Removal Of Chemical Contaminants Research Articles

Removal of metals and assimilable organic carbon by activated carbon and reverse osmosis point-of-use water filtration systems

Activated carbon (AC) systems and reverse osmosis (RO) systems are commonly used point-of-use (POU) water filtration systems for removing trace-level contaminants in tap water to protect human health. However, limited research has been done to evaluate their effectiveness in removing heavy metals like manganese (Mn) and uranium (U), or to assess the potential for undesired microbial growth within POU systems, which can reduce their treatment efficiency. This study aimed to systematically evaluate the removal of metals and assimilable organic carbon (AOC) in POU systems. AC systems were operated to 200% of their designed treatment capacities and RO systems were run for three weeks. The results showed that AC systems were generally ineffective at removing metals from drinking water, while RO systems effectively removed them. Both Mn and U were poorly removed by AC systems. Calcium (Ca) and magnesium (Mg) were poorly removed by AC systems, with efficiencies of less than 1%. Iron (Fe) removal by AC systems varied between 61% and 84%. Copper (Fe), likely due to its low influent concentration (<30 μg L−1), was effectively removed by AC systems with efficiencies over 95%. In contrast, RO systems consistently removed all metals effectively. Mn and U removal in RO systems exceeded 95%, while Ca, Mn, Fe, and Cu were all removed with efficiencies greater than 98%. AOC was effectively removed from all AC and RO systems, but with high variability in removal efficiency, which is likely attributed to the heterogeneity of biofilm and microbial growth within the POU systems. The new knowledge generated from this study can improve our understanding of chemical contaminant removal in POU systems and inform the development of better strategies for designing and operating POU systems to remove chemical contaminants in drinking water and mitigate their associated health risks.

Hierarchically Porous Polyacetylene Networks: Adsorptive Photocatalysts for Efficient Bisphenol A Removal from Water.

In this article, we report a series of functionalized polyacetylene-type networks formed by chain-growth insertion coordination polymerization in high internal phase emulsions (HIPEs). All polymerized HIPEs (polyHIPEs) contain a hierarchically structured, 3D-interconnected porous framework consisting of a micro-, meso- and macropore system, resulting in exceptionally high specific surface areas (up to 1055 m2·g-1) and total porosities of over 95%. The combination of π-conjugated and hierarchically porous structure in one material enabled the use of these polyacetylene polyHIPEs as adsorptive photocatalysts for the removal of chemical contaminants from water. All polyacetylene polyHIPEs demonstrated high efficiency in the adsorption of bisphenol A from water (up to 48%) and the subsequent photocatalytic degradation. Surprisingly, high adsorption capacity did not affect the photocatalytic efficiency (up to 58%). On the contrary, this dual function seems to be very promising, as some polyacetylene polyHIPEs almost completely removed bisphenol A from water (97%) through the adsorption-photooxidation mechanism. It also appears that the presence of polar functional side groups in the polyacetylene backbone improves the contact of the polyacetylene network with the aqueous bisphenol A solution, which can thus be more easily adsorbed and subsequently oxidized, compensating for the lower specific surface area of some networks, namely, 471 and 308 m2·g-1 in the case of 3-ethynylphenol- and 3-ethynylaniline-based polyacetylene polyHIPEs, respectively.

Low-Cost Antibacterial Ceramic Water Filters for Decentralized Water Treatment: Advances and Practical Applications.

Access to clean water remains challenging for people living in underdeveloped regions, rural areas, and remote locations. In the absence of centralized water treatment systems, point-of-use (POU) solutions are necessary. Ceramic water filters (CWFs) have emerged as a practical and affordable option for decentralized water treatment. This review focuses on recent advances in antibacterial CWFs, including preparation methods, filtration performance, and applications. The review highlights the significance of preparation techniques, material choices, and additives in determining CWF properties and performance. Despite virus and chemical contaminant removal limitations, ongoing research on nanofillers and antibacterial additives shows promise for enhancing the CWF performance. The cost-effectiveness, ease of production, and low operational requirements of CWF make it a viable solution for decentralized drinking water systems, particularly in resource-limited areas. Studies have demonstrated the efficacy of CWFs in reducing water contaminants, but proper maintenance and user training are crucial to optimal performance.

