Analytical issues in monitoring drinking-water contamination related to short-term, heavy rainfall events

High sensitivity on-site early warning system monitoring of pesticides by photo-induced fluorescence

This paper describes the prototype of an on-site High Sensitivity Early Warning Monitoring System, using Photo-Induced Fluorescence, for pesticide monitoring in natural waters (HSEWPIF). To obtain a high sensitivity, the prototype was designed with four main features. Four UV LEDs are used to excite the photoproducts at different wavelengths and select the most efficient one. Two UV LEDs are used simultaneously at each wavelength to increase the excitation power and then the fluorescence emission of the photoproducts. High-pass filters are used to avoid the saturation of the spectrophotometer and to increase the signal-to-noise ratio. The HSEWPIF prototype also employs UV absorption to detect any occasional increase of suspended and dissolved organic matter, which could disrupt the fluorescence measurement. The conception of this new experimental set-up is explained and described, then analytical applications are carried out online for the determination of fipronil and monolinuron. We obtained a linear calibration range from 0 to 3 μg mL^-1 with limits of detection of 1.24 ng mL^-1 for fipronil and 0.32 ng mL^-1 for monolinuron. A mean recovery of 99.2% for fipronil and 100.9% for monolinuron show that the method is accurate, moreover a standard deviation of 1.96% for fipronil and 2.49% for monolinuron show that the method is repeatable. Compared to other methods for the determination of pesticides by photo-induced fluorescence, the HSEWPIF prototype has good sensitivity with better limits of detection, and good analytical performances. These results show that HSEWPIF can be used for monitoring pesticide in natural waters to protect industrial facilities against accidental contamination.

Impacts of climate change on drinking water quality in Norway

Climate change will lead to higher temperatures, increased precipitation and runoff, as well as more intense and frequent extreme weather events in Norway. More extreme rainfall and increased runoff are historically associated with higher concentrations of indicator bacteria, colour and turbidity in raw water of Norwegian waterworks. Regional information about the risk for drinking water deterioration by the end of the century is essential for evaluating potential treatment capacity upgrades at the waterworks. We combined locally downscaled future climate scenarios with historical associations between weather/runoff and water quality from a wide spread of waterworks in Norway. With continued climate change, we estimate higher concentrations of water quality indicators of raw water by the end of the century. The water quality is estimated to deteriorate mainly due to the projected increase in rainfall, and mainly in the Western and Northern parts of Norway. While large waterworks seem to be able to adapt to future conditions, the degradation of raw water quality may cause future challenges for the treatment processes at smaller waterworks. Combining these results with further studies of treatment effects and microbial risk assessments is needed to ensure sufficient treatment capacities of the raw water in the future.

Automated Targeted Sampling of Waterborne Pathogens and Microbial Source Tracking Markers Using Near-Real Time Monitoring of Microbiological Water Quality

Waterborne pathogens are heterogeneously distributed across various spatiotemporal scales in water resources, and representative sampling is therefore crucial for accurate risk assessment. Since regulatory monitoring of microbiological water quality is usually conducted at fixed time intervals, it can miss short-term fecal contamination episodes and underestimate underlying microbial risks. In the present paper, we developed a new automated sampling methodology based on near real-time measurement of a biochemical indicator of fecal pollution. Online monitoring of β-D-glucuronidase (GLUC) activity was used to trigger an automated sampler during fecal contamination events in a drinking water supply and at an urban beach. Significant increases in protozoan parasites, microbial source tracking markers and E. coli were measured during short-term (<24 h) fecal pollution episodes, emphasizing the intermittent nature of their occurrence in water. Synchronous triggering of the automated sampler with online GLUC activity measurements further revealed a tight association between the biochemical indicator and culturable E. coli. The proposed event sampling methodology is versatile and in addition to the two triggering modes validated here, others can be designed based on specific needs and local settings. In support to regulatory monitoring schemes, it should ultimately help gathering crucial data on waterborne pathogens more efficiently during episodic fecal pollution events.

