Microplastics (MPs) have recently been detected in oceans, seas and freshwater bodies worldwide, yet few studies have revealed the occurrence of MPs in potable water. Although the potential ...toxicological effects of MPs are still largely unknown, their presence in water intended for human consumption deserves attention. Drinking water treatment plants (DWTPs) pose a barrier for MPs to enter drinking water; thus, the fate of MPs at DWTPs is of great interest. This review includes a summary of the available information on MPs in drinking water sources and in potable water, discusses the current knowledge on MP removal by different water treatment processes, and identifies the research needs regarding MP removal by DWTP technologies. A comparison of MPs with other common pollution agents is also provided. We concluded that special attention should be given to small-size MPs (in the range of several micrometres) and that the relationship between MP character and behaviour during distinct treatment processes should be explored.
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•Microplastics (MPs) are being detected in freshwaters and also in drinking water.•Drinking water treatment plants pose a barrier for MPs to enter drinking water.•Conventional treatment processes have a potential to remove a part of microplastics.•Efficiency of distinct treatment steps versus MPs character should be understood.•Regarding water treatment, special focus should be put on small-sized MPs (< 10 μm).
Fluoride contamination of groundwater is a serious problem in several countries of the world because of the intake of excessive fluoride caused by the drinking of the contaminated groundwater. ...Geological and anthropogenic factors are responsible for the contamination of groundwater with fluoride. Excess amounts of fluoride in potable water may cause irreversible demineralisation of bone and tooth tissues, a condition called fluorosis, and long-term damage to the brain, liver, thyroid, and kidney. There has long been a need for fluoride removal from potable water to make it safe for human use. From among several defluoridation technologies, adsorption is the technology most commonly used due to its cost-effectiveness, ease of operation, and simple physical process. In this paper, the adsorption capacities and fluoride removal efficiencies of different types of adsorbents are compiled from relevant published data available in the literature and represented graphically. The most promising adsorbents tested so far from each category of adsorbents are also highlighted. There is still a need to discover the actual feasibility of usage of adsorbents in the field on a commercial scale and to define the reusability of adsorbents to reduce cost and the waste produced from the adsorption process. The present paper reviews the currently available methods and emerging approaches for defluoridation of water.
•Adsorption capacities and fluoride removal efficiencies have been presented for a wide range of adsorbents.•Aluminium-based adsorbents are most effective but it’s leaching cause health problems.•Langmuir isotherm and pseudo-second-order kinetic were found to be best fitting model.•Current desorption strategies are inadequate and environmentally not sustainable.•Reusability of an adsorbent is very important to make it sustainable.•More integrated and economically viable adsorption techniques now needed.
Climate change, severe droughts, population growth, demand increase, and poor management during the recent decades have further stressed the scarce freshwater resources worldwide and resulted in ...severe water shortages in many regions. The water utilities address the water shortage by providing alternative source of water, augment the supplied water, supply intermittently, and even bulk water delivery under severe water shortage conditions. On the other hand, many households store water in building storage tanks to cope with insufficient delivery of potable water due to frequent interruptions. All these practices could pose crucial risks to the chemical and microbiological quality of the water. However, consistent monitoring and implementation of mitigation strategies could lower the potential risks associated with these practices. It is critical to identify the potential hazards resulting from the alternative water supplies and distribution practices to develop temporary and long-term monitoring and mitigation plans and reduce the microbial and chemical contamination of potable water delivered to the consumers. This paper provides a holistic review of the significant hazards associated with the practices employed by the water utilities and water consumers to alleviate the potable water shortage and discusses the required monitoring and mitigation practices.
Characterising the organic and microbial matrix of water are key issues in ensuring a safe potable water supply. Current techniques only confirm water quality retrospectively via laboratory analysis ...of discrete samples. Whilst such analysis is required for regulatory purposes, it would be highly beneficial to monitor water quality in-situ in real time, enabling rapid water quality assessment and facilitating proactive management of water supply systems.
