Production Of Safe Drinking Water Research Articles

Achieving low concentrations of chromium in drinking water by nanofiltration: membrane performance and selection.

This study evaluates nanofiltration as a feasible process to reach low concentrations of chromium in drinking water and provides means for the selection of the most suitable membrane based on the specific treatment needs. Chromium removal is concerning since new stringent limits (10μg/L) for hexavalent Cr concentration in potable water were recently adopted in various countries. Three commercial nanofiltration membranes were tested against this threshold value: two membranes made of semi-aromatic polyamide and the third having a sulfonated polyethersulfone asymmetric film as the selective layer. The rejection observed as a function of chemical composition in the feed solution suggests that electrostatic effect is an important mechanism of chromium(VI) removal for the membranes with higher surface charge and lower film density. The performance of such membranes is strongly affected by the presence of salts, especially divalent cations, which reduce both Cr(VI) rejection and the permeate flux. The removal of Cr(VI) by denser membranes is dominated by solution-diffusion and is not influenced by feed ionic strength. The exposure of membranes to high chromium concentrations and to hypochlorite, typically employed as an oxidizing agent in water treatment plants, was also investigated. An analysis of the operational membrane life is thus discussed, based on the loss in performance due to active film degradation. All three membranes showed adequate rejection of chromium from tap and well water of diverse chemical composition, suggesting that nanofiltration is an effective process to remove chromium for the production of safe drinking water. However, membranes with different properties should be adopted depending on specific feed water composition and on the productivity required from the system. A final analysis is presented to help with the choice of the most suitable nanofiltration membrane based on initial and target Cr(VI) concentration in feed and product water, respectively.

Purifying arsenic and fluoride-contaminated water by a novel graphene-based nanocomposite membrane of enhanced selectivity and sustained flux.

A novel graphene-based nanocomposite membrane was synthesized by interfacial polymerization (IP) through chemical bonding of the graphene oxide (GO) layer to polyethersulfone surface. Detailed characterization of the composite membrane through AFM, SEM, ATR-FTIR, XRD analysis, and Raman spectroscopy indicates strong potential of the membrane in highly selective removal of the toxic contaminants like arsenic and fluoride while permeating the essential minerals like calcium and magnesium. This makes the membrane suitable for production of safe drinking water from contaminated water. The membrane applied in a flat-sheet cross-flow module succeeded in removal of more than 98% arsenic and around 80% fluoride from contaminated water while selectively retaining the useful calcium and magnesium minerals in drinking water. A sustained pure water flux of around 150 LMH (liter per square meter per hour) during operation over long hours (> 150h) with only 3-5% drop in flux indicates antifouling character of the membrane module.

The rapidly growing role of UV-AOPs in the production of safe drinking water

Guest editors Stuart Khan, Graham Gagnon, Michael Templeton and Dionysios (Dion) Dionysiou introduce the Ultraviolet-based advanced oxidation processes (UV-AOPs) themed issue of Environmental Science: Water Research & Technology.

Evaluation of an environmentally sustainable UV-assisted water treatment system for the removal of Bacillus globigii spores in water.

Development of greener water treatment technologies is important for the production of safe drinking water and water security applications, such as decontamination. Chlorine assisted disinfection is common and economical, but can generate disinfection byproducts (DBPs) that may be of health concern. DBPs are formed due to the reaction of chlorine with naturally occurring organic and inorganic substances in water. Currently, various innovative technologies are being developed as alternative approaches for preventing DBPs during water treatment. In this study, we evaluated the effectiveness of a novel combination of high efficiency flow filtration and UV disinfection treatment system for the removal of Bacillus globigii (B. globigii) spores in water. The filtration system consists of a charged membrane filter (CMF) that not only helps to remove suspended particles but also reduces the impact of other impurities including bio organisms. In order to get most performance details, the CMF was evaluated at clean, half-life, and end of life (EOL) conditions along with 100% UV transmittance (UVT). In addition, the effectiveness of the UV system was evaluated as a stand alone system at 100% and 70% EOL intensity. The study was conducted at the US EPA's Test and Evaluation (T&E) Facility in Cincinnati, OH, using B. globigii, a surrogate for B. anthracis spores. This non-chemical environmentally-friendly CMF/UV combination system and the stand alone UV unit showed greater than 6.0 log removal of B. globigii during the tests.

