A bench-scale study of the degradation of four selected pharmaceuticals and personal care products (PPCPs) was carried out using UV and UV/H₂O₂ treatment employing low pressure (LP) and medium pressure (MP) lamps. The target substances included the pharmaceutical compounds ibuprofen, naproxen, and gemfibrozil, along with the bactericide triclosan. There were four main objectives of the study, as follows: to evaluate the removal of the target compounds using UV irradiation alone and UV/H₂O₂, to determine the reaction kinetics for direct and indirect photolysis of each selected compound, to determine the influence of major water quality parameters on the efficacy of treatment, and to compare the applied UV and UV/H₂O₂ doses to those that have been found to be effective for disinfection and removal of taste and odour compounds, respectively. For initial ultra-pure water experiments the target compounds were spiked at concentrations of approximately 250 µg/L (~1 µM). In latter ultra-pure water experiments and in the partially-treated water experiments, the selected PPCPs were spiked at a lower range (c~500-1000 ng/L), which is more representative of reported environmental concentrations. In an ultra-pure water matrix, a high LP fluence of 1000 mJ/cm² caused only triclosan to substantially degrade. Furthermore, with LP-UV/H₂O₂ only triclosan and naproxen had average percent removals above 60% at a typical disinfection fluence of 40 mJ/cm² with 100 mg/L H₂O₂. Complete degradation of all four compounds in ultra-pure water was achieved with very high fluences (compared to those used for UV disinfection) with MP-UV alone (at or above 1000 mJ/cm²) or with relatively high fluences for MP-UV/H₂O₂ (200-300 mJ/cm²) with 10 mg/L H₂O₂. Overall, when compared at similar applied fluences, the MP lamp was much more effective than the LP lamp. Furthermore, the addition of H₂O₂ typically increased removal rates, in some cases substantially, through formation and subsequent reaction of the PPCP with the •OH radical. When target substances were treated all together in an ultra-pure water solution, removals were lower than when they were treated independently at the same individual concentrations (~250 µg/L) this may simply have been the result of a higher total contaminant concentration in solution, which lessened the availability of the •OH radical and incident UV irradiation for degradation of all compounds. On the other hand, removals were improved when the combined target compounds were present at a lower individual concentration range (~750 ng/L), which suggests that removals may be concentration driven, with reduced matrix effects seen at lower overall contaminant concentrations. Furthermore, during the partially-treated water experiments, variability in treatment performance was observed with differing water quality; however, it was not evident which specific quality parameters influenced treatment effectiveness. On the other hand, substantial and sometimes complete, degradation of the target compounds was still seen in the partially-treated water with high MP-UV/H₂O₂ doses (e.g. 300 mJ/cm² + 10 mg/L H₂O₂ and 500 + 10 mg/L H₂O₂). For the kinetic experiments, compounds were spiked individually in ultra-pure water (c~250 µg/L = ~1µM). The photolysis of the target compounds during treatment was assumed to be a pseudo-first-order reaction. Kinetic parameters were determined for both direct and indirect photolysis for both lamps. The calculated rate constants confirmed the importance of •OH radicals for degradation of these compounds, especially for ibuprofen and gemfibrozil. For ibuprofen and gemfibrozil, direct photolysis rate constants could not be determined for LP-UV because very little degradation was seen at the fluences tested. LP-UV direct phototlysis rate constants for naproxen and triclosan were 0.0002 and 0.0033 cm²/mJ, respectively. Overall rate constants describing degradation of the four compounds due to LP-UV/H₂O₂ ranged from 0.0049 to 0.0124 cm²/mJ. All four compounds had fluence-based reaction rate constants for MP-UV indirect photolysis of approximately 0.01 cm²/mJ, while MP-UV direct photolysis rate constants ranged between 0.0007-0.007 cm²/mJ, with ibuprofen having the lowest and triclosan the highest. The overall trends were similar to those seen by other researchers for the removal of taste and odour compounds. For example, fluences required for substantial removal were much higher than typical disinfection doses, the MP lamp was more effective than the LP lamp (when compared solely on a fluence-basis), and the addition of H₂O₂ improved removals. On the whole, UV/H₂O₂ appears to be a very promising technology for the removal of these selected PPCPs during drinking water treatment, and is likely to be equally effective for other, similar contaminants.

