Probabilistic fecal pollution source profiling and microbial source tracking for an urban river catchment

Assessing the impact of inland navigation on the faecal pollution status of large rivers: A novel integrated field approach

The contribution of ships to the microbial faecal pollution status of water bodies is largely unknown but frequently of human health concern. No methodology for a comprehensive and target-orientated system analysis was available so far. We developed a novel approach for integrated and multistage impact evaluation. The approach includes, i) theoretical faecal pollution source profiling (PSP, i.e., size and pollution capacity estimation from municipal vs. ship sewage disposal) for impact scenario estimation and hypothesis generation, ii) high-resolution field assessment of faecal pollution levels and chemo-physical water quality at the selected river reaches, using standardized faecal indicators (cultivation-based) and genetic microbial source tracking markers (qPCR-based), and iii) integrated statistical analyses of the observed faecal pollution and the number of ships assessed by satellite-based automated ship tracking (i.e., automated identification system, AIS) at local and regional scales. The new approach was realised at a 230 km long Danube River reach in Austria, enabling detailed understanding of the complex pollution characteristics (i.e., longitudinal/cross-sectional river and upstream/downstream docking area analysis). Faecal impact of navigation was demonstrated to be remarkably low at regional and local scale (despite a high local contamination capacity), indicating predominantly correct disposal practices during the investigated period. Nonetheless, faecal emissions were sensitively traceable, attributable to the ship category (discriminated types: cruise, passenger and freight ships) and individual vessels (docking time analysis) at one docking area by the link with AIS data. The new innovative and sensitive approach is transferrable to any water body worldwide with available ship-tracking data, supporting target-orientated monitoring and evidence-based management practices.

Integrating fecal pollution markers and fluorescence analysis for water quality assessment of urban river

Human fecal contamination in urban rivers poses significant health risks, but their potential connections with other substances like dissolved organic matter (DOM) remain underexplored. In this study, five fecal pollution markers related to fecal Bacteroides or human fecal contamination (AllBac, HF183, BacH, Hum2, and Hum163) and DOM along an urban river were analyzed using quantitative polymerase chain reaction (qPCR) and three-dimensional excitation-emission (3D EEM) fluorescence spectrometry. All five markers were detected with average absolute abundance ranging from 2.51 to 6.28 lg gene copies/100 mL, showing a progressive increase along the river (R2 = 0.29-0.92, p < 0.05). Parallel factor analysis identified three dominant DOM components (humic acid-like, fulvic acid-like, and protein-like), with strong positive correlations between protein-like components and all fecal markers (R2 = 0.59-0.66, p < 0.001). Both fecal and DOM distributions consistently showed significant differences between upstream and downstream areas (p < 0.001), suggesting their complementary assessment. While DOM was more sensitive to environmental variables such as rainfall, rubber dam, and tidal dynamic, the combination of fecal pollution markers and 3D EEM analysis allowed a more comprehensive assessment of contamination levels, mitigating potential biases caused by the influence of multiple factors on a single method. Furthermore, due to the strong correlation between protein-like and fecal markers in the DOM, 3D EEM can be used as a pre-detection means for qPCR detection, reducing testing time and costs.

Diversity of Fecal Indicator Enterococci among Different Hosts: Importance to Water Contamination Source Tracking

Enterococcus spp. are common bacteria present in the intestinal tracts of animals and are used as fecal indicators in aquatic environments. On the other hand, enterococci are also known as opportunistic pathogens. Elucidating their composition in the intestinal tracts of domestic animals can assist in estimating the sources of fecal contamination in aquatic environments. However, information on the species and composition of enterococci in animal hosts (except humans) is still lacking. In this study, enterococci were isolated from the feces of cattle, pigs, birds, and humans using selective media. Enterococcal species were identified using mass spectrometry technology, and each host was characterized by diversity and cluster analysis. The most dominant species were E. hirae in cattle, E. faecium in birds, and E. faecalis in pigs and humans. Cattle had the highest alpha diversity, with high interindividual and livestock farm diversity. The dominant enterococcal species in pigs and humans were identical, and cluster analysis showed that the majority of the two hosts' species clustered together.

