Raw Municipal Sewage Research Articles

Elimination of Vibrio Cholerae from Raw Sewage Using Chlorella Vulgaris: A Case of Chegutu Waste Reticulation, Zimbabwe

The research was aimed at eliminating Vibrio cholerae from raw sewage collected from home spills of Chegutu, Zimbabwe. An experimental approach was used in which homogenized raw sewage, inoculated with Chlorella vulgaris culture was distributed equally into three tanks and left to stand for three weeks. Samples were extracted from the three tanks and tested for the presence of Vibrio cholerae and physico-chemical parameters once in seven days. Results showed a continuous decrease in the quantities of Vibrio cholerae as well as physico-chemical parameters. Vibrio cholerae was totally eliminated from the sewage within 21 days. Chlorella vulgaris can be used as a bioremediation agent to eliminate the Vibrio cholerae from sewage. The research recommends that the prototype designed from this research could be used at a large scale in the elimination of Vibrio cholerae in Municipal raw sewage.

Occurrence of extended-spectrum betalactamase (ESBL) and carbapenemases among ampicillin-resistant enterobacteriales recovered from a municipal raw sewage in Minas Gerais, Brazil

Introduction: The capacity of resistance to β-lactam among enterobacteriales is notable, mainly into water environment. Herein, many species of this family have the ability to carrier and produce β-lactamases enzymes, such as extended-spectrum β-lactamases (ESBLs) and carbapenemases. However, contrary to clinical settings, where the distribution of resistant bacteria is well documented, the evidence of resis-tant pathogens in the domestic sewage has been little explored, especially in Brazil. Thus, we aimed to investigate the occurrence of ESBL and carbapenemases between ampicillin-resistant enterobacteriales recovered from a municipal raw sewage in Minas Gerais, Brazil. Methods: Enterobacteriales were isolated from sewage samples on MacConkey agar supplemented with ampicillin. Species identifica-tion was performed by biochemical and morphological methods and the resistance profile determined by the Kirby-Bauer test. The production of ESBL and carbapen-emase was investigated in all isolates by phenotypic tests. Results and discussion:A total of 45 species of enterobacteriales resistant to ampicillin were recovered (37 Escherichia coli, four Klebsiella pneumoniae, and one Klebsiella oxytoca, Citrobacter freundii and Pantoea agglomerans). Most isolates showed a high β-lactam suscep-tibility profile (14/45, 31.1 %), however E. coli with decreased susceptibility to imipenem was detected (2/37; 2.7 %). ESBL-positive isolates were mostly identified as E. coli (10/45; 22.2 %), but no isolates were positive carbapenemase. Conclu-sion: Domestic sewage is an important source of β-lactams resistant determinants in Brazil.

The use of a natural substrate for immobilization of microalgae cultivated in wastewater

The methods of separation of microalgae has a significant impact in the economic aspects of their cultivation. In this study, pine bark was used as a substrate for immobilization of microalgal biomass cultivated in raw municipal sewage. The experiment was conducted in cylindrical photobioreactors (PBRs) with circulation of wastewater. Biomass was cultivated for 42 days. After that time, abundant growth of the biofilm with microalgae on the surface of pine bark as well as improvement of the quality of treated sewage were observed. The efficiency of removal of nutrients from wastewater was 64–81% for total nitrogen and 97–99% for total phosphorus. Moreover, the concentration of suspended solids in sewage was reduced, which resulted in a decrease in turbidity by more than 90%. Colorimetric analysis and Volatile Matter (VM) content in the substrate showed a decrease in the Higher Heating Value (HHV) and concentration of VM due to the proliferation of biofilm.

Molecular Basis for Lytic Bacteriophage Resistance in Enterococci.

