British Geological Survey, Maclean Building, Wallingford, OX10 8BB, United Kingdom of Great Britain and Northern Ireland UK; Department of Geography, University College London, London WC1E 6BT, United Kingdom of Great Britain and Northern Ireland UK.
Department of Geology and Petroleum Studies, Makerere University, Uganda.
Water Res. 2021 Nov 1;206:117734. doi: 10.1016/j.watres.2021.117734. Epub 2021 Oct 3.
Faecal indicator organisms (FIOs) are limited in their ability to protect public health from the microbial contamination of drinking water because of their transience and time required to deliver a result. We evaluated alternative rapid, and potentially more resilient, approaches against a benchmark FIO of thermotolerant coliforms (TTCs) to characterise faecal contamination over 14 months at 40 groundwater sources in a Ugandan town. Rapid approaches included: in-situ tryptophan-like fluorescence (TLF), humic-like fluorescence (HLF), turbidity; sanitary inspections; and total bacterial cells by flow cytometry. TTCs varied widely in six sampling visits: a third of sources tested both positive and negative, 50% of sources had a range of at least 720 cfu/100 mL, and a two-day heavy rainfall event increased median TTCs five-fold. Using source medians, TLF was the best predictor in logistic regression models of TTCs ≥10 cfu/100 mL (AUC 0.88) and best correlated to TTC enumeration (ρ 0.81), with HLF performing similarly. Relationships between TLF or HLF and TTCs were stronger in the wet season than the dry season, when TLF and HLF were instead more associated with total bacterial cells. Source rank-order between sampling rounds was considerably more consistent, according to cross-correlations, using TLF or HLF (min ρ 0.81) than TTCs (min ρ 0.34). Furthermore, dry season TLF and HLF cross-correlated more strongly (ρ 0.68) than dry season TTCs (ρ 0.50) with wet season TTCs, when TTCs were elevated. In-situ TLF or HLF are more rapid and resilient indicators of faecal contamination risk than TTCs.
粪便指示生物（FIO）在保护公众健康免受饮用水微生物污染方面的能力有限，因为它们的短暂存在和产生结果所需的时间。我们评估了替代的快速、潜在更具弹性的方法，以应对在乌干达一个城镇的 40 个地下水源进行的为期 14 个月的粪便污染特征研究中的耐热大肠菌群（TTC）基准 FIO。快速方法包括：原位色氨酸类似荧光（TLF）、腐殖质类似荧光（HLF）、浊度；卫生检查；以及流式细胞术检测的总细菌细胞。TTC 在六次采样访问中变化很大：三分之一的水源检测结果呈阳性和阴性，50%的水源 TTC 范围至少为 720 cfu/100 mL，两天的强降雨事件使 TTC 中位数增加了五倍。使用源中位数，TLF 是 TTC≥10 cfu/100 mL 的逻辑回归模型中最好的预测因子（AUC 0.88），与 TTC 计数相关性最好（ρ 0.81），HLF 表现相似。在雨季，TLF 或 HLF 与 TTC 之间的关系比旱季更强，而在旱季，TLF 和 HLF 与总细菌细胞的相关性更强。根据交叉相关，与 TTC 相比，TLF 或 HLF 用于源排序（min ρ 0.81）在各轮采样之间的一致性更高（min ρ 0.34）。此外，与旱季 TTC（ρ 0.50）相比，旱季 TLF 和 HLF 与湿季 TTC 之间的相关性更强（ρ 0.68），此时 TTC 升高。原位 TLF 或 HLF 是比 TTC 更快、更具弹性的粪便污染风险指标。
