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Urban stormwater is regarded as a key input of faecal contamination in receiving water bodies and therefore, a major concern for health risks associated with aquatic recreation. Wastewater leakages, cross connections and overflows, together with faeces washed from surfaces during rainfall events, are possible origins of faecal contamination which enter these water bodies through stormwater drains. This paper applies conceptual models to a case study of the Yarra River estuary to understand the relative importance of fluxes derived from an urban creek and the 219 urban stormwater pipes which drain directly to the estuary as compared with other inputs, such as the Yarra River itself. Existing hydrologic-microorganism models were used for the estimation of the inputs from riverine and urban stormwater fluxes. These predictions were applied as boundary conditions for a new, highly simplified, model which accounts for the transport and survival of faecal microorganisms in the estuary. All models were calibrated using a rich dataset, containing over 2,000 measured Escherichia coli concentrations. Mass balances from the riverine and stormwater models indicate the limited influence of urban stormwater drains on the estuary during dry weather; less than 0.05% to 10% (5th and 95th percentile; median 0.5%) of the total daily E. coli load entering the estuary was derived from urban stormwater drains. While wet weather contributions from stormwater drains could be more significant (2% to 50%; 5th and 95th percentile), the average contribution remained marginal (median 10%). Sensitivity testing of the estuarine microorganism model by switching off stormwater boundary conditions resulted in minimal model efficiency reduction; this may reflect the low average daily contribution from urban stormwater drains. While these results confirm previous studies which show that E. coli loads derived from stormwater drains are dwarfed by other inputs, it is essential to note that these results also demonstrate that some conditions reveal the opposite; high proportions from stormwater are possible when combined with low riverine inputs and high urban rainfall. Furthermore, this study focuses on the overall impacts of direct urban stormwater inputs on the faecal contamination levels within the estuary, and localized impacts would certainly require further investigation. [ABSTRACT FROM AUTHOR]

In the Citadel area of Hue City, drainage systems that include canals and ponds are considerable sources of fecal contaminants to inundated water during the rainy season because canals and ponds receive untreated wastewater. It is important to investigate the characteristics of hydraulics and water pollution in canals and ponds. At the canals and ponds, water sampling was conducted during dry and wet weather periods in order to evaluate fecal contamination and to investigate changes in water pollution caused by runoff inflow. Inundated water was also collected from streets during heavy rainfall. At the canals and ponds, concentrations of Escherichia coli and total coliform exceeded the Vietnamese regulation values for surface water in 23 and 24 out of 27 samples (85 and 89%), respectively. The water samples were categorized based on the characteristics of water pollution using cluster analysis. In the rainy season, continuous monitoring was conducted at the canals and ponds using water depth and electrical conductivity (EC) sensors to investigate the dynamic relationship between water level and water pollution. It is suggested that in the canals, high EC meant water stagnation and low EC signified river water inflow. Therefore, EC might be a good indicator of water flow change in canals. [ABSTRACT FROM AUTHOR]

Odaiba seaside park is one of the most popular waterfronts in Tokyo Bay, but is easily affected by wet weather pollutant loads through combined sewer overflows (CSOs). The monitoring data of Escherichia coli clearly showed high faecal contamination after a rainfall event on 9-11 November 2007. We estimated the amounts of discharge volume and E. coli pollutant loads of urban rivers receiving CSO from rainfall chambers as well as pumping stations and primary effluent discharge. The result suggested that Sumida River and Meguro River were more influential to the Odaiba coastal area than other sources including the nearest wastewater treatment plant. Subsequently, we simulated the dynamic behaviour of E. coli by a three-dimensional (3D) hydro-dynamic and water quality model. The model simulation reproduced that E. coli concentration after the rainfall event increased rapidly at first and later gradually decreased. The simulations with and without inflow pollutant loads from urban rivers suggested that the E. coli concentration can be influenced by the Meguro River just after the rainfall event and Sumida River about 1 week later. From the spatial and temporal distribution of surface E. coli concentration, after at least 6 days from the rainfall event, high faecal contamination spread to the whole of the coastal area. [ABSTRACT FROM AUTHOR]

Hepatitis A virus (HAV) strains found in selected South African (SA) surface waters were characterised to establish what HAV types are circulating in the environment, thus reflecting circulation in the surrounding communities. Surface water samples used for irrigation or domestic purposes, and water samples from the outflow of wastewater plants were collected from six provinces. Viruses were recovered from the samples using a glass wool adsorption-elution method and then further concentrated using polyethylene glycol/sodium chloride precipitation. After automated nucleic acid extraction, samples were analysed for HAV by real-time reverse-transcriptase polymerase chain reaction. HAV strains were genotyped by nucleotide sequence analysis of the capsid gene VP1 and the VP1/P2B junction. HAVs were detected in 76% (16/21) of the surface water samples and in 37% (19/51) of the samples from the wastewater plants. Strains were characterised from 32 of the 35 samples and classified within genotype IB. The presence of genotype IB in the water sources confirms human faecal contamination. Hence, these faecally-contaminated water sources may be a potential transmission route of HAV infection and a potential source of contamination of irrigated fresh produce in SA. [ABSTRACT FROM AUTHOR]

Fluctuation of bacteriophage and Escherichia coli densities in naturally developed riverbed biofilms were investigated for a 1-year period. E. coli ranged from 1,500 to 15,500 most probable number (MPN)/100 mL and from 580 to 18,500 MPN/cm2 in the main channel in the river water and biofilms, respectively. However, the fluctuations were much greater in the tributary, ranging from 0.8 to 100 MPN/100 mL and from 0.3 to 185 MPN/cm2 in water and biofilms, respectively. The fluctuations of coliphages were also greater in the tributary than in the main channel. FRNA phage serotyping results indicated no significant differences in the source type of the fecal contamination in the main channel and tributary sampling stations. Significant correlations between phage groups in biofilms and water were found at both main channel and tributary. It was assumed that natural biofilms developed in the streambed captured and retained somatic phages in the biofilms for a certain period of time in the main channel site. At the location receiving constant and heavy contamination, the usage of phage indicators may provide additional information on the presence of viruses. In the small tributary it may be possible to estimate the virus concentration by monitoring the E. coli indicator. [ABSTRACT FROM AUTHOR]

Urbanization and frequent storms play important roles in increasing faecal bacteria pollution, especially for tropical urban catchments. However, only little information on the faecal bacteria levels from different land use types and the factors that influence bacteria concentrations is available. Thus, the objectives of this study were to quantify the levels and transport mechanism of faecal coliforms (FCs) from residential and commercial catchments. Stormwaters were sampled and the runoff flow rates were measured from both catchments during four storm events in Skudai, Malaysia. The samples were then analysed for FC, biochemical oxygen demand (6005). chemical oxygen demand (COD), total suspended solids (TSS) and ammoniacal-nitrogen (NH3i-N) concentrations. Intra-storm and inter-storm characteristics of FC bacteria were investigated in order to identity the level and transport pattern of EC. The commercial catchment showed significantly higher event mean concentration (EMC) of FC than the residential catchment. For the residential catchment, the highest bacterial concentrations occurred during the early part of stormwater runoff with peak concentrations usually preceding the peak flow. First flush effect was more prevalent at the residential catchment. [ABSTRACT FROM AUTHOR]