ABSTRACTThe human intestine harbors diverse communities of bacteria and bacteriophages. Given the specificity of phages for their bacterial hosts, there is growing interest in using phage therapies to combat the rising incidence of multidrug-resistant bacterial infections. A significant barrier to such therapies is the rapid development of phage-resistant bacteria, highlighting the need to understand how bacteria acquire phage resistance in vivo. Here we identify novel lytic phages in municipal raw sewage that kill Enterococcus faecalis, a Gram-positive opportunistic pathogen that resides in the human intestine. We show that phage infection of E. faecalis requires a predicted integral membrane protein that we have named PIPEF (for phage infection protein from E. faecalis). We find that PIPEF is conserved in E. faecalis and harbors a 160-amino-acid hypervariable region that determines phage tropism for distinct enterococcal strains. Finally, we use a gnotobiotic mouse model of in vivo phage predation to show that the sewage phages temporarily reduce E. faecalis colonization of the intestine but that E. faecalis acquires phage resistance through mutations in PIPEF. Our findings define the molecular basis for an evolutionary arms race between E. faecalis and the lytic phages that prey on them. They also suggest approaches for engineering E. faecalis phages that have altered host specificity and that can subvert phage resistance in the host bacteria.

Comparative analysis of the digestibility of sewage fine sieved fraction and hygiene paper produced from virgin fibers and recycled fibers

Sewage fine sieved fraction (FSF) is a heterogeneous substrate consisting of mainly toilet paper fibers sequestered from municipal raw sewage by a fine screen. In earlier studies, a maximum biodegradation of 62% and 57% of the sewage FSF was found under thermophilic (55°C) and mesophilic (35°C) conditions, respectively. In order to research this limited biodegradability of sewage FSF, this study investigates the biodegradation of different types of cellulosic fibers-based hygiene papers including virgin fibers based toilet paper (VTP), recycled fiber based toilet paper (RTP), virgin pulp for paper production (VPPP) as a raw material, as well as microcrystalline cellulose (MCC) as a kind of fiberless reference material. The anaerobic biodegradation or digestibility tests were conducted under thermophilic and mesophilic conditions. Results of the experiments showed different biomethane potential (BMP) values for each tested cellulose fiber-based substrate, which might be associated with the physical characteristics of the fibers, type of pulping, presence of lignin encrusted fibers, and/or the presence of additive chemicals and refractory compounds. Higher hydrolysis rates (Kh), higher specific methane production rates (SMPR) and shorter required incubation times to achieve 90% of the BMP (t90%CH4), were achieved under thermophilic conditions for all examined substrates compared to the mesophilic ones. Furthermore, the biodegradability of all employed cellulose fiber-based substrates was in the same range, 38–45%, under both conditions and less than the observed FSF biodegradability, i.e. 57–62%. MCC achieved the highest BMP and biodegradability, 86–91%, among all cellulosic substrates.

High-rate thermophilic bio-methanation of the fine sieved fraction from Dutch municipal raw sewage: Cost-effective potentials for on-site energy recovery

Sieving of Dutch raw sewage over a 350μm screen, produces a cake layer called fine sieved fraction (FSF), an energy-rich material that contains mainly cellulosic fibers originating from toilet paper. The FSF biomethane potential (BMP) was studied under both mesophilic (35°C) and thermophilic (55°C) conditions, whereas the stability of the fed-batch digesters at both 35°C and 55°C was researched by varying the inoculum to substrate ratios (RI/S: 0.5–15). Results clearly showed advantages of thermophilic conditions over mesophilic conditions at all tested RI/S. Stable digestion was even possible at an RI/S of 0.5 at 55°C.Following the results of the batch tests, a compact high loaded thermophilic digester for on-site energy recovery from FSF was proposed. Based on the results of the study, high biogas production rates at high organic loading rates (OLRs) were predicted. In the energy balance calculations, surplus heat production from combined heat and power (CHP) was utilized to dry the digestate sludge before transportation to an incineration plant or for use in pyrolysis or gasification processes. Overall results showed the potential of generating 46% of the required energy for wastewater treatment via high rate FSF digestion and subsequent conversion of the bio-methane into electricity and heat. The net recoverable energy from fine sieving, anaerobic digestion of FSF, dewatering of digestate sludge and drying of dewatered digestate sludge amounted 287MJ/ton FSF and 237kWh electric/ton FSF at 23% TS.

