Point-of-use Devices Research Articles

Point‐of‐Use Devices for Attenuation of Trace Organic Compounds in Water

Trace organic compounds (TOrCs) continue to be detected in drinking water, and their recalcitrance makes them difficult to attenuate without installing expensive advanced treatment processes. Because human consumption is a small portion of net household water use, point‐of‐use (POU) devices may provide additional security against drinking water contaminants. This research evaluated three pitcher and two refrigerator POU devices using two waters. Refrigerator POU devices removed more TOrCs over the manufacturer's expected lifetime in terms of total mass than the pitcher POU devices. Average removal through all filters for nonionic, hydrophobic compounds was higher than for hydrophilic compounds in both waters. Removal of ionic compounds was enhanced by cation/anion exchange resins present in pitcher POU devices. Results indicated that POU devices are capable of removing significant amounts of organic contaminants in water. However, removal of a specific compound depends on its molecular properties, treatment technology implemented, and water quality and lifetime of the cartridge.

Quality of Drinking Water Treated at Point of Use in Residential Healthcare Facilities for the Elderly.

Municipal tap water is increasingly treated at the point of use (POU) to improve the acceptability and palatability of its taste. The aim of this study was to assess the bacteriologic and nutritional characteristics of tap water treated at the point of use in residential healthcare facilities for the elderly. Two types of POU devices were used: microfiltered water dispensers (MWDs) and reverse-osmosis water dispensers (ROWDs). All samples of water entering the devices and leaving them were tested for the bacteriological parameters set by Italian regulations for drinking water and for opportunistic pathogens associated with various infections in healthcare settings; in addition, the degree of mineralization of the water was assessed. The results revealed widespread bacterial contamination in the POU treatment devices, particularly from potentially pathogenic species. As expected, the use of ROWDs led to a decrease in the saline content of the water. In conclusion, the use of POU treatment in healthcare facilities for the elderly can be considered advisable only if the devices are constantly and carefully maintained.

Voltage Asssisted Photocatalytic Flow through Cell for Inactivation of Biological Pathogens Using Titania Nanotube Arrays

Diseases stemming from pathogen contaminated water kills 3.4 million people annually; despite our centralized water treatment facilities in the US, we are not immune to tainted drinking water. Aging infrastructure and natural disasters can cause limited access to potable water, making point-of-use (POU) disinfection devices critical for survival. In this work, a POU device using a voltage assisted photocatalytic flow through cell, was designed and built for the disinfection of water under various conditions. Anodically formed titania nanotube arrays (TNAs) were used as the photocatalytic component of the cell. The TNAs were characterized via x-ray diffraction, scanning electron microscopy and photoelectrochemical measurements. Voltage assisted inactivation was examined under different light intensities, water chemistries and applied biases. Complete biocide (a 10-log reduction) of Escherichia coli (E. Coli) W3110, was achieved in 15 s of contact time under 25 mW/cm2 insolation and an anodic bais of 3 V. The presence of chloride ions was found to enhance disinfection as chlorine radicals participate in bacterial inactivation; however, sulfate and nitrate ions were found to inhibit inactivation. It was also determined that TNAs annealed in a reducing atmosphere performed significantly better than those annealed in air. Overall, this voltage assisted photocatalysis methodology proved to be highly effective in complete inactivation of E. Coli. Figure 1

DNA extraction-free quantification of Dehalococcoides spp. in groundwater using a hand-held device.

Nucleic acid amplification of biomarkers is increasingly used to measure microbial activity and predict remedial performance in sites with trichloroethene (TCE) contamination. Field-based genetic quantification of microorganisms associated with bioremediation may help increase accuracy that is diminished through transport and processing of groundwater samples. Sterivex cartridges and a previously undescribed mechanism for eluting biomass was used to concentrate cells. DNA extraction-free loop mediated isothermal amplification (LAMP) was monitored in real-time with a point of use device (termed Gene-Z). A detection limit of 10(5) cells L(–1) was obtained, corresponding to sensitivity between 10 to 100 genomic copies per reaction for assays targeting the Dehalococcoides spp. specific 16S rRNA gene and vcrA gene, respectively. The quantity of Dehalococcoides spp. genomic copies measured from two TCE contaminated groundwater samples with conventional means of quantification including filtration, DNA extraction, purification, and qPCR was comparable to the field ready technique. Overall, this method of measuring Dehalococcoides spp. and vcrA genes in groundwater via direct amplification without intentional DNA extraction and purification is demonstrated, which may provide a more accurate mechanism of predicting remediation rates.