Diverse fecal and nonfecal bacterial contamination and nutrient sources (e.g. agriculture, human activities and wildlife) represent a considerable non-point source load entering natural recreational waters which may adversely affect water quality. Monitoring of natural recreational water microbial quality is most often based mainly on testing a set of microbiological indicators. The cost and labour involved in testing numerous water samples may be significant when a large number of sites must be monitored repetitively over time. In addition to water testing, ongoing monitoring of key environmental factors known to influence microbial contamination may be carried out as an additional component. Monitoring of environmental factors can now be performed using remote sensing technology which represents an increasingly recognized source of rigorous and recurrent data, especially when monitoring over a large or difficult to access territory is needed. To determine whether this technology could be useful in the context of recreational water monitoring, we evaluated a set of agroenvironmental determinants associated with fecal contamination of recreational waters through a multivariable logistic regression model built with data extracted from satellite imagery. We found that variables describing the proportions of land with agricultural and impervious surfaces, as derived from remote sensing observations, were statistically associated (odds ratio, OR = 11 and 5.2, respectively) with a higher level of fecal coliforms in lake waters in the southwestern region of Quebec, Canada. From a technical perspective, remote sensing may provide important added-value in the monitoring of microbial risk from recreational waters and further applications of this technology should be investigated to support public health risk assessments and environmental monitoring programs relating to water quality. [ABSTRACT FROM AUTHOR]

Genetic markers derived from Bacteroidaies spp. have been proposed as promising indicators for fecal contamination in the water environment. However, little is known about the persistency of Bacteroidaies spp. 16S rRNA genetic markers in the natural environment, which hampers the precise identification of fecal contamination sources, in this study, the persistency of human-specific Bacteroidales spp. genetic markers in river water was investigated during a 3-week agitation. The copy number of Bacteroidales spp. genetic marker was decreased with agitation time, and was very sensitive to water temperature. After the 3-week agitation, three clones of 18S rRNA gene related to Glaucoma scintillans, Spumella-like flagellate, and Colpidium campylum were acquired. The presence of predators that can prey on target bacteria could also be a critical factor affecting the quantified value of genetic markers. It is very important to take these factors, water temperature and the presence of predator, into account for predicting the fate of genetic markers to accurately identify fecal pollution sources. [ABSTRACT FROM AUTHOR]

WSP technology has been used in Ceará, Northeast Brazil, since middle 1970s. There are presently 96 ponds plants and most of them are comprised by single cells (40%) and series of 3 ponds (35%). They were under loaded due to incomplete house connections to the sewerage network and low per capita wastewater contributions. Highest removal rates of organic material, ammonia and faecal coliform were found in 3 pond series. Faecal coliform removal was in accordance with the literature and series of ponds reached numbers ⩽105 cells/100 ml. In series with 4 and 5 ponds FC was below 103 cells/100 ml. Ammonia removal varied from 30 to 80% and total phosphorus the removal was not significant. An increase in the number of maturation ponds enhances nutrient and coliform removal. Up-grading schemes should be investigated as well as effluent reuse potential. [ABSTRACT FROM AUTHOR]

Performance of the combined process of up-flow anaerobic sludge blanket (UASB) reactor and cascade sponge reactor (CSR) for sewage treatment was studied. UASB-CSR system was operated at HRTs of 24 h, 16 h, and 8 h at an average wastewater temperature of 29°C. It comprises of the most efficient combined process not only for CODT (98.9%), BODT (98.5%), TSS (99.3%), total nitrogen (89.1%), total phosphorus (99.0%), total coliform (99.9%) and fecal coliform (99.9%) removal but also for reducing excess sludge production. Fecal coliform counts were found 23 MPN/100 ml only in final effluents. The effluent quality of the system sufficiently meets the discharged standards which regulate wastewater discharge into drains. The parameters of CSR are closely related to those of the potable water after certain advanced treatment which can be reused in many ways. Moreover, it does not require any external aeration and thus the cost associated with energy and devices required for aeration are cut to zero. [ABSTRACT FROM AUTHOR]

The Sulfate Reduction, Autotrophic Denitrification, Nitrification Integrated (SANI) process has been specially designed to treat saline wastewater. In the process no biological excess sludge is produced. SANI process also has the added advantages of cost and footprint reduction when compared to traditional activated sludge processes. In the SANI pilot plant, the fecal coliform removal efficiency in the sulfate reducing up-flow sludge bed (SRUSB) was found to be 1.4 log, whereas that in the subsequent anoxic and aerobic reactors it was 0.6 and 0.2 log, respectively, leading to a relatively high overall coliform removal of 2.210g. Sulfide was confirmed to be toxic to fecal coliform and the contact time between the sulfide produced and coliform in the SRUSB played an important role in the removal. [ABSTRACT FROM AUTHOR]

As a representative urban stream in Korea, the Gwangju (GJ) stream suffers from chronic fecal contamination. In this study, to characterize levels of fecal pollution in the GJ stream, the monthly monitoring data for seven years (from 2001 to 2007) and the hourly monitoring data from two field experiments were examined with respect to seasonal/daily variations and spatial distribution under wet and dry weather conditions. This research revealed that concentrations of fecal indicator bacteria strongly varied depending on the prevalent meteorological conditions. That is, during the dry daytime, fecal indicator bacteria concentrations decreased due to inactivation from solar irradiation, but rapidly increased in the absence of sunlight, suggesting external source inputs. In addition, bacterial concentrations substantially increased during rainfall events, due probably to a major contribution from combined sewer overflow. The observations in this study can be useful for implementing fecal pollution management strategies and for predicting fecal contamination as a function of meteorological conditions. [ABSTRACT FROM AUTHOR]

In order to understand the current status of rainwater harvesting (RWH) practices in Taiwan's schools, a study was carried out to examine the RWH system performance, water usage, and water quality in these sites. A total of 29 schools in various regions were selected for this investigation, including 7 in the northern, 7 in the central, 8 in the southern, and 7 in the eastern regions of Taiwan. Water quality indicators tested were: pH, temperature, conductivity, oxidation-reduction potential, suspended solid, total organic carbon, fecal coliform, and total coliform. From this study, it was found that RWH systems in these sites generally had two different designs: one that collected rainwater only, and one that collected both rainwater and grey water. From statistical analysis, it was found that water quality indicators such as suspended solids, total organic carbon, and fecal coliform were significantly affected by the water source and site location. Fecal coliforms in most of the sites we studied were high and not qualified for toilet flushing. The average water retention time of 2.4 months was long and considered to be the main reason to cause high fecal coliform counts. Finally, the benefit analysis was conducted to evaluate economic feasibility of rainwater harvesting for these schools. It turned out that 20% of them were able to gain economic benefits from using rainwater. [ABSTRACT FROM AUTHOR]

