The effect of a sewage treatment plant effluent on the faecal coliforms and enterococci populations of the reception river waters

AIMS: A rural sewage treatment plant and the effect of its effluent on the enterococci and faecal coliforms populations of the receiving river waters was evaluated. METHODS AND RESULTS: The enumeration of bacteria was performed by membrane filtration. Diversity and population similarity were analysed using the PhP-plates system. The treatment plant reduces the number of enterococci and faecal coliforms to values similar to those observed upstream. All water samples showed a high diversity for both bacterial populations. A high similarity in the composition and structure, was detected among all the samples. CONCLUSIONS: The impact of the disposal of treated sewage on the river did not modify the composition of either bacterial populations in the river water. SIGNIFICANCE AND IMAPCT OF THE STUDY: The biochemical phenotyping of bacterial populations is a reliable tool for ecological and biodiversity studies. The obtained results provide a better understanding of the sewage treatment process and the impact of the treated sewage effluents in the environment.     

Non-compliance of beaches with the EU directives of bathing water quality: evidence of non-point sources of pollution in Morecambe Bay

Morecambe's three EU designated bathing beaches frequently fail the EU directives, even after a state of the art sewage treatment plant has become operational. We have been using conventional microbiology to look at the seasonality and distribution of indicator and pathogenic bacteria in Morcambe Bay and using molecular methods (polymerase chain reaction (PCR) and pulse field gel electrophoresis (PFGE)) to investigate the pathways by which pathogens reach the bathing waters. We will present data for Morecambe Bay which show that: 1. Failures and passes appear to be associated with the prevailing climatic conditions. 2. Indicator bacteria may not always be derived from sewage effluents. 3. Not all pathogens are distributed in the same way as indicator bacteria. 4. Pathogens such as Campylobacter are as likely to come from birds as from sewage.     

Distribution of the human faecal bacterium Bacteroides fragilis, its bacteriophages and their relationship to current sewage pollution indicators in bathing water

Although several bacteria are currently used as possible indicators of human pathogens in sewage-polluted sea water, they are often viewed as inadequate and especially inadequate as indicators of viral pathogens. This study investigates the distribution of Bacteroides fragilis and closely related Bacteroides spp. and their associated bacteriophages in sea water frequently used for recreational purposes. These organisms may provide a potentially more appropriate indicator. Bacteroides fragilis is one of about 10 species which are loosely placed together in the 'B. fragilis' group. Samples down-current from a sewage outfall were examined for the presence of B. fragilis group organisms and associated bacteriophages. Numbers were correlated with current bacterial and possible viral indicators at these sites. These B. fragilis group isolates were used as hosts to successfully isolate bacteriophages. The host range of these bacteriophages was investigated. It is hoped to expand this study by using these B. fragilis group hosts and their bacteriophages to identify a more suitable, European-wide, indicator of bacterial pathogens which can also be used to detect bacteriophages which are suitable as viral indicators.     

The composition and persistence of faecal coliforms and enterococcal populations in sewage treatment plants

AIMS: The changes in structure and composition of faecal coliforms and enterococcal populations in sewage from different treatment plants, and the elimination of vancomycin- and erythromycin-resistant enterococci (VRE and ERE, respectively) in these treatment plants was analysed to determine any selective reduction. METHODS AND RESULTS: Faecal coliforms, enterococci, VRE, ERE and spores of sulphite-reducing bacteria were enumerated using standard methods. Samples were enriched where necessary in order to isolate antibiotic resistant strains. The structure and composition of these bacterial populations were determined by biochemical fingerprinting and clustering analysis. High diversity and similarity indexes were detected among all the bacterial populations in raw and treated sewage, independently of their origin and the treatment processes employed. Antibiotic resistant strains were detected in all sewage tested and no selective reduction was observed. CONCLUSIONS: The faecal coliforms and enterococci populations did not differ in the sewage samples studied. The vancomycin and erythromycin resistances of the enterococcal populations were similar in the sewage samples. Resistance to both antibiotics persisted after the treatment process independently of raw sewage flow, faecal origin or size of the human population contributing to sewage. However, sewage of mixed origin (human and animal) presented a lower similarity index for the two bacterial populations compared with that of the other human sewage analysed. SIGNIFICANCE AND IMPACT OF THE STUDY: Although a significant reduction in bacterial populations was observed, the persistence of VRE and ERE strains in the same proportions in sewage suggests that there is no selective elimination of bacterial populations during the treatment processes. The ability of antibiotic resistance strains to survive sewage treatment systems should be considered in certain water reuse programmes.     