A novel LED-based instrument, detecting fluorescence peaks C and T (surrogates for organic and microbial matter, respectively), was constructed and performance assessed. Results from over 200 samples taken from source waters through to customer tap from three UK water companies are presented. Excellent correlation was observed between the new device and a research grade spectrophotometer (r2=0.98 and 0.77 for peak C and peak T respectively), demonstrating the potential of providing a low cost, portable alternative fluorimeter. The peak C/TOC correlation was very good (r2=0.75) at low TOC levels found in drinking water. However, correlations between peak T and regulatory measures of microbial matter (2day/3day heterotrophic plate counts (HPC), E. coli, and total coliforms) were poor, due to the specific nature of these regulatory measures and the general measure of peak T. A more promising correlation was obtained between peak T and total bacteria using flow cytometry. Assessment of the fluorescence of four individual bacteria isolated from drinking water was also considered and excellent correlations found with peak T (Sphingobium sp. (r2=0.83); Methylobacterium sp. (r2=1.0); Rhodococcus sp. (r2=0.86); Xenophilus sp. (r2=0.96)). It is notable that each of the bacteria studied exhibited different levels of fluorescence as a function of their number. The scope for LED based instrumentation for in-situ, real time assessment of the organic and microbial matrix of potable water is clearly demonstrated.
•LED fluorimeter developed for accurate assessment of potable water quality•Device offers potential to promote a proactive means of monitoring water quality.•4 bacteria isolated from water show a clear and different response between strains.
A humidification–dehumidification desalination system powered by low-grade waste heat energy (45 °C–70 °C) was experimentally investigated. The seawater directly utilized as coolant (25 °C) for the ...dehumidifier was preheated by latent heat recovery from the water vapor produced by the humidifier. The effect of key performance-contributing factors such as the mass flow rate and temperature of the air and feed at the inlets of the humidifier and dehumidifier were evaluated and optimized. For a constant volume, the effect of the humidifier's surface area was evaluated comparatively considering different novel packing materials such as tri-pack rings, pall rings (diameter = 16 mm and 25 mm), saddle rings, and snowflake rings. It was determined that compared to other factors, air-related and water-related parameters influenced the humidifier and dehumidifier performance respectively. Maximum freshwater productivity of 1398 mL/h was achieved with 16 mm pall ring humidifier, owing to its improved wet area (188,000 m2/m3) under optimal conditions of air flow rate, feed flow rate, humidifier air inlet temperature, humidifier, and dehumidifier water inlet temperatures of 3.5 kg/min, 0.9 L/min, 70 °C, 55 °C, and 25 °C, respectively, with a dual-fluid preheating mechanism. Detailed chemical analysis revealed that the generated freshwater is potable.
•Low-grade waste heat is utilized to convert seawater into freshwater through HDH.•The system is optimized for process conditions in conjunction with different packed humidifiers.•Seawater is directly used as a coolant (25 °C) without precooling.•The humidifier's surface area had a direct influence on freshwater productivity.•The generated freshwater satisfies WHO and EPA drinking water standards.
•Field studies comparing disinfectants rank the typical efficacy against Legionella as chloramine > chlorine dioxide > chlorine.•Disinfection concentration on its own is not the deciding factor for ...the disinfectant efficacy against Legionella.•A total of 16 different factors potentially influenced the antibacterial efficacy of the chlorine-based disinfectants.•A total of 21 factors were identified as influencing the rate of decay of disinfectants in premise plumbing systems.•Future research is needed to measure and model these factors in premise plumbing systems to improve Legionella control.