Defluoridation of drinking water using Al3+-modified bentonite clay: optimization of fluoride adsorption conditions

Al3+-bentonite clay (Alum-bent) was prepared by ion exchange of base cations on the matrices of bentonite clay. Intercalation of bentonite clay with Al3+ was performed in batch experiments. Parameters optimized include time, dosage, and Al3+ concentration. Physicochemical characterization of raw and modified bentonite clay was done by X-ray fluorescence, X-ray diffraction, energy dispersive X-ray spectrometry attached to scanning electron microscopy, Brunauer–Emmett–Teller analysis, cation exchange capacity (CEC) by ammonium acetate method, and pHpzc by solid addition method. Chemical constituents of water were determined by atomic absorption spectrometry (AAS), ion selective electrode (Crison 6955 Fluoride selective electrode) and a Crison multimeter probe. For fluoride removal, the effect of contact time, adsorbent dosage, adsorbate concentration, and pH were evaluated in batch procedures. The adsorption capacity of fluoride by modified bentonite clay was observed to be 5.7 mg g−1 at (26 ± 2) °C room temperature. Maximum adsorption of fluoride was optimum at 30 min, 1 g of dosage, 60 mg L−1 of adsorbate concentration, pH 2–12, and 1:100 solid/liquid (S/L) ratios. Kinetic studies revealed that fluoride adsorption fitted well to pseudo-second-order model than pseudo first order. Adsorption data fitted well to both the Langmuir and Freundlich adsorption isotherms, hence, confirming monolayer and multilayer adsorption. Alum-bent showed good stability in removing fluoride from ground water to below the prescribed limit as stipulated by World Health Organization. As such, it can be concluded that Alum-bent is a potential defluoridation adsorbent which can be applied in fabrication of point of use devices for defluoridation of fluoride-rich water in rural areas of South Africa and other developing countries. Based on that, this comparative study proves that Alum-bent is a promising adsorbent with a high adsorption capacity for fluoride and can be a substitute for conventional defluoridation methods.

Decision support system to select sustainable point-of-use/point-of-entry treatment systems (D4SPOUTS)

Point-of-use (POU) and point-of-entry (POE) devices are, in some situations, considered to be a viable solution for drinking water suppliers and consumers alike to deal with site specific drinking water issues. This paper introduces a newly developed decision support system (DSS) that employs decision making techniques to select among the various devices based on their characterization and sustainability assessment. Careful illustration of the various aspects and components of the DSS is provided and the decision process is explained. Aspects of validity, usability and sensitivity analysis are demonstrated through a hypothetical case study for removing lead introduced in the distribution system of municipally treated drinking water. The output of the DSS helps to determine the more sustainable treatment devices which should have positive implications for the application of POU and POE devices. Other potential uses of the DSS are described to illustrate its versatility and usefulness. The DSS is not intended to replace common engineering practice in selecting POU and POE treatment systems, but rather to give support to the users by providing the necessary information about all possible solutions.

POU devices in large buildings: Lead removal and water quality

The performance of point‐of‐use (POU) devices to remove dissolved and particulate lead (Pb) and their effect on tap water quality were investigated in a large building under typical usage patterns and during one year. Both forms of Pb were efficiently removed, although materials downstream of the POU devices slightly increased total Pb levels at the tap. No evidence of POU breakthrough was observed following stagnations carried out before sampling. Although measurements of heterotrophic place counts and total and live bacteria on the POU material itself indicated no significant colonization, small but significant increases in viable bacteria at the tap suggest that colonization occurred in the piping and tap downstream of the POU devices in the absence of chlorine residual. This study suggests that these devices are a useful remediation approach to control Pb in large buildings, providing that building maintenance procedures are issued for POU devices.

Arsenate removal from simulated groundwater with a Donnan dialyzer

A simple point of use (POU) device based on the theory of Donnan dialysis was developed for the removal of arsenate (As(V)) in the present study. A commercial anion exchange membrane was used as a semipermeable barrier between the feed and stripping solution (As(V)-spiked groundwater and a 12gL−1 table salt solution, respectively). The proposed POU device could be operated 26 times before replacing the stripping solution. In each batch, approximately 80% of the arsenate anions were transported across the membrane within 24h, and the arsenic concentration of the stripping solution was finally more than 180 times greater than that of the treated water. Cations were well preserved in treated water; however, a slight increase in the sodium ion concentration was observed due to electrolyte leakage. Alternatively, the chloride ion concentration significantly increased at the expense of a loss of sulfate and bicarbonate. The quality of treated water was in compliance with drinking water standards. Membrane fouling was investigated, and a reduction in the As(V) removal rates was not observed when the membrane was used repeatedly. Our results showed that the proposed Donnan dialysis POU device could effectively remove arsenic from drinking water in rural areas in a sustainable manner.