Phototrophic purple and green bacteria in a sewage treatment plant

In all purification stages of a biological sewage treatment plant, phototrophic bacteria were detected by the method of viable cell counts. The predominant species identified belonged to the genus Rhodopseudomonas of purple nonsulfur bacteria. The number of phototrophic bacteria was highest in wastewater containing sludge. In activated sludge, an average of 10(5) viable cells/ml was found; the number depended upon concentration of sludge rather than on seasonal changes in light conditions in the course of a year. Bacteriochlorophyll a was extracted from activated sludge. Relative to the viable counts of phototrophic bacteria, the content of bacteriochlorophyll a was 5- to 10-fold higher than that of three representative pure cultures. By incubation of activated and digester sludge under different environmental conditions, it was shown that phototrophic bacteria can complete with other bacteria only under anaerobic conditions in the light.     

Distribution and survival of faecal indicator bacteria in the sediments of the Bay of Vidy,Lake Geneva,Switzerland

The purpose of this study was to determine the concentrations and the horizontal distribution of faecal indicator bacteria (FIB) including Escherichia coli and Enterococcus sp. in the bottom sediments of the Bay of Vidy, City of Lausanne, Switzerland. A vertical distribution of FIB in sediments near the municipal wastewater treatment plant (WWTP) outlet was evaluated and their persistence in those sediments was monitored for a period of 90 days. High FIB levels were measured in the sediments sampled near the WWTP outlet pipe and the mouth of the Chamberonne River, at concentrations ranging between 10⁵ and 10⁷ CFU 100 g^?1. FIB levels at 10 cm depth in the sediments near the WWTP outlet pipe ranged between 10⁴ and 10⁵ CFU 100 g^?1, and were still detected in the top 6 cm after 90 days. Results of this study indicate that freshwater sediments of the Bay of Vidy constitute a reservoir of faecal indicator bacteria, which can persist in certain areas of the bay. Possible resuspension of FIB and pathogens may affect water quality and may increase health risks to sensitive populations during recreational activities. FIB survival in sediments for long periods is of considerable significance for the understanding of microbial pollution in water and for the management of risk at specific recreational coastal sites.     

De novo formation of organochlorines in a sewage treatment plant

The de novo formation of organochlorines was observed in a municipalsewage treatment plant. Due to this formation, the amount of organically boundhalogens (AOX) increased 15-fold inside the sewage treatment plant. Per day,more than 6 kg of organically-bound chlorine were produced. Thisformation is not based on a metabolism of present organochlorines, it is a denovo formation out of inorganic chloride and organic substrates. The AOXtriggerconcentration in sewage sludge in Germany is 500 mgkg^–1 and was sometimes exceeded by a factor of 10. Noknown anthropogenic organohalogens were found which could explain the elevatedAOX concentrations. Instead many chlorinated compounds could be identifiedwhichwere not known to be of anthropogenic origin. The compound with the highestconcentration was the 3,4-dichlorophenylacetic acid (3,4-CPAc). In one case,more than 1 g kg^–1 of this compound was detected.A slaughterhouse that emits phenylacetic acid is probably the origin of thatformation. In model experiments phenylacetic acid was chlorinated with HOCl butchlorinated phenylacetic acids other than 3,4-CPAc were found. Therefore it canbe excluded that the chlorination in the sewage treatment plant takes place byan abiotic reaction with hypochlorite that might have been introduced there. Weassume that the occurring microorganisms are responsible for the de novoformation in the sewage treatment plant. The obtained knowledge could also beuseful to understand natural chlorination processes.     

The effect of dissolved oxygen,sediment, and sewage treatment plant discharges upon growth,survival and density of Asiatic clams

The biology of Corbicula fluminea, the Asiatic clam, in the Vermilion River, Louisiana, as affected by sediment, dissolved oxygen (DO) levels, and sewage treatment plant (STP) effluents was investigated. A point source of high DO water to the Vermilion River established a gradient of DO that decreased as the river moved towards the Gulf of Mexico. Lowering DO levels were exacerbated by municipal sewage treatment plant discharges in the 20 km reach studied. Low dissolved oxygen was associated with reduced Corbicula density in the river and 30-day in-stream growth studies (weight and length) demonstrated that low DO inhibited growth. Generally, if DO was < 1.0 mg l^–1 in sediment pore water and/or < 3.0 mg l^–1 at the sediment-water interface, growth was significantly impaired (p < 0.05). Corbicula experienced substantial mortality near the STP discharges (up to 70% in 30 days) and laboratory toxicity tests with Ceriodaphnia dubia, a sensitive cladoceran, also strongly suggested discharges were chronically toxic at 6.25–25.0% effluent. Respiration experiments along with environmental measurements of DO, temperature, and STP discharge chemistry support a hypothesis that clam populations are adversely affected by the suite of environmental conditions present in the Vermilion River. Further, growth studies were consistent with observed population densities in situ.     