A series of pilot-scale granular media filtration experiments was conducted to examine the effect of media roughness on filter performance and to evaluate the applicability of spherical, rough engineered ceramic filter media for use in granular media filters used for drinking water treatment. Filter media performance was assessed using turbidity and particle count reductions, Cryptosporidium oocyst and oocyst-sized microsphere removal, head loss and stability of operation. Experiments were designed to allow related facets of current filtration research to be examined. These included: effect of loading rate, coagulant type and dosage, and suitability of latex microspheres as surrogates for Cryptosporidium oocyst removal by granular media filtration. This study indicated that increased filter media roughness consistently improved turbidity and particle count reduction under the conditions investigated. As well, the engineered media also consistently achieved greater stability of operation during non-ideal operational periods (e.g. sudden change in filter influent turbidity).Oocyst removals were generally improved by media roughness, though this improvement was reliant on operating conditions, such as coagulant dose and type of coagulant used. The surrogate relationship between oocyst-sized latex microspheres and oocyst removal by filtration was also dependent on coagulant dose and type of coagulant. During trials with no coagulant addition, contrasts in oocyst removal were not significant, suggesting that neither surface roughness nor the size of media used were significant factors impacting oocyst removal by filtration during those periods of impaired operation. When pre-treating raw water with PACl, the engineered ceramic media achieved up to 1.25 log10 higher oocyst removals than conventional media. This improvement in oocyst removal relative to conventional media was not observed when alum was used as the primary coagulant, however. Future studies should directly compare engineered and conventional media filtration performance, using other raw water sources and different operating conditions. Biologically active filtration should also be included in future performance studies because the rough, highly porous surface of the engineered ceramic media is likely to provide excellent biofilm support.

The use of sunlight for water disinfection has been practiced since ancient times. Only in the last three decades has solar disinfection become widely recognized as a viable means of providing safe drinking water to the disadvantaged portion of the world’s population. The World Health Organization estimates that 1.6 million people die every year because of waterborne diseases. <br/><br/> The Swiss Federal Institute of Environmental Science and Technology and their Department of Water and Sanitation in Developing Countries have been instrumental in propagating the solar water disinfection (SODIS) process in developing countries. The reason for this technology being widely used and accepted is its ease of use and effectiveness: water is placed in clear plastic bottles and exposed to direct sunlight for approximately six hours. The microorganisms in the water absorb the sunlight and it, in turn at sufficient UV dosages, causes mutations to their genetic material, inhibiting reproduction. Although some pathogens may still be viable they are no longer infective. The result is microbiologically safe water. <br/><br/> Research to date has explored everything from which colour and size the SODIS containers should be to whether adding catalysts to the water before exposure improves disinfection. Apart from a few studies that examined the effect of shaking the bottles (to entrain air) before exposure, there has been limited research on pretreatments for enhancing solar disinfection. <br/><br/> The focus of this project was to explore two pretreatments for SODIS and determine how they affect the efficiency of the process. The first stage was to examine one of the currently used pretreatments: cleaning the water containers before use. The second stage was to develop an accessible, low-cost filtration technique to remove particles from the water before exposure to sunlight. Particles in the water disperse the light and protect the microorganisms from being inactivated, so it is important to have as few particles as possible; the recommended upper limit is 30 NTU for solar disinfection. In many instances, surface water with high turbidity (greater than 200 NTU) serves as the only source for drinking water in developing areas. <br/><br/> The first series of experiments in the current research evaluated if