Bacterial source tracking from diverse land use catchments by sterol ratios

Water samples from sites potentially impacted by septic tanks, cattle, sewage treatment plant (STP) and natural forests were collected at regular monthly intervals and within 48 h of rainfall events between October 2004 and June 2006. All samples (n=296) were analysed for faecal coliforms and faecal sterols including coprostanol, epicoprostanol, cholestanol, cholesterol and 24-ethylcoprostanol. Faecal sterol ratios were used to assign human and/or herbivore contamination sources and to estimate their percentage relative contributions in water samples. The catchments had significantly different profiles of designated contamination origins (p<0.05), which were consistent with land use patterns. The STP impacted site had the highest incidence of human contamination assignations and the highest mean levels of coprostanol, whilst the forested site had the highest incidence of uncontaminated samples and the lowest mean concentration of coprostanol. Coprostanol concentrations were not always correlated with faecal coliform counts.     

Evaluating the input and source of faecal contamination in the cattle farming and forested regions of the Oconee watershed

Sites along Sugar Creek and the Apalachee River were monitored to compare the water quality in cattle farming regions with the forested regions of the Oconee watershed. Dissolved oxygen (6.68 mg/L) and turbidity [23.91 nephelometric turbidity units (NTU)] in Sugar Creek and the Apalachee River were similar. Overall, cattle farming sites along Sugar Creek had higher levels of NO₃^? and PO₄^?3 during the summer months. In contrast, the forested sites on the Apalachee River had elevated concentrations of inorganic nutrients only during spring rain events. The concentration of faecal bacteria was greater in the cattle farming areas compared with the level of faecal bacteria in the forested areas, and microbial source tracking with the bovine‐associated Bacteroides (BoBac) DNA marker indicated that cattle were the major source of faecal bacteria in Sugar Creek.     

Evaluating potential applications of faecal sterols in distinguishing sources of faecal contamination from mixed faecal samples

Faecal samples from humans, herbivores, carnivores and birds as well as samples from septic tanks and effluents from a sewage treatment plant (STP) were extracted and analyzed by gas chromatography-mass spectrometry for faecal sterols including coprostanol, epicoprostanol, cholestanol, cholesterol, stigmasterol, campesterol, 24-ethylcoprostanol and beta-sitosterol. Coprostanol was observed in the highest concentrations from the human derived samples, but it was also present in substantial quantities in a range of herbivores. There was no unique marker of human faecal contamination. Multivariate analyses revealed that the faecal sterol profiles were significantly different between the four groups of animals (Wilks' lambda=0.007, P<0.002), and coprostanol and 24-ethylcoprostanol were the major discriminant factors. However, when faecal samples were mixed, the confounding of faecal sterol levels prevented accurate identification of contributing species. Conversely, faecal sterol ratios were highly efficient at identifying which mixtures contained human contribution, but could not appropriately determine percentage contributions of sources.     

Distribution of indicator bacteria in Canyon Lake, California

The spatial and temporal distributions of indicator bacteria in a small, multiple-use source drinking water reservoir in Southern California, USA were quantified over the period August 2001-July 2002. High levels of total and fecal coliform bacteria were present in Canyon Lake (annual geometric mean concentrations+/-SEM of 3.93+/-0.02 and 3.02+/-0.03 log cfu/100mL, respectively), while comparatively low levels of enterococci and E. coli were found (1.16+/-0.02 log cfu/100mL and 0.30+/-0.03 log MPN/100mL, respectively). As a result, these different indicator bacteria yielded quite divergent indices of water quality, with 72.1% of all surface samples (n=294) exceeding the USEPA single-sample limit of 400 cfu/100mL fecal coliform bacteria, while none (0%) of the samples exceeded the single-sample limit for E. coli (n=194). Regression analyses found a positive correlation between total and fecal coliform bacteria (R=0.50, significant at p<0.001) and between enterococci and E. coli (R=0.51, significant at p<0.001), but no correlation or inverse correlations were found between coliform concentrations and enterococci and E. coli levels. External sources responsible for the high total and fecal coliform bacteria were not identified, although laboratory studies demonstrated growth of the coliform bacteria in lake water samples. Enterococci and E. coli were not observed to grow, however. Bacteria concentrations varied relatively little laterally across the lake, although strong vertical gradients in fecal coliform and enterococcus bacteria concentrations were present during summer stratification, with concentrations about 10x higher above the thermocline when compared with surface concentrations. In contrast, total bacteria, total virus and total coliform bacteria levels were unchanged with depth. Seasonal trends in bacteria concentrations were also present. This study shows that the choice of indicator bacteria and sampling depth can both strongly affect the apparent microbial water quality of a lake or reservoir.     