Faecal contamination sources were identified in coastal areas around the Guerande-Atlantique peninsula using two microbial source tracking (MST) methods: (i) Bacteroidales host-specific 16S rRNA gene markers measured by real-time PCR and (ii) F-specific bacteriophage (FRNAPH) genotyping. Both methods were used on 63 water samples from 7 water courses. HF183 marker and bacteriophage genogroup II (FRNAPH II) were detected in all water samples and in the majority of water samples, respectively, from La Torre stream (W5), Piriac (W2), R2000 (W3) and Mazy (W7) rain water drains, and also detected, less frequently, in Le Nau drain (W4), suggesting contamination by human faecal sources at these sites. These human markers were weakly detected in Pouliguen channel (W6). Furthermore, BacR and bacteriophage genogroup I (FRNAPH I) were also detected, but at lower concentration and frequency. So, site W6 seems to be contaminated by multiple sources, though mainly human. Finally, BacR was detected twice in Pont d'Armes channel (W1), whereas HF183 was not detected. FRNAPH I and II were detected in only 3 out of 12 water samples. Site W1 seems mainly contaminated by animal sources. As a result of our findings, actions were taken to remediate water and shellfish quality. [ABSTRACT FROM AUTHOR]

The occurrence of resistance patterns among wastewater fecal coliforms was determined in the study. Susceptibility of the isolates was tested against 19 antimicrobial agents: aminoglycosides, aztreonam, carbapenems, cephalosporines, b-lactam/b-lactamase inhibitors, penicillines, tetracycline, trimethoprim/sulfamethoxazole, and fluoroquinolones. Additionally the removal of resistant isolates was evaluated in the laboratory-scale wastewater treatment model plant (M-WWTP), continuously supplied with the wastewater obtained from the full-scale WWTP. Number of fecal coliforms in raw (after mechanical treatment) and treated wastewater, as well as in aerobic chamber effluent was determined using selective medium. The selected strains were identified and examined for antibiotic resistance using Phoenix Automated Microbiology System (BD Biosciences, USA). The strains were identified as Escherichia coli (n = 222), Klebsiella pneumoniae ssp. ozaenae (n = 9), and Pantoea agglomerans (n = 1). The isolate of P. agglomerans as well as 48% of E. coli isolates were sensitive to all antimicrobials tested. The most frequent resistance patterns were found for ampicillin: 100% of K. pneumoniae ssp. ozaenae and 41% of E. coli isolates. Among E. coli isolates 12% was regarded as multiple antimicrobial resistant (MAR). In the studied M-WWTP, the applied activated sludge processes reduced considerably the number of fecal coliforms, but increased the ratio of antimicrobial-resistant E. coli isolates to sensitive ones, especially among strains with MAR patterns. [ABSTRACT FROM AUTHOR]

The study used existing indicator bacterial data and a number of physicochemical parameters that can be measured instantaneously to determine if a decision tree approach, especially classification and regression tree, could be used to predict bacterial concentrations in timely manner for beach closure management. Each indicator bacteria showed different tree structures and each had its own significant variables; Dissolved oxygen played an important role for both total coliform and fecal coliform and turbidity was the most important factor to predict concentrations of enterococci for decision tree approaches. Root mean squared error stayed between 5 and 6.5% of the average values of observations; RMSEs from each simulation, 0.25 for total coliform, 0.31 for fecal coliform, and 0.29 for enterococci. Estimations from tree structures would be regarded as a good representation of the actual data. In addition to results of the objective function, RMSE, 77.5% of actual value fell into the 95% of confidence interval of estimations for total coliform concentrations, 60% for fecal coliform concentrations, and 62.5% for enterococci concentrations. The approach showed reliable estimations for the majority of the data processed, although the method did not portray low concentrations of bacteria as well. [ABSTRACT FROM AUTHOR]

Many outbreaks related to swimming pools could have been prevented or reduced if the pool had been well managed and effectively monitored. The aim of this study was to evaluate physicochemical and microbial parameters that can be proposed as an indicator for the safety of swimming pools. A total of 234 water samples, over a 10-month period in 2006-2007, were collected from indoor swimming pools in Isfahan. All water samples were analyzed for physicochemical and microbial parameters including temperature, pH, turbidity, conductivity, free chlorine, heterotrophic plate count (HPC), total (TC) and fecal coliforms (FC), fecal streptococci (FS) Staphylococcus aureus (Sa) and Pseudomonas aeruginosa (Pa). The highest isolation of microbial indicators was for total coliforms (38%) and the lowest for fecal streptococci (3%). The correlation analyses indicated that free chlorine concentration had a significant negative relationship with the heterotrophic bacteria population and total coliforms. Total coliforms presented a significant correlation with the other microbiological indicators. The results clearly showed that the hygienic quality of the swimming pools was dependent on the efficacy of disinfection. Thus, the free chlorine and pH were good operational indices for the quality control of swimming pools and must be maintained in the recommended range to ensure optimal disinfection. The results also showed that TC and HPC were reliable and practical indicators for routine quality surveillance and assessment of the efficiency of the disinfection process and safety of swimming pools. [ABSTRACT FROM AUTHOR]

The Metropolitan Water Reclamation District of Greater Chicago (District) initiated a research study to determine the total numbers and percentages of antibiotic resistant fecal coliform (FC) bacteria in raw sewage (RS) entering and final effluents (FE) discharged from its seven Water Reclamation Plants (WRPs). The density of FC was determined on m-FC agar containing ampicillin (ampR-16μg/ml), gentamycin (genR-8μg/ml), tetracycline (tetR-8μg/ml), or all three antibiotics. The study was primarily undertaken to determine whether secondary sewage treatment at the District WRPs adequately reduces the numbers and percentages of FCampR, FCtetR, FCgenR, FCamp/tet/genR in the FE. The numbers of ampR, tetR, genR, and amp/tet/genR FC observed in RS ranged from 2.0 × 105 to 1.1 × 107, 9.5 × 104 to 2.2 × 106, 95 to 1.5 × 104 and 90 to 9.5 × 103 per 100 mL, respectively. Secondary sewage treatment without disinfection was shown to reduce the number of antibiotic resistant FC by two-three orders of magnitude. The numbers of FCampR, FCtetR, FCgenR, and FCamp/tet/genR observed in non-disinfected FE ranged from 2.0 × 102 to 6.4 × 103, 2.2 × 102 to 4.1 × 103, 9 to <20 and 9 to <20 per 100 mL, respectively. The relative percentages of antibiotic resistant FC observed in FE followed the same trend observed in RS: FCampR > FCtetR > FCgenR > FCamp/tet/genR. Only one FCamp/tet/genR bacteria was found in this study indicating that multiple-antibiotic resistant FC was virtually eliminated by secondary sewage treatment. The results of multivariate regression analysis showed that the percentages of antibiotic resistant FC in the FE from all seven District WRPs were lower than the percentages of these organisms in RS ( p < 0.01). These results support the conclusion that secondary sewage treatment in the District effectively reduces the number of antibiotic resistant FC and that the environments of the District's seven WRPs are not conducive to the propagation or survival of antibiotic resistant fecal coliform bacteria. [ABSTRACT FROM AUTHOR]