cleaning the bottles was necessary and if so, which cleaning agents would be most effective and available. The agents selected were 70% isopropyl alcohol, a soap-water mixture, and lime juice. The experiments demonstrated that cleaning with 70% isopropyl alcohol did not affect the process in any way. Cleaning with the soap-water mixture did have a slightly negative effect on the process; there was substantial microbial recovery when bottles were kept in the dark overnight. In the case of the lime juice, it actually inhibited the disinfection process. It is necessary to remove any debris that might exist within the containers before using them, but using a chemical cleaning agent or mechanically scrubbing can decrease the amount of disinfection that occurs during SODIS. Thus, it is suggested that using a chemical pretreatment is not necessary and has the potential to inhibit disinfection, especially without proper training or technical knowledge. <br/><br/> The second series of experiments identified the optimal design for a low-cost roughing filter that could be used to remove particles from water before exposure to sunlight. The roughing filter that was built from the same plastic pop bottles used for solar disinfection, as well as gravel and sand. It was constructed with three centimetres of gravel on the bottom of the pop bottle and then 17 cm of coarse sand was added on top to make the total filter height 20 cm. A 0.6 mm hole was made at approximately 1.5 cm from the bottom of the bottle using a standard sewing needle. Each filter run consisted of 10 L of water at approximately 200 NTU. Experimental results indicated that 95% removal of turbidity could be achieved. These roughing filters can be constructed from readily available and affordable materials in developing countries and produce an effluent water quality of less than 30 NTU when initial turbidities are greater than 200 NTU. <br/><br/> Finally, the third series of experiments focused on testing the newly developed roughing filter in series with SODIS to evaluate the system as a whole. The results confirmed that using the roughing filter, as a pretreatment to SODIS, is a highly effective means of improving the disinfection potential of the process. These roughing filters produce an effluent water quality of less than 30 NTU, which is required for SODIS, making them a viable pretreatment for turbid water intended for SODIS use.

The drinking water contamination tragedy in Walkerton, Ontario during the spring of 2000 led to many changes in water management for the province. Among these changes has been the increased use of the multiple barrier approach (MBA) to safe drinking water as the basis of water management for communities throughout Ontario. The MBA is also used in the management of water for First Nations communities throughout Ontario and Canada. Literature on water quality management for First Nations suggests that despite these changes, many communities continue to face challenges for ensuring the safety and quality of their drinking water supplies. Fort William First Nation, Gull Bay First Nation, and Mattagami First Nation, were selected for this study in order to investigate the use of the MBA in these communities. Data was collected using key informant interviews with representatives of institutions that affect water management for the case study communities, direct observations during visits to two of the communities and attendance at a First Nations water policy forum, and through a review of recent reports and publications on safe drinking water for First Nations. The research has provided insight into the challenges that the case study communities face for ensuring safe drinking water under the MBA, as well as opportunities that exist to address those challenges. The findings suggest that the MBA currently does not meet the unique needs of some First Nations communities. They also suggest that specific adaptations of existing water management strategies to the MBA framework may lead to a more effective approach to ensure safe drinking water for First Nations communities. This thesis focuses on several key ways to make these changes: Strengthen public involvement and awareness; Introduce effective legislative and policy frameworks; Encourage research, science and technology for First Nations’ water management; Allocate sufficient financial resources to First Nations to recruit, train and retain qualified water managers and maintain drinking water infrastructure, and; Increase efforts to ensure that water management goals are supported by local and indigenous traditional knowledge, beliefs and perspectives.