Effects of a sewage treatment plant outlet pipe extension on the distribution of contaminants in the sediments of the Bay of Vidy, Lake Geneva, Switzerland

In 2001, the municipality of Lausanne extended the outlet pipe of the sewage treatment plant into the Bay of Vidy (Lake Geneva, Switzerland) as a measure to reduce bacterial water pollution and sediment contamination close to the lake beaches. The aim of the present study was to assess the impact of this measure. Lake bottom sediments were collected and analyzed for grain size, organic matter, organic carbon, nitrogen, phosphorus, heavy metals and hydrophobic organic compounds to evaluate their concentration and spatial distribution. Our results demonstrate that, compared to results obtained before the outlet pipe prolongation, the surface area of highly contaminated sediments was reduced by one third after the pipe extension. However, contaminant concentrations are still high and the accumulation of pollutants may represent a significant source of toxicity for benthic organisms. One concludes that contaminant reduction at the source will be necessary for a further improvement.     

Phototrophic purple and green bacteria in a sewage treatment plant.

In all purification stages of a biological sewage treatment plant, phototrophic bacteria were detected by the method of viable cell counts. The predominant species identified belonged to the genus Rhodopseudomonas of purple nonsulfur bacteria. The number of phototrophic bacteria was highest in wastewater containing sludge. In activated sludge, an average of 10(5) viable cells/ml was found; the number depended upon concentration of sludge rather than on seasonal changes in light conditions in the course of a year. Bacteriochlorophyll a was extracted from activated sludge. Relative to the viable counts of phototrophic bacteria, the content of bacteriochlorophyll a was 5- to 10-fold higher than that of three representative pure cultures. By incubation of activated and digester sludge under different environmental conditions, it was shown that phototrophic bacteria can complete with other bacteria only under anaerobic conditions in the light.     

Seasonal migrations of the common Goby,Pomatoschistusmicrops (Kroyer), in Morecambe Bay and elsewhere

Summary Seasonal changes in abundance, and also reproduction, of the gobiid Pomatoschistus microps in intertidal pools on mussel beds at Morecambe, Lancashire, were studied from 1956 to 1961. During winter the shore was largely vacated by this species which returned for breeding purposes in spring. Spawning took place in upper shore pools from April to August. After a planktonic life of between 6–9 weeks, young fishes were recruited to the demersal population usually from June to September. A correlation between seasonal migrations and sea temperature is postulated. Geographical variation in occurrence and extent of migration in P. microps and the related sublittoral P. minutus is considered in relation to minimum winter sea temperatures over the southern Boreal and Baltic sea areas. Offshore winter migration has been found to take place in areas where such temperatures normally fall below 5° C, but not where minimum sea temperature is above 7° C. The effect of the severe winter of 1962–63 on certain populations of P. microps is described.     

Characterization of indicator bacteria in municipal raw water, drinking water, and new main water samples

Municipal water samples were analyzed by membrane filter (MF) and presence-absence (P-A) tests for pollution indicator bacteria. In four years, 11 514 bacterial cultures were isolated from either raw water, drinking water, or new main water samples submitted to three environmental laboratories. The bacterial species occurring most often in all types of water samples were Escherichia coli (11.6-39.7%), Enterobacter aerogenes (18.1-26.3%), Aeromonas hydrophila (8.8-17.0%), Klebsiella pneumoniae (7.7-10.3%), and Citrobacter freundii (5.9-22.7%). A lactose - lauryl tryptose - tryptone broth was examined as an alternative medium to modified MacConkey broth in the presumptive portion of the P-A test. The intensity of acid and gas production in presumptive positive P-A bottles was compared with the types and frequencies of indicator bacteria shown by confirmatory tests. The results of detecting indicator bacteria following the analysis of 53 130 samples over a 2-year period were arranged by water source (well, lake, river, mixed) and water type (raw or drinking) to determine the influence of these parameters on the recovery of indicator bacteria. A further subdivision of the sample types into raw surface, raw ground, in-plant, plant discharge, reservoir, and distribution samples demonstrated the effect of water treatment practices.     