Nitrate removal from drinking water by point of use ion exchange.

A laboratory study was conducted to investigate the ability of a special type of strongly basic resin MP500WS for the removal of nitrate from different waters. Two different types of Point-of-Use (POU) devices containing an identical resin were used. MP500WS known as macro porous was used in POU devices for removal of high concentrations of nitrate and sulfate ions from water. Sulfate and chloride ions are considered the most important interferences in the treatment process of nitrate by most anion exchange resins. The results obtained by treatment of water samples having different ranges of nitrate (20 to150 mg/L), sulfate (50, 100 and 800 mg/L) and chloride (50 and 500 mg/L) have shown that the method was suitable for delivering water with NO(3) concentrations in less than its maximum contaminant level (MCL=45 mg/L) as long as the initial NO(3), SO(4) and Cl concentration has remained in less than 150, 100 and 500 mg/L, respectively. For this purpose, POU systems that utilize a suitable tested resin may be considered as an economical and effective alternative to conventional systems. This study shows this strategy very effective for nitrate reduction to acceptable levels when macro porous type strongly basic resin is used as the resin.

Comparison of Byproduct Formation in Waters Treated with Chlorine and Iodine: Relevance to Point-of-Use Treatment

Due to their efficacy in deactivating a range of microbial pathogens, particularly amoebic cysts, iodine-based disinfectants have been a popular option for point-of-use (POU) drinking water disinfection by campers, the military, and rural consumers in developing countries. Recently, concerns regarding the formation of cytotoxic and genotoxic iodinated disinfection byproducts (I-DBPs) have arisen during chloramine disinfection of iodide-containing waters in the developed world; similar concerns should pertain to iodine-based POU disinfection. Because there are alternative POU disinfection techniques, including chlorine-based disinfectants, this paper compared disinfection byproduct formation from a range of iodine-based disinfectants at their recommended dosages to chlorination and chloramination under overdosing conditions. Just as chloroform was the predominant trihalomethane (THM) forme during chlorination or chloramination, iodoform was the predominant THM formed during iodination. Conditions fostering THM formation were similar between these treatments, except that THM formation during chlorination increased with pH, while it was slightly elevated at circumneutral pH during iodination. Iodoform formation during treatment with iodine tincture was higher than during treatment with iodine tablets. On a molar basis, iodoform formation during treatment with iodine tincture was 20-60% of the formation of chloroform during chlorination, and total organic iodine (TOI) formation was twice that of total organic chlorine (TOCl), despite the 6-fold higher oxidant dose during chlorination. Based upon previous measurements of chronic mammalian cell cytotoxicity for the individual THMs, consumers of two waters treated with iodine tincture would receive the same THM-associated cytotoxic exposure in 4-19 days as a consumer of the same waters treated with a 6-fold higher dose of chlorine over 1 year. Iodoacetic acid, diiodoacetic acid, and other iodo-acids were also formed with iodine tincture treatment, but at levels <11% of iodoform. However, testing of a Lifestraw Personal POU device, which combines an iodinated anion exchange resin with activated carbon post-treatment, indicated minimal formation of I-DBPs and no iodine residual. Although N-nitrosamines have been associated with oxidant contact with anion exchange resins, N-nitrosamine formation rapidly declined to low levels (4 ng/L) using the Lifestraw device after the first few flushes of water.

Lead removal from tap water using POU devices

Common point‐of‐use (POU) devices that met NSF/ANSI‐53 certification standards for lead removal before July 16, 2007, were evaluated for the reduction of lead and other trace metals in drinking water. Systematic testing and evaluation of various POUs focused on particulate and dissolved lead removal efficacy, under conditions different from those addressed in the NSF‐53 testing protocol (particle type, water tested, lead levels). Tap‐mounted and under‐the‐sink POUs showed, globally, adequate removal performance, although the NSF threshold value for lead of 10 pg/L was occasionally slightly exceeded. Pour‐through POUs failed to remove particulate lead, decreased pH, did not reduce turbidity, and were the least efficient for chlorine removal. Copper removal was effective for any concentration tested, and silver was detected in effluent water. Nitrification did not increase the dissolution of lead particles trapped in the filters.

