影响饮用自来水亚硝酸盐指标的几个主要因素

本文着眼于目前城市饮用自来水中亚硝酸盐偏高的问题,通过大量实地调查、水质检测及历年数据统计分析工作,研究了水源污染、生物化学转化、氯胺消毒工艺及输水管网等因素对饮用自来水中亚硝酸盐指标的影响,并提出了一些可行的改进方案。     

Rapid and automated detection of fluorescent total bacteria in water samples

Traditional methods for the detection and enumeration of bacteria in water samples are growth-based and require several days to obtain the result. New techniques which reduce the time of analysis have been developed. The objective of this work was to test a rapid method for the detection and enumeration of total viable bacteria using direct fluorescent labelling and detection by laser scanning. This method (referred to as TVC for Total Viable Count) was compared to the R2A culture method and the cyano-ditolyl-tetrazolium chloride (CTC) staining method for the analysis of samples before the final chlorination (after GAC filtration) and drinking water samples. For the comparison of TVC and CTC, the outcome depends on the water type: for samples after GAC filtration, TVC counts were significantly lower than CTC counts by up to 2 log10 orders of magnitude. For chlorinated water samples, TVC counts were not significantly different from CTC counts. The comparison of TVC and R2A showed that TVC counts could be lower than R2A counts or equivalent depending on the type of water. For drinking water, the TVC method proved to yield results equivalent to those of the R2A method. The TVC method requires much shorter time frame than others. It is also simple to use and allows the analysis of large volumes (100 ml) of drinking water.     

我国包装饮用水行业发展现状及存在的问题

本文介绍了我国包装饮用水的行业现状,并围绕水源、生产和流通环节深入排查了包装饮用水的行业风险。水源风险主要集中在公共供水系统的消毒副产物污染、非公共供水系统的水质污染和企业对水源管理不严格等;生产环节的风险主要集中在行业准入门槛低、部分企业管理松散、水处理及杀菌工艺控制不严、包装容器的使用风险、清洗消毒不符合规范、执行标准界限模糊、产品市场宣传概念存在争议等;流通环节的风险主要集中在水站经营水平不高、制假售假、产品运输不规范等。针对以上风险,本文提出了适应国内包装饮用水产业发展的监管对策,对企业提升产品质量和完善包装饮用水监管制度体系具有重要意义。     

Long-term trends and opportunities for managing regional water supply and wastewater greenhouse gas emissions

Greenhouse gas emissions are likely to rise faster than growth in population and more than double for water supply and wastewater services over the next 50 years in South East Queensland (SEQ), Australia. New sources of water supply such as rainwater tanks, recycled water, and desalination currently have greater energy intensity than traditional sources. In addition, direct greenhouse gas emissions from reservoirs and wastewater treatment and handling have potentially the same magnitude as emissions from the use of energy. Centralized and decentralized water supply and wastewater systems are considered for a scenario based upon a government water supply strategy for the next 50 years. Many sources of data have large uncertainties which are estimated following the IPCC Good Practice Guidelines. Important sources of emissions with large uncertainties such as rainwater tanks and direct emissions were identified for further research and potential mitigation of greenhouse gas emissions.     

Renewable energy powered membrane technology. 1. Development and characterization of a photovoltaic hybrid membrane system

In isolated communities where potable water sources as well as energy grids are limited or nonexistent, treating brackish groundwater aquifers with small-scale desalination systems can be a viable alternative to existing water infrastructures. Given the unavailability of power in many such situations, renewable energy is an obvious solution to power such systems. However, renewable energy is an intermittent power supply and with regards to the performance of intermittently operated desalination systems, only very limited experience exists, both with regards to efficiency as well as water quality. In this paper, this lack of knowledge is addressed by evaluating a system operated with varying parameters (pressure and flow) with constant power as a step toward defining a safe operating window, and they provide a basis for interpreting future data obtained with a renewable energy source. Field trials were performed on a brackish (5300 mg/L TDS; 8290 microS/cm) bore in Central Australia with a photovoltaic-powered membrane filtration (PV-membrane) system. Four nanofiltration and reverse osmosis membranes (BW30, ESPA4, NF90, TFC-S) and a number of operation parameter combinations (transmembrane pressure, feed flow, TFC-S) and operating parameters transmembrane pressure and feed flow were investigated to find the best operating conditions for maximum drinking water production and minimum specific energy consumption (SEC). The ESPA4 membrane performed best for this brackish source, producing 250 L/h of excellent drinking water (257 mg/L TDS; 400 microS/ cm) at an SEC of 1.2 kWh/m3. The issue of brine disposal or reuse is also discussed and the article compares the salinity of the produced brine with livestock water. Since the feedwater is disinfected physically using ultrafiltration (UF), the brine is free from bacteria and most viruses and hence can be seen more as a reusable product stream than a waste stream with a disposal problem.     