Detection and enumeration of Listeria monocytogenes in a sewage treatment plant in Iraq

Listeria monocytogenes was isolated from a sewage treatment plant in Baghdad, Iraq, at all stages of treatment. The treatment processes did not yield a sewage sludge cake or a final discharge free of listerias. The agricultural practice of using such sewage products as fertilizers could become a route of spreading the organism in Iraq, particularly by infecting animals that consume vegetation in fields spread with such sewage. Dewatering of sewage reduced the number of L. monocytogenes but long periods of exposure to sun would be needed to obtain a 'safe' sewage sludge cake.     

Detection and enumeration of Listeria monocytogenes in a sewage treatment plant in Iraq

Listeria monocytogenes was isolated from a sewage treatment plant in Baghdad, Iraq, at all stages of treatment. The treatment processes did not yield a sewage sludge cake or a final discharge free of listerias. The agricultural practice of using such sewage products as fertilizers could become a route of spreading the organism in Iraq, particularly by infecting animals that consume vegetation in fields spread with such sewage. Dewatering of sewage reduced the number of L. monocytogenes but long periods of exposure to sun would be needed to obtain a 'safe' sewage sludge cake.     

人工湿地污水处理系统中的植物效应与基质酶活性

为了解植物在湿地污水净化系统中的作用与机理,构建了A-B-C三级串连垂直流人工湿地系统,并选择水葱(Scirpus validus)风车草(Cyperus alternifolius)、美人蕉(Canna indica)、和芦苇(Phragmites australis)作为测试植物,进行了生活污水处理试验.结果表明,系统中有植物单元单位面积污染物的去除量均高于无植物对照单元.与对照相比,在A、B、C三级系统中由植物效应产生的CODCr去除增量分别为43.52 g/(m2·d),20.38 g/(m2·d),30.94 g/(m2·d);TN去除增量为13.14 g/(m2·d),28.61 g/(m2·d),6.97 g/(m2·d);TP去除增量为1.2 g/(m2·d),0.66 g/(m2·d),0.06 g/(m2·d).从A到C级,污水中污质浓度递减,呈现根系活力显著增强,而植物生长量、过氧化物酶含量、生长量与氮磷积累量等显著下降趋势.基质酶活性在对照单元中较低,在有植物单元中,基质酶活性明显增大并与根系活力成正相关.     

Detection of low numbers of Salmonella in environmental water, sewage and food samples by a nested polymerase chain reaction assay

A polymerase chain reaction (PCR) assay with two nested pairs of primers selected from conserved sequences within a 2.3 kb randomly cloned DNA fragment from the Salmonella typhimurium chromosome was developed. The nested PCR assay correctly identified 128 of a total of 129 Salmonella strains belonging to subspecies I, II, IIIb and IV. One strain of Salm. arizona (ssp. IIIa) tested negative. No PCR products were obtained from any of the 31 non-Salmonella strains examined. The sensitivity of the assay was 2 cfu, as determined by analysis of proteinase K-treated boiled lysates of Salm. typhimurium. The performance of the assay was evaluated for environmental water, sewage and food samples spiked with Salm. typhimurium. Water and sewage samples were filtered and filters were enriched overnight in a non-selective medium. Prior to PCR, the broth cultures were subjected to a rapid and simple preparation procedure consisting of centrifugation, proteinase K treatment and boiling. This assay enabled detection of 10 cfu 100 ml(-1) water with background levels of up to 8700 heterotrophic organisms ml(-1) and 10000 cfu of coliform organisms 100 ml(-1) water. Spiked food samples were analysed with and without overnight enrichment in a non-selective medium using the same assay as above. Nested PCR performed on enriched broths enabled detection of <10 cfu g(-1) food. Variable results were obtained for food samples examined without prior enrichment and most results were negative. This rapid and simple assay provides a sensitive and specific means of screening drinking water or environmental water samples, as well as food samples, for the presence of Salmonella spp.     

Antibiotic resistance of native and faecal bacteria isolated from rivers, reservoirs and sewage treatment facilities in Victoria, south-eastern Australia

The incidence of resistance to ampicillin, chloramphenicol, kanamycin, nalidixic acid, neomycin and streptomycin was significantly greater (P < 0.001) in native heterotrophic bacteria than in Escherichia coli isolated from a range of sites along the Yarra River in south-eastern Australia. There was no significant difference in the incidence of resistance between native and faecal bacteria to tetracycline. Both groups were almost totally resistant to penicillin. Multivariate analyses indicated little clear spatial pattern in the incidence of resistance in native bacteria from upstream vs downstream sites along the Yarra River. In contrast, E. coli isolated from upstream (rural) sites tended to have a lower incidence of resistance than isolates from downstream (urban) sites. These findings have implications for the use of antibiotic resistance as a bacteriological water quality parameter.