Micellar enhanced photo-induced fluorescence and absorbance for the development of an on-site early warning water quality monitoring system for pesticides

This paper describes two prototypes of an on-site Early Warning Water Quality Monitoring System (EWWQMS) for pesticide quantification in natural waters. As many pesticides are non-fluorescent, the EWWQMS setup uses UV photoconversion to form highly fluorescent photoproducts. To enhance sensitivity, the two prototypes use micellar-enhanced fluorescence with surfactant (cetyl trimethyl ammonium chloride) in aqueous solution. To improve specificity, four UV LEDs at different wavelengths then excite the fluorescent photoproducts. The EWWQMS prototypes also employ UV absorption for quantification of non-photosensitive pesticides. The first prototype detects the pesticides via a diode array spectrometer. The second system is developed with higher resolution spectrometer and an intensified CCD camera detection to improve the sensitivity of the method. These experimental set-ups are described, explained and tested. Analytical applications were carried out online in CTAC aqueous solution, for the determination of isoproturon, flufenoxuron and profenofos. The calibration curves obtained are linear over one order of magnitude, and the detection limits are in the ng mL-1 range. The analytical performances of these new methods are good compared with other published classical micellar enhanced photo-induced fluorescence methods for the determination of pesticides in aqueous solutions. Our results show that these EWWQMS prototypes can be used as a warning system to protect against pesticide contamination exceeding the threshold of treatment capabilities at industrial facilities using natural waters.

Campylobacter jejuni Strains Associated with Wild Birds and Those Causing Human Disease in Six High-Use Recreational Waterways in New Zealand

Campylobacter jejuni, a leading cause of gastroenteritis worldwide, has been frequently isolated from recreational rivers and streams in New Zealand, yet the public health significance of this is unknown. This study uses molecular tools to improve our understanding of the epidemiology and sources of Campylobacter in recreational waterways, with a view to preventing human infection. Epidemiological and microbiological data were collected between 2005 and 2009 from six high-use recreational waterways in the Manawatu-Wanganui region of the North Island. Campylobacter spp. and C. jejuni were isolated from 33.2% and 20.4% of 509 samples, respectively. Isolation of Campylobacter was observed in both low and high river flows. After adjusting for the confounding effects of river flow, there was a significantly higher likelihood of isolating Campylobacter in the winter month of June compared to January. A high diversity of C. jejuni multilocus sequence types was seen, with the most commonly isolated being the water rail-associated ST-2381 (19/91 isolates [20.9%]), ST-1225 (8/91 isolates [8.8%]), and ST-45 (6/91 isolates [6.6%]). The ST-2381 was found in all rivers, while the most commonly isolated ST from human cases in New Zealand, the poultry-associated strain ST-474, was isolated only in one river. Although the majority of Campylobacter sequence types identified in river water were strains associated with wild birds that are rarely associated with human disease, poultry and ruminant-associated Campylobacter strains that are found in human infection were also identified and could present a public health risk.IMPORTANCE In 2016, there was a large-scale waterborne outbreak of campylobacteriosis in New Zealand, which was estimated to have affected over 5,000 people. This highlighted the need for a greater understanding of the sources of contamination of both surface and groundwater and risks associated with exposure to both drinking and recreational water. This study reports the prevalence and population structure of Campylobacter jejuni in six recreational waters of the Manawatu-Wanganui region of New Zealand and models the relationship between Campylobacter spp. and ruminant-associated Campylobacter and the parameters "sites," "months," and "river flow." Here, we demonstrate that both low and high river flows, month of the year, and recreational sites could influence the Campylobacter isolation from recreational waters. The presence of genotypes associated with human infection allowed us to describe potential risks associated with recreational waters.

Methods for Sample Collection, Storage, and Analysis of Freshwater Phosphorus

Although phosphorus (P) is an essential nutrient for biological productivity, it can cause freshwater degradation when present at fairly low concentrations. Monitoring studies using continuous sampling is crucial for documenting P dynamics in freshwater ecosystems and to reduce the risk of eutrophication. Despite literature updates of developments of the analytical methods for measurement of P species in natural waters, there has been no comprehensive review addressing freshwater sample collection, sample preparation, and sample treatment to fractionate and characterize different forms of P. Therefore, this paper aims to elaborate the different techniques for freshwater sampling and to introduce alternative laboratory methods for sample preservation and P fractionation. The advantages and disadvantages of various sampling techniques, including the traditional manual and the recently developed automatic and passive methods, are presented to highlight the importance of collecting representative freshwater samples. Furthermore, we provide suggestions for sample pretreatment, including filtration, transportation, and storage steps to minimize microbial activity and to maximize the accuracy of measurement of various P fractions. Finally, the most common laboratory methods to measure dissolved and particulate as well as the organic and inorganic freshwater P fractions are efficiently provided. Using this guide, a comprehensive monitoring program of P dynamics in freshwater ecosystems can be developed and applied to improve water quality, particularly of P-rich freshwaters.