Legionella is an opportunistic waterborne pathogen that causes Legionnaires’ disease. It poses a significant public health risk, especially to vulnerable populations in health care facilities. It is ubiquitous in manufactured water systems and is transmitted via inhalation or aspiration of aerosols/water droplets generated from water fixtures (e.g., showers and hand basins). As such, the effective management of premise plumbing systems (building water systems) in health care facilities is essential for reducing the risk of Legionnaires’ disease. Chemical disinfection is a commonly used control method and chlorine-based disinfectants, including chlorine, chloramine, and chlorine dioxide, have been used for over a century. However, the effectiveness of these disinfectants in premise plumbing systems is affected by various interconnected factors that can make it challenging to maintain effective disinfection. This systematic literature review identifies all studies that have examined the factors impacting the efficacy and decay of chlorine-based disinfectant within premise plumbing systems. A total of 117 field and laboratory-based studies were identified and included in this review. A total of 20 studies directly compared the effectiveness of the different chlorine-based disinfectants. The findings from these studies ranked the typical effectiveness as follows: chloramine > chlorine dioxide > chlorine. A total of 26 factors were identified across 117 studies as influencing the efficacy and decay of disinfectants in premise plumbing systems. These factors were sorted into categories of operational factors that are changed by the operation of water devices and fixtures (such as stagnation, temperature, water velocity), evolving factors which are changed in-directly (such as disinfectant concentration, Legionella disinfectant resistance, Legionella growth, season, biofilm and microbe, protozoa, nitrification, total organic carbon(TOC), pH, dissolved oxygen(DO), hardness, ammonia, and sediment and pipe deposit) and stable factors that are not often changed(such as disinfectant type, pipe material, pipe size, pipe age, water recirculating, softener, corrosion inhibitor, automatic sensor tap, building floor, and construction activity). A factor-effect map of each of these factors and whether they have a positive or negative association with disinfection efficacy against Legionella in premise plumbing systems is presented. It was also found that evaluating the effectiveness of chlorine disinfection as a water risk management strategy is further complicated by varying disinfection resistance of Legionella species and the form of Legionella (culturable/viable but non culturable, free living/biofilm associated, intracellular replication within amoeba hosts). Future research is needed that utilises sensors and other approaches to measure these key factors (such as pH, temperature, stagnation, water age and disinfection residual) in real time throughout premise plumbing systems. This information will support the development of improved models to predict disinfection within premise plumbing systems. The findings from this study will inform the use of chlorine-based disinfection within premise plumbing systems to reduce the risk of Legionnaires disease.
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Although granular activated carbon (GAC) has been broadly applied in ozone-biologically activated carbon filtration (O3/BAC) systems for potable reuse of municipal wastewater, the mechanisms of ...various pollutant removal remain largely unknown as the regenerated GAC develops microbial populations resulting in biofiltration but loses significant adsorption capacity as it becomes spent GAC. Therefore, pilot-scale parallel performance comparisons of spent and regenerated GAC, along with a range of pre-oxidant ozone doses, were used to shed light on the mechanisms responsible for the removal of various types of treatment byproduct precursors and trace organic compounds. It was confirmed from this pilot-study that ozone alone can effectively degrade chlorinated trihalomethane (THM) and haloacetic acid (HAA) precursors, chloramine-reactive N-nitrosodimethylamine (NDMA) precursors, and 29 PPCPs. In contrast, biodegradation by microbial population on spent or regenerated GAC can remove NDMA and 22 PPCPs, while the adsorption by regenerated GAC can remove chlorinated THM and HAA precursors, PFAS, flame retardants, and 27 PPCPs. The results of this pilot study are intended to provide those interested in potable reuse with an example of the simultaneous removal capabilities and mechanisms that can be anticipated for treating a complex mixture of organics present in real municipal wastewater effluent.
•Roles of spent and regenerated GAC were for the first time compared.•Pathways for the removal of a wide spectrum of compounds were identified.•Biodegradation can remove NDMA and 22 PPCPs.•Adsorption can remove THM and HAA precursors, PFAS, flame retardants, and 27 PPCPs.•Ozone can remove THM, HAA, chloramine-reactive NDMA precursors, and 29 PPCPs.