High prevalence of type 41 and high sequence diversity of partial hexon gene of human adenoviruses in municipal raw sewage and activated sludge.

This study was aimed to assess seasonal/geographical distribution and sequence diversity of partial hexon gene for human adenoviruses (HAdVs) within raw sewages (RS) and activated sludges (AS). Assessments were based on high-throughput sequencing (HTS) for polymerase chain reaction (PCR)-amplified 128-bp partial hexon gene fragments and followed by principal coordinate analyses (PCoA) for revealed sequences. Sequencing results showed that the majority of sequences (>90%) for the RS or AS samples were identical to HAdV type 41 of species F, while rest of few sequences belonged to HAdV species-D and -C were only occurred rarely without significant seasonal/geographical variation. The partial hexon genes were highly diverse as many sequence types and operational taxonomic unit groups were noticed among the matched sequences. This study demonstrated that HAdV-41 was constantly appeared in the RS and AS samples from Taiwan throughout the year without significant seasonal or geographical variations; but, had high sequence diverse noticed for the 128-bp partial hexon gene fragments. High-throughput-sequencing results provided better insights of HAdV distribution and genetic diversity for raw sewage and AS samples allowing some probable biases for cloning-sequencing approach to be defeated and further providing public health awareness regarding viral-contaminated sewages or sludges.

Digester performance and microbial community changes in thermophilic and mesophilic sequencing batch reactors fed with the fine sieved fraction of municipal sewage

This study investigates the start-up and operation of bench-scale mesophilic (35 °C) and thermophilic (55 °C) anaerobic sequencing batch reactor (SBR) digesters treating the fine sieved fraction (FSF) from raw municipal sewage. FSF was sequestered from raw municipal wastewater, in the Netherlands, using a rotating belt filter equipped with a 350 micron mesh. For the given wastewater, the major component of FSF was toilet paper, which is estimated to be 10–14 kg per year per average person in the western European countries. A seven months adaptation time was allowed for the thermophilic and mesophilic digesters in order to adapt to FSF as the sole substrate with varying dry solids content of 10–25%. Different SBR cycle durations (14, 9 and 2 days) were applied for both temperature conditions to study methane production rates, volatile fatty acids (VFAs) dynamics, lag phases, as well as changes in microbial communities. The prevailing sludge in the two digesters consisted of very different bacterial and archaeal communities, with OP9 lineage and Methanothermobacter being pre-dominant in the thermophilic digester and Bacteroides and Methanosaeta dominating the mesophilic one. Eventually, decreasing the SBR cycle period, thus increasing the FSF load, resulted in improved digester performances, particularly with regard to the thermophilic digester, i.e. shortened lag phases following the batch feedings, and reduced VFA peaks. Over time, the thermophilic digester outperformed the mesophilic one with 15% increased volatile solids (VS) destruction, irrespective to lower species diversity found at high temperature.

Performance of a single stage vertical flow constructed wetland system treating raw domestic sewage in Brazil

This study investigated the behaviour of two intermittently fed vertical flow constructed wetlands (one planted with Tifton 85 and the other unplanted) working in parallel, treating raw municipal sewage in Brazil for a population equivalent around 100 inhabitants. Based on a monitoring programme of over 2 years, the following items were evaluated: influence of batch frequency and the presence of Tifton 85 on the wetlands performance in terms of several physico-chemical and biological constituents. The unit with plants performed better than the one without, indicating a positive influence of the presence of plants. More attachment by total and volatile solids and larger amount of bacteria involved in the nitrogen cycle were observed in the planted filter medium, which can explain its higher nitrification and solids removal. The application of a smaller influent volume with a higher batch frequency improved the performance of both units. No signs of medium clogging have been observed in both units. The system simplicity and the good removal efficiency of organic matter, suspended solids, ammonia and helminth eggs indicate its high applicability in small communities in developing countries such as Brazil.