An Overview on Chemical Contaminants of Wastewater and Their Current Removal Techniques

Water pollution is a global concern, and it has affected the lives of millions of people. The delivery of a good approach to eliminate the chemical contaminants is an emerging issue and requires continuous exploration. Recently, extensive studies have reported interesting findings on the development of suitable methods for the removal of chemical contaminants. In this review, the origin of different types of chemical contaminants and their effect on the environment and human health were presented. We also reviewed the current state-of-the-art of available and newly established techniques for the removal of the chemical contaminants. Lastly, challenges and future directions related to this area were also tackled. This review can be positively beneficial to human, the environment, economics and society.

Performance evaluation of ceramic pot filters combined with adsorption processes for the removal of heavy metals and phenolic compounds.

It has been demonstrated that the ceramic pot filters (CPFs) with impregnated colloidal silver are efficient for the removal of turbidity and pathogens for household water treatment. This investigation evaluated the efficiency of two filter models for the removal of chemical contaminants (Hg, Pb, As and phenolic compounds) during 175 days. The first model is a traditional CPF impregnated with colloidal silver and the second consists of the ceramic silver-impregnated pot plus a post-filtration column with granular activated carbon and zeolite (CPF + GAC-Z). The results of the CPF showed average efficiencies of 91.5% (Hg), 92% (Pb), 50.2% (As) and 78.7% (phenols). The CPF + GAC-Z showed similar efficiencies for the removal of heavy metals (92.5% Hg, 98.1% Pb and 52.3% As) and a considerably higher efficiency for the removal of phenols (96.4%). The As concentration of the filtered water in both systems was higher than the regulatory limit. The ceramic pot was responsible for the highest removal of chemical compounds. It can be concluded that the traditional CPF is a viable option for water supply treatment at the household level for the removal of chemical contaminants. The efficiency of this filter can be improved with the post-filtration column mainly for the removal of organic constituents.

Group Contribution Method to Predict the Mass Transfer Coefficients of Organics through Various RO Membranes.

Reverse osmosis (RO) is a membrane technology that separates dissolved species from water. RO has been applied for the removal of chemical contaminants from water for potable reuse applications. The presence of a wide variety of influent chemical contaminants and the insufficient rejection of low-molecular-weight neutral organics by RO calls for the need to develop a model that predicts the rejection of various organics. In this study, we develop a group contribution method (GCM) to predict the mass transfer coefficients by fragmenting the structure of low-molecular-weight neutral organics into small parts that interact with the RO membrane. Overall, 54 organics including 26 halogenated and oxygenated alkanes, 8 alkenes, and 20 alkyl and halobenzenes were used to determine 39 parameters to calibrate for 6 different RO membranes, including 4 brackish water and 2 seawater membranes. Through six membranes, approximately 80% of calculated rejection was within an error goal (i.e., ±5%) from the experimental observation. To extend the GCM for a reference RO membrane, ESPA2-LD, 14 additional organics were included from the literature to calibrate nitrogen-containing functional groups of nitrosamine, nitriles, and amide compounds. Overall, 49 organics (72% of 68 compounds) from calibration and 7 compounds (87.5% of 8 compounds) from prediction were within the error goal.

Temperature dependence of hydroxyl radical reactions with chloramine species in aqueous solution

The absolute temperature-dependent kinetics for the reaction between hydroxyl radicals and the chloramine water disinfectant species monochloramine (NH2Cl), as well as dichloramine (NHCl2) and trichloramine (NCl3), have been determined using electron pulse radiolysis and transient absorption spectroscopy. These radical reaction rate constants were fast, with values of 6.06 × 108, 2.57 × 108, and 1.67 × 108 M−1 s−1 at 25 °C for NH2Cl, NHCl2, and NCl3, respectively. The corresponding temperature dependence of these reaction rate constants, measured over the range 10–40 °C, is well-described by the transformed Arrhenius equations:ln k (OH & NH2Cl) = (23.68 ± 0.23) – {(8570 ± 580)/(8.314*T/K)}ln k (OH & NHCl2) = (21.96 ± 0.56) – {(6110 ± 400)/(8.314*T/K)}ln k (OH & NCl3) = (21.26 ± 0.29) – {(5770 ± 720)/(8.314*T/K)}giving activation energies of 8.57 ± 0.58, 6.11 ± 0.40, and 5.77 ± 0.72 kJ mol−1 for these three chloramines, respectively. These data will aid water utilities in predicting hydroxyl radical partitioning and chemical contaminant removal efficiencies under real-world advanced oxidation process treatment conditions.