A simple and rapid method for detecting fecal pollution in urban rivers by measuring the intrinsic β-D-glucuronidase activity of Escherichia coli

As urban rivers are domestic, industrial, and agricultural water resources, fecal pollution poses human health and environmental risks. In this study, we developed a simple and rapid method to detect fecal pollution in urban rivers. Water samples were mixed with liquid medium, including a fluorescent substrate and fluorescence intensity (F.I.) was measured using a microplate reader to determine Escherichia coli (E. coli) β-D-glucuronidase (GUS) activity instead of E. coli concentration. GUS activities measurements in pure E. coli cultures revealed that E. coli incubated with a GUS substrate accumulated GUS enzymes in their cells, whereas those incubated without a GUS substrate did not. The increase in GUS activity corresponded to the proliferation of E. coli and the GUS activity increased linearly even during the lag growth phase of E. coli, indicating the presence of intrinsic GUS (iGUS) in E. coli cells before incubation. iGUS activity persisted at 81 % in the chlorinated samples, even though the E. coli concentration was reduced by a factor of 106. The iGUS activity persisted for approximately three days. Therefore, we assumed that E. coli present in fecal contaminants, in which GUS substrates are present, could be distinguished from those surviving in the natural environment for three days or longer by measuring iGUS activity. River water samples were collected upstream and downstream of the discharge outlets of municipal wastewater treatment plants and a combined sewer outlet. The iGUS activities were <0.24 mMFU/mL for the upstream samples and >0.21 mMFU/mL for the downstream samples. Interestingly, E. coli concentrations were not necessarily associated with fecal pollution. This indicates that by setting a threshold for iGUS activity, our method can be used as a simple and rapid method for detecting fecal pollution in urban rivers. Because the limit of detection for our method is 20 CFU/mL, our method is applicable to detecting high fecal pollution in a small river.

Microbial source tracking using molecular and cultivable methods in a tropical mixed-use drinking water source to support water safety plans

Microbial contamination deteriorates source water quality, posing a severe problem for drinking water suppliers worldwide and addressed by the Water Safety Plan framework to ensure high-quality and reliable drinking water. Microbial source tracking (MST) is used to examine different microbial pollution sources via host-specific intestinal markers for humans and different types of animals. However, the application of MST in tropical surface water catchments that provide raw water for drinking water supplies is limited. We analyzed a set of MST markers, namely, three cultivable bacteriophages and four molecular PCR and qPCR assays, together with 17 microbial and physicochemical parameters, to identify fecal pollution from general, human-, swine-, and cattle-specific sources. Seventy-two river water samples at six sampling sites were collected over 12 sampling events during wet and dry seasons. We found persistent fecal contamination via the general fecal marker GenBac3 (100 % detection; 2.10-5.42 log₁₀ copies/100 mL), with humans (crAssphage; 74 % detection; 1.62-3.81 log₁₀ copies/100 mL) and swine (Pig-2-Bac; 25 % detection; 1.92-2.91 log₁₀ copies/100 mL). Higher contamination levels were observed during the wet season (p < 0.05). The conventional PCR screening used for the general and human markers showed 94.4 % and 69.8 % agreement with the respective qPCR results. Specifically, in the studied watershed, coliphage could be a screening parameter for the crAssphage marker (90.6 % and 73.7 % positive and negative predictive values; Spearman's rank correlation coefficient = 0.66; p < 0.001). The likelihood of detecting the crAssphage marker significantly increased when total and fecal coliforms exceeded 20,000 and 4000 MPN/100 mL, respectively, as Thailand Surface Water Quality Standards, with odds ratios and 95 % confidence intervals of 15.75 (4.43-55.98) and 5.65 (1.39-23.05). Our study confirms the potential benefits of incorporating MST monitoring into water safety plans, supporting the use of this approach to ensure high-quality drinking water supplies worldwide.