Increased Levels of Multiresistant Bacteria and Resistance Genes after Wastewater Treatment and Their Dissemination into Lake Geneva, Switzerland

At present, very little is known about the fate and persistence of multiresistant bacteria (MRB) and their resistance genes in natural aquatic environments. Treated, but partly also untreated sewage of the city of Lausanne, Switzerland is discharged into Vidy Bay (Lake Geneva) resulting in high levels of contamination in this part of the lake. In the present work we have studied the prevalence of MRB and resistance genes in the wastewater stream of Lausanne. Samples from hospital and municipal raw sewage, treated effluent from Lausanne’s wastewater treatment plant (WTP) as well as lake water and sediment samples obtained close to the WTP outlet pipe and a remote site close to a drinking water pump were evaluated for the prevalence of MRB. Selected isolates were identified (16S rRNA gene fragment sequencing) and characterized with regards to further resistances, resistance genes, and plasmids. Mostly, studies investigating this issue have relied on cultivation-based approaches. However, the limitations of these tools are well known, in particular for environmental microbial communities, and cultivation-independent molecular tools should be applied in parallel in order to take non-culturable organisms into account. Here we directly quantified the sulfonamide resistance genes sul1 and sul2 from environmental DNA extracts using TaqMan real-time quantitative PCR. Hospital sewage contained the highest load of MRB and antibiotic resistance genes (ARGs). Wastewater treatment reduced the total bacterial load up to 78% but evidence for selection of extremely multiresistant strains and accumulation of resistance genes was observed. Our data clearly indicated pollution of sediments with ARGs in the vicinity of the WTP outlet. The potential of lakes as reservoirs of MRB and potential risks are discussed.

Evaluation of case-based design principles in the design of Soche wastewater treatment plant, Blantyre, Malawi

This paper evaluates case-based design principles in the design of Soche wastewater treatment works (WWTW) in the city of Blantyre, Malawi. According to the Case Study Manager in the ED-WAVE tool, a similar case to both dry season and wet season conditions of Soche plant is Municipal Case 6 in Greece. The raw material at Municipal Case 6 in Greece is raw municipal sewage where the typical wastewater parameters are BOD5, and TSS. The treatment target is BOD5, and TSS reduction. The study confirmed the practical use of case-based design principles in the design of wastewater treatment systems, where after encountering a new situation; already collected decision scenarios (cases) are invoked and modified in order to arrive at a particular design alternative. What is necessary, however, is to appropriately modify the case arrived at through the Case Study Manager in order to come up with a design appropriate to the local situation taking into account technical, socio-economic and environmental aspects.

EFFECTS OF MUNICIPAL SEWAGE ON THE GROWTH PERFORMANCE OF CASUARINA EQUISETIFOLIA (FORST. & FORST.) ON SANDY SOIL OF EAST COAST AT KALPAKKAM (TAMIL NADU, INDIA)

Municipal sewage both untreated and treated, that pollutes the water bodies was used growing Casuarinas ( Casuarina equisetifolia Forst. & Forst.), an exotic bio-shield tree species on sandy soil at Kalpakkam on the East Coast of Indian peninsula; it may help in reducing aquatic pollution as well as in preventing the high tides like Tsunami. Significant increase in growth performance in plant-height, branches, root length and the biomass was recorded in the saplings irrigated with untreated municipal raw sewage (RS) and treated sewage (TS) compared to that irrigated with unpolluted potable water (PW) over a period of 13 months, October 2005 to October 2006. These growth parameters showed close relationship with the nutrient contents of municipal RS, TS and PW, the former being characterized by relatively higher pH, electrical conductivity ( µs/cm), total dissolved solids, total suspended solid, total hardness, chloride, sulphate, biochemical oxygen demand, chemical oxygen demand, calcium, magnesium, sodium, potassium, bicarbonates, total alkanity, nitrate, phosphate and carbonates (mg/l) compared to that of the TS and PW indicating profound influence of municipal sewage on the plant growth.