Inhibition factors of urea hydrolysis caused by fecal contamination as source of urease were investigated. The urea hydrolysis was described by initial ammonification rate (IAR). Three factors for the inhibition (pH, free ammonia nitrogen (FAN) and salinity) were investigated in this study. It was found that the optimum pH value for the urea hydrolysis was obtained at pH 7 (30°C). Similar results were obtained from pH 5 to pH 8 whereas pH 9 provided a little amount of negative effect on the hydrolysis. Significant effect of the FAN as inhibition factor on the urea hydrolysis was obtained in the urea solution: the hydrolysis was observed within 120 mg-N/l of the FAN level in artificial urea solution with fecal contamination. However in storage process of real urine the urea hydrolysis was observed until the FAN level increased up to 2,000 mg-N/l. Salinity obviously provided negative effect on the urea hydrolysis in stored urine with fecal contamination at 30°C. It was assumed that high concentration of the NaCl (150 g/l) was required to achieve 50% reduction of the IAR. [ABSTRACT FROM AUTHOR]

In order to gain knowledge on the presences of bacteria and viruses in urban waters, the authors started a long-term study on the microbiological quality of urban lakes and rivers in Xi'an, China. In the current study, enteroviruses were chosen as typical viruses and RT-nested PCR was conducted for their detection. Universal primers were designed for simultaneous detection of poliovirus, coxsackievirus, and enterovirus 71 which are the most frequently encountered enteroviruses in China. The RT-nested PCR protocol established in this study showed high sensitivity and specificity. The detection limit was equivalent to 0.038 CCID50 per litre by applying a modified adsorption-elution concentration method. No cross-reactivity was observed using the genome of pathogenic bacteria as of PCR template. The occurrence of enteroviruses was compared with fecal coliform count in a 6-month period from July to December 2006 for the urban waters. As a result, it was noticed that the presence of enteroviruses might not relate to the fecal coliform count so much. Statistical analysis also indicated that there was no significant correlation between the presence of enteroviruses and that of total bacteria, total coliform, and fecal coliform. [ABSTRACT FROM AUTHOR]

Development of efficient techniques to discriminate the sources of E. coli in aquatic environments is essential to improve the surveillance of fecal pollution indicators, to develop strategies to identify the sources of fecal contamination, and to implement appropriate management practices to minimize gastrointestinal disease transmission. In this study the robustness of five different rep-PCR methods, such as REP-PCR, ERIC-PCR, ERIC2-PCR, BOX-PCR and (GTG)5-PCR were evaluated to discriminate 271 E. coli strains isolated from two watersheds (Lakelse Lake and Okanagan Lake) located in British Columbia, Canada. Cluster analysis of (GTG)5-PCR, BOX-PCR, REP-PCR, ERIC-PCR and ERIC2-PCR profiles of 271 E. coli revealed 43 clusters, 35 clusters, 28 clusters, 23 clusters and 14 clusters, respectively. The discriminant analysis of rep-PCR genomic fingerprints of 271 E. coli isolates yielded an average rate of correct classification (watershed-specific) of 86.8%, 82.3%, 78.4%, 72.6% and 55.8% for (GTG)5-PCR, BOX-PCR, REP-PCR, ERIC-PCR and ERIC2-PCR, respectively. Based on the results of cluster analysis and discriminant function analysis, (GTG)5-PCR was found to be the most robust molecular tool for differentiation of E. coli populations in aquatic environments. [ABSTRACT FROM AUTHOR]

Rainstorms can flush large amounts of faecal pollution from land sources into water bodies, threatening, particularly, contact recreation and bivalve shellfish harvest. We quantified the faecal pollution loads of stormflows in the Toenepi Stream, draining a catchment in intensive dairy-farming (Waikato Region, New Zealand). In this stream, as is typical, E. coli concentration peaks well ahead of flow on storm flow hydrographs, which complicates calculation of loads. However, stormflow E. coli concentration correlates with turbidity in the Toenepi Stream, so we used a continuously-recording turbidimeter to estimate 'continuous' E. coli concentrations and thence E. coli fluxes (cfu/s) and loads (cfu). E. coli was measured on 25 out of the 30 (83%) of storm events occurring in the Toenepi Stream in a 12-month period, using an automatic sampler sampling every 2 hrs over stormflow hydrographs for microbial analysis (within 48 hr). E. coli (cfu) yield on individual events tended to increase systematically with event size. The sum of storm-flow exports (occurring 24% of total time) amounted to 95% of the total annual E. coli export from the Toenepi Catchment. The stream exported about 6% of the (expected) total E. coli production in cattle faeces within the catchment. [ABSTRACT FROM AUTHOR]

The study investigates the fate and transport of microorganisms introduced by artificial groundwater recharge at the Nardò fractured aquifer in Salento, Italy. Microbial indicators of faecal contamination, parasitic protozoa (Giardia and Cryptosporidium) and pathogenic bacteria (Campylobacter spp.), were monitored into injected water and groundwater to test the efficiency of the "natural disinfection" into the fractured aquifer. A remarkable decrease of microbial indicators and pathogens was observed suggesting that pathogens removal or inactivation may be possible during water flow in fractured aquifer. The recently described PNA probe CJE195 (Lehtola et al. 2005) was utilised for the rapid and specific detection of Campylobacter spp. by fluorescence in situ hybridization (FISH) after enrichment. FISH results were consistent with those of traditional cultural method (ISO 17995) applied in parallel: time required for Campylobacter identification was reduced of 4 days. [ABSTRACT FROM AUTHOR]

Reactivation or regrowth of fecal coliform bacteria in biosolids has recently become a concern due to knowledge that Class B materials may fail to meet this criterion after storage or even after land application. In this paper, data show the two types of fecal coliform increases that have been characterized: immediate reappearance of large concentrations directly after dewatering; and the rapid, but less immediate, increases that follow dewatering with some biosolids after dewatering. The latter phenomenon is shown to extend over a time period of days prior to gradual decrease in fecal coliform numbers. Modeling shows that anaerobic or fermentative growth cannot simulate the observed growth, but that a straightforward biokinetic model can duplicate the observed conditions if a doubling time of one hour is assumed, which is supported by literature. Thus regrowth cannot be ruled out as the underlying phenomenon. [ABSTRACT FROM AUTHOR]