Several health problems may be caused by excess nitrate in drinking water, the most important of which being methemoglobinemia, a potentially fatal disorder, in infants under six months of age. Many different parts of the world have been facing the problem of nitrate contaminated surface and groundwaters due in large part to excessive use of nitrate-based chemical fertilizers. In the Region of Waterloo, Ontario, Canada some groundwater sources have nitrate concentrations approaching the Health Canada and Ontario Ministry of the Environment maximum acceptable concentration (MAC) of 10 mg NO3--N/L. Finding a practical and economical way to reduce nitrate concentrations in representative groundwater in the Region of Waterloo was the overall objective of this research. To achieve this goal, nitrate removal technologies including biological denitrification, ion exchange (IX), reverse osmosis (RO), electrodialysis (ED), and chemical denitrification were reviewed and compared. IX and RO were found to be the most promising technologies for nitrate removal. They have also been approved by the United States Environmental Protection Agency (USEPA) as Best Available Technologies (BAT). To investigate the feasibility of IX and RO for nitrate removal from representative groundwater in the Region of Waterloo, bench-scale experiments were conducted and compared. These technologies could be considered for application at full- or point-of-use (POU)-scale. Decision support assistance for the selection of the appropriate technology for different technical and economical conditions is provided as an outcome of this work. Two nitrate-selective ion exchange resins (Dowex™ NSR-1 and Purolite® A-520E), two non-selective resins (Purolite® A-300E and Amberlite® IRA400 Cl), and a commercially-available RO POU device (Culligan® Aqua-Cleer® model RO30), which included a particle filter and a carbon block, were tested with deionized water and real groundwater.* IX results confirmed that production time before resin exhaustion was influenced by operating conditions, specifically bed depth as would be expected. It was also confirmed that the presence of competing anions (sulfate, chloride) and alkalinity adversely affected performance, with sulfate being the main competitor for nitrate removal. The extent of these effects was quantified for the conditions tested. At the end of the runs, the non-selective resins were prone to potential nitrate displacement and release into product water and are therefore not recommended. The nitrate-selective resins did not release previously adsorbed nitrate as their capacity became exhausted. Purolite® A-520E was identified as the best alternative amongst the four resins for removing nitrate from the representative groundwater source. The RO unit removed roughly 80% of the nitrate from groundwater. Background ions didn’t appear to compete with each other for removal by RO units, so RO might be a more appropriate technology than IX for nitrate removal from waters with high concentrations of sulfate or TDS. Since RO removes other background ions as well as nitrate, the product water of RO is low in alkalinity and can potentially be corrosive, if water from a small full-scale system is pumped through a communal distribution system. Post-treatment including pH adjustment, addition of caustic soda, and/or corrosion inhibitors may be required. While the carbon block did not play a substantial role with respect to removal of nitrate in the groundwater tested, a potential issue was identified when running RO systems without the carbon block. In deionized water (and presumably in very low alkalinity real waters) it was noted that RO nitrate removal efficiency dropped substantially as the alkalinity of the influent water approached zero. With respect to the scale of application of IX and RO devices, IX can be applied at full-scale without requiring large amounts of space. However, if feed water contains high concentrations of sulfate or TDS, nitrate leakage happens sooner and regeneration would be needed at more frequent intervals. Also, chloride concentrations in IX product water might exceed aesthetic objectives (AO) and should be monitored in cases of high feed water TDS. POU IX devices are not recommended when feed water nitrate concentration is high due to potential nitrate leakage into the product water when the resin is nearing exhaustion which increases public health risk. Issues associated with RO application at full-scale are high energy demand, low recovery, high costs, need of pre-treatment (fouling control), and post-treatment (corrosion control). On the other hand, POU RO devices may be acceptable since low recovery is of less importance in a household system, and product water corrosivity is less relevant. POU RO devices are preferable to POU IX units due to their lower risk of nitrate leakage into treated water. * Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