Rapid Production of a Porous Cellulose Acetate Membrane for Water Filtration using Readily Available Chemicals

A chemistry laboratory experiment using everyday items and readily available chemicals is described to introduce advanced high school students and undergraduate college students to porous polymer membranes. In a three-step manufacturing process, a membrane is produced at room temperature. The filtration principle of the membrane is then illustrated by filtering solutions containing pigmentary watercolor or food coloring. A comparison of the filtration results shows that insoluble watercolor pigments are too large to pass the pores of the membrane and are successfully rejected by the membrane, whereas the food coloring is completely soluble in water and easily passes the membrane. The laboratory experiment can be performed in a 2 h activity and serves the purpose of (1) exposing students to a new and interesting field of material science. It (2) makes them familiar with porous membranes for the production of safe drinking water and (3) introduces them to a template-removal technique utilizing acid/base the...

The cyanotoxin-microcystins: current overview

The monocyclic heptapeptides microcystins (MCs), are a group of hepatotoxins, produced worldwide by some bloom-forming cyanobacterial species/strains both in marine and freshwater ecosystems. MCs are synthesized non-ribosomally by large multi-enzyme complexes consisting of different modules including polyketide synthases and non-ribosomal peptide synthetases, as well as several tailoring enzymes. More than 85 different variants of MCs have been reported to exist in nature. These are chemically stable, but undergo bio-degradation in natural water reservoirs. Direct or indirect intake of MCs through the food web is assumed to be a highly exposed route in risk assessment of cyanotoxins. MCs are the most commonly found cyanobacterial toxins that cause a major challenge for the production of safe drinking water and pose a serious threat to global public health as well as fundamental ecological processes due to their potential carcinogenicity. Here, we emphasize recent updates on different modes of action of their possible carcinogenicity. Besides the harmful effects on human and animals, MC producing cyanobacteria can also present a harmful effect on growth and development of agriculturally important plants. Overall, this review emphasizes the current understanding of MCs with their occurrence, geographical distribution, accumulation in the aquatic as well as terrestrial ecosystems, biosynthesis, climate-driven changes in their synthesis, stability and current aspects on its degradation, analysis, mode of action and their ecotoxicological effects.

Feasibility assessment of surface water disinfection by ultrafiltration

Ultrafiltration (UF) has been presented as an alternative to chemical disinfection to obtain safe drinking water, for its ability to remove microbiological contamination. Hollow-fiber UF membranes are designed as an effective barrier to microorganisms, for their high manufacturing integrity and for the ‘potting’ method adopted to seal fibers to the feeding/extraction manifold. While the main advantage over chemical disinfection is the drastic reduction of disinfection-by-product (DBP) formation, some chemicals are still required to control fouling and related sanitary risks. This study aims at an up-to-date assessment of UF use for surface water disinfection by compact, minimally-attended, automated plants. A 3.5 m3/h automated UF pilot-plant was run for 8 months for drinking quality purification of surface water from Pescia stream. Standard drinking water parameters, as well as specific microbiological parameters (Legionella, Mycobacterium, Adenovirus, coliphage) and DBP formation were monitored. Final results highlighted that the plant could reach a good removal of bacteria and a significant reduction of viruses. However, the adopted operation/maintenance policies had a strong impact on energy and water consumption, efficacy of bacterium/virus barrier and DBP formation. Hence, an accurate and competent operation, as well as the assistance of chemical disinfection, are still required for safe drinking water production.

Drinking & other pure water production: Filtration and sedimentation in clean water production

Pure water production, whether for human consumption or for industrial uses, is by far the largest application for solid-liquid separation equipment. Ken Sutherland looks at the role of filtration and sedimentation in the production of safe drinking water, and of pure water for other purposes.