Variable responses of dissolved organic carbon to precipitation events in boreal drinking water lakes

In boreal regions, increased concentrations of dissolved organic carbon (DOC) have been linked to extreme wet years; however, less is known about the extent to which precipitation events are altering DOC concentration and quality. We assessed the effects of rain events on a suite of six lakes in Maine, U.S.A., to better understand how events alter DOC quantity and quality. DOC concentrations and DOC quality (measured as DOC-specific absorption coefficients (Specific Ultraviolet Absorbance (SUVA₂₅₄ (also a*₂₅₄), a*₃₂₀, and a*₃₈₀)) were quantified 24 h before, and at three time points (24-48 h, 5-7 days, and 3 weeks) after five different precipitation events. Our results revealed three types of responses across the lakes: (1) an initial spike in DOC concentrations of 30-133% and in the three quality metrics of 20-86% compared to pre-storm levels, followed by return to pre-storm concentrations; (2) a sustained increase in DOC concentrations (by 4-23%) and an increase in the three DOC quality metrics (by 1-43%) through the second post-storm sampling, with concentrations falling by the third post-storm sampling compared to pre-storm levels; and (3) no change during all sampling periods. Lake residence time was a key driver of changes in DOC concentration and DOC quality in response to storm events. Our research provides evidence that precipitation events contribute to short-term abrupt changes in DOC quantity and quality that are largely driven by key landscape and lake characteristics. These changes in DOC may have important implications for management of water utilities, including alteration or implementation of treatment strategies.

Development of a new automatic on-site detector of pesticides in natural waters by photo induced fluorescence, application to three phenylurea and benzoylurea herbicide

Prototypes of on-site automatic photo induced fluorescence detectors of pesticide in natural waters are set up and applied for the determination of the benzoyl- and phenylurea pesticides, namely fluometuron, monolinuron and diflubenzuron. As these pesticides present no native fluorescence the set up system use the photo conversion under UV irradiation of these pesticides into highly fluorescent photoproducts. A first system, called AUTOPIF, (evolution the commercial AQUAPOD system) is develop using a detection via a diode array spectrometer. To improve the sensitivity of the method, a second system, called AUTOPIF+, is developed with a more resolute spectrometer and an intensified CCD camera detection. Analytical applications were carried out in aqueous solution and detected on line with the AUTOPIF and AUTOPIF+ system. The calibration curves are linear over one order of magnitude, and the limits of detection are in the μg mL^-1 range. The analytical performances of these methods for the determination of the three pesticides are satisfactory in comparison to other classical PIF methods published for the determination of phenylurea pesticides in aqueous solutions. Our results show that the AUTOPIF and AUTOPIF+ methods are versatile, sensible and can be easily applied as an alert system to detect pollutant residues in naturals waters over a threshold value.

Daily variation of heavy metal contamination and its potential sources along the major urban wastewater channel in Kampala, Uganda

Heavy metal pollution from untreated industrial wastewater has become a major concern to the environment and public health in many rapidly growing cities in low-income countries. Previous studies on heavy metals of urban wastewater systems have focused on long-term (weekly or seasonal) variations, while only few studies investigated short-term (daily) variation to capture potential bulk discharges. To monitor and enforce wastewater discharge regulations and reduce industrial pollution, a better understanding of the short-term variation of these pollutants and industrial discharge practices is needed. The aim of this study is to assess the daily variation of heavy metals and physicochemical parameters along the major urban wastewater system in Kampala, Uganda. Over 1 week, daily water samples were collected at 16 locations and analyzed for lead (Pb), mercury (Hg), copper (Cu), and chromium (Cr) and a range of physicochemical parameters. Additionally, 25 key informant interviews with industries were administered to investigate their potential to contaminate the environment. Among 78 water samples, 29 exceeded the national standards for Pb (> 0.1 mg/L) and one for Hg (> 0.01 mg/L). High daily variation and peak concentrations were detected which are likely due to industries retaining their effluents and discharging them irregularly. Although 24 industries used heavy metals in their manufacturing processes and are likely to discharge heavy metals, only ten industries had a wastewater treatment system in place. Our results show that repeated measurements of heavy metals over short time intervals are needed to capture their high daily variation in an urban wastewater system. Furthermore, there is an urgent need to register industries and to assess their effluent composition in order to select appropriate wastewater management measures.