The objectives of the study were to upgrade sewage sludge to Class A Exceptional Quality biosolids (as defined by US EPA) using an electrokinetics dewatering system. The pathogens monitored were Salmonella spp, and fecal coliforms (FC). Ten bench-scale electrokinetic cells were set up for the disinfection of the following sludges: primary, secondary (attached growth culture and suspended culture), and anaerobically digested sludge. A conditioning liquid was also added to five cells. Blower system to aid in dewatering and drying was used in in four EK cells. Sludge characteristics such as water content, volatile solids content, sulfate and chloride ions concentrations, FC and Salmonella spp. before and after the tests were monitored. The highest total solids content (98% TS) was achieved in the cell with the low voltage gradient, in the presence of the conditioner and with the blower system. An average reduction by 50% of volatile solids was observed. The highest, 11 log-reduction of Salmonella spp. was observed in a cell with anaerobically digested sludge. No fecal coliforms were observed in any of the cells after EK treatment. [ABSTRACT FROM AUTHOR]

This article presents a reliability analysis of 116 full-scale pond systems in Brazil, comprising 73 primary facultative ponds and 43 anaerobic--facultative pond systems. A methodology developed by Niku et al. (1979) is used for the determination of the coefficients of reliability, in terms of the compliance of effluent BOD, COD, TSS and FC to discharge standards or effluent quality targets. The design concentrations necessary to meet the prevailing discharge standards and the expected compliance percentages have been calculated from the coefficients of reliability obtained. The results showed that few units, under the observed operating conditions, would be able to present reliable performances in terms of compliance with the analyzed standards. For the four constituents (BOD, COD, TSS and FC) and both systems (facultative ponds and anaerobic-facultative systems), the variability of the effluent quality was very large, leading to a high variability of the coefficient of variation (CV) and the coefficient of reliability (COR). The effluent quality from the facultative ponds showed a larger distance to both the desired values and the discharge standard values, compared with the anaerobic--facultative systems. [ABSTRACT FROM AUTHOR]

Wet weather urban discharges are responsible for bathing water contamination. The proposal for a revised EU Directive concerning the quality of bathing water imposes significantly more stringent requirements for the management of bathing water quality, with particularly important repercussions on beaches subjected to short-term pollution incidents. The paper reviews the aspects from EU legislation most directly related to the problem of wet-weather discharges, placing special emphasis on the recent revision process of the Directive on bathing water quality, and evaluates the benefits of some potential solutions based on continuous modelling of a combined sewer system. Increasing the sewer system storage capacity or the STP hydraulic capacity may substantially reduce the untreated discharge volumes, but spill frequency reductions under 2 to 3 spill days per bathing season will hardly be achieved. Results show the severe strains that local rainfall patterns would place on compliance with the Commission's proposal for a revised Directive and highlight the importance of the changes introduced in the amended proposal recently approved by the Council, making it less prescriptive if adequate measures are adopted to prevent bathers' exposure to short-term pollution incidents. [ABSTRACT FROM AUTHOR]

Fecal coliform recurrence has been observed at the City of Los Angeles Hyperion Treatment Plant during pilot-scale experiments with a designated thermophilic battery of six anaerobic digesters, while other digesters were still at a mesophilic temperature. Several lab and full-scale experiments indicated the following possible causes of the growth/reactivation of fecal coliforms in post-digestion: a) contamination of thermophilically digested biosolids with mesophilically digested biosolids; b) a large drop in the biosolids temperature between the centrifuges and silos, which could have allowed the reactivation and/or growth of fecal coliforms. These were resolved by the full plant conversion to thermophilic anaerobic digestion and design modifications of the post-digestion train. [ABSTRACT FROM AUTHOR]

The effect of oxidative and thermo-oxidative co-treatment of excess municipal sludge was investigated. A mixture of primary and waste activated sludge was anaerobically treated using two different configurations: i) two stages and ii) a single stage with recycling. Oxidative or thermo-oxidative co-treatment placed in between the reactor or in the recycle line was studied. A two-stage configuration with no co-treatment served as a control and resulted in 50.1% overall solids removal. Compared to the control, an increase in solids removal of 10.8 and 2.7% was observed when oxidative co-treatment was placed between reactors and in the recycle line respectively. When thermo-oxidative co-treatment was placed between the two stages or in the recycle line an increase in solids removal of 25.1 and 26.9% respectively was observed. The performances of the different configurations were also evaluated with parameters such as COD, TKN, ammonia, and fecal coliform concentration. [ABSTRACT FROM AUTHOR]

The 'H2S test' is being advanced for microbiological water quality testing where conventional coliform based methods are impractical or too expensive. It involves ambient temperature incubation of water samples with nutrient formulated to generate hydrogen sulphide when 'faecal' bacteria are present. Recently a WHO review identified several concerns including the limited number of comparative studies, formulation variability, and false positives and negatives. In response we have compared the H2S test's ability to detect and quantify faecal contamination in an aquifer impacted by septic tank leachfields with measurements obtained concurrently using conventional bacterial indicators, coliphages, faecal sterol biomarkers, Cryptosporidium and Giardia. Like these other analytes, H2S testing detected a contamination gradient ranging from high (septic liquid) to moderate (exfiltration zones), to background (e.g. domestic bores), corresponding to indicator removal + dilution by factors >106>>>>>>>>>. Presence/absence tests could not distinguish between heavily and slightly contaminated waters, whereas multi-tube testing (e.g. 10 x 10 mL arrays) did. It was concluded that while the WHO review concerns are justified, the H2S test performance shows promise in sanitary survey work, can be improved by employing an mpn approach and has potential to aid in the protection of source water and identifying contaminated groundwater. [ABSTRACT FROM AUTHOR]

Increasing concern about bathing water quality in Scotland has led to renewed interest in diffuse sources, as well as the already closely monitored municipal sewage effluents and combined sewer overflows (CSOs) that have been the subject of multi-million pound capital expenditure schemes for several years. Early investigations of diffuse sources focused on rural land uses. This paper is an initial effort to consider the possible significance of urban diffuse sources. A review of the potential for diffuse urban sources includes consideration of sewage pollution in surface water sewers, as well as non-human sources such as pigeon and other bird roosts, and faecal material from pets such as dogs and cats. Portobello beach in Edinburgh is the case study selected, because of earlier work done by Scottish Water and SEPA. The Figgate Burn crosses Edinburgh to discharge onto the beach at Portabello, and pollution sources in its catchment are described. Additional information is reported from Dunfermline, where the sewer network has provided examples of three ways in which sewage pollution can occur in urban streams, and also Scottish examples of measures to control some non-human sources (e.g. SUDS). [ABSTRACT FROM AUTHOR]