Adsorptive removal of arsenic in saturated sand filter containing amended adsorbents

In this study, adsorptive removal of arsenic in saturated sand filters (SSF(a) and SSF(b)) containing raw and iron-coated honeycomb briquette cinders (HBC and Fe-HBC) is presented. Operating parameters including SSF design, dissolved oxygen (DO), pH, iron leaching and the effects of co-occurring ions on arsenic removal were investigated at 23±2.0°C temperature for 24-days long treatment. Sampling times (ST) (5–120min) during treatment days (TD) 1, 6, 12, 18 and 24 were purposively decided to assess filters’ performance from tap water with the spiked of 200μg/L of As(V) and As(III) into SSF(a) and SSF(b), respectively. No other alteration or pH adjustment was made to the influent water. Results demonstrated that the removal efficiencies of arsenic in SSF(a) and SSF(b) were maintained >95% and >85% till TD-12 and than decreased to 78% and 60%, respectively, on TD-24. Lower arsenic removal in SSF(b) could be the result of As(III) slower oxidation at the studied influent pH under oxic conditions. Decreased in effluent DO and increased iron leaching were measured in both the filters from TD-1 to TD-24. Minor variations of effluents pH and co-occurring ions (Fluoride, Nitrate and Sulphate) were recorded, but no significant effect on arsenic removal was measured in the reported ranges. Performance of NaOH-regenerated filter-beds was evaluated and both filters removed 95% of arsenic in three-cycle treatments. This study suggests of an in situ treatment; by the oxidation of As(III) into As(V) in the presence of DO and hydroxyl radical on adsorbent surfaces, followed by subsequent adsorption through selective physical sorption and Fe-As complexation. SSF containing cost-effective adsorbents could be an effective in situ treatment option to conventional treatment for safe drinking water production.

Extensive Environmental-Monitoring Project Relies on Integration of Several Networks

This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 156294, ’Innovative Environmental Monitoring for Upstream Onshore Installation,’ by Paolo Carnevale, SPE, and Silvia Di Croce, Eni, prepared for the 2012 SPE/APPEA International Conference on Health, Safety, and Environment in Oil and Gas Exploration and Production, Perth, Australia, 11-13 September. The paper has not been peer reviewed. A comprehensive environmental-monitoring project in the Agri Valley in southern Italy has been developed to ensure continuous management of the environmental effects of Eni’s oil treatment center there. This project is able to control the environmental effects of exploration and production in a large area around the plant (100 km2). It is characterized by a complete integration of several networks, stations, and systems used to monitor simultaneously air quality, noise, odorous emissions in terms of olfactory nuisance, groundwater and soil quality, ecosystems status, and ecological biodiversity. Introduction The area where the environmental-monitoring project was developed is characterized by sites that have community-level protection, especially areas protected because of national parks, widespread woods, rivers and streams of high quality, and springs and ground water of great regional and national importance for the production of safe drinking water. Eni’s oil treatment center in this territory collects the production from 24 oil wells, amounting to approximately 104,000 BOPD (Fig. 1). The environmental-monitoring plan consists of environmental-monitoring networks on more than 100 km2 at altitudes between 600 and 900 m. The system includes monitoring networks relevant to the following environmental variables: Air quality Biosystems Bad odors Noise Microseismicity Ecosystem Air Quality The network consists of four monitoring units placed 2.3–4.8 km from the oil center. The sites were chosen according to a model that predicted the spread of emissions from the oil center. The air-quality-monitoring stations were installed outside the plant to continuously identify the effects that production activities have on the quality of the air and to provide operational warnings to avoid any negative effect on the surrounding territory. Each unit is provided with computerized instruments, allowing continuous monitoring of the levels of carbon mon-oxide, hydrogen sulfide, sulfur dioxide, ozone, nitrogen oxides, benzene, toluene, xylene, methane, nonmethane gases, volatile organic compounds, polycyclic aromatic hydrocarbons, and radon, and monitoring of meteorological standards (e.g., wind speed and direction, rainfall levels, humidity, temperature). The data received continuously from the monitoring units are reported in real time on the Web and in the control room of the plant and are compared continuously with information on pollution standards taken from the chimneys of the oil center.