Control of sulfide in sewer systems by dosage of iron salts: Comparison between theoretical and experimental results, and practical implications

Removal of sulfide species from municipal sewage conveyance systems by dosage of iron salts is a relatively common practice. However, the reactions that occur between dissolved iron and sulfide species in municipal sewage media have not yet been fully quantified, and practical application relies heavily on empirical experience, which is often site specific. The aim of this work was to combine theoretical considerations and empirical observations to enable a more reliable prediction of the sulfide removal efficiency for a given dosing strategy. Two main questions were addressed, regarding the dominant sulfur species that results from the oxidation of sulfide by Fe(III) and the dominant precipitation reaction between Fe(II) and sulfide species. Comparison of thermodynamic prediction obtained by an equilibrium chemistry-based computer program (MINEQL+) with experimental results obtained by dosing ferrous salts showed that the product of precipitation is FeS under all operational conditions tested. Regarding the reaction between ferric salts and sulfide species, analysis of thermodynamic data suggested that the dominant product of sulfide oxidation under typical pe/pH conditions prevailing in municipal raw wastewater is SO 4 2−. However, comparison between sulfide removal in laboratory experiments conducted with multiple samples of raw municipal sewage with a varying composition, and the prediction of MINEQL+ showed the main sulfide oxidation product to be S 0. In order to reduce sulfide in sewage to < 0.1 mgS/l a minimal molar ratio of around 1.3 Fe to 1 S should be applied when ferrous salts are used, as compared with a minimal ratio of 0.9 Fe to 1 S required when ferric salts or a mixture of ferrous and ferric salts (at a 2 Fe(III) to 1 Fe(II) ratio) are used. It appears that the high Fe to S(-II) ratios often recommended in practice can be reduced considerably by applying tight in-line control.

Removal of nitrogen from wastewater for reusing to boiler feed-water by an anaerobic/aerobic/membrane bioreactor

Abstract The innovative process anaerobic/aerobic/membrane bioreactor (A/O/MBR) was developed to enhance pre-denitrification without the energy consumption of the recirculation pump for reusing wastewater to boiler feed-water. The performance of this bioreactor was investigated. Firstly, the septic tank wastewater with low ratio of COD/TN was disposed by a dynamic membrane bioreactor (DMBR). It was found that, although the high concentration of NO 2 − –N in the effluent implied the potential ability of DMBR to realize shortcut nitrification and denitrification, the effluent of single DMBR was difficult to reach the criteria of reusing to boiler feed-water. Then, the process A/O/DMBR in disposing the septic tank wastewater was studied. The results indicated that this process not only accomplished the removal of 91.5% COD, 90.3% NH 4 + –N and 60.2% TN, but also successfully realized pre-denitrification without additional recirculation pump. At last, based on the A/O/DMBR, a pilot plant A/O/MBR was built to dispose the municipal raw sewage. In the stable operation period, the average removal efficiencies for COD, NH 4 + –N, TP and turbidity reached 90%, 95%, 70% and 99%, respectively. During the tested HRT run of 9.0 h, the effluent of COD, NH 4 + –N, TP and turbidity was about 10 mg/L, 3 mg/L, below 1 mg/L and 1.2 NTU, respectively, which reached the criteria of the boiler feed-water in China.

