerere University, P. O. Box 7062, Kampala, Uganda.
Water Res. 2021 Jun 1;197:117068. doi: 10.1016/j.watres.2021.117068. Epub 2021 Mar 23.
Reuse of faecal sludge in agriculture has many potential benefits, but also poses risks to human health. To better understand the potential risks, Quantitative Microbial Risk Assessment (QMRA) was performed for three population groups in Kampala, Uganda: wastewater and faecal sludge treatment plant workers; farmers using faecal sludge; and consumers of faecal sludge-fertilised vegetables. Two models were applied for farmers and consumers, one based on pathogen concentrations from field sampling of sludge, soils and vegetables, and one based on theoretical pathogen contribution from the last sludge application, including decay and soil to crop transfer of pathogens. The risk was evaluated for two pathogens (enterohaemorrhagic E. coli (EHEC) and Ascaris lumbricoides). The field data on sludge, soil and vegetables indicated that the last application of faecal sludge was not the sole pathogen source. Correspondingly, the model using field data resulted in higher risks for farmers and consumers than the theoretical model assuming risk from sludge only, except when negligible for both. For farmers, the yearly risk of illness, based on measured concentrations, was 26% from EHEC and 70% from Ascaris, compared with 1.2% and 1.4%, respectively, considering the theoretically assumed contribution from the sludge. For consumers, the risk of illness based on field samples was higher from consumption of leafy vegetables (100% from EHEC, 99% from Ascaris) than from consumption of cabbages (negligible for EHEC, 26% from Ascaris). With the theoretical model, the risk of illness from EHEC was negligible for both crops, whereas the risk of illness from Ascaris was 64% and 16% for leafy vegetables and cabbage, respectively. For treatment plant workers, yearly risk of illness was 100% from EHEC and 99.4% from Ascaris. Mitigation practices evaluated could reduce the relative risk by 30-70%. These results can help guide treatment and use of faecal sludge in Kampala, to protect plant workers, farmers and consumers.
农业中粪便污泥的再利用有许多潜在益处，但也对人类健康构成风险。为了更好地了解潜在风险，对乌干达坎帕拉的三类人群进行了定量微生物风险评估（QMRA）：废水和粪便污泥处理厂工人；使用粪便污泥的农民；以及食用粪便污泥施肥蔬菜的消费者。针对农民和消费者应用了两种模型，一种基于污泥、土壤和蔬菜现场采样的病原体浓度，另一种基于上次污泥施用的理论病原体贡献，包括病原体的衰减和从土壤到作物的转移。对两种病原体（肠出血性大肠杆菌（EHEC）和蛔虫）进行了风险评估。关于污泥、土壤和蔬菜的现场数据表明，上次粪便污泥施用并非唯一的病原体来源。相应地，与仅假设来自污泥风险的理论模型相比，使用现场数据的模型得出的农民和消费者风险更高，除非两者都可忽略不计。对于农民，基于实测浓度，EHEC导致的年发病风险为26%，蛔虫导致的为70%，而考虑到理论上假设的污泥贡献，分别为1.2%和1.4%。对于消费者，基于现场样本，食用叶菜类蔬菜导致的发病风险（EHEC为100%，蛔虫为99%）高于食用卷心菜（EHEC可忽略不计，蛔虫为26%）。使用理论模型时，两种作物由EHEC导致的发病风险均可忽略不计，而叶菜类蔬菜和卷心菜由蛔虫导致的发病风险分别为64%和16%。对于处理厂工人，EHEC导致的年发病风险为100%，蛔虫导致的为99.4%。评估的缓解措施可将相对风险降低30 - 70%。这些结果有助于指导坎帕拉粪便污泥的处理和利用，以保护工厂工人、农民和消费者。