Efficiency of Silver Impregnated Porous Pot (SIPP) Filters for Production of Clean Potable Water

The Silver Impregnated Porous Pot (SIPP) filter is a product of the Tshwane University of Technology manufactured for the production of safe drinking water at a household (home) level. Two SIPP devices were assessed for the reduction efficiency of chemical contaminants such as calcium, magnesium, iron, arsenic, fluorides and total organic carbon (TOC) as well as microbial contaminants from environmental samples. Turbidity change after filtration, together with correlation between chlorophyll a in the feed water and SIPP’s flow rates were also evaluated in order to give comprehensive guidelines on the quality of intake water that could be filtered through the filter without causing a significant decrease in flow rate. The SIPP filters removed contaminants from environmental water samples as follows: 70% to 92% iron, 36% to 68% calcium, 42% to 82% arsenic, 39% to 98% magnesium, 39% to 95% fluorides, 12% to 35% TOC and 45% to 82% turbidity. The SIPP filters had initial flow rates of 1 L/h to 4 L/h but the flow rates dropped to 0.5 L/h with an increase in cumulative volume of intake water as the filter was used. Turbidity and chemical contaminant reduction rates decreased with accumulating volume of intake water but the filter removed Ca, Fe and Mg to levels that comply with the South African National Standards (SANS 241) and the World Health Organization (WHO) guideline values. However, the SIPP filters cannot produce enough water to satisfy the daily drinking water requirement of a typical household (25 L/p·d). Chlorophyll a was associated with a decrease in the flow rate through the SIPP filters.

Removing 17β-estradiol from drinking water in a biologically active carbon (BAC) reactor modified from a granular activated carbon (GAC) reactor

Estrogenic compounds in drinking water sources pose potential threats to human health. Treatment technologies are needed to effectively remove these compounds for the production of safe drinking water. In this study, GAC adsorption was first tested for its ability to remove a model estrogenic compound, 17β-estradiol (E2). Although GAC showed a relatively high adsorption capacity for E2 in isotherm experiments, it appeared to have a long mass transfer zone in a GAC column reactor, causing an early leakage of E2 in the effluent. With an influent E2 concentration of 20 μg/L, the GAC reactor was able to bring down effluent E2 to ∼200 ng/L. To further enhance E2 removal, the GAC reactor was converted to a biologically active carbon (BAC) reactor by promoting biofilm growth in the reactor. Under optimal operating conditions, the BAC reactor had an effluent E2 concentration of ∼50 ng/L. With the empty bed contact times tested, the reactor exhibited more robust E2 removal performance under the BAC operation than under the GAC operation. It is noted that estrone (E1), an E2 biodegradation intermediate, was frequently detected in reactor effluent during the BAC operation. Results from this study suggested that BAC could be an effective drinking water treatment process for E2 removal and in the meantime E1 accumulation needs to be addressed.

Cost-Effective Filter Materials Coated with Silver Nanoparticles for the Removal of Pathogenic Bacteria in Groundwater

The contamination of groundwater sources by pathogenic bacteria poses a public health concern to communities who depend totally on this water supply. In the present study, potentially low-cost filter materials coated with silver nanoparticles were developed for the disinfection of groundwater. Silver nanoparticles were deposited on zeolite, sand, fibreglass, anion and cation resin substrates in various concentrations (0.01 mM, 0.03 mM, 0.05 mM and 0.1 mM) of AgNO3. These substrates were characterised by SEM, EDS, TEM, particle size distribution and XRD analyses. In the first phase, the five substrates coated with various concentrations of AgNO3 were tested against E. coli spiked in synthetic water to determine the best loading concentration that could remove pathogenic bacteria completely from test water. The results revealed that all filters were able to decrease the concentration of E. coli from synthetic water, with a higher removal efficiency achieved at 0.1 mM (21–100%) and a lower efficiency at 0.01 mM (7–50%) concentrations. The cation resin-silver nanoparticle filter was found to remove this pathogenic bacterium at the highest rate, namely 100%. In the second phase, only the best performing concentration of 0.1 mM was considered and tested against presumptive E. coli, S. typhimurium, S. dysenteriae and V. cholerae from groundwater. The results revealed the highest bacteria removal efficiency by the Ag/cation resin filter with complete (100%) removal of all targeted bacteria and the lowest by the Ag/zeolite filter with an 8% to 67% removal rate. This study therefore suggests that the filter system with Ag/cation resin substrate can be used as a potential alternative cost-effective filter for the disinfection of groundwater and production of safe drinking water.

