Identifying Sources of Faecal Contamination in a Small Urban Stream Catchment: A Multiparametric Approach

Small urban streams discharging in the proximity of bathing waters may significantly contribute to the deterioration of water quality, yet their impact may be overlooked. This study focuses on the Elm Park stream in the city of Dublin that is subject to faecal contamination by unidentified sources. The aim of the study was to identify a minimum number of “sentinel” sampling stations in an urban catchment that would provide the maximum amount of information regarding faecal pollution in the catchment. Thus, high-resolution sampling within the catchment was carried out over the course of 1 year at 11 stations. Faecal indicator bacteria were enumerated and microbial source tracking (MST) was employed to evaluate human pollution. In addition, ammonium, total oxidised nitrogen, and phosphorus levels were monitored to determine if these correlated with faecal indicator and the HF183 MST marker. In addition, the effect of severe weather events on water quality was assessed using automated sampling at one of the identified “sentinel” stations during baseflow and high flow conditions over a 24-h period. Our results show that this urban stream is at times highly contaminated by point source faecal pollution and that human faecal pollution is pervasive in the catchment. Correlations between ammonium concentrations and faecal indicator bacteria (FIB) as well as the human MST marker were observed during the study. Cluster analysis identified four “sentinel” stations that provide sufficient information on faecal pollution in the stream, thus reducing the geographical complexity of the catchment. Furthermore, ammonium levels strongly correlated with FIB and the human HF183 MST marker under high flow conditions at key “sentinel” stations. This work demonstrates the effectiveness of pairing MST, faecal indicators, and ammonium monitoring to identify “sentinel” stations that could be more rapidly assessed using real-time ammonium readouts to assess remediation efforts.

Spatial and temporal variations of faecal indicator bacteria in Lake Bunyonyi, South-Western Uganda

Background Microbial water quality serves to indicate health risks associated with the consumption of contaminated water. Nevertheless, little is known about the microbiological characteristics of water in Lake Bunyonyi. This study was therefore undertaken to examine the spatial and temporal variations of faecal indicator bacteria (FIB) in relation to physicochemical parameters in Lake Bunyonyi. Result The FIB concentration was consistently measured during sampling months and correlated with each other showing the presumed human faecal pollution in the lake. The highest concentration values for E. coli (64.7 ± 47.3 CFU/100 mL) and enterococci (24.6 ± 32.4 CFU/100 mL were obtained in the station close to the Mugyera trading centre. On a temporal basis, the maximum values were recorded during the rainy season in October 2019 (70.7 ± 56.5 CFU/100 mL for E. coli and 38.44 ± 31.8 CFU/100 mL for enterococci. FIB did not differ significantly among the study stations (p > 0.05) but showed significant temporal variations among the months (p < 0.05) with concentrations being significantly high in wet season than dry season (U = 794, p < 0.0001 for E. coli; U = 993.5, p = 0.008 for enterococci). Spearman’s rank correlation revealed that FIB concentrations were significantly positively correlated with turbidity and DO concentration levels (p < 0.05). Approximately 97.2% of the water samples had E. coli and enterococci concentrations levels below USEPA threshold for recreational waters. Likewise, 98.1 and 90.7% of samples recorded E. coli and enterococci counts exceeding the UNBS, APHA, WHO and EU threshold values for drinking water. Conclusion The FIB counts show that the Lake Bunyonyi water is bacteriologically unsuitable for drinking unless it is treated since the FIB pose health risks to consumers. Besides, the water can be used for recreational purposes.

Correlation between faecal indicator bacteria in diarrheagenic stools and hospital wastewaters: Implication on public health

Background: Hospital wastewaters contain blends of inorganic, natural constituents and contaminants that carry significant health risk when released directly into the environment. The aim of this study is to investigate the correlation between faecal indicator bacteria in diarrheagenic stools and wastewaters generated in University of Medical Sciences Teaching Hospital complex, Akure, Nigeria.Methodology: Quantification of faecal indicator bacteria was carried out on diarrheagenic faecal samples collected from 55 hospitalized patients and 68 wastewater samples from the medical laboratory science and laundry units of the hospital over of period of 12 weeks. Standard membrane filtration technique was performed using membrane intestinal enterococcus (m-ENT), membrane faecal coliform (m-FC), membrane lauryl sulphate (MLSA), eosin methylene blue (EMB) and Salmonella-Shigella (SS) agar plates, which were incubated at 37ºC for 24 hours (MLSA, EMB and SSA), 44ºC for 24 hours (m-FC); and 37ºC for 48 hours (m-ENT). Bacterial colonies on agar plates were counted and expressed as colony forming units (CFU) per 100ml of diarrheagenic stool and wastewater. Pearson’scorrelation analysis was used to determine the relationship between the level of faecal indicator bacteria in diarrheagenic stools and wastewaters at p<0.05 level of significance (and 95% confidence interval).Results: The faecal coliform counts (log 10 CFU/100ml) ranged from 1.18 to 1.54 in diarrheagenic stools, 1.32 to1.64 in laboratory wastewater and 1.08 to 2.19 in laundry wastewater. Escherichia coli count (log 10 CFU/100ml) ranged from 1.08 to 1.40 in diarrheagenic stools, 1.20 to 1.86 in laboratory wastewater and 0.30 to 1.81 in laundry wastewater. Intestinal enterococci count (log 10 CFU/100ml) ranged from 0 to 0.30 in diarrheagenic stools, 0.78 to 0.90 in laboratory wastewaters and 0.48 to 1.11 in laundry wastewaters. Pearson’s correlation co-efficient showed that all the faecal indicator bacteria count in diarrheagenic faecal samples exhibited positive correlation with those in laboratory wastewaters, but not with those from laundry wastewaters.Conclusion: The findings suggest that diarrheagenic stools should be properly disinfected after the performance of laboratory tests to prevent transmission of potential pathogens, and wastewater generated from hospitals should be treated prior to discharge into the environment, to prevent possible infections in the community. Keywords: Correlation, faecal indicator bacteria, public health, transmission, wastewater

Study of the plastisphere: biofilm development and presence of faecal indicator bacteria on microplastics from the Río de la Plata estuary

Microplastics (MPs) are considered emerging pollutants and often enter aquatic ecosystems carried by currents and tides until they accumulate on the shorelines. In many cases they may be colonized by diverse microorganisms forming a community called plastisphere, which can even act as a reservoir for pathogenic microorganisms. This study carried out in the Río de la Plata estuary (southern coastal fringe, Argentina) focused on two main objectives, the analysis of the biofilm colonizing MPs under laboratory conditions, and the detection of bacteria indicating faecal contamination (Escherichia coli and Enterococci), in MPs from the intertidal sediment at coastal sites with different land uses, in the freshwater sector of the Río de la Plata estuary. The colonization experiment was carried out in the laboratory with water from the estuary for a period of 35 days (residence time of the water in the freshwater sector of the estuary). The results revealed a remarkable development and diversity of biofilm organisms from the second week of colonization on, covering the surface of the microplastic and thus masking this pollutant. On the other hand, the presence of faecal indicator bacteria in the MPs of the intertidal sediment was confirmed in all the studied sites, being proportionally higher on MPs found in areas influenced by sewage discharges.