To ensure optimum quality at Bathing Waters, the control of diffuse sources of bacterial contamination is receiving increasing attention. As part of an initiative to improve the quality of the EU designated bathing waters on the Fylde Coast (North West England), a project was undertaken to quantify the faecal indicator load from birds and assess the significance on water quality. High bird counts are encountered on the Fylde Coast with gulls, feral pigeons and starlings being prominent. The piers at Blackpool make an attractive roost for starlings with numbers peaking at over 30,000 in late summer. Systematic recording of bird numbers and locations was undertaken during 2001/2. Estimates were also made of the daily faecal organism production by the different species. The spatial distribution of faecal organisms from the bird population was statistically linked to synoptic water quality data. This allowed estimates to be made of the contribution from birds to the faecal pollution load at the bathing waters. The work confirmed a statistically significant link between bird populations and water quality with a marked seasonal bias. [ABSTRACT FROM AUTHOR]

Achieving compliance with the mandatory standards of the 1976 Bathing Water Directive (76/160/EEC) is required at all UK identified bathing waters. In recent years, the Fylde coast has been an area of significant investments in 'point source' control, which have not proven, in isolation, to satisfactorily achieve compliance with the mandatory, let alone the guide, levels of water quality in the Directive. The potential impact of riverine sources of pollution was first confirmed after a study in 1997. The completion of sewerage system enhancements offered the potential for the study of faecal indicator delivery from upstream sources comprising both point sources and diffuse agricultural sources. A research project to define these elements commenced in 2001. Initially, a desk study reported here, estimated the principal infrastructure contributions within the Ribble catchment. A second phase of this investigation has involved acquisition of empirical water quality and hydrological data from the catchment during the 2002 bathing season. These data have been used further to calibrate the 'budgets' and 'delivery' modelling and these data are still being analysed. This paper reports the initial desk study approach to faecal indicator budget estimation using available data from the sewerage infrastructure and catchment sources of faecal indicators. [ABSTRACT FROM AUTHOR]

Fecal coliform bacteria are used as indicator organisms for the presence of pathogens. In sludges, it has often been assumed that the counts of fecal coliforms after digestion (where the sludges may also be called biosolids) are representative of the counts when the sludge is disposed or recycled, such as by land application. The possibility has been raised, however, that dewatering processes can lead to increased counts of fecal coliforms and, by inference, human pathogens. This paper presents data from previous studies of this possibility; the results were inconsistent but showed observable increases in fecal coliforms at one treatment plant. Additional studies were then performed at another treatment facility, which showed statistically significant increases in fecal coliform counts after dewatering and two days of aging. The increases exceeded two orders of magnitude and included two centrifuge types and two biosolids types. Artifacts of media type and enumeration method have been excluded, and shearing of the material by commercial blender did not produce the same effects. [ABSTRACT FROM AUTHOR]

A human-impacted watershed was monitored during the dry summer seasons in 2002 and 2003 to investigate the impact of providing access to sewer mains to local village residences. Faecal coliform concentrations were monitored at select sites along the 30-mile stretch of creek, together with faecal streptococci, enterococci and total coliforms. Analysis of the results found that levels of faecal coliforms were inadequate at identifying significant known influxes of human and animal sewage established by sanitary survey. However, the bacterial ratio of atypical colonies to total coliform colonies (AC/TC), obtained from the total coliform membrane filter assay on m-Endo media, correctly indexed human faecal impact of inadequately sewered villages located along the creek. In addition, the AC/TC ratio correctly classified the predominant source of faecal runoff in the creek headwaters as agricultural, and indicated when aged agricultural faecal material was introduced by tributaries. An approach for watershed management that uses the AC/TC ratio in addition to levels of bacteria is proposed. [ABSTRACT FROM AUTHOR]

In this study the assessment of randomly amplified polymorphic DNA (RAPD) analysis was established as a molecular epidemiological tool. RAPD analysis was performed to differentiate faecal Escherichia coli isolates from human and animal sources. E. coli strains (128) were isolated from human and animal faeces (from cattle and sheep). Genomic DNA was extracted and randomly amplified polymorphic DNA-PCR (RAPD-PCR) fingerprinting was performed. Seven arbitrary primers were tested with a view to discriminating between E. coli isolates from humans and E. coli isolates from animals. RAPD profiles were analysed with hierarchical cluster analysis using an unweighted pair group method. RAPD profiles obtained with three of the tested primers (1247, 1290 and 1254) established a distinct differentiation between E. coli isolates from humans and E. coli from animals. Low levels of misclassification and high levels of specificity make RAPD a sensitive, efficient and reliable means of distinguishing closely related strains. [ABSTRACT FROM AUTHOR]

Antibiotic resistance profiling (ARP) is a potentially useful method for distinguishing faecal bacteria according to host source. This phenotypic approach has cost benefits over genotypic methods, but existing protocols are time-consuming and manual data handling is open to human error. A simplified, low-cost approach to the ARP technique was developed that used automated data recording techniques combined with simple statistical analyses to compare isolates of the genus Enterococcus from various faecal sources. An initial battery of 21 antibiotics (at up to four concentrations) was chosen for source discrimination. Images of growth or non-growth in microplate wells were stored as bitmaps and converted to binary data to form a database of known antibiotic resistance profiles. Discriminant function analysis (DFA) showed that the average rate of isolates correctly classified by the database (wastewater vs non-wastewater) was 86%. Once the more discriminating antibiotics and their concentrations had been identified, it was possible to reduce the number of tests from 80 to 18 whilst increasing the number of correctly classified human isolates. ARP could offer a low-cost and rapid means of identifying sources of faecal pollution. As such, the technique may be of particular benefit to developing countries, where water quality may have a significant impact on health and where cost is a major factor when choosing environmental management technology. [ABSTRACT FROM AUTHOR]

The supply of unfiltered disinfected drinking water from Melbourne's fully protected catchments means that the water-quality managers must ensure that the source water poses no public health risk. High turbidity is currently used as a surrogate of pathogens, and harvesting of water is based on its measurement. The work presented here summarises suspended particle and associated pathogen, microbial indicator and faecal biomarker concentrations collected to (a) quantify turbidity in an Australian water supply system and (b) assess the possibility of increasing water harvesting from selected tributaries. Pathogens and microbial indicators were present in low numbers in these source waters; increased turbidity during storm events was not associated with an increase in pathogen concentration. The results confirmed that protected catchments, along with good management, were effective barriers to pathogen contamination. Aesthetic issues still need to be addressed, but no measurable increase in microbiological risk was associated with storm-generated particles. [ABSTRACT FROM AUTHOR]