Increased information on waterborne outbreaks through efficient notification system enforces actions towards safe drinking water

In 1997, a compulsory notification system for waterborne outbreaks was introduced in Finland. The main aim of this notification is to obtain immediate information on suspected waterborne outbreaks in order to restrict and manage the outbreak promptly. During the past ten years, there have been 67 waterborne outbreaks in Finland, mainly associated with small groundwater supplies or private wells. The number of reported waterborne outbreaks has increased since the launch of the notification system indicating that the threshold limit of outbreak detection has most probably decreased. The number of cases of illness has fulfilled the national health target, which is below 0.01% of the population, but more action is still needed to ensure the production of safe drinking water under all circumstances. Ten years accumulation of knowledge on outbreaks has revealed that a compulsory notification system is an effective tool to gather information on waterborne outbreaks. The system has also increased awareness of possible problems related to the quality of drinking water. This article summarises management and legislative actions and policy measures taken so far in Finland to reduce the number of outbreaks and cases of illness related to them.

Household water treatment systems: A solution to the production of safe drinking water by the low-income communities of Southern Africa

One of the United Nations Millennium Development Goals is to reduce to half by 2015 the number of people, worldwide, who lack access to safe water. Due to the numerous deaths and illnesses caused by waterborne pathogens, various household water treatment devices and safe storage technologies have been developed to treat and manage water at the household level. The new approaches that are continually being examined need to be durable, lower in overall cost and more effective in the removal of the contaminants. In this study, an extensive literature survey was conducted to regroup various household treatment devices that are suitable for the inexpensive treatment of water on a household basis. The survey has resulted in the selection of four household treatment devices: the biosand filter (BSF), bucket filter (BF), ceramic candle filter (CCF) and the silver-impregnated porous pot filter (SIPP). The first three filters were manufactured in a Tshwane University of Technology workshop, using modified designs reported in literature. The SIPP filter is a product of the Tshwane University of Technology. The performance of the four filters was evaluated in terms of flow rate, physicochemical contaminant (turbidity, fluorides, phosphates, chlorophyll a, magnesium, calcium and nitrates) and microbial contaminant (Escherichia coli, Vibrio cholerae, Salmonella typhimurium, Shigella dysenteriae) removals. The flow rates obtained during the study period were within the recommended limits (171l/h, 167l/h, 6.4l/h and 3.5l/h for the BSF, BF, CCF and SIPP, respectively). Using standard methods, the results of the preliminary laboratory and field studies with spiked and environmental water samples indicated that all filters decreased the concentrations of contaminants in test water sources. The most efficiently removed chemical contaminant in spiked water was fluoride (99.9%) and the poorest removal efficiency was noted for magnesium (26–56%). A higher performance in chemical contaminant removal was noted with the BF. For pathogenic bacteria, the mean percentage removals ranged between 97% and 100%. Although the concentrations of most chemical parameters were within the recommended limits in raw surface water, poor removal efficiencies were recorded for all filters, with the poorest reduction noted with fluorides (16–48%). The average turbidity removals from surface water ranged between 90% and 95% for all filters. The highest bacterial removal efficiency was recorded by the SIPP (99–100%) and the lowest by the BF (20–45%) and the BSF (20–60%). Extensive experimental studies with various types of raw surface water will still determine the long-term performance of each filter, as well as the filters that can be recommended to the communities for household treatment of drinking water.

Stochastic Modelling of Drinking Water Treatment in Quantitative Microbial Risk Assessment

Safe drinking water is a basic need for all human beings. Preventing microbial contamination of drinking water is of primary concern since endemic illness and outbreaks of infectious diseases can have significant social and economic consequences. Confirming absence of indicators of faecal contamination by water analysis only provides a limited verification of safety. By measuring pathogenic organisms in source water and modelling their reduction by treatment, a higher level of drinking water safety can be verified. This book provides stochastic methods to determine reduction of pathogenic microorganisms by drinking water treatment. These can be used to assess the level and variability of drinking water safety while taking uncertainty into account. The results can support decisions by risk managers about treatment design, operation, monitoring, and adaptation. Examples illustrate how the methods can be used in water safety plans to improve and secure production of safe drinking water. This title belongs to KWR Watercycle Research Institute Series . ISBN: 9781843393740 (Print) ISBN: 9781780401591 (eBook)