Faecal bacteria yields in artificial flood events: quantifying in-stream stores

Stream sediments have been recognised as an in-channel store of faecal contamination that can be mobilised during floods or other sediment-disturbing events. We studied this store of faecal contamination by creating artificial floods during dry weather when, in the absence of overland flow from the catchment, the only source of faecal bacteria was stores within the channel. Artificial floods, created by releasing water from a supply reservoir, increased the E. coli concentration in the water column by two orders of magnitude, from a background level of 10(2) cfu per 100 mL to over 10(4) cfu per 100 mL. The bacterial peak concentrations and yields declined systematically through a triplicate flood series. The size of the total in-channel store, calculated as the sum of yields of an infinite series of artificial floods, was approximately 10(8) cfu m(-2) of streambed area. Direct measurements of sediment E. coli found few sites (only those associated with cattle crossings) with areal concentrations as high as 10(8) cfu m(-2), consistent with flood yields. Concentrations of E. coli in the biofilms on exposed rocks were orders of magnitude lower, indicating that exposed rocks were not a source of E. coli released by the artificial floods.     

Seasonal variations of several pharmaceutical residues in surface water and sewage treatment plants of Han River, Korea

We collected influent and effluent samples from four sewage treatment plants (STPs) as well as surface water samples in Han River of Seoul, Korea, in three sampling events representing different flow conditions, i.e., April, June, and August, 2005, and analyzed for eleven pharmaceuticals including acetaminophen, caffeine, carbamazepine, cimetidine, diltiazem, trimethoprim, and five sulfonamide antibiotics, using LC-MS-ESI. Pharmaceuticals of high annual production amount were detected in higher level in STP influents. Levels of pharmaceutical residues in the influents were the highest for acetaminophen (average 27,089 ng/L), followed by caffeine (23,664 ng/L), cimetidine (8045 ng/L), and sulfamethoxazole (523 ng/L). Levels of acetaminophen and caffeine in STP effluents were very low compared to the influent concentrations. However cimetidine was detected in relatively high levels even in STP effluent samples. In effluent samples, cimetidine showed the highest level (5380 ng/L), followed by caffeine (278 ng/L), sulfamethoxazole (193 ng/L), and carbamazepine (111 ng/L). The concentration of cimetidine was also the highest in surface water samples (average 281 ng/L), which is the highest level reported from surface water worldwide to our knowledge. Caffeine (268.7 ng/L), acetaminophen (34.8 ng/L), and sulfamethoxazole (26.9 ng/L) were also detected in relatively high levels. Levels of pharmaceuticals detected in surface water samples upstream STPs were generally very low compared to the downstream samples, suggesting that the STPs potentially be a major source of the test pharmaceuticals into Han River. The hazard quotients (HQs) were calculated for the test pharmaceuticals based on their occurrences in surface water, and no pharmaceutical resulted in HQ greater than one, suggesting that their potential environmental impact may be low.     

Faecal coliforms and faecal streptococci in streams in the new guinea highlands

Procedures used to assess faecal water contamination were developed in temperate regions and their applicability to tropical waters has been questioned. This paper reports a detailed study of faecal coliform and faecal streptococci concentrations in the streams of the Saka Valley in the Highlands of New Guinea. The Saka Valley supports large populations of humans and domestic pigs, whose faeces are washed into the streams by surface runoff following rain. Faecal coliforms and faecal streptococci, enumerated by the membrane filtration technique, were found to be excellent indicators of faecal pollution in the New Guinea Highlands. A consideration of faecal coliform to faecal streptococci ratios and other factors, leads to the conclusion that most faecal contamination derives from pigs. All waters investigated, with the exception of spring waters, were grossly contaminated with faecal material and these polluted streams provide the total domestic water needs of the New Guineans. The fluctuations in pollution levels are described and their association with water temperature, rainfall and turbidity is analysed. The interpretation of the water contamination data is made speculative by the lack of information on the coliform and streptococcal flora of fresh pig and human faeces under New Guinea Highlands conditions.     

