Occurrence of Giardia cysts and Cryptosporidium oocysts in raw and treated water from two water treatment plants in Selangor, Malaysia

The occurrence of Giardia cysts and Cryptosporidium oocysts was determined both in the raw water and the treated waters from two water treatment plants in Selangor, Malaysia between July 1994 and January 1995. At each treatment plant, raw and treated water samples were collected fortnightly on 10 separate occasions. Physical parameters, including dissolved oxygen, pH, temperature, conductivity, turbidity and free and total chlorine were measured, and samples were also taken for faecal coliform analyses. The isolation and enumeration of cysts and oocysts was according to UK standard methods. Whilst Giardia cysts were detected in 90% of the raw water samples (range 0–60 cysts per litre) no Cryptosporidium oocysts were detected. Higher concentrations of cysts were detected in the raw water of the first treatment plant. All raw water samples were faecally contaminated, as faecal coliform counts ranged from 4.6 × 10⁴ to 1.3 × 10⁵ colony forming units per 100 ml. No correlation between the concentration of Giardia cysts and the concentration of faecal coliforms could be demonstrated statistically, nor was there any correlation between the concentration of Giardia cysts and the physical parameters tested for any of the raw waters. No cysts, oocysts or faecal coliforms were detected in samples of treated water.     

Fecal coliform removal in wastewater treatment plants studied by plate counts and enzymatic methods

Twelve wastewater treatment plants (WWTPs) were sampled in France and Belgium in 1999 and 2000 in order to estimate the fecal coliform (FC) removal efficiency of various types of treatment. Only one of these WWTPs was equipped with a specific step to eliminate microorganisms (UV disinfection preceded by sand filtration). FC abundance was measured in raw and treated sewage by plate counts on selective medium and rapid beta-D-glucuronidase (GLUase)-based assays. Removal of culturable FC was the most efficient in treatments with high retention time (activated sludge process with nitrification and denitrification, lagooning), in biofiltration and in the treatment with a tertiary disinfection step. GLUase activity measurements showed the same removal pattern as plate counts except for UV disinfection, where no reduction of GLUase activity was measured. Specific loads of culturable FC and GLUase activity, i.e. daily amounts of culturable FC or GLUase activity in sewage per inhabitant-equivalent, were calculated in raw and treated wastewater for the different WWTPs.     

Effect of pathogen concentrations on removal of Cryptosporidium and Giardia by conventional drinking water treatment

The presence of waterborne enteric pathogens in municipal water supplies contributes risk to public health. To evaluate the removal of these pathogens in drinking water treatment processes, previous researchers have spiked raw waters with up to 10(6) pathogens/L in order to reliably detect the pathogens in treated water. These spike doses are 6-8 orders of magnitude higher than pathogen concentrations routinely observed in practice. In the present study, experiments were conducted with different sampling methods (i.e., grab versus continuous sampling) and initial pathogen concentrations ranging from 10(1) to 10(6) pathogens/L. Results showed that Cryptosporidium oocyst and Giardia cyst removal across conventional treatment were dependent on initial pathogen concentrations, with lower pathogen removals observed when lower initial pathogen spike doses were used. In addition, higher raw water turbidity appeared to result in higher log removal for both Cryptosporidium oocysts and Giardia cysts.     

Prevalence of Cryptosporidium oocysts and giardia cysts in the drinking water supply in Japan