水环境中贾第鞭毛虫和隐孢子虫检测方法的研究进展

水环境中的病原微生物是一个重要的公共卫生问题。贾第鞭毛虫和隐孢子虫是世界上最主要的2种能导致人体腹泻的寄生虫,具有潜伏期长、个体小、致病性强且容易暴发流行的特点,对公共卫生安全造成严重威胁。预防其暴发的关键就是通过优化水处理的工艺来确保饮用水的安全,但由于供水系统极易遭受各种形式的二次污染,依然存在着不能完全去除的风险。自新的生活饮用水卫生标准实施以来,我国对水源水和饮用水的相关调查和监测逐渐增多,贾第鞭毛虫和隐孢子虫时常被检出。本文就近年来对水环境中贾第鞭毛虫和隐孢子虫的检测技术进展情况进行综述,并针对现行的国标检测方法提出影响因素分析及质量控制方法。随着免疫学和现代分子生物学的不断发展,新的检测技术不断涌现,并具有良好的应用前景。     

Perfluorinated compounds in the environment and the blood of residents living near fluorochemical plants in Fuxin, China

A fluorochemical industrial park was built in 2004 in Fuxin, China, for the production of polytetrafluoroethylene (PTFE) and perfluorobutane sulfonate (PFBS). Yet little is known about the distribution of fluorochemicals in the environment and in people living in and around the park. In this study, environmental samples were collected from 22 sites in Fuxin to investigate the extent of perfluorinated compound (PFC) contamination in the environment around the park, and in drinking water from the public water supply system and groundwater in shallow aquifers from private wells near the park. Serum samples were also collected from nonoccupationally exposed residents living in Fuxin to determine the PFC load of local residents. As the dominant contaminant of eight target PFCs, the maximum concentrations of perfluorooctanoic acid (PFOA) in sediment and river water of the River Xi along the industrial park were 48 ng/g dry weight and 668 ng/L, respectively; the highest PFOA concentration in groundwater beneath the park was 524 ng/L; and the PFOA levels in drinking water from the public water supply system ranged between 1.3 and 2.7 ng/L. In human serum, PFOA had the geometric mean at 4.3 ng/mL, ranging from 0.02 to 93 ng/mL. This study serves to document what should be the beginning of a long-term surveillance effort to minimize potential exposure of residents living in Fuxin.     

Sources of parameter uncertainty in predicting treatment performance: the case of preozonation in drinking water engineering

This study investigates the factors that determine parameter uncertainty when applying predefined, existing models to predict the performance of a full scale treatment system from environmental engineering. The analysis is performed for ozonation of surface water, a technology applied in drinking water treatment for disinfection and oxidation of micropollutants. The pseudo first order rate constant of ozone decay k(O3) is characterized as a time dependent parameter and estimated from data obtained from three experimental setups representing upscaling stages in engineering design. To obtain meaningful uncertainty estimates, various factors need to be acknowledged: uncertainty about the model structure, uncertainty of other model parameters, uncertainty due to non-representative sampling, and errors in chemical analysis. It is concluded that an on-site automated sequencing batch reactor is best suited for estimating kinetics during operation of the full scale system. Furthermore, the transferability of information in upscaling from laboratory experiments to the full scale system is found to be critical. Although uncertainty analysis enhances the understanding of the system, it is also shown to be a subjective process depending on the knowledge and assumptions of the modeler and the availability and quality of data.     