From source to filter: changes in bacterial community composition during potable water treatment.

Rural communities rely on surface water reservoirs for potable water. Effective removal of chemical contaminants and bacterial pathogens from these reservoirs requires an understanding of the bacterial community diversity that is present. In this study, we carried out a 16S rRNA-based profiling approach to describe the bacterial consortia in the raw surface water entering the water treatment plants of 2 rural communities. Our results show that source water is dominated by the Proteobacteria, Bacteroidetes, and Cyanobacteria, with some evidence of seasonal effects altering the predominant groups at each location. A subsequent community analysis of transects of a biological carbon filter in the water treatment plant revealed a significant increase in the proportion of Proteobacteria, Acidobacteria, Planctomycetes, and Nitrospirae relative to raw water. Also, very few enteric coliforms were identified in either the source water or within the filter, although Mycobacterium was of high abundance and was found throughout the filter along with Aeromonas, Legionella, and Pseudomonas. This study provides valuable insight into bacterial community composition within drinking water treatment facilities, and the importance of implementing appropriate disinfection practices to ensure safe potable water for rural communities.

Potential Effectiveness of Point-of-Use Filtration to Address Risks to Drinking Water in the United States.

Numerous contemporary incidents demonstrate that conventional control strategies for municipal tap water have limited ability to mitigate exposures to chemicals whose sources are within distribution systems, such as lead, and chemicals that are not removed by standard treatment technologies, such as perfluorooctanoic acid (PFOA)/perfluorooctanesulfonic acid (PFOS). In these situations, point-of-use (POU) controls may be effective in mitigating exposures and managing health risks of chemicals in drinking water, but their potential utility has not been extensively examined. As an initial effort to fill this information gap, we conducted a critical review and analysis of the existing literature and data on the effectiveness of POU drinking water treatment technologies for reducing chemical contaminants commonly found in tap water in the United States. We found that many types of water treatment devices available to consumers in the United States have undergone laboratory testing and often certification for removal of chemical contaminants in tap water, but in most cases their efficacy in actual use has yet to be well characterized. In addition, the few studies of POU devices while “in use” focus on traditional contaminants regulated under the Safe Drinking Water Act, but do not generally consider nontraditional contaminants of concern, such as certain novel human carcinogens, industrial chemicals, pesticides, pharmaceuticals, personal care products, and flame retardants. Nevertheless, the limited information available at present suggests that POU devices can be highly effective when used prophylactically and when deployed in response to contamination incidents. Based on these findings, we identify future areas of research for assessing the ability of POU filters to reduce health-related chemical contaminants distributed through public water systems and private wells.

A New Approach and Tools for Perfecting Phytoremediation Technology

The development of methods for soil remediation for removal of chemical contaminants is a large and challenging problem. A new phytoremediation technology, given in the present work, is based on joint application of natural sorbents, microorganisms and plants. The method aims at prevention of chemical contamination of soils. It has the potential to restore a polluted environment and prevent dissemination of toxic compounds from hotbeds of pollution for a considerable length of time. The presented complex biotechnology is important from the viewpoint of prevention. This technology can be applied to soils contaminated with heavy metals, oil hydrocarbons, explosives, pesticides and other pollutants. The main purpose of the carried out work is the development of a novel approach to the provision of ecological safety. The approach is based on using natural minerals composites which are comprised of natural mineral rocks, microorganism strains with high detoxification abilities and plants-phytoremediators. In this composite material, the function of a sorbent is to uptake and to trap pollutants thus restraining their emission in the environment. The role of the microorganisms is to accomplish the first stage of biodegradation of organic contaminants and then to apply phytoremediation as a unique cleanup strategy. Natural sorbent can be applied during the initial stage of cleaning up of contaminated soil, followed by application of a phytoremediation technology through purposeful planting of selected plants. This results in the total assimilation and complete mineralization of pollutants and/or their intermediates or in their partial transformation by microbes.Following contaminants were used in the present work: explosive – 2,4,6 trinitrotoluene (TNT), oil hydrocarbon (hexadecane) and Wax (long chain hydrocarbons). Special attention was paid to enhancement of soil fertility, which improves microorganism and plant growth conditions and is important for bioremediation processes providing total rehabilitation of soil.