Occurrence of virulence genes associated with enterohemorrhagic Escherichia coli in raw municipal sewage

Municipal sewage influent was screened for the presence of the virulence genes encoding Shiga-like toxins SLT-I and SLT-II ( slt-I and slt-II) and intimin ( eaeA) and those involved in biosynthesis of O157 ( rfbE) and H7 ( fliC) antigens by multiplex PCR to simultaneously identify the enterohemorrhagic Escherichia coli (EHEC) O157:H7 and its virulence factors in a single reaction. The screening was carried out monthly from October 2004 to September 2005. Direct PCR analysis using total DNA from sewage concentrate showed the presence of at least one virulence gene in 100% samples ( n = 12). Sixty six percent of these samples were also positive for rfbE (O157) gene and fliC (H7) gene. The PCR amplification of these genes was possible when the concentration was above 20 cells ml −1. From the multiplex PCR of the isolates following plating on Cefixime-Tellurite Sorbitol MacConkey (CT-SMAC) agar to detect non-sorbitol fermenting (NSF) colonies ( n = 600), one E. coli strain carrying slt-II gene and two strains of E. coli O157:H7 carrying slt-I were detected. The results show that municipal sewage represents a potential reservoir of EHEC. CT-SMAC agar was proved to have limited E. coli O157:H7 selectivity and only 0.005% (3/600) sensitivity for sewage samples due to the high frequency (43%) of NSF strains in sewage. The enrichment of sewage sample in modified E. coli broth (mEC) increased the sensitivity of PCR resulting in the clearer amplification of five genes. Amplification of target cell type in mEC broth implied that EHEC were present in sewage in a culturable and hence potentially infectious state. However, pre-enrichment did not affect the selectivity of CT-SMAC because frequency of NSF colonies remained the same as that obtained without enrichment. The study, therefore, underscores the need for more sensitive screening techniques that can be routinely employed for the regular monitoring of sewage influent.

Feasibility study of a pilot-scale sewage treatment system combining an up-flow anaerobic sludge blanket (UASB) and an aerated fixed bed (AFB) reactor at ambient temperature

A feasibility test of a 17 m 3-pilot-scale sewage treatment system was carried out by continuous feeding of raw municipal sewage under ambient temperature conditions. The system consisted of a UASB and an aerated fixed bed reactor. Some of the effluent from the fixed bed reactor was returned to the UASB influent in order to provide a sulfate source. The total BOD of 148–162 mg l −1 in the influent was reduced to a more desirable 11–25 mg l −1 in the final effluent. The levels of methane-producing activity from acetate and H 2/CO 2 gas at 10 °C were only 2% and 0% of those at 35 °C, respectively. On the other hand, the sulfate-reducing activity levels of the UASB sludge were relatively high at 10 °C, for example, 18% for acetate and 9% for H 2/CO 2 gas, compared to the activity levels at 35 °C. Therefore, BOD oxidization by sulfate reduction in the UASB was greater than that by methane production under low temperature conditions. This sulfate-reducing activity tended to be proportional to the copy number of adenosine-5′-phosphosulfate (APS) reductase genes in DNA extracted from the sludge.

Occurrence of Escherichia coli O157:H7 and Other Enterohemorrhagic Escherichia coli in the Environment

Enterohemorrhagic Escherichia coli (EHEC) (O157 and other serotypes) are zoonotic pathogens linked with severe human illnesses. The main virulence factors of EHEC are the Shiga toxins, among others. Most of the genes coding for these toxins are bacteriophage-encoded. Although ruminants are recognized as their main natural reservoir, water has also been documented as a way of transmission of EHEC. E. coli O157:H7 and other EHEC may contaminate waters (recreational, drinking or irrigation waters) through feces from humans and other animals. Indeed, the occurrence of EHEC carrying the stx2 gene in raw municipal sewage and animal wastewater from several origins has been widely documented. However, the evaluation of the persistence of naturally occurring EHEC in the environment is still difficult due to methodological problems. Methods proposed for the detection and isolation of stx-encoding bacteria, ranging from the classic culture-based methods to molecular approaches, and their application in the environment, are discussed here. Most virulence factors associated with these strains are linked to either plasmids or phages, and consequently they are likely to be subject to horizontal gene transfer between species or serotypes. Moreover, the presence of infectious stx-phages isolated as free particles in the environment and their high persistence in water systems suggest that they may contribute to the spread of stx genes, as they are directly involved in the emergence of new pathogenic strains, which might have important health consequences.