Variability of disinfection by-products at a full-scale treatment plant following rainfall events

The quality of drinking water sources can decrease when contaminants are transported by overland and subsurface flow and discharged into surface waters following rainfall events. Increases in organic contaminants such as road salts and organic matter may occur and potentially modify disinfection by-products (DBPs) concentration and speciation. This study investigated the effects of various spring rainfall events on the quality of treated waters at a large water treatment plant through the implementation of intensive water quality monitoring of raw, filtered and treated waters during different rainfall events. DBPs (four trihalomethanes and six haloacetic acids) and their explanatory variables (pH, turbidity, water temperature, specific ultraviolet absorbance, total and dissolved organic carbon, bromide and chlorine dose) were measured during four rainfall events. The results showed that water quality degrades during and following rainfall, leading to small increases in trihalomethanes (THM4) and haloacetic acids (HAA6) in treated waters. While THM4 and HAA6 levels remained low during the pre-rainfall period (<9 μg/L) for the four sampling campaigns, small increases in THM4 and HAA6 during and after spring rainfall events were observed. During the rainfall and post-rainfall periods, concentration peaks corresponding to 3-fold and 2-fold increases (respectively 27.5 μg/L for THM4 and 12.6 μg/L for HAA6) compared to pre-rainfall levels were also measured. A slight decrease in harmful brominated THM and HAA proportion was also observed following rainfall events.

Online flow cytometry reveals microbial dynamics influenced by concurrent natural and operational events in groundwater used for drinking water treatment

Detailed measurements of physical, chemical and biological dynamics in groundwater are key to understanding the important processes in place and their influence on water quality – particularly when used for drinking water. Measuring temporal bacterial dynamics at high frequency is challenging due to the limitations in automation of sampling and detection of the conventional, cultivation-based microbial methods. In this study, fully automated online flow cytometry was applied in a groundwater system for the first time in order to monitor microbial dynamics in a groundwater extraction well. Measurements of bacterial concentrations every 15 minutes during 14 days revealed both aperiodic and periodic dynamics that could not be detected previously, resulting in total cell concentration (TCC) fluctuations between 120 and 280 cells μL⁻¹. The aperiodic dynamic was linked to river water contamination following precipitation events, while the (diurnal) periodic dynamic was attributed to changes in hydrological conditions as a consequence of intermittent groundwater extraction. Based on the high number of measurements, the two patterns could be disentangled and quantified separately. This study i) increases the understanding of system performance, ii) helps to optimize monitoring strategies, and iii) opens the possibility for more sophisticated (quantitative) microbial risk assessment of drinking water treatment systems.

Experimental disinfection by-product formation potential following rainfall events

Spring rainfall events can have deleterious impacts on raw and drinking water quality for water treatment plants that use surface waters. This study compares the influence of land use and climate on DBP precursors in two catchments supplying the region around the City of Québec, Canada, and assesses the variability of Disinfection By-Product (DBP) concentration and speciation following rainfall events. DBPs (trihalomethanes (THMs) and haloacetic acids (HAAs)) and their precursors in raw waters (pH, turbidity, specific ultraviolet absorbance (SUVA), total and dissolved organic carbon, bromides and chlorine dose) were monitored. Various experimental chlorination tests, DBP formation potential (DBPFP) and Simulated Distribution Systems (SDS), were also performed. Differences in pre-rainfall (baseflow) water quality were noted according to the different watershed land uses. Raw water quality patterns showed modifications between baseflow and rainfall periods, with a degradation of raw water quality according to turbidity and SUVA in both water sources. Rainfall events were also shown to alter organic matter reactivity with an increase in THM formation potential for both sites. A less noticeable impact on HAA formation potential was observed. However, no clear differences in DBPFP tests were observed between the sites. SDS tests showed that rainfall events lead to considerable rises in organic carbon reactivity of filtered waters, even after primary treatment, with a 2-fold increase in THM and HAA concentrations following rainfall for waters representing the end of one main distribution system (20 h contact time). These increases are linked mainly to a rise in non-brominated DBPs such as chloroform, trichloroacetic acid and dichloroacetic acid. This study confirms the importance of strictly controlling OM levels during drinking water treatment to ensure safe drinking water quality throughout the distribution system.