Fabrication and characterization of iron oxide ceramic membranes for arsenic removal

Nanoscale iron oxide particles were synthesized and deposited on porous alumina tubes to develop tubular ceramic adsorbers for the removal of arsenic, which is an extremely toxic contaminant even in very low concentrations. Its natural presence affects rural and low-income populations in developing countries in Latin America and around the world, which makes it essential to develop a user-friendly, low energy demanding and low cost treatment technology. The fabricated ceramic membranes can be operated with minimal trans-membrane pressure difference and do not require pumping. The support tubes and final membrane have been characterized by surface area and porosity measurements, permeability tests and scanning electron microscopy (SEM) imaging. Arsenic concentrations were determined by inductively coupled plasma–optical emission spectroscopy (ICP-OES). Due to its low cost and simple operation, the system can be applied as a point of use device for the treatment of arsenic contaminated groundwaters in developing countries.

Arsenic in groundwater in New England — point-of-entry and point-of-use treatment of private wells

Arsenic in drinking water is a factor that has recently been shown to be a possible cause for an elevated bladder cancer risk in northern New England. More than 40% of the population in this region uses private wells as the primary drinking water source. Point-of-entry (POE) and point-of-use (POU) arsenic removal systems can be an attractive and effective way for a well owner to treat the water to reduce the arsenic level to below the US EPA maximum contaminant level (MCL) of 10 μg/L (10 ppb). A study based on data collected from customers in eastern New England and New Jersey has been conducted to identify areas with elevated arsenic concentrations and to assess the performance of installed POE and POU devices based on arsenic adsorption on hybrid hydrous iron oxide/polymer media. The first of these arsenic treatment systems became operational in November 2005 and as of August 26, 2007, a total of 275 systems has been installed. The raw water from all the systems was sampled at startup and 62 have since been re-sampled. Of the tested waters, 77% had arsenic concentrations less than 50 ppb which was the US EPA MCL for arsenic until January 2006. At this level, the lead column of the POE system would be expected to last for a minimum of 1.5 years in most waters before replacement is required. However, the actual life of the media column will depend upon the volume of processed water and the water chemistry (arsenic speciation, silica, phosphate and pH). To date, the collected data seem to fall into areas that have been identified by the US Geological Survey for the New England region and the New Jersey Geological Survey in New Jersey as having high arsenic concentrations in the groundwater. Periodic arsenic analyses of the customer waters have shown that the POE and POU systems operate as predicted and meet the needs of the customers in terms of arsenic removal and ease of operation. Only 10 systems have required replacement of the exhausted lead column since becoming operational, which is 4.2% of all installed devices. This means that even in challenging conditions the lead column effectively operates for an average of 10–12 months.

Point of Use: The Final Barrier

This article focuses on problems that can occur within the distribution system and the point of use (POU) devices that can be used to address these problems. The causes of contamination discussed in the article include: formation of disinfection byproducts (DBPs); distribution system repairs and replacement; hydraulic surges; power outages; fire flow; and, backpressure. The burgeoning growth of the bottled water industry is mentioned, along with a variety of technologies used in POU devices that include sediment filters, submicron filtration and activated carbon systems, and disinfection systems. The article also discusses the costs of using POU devices and who should be responsible for installing and maintaining the devices.

Effects of time and point-of-use devices on arsenic levels in Southeastern Michigan drinking water, USA

Health effects associated with chronic, low-level exposures to arsenic in drinking water (<100 μg/L) remain unclear, in part due to uncertainties in assessing exposure. Drinking water concentrations have been used to assess past exposure to arsenic in epidemiological studies, under the assumption that a single measurement can be used to estimate historical exposure. This study aims to better understand (1) temporal variability in arsenic concentrations in drinking water and (2) the impact of point-of-use (POU) treatment devices on arsenic exposure measurements, and on reliability of the exposure measurement for population-level studies. Multiple drinking water samples were collected at two points in time (an average of fourteen months apart) for 261 individuals enrolled in a case-control study of arsenic exposure and bladder cancer in Michigan. Sources of drinking water included private wells (n=221), public water supplies (n=33), and bottled water (n=7); mean arsenic concentration was highest in private wells (7.28 μg/L) and lowest in bottled water samples (0.28 μg/L). Arsenic concentrations in primary drinking water samples were highly correlated (r=0.88, p<0.0001, n=196), with 3% of the water sources exceeding the United States Environmental Protection Agency's Maximum Contaminant Level (MCL) in one sample but not in the other sample. Measurement reproducibility did not vary by type of POU device (e.g., softener, filter, reverse osmosis system). Arsenic concentrations did differ, however, between samples treated with POU devices and untreated samples taken on the same day. Substantial differences in arsenic concentrations were consistently observed for reverse osmosis systems; other POU devices had variable effects on arsenic concentrations. These results indicate that while a single residential arsenic measurement may be used to represent exposure in this region, researchers must obtain information on changes in water source and POU treatment devices to better characterize population exposures over time.