Bromate in chlorinated drinking waters: occurrence and implications for future regulation

Bromate is a contaminant of commercially produced solutions of sodium hypochlorite used for disinfection of drinking water. However, no methodical approach has been carried out in U.S. drinking waters to determine the impact of such contamination on drinking water quality. This study utilized a recently developed method for quantitation of bromate down to 0.05 microg/L to determine the concentration of bromate present in finished waters that had been chlorinated using hypochlorite. Forty treatment plants throughout the United States using hypochlorite in the disinfection step were selected and the levels of bromate in the water both prior to and following the addition of hypochlorite were measured. The levels of bromate in the hypochlorite feedstock were also measured and together with the dosage information provided by the plants and the amount of free chlorine in the feedstock, it was possible to calculate the theoretical level of bromate that would be imparted to the water. A mass balance was performed to compare the level of bromate in finished drinking water samples to that found in the corresponding hypochlorite solution used for treatment. Additional confirmation of the source of elevated bromate levels was provided by monitoring for an increase in the level of chlorate, a co-contaminant of hypochlorite, atthe same point in the treatment plant where bromate was elevated. This study showed that bromate in hypochlorite-treated finished waters varies across the United States based on the source of the chemical feedstock, which can add as much as 3 microg/L bromate into drinking water. Although this is within the current negotiated industry standard that allows up to 50% of the maximum contaminant level (MCL) for bromate in drinking water to be contributed by hypochlorite, it would be a challenge to meet a tighter standard. Given that distribution costs encourage utilities to purchase chemical feedstocks from local suppliers, utilities in certain regions of the United States may be put at a distinct disadvantage if future lower regulations on bromate levels in finished drinking water are put into place. Moreover, with these contaminant levels it would be almost impossible to lower the maximum permissible contribution to bromate in finished water from hypochlorite to 10% of the MCL, which is the norm for other treatment chemicals. Until this issue is resolved, it will be difficult to justify a lowering of the bromate MCL from its current level of 10 to 5 microg/L or lower.     

Impact of treatment processes on the removal of perfluoroalkyl acids from the drinking water production chain

The behavior of polyfluoralkyl acids (PFAAs) from intake (raw source water) to finished drinking water was assessed by taking samples from influent and effluent of the several treatment steps used in a drinking water production chain. These consisted of intake, coagulation, rapid sand filtration, dune passage, aeration, rapid sand filtration, ozonation, pellet softening, granular activated carbon (GAC) filtration, slow sand filtration, and finished drinking water. In the intake water taken from the Lek canal (a tributary of the river Rhine), the most abundant PFAA were PFBA (perfluorobutanoic acid), PFBS (perfluorobutane sulfonate), PFOS (perfluorooctane sulfonate), and PFOA (perfluorooctanoic acid). During treatment, longer chain PFAA such as PFNA (perfluorononanoic acid) and PFOS were readily removed by the GAC treatment step and their GAC effluent concentrations were reduced to levels below the limits of quantitation (LOQ) (0.23 and 0.24 ng/L for PFOS and PFNA, respectively). However, more hydrophilic shorter chain PFAA (especially PFBA and PFBS) were not removed by GAC and their concentrations remained constant through treatment. A decreasing removal capacity of the GAC was observed with increasing carbon loading and with decreasing carbon chain length of the PFAAs. This study shows that none of the treatment steps, including softening processes, are effective for PFAA removal, except for GAC filtration. GAC can effectively remove certain PFAA from the drinking water cycle.The enrichment of branched PFOS and PFOA isomers relative to non branched isomers during GAC filtration was observed during treatment. The finished water contained 26 and 19 ng/L of PFBA and PFBS. Other PFAAs were present in concentrations below 4.2 ng/L The concentrations of PFAA observed in finished waters are no reason for concern for human health as margins to existing guidelines are sufficiently large.     

Consequences of treated water recycling as regards pharmaceuticals and drugs in surface and ground waters of a medium-sized Mediterranean catchment

In Mediterranean regions where the population is rapidly growing, the risk of water resource contamination by wastewater is likely to increase. This is the case of the Hérault watershed (south of France), where the presence of treated wastewater in surface and ground waters has been shown in a previous study. To assess the consequence of these wastewater contaminations as regards pharmaceuticals and other organic compounds, 16 common pharmaceuticals (amitryptilin, acetylsalicylic acid, carbamazepine, clenbuterol, diazepam, diclofenac, doxepin, gemfibrozil, ibuprofen, imipramine, ketoprofen, naproxen, nordiazepam, paracetamol, salbutamol, and terbutalin) as well as wastewater related pollutants (caffeine, gadolinium anomaly, and boron) were analyzed in wells pumped for potable water supply and in two wastewater treatment plant (WWTP) effluents. In addition, a monitoring along the Lergue River (the main tributary of the Hérault River) was achieved to assess pharmaceutical behavior in surface waters. Pharmaceuticals and other wastewater-related contaminants are present in several reservoirs tapped for drinking water, confirming wastewater contamination; paracetamol, caffeine, and diclofenac are the most frequently detected. Paracetamol is present at rather high concentrations (up to 11 microg/L and 211 ng/L, respectively, in a wastewater effluent and in a drinking water sample). Though degradable in WWTP, caffeine is commonly encountered in surface waters and detected in highly polluted groundwater. On the contrary, acetylsalicylic acid concentrations are generally low despite a large consumption in France; this is related to its metabolism in humans and rapid degradation in the aquatic environment. The monitoring of pharmaceuticals along the Lergue River shows that dilution is sufficient to decrease pharmaceutical values.     