A one-year monitoring of Cryptosporidium oocysts and Giardia cysts was conducted at a water purification plant. A total of 13 samples of 50 L river source water and 26 samples of 2,000 L-filtered water, treated by coagulation flocculation, sedimentation and rapid filtration, were tested. Prior to conducting a survey of a water purification plant, we developed a method for concentrating Cryptosporidium oocysts from a large volume of raw or filtered water using a hollow fiber ultrafiltration (UF) membrane, and this procedure was adapted to survey a water purification plant. Cryptosporidium oocysts were detected in all of the 13 raw water samples. The geometric mean concentration was 40 oocysts 100 L. Giardia cysts were detected in 12 of 13 raw water samples (92%) and the geometric mean concentration was 17 cysts/100 L. Probability distributions of both Cryptosporidium oocyst and Giardia cyst concentration in raw water were nearly lognormal. In filtered water samples, Cryptosporidium oocysts were detected in 9 of the 26 samples (35%) with the geometric mean concentration of 1.2 oocysts /1,000 L and Giardia cysts in 3 samples (12%) with 0.8 cysts/1,000 L. The estimated log10 removal efficiency of Cryptosporidium oocysts and Giardia cysts by rapid-sand filtration was 2.47 and 2.53, respectively. Empty particles were removed at a higher log10 than intact oocysts and cysts. The efficiency of particle removal in the rapid sand filtration process tends to be reduced under cold-water conditions. Close management is necessary in the winter when the water temperature is low.     

Relationship between coliform culturability and organic matter in low nutritive waters

The objective of this work was to investigate the behaviour of coliform bacteria in specific low nutritive waters conveying organic fractions from different origin of which an unknown part is likely to pass through the treatment barrier. For this purpose, we studied the growth (microscopic counting) and the culturability (count on nutritive medium) of ten coliform bacteria species as a function of the amount of organic matter in a river water collected after a period of heavy rain and in an algal bloom water. Assays were carried out in the presence of autochthonous heterotrophic bacteria from the Nancy (France) drinking water, with variable concentrations of dissolved organic carbon (DOC) representative of drinking waters (0.5-1.5 mg l(-1) for diluted river water samples and 1.3-2.5 mg l(-1) for diluted algal bloom water samples). Bacterial growth was measured in the two types of water, regardless of the initial concentration of DOC. We found that coliform bacteria lost their culturability in both sample series, and that the lower the initial DOC concentration the more rapidly the culturability was lost. The quantity of DOC consumed by the bacteria in the two water types (0.03-0.13 mg l(-1) in river water and 0.77-1.29 mg l(-1) in algal bloom water) and the resulting consequences on bacterial behaviour suggested that bloom water contains algal organic compounds that are antagonistic to the growth and/or the culturability of coliform bacteria. Organic matter thresholds, beyond which coliform bacteria are unlikely to keep their culturability, have not been determined experimentally. Indeed, at the end of the assays some culturable coliform bacteria were systematically detected in both types of water. Enterobacter cloacae was the predominant species. Thus, during these adverse events the probability of coliform occurrence can be considered as high in treated water.     

The effects of tertiary wastewater treatment on the prevalence of antimicrobial resistant bacteria

The effects of tertiary wastewater treatment on the prevalence of antimicrobial resistant bacteria were investigated in two large-scale municipal treatment plants during a period of six months. Total and relative numbers of resistant bacteria were determined in raw sewage, treated sewage and anaerobically digested sludge by bacteriological counts on media selective for coliforms (MacConkey agar) and Acinetobacter spp. (Baumann agar). In addition, the level of antimicrobial susceptibility was determined by the disc-diffusion method in 442 Acinetobacter isolates identified by colony hybridisation with a genus-specific DNA probe. Independent of the different antibiotics and media used, the total numbers of resistant bacteria in treated sewage were 10-1000 times lower than in raw sewage. Based on linear regression analysis of data on bacteriological counts, the prevalences of antimicrobial-resistant presumptive coliforms and Acinetobacter spp. in treated sewage and digested sludge were not significantly higher compared with raw sewage. On the contrary at one plant, statistically significant decreases were observed in the prevalence of ampicillin-resistant presumptive Acinetobacter spp. (p = 0.0188) following sewage treatment, and in the prevalence of either ampicillin-resistant presumptive Acinetobacter spp. (p = 0.0013) or ampicillin- and gentamicin-resistant presumptive coliforms (p = 0.0273 and p = 0.0186) following sludge treatment. The results obtained by bacteriological counts were confirmed by antimicrobial susceptibility testing of Acinetobacter isolates. Based on logistic regression analysis, isolates from treated sewage and digested sludge were generally not significantly more resistant compared with isolates from raw sewage. Based on these evidences, it was concluded that tertiary wastewater treatment did not result in a selection of antimicrobial resistant bacteria.     