Automatic High Frequency Monitoring for Improved Lake and Reservoir Management

Recent technological developments have increased the number of variables being monitored in lakes and reservoirs using automatic high frequency monitoring (AHFM). However, design of AHFM systems and posterior data handling and interpretation are currently being developed on a site-by-site and issue-by-issue basis with minimal standardization of protocols or knowledge sharing. As a result, many deployments become short-lived or underutilized, and many new scientific developments that are potentially useful for water management and environmental legislation remain underexplored. This Critical Review bridges scientific uses of AHFM with their applications by providing an overview of the current AHFM capabilities, together with examples of successful applications. We review the use of AHFM for maximizing the provision of ecosystem services supplied by lakes and reservoirs (consumptive and non consumptive uses, food production, and recreation), and for reporting lake status in the EU Water Framework Directive. We also highlight critical issues to enhance the application of AHFM, and suggest the establishment of appropriate networks to facilitate knowledge sharing and technological transfer between potential users. Finally, we give advice on how modern sensor technology can successfully be applied on a larger scale to the management of lakes and reservoirs and maximize the ecosystem services they provide.

Biological efficacy and toxic effect of emergency water disinfection process based on advanced oxidation technology

An innovative and removable water treatment system consisted of strong electric field discharge and hydrodynamic cavitation based on advanced oxidation technologies was developed for reactive free radicals producing and waterborne pathogens eliminating in the present study. The biological efficacy and toxic effects of this advanced oxidation system were evaluated during water disinfection treatments. Bench tests were carried out with synthetic microbial-contaminated water, as well as source water in rainy season from a reservoir of Dalian city (Liaoning Province, China). Results showed that high inactivation efficiency of Escherichia coli (>5 log) could be obtained for synthetic contaminated water at a low concentration (0.5-0.7 mg L(-1)) of total oxidants in 3-10 s. The numbers of wild total bacteria (108 × 10(3) CFU mL(-1)) and total coliforms (260 × 10(2) MPN 100 mL(-1)) in source water greatly reduced to 50 and 0 CFU mL(-1) respectively after treated by the advanced oxidation system, which meet the microbiological standards of drinking water, and especially that the inactivation efficiency of total coliforms could reach 100%. Meanwhile, source water qualities were greatly improved during the disinfection processes. The values of UV254 in particular were significantly reduced (60-80%) by reactive free radicals. Moreover, the concentrations of possible disinfection by-products (formaldehyde and bromide) in treated water were lower than detection limits, indicating that there was no harmful effect on water after the treatments. These investigations are helpful for the ecotoxicological studies of advanced oxidation system in the treatments of chemical polluted water or waste water. The findings of this work suggest that the developed water treatment system is ideal in the acute phases of emergencies, which also could offer additional advantages over a wide range of applications in water pollution control.

Transport and viability of Escherichia coli cells in clean and iron oxide coated sand following coating with silver nanoparticles

A mechanistic understanding of processes controlling the transport and viability of bacteria in porous media is critical for designing in situ bioremediation and microbiological water decontamination programs. We investigated the combined influence of coating sand with iron oxide and silver nanoparticles on the transport and viability of Escherichia coli cells under saturated conditions. Results showed that iron oxide coatings increase cell deposition which was generally reversed by silver nanoparticle coatings in the early stages of injection. These observations are consistent with short-term, particle surface charge controls on bacteria transport, where a negatively charged surface induced by silver nanoparticles reverses the positive charge due to iron oxide coatings, but columns eventually recovered irreversible cell deposition. Silver nanoparticle coatings significantly increased cell inactivation during transit through the columns. However, when viability data is normalised to volume throughput, only a small improvement in cell inactivation is observed for silver nanoparticle coated sands relative to iron oxide coating alone. This counterintuitive result underscores the importance of net surface charge in controlling cell transport and inactivation and implies that the extra cost for implementing silver nanoparticle coatings on porous beds coated with iron oxides may not be justified in designing point of use water filters in low income countries.