Point-of-use (POU) and point-of-entry (POE) water treatment are forms of decentralized water treatment that are becoming increasingly sought alternatives for ensuring the safety of drinking water. Although the acceptance of POU and POE systems is still the subject of some debate, it is generally acknowledged that they have a role to play in drinking water treatment. However, some of the main drivers for the increase in the use of POU and POE alternatives include: (1) the emergence of new technologies with high removal efficiencies of target contaminants; (2) the enhanced certification system of POU and POE treatment devices and components which ensures that devices have been well engineered to achieve defined contaminant removal targets and do not add contaminants from materials of construction; (3) the inclusion of POU and POE systems as acceptable means to comply with drinking water standards; and (4) the concerns voiced by consumers in several surveys regarding the safety of centrally treated drinking water; which, regardless of whether or not these concerns are justified, have led to an increase in the use of POU and POE treatment systems. With the commercialization of these devices the task of selecting a suitable device for treatment has become cumbersome. When the inherent complexity of a particular drinking water treatment task is added to the mix, a complex decision making situation is created. Thus the need for designing a decision support tool to compare and select POU and POE treatment systems was evident. Currently the best decision aid for selecting POU and POE systems is NSF International’s listing of the devices and their contaminant reduction claims. A significant contribution of this research is the depiction of an appropriate conceptual framework for developing usable and valid decision support systems (DSSs) to select or design water or wastewater treatment systems. A thorough investigation of the methods used to develop DSSs benchmarked a systematic approach to developing DSSs, which includes the analysis of the treatment problem(s), knowledge acquisition and representation, and the identification and evaluation of criteria controlling the selection of optimal treatment systems. Finally, it was concluded that there is a need to develop integrated DSSs that are generic, user-friendly and employ a systems analysis approach. Another significant contribution of this research is applying a systems analysis approach to outline aspects of implementation, management, and governance of POU and POE water treatment systems. The analysis also included a timeline of the progress of POU and POE treatment from regulatory, industry and certification, and research perspectives. Results of the analysis were considered the first step of a conceptual framework for the sustainability assessment of POU and POE treatment systems which acts as the basis for developing a decision support system that will help select sustainable POU or POE treatment systems. In the context of POU and POE treatment, sustainability encompasses providing: (a) safe drinking water to help maintain good human health and hygiene; (b) minimum negative impact on the environment; (c) better use of human, natural, and financial resources; (d) a high degree of functional robustness and flexibility; and (e) cultural acceptance thus encouraging responsible behavior by the users. The most significant contribution of this research is developing, for the first time, a set of sustainability criteria, objectives, and quantifiable indicators to properly assess the sustainability of the various POU and POE alternatives. Twenty five quantitative and qualitative indicators covering technical, economic, environmental, and socio-cultural aspects of implementing a POU or a POE system were defined. Results of a survey of experts’ judgment on the effectiveness of the developed list of indicators generated 52 comments from 11 experts, which helped in refining and enhancing the list. The conceptual framework for assessing the sustainability of POU and POE systems represented a blueprint for building the decision support system. Decision logic and cognitive thinking was used to formulate the calculation of the 20 refined indicators. The Analytical Hierarchy Process (AHP), a recognized Multi-criteria Decision Analysis (MCDA) tool, was employed to construct the structural hierarchy of sustainability indicators. Pairwise comparison was used to help in the analysis of indicators' relative importance and develop the indicators’ weights. A survey was designed to develop the relative weights of the indicators based on the average response of 19 stakeholders to a series of pairwise comparison questions pertaining to the relative importance of the indicators. Finally, the practical contribution of this research is the development of, for the first time, a new Decision Support System for Selecting Sustainable POU and POE Treatment Systems (D4SPOUTS) suitable for a particular water treatment case. The MCDA technique explained above is combined with designed screening rules, constraints, and case characteristics to be applied to a knowledgebase of POU and POE treatment systems incorporated in the DSS. The components of the DSS were built using Microsoft® Excel® and Visual Basic® for Applications. The quality of the DSS and aspects of its usability, applicability, and sensitivity analysis are demonstrated through a hypothetical case study for lead removal from drinking water. This research is expected to assist water purveyors, consultants, and other stakeholders in selecting sustainable and cost effective POU and POE treatment systems.