Washout of accumulated testosterone in a watershed

Testosterone is constantly excreted into the environment by both human and animal sources but little is known about how it is transported in the environment. In this study, testosterone was measured in 15 sites in the Upper Jordan Valley after major rain events (238 samplings) for two consecutive rain seasons. The area consists of small farms, cattle pasture, fish ponds with some urban development. One liter samples were extracted on solid phase columns and the eluates measured using specific radio-immunoassay for testosterone and estrogen (estradiol + estrone). The first rain season was the first above average season after a 3-year period of well below average rainfall. It was found in the rain season of 2001/2002, that following a rain sequence of 131 mm/week there was an initial large increase in the concentration of testosterone (maximum 6 ng/l) accompanied by high estrogen (maximum 6 ng/l), which then gradually declined to non-detectable levels (< 0.3 ng/l) over a period of 3 months. These peaks originated from runoff from cattle pasture and fish pond effluent. Later peaks consisted only of testosterone that was moderately associated with sulfate (r2 = 0.53, P < 0.05) and somewhat associated with total phosphorus (r2 = 0.49, P < 0.1) indicating that the origin was leaching from the sulfurous peat soil. In the following rainy season, which had recorded rainfalls, no testosterone peaks above 1 ng/l were seen. We conclude that the testosterone accumulated in the Upper Jordan Valley was washed out in two stages, first as surface runoff from cattle pasture and then as discharge from the soil.     

Concentrations of coprostanol that correspond to existing bacterial indicator guideline limits

Coprostanol is a faecal sterol that has been proposed as an alternative measure of faecal pollution. While the technique has been used successfully to trace sewage-derived organic matter in a range of environments, it has not been embraced for use as a water quality indicator. This is mostly because of a lack of epidemiological evidence relating coprostanol abundance to any health risk. However, there is a valuable reason why the concentration of coprostanol should be related as quantitatively as possible to the abundance of bacterial indicators currently used to measure faecal pollution. The measurement of coprostanol (and concurrently other faecal sterols) offers many diagnostic and quantitative advantages over traditional techniques for detecting human sewage pollution versus faecal contamination from animal sources. Knowing the amount of coprostanol expected given a certain amount of human sewage pollution would provide a measure against which water managers could quantitatively assess faecal pollution as a whole and relate that assessment to variables with which they are more familiar. This study determines the relationships between coprostanol concentrations and indicator bacterial counts and synthesises the results from several environments to propose coprostanol concentrations broadly equivalent to existing bacterial standards. Our data suggest that 60 and 400 ng L⁻¹ of coprostanol correspond to currently defined primary and secondary contact limits for bacteria measured as thermotolerant coliforms (commonly referred to as faecal coliforms) or enterococci.     

Sources and growth dynamics of fecal indicator bacteria in a coastal wetland system and potential impacts to adjacent waters

Coastal wetlands are receiving increased attention as a putative source of fecal indicator bacteria (FIB) in Southern California coastal waters. We examined temporal trends of water and sediment-associated FIB after rain events along with spatial sediment characteristics at two sites within the Santa Ana River wetlands and made comparisons to FIB levels observed in adjacent surf zone waters. During the first two rain events, total coliforms (TC), Escherichia coli (EC) and enterococci (ENT) in wetland water and sediment samples peaked either on the same day or within several days of the rain event, while the third resulted in elevated wetlands sediment TC levels only. TC in adjacent coastal waters consistently peaked on the same day as the rain event and decreased quickly thereafter (within 1 day). The TC/EC ratios of surf zone samples consistently fell below 10, indicating an increased probability of human fecal contamination whereas wetland TC/EC ratios were higher, averaging approximately 60 and 14 at each site. These results suggest sediment-associated FIB populations may be distinct from those found in the water samples, or at least have internal dynamics independent of water-borne populations. Increases in sediment-associated FIB may be due to in situ population growth and/or increased survival due to changes in environmental parameters (salinity, moisture and nutrient input) resulting from the rain events. Spatial differences in between the two sites may be due to sediment differences such as organic content and finer grain size and/or discrete sources of FIB.     