Justification for community-scale photovoltaic-powered electrodialysis desalination systems for inland rural villages in India

This paper justifies photovoltaic (PV)-powered electrodialysis (ED) as an energy and cost-effective means of desalinating groundwater in rural India and presents the design requirements for a village-level system. Saline groundwater, which underlies 60% of India, can negatively impact health as well as cause a water source to be discarded because of its taste. A quarter of India's population live in villages of 2000–5000 people, many of which do not have reliable access to electricity. Most village-scale, on-grid desalination plants use reverse osmosis (RO), which is economically unviable in off-grid locations. Technical and ethnographic factors are used to develop an argument for PV-ED for rural locations, including: system capacity, biological and chemical contaminant removal; water aesthetics; recovery ratio; energy source; economics of water provision; maintenance; and the energetic and cost considerations of available technologies. Within the salinity range of groundwater in India, ED requires less specific energy than RO (75% less at 1000mg/L and 30% less at 3000mg/L). At 2000mg/L, this energetic scaling translates to a 50% lower PV power system cost for ED versus RO. PV-ED has the potential to greatly expand the reach of desalination units for rural India.

Removal of Chemical Contaminants of Micro-Polluted Water from Wastewater Treatment Plant Through Electrochemical Oxidation

Removal of Chemical Contaminants of Micro-Polluted Water from Wastewater Treatment Plant Through Electrochemical Oxidation

A comparative assessment of chemical contaminant removal by three household water treatment filters

This study was aimed at modifying the design of, constructing, evaluating and comparing chemical contaminant removal efficiency by, 3 household water treatment filters. The filters were: 1) biosand filter (BSF); 2) the ceramic candle filter (CCF); 3) bucket filter (BF). The filters were evaluated for their efficiency in removal of calcium, magnesium, iron and arsenic, nitrates, phosphates, fluorides, total organic carbon and turbidity, by determining levels of these contaminants in water before and after filtration through the filters. The effects of chlorophyll a concentration(mg/m3) of intake water, as well as the effects of turbidity of intake water, on the flow rates of the filters was quantified and recommendations on the quality of water that could be filtered through these filters were made. Chlorophyll a concentrations in intake water had a positive correlation with the turbidity of the unfiltered water (r = 0.607).The flow rates of the filters were 0.8 l/h - 6.48 l/h (BSF), 0.05 l/h - 2.495 l/h (CCF) and 106.5 l/h - 160.5 l/h (BF). Because of the large particle size materials used in constructing the BF and the design, which caused it to be a rapid sand filter, the biosand filter (BF) was found to have flow rates significantly higher than those of BSF and CCF (p ≥ 0.05). There was no difference in the efficiency of removal of metals (average 40% - 50%) by the filters (p ≥ 0.05), as the same removal mechanisms (straining, ammonification, fixation and adsorption) were believed to be taking place in all of the filters. The CCF removed total organic carbon (TOC) (up to 39%) better than the BSF and BF (p ≤ 0.05). The filters removed turbidity effectively with the BSF having the highest reduction (70%). The average turbidity reduction efficiency was in the order BSF (70%) > BF (51%) > CCF (44%). The BSF, CCF and BF reduced turbidity and other contaminants even after filtering a total cumulative volume greater than 1 000 l. Keywords : Biosand filter, bucket filter, ceramic candle filter, flow rate, chlorophyll a .