A survey of the microbiological and chemical quality of water supplies in the Bindura urban and peri-urban area was carried out over a three-year period from January 2000 to July 2003. Bindura is the provincial city of Mashonaland Central, situated 88 km from the national capital, Harare. Large-scale farming and mining activities in the area predispose water bodies to eutrophication and chemical pollutants, raising concerns about the safety of local water supplies. In this study, thermotolerant (faecal) coliform levels, total aerobic bacterial counts and physicochemical profiles were determined for municipal and borehole water as well as water supplies to mining and squatter communities. Although municipal and mining compound water supplies were of satisfactory microbial and chemical quality, borehole water supplies showed a seasonal fluctuation, with higher coliform counts in the wet season from November to March. Stream water supplies to a squatter camp in the peri-urban area consistently recorded coliform levels >1,800/100 mL and total aerobic plate counts of <2.8 x 106 CFU/mL. All cholera incidents recorded in 1999 and 2000 at the Provincial hospital were from peri-urban settlements and surrounding commercial farms while 1,045 to 2,632 cases of dysentery were also reported each year at the provincial hospital during the period 1997-2002. [ABSTRACT FROM AUTHOR]

Details are given of the application of Artificial Neural Networks (ANNs) to predicting the compliance of bathing waters along the coastline of the Firth of Clyde, situated in the south west of Scotland, UK. Water quality data collected at 7 locations during 1990-2000 were used to set up the neural networks. In this study faecal coliforms were used as a water quality indicator, i.e. output, and rainfall, river discharge, sunlight and tidal condition were used as input of these networks. In general, river discharge and tidal ranges were found to be the most important parameters that affect the coliform concentration levels. For compliance points close to the meteorological station, the influence of rainfall was found to be relatively significant to the concentration levels. [ABSTRACT FROM AUTHOR]

The objective was to investigate the potential risk of faecal indicator organism (FIO) bacteriological contamination of river catchments and coastal bathing waters from farm management practices and to develop practices to reduce the risk. A risk assessment on 117 farms was carried out in two river catchments in south-west Scotland. Manure storage facilities, farming practices, field conditions and catchment characteristics were assessed. River samples at 33 locations were regularly taken and analysed for FIOs. Available manure storage capacity and farm management practices are inadequate on a high proportion of farms and FIO contamination of watercourses was likely the result of effluent transported into watercourses due to non-collection or poor containment. In addition, surface run-off or leaching following land application of manure or intensive stocking in adverse conditions was a high risk on up to 50% of farms. The concentrations of FIOs in the streams of two sub-catchments with high livestock intensity was 4 to 8 times higher compared to the two sub-catchments which had a low livestock intensity. The majority of potential risks of agricultural pollution to watercourses may be eliminated through improved manure and dirty water management, forward planning of manure spreading activities and improved operational procedures. [ABSTRACT FROM AUTHOR]

The removal of sanitary indicator bacteria (total coliforms, faecal coliforms, and faecal streptococci) was studied in an experimental constructed wetland system consisting of (1) a 2-m³ threechamber sedimentation tank, (2) a 5 m² vertical flow constructed wetland, (3) a filter-unit with calcite aimed at removing phosphorus, and (4) a 10 m² vertical flow constructed wetland. The indicator bacteria were enumerated before and after each unit of the wetland system during four monitoring episodes with different loading conditions. At a hydraulic loading rate of 520-1,370 mm/d, the first-stage vertical flow beds removed about 1.5 log-units of total coliforms, 1.7 log-units of faecal coliforms and 0.8 log-units of faecal streptococci. In the second stage bed receiving lower loadings both in term of concentration and quantity (260-690 mm/day), the eliminations were lower. It was not possible in the present study to identify any seasonal effects, but no measurements were done during summer. Recycling of treated effluent back to the sedimentation tank did not affect elimination. Area-based rate constants for the vertical flow wetland receiving effluent from the sedimentation tank averaged 3.2 m/d for total coliforms, 3.3 m/d for faecal coliforms and 2.1 m/d for faecal streptococci. The rate constants depended on loading rates. It is suggested that filtration is a major removal mechanism for bacterial indicator organisms in vertical flow constructed wetland systems. [ABSTRACT FROM AUTHOR]

In order to move towards optimising wastewater treatment performance by vertical down-flow reed beds, user and installer demands were applied to design, resulting in the "compact vertical flow reed bed" (CVF bed). Performance data are presented for the two years since commissioning a CVF bed and pond system serving eight residents. Particular emphasis was placed on investigating oxygen transfer rate and susceptibility to hydraulic overloading. Average percentage concentration reduction effected by single passage through the bed exceeded 97% for suspended solids and biochemical oxygen demand, and 90% for ammoniacal nitrogen and total Kjeldahl nitrogen. The occurrence of nitrification and denitrification (up to 58%) within the same bed was clearly indicated. Percentage ortho-phosphate removal averaged 92% over the first 17 months' operation and thereafter fell to approximately 45%. Faecal coliform density underwent an almost four log reduction. Oxygen transfer rate within the reed bed was between 28-36 gO2/m².d. Normal operation was maintained until six times dry weather hydraulic load rate was exceeded, at which point surface flooding occurred. The capacity of a single vertical flow reed bed to achieve effective treatment of domestic sewage was demonstrated, with no requirement for reduced load rates, promising substantial advantages over established approaches. [ABSTRACT FROM AUTHOR]

Wetlands are in use as adjuncts to wastewater treatment lagoons at many north temperate locations. Performance data for 21 systems show median removals of 67, 61, 61, 48 and 99.8% for TSS, BOD, NH4-N, TP and fecal coliforms, respectively. Hydraulic loading rates range from 0.14 to 55 cm/d, areas from 0.02 to 200 ha, and latitudes from 30 to 54°N. Calibrations of first order models with temperature dependence show that rate constants vary from seasonal dependence at low loadings to temperature dependence at high loadings for ammonia. Phosphorus rate constants display seasonal, not temperature effects. BOD and TSS are not affected by season. Wetland rate constants are larger than those for lagoons for all constituents. The optimal winter operating strategy, if hydraulics allow, is partial storage during frozen months, coupled with winter use of the wetlands. The use of FWS wetlands for polishing lagoon effluents is cost effective when land availability is not drastically constrained. Many systems have been in operation long enough to demonstrate sustainable long-term performance. Infiltration beds are potentially a valuable addition to ponds and wetlands. [ABSTRACT FROM AUTHOR]

The paper uses the technique of Monte Carlo simulation in order to investigate the sensitivity to the Dispersion Number (d) of the effluent coliform concentration from facultative and maturation ponds. The Dispersion Number is one of the coefficients used in the dispersed-flow model for ponds. Initially, four empirical equations available in the literature for the estimation of d were compared, using the results from 1,000 runs of the Monte Carlo simulation. A second different set of Monte Carlo simulations (1,000 runs) was undertaken, allowing a sensitivity analysis of d, in conjunction with other coefficients and input data used in the design of facultative and maturation ponds (e.g., population, wastewater flow, coliform removal coefficient and others). The results of the simulations suggest that, when considering the high level of uncertainty in all input variables used in the design of the ponds for coliform removal, the Dispersion Number d does not present a greater influence in the model prediction, compared with the other input variables. Based on these considerations, it is likely that, for design purposes, simple models for the prediction of d can be used, without significantly affecting the estimation of the effluent coliform concentration, considering the existing uncertainty in all other input variables. [ABSTRACT FROM AUTHOR]