Chemometric approach to validating faecal sterols as source tracer for faecal contamination in water

Faecal sterols detection is a promising method for identifying sources of faecal pollution. In this study, faecal contamination in water samples from point source (sewage treatment plants, chicken farms, quail farms and horse stables) was extracted using the solid phase extraction (SPE) technique. Faecal sterols (coprostanol, cholesterol, stigmasterol, β-sitosterol and stigmastanol) were selected as parameters to differentiate the source of faecal pollution. The results indicated that coprostanol, cholesterol and β-sitosterol were the most significant parameters that can be used as source tracers for faecal contamination. Chemometric techniques, such as cluster analysis, principal component analysis and discriminant analysis were applied to the data set on faecal contamination in water from various pollution sources in order to validate the faecal sterols’ profiles. Cluster analysis generated three clusters: coprostanol was in cluster 1, cholesterol and β-sitosterol formed cluster 2, while cluster 3 contained stigmasterol and stigmastanol. Discriminant analysis suggested that coprostanol, cholesterol and β-sitosterol were the most significant parameters to discriminate between the faecal pollution source. The use of chemometric techniques provides useful and promising indicators in tracing the source of faecal contamination.     

Development of microbial and chemical MST tools to identify the origin of the faecal pollution in bathing and shellfish harvesting waters in France

The microbiological quality of coastal or river waters can be affected by faecal pollution from human or animal sources. An efficient MST (Microbial Source Tracking) toolbox consisting of several host-specific markers would therefore be valuable for identifying the origin of the faecal pollution in the environment and thus for effective resource management and remediation. In this multidisciplinary study, after having tested some MST markers on faecal samples, we compared a selection of 17 parameters corresponding to chemical (steroid ratios, caffeine, and synthetic compounds), bacterial (host-specific Bacteroidales, Lactobacillus amylovorus and Bifidobacterium adolescentis) and viral (genotypes I-IV of F-specific bacteriophages, FRNAPH) markers on environmental water samples (n = 33; wastewater, runoff and river waters) with variable Escherichia coli concentrations. Eleven microbial and chemical parameters were finally chosen for our MST toolbox, based on their specificity for particular pollution sources represented by our samples and their detection in river waters impacted by human or animal pollution; these were: the human-specific chemical compounds caffeine, TCEP (tri(2-chloroethyl)phosphate) and benzophenone; the ratios of sitostanol/coprostanol and coprostanol/(coprostanol+24-ethylcopstanol); real-time PCR (Polymerase Chain Reaction) human-specific (HF183 and B. adolescentis), pig-specific (Pig-2-Bac and L. amylovorus) and ruminant-specific (Rum-2-Bac) markers; and human FRNAPH genogroup II.     

Microbiology of pond ecosystems in rural Bangladesh: its public health implications

In rural Bangladesh various components of four ponds, including aquatic plants, snails, water, oysters, and sediment were studied for faecal contamination for three years, from July 1994, to June 1997. Faecal coliform counts ranged from 2.80–5.45, 2.95–5.64, 1.49–2.05, 2.51–4.60 and 1.30–3.15 log₁₀cfu/gm or ml in plant, snail, water, oyster and sediment samples respectively during the study period. Snail and sediment samples showed highest and lowest counts, respectively. All components of the studied ponds included in this study yielded coliform counts higher than the accepted limit for potability and domestic use, as recommended by the WHO. Therefore these ponds have a high potential for transmission of diarrhoeal and other water‐borne diseases.     

Impact of inland pollution sources on the bacteriological water quality of the Southern Ganghwado Bay Area,South Korea

The bacteriological pollution of water is a serious global environmental issue. The pollution of water by human and animal wastes can be a source of hazardous pathogens, which may pose serious health risks. In this study, we evaluated the microbiological water quality in the southern Ganghwado Bay area, South Korea. A total of 30 samples (14 discharge water samples from the drainage area and 16 sea water samples from the adjacent area) were analyzed for the concentrations of total coliforms (TC) and fecal coliforms (FC) in November 2013. The highest concentration of FC (28,000 MPN/100 mL) was found at site L1 (inland). The highest mean concentrations of coliforms were found at sites W9 (sea water) and W11 (sea water), with TC and FC concentrations of 33 MPN/100 mL. In conclusion, site L1 located near W9 and W11 is clearly identified as the main source of pollution at Dongmak Beach.     