Metallic iron for safe drinking water worldwide

A new concept for household and large-scale safe drinking water production is presented. Raw water is successively filtered through a series of sand and iron filters. Sand filters mostly remove suspended particles (media filtration) and iron filters remove anions, cations, micro-pollutants, natural organic matter, and micro-organisms including pathogens (reactive filtration). Accordingly, treatment steps conventionally achieved with flocculation, sedimentation, rapid sand filtration, activated carbon filtration, and disinfection are achieved in the new concept in only two steps. To prevent bed clogging, Fe 0 is mixed with inert materials, yielding Fe 0/sand filters. Efficient water treatment in Fe 0/sand filters has been extensively investigated during the past two decades. Two different contexts are particularly important in this regard: (i) underground permeable reactive barriers and (ii) household water filters. In these studies, the process of aqueous iron corrosion in a packed bed was proven very efficient for unspecific aqueous contaminant removal. Been based on a chemical process (iron corrosion), efficient water treatment in Fe 0 beds is necessarily coupled with a slow flow rate. Therefore, for large communities several filters should work in parallel to produce enough water for storage and distribution. It appears that water filtration through Fe 0/sand filters is an efficient, affordable, a flexible technology for the whole world.

Extending Service Life of Household Water Filters by Mixing Metallic Iron with Sand

AbstractThe use of metallic iron filters (Fe0 filters) has been discussed as a promising low‐cost option for safe drinking water production at household level. Filter clogging due to the volumetric expansive nature of iron corrosion has been identified as the major problem of Fe0 filters. Mixing Fe0 and sand (yielding Fe0/sand filters) has been proposed as a tool to extent filter service life. However, no systematic discussion rationalizing Fe0/sand mixtures is yet available. This communication theoretically discussed suitable Fe0/sand proportions for efficient filters. Results suggested that Fe0/sand filters should not contain more that 50 vol% Fe0 (25 wt% when Fe0 is mixed with quartz). The actual Fe0 percentage in a filter will depend on its intrinsic reactivity.

Development of a mobile water maker, a sustainable way to produce safe drinking water in developing countries

Moreover, there is a growing demand for a simple, low capacity drinking water treatment used by local people in developing countries to reduce mortality caused by water born diseases. To solve this problem a small portable water treatment unit with a production capacity of approximately 500 L/day was developed. The unit can operate without the use of external electricity/pumps/generators in order to operate completely independent. The mobile water treatment unit uses tubular ceramic membranes in combination with an anodic oxidation process, powered by a solar power panel. The membranes are cleaned by simple flushing without the use of chemicals and this enables a sustainable production of safe drinking water on every location in the world without replacing polluted filter cartridges. Laboratory tests with several kinds of surface water and effluent of a wastewater treatment plant (WWTP) showed a very stable production and gave very good results in the removal of sediments, colloidal material, bacteria and viruses.

The impact of climate change on drinking water supply by riverbank filtration

Riverbank filtration (RBF) is a well proven natural treatment, which in many countries is part of a multi-barrier concept in drinking water supply. The induced infiltration of river water into the aquifer produces a significant improvement in river water quality. Riverbank filtration wells are characterized by a high capacity. Based on data from recent years, an integrated approach to assessing the impact of climate change on safe drinking water production by RBF is demonstrated in the Lower Rhine Valley, Germany. Influencing factors on quantitative as well as qualitative aspects were identified. During low river water periods, the capacity of the RBF-wells decreases. In addition the lower discharge within the river is accompanied by a increased concentration of several chemical compounds. Together with higher water temperatures which influence the hydrogeochemical processes during RBF, the changing raw water composition has to be considered for the subsequent technical treatment step. However, our investigations reveal that despite the impact of climate change on RBF, the multi-protective barrier concept, including both natural and technical purification, has proven a reliable method for drinking water production. The sanitation of the Rhine over the last decades was an important step to make RBF more resilient to climate change.