The increasing demand for drinking water has led to the adoption of unconventional water sources, such as water reuse. Reverse osmosis (RO) and nanofiltration (NF) membranes are effective barriers ...against trace organic contaminants in potable water reuse applications. However, the use of RO is being challenged by NF, primarily due to NF's potential to achieve similar contaminant removal as RO but with higher productivity and lower energy requirements. This study compares NF and RO membranes in terms of contaminant removal and energy consumption for potable water reuse applications. RO (BW30XFR) and dense and loose NF (NF90 and NF270) membranes were tested in bench-scale systems, and RO (TW30) and NF (NF9) membrane elements were tested in an engineering scale system utilizing UF-filtered reclaimed wastewater. The highest solute passage was observed using NF270 membrane. There was no difference between NF90 and BW30XFR in terms of divalent ion passage, but NF90's total organic carbon and monovalent ion passages were higher. Both NF90 and BW30XFR highly rejected negatively charged trace organic contaminants (TOrCs), though rejections were lower for neutral and positively charged compounds. Furthermore, all compounds were highly rejected in the engineering-scale system by NF9 and TW30. These results highlight the potential of dense NF membranes as an energy-efficient barrier for contaminant removal.
•Bench- and engineering-scale systems were used to compare NF and RO membranes.•High TOC rejection by NF90 and NF270, but lower rejection of inorganics with NF270•Rejection of inorganics was similar between NF90 and RO except for monovalent ions.•Rejection of TOrCs was similar between NF90 and RO membranes.•NF9 maintained high contaminants rejection in long-term engineering-scale operations.
In the face of water shortages, the world seeks to explore all available options in reducing the over exploitation of limited freshwater resources. One of the surest available water resources is ...wastewater. As the population grows, industrial, agricultural, and domestic activities increase accordingly in order to cater for the voluminous needs of man. These activities produce large volumes of wastewater from which water can be reclaimed to serve many purposes. Over the years, conventional wastewater treatment processes have succeeded to some extent in treating effluents for discharge purposes. However, improvements in wastewater treatment processes are necessary in order to make treated wastewater re-usable for industrial, agricultural, and domestic purposes. Membrane technology has emerged as a favorite choice for reclaiming water from different wastewater streams for re-use. This review looks at the trending membrane technologies in wastewater treatment, their advantages and disadvantages. It also discusses membrane fouling, membrane cleaning, and membrane modules. Finally, recommendations for future research pertaining to the application of membrane technology in wastewater treatment are made.
Microplastic pollution of water and ecosystem is attracting continued attention worldwide. Due to their small sizes (≤5 mm) microplastic particles can be discharged to the environment from treated ...wastewater effluents. As microplastics have polluted most of our aquatic ecosystems, often finding its way into drinking water, there is urgent need to find new solutions for tackling the menace of microplastic pollution. In this work, sustainable green photocatalytic removal of microplastics from water activated by visible light is proposed as a tool for the removal of microplastics from water. We propose a novel strategy for the elimination of microplastics using glass fiber substrates to trap low density microplastic particles such as polypropylene (PP) which in parallel support the photocatalyst material. Photocatalytic degradation of PP microplastics spherical particles suspended in water by visible light irradiation of zinc oxide nanorods (ZnO NRs) immobilized onto glass fibers substrates in a flow through system is demonstrated. Upon irradiation of PP microplastics for two weeks under visible light reduced led to a reduction of the average particle volume by 65%. The major photodegradation by-products were identified using GC/MS and found to be molecules that are considered to be mostly nontoxic in the literature.
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•Photocatalytic removal of microplastics from water activated by visible light (simulated sunlight).•Photodegradation of microplastics particles in a continuous water flow system.•More than 65% reduction in microplastics particle volume within two weeks of visible light irradiation.•The by-products from microplastics degradation are considered to have low toxicity effect on human and aquatic environment.•Fast kinetic evolution of carbonyl and hydroxyl groups are observed.
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