Impact of artificial recharge on dissolved noble gases in groundwater in California

Dissolved noble gas concentrations in groundwater can provide valuable information on recharge temperatures and enable 3H-3He age-dating with the use of physically based interpretive models. This study presents a large (905 samples) data set of dissolved noble gas concentrations from drinking water supply wells throughout California, representing a range of physiographic, climatic, and water management conditions. Three common interpretive models (unfractionated air, UA; partial re-equilibration, PR; and closed system equilibrium, CE) produce systematically different recharge temperatures or ages; however, the ability of the different models to fit measured data within measurement uncertainty indicates that goodness-of-fit is not a robust indicator for model appropriateness. Therefore caution is necessary when interpreting model results. Samples from multiple locations contained significantly higher Ne and excess air concentrations than reported in the literature, with maximum excess air tending toward 0.05 cm3 STP g(-1) (deltaNe approximately 400%). Artificial recharge is the most plausible cause of the high excess air concentrations. The ability of artificial recharge to dissolve greater amounts of atmospheric gases has important implications for oxidation-reduction dependent chemical reactions. Measured gas concentration ratios suggest that diffusive degassing may have occurred. Understanding the physical processes controlling gas dissolution during groundwater recharge is critical for optimal management of artificial recharge and for predicting changes in water quality that can occur following artificial recharge.     

饮用水生物性污染物快速检测技术研究进展

饮用水微生物安全问题大多源于细菌、病毒、原生动物和藻类等生物性污染。加强饮用水生物性污染物的检测与监测, 防止消费者饮用存在生物性污染的水, 对保障饮用水的生物性安全具有十分重要的意义。当前饮用水微生物检测工作中, 主要采用国标检测方法对4项常规微生物及2项非常规微生物指标进行检测, 存在指标覆盖不全、耗时较长、操作复杂等不足, 难以满足饮用水生物性污染物监测的现实需求。因此, 本文重点对饮用水生物性污染物的各种快速检测与筛查技术, 如微生物快速测试片检测技术、生物荧光检测技术、流式细胞仪检测技术、PCR检测技术、等温扩增检测技术、基因芯片检测技术、高通量测序检测技术等进行综述、比较与探讨, 以期为饮用水中生物性污染物快速检测与筛查提供适宜的技术参考基础。     

Bacterial community structure in the drinking water microbiome is governed by filtration processes

The bacterial community structure of a drinking water microbiome was characterized over three seasons using 16S rRNA gene based pyrosequencing of samples obtained from source water (a mix of a groundwater and a surface water), different points in a drinking water plant operated to treat this source water, and in the associated drinking water distribution system. Even though the source water was shown to seed the drinking water microbiome, treatment process operations limit the source water's influence on the distribution system bacterial community. Rather, in this plant, filtration by dual media rapid sand filters played a primary role in shaping the distribution system bacterial community over seasonal time scales as the filters harbored a stable bacterial community that seeded the water treatment processes past filtration. Bacterial taxa that colonized the filter and sloughed off in the filter effluent were able to persist in the distribution system despite disinfection of finished water by chloramination and filter backwashing with chloraminated backwash water. Thus, filter colonization presents a possible ecological survival strategy for bacterial communities in drinking water systems, which presents an opportunity to control the drinking water microbiome by manipulating the filter microbial community. Grouping bacterial taxa based on their association with the filter helped to elucidate relationships between the abundance of bacterial groups and water quality parameters and showed that pH was the strongest regulator of the bacterial community in the sampled drinking water system.     