净水供水一体化设备处理高藻低浊水库水研究

采用净水供水一体化设备对珠海市唐家水厂水库原水进行净化处理。结果表明,一体化净水供水设备对浊度、藻类、有机物和细菌均有较好的处理效果,运行期间浊度和CODMn的平均去除率分别为97％和46％,藻类去除率大于99％,细菌的截留率达到100％,出水水质满足《生活饮用水卫生标准》（GB5749--2006）限值要求。     

Inactivation of Bacillus subtilis spores with ozone and monochloramine

The inactivation kinetics of Bacillus subtilis spores with ozone and monochloramine was characterized by a lag phase followed by a pseudo-first-order rate of inactivation. The lag phase decreased and the post-lag phase rate constant increased with increasing temperature within the range investigated (1-30 degrees C for ozone, 1-20 degrees C for monochloramine). The corresponding activation energies were 46820 J/mol for ozone and 79640 J/mol for monochloramine. The CT concept was found to be valid within the concentration range investigated of 0.44-4.8 mg/l for ozone, and 3.8-7.7 mg/l as Cl(2) for monochloramine. The inactivation kinetics of B. subtilis spores with both ozone and monochloramine varied with pH within the range of pH 6-10 investigated. The fastest ozone and monochloramine inactivation rates were observed at pH 10 and 6, respectively. Different stocks of the same strain of B. subtilis spores had different resistance to ozone and monochloramine mainly because of discrepancies in the extent of the lag phase. B. subtilis spores might not be conservative surrogates for C. parvum oocysts for ozone disinfection at relatively low temperature mainly due to the spores having a lower activation energy compared to that for the oocysts. In contrast, the activation energy for monochloramine was comparable for both microorganisms but differences in the extent of the lag phase might result in the spores being overly conservative surrogates for the oocysts at relatively low temperature.     

Removal efficiency and homologue patterns of dioxins in drinking water treatment

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) analyses in raw and treated water throughout Japan were implemented to identify the concentration and homologue patterns of dioxins before and after the water treatment process. In 40 surface water and 5 ground water treatment plants, the removal efficiency of dioxins and the influence of extent chlorination on dioxins increase in drinking water were also studied. Raw water and treated water were sampled twice, summer and winter. The mean concentration in raw water and treated water of dioxins was 56.45 pg/L (0.15 pg WHO-TEQ/L) and 4.24 pg/L (0.019 pg WHO-TEQ/L), respectively. Location of water treatment plants not only significantly influenced the concentration level of dioxins but also resulted in different homologue patterns of dioxins. Levels of dioxins in ground water were much less than that of surface water in both raw and treated water. This study shows most dioxin congeners are well removed (87% removal efficiency) by water treatment. However, in some water treatment plants, the level of TeCDFs (pg WHO-TEQ/L) increased as a result of chlorination.     

污水再生工艺去除病原体效果的评价

为考察常用城市污水再生回用工艺去除病毒的效果,采用柯萨奇B3型病毒(CoxB3)作为肠道病毒示踪剂进行试验.首先向污水厂二级处理出水中人工投加已知浓度的病毒,然后分别采用混凝/沉淀/过滤、超滤、氯消毒和臭氧消毒对其进行处理,并分析处理前后病毒的组织培养半数感染剂量(TCID50).结果表明,混凝/沉淀/过滤对大肠菌的去除率为2-lg～3-lg,对柯萨奇病毒的去除率约为1.83-lg;氯消毒和臭氧消毒可以有效杀灭大肠菌,在消毒剂浓度为1～10mg/L、余氯浓度为1～6 mg/L、pH为6～7的条件下,氯消毒对柯萨奇病毒的去除效果不佳,臭氧消毒对柯萨奇病毒的去除率则随臭氧浓度的不同而在1.33-lg～3.83-lg变化;超滤可有效去除大肠菌,对柯萨奇病毒的去除率为2.33-lg.     