Detection of bacterial pathogens in municipal wastewater using an oligonucleotide microarray and real-time quantitative PCR

As a first step toward building a comprehensive microarray, two low density DNA microarrays were constructed and evaluated for the accurate detection of wastewater pathogens. The first one involved the direct hybridization of wastewater microbial genomic DNA to the functional gene probes while the second involved PCR amplification of 23S ribosomal DNA. The genomic DNA microarray employed 10 functional genes as detection targets. Sensitivity of the microarray was determined to be approximately 1.0 μg of Esherichia coli genomic DNA, or 2 × 10 8 copies of the target gene, and only E. coli DNA was detected with the microarray assay using municipal raw sewage. Sensitivity of the microarray was enhanced approximately by 6 orders of magnitude when the target 23S rRNA gene sequences were PCR amplified with a novel universal primer set and allowed hybridization to 24 species-specific oligonucleotide probes. The minimum detection limit was estimated to be about 100 fg of E. coli genomic DNA or 1.4 × 10 2 copies of the 23S rRNA gene. The PCR amplified DNA microarray successfully detected multiple bacterial pathogens in wastewater. As a parallel study to verify efficiency of the DNA microarray, a real-time quantitative PCR assay was also developed based on the fluorescent TaqMan® probes (Applied Biosystems).

Simultaneous determination of natural and synthetic steroid estrogens and their conjugates in aqueous matrices by liquid chromatography/mass spectrometry

An analytical method for the simultaneous determination of nine free and conjugated steroid estrogens was developed with application to environmental aqueous matrices. Solid-phase extraction (SPE) was employed for isolation and concentration, with detection by liquid chromatography/mass spectrometry (LC/MS) using electrospray ionisation (ESI) in the negative mode. Method recoveries for various aqueous matrices (wastewater, lake and drinking water) were determined, recoveries proving to be sample dependent. When spiked at 50 ng/L concentrations in sewage influent, recoveries ranged from 62–89% with relative standard deviations (RSD) <8.1%. In comparison, drinking water spiked at the same concentrations had recoveries between 82–100% with an RSD <5%. Ion suppression is a known phenomenon when using ESI; hence its impact on method recovery was elucidated for raw sewage. Both ion suppression from matrix interferences and the extraction procedure has a bearing on the overall method recovery. Analysis of municipal raw sewage identified several of the analytes of interest at ng/L concentrations, estriol (E3) being the most abundant. Only one conjugate, estrone 3-sulfate (E1-3S), was observed.

Prevalence of the stx2 gene in coliform populations from aquatic environments.

Shiga toxin-producing Escherichia coli strains are human pathogens linked to hemorrhagic colitis and hemolytic uremic syndrome. The major virulence factors of these strains are Shiga toxins Stx1 and Stx2. The majority of the genes coding for these toxins are borne by bacteriophages. Free Stx2-encoding bacteriophages have been found in aquatic environments, but there is limited information about the lysogenic strains and bacteria present in the environment that are susceptible to phage infection. The aim of this work was to study the prevalence and the distribution of the stx(2) gene in coliform bacteria in sewage samples of different origins. The presence of the stx(2) gene was monitored every 2 weeks over a 1-year period in a municipal sewage treatment plant. A mean value of 10(2) genes/ml was observed without significant variation during the study period. This concentration was of the same order of magnitude in raw municipal sewage of various origins and in animal wastewater from several slaughterhouses. A total of 138 strains carrying the stx(2) gene were isolated by colony hybridization. This procedure detected approximately 1 gene-carrying colony per 1,000 fecal coliform colonies in municipal sewage and around 1 gene-carrying colony per 100 fecal coliform colonies in animal wastewaters. Most of the isolates belonged to E. coli serotypes other than E. coli O157, suggesting a low prevalence of strains of this serotype carrying the stx(2) gene in the wastewater studied.