Life cycle assessment for sustainable metropolitan water systems planning

Life Cycle Assessment (LCA) is useful as an information tool for the examination of alternative future scenarios for strategic planning. Developing a life cycle assessment for a large water and wastewater system involves making methodological decisions about the level of detail which is retained through different stages of the process. In this article we discuss a methodology tailored to strategic planning needs which retains a high degree of model segmentation in order to enhance modeling of a large, complex system. This is illustrated by a case study of Sydney Water, which is Australia's largest water service provider. A prospective LCA was carried out to examine the potential environmental impacts of Sydney Water's total operations in the year 2021. To our knowledge this is the first study to create an LCA model of an integrated water and wastewater system with this degree of complexity. A "base case" system model was constructed to represent current operating assets as augmented and upgraded to 2021. The base case results provided a basis for the comparison of alternative future scenarios and for conclusions to be drawn regarding potential environmental improvements. The scenarios can be roughly classified in two categories: (1) options which improve the environmental performance across all impact categories and (2) options which improve one indicator and worsen others. Overall environmental improvements are achieved in all categories by the scenarios examining increased demand management, energy efficiency, energy generation, and additional energy recovery from biosolids. The scenarios which examined desalination of seawater and the upgrades of major coastal sewage treatment plants to secondary and tertiary treatment produced an improvement in one environmental indicator but deteriorations in all the other impact categories, indicating the environmental tradeoffs within the system. The desalination scenario produced a significant increase in greenhouse gas emissions due to coal-fired electricity generation for a small increase in water supply. Assessment of a greenfield scenario incorporating water demand management, on-site treatment, local irrigation, and centralized biosolids treatment indicates significant environmental improvements are possible relative to the assessment of a conventional system of corresponding scale.     

Compliance work for food contact materials: feasibility of the legally required safety assessment of an epoxy/amine-based coating for domestic water pipe restoration

Options were explored for fulfilling the legally required safety assessment for a widely applied epoxy/amine coating used for restoring corroded domestic drinking water supply systems. The coating was made up of two components mixed shortly before application, the first mainly consisting of bisphenol A diglycidyl ether (BADGE), the second of various amines. The analytically identified starting substances were all authorised, but only constituted a small proportion of the low molecular mass material left after curing and potentially migrating into water. Reaction products synthesised from constituents of the starting components (expected oligomers) could not be eluted from GC even after derivatisation, indicating that standard GC-MS screening would miss most potential migrants. They were detectable by size exclusion chromatography (SEC) after acetylation. HPLC with MS or fluorescence detection was possible for constituents including a BADGE moiety, but phenalkamines could not be detected with adequate sensitivity. Possibilities for determining long-term migration relevant for chronic toxicity are discussed. Analysis in water shortly after application of the coating overestimates migration if migration decreases over time and requires detection limits far out of reach. Analysis of a solvent extract of the coating is easier and provides an upper estimate of what could migrate into the drinking water over the years. However, to satisfy the regulatory requirements, components of the complex mixture need to be identified at lower proportions than those accessible. In vitro testing of the whole mixture for genotoxicity is expected to fail because of the required sensitivity and the glycidyl functions probably wrongly resulting in positive tests. The difficulties in dealing with this situation are discussed.     

自动SPME-GCMS法分析生活饮用水中臭味物质土臭素和2-甲基异莰醇

如果饮用水中的土臭素与2-甲基异莰醇的含量超标,往往会造成致嗅现象。因此,供水企业对这类嗅味物质的有效去除一直十分关注。在实践中,通过传统方法很难实现有效去除,且对这类嗅味物质的检测与分析也存在诸多不足。本文应用自动SPME技术连接thermo scientifi cTM ISQ 7000 GCMS,实现了对2-甲基异莰醇和土臭素的高效率、高灵敏度的检测,其最低检出质量浓度分别为1.0 ng/L和0.49 ng/L,满足饮用水中土臭素和2-甲基异莰醇的检测要求。     

Testing tubewell platform color as a rapid screening tool for arsenic and manganese in drinking water wells

A low-cost rapid screening tool for arsenic (As) and manganese (Mn) in groundwater is urgently needed to formulate mitigation policies for sustainable drinking water supply. This study attempts to make statistical comparison between tubewell (TW) platform color and the level of As and Mn concentration in groundwater extracted from the respective TW (n = 423), to validate platform color as a screening tool for As and Mn in groundwater. The result shows that a black colored platform with 73% certainty indicates that well water is safe from As, while with 84% certainty a red colored platform indicates that well water is enriched with As, compared to WHO drinking water guideline of 10 μg/L. With this guideline the efficiency, sensitivity, and specificity of the tool are 79%, 77%, and 81%, respectively. However, the certainty values become 93% and 38%, respectively, for black and red colored platforms at 50 μg/L, the drinking water standards for India and Bangladesh. The respective efficiency, sensitivity, and specificity are 65%, 85%, and 59%. Similarly for Mn, black and red colored platform with 78% and 64% certainty, respectively, indicates that well water is either enriched or free from Mn at the Indian national drinking water standard of 300 μg/L. With this guideline the efficiency, sensitivity, and specificity of the tool are 71%, 67%, and 76%, respectively. Thus, this study demonstrates that TW platform color can be potentially used as an initial screening tool for identifying TWs with elevated dissolved As and Mn, to make further rigorous groundwater testing more intensive and implement mitigation options for safe drinking water supplies.     