The ecology of "fecal indicator" bacteria commonly found in pulp and paper mill water systems

Coliform bacteria have long been used to indicate fecal contamination of water and thus a health hazard. In this study, the in-mill water and external effluent treatment systems of seven typical Canadian pulp and paper mills were all shown to support the growth of numerous coliforms, especially Klebsiella Spp., Escherichia coli. Enterobacter spp., and Citrobacter spp. In all mills and most sampled locations, klebsiellas were the predominant coliforms. Although all but one of the mills had no sewage input and most disinfected their feed (input) water, all contained the most typical fecal indicator bacterium, E. coli. Many of the mill coliforms were classified as fecal coliforms by standard "MPN" and metabolic tests, but this was shown to be due to their thermotolerance, not their origin. Mill coliforms were shown not to be just simple transients from feedwater or furnish (wood), but to be continuously growing, especially in some of the primary clarifiers. Isolated mill coliforms grew very well on a sterilized raw combined mill effluent. The fecal streptococci (enterococci), alternative indicators of fecal health hazards, were common in all mills in the absence of sewage. Ten strains of E. coli isolated from four mills were all shown to be non-toxigenic strains of harmless serotypes. No salmonellas were found. Therefore, the use of total coliform, fecal coliform, enterococci, or E. coli counts as indicators of fecal contamination, and thus of health hazard in pulp and paper mill effluents or biosolids (sludges) known to be free of fecal input is invalid.     

Artificial groundwater treatment: biofilm activity and organic carbon removal performance

The artificial recharge of sand aquifers with raw source waters is a means both explored and utilised by many water utilities to meet the future potable water demands for increasing urban populations. The microbial ecology within these systems is however, poorly understood, as is the role that microbial biofilms play in the quality of finished water. Knowledge of the ability of biofilm bacteria to metabolise natural organic matter (NOM) is limited, particularly in respect to the degradation of normally recalcitrant hydrophilic and hydrophobic humic acid fractions by sessile and planktonic microbial consortia within sand aquifer systems. To simulate the artificial recharge of sand aquifers that were proposed for the Greater Stockholm Area, four separate 4 m deep sand columns were fed raw lake water and examined over a 45-week study period. The simulated aquifer system (hydraulic retention time 9-16 h) demonstrated the removal of total organic carbon (TOC) (10+/-5%), direct total counts (DTC) of bacteria (74+/-11%), heterotrophic plate count (HPC) bacteria (87+/-5%) and assimilable organic carbon (AOC) (87+/-5%), thereby fulfilling an important barrier function, except for the removal of TOC. Hydrophilic humic acid fractions were more readily metabolised by microbiota (HPC and EUB338-positive cells) harvested from the raw source water (SSM-W), whilst hydrophobic humic acid fractions promoted higher activity by microbiota harvested from the sand matrix (SSM-S). The apparent low activity demonstrated by biofilm microbiota (approximately 40% and 25% of DTC were positive to EUB338 probing for sand matrix and slide biofilms, respectively) could be attributed to the highly recalcitrant nature of the organic loads, whilst at the same time explain the poor removal of TOC. Following nutrient activation (by the PAC assay) nonetheless, a 3-fold increase in the percentage of EUB-positive bacteria was observed on glass slides. Furthermore, the incubation of SSM-S with R2A increased probe-active cells from 57+/-8% to 75+/-7% of DTC and at the same time increased SSM-W from 38+/-8% to 50+/-10%. Whilst these results may imply a good potential for the biological treatment of water by shallow sand aquifers, further work should address the poor removal of TOC observed in this study.     