Comparison of the microbiologic quality of point-of-use (POU)-treated water and tap water

Activated carbon filtration devices placed on household faucets are used to improve the taste and odour of tap water. However, there has been a concern that the growth of bacteria capable of causing opportunistic infections in these devices might present a public health risk. The water quality from point-of-use (POU) water activated carbon treatment devices and that of tap water with POU-connections and tap water without POU devices were compared. Heterotrophic plate count (HPC) bacteria, total and faecal coliforms, and acid-fast organisms (Mycobacteria spp.), as well as, the opportunistic bacterial pathogens Aeromonas hydrophila, Plesiomonas shigelloides, and Pseudomonas aeruginosa were enumerated. The highest concentration of bacteria was found in POU-treated water. P. aeruginosa, acid-fast organisms, and total coliforms were present in 38.5, 43.8, and 82.4% of the samples, respectively. HPC bacteria were present in all of the POU-treated water samples, with concentrations ranging from 102 to 107 colony forming units/mL. Neither faecal coliforms nor P. shigelloides were recovered from any samples. Tap water with a POU-connection also had higher numbers of bacteria than tap water samples. It was concluded that tap water without POU devices had lower numbers of A. hydrophila, acid-fast organisms, HPC bacteria, P. aeruginosa and coliforms than POU-treated water, and tap water with a POU-connection. The use of POU-devices may amplify the numbers of bacteria present in the tapwater by promoting biofilm formation. Based on a daily ingestion of two liters of POU treated water, A. hydrophila and P. aeruginosa had a probability of less than 10 − 6 of colonizing the gut; however, annual risks could be as much as 100-fold greater.

What Will Be Expected of Utilities That Install POU Devices?

This month's question addresses how a community water system (CWS) must take control and ownership of any official point‐of‐use (POU) treatment program for a systemwide contaminant. The US Environmental Protection Agency (USEPA) guidelines allow small utilities to use POUs for achieving compliance in removing contaminants, as long as the CWS controls the operation and maintenance of devices it has installed. Also, utilities must provide a maintenance service for these home treatment units. Other topics covered in this article include installation considerations, regular maintenance tasks, and assessing costs.

Selecting the Right POU Device

This article provides information for small systems considering point‐of‐use (POU) treatment and for larger systems that receive inquiries from their customers about the use of home treatment devices.

Nontraditional approaches for providing potable water in small systems: Part 1

Combined central treatment and distribution are relatively recent phenomena, having only become standard in the last century or so. Given that &lt;1% of treated water is actually ingested, the concept of treating all of the water in a system to optimal drinking water specifications is becoming more impractical, especially in the face of increasingly stringent regulations, high costs, water quality deterioration during distribution, and reduced access to high‐quality source water. The Safe Drinking Water Act has created special opportunities for small systems to use decentralized compliance through point‐of‐use (POU) and point‐of‐entry (POE) techniques to provide supplemental treatment for part of the delivered piped water. Two‐tier water systems that include the use of POU or POE devices or possibly even bottled water provide a feasible and cost‐effective means of delivering safe water to consumers. Community‐managed decentralized strategies also offer small systems the opportunity to achieve safer, higher‐quality drinking water than these communities might otherwise have had, more quickly and at reasonable costs. These alternative approaches create new logistic, management, compliance, monitoring, and regulatory oversight issues, but these are solvable. Most of the principles supporting decentralized solutions for small systems are also applicable to providing community‐managed “beverage‐quality” drinking water in much larger systems. For all water providers, decentralized and centralized treatment combinations represent a better use of diminishing water resources and limited finances.

Removing lead in drinking water with activated carbon

AbstractA point‐of‐use (POU) granular activated carbon (GAC) fixed bed adsorber (FBA) was evaluated for reduction of soluble and insoluble lead from drinking water. Some of the factors which affect lead removal by GAC were evaluated, such as carbon type, solution pH, and a limited amount of work on competitive interactions. The design criteria for lead reduction by a POU device are also addressed. Minicolumns were used to evaluate the capacity of carbon for lead under a variety of conditions. The importance of surface chemistry of the carbon and the relationship with the pH of the water for lead reduction was demonstrated. Results indicate that a properly designed POU‐GAC‐FBA can reduce lead in drinking water to below the EPA action level of 15 ppb while being tested under a variety of conditions as specified under the National Sanitation Foundation (NSF) International Standard 53 test protocol.