Eubacterial 16S-rDNA amplicon profiling: a rapid technique for comparison and differentiation of heterotrophic plate count communities from drinking water

Determination of the heterotrophic plate count (HPC) is commonly used as a surrogate to assess the general microbial water quality in drinking water. For routine monitoring applications, the HPC is investigated in a quantitative way. However, qualitative data about the HPC bacterial community composition and/or population dynamics are required for particular situations. In order to provide fast and efficient qualitative approaches, molecular biological DNA profiling techniques seem to be suitable tools for the analysis of the total HPC community composition. In this work a DNA profiling technique is presented, which was recently demonstrated by our group to have potential for the rapid qualitative comparison and differentiation of HPC communities from raw and drinking water. The presented approach consists of a polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE) for the generation of 16S-rDNA amplicon fingerprints from whole HPC community DNA extracts. In the context of this proceeding, the methodical background is presented and possible scientific merits as well as potential water management applications are discussed. Selected examples of (i) the demonstration of selective growth of HPC populations on different media and the comparison to the total in situ drinking water eubacterial community, (ii) the screening for HPC community variations at different locations of a drinking water distribution system, and (iii) the influence assessment on groundwater HPC communities by an infiltrating treated sewage effluent (bacterial source tracking) are given.     

2004 National Atrazine Occurrence Monitoring Program using the Abraxis ELISA method

The goal of this project was to gain a better understanding of atrazine occurrence in the United States by surveying drinking water utilities' sources and finished water for atrazine on a weekly basis for seven months. Atrazine is a contaminant of interest because the United States Environmental Protection Agency (USEPA) has found short-term atrazine exposure above the drinking water maximum contaminant level (MCL) to potentially cause heart, lung, and kidney congestion, low blood pressure, muscle spasms, weight loss, and damage to the adrenal glands. Long-term exposure to atrazine concentrations above the drinking water MCL has been linked to weight loss, cardiovascular damage, retinal and muscle degeneration, and cancer. This survey effort improved upon previously conducted atrazine surveys through intensive, high frequency sampling (participating plants sampled their raw and finished water on a weekly basis for approximately seven months). Such an intensive effort allowed the authors to gain a better understanding of short-term atrazine occurrence and its variability in drinking water sources. This information can benefit the drinking water industry by facilitating (1) better atrazine occurrence management (i.e., awareness when plants may be more susceptible to atrazine), (2) more efficient atrazine control (e.g., effective treatment alternatives and more effective response to atrazine occurrence), and (3) treatment cost reduction (e.g., efficient atrazine control can result in substantial cost savings). Forty-seven drinking watertreatment plants located primarily in the Midwestern United States participated in the survey and sampled their raw and finished water on a weekly basis from March through October. Samples were analyzed using the Abraxis enzyme-linked immunosorbent assay (ELISA) test kit. Confirmation samples for quality assurance/quality control (QA/QC) purposes were analyzed using solid-phase extraction (SPE) followed by gas chromatography mass spectrophotometry (GC/MS). Several important conclusions can be drawn from this study including (1) surface waters were confirmed to be more vulnerable to atrazine contamination than groundwater sources, (2) peak atrazine concentrations corresponded well to precipitation/runoff events, and (3) atrazine occurrence tended to be uniform geographically when compared by river drainage basins. In addition, this project confirmed that the Abraxis atrazine ELISA test kit tended to have a positive bias (i.e., the measured ELISA concentration was higher than the actual concentration) in most measured samples. Finished samples tended to have more of a positive bias than raw water samples. Therefore, this bias may limit the effectiveness for ELISA for regulatory monitoring. There are many other applications for ELISA, however, including frequent monitoring for early detections of atrazine concentration changes that might trigger conventional analysis by GC/MS or be used for activated carbon dosing or other treatment operating controls.