This paper reports the impact of four sequential maturation pond interventions on the removal of thermotolerant "faecal" coliform bacteria at a full scale WSP system in tropical Colombia. Each intervention was designed to increase hydraulic retention time and was followed by continuous physico-chemical logging and meteorological monitoring, and simultaneous tracer studies to define hydraulic retention time, flow paths and dispersion. Inlet and outlet monitoring showed that, primarily due to hydraulic short-circuiting, the open maturation pond only achieved a 90% reduction in thermotolerant "faecal" coliforms. By contrast, an in-pond batch decay rate study for thermotolerant faecal coliforms showed that a 1 log (90%) reduction was achieved every 24 hours for 4 days at 26°C, so that the maximum theoretical efficiency would be a 2.6 log reduction (99.7%) if hydraulic efficiency was perfect for plug flow. The second intervention was the conversion of the maturation pond to a parallel series of three open channels to attempt to control shortcircuiting and convert to plug flow. The channels raised performance to 96%. The introduction of top baffles, at the end of the first and second channels, to attempt to further reduce the effect of surface and sub-surface flow on short-circuiting, actually reduced performance to 92.64%, and were removed. The final intervention, a 2.1 m high wind break around the maturation channels raised efficiency to 98.13%; this performance is almost a half log (0.47) greater than the efficiency (95.1%) predicted from Marais' equation for a completely mixed reactor, and 0.77 log greater than recorded in the open pond. The results have fundamental implications for improving WSP efficiency, for meeting re-use guidelines, for savings in land area and improvement of design of WSPs; they also highlight short-comings in the indiscriminate use of the Marais design equation for faecal coliform removal. [ABSTRACT FROM AUTHOR]

Parasite removal and low cost systems for wastewater treatment have become increasingly important requirements in developed and developing countries to safeguard public health from wastewater-associated intestinal diseases. Pilot and field-scale ponds and wetlands in Brazil and Egypt have been investigated for the fate and removal of eggs of human intestinal parasites from domestic wastewater. In northeast Brazil, parasite removal was investigated for a series of five waste stabilisation ponds treating raw wastewater. In Egypt, parasite removal was studied for Gravel Bed Hydroponic constructed wetlands treating partially treated wastewater. Influents to ponds and wetlands contained a variety of parasite helminth eggs (e.g. Ascaris, hookworm, Trichuris, and Hymenolepis spp.). The ponds consistently removed parasite eggs though rate of removal by individual ponds may have been related to influent egg numbers and extent of short-circuiting. Parasite eggs were reduced on average by 94% and 99.9% in the anaerobic and facultative ponds respectively. No eggs were found in effluent from the second maturation pond. In the wetland system, parasite removal varied with reedbed length. The majority of parasite eggs were retained within the first 25 m. Parasite eggs were reduced on average by 98% after treatment in 50 m beds and completely removed after treatment in 100 m beds. [ABSTRACT FROM AUTHOR]

During treatment in wastewater stabilization ponds (WSPs) many pathogens, in particular helminth eggs, are concentrated in the sludge layer. Because periodic removal of the sludge is often required, information is needed on the concentrations and inactivation of pathogens in the sludge layer to evaluate the public health risk they pose upon removal of the sludge. In this paper, previous reports on the sludge concentrations of various pathogen indicator organisms and helminth eggs are reviewed and results from our own recent experiments are reported. The advantages and disadvantages of several methods for studying inactivation in the sludge layer are discussed, as well as implications for the management of WSP sludge. In our recent experiments, which were conducted at three WSPs in central Mexico, sludge cores, dialysis chambers, and batch experiments were used to measure the inactivation rates of fecal coliform bacteria, fecal enterococci, F+ coliphage, somatic coliphage, and Ascaris eggs. The first-order inactivation rate constants were found to be approximately 0.1, 0.1, 0.01, 0.001, and 0.001 d-1, respectively. The concentrations of all the organisms were found to vary both vertically and horizontally in the sludge layer; therefore, to determine the maximum and average concentration of organisms in the sludge layer of a WSP, complete sludge cores must be collected from representative locations throughout the pond. [ABSTRACT FROM AUTHOR]

The survival of bacterial and viral pollution indicators and Salmonella in urban wastewaters under freezing conditions (-14°C for up to 60 days) is reported. Presumptive, total and faecal coliforms (PC, TC, FC), salmonellae and coliphages were tested. The dynamics of somatic coliphage (E. coli C) and F-pili specific coliphage inactivation were compared at 4°C and 25°C over various run times. On freezing of the wastewater, it was found that PC, TC and FC showed a first rapid phase (days) of inactivation followed by a slower second phase (up to 4 weeks) and then stabilisation at between 1-10% of the initial population size, depending on the wastewater sample used. Salmonella spp. were detectable in 0.1 ml of raw wastewater and were still detected up to 2 days after freezing but none were detected in 100 ml samples after 4, 42 and 60 days, although microbiologically similar but antigenically different forms were found. Viral indicators of pollution showed a slow but constant decrease in viability during the first month but then stabilised at between 10-20% survivors (10% in somatic E. coli C phages, 15.8% in somatic Salmonella phages and 17.9% in F-pili specific coliphages). Using electron microscopy, no difference in susceptibility to freezing could be detected with respect to morphological phage types, which were either small icosahedral particles or complex tailed phages. The study of viral indicators at 4°C versus 25°C showed a higher survival of the various coliphages over time at 4°C. F-pili specific leviviridae were particularly susceptible to the antiviral factors at 25°C and no viable units per ml were detected after one month at that temperature, whereas somatic coliphages were detected in higher numbers after this period, especially at 4°C. [ABSTRACT FROM AUTHOR]

Faecal coliform removal in stabilisation ponds is highly dependent on shortest water retention times. Tracer tests have been performed in a 3,300 m2 and 1.0 m deep pond, located in Southern France, to measure the retention times and bring light on the main influencing factors and mechanisms. Tracer concentrations were monitored at the outlet and 60 locations within the pond -- at the surface, mid depth and the bottom of the water column. Pond water temperatures were measured at different depths and locations, together with pH, DO and redox potential. Wind velocity and rainfall were recorded. Water quality was monitored at the inlet, outlet and within the pond. Water retention times were shown to be strongly affected by weather conditions. Windy periods appeared to favour mixing regardless of the season. In sunny periods of spring and summer, a clear stratification was observed during daytime and vanished gradually during the night, suggesting alternation of mixed and stratified hydrodynamic patterns. This alternation was shown to influence microorganism contents within and at the outlet of the pond. Accurate prediction of shortest water retention times and disinfection performance requires 3D unsteady state fluid dynamic models that are able to take the influence of wind and water temperature distribution into account. [ABSTRACT FROM AUTHOR]