In the first phase of this project three enhanced large diameter (> 60 cm) residential wells were constructed at a study site in Lindsay, Ontario. Two wells were constructed using concrete tile casing while the other well was constructed using galvanized steel casing. Javor (2010) evaluated various aspects of drinking water well construction and design to determine the susceptibility of residential large diameter drinking water wells to surface water and airborne contamination. One of the purposes of these new installations was to remove the uncertainty with respect to construction methods, age and maintenance that is characteristic of residential drinking water well performance studies. Javor (2010) conducted a field and laboratory study to assess the performance of several design changes that were thought to improve the integrity of large diameter drinking water wells. These experiments were also used to determine whether one design was more prone to atmospheric and/or surface water contamination than another. During the second phase of this project routine monitoring was continued and data pertinent to assess the performance of the test wells were collected using the same instrumentation. This routine monitoring involved the visual inspection of the wells, collection of well water elevation, collection of soil temperature profile data, collection and analysis of water samples, and collection of cumulative water volumes extracted from the test wells. In addition to the routine monitoring, a ground penetrating radar (GPR) survey was performed in October 2010 to complement the previous data collected during February 2010. Smoke tracer tests were performed under non-frozen and frozen conditions to re-assess the potential pathways of contaminants between the atmosphere and the interior of the test wells. Bacteriological indicators and high concentrations of two dissolved ions were detected in all test and monitoring wells. The smoke tracer tests demonstrated that pathways for airborne contaminants to enter the test wells exist with similar pathways observed in the winter and the summer. GPR surveys indicated that the bentonite slurry annular sealant was the most homogeneous media. A baseline characterization of the microbial nature of the biofilm performed in three of the test wells (CTH1, ETH1 and ETH3) indicated that the sessile bacteria are more metabolically diverse than suspended bacteria, and that this diversity is even higher in the concrete cased wells. Biofilm characterization performed on concrete, fibreglass and galvanized steel coupons incubated in two of the test wells (concrete and galvanized steel) showed that bacteria in the concrete cased wells barely colonized on fiberglass and galvanized steel, while bacteria in the galvanized steel cased well did not have difficulty colonizing on any of the casing materials. The results of the biofilm cleaning study indicated that the use of pressure washing combined with chlorination effectively removed biofilm grown on galvanized steel and fibreglass casing materials. This study investigated various factors that could affect the performance of large diameter drinking water wells. Since the test wells used in this study were under the direct influence of surface water a comparison between the various annular sealants was problematic. However, the three enhanced test wells outperformed the conventional test well. The observations from the smoke tracer tests performed under non-frozen and frozen conditions indicate that the Poly-Lok lid seam is the most prevalent pathway for airborne contaminants to enter a well. Fibreglass may be the preferred choice for large diameter well casing material since fibreglass is corrosion resistant, lightweight, easy to install, has a high strength to weight ratio, and a greater degree of biofilm was able to be removed from fibreglass casing material than from galvanized steel casing material.

No description available.

Ronneby Miljö- och hälsoskyddskontor ville genom undersökningen få information om nitrathalter i enskilda dricksvattenbrunnar inom kommunen, med bakgrund av den nya miljökvalitetsnormen. Riktvärdet för nitrat är 50 mg/l. Halter som överstiger detta bör inte ges till barn under ett års ålder på grund av risk för methemoglobinemi. Jämförelsen skulle ske mellan områden präglade av jordbruk respektive skogsbruk, samt mellan grävda och borrade brunnar. Jämförelsen skulle även ske över tiden, mellan 1975-1990 till 2005. Urvalet av provtagningspunkter baserades på en sammanställning från befintligt arkiv samt efter en annons i dagspressen. Sammanställning av resultaten har gjorts i tabellform. Det framkommer av undersökningen att grävda och borrade brunnar uppvisar det förväntande resultatet: de grävda brunnarna svarar för en högre halt av nitrat samt att nitrathalterna har ökat under tidsperioden. För de borrade brunnarna är resultatet det omvända. Medan områden präglade av skogsbruk samt jordbruk inte har erhållit det förväntade resultatet. Jordbruket uppvisar en minskning av nitrathalterna medan skogsbruket har fått en förhöjd nitrathalt. En trolig orsak till de förhöjda nitrathalterna kan vara hästhållningen. Samt att deposition av olika kväveföreningar förekommer. / The environment protection and public health department in Ronneby wanted to have a study of nitrate concentrations in private water supply. The reason is a new environmental quality standard. The contaminant level for