重庆城市污水粪大肠菌污染源调查

对重庆市几个主要区县的城市污水排放口及医院污水排放口进行了抽样调查,结果显示未经处理的城市污水粪大肠菌值主要处于106~107个/L数量级,最大值与最小值之间相差4个数量级。医院污水处理系统虽设计安装有消毒装置,但运行管理不当,出水粪大肠菌严重超标,主要处于104~105个/L数量级,低于城市生活污水。比较了安装与未安装消毒装置的污水处理厂出水中粪大肠菌值,技术经济比较结果显示,氯法、紫外光和臭氧消毒技术在城市污水排放消毒和回用水消毒、医院污水排放消毒方面各有优缺点,宜根据实际情况单独或组合使用。     

Mechanisms of microwave irradiation involved in the destruction of fecal coliforms from biosolids

Microwaves have been found to be effective in destructing pathogens in sewage sludge (biosolids) (75th Annual Water Environment Federation Conference, Chicago, September 29-October 2, 2002; Third World Water Congress, International Water Association, Melbourne, Australia, April 7-12, 2002). Mechanisms and roles of microwaves on fecal coliform destruction were investigated using bacterial viability tests, electron transport system (ETS) and beta-galactosidase activity assays, gel electrophoresis, and genomic deoxyribonucleic acid (DNA) optical density (OD) measurements with fecal coliforms isolated from biosolids. Bacterial viability tests demonstrated cell membrane damage as microwave irradiation intensity and temperature increased. Above 60+/-3 degrees C, viable cells were rarely found when pure fecal coliforms were irradiated with microwaves. ETS and beta-galactosidase activity assays revealed increased activity for externally heated samples due to fecal coliform growth but decreased activity for microwave-irradiated samples as temperature was increased from 20 degrees C to 57 degrees C, indicating other destruction mechanisms besides heating. Between 57 degrees C and 68 degrees C, microwave irradiation led to a more rapid decrease in activity than external heating by convection. Above 68 degrees C, bacterial activity almost ceased for both pretreatments. DNA bands in gel electrophoresis tests and OD of genomic DNA decreased more rapidly for microwave-irradiated samples than for externally heated samples, implying that microwaves disrupted DNA in fecal coliform cells at lower temperatures than external heating. Microwave irradiation of sludge appears to be a viable and economical method of destructing pathogens and generating environmentally safe sludge.     

Evaluation of onsite sewage treatment and disposal systems in shallow karst terrain

Two conventional onsite sewage treatment and disposal systems (OSTDSs) at Manatee Springs State Park, Florida, USA, were studied to assess their impact on groundwater quality in a shallow karst environment. Sulfur hexafluoride (SF6) and fluorescein were used as tracers to establish connections between the drainfields and monitoring wells. Elevated nutrients were found in all wells where significant concentrations of both tracers were observed, with the mean of the highest nitrate (NO3) concentration observed at each well being 47.8+/-14.9 (n=11) mg/L NO3-N. The most elevated nutrient concentrations were found directly in the flow path of the effluent. Fecal coliform densities above 10 colony-forming units (cfu)/100 mL were observed in wells with the most rapid connection to the drainfield. The proximity and connectivity of the 0.4-4m thick sandy surficial soils and the underlying karst aquifer allow rapid contaminant transport and limit the ability of conventional OSTDSs to attenuate NO3.     

Detection of pathogenic Escherichia coli strains in groundwater in the Yaoundé region (Cameroon,Central Africa)

This study was aimed at assessing the prevalence of pathogenic Escherichia coli strains, relative to the total count of E. coli, faecal coliforms and other heterotrophic mesophilic aerobic bacteria (HMAB) isolated in groundwater in the equatorial region of Cameroon (Central Africa). Bacteria were isolated using standard methods. Pathogenic E. coli strains were then identified using haemagglutination and antisera tests. The maximum abundance of HMAB, faecal coliforms and E. coli strains were 4.9 × 10⁶, 5.6 × 10³ and 1 × 10³ colony‐forming units (CFU)/100 mL, respectively. The count of pathogenic E. coli strains reached 3 CFU/100 mL. The counts of commensal and pathogenic E. coli strains underwent temporal and spatial fluctuations. In 21% of sampling sites, the abundance of faecal coliforms was significantly correlated to that of E. coli (P < 0.05). However, the isolated bacterial count was not significantly correlated to that of the pathogenic E. coli strains (P > 0.05). The bacteria abundance dynamics may be impacted by many interacting factors.     

A simple test for differentiation between E. coli and A. aerogenes

An important problem in water quality control is the ability to differentiate between E. coli (faecal) and A. aerogenes (non-faecal) coliforms. To perform this differentiation, a simple test, based on a modification of the selective mFC medium and optimal incubation temperature (37°C) is proposed. Under these specific conditions E. coli bacteria develop into dark blue colonies, whereas A. aerogenes into pink ones. The intermediate coliform bacteria appear greenish-blue or pink, depending on their relation (closeness) to E. coli or A. aerogenes.