Relating freshwater organic matter fluorescence to organic carbon removal efficiency in drinking water treatment

Monthly raw and clarified water samples were obtained for 16 UK surface water treatment works. The fluorescence excitation-emission matrix (EEM) technique was used for the assessment of total organic carbon (TOC) removal and organic matter (OM) characterisation. The impact of algae presence in water on TOC removal, and its relationship with fluorescence, was analysed. Fluorescence peak C intensity was found to be a sensitive and reliable measure of OM content. Fluorescence peak C emission wavelength and peak T intensity (reflecting the degree of hydrophobicity and the microbial fraction, respectively) were found to characterize the OM; the impact of both on TOC removal efficiency was apparent. OM fluorescence properties were shown to predict TOC removal, and identify spatial and temporal variations. Previous work indicates that the trihalomethane (THM) concentration of treated water can be predicted from the raw water TOC concentration. The simplicity, sensitivity, speed of analysis and low cost, combined with potential for incorporation into on-line monitoring systems, mean that fluorescence spectroscopy offers a robust analytical technique to be used in conjunction with, or in place of, other approaches to OM characterisation and THM formation prediction.     

Occurrence of pathogens on vegetables harvested from soils irrigated with contaminated streams

The study assesses the contamination level, the seasonal distribution and the toxigenicity of pathogens isolated from irrigated vegetables and the water used for irrigation. A total of 196 samples of water used for irrigation and 326 irrigated vegetables were obtained from Kawo drain, Sabon Gari drain and River Galma and examined using standard procedures for coliform and viable counts and the presence of E. coli, Salmonella and Vibrio during the dry and wet seasons. Irrigation water from Kawo drain had significantly higher coliform counts by location and season than water from the other two locations. Although all the vegetables had coliform counts higher than the recommended standard (range 3.40-6.38 log(10) cfuml(-1)), amaranthus had significantly higher (P<0.05) counts than other vegetables during the dry season. Salmonella was significantly more likely to be detected during the dry season than during the wet (OR 4.91, 1.07相似文献   

The assessment of particle association and UV disinfection of wastewater using indigenous spore-forming bacteria

Studies have shown that association between particles and coliform bacteria in wastewater influence the inactivation of these microorganisms by ultraviolet (UV) irradiation. This research investigated the potential use of indigenous aerobic spore-forming (ASF) bacteria for studying the particle - microorganism interaction and its effect on UV disinfection of protozoan pathogens, such as Giardia spp. and Cryptosporidium spp., present in effluents from full-scale municipal wastewater treatment plants. The effect of particle - ASF association was determined by homogenizing wastewater effluent samples before and after exposure to controlled UV doses delivered by a bench-scale collimated beam apparatus. Particle association between Bacillus subtilis spores added to wastewater and wastewater particles was also assessed. The results indicate that spores are not significantly associated with wastewater particulate matter and particle association does not significantly affect the inactivation of indigenous spores present in wastewater by UV radiation in this study.     

Bacterial population changes in hospital effluent treatment plant in central India

Hospital effluent with its high content of multidrug resistant (MDR) enterobacteria and the presence of enteric pathogens could pose a grave problem for the community. It was planned at our tertiary care hospital in central India to study the population changes at various steps of effluent treatment plant (ETP) like collection, aeration, clarification, liquid sludge, dried sludge, high-pressure filter and treated wastewater. The study included viable bacterial counts, coliform counts, staphylococcal, enterococcal, Pseudomonas and multiple drug resistant (MDR) gram negative bacterial counts in the different stages of ETP. In order to study the distribution of bacteria as free floating in liquid and adherent to suspended particles, enumeration of the bacteria in the filterate and the sediment was also carried out. The effluent input showed 55% of the 8.6 x 10(6)/ml bacteria as coliforms and E. coli which was a typical of fecal flora. The prevalence of MDR coliforms was 0.26%. The substantial reduction (> 3log) was seen for the effluent coming from the clarifier. The bulk of the bacteria in the hospital effluent remains firmly adhered to solid particles; aeration and clarification removes bulk of the bacteria by physical processes like flocculation. The treated liquid effluent still contains sizeable loads of MDR bacteria and inactivation by procedure such as chlorination is required. The bacteria get concentrated in sludge and a greater concentration of chlorine is required for decontamination.     