A simplified cost-effective biosand filter (BSFZ) for removal of chemical contaminants from water

A study aimed at designing, constructing and evaluating a cost-effective biosand filter was undertaken. The biosand filter was modified with the addition of zeolites (clinoptilolite). The zeolites formed the largest part of the filter media which comprised of four layers. The complete filter had six zones which played a role during the filtration process. Filtration was done for 3 h to mimic water filtration in private homes. The filtered water was collected in a vessel for 1 h after which the samples were taken for analysis. Results indicated removal of up to 80 calcium, 89 magnesium, 99 iron, 56 arsenic, 54 fluorides, 96 turbidity, 37 nitrates and 41% total organic carbon. Higher turbidity (r = 0.024) and chlorophyll a (r = 0.566) concentrations resulted in a decrease in the flow rate of the filter which was between 1.74 l/h and 19.20 l/h. Higher chlorophyll a concentrations resulted in higher turbidity (r = 0.609). The filter was costeffective (<US$20.00), and easy to construct, operate and maintain.

A simplified cost-effective biosand filter (BSFZ) for removal of chemical contaminants from water

A simplified cost-effective biosand filter (BSFZ) for removal of chemical contaminants from water

Assessing granular media filtration for the removal of chemical contaminants from wastewater

Granular media filtration was evaluated for the removal of a suite of chemical contaminants that can be found in wastewater. Laboratory- and pilot-scale sand and granular activated carbon (GAC) filters were trialled for their ability to remove atrazine, estrone (E1), 17α-ethynylestradiol (EE2), N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMOR) and N-nitrosodiethylamine (NDEA). In general, sand filtration was ineffective in removing the contaminants from a tertiary treated wastewater, with the exception of E1 and EE2, where efficient removals were observed after approximately 150 d. Batch degradation experiments confirmed that the removal of E1 was through biological activity, with a pseudo-first-order degradation rate constant of 7.4 × 10 −3 h −1. GAC filtration was initially able to effectively remove all contaminants; although removals decreased over time due to competition with other organics present in the water. The only exception was atrazine where removal remained consistently high throughout the experiment. Previously unreported differences were observed in the adsorption of the three nitrosamines, with the ease of removal following the trend, NDEA > NMOR > NDMA, consistent with their hydrophobic character. In most instances the removals from the pilot-scale filters were generally in agreement with the laboratory-scale filter, suggesting that there is potential in using laboratory-scale filters as monitoring tools to evaluate the performance of pilot- and possibly full-scale sand and GAC filters at wastewater treatment plants.

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.

Water recycling — forwards or backwards for public health?

Water recycling — forwards or backwards for public health?

Water recycling — forwards or backwards for public health?

Water recycling — forwards or backwards for public health?

Removal of chemical and microbiological contaminants from domestic greywater using a recycled vertical flow bioreactor (RVFB)

Reuse of domestic greywater (GW) for non-potable purposes is emerging as an important approach to the management and conservation of water resources, particularly in rural and developing areas where small-scale decentralized treatments are suited. Recently, researchers at Ben-Gurion University (Israel) have developed a modular system – the recycled vertical flow bioreactor (RVFB) – for the removal of chemical contaminants from GW. We report on the removal of chemical contaminants, indicator organisms, and opportunistic pathogens from GW using this system. Synthetic GW, enriched with wastes from a dining hall, was added to experimental RVFB systems. The greywater was recirculated for 2–3 days at which time half of the water was removed from each system and replaced with fresh synthetic GW. Removal of chemical and microbiological contaminants was determined by comparing influent to effluent samples obtained after 8 and 72 h treatment in the systems. GW treatment using the RVFB system reduced effluent concentrations for NO 3-N, total ammonia nitrogen, NO 2-N, total suspended solids, boron, and anionic surfactants to below the levels considered acceptable for either recreation or irrigation. Reduction in chemical contaminants was associated with a significant increase in the number of both heterotrophic bacteria and surfactant-degrading bacteria within the RVFB. Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa were present at the beginning of each treatment cycle. Treatment using the RVFB system resulted in final E. coli concentrations that met the USEPA water quality criteria for recreational water. Viable S. aureus and P. aeruginosa were consistently present in samples obtained at the end of the 72 h treatment period. The survival of these non-enteric opportunistic pathogens underscores the need for the consideration of additional indicator organisms to monitor and assure the safe reuse of GW.