A decision support system for drinking water production integrating health risks assessment

The issue of drinking water quality compliance in small and medium scale water services is of paramount importance in relation to the 98/83/CE European Drinking Water Directive (DWD). Additionally, concerns are being expressed over the implementation of the DWD with respect to possible impacts on water quality from forecast changes in European climate with global warming and further anticipated reductions in north European acid emissions. Consequently, we have developed a decision support system (DSS) named ARTEM-WQ (AwaReness Tool for the Evaluation and Mitigation of drinking Water Quality issues resulting from environmental changes) to support decision making by small and medium plant operators and other water stakeholders. ARTEM-WQ is based on a sequential risk analysis approach that includes consideration of catchment characteristics, climatic conditions and treatment operations. It provides a holistic evaluation of the water system, while also assessing human health risks of organic contaminants potentially present in treated waters (steroids, pharmaceuticals, pesticides, bisphenol-a, polychlorobiphenyls, polycyclic aromatic hydrocarbons, petrochemical hydrocarbons and disinfection by-products; n = 109). Moreover, the system provides recommendations for improvement while supporting decision making in its widest context. The tool has been tested on various European catchments and shows a promising potential to inform water managers of risks and appropriate mitigative actions. Further improvements should include toxicological knowledge advancement, environmental background pollutant concentrations and the assessment of the impact of distribution systems on water quality variation.

The impact of climate change on the treatability of dissolved organic matter (DOM) in upland water supplies: a UK perspective

Climate change in the UK is expected to cause increases in temperatures, altered precipitation patterns and more frequent and extreme weather events. In this review we discuss climate effects on dissolved organic matter (DOM), how altered DOM and water physico-chemical properties will affect treatment processes and assess the utility of techniques used to remove DOM and monitor water quality. A critical analysis of the literature has been undertaken with a focus on catchment drivers of DOM character, removal of DOM via coagulation and the formation of disinfectant by-products (DBPs). We suggest that: (1) upland catchments recovering from acidification will continue to produce more DOM with a greater hydrophobic fraction as solubility controls decrease; (2) greater seasonality in DOM export is likely in future due to altered precipitation patterns; (3) changes in species diversity and water properties could encourage algal blooms; and (4) that land management and vegetative changes may have significant effects on DOM export and treatability but require further research. Increases in DBPs may occur where catchments have high influence from peatlands or where algal blooms become an issue. To increase resilience to variable DOM quantity and character we suggest that one or more of the following steps are undertaken at the treatment works: a) 'enhanced coagulation' optimised for DOM removal; b) switching from aluminium to ferric coagulants and/or incorporating coagulant aids; c) use of magnetic ion-exchange (MIEX) pre-coagulation; and d) activated carbon filtration post-coagulation. Fluorescence and UV absorbance techniques are highlighted as potential methods for low-cost, rapid on-line process optimisation to improve DOM removal and minimise DBPs.

Suitability of optical, physical and chemical measurements for detection of changes in bacterial drinking water quality

In this study, different optical, physical and chemical measurements were tested for their capacity to detect changes in water quality. The tests included UV-absorbance at 254 nm, absorbance at 420 nm, turbidity, particle counting, temperature, pH, electric conductivity (EC), free chlorine concentration and ATP concentration measurements. Special emphasis was given to investigating the potential for measurement tools to detect changes in bacterial concentrations in drinking water. Bacterial colony counts (CFU) and total bacterial cell counts (TBC) were used as reference methods for assessing the bacterial water quality. The study consists of a series of laboratory scale experiments: monitoring of regrowth of Pseudomonas fluorescens, estimation of the detection limits for optical measurements using Escherichia coli dilutions, verification of the relationships by analysing grab water samples from various distribution systems and utilisation of the measurements in the case of an accidentally contaminated distribution network. We found significant correlations between the tested measurements and the bacterial water quality. As the bacterial contamination of water often co-occurs with the intrusion of matrixes containing mainly non-bacterial components, the tested measurement tools can be considered to have the potential to rapidly detect any major changes in drinking water quality.

Emergency water supply: a review of potential technologies and selection criteria

Access to safe drinking water is one of the first priorities following a disaster. However, providing drinking water to the affected population (AP) is challenging due to severe contamination and lack of access to infrastructure. An onsite treatment system for the AP is a more sustainable solution than transporting bottled water. Emergency water technologies (WTs) that are modular, mobile or portable are suitable for emergency relief. This paper reviews WTs including membrane technologies that are suitable for use in emergencies. Physical, chemical, thermal- and light-based treatment methods, and membrane technologies driven by different driving forces such as pressure, temperature and osmotic gradients are reviewed. Each WT is evaluated by ten mutually independent criteria: costs, ease of deployment, ease of use, maintenance, performance, potential acceptance, energy requirements, supply chain requirements, throughput and environmental impact. A scoring system based on these criteria is presented. A methodology for emergency WT selection based on compensatory multi-criteria analysis is developed and discussed. Finally, critical research needs are identified.