三种预氧化剂在水处理中的应用评估

源水的富营养化将严重影响常规给水处理厂的运行,使得出水水质不能保证。为此,开展了KMnO4、H2O2、ClO2 的预氧化研究。结果表明,投加这三种氧化剂均能显著提高对水中藻类、浊度、有机物的去除率,对细菌及大肠菌群也有较好的去除效果,但投加KMnO4 会增加出水色度,采用ClO2 作氧化剂则成本较高,相比之下H2O2 是一种较为理想的预氧化剂。     

Bacteriophages and Clostridium spores as indicator organisms for removal of pathogens by passage through saturated dune sand

In a field study on the efficiency of dune recharge for drinking water production, bacteriophage MS2 was shown to be removed 8 log(10) by passage through the dune sand. The question of whether pathogenic viruses would be removed as much as MS2 was studied by comparing complete breakthrough curves of MS2 with those of the human viruses Coxsackievirus B4 (CB4) and Poliovirus 1 (PV1) in laboratory columns. The columns were designed to closely simulate the field conditions: same sand, water, porewater velocity and temperature. Employing a two-site kinetic model to simulate breakthrough curves, attachment/detachment to two types of kinetic sites as well as inactivation of free and attached viruses were evaluated. It was found that attachment to only one of the sites is of significance for determining overall removal. At field scale, removal of the less negatively charged PV1 was extrapolated to be about 30 times greater than that of MS2, but removal of CB4 would be only as much as that of MS2. Also, removal of spores of Clostridium perfringens D10, a potential surrogate for Cryptosporidium oocysts, was studied. The attachment rate coefficient of the spores was 7.5 times greater than that of MS2. However, this does not imply that the removal of the spores is 7.5 times greater than that of MS2. Due to negligible inactivation in combination with detachment of previously attached spores, the actual removal rate of the spores depends on the duration of contamination and eventually all spores will break through. Provided no irreversible attachment or physical straining occurs, this may also be the case for other persistent microorganisms, like oocysts of Cryptosporidium.     

某市贾第鞭毛虫和隐孢子虫污染现状

利用免疫荧光分析技术对南方某市饮用水源水、自来水厂出水和污水处理厂进、出水中贾第鞭毛虫和隐孢子虫(两虫)的污染状况进行了调查,并就自来水厂常规处理工艺对两虫的去除特性进行了研究.结果显示:该市饮用水源水中的两虫密度分别为2～120个/100L和0～24个/100 L,自来水厂出水分别为0～12个/1000 L和0～8个/1000 L,污水处理厂进水中的两虫密度分别为7 200～18 300个/L和69～1 210个/L,二级处理出水的分别为6～153个/L和1～46个/L;混凝沉淀和过滤对两虫有较好的去除效果.     

上海市浦东自来水厂净水工艺对两虫去除效果的研究

采用免疫磁分离及荧光染色法（EPA1623法）对上海市浦东地区4家自来水厂的原水、出厂水、管网水中贾第鞭毛虫和隐孢子虫的分布状况进行了分析，并考察了水厂净水过程中不同操作单元对两虫的去除效果。研究表明：原水中存在贾第鞭毛虫与隐孢子虫，但其密度分别维持在0～8个／10L和0～6个／10L的低水平，而在出厂水与管网水中均未检出两虫；水厂的混凝、沉淀单元对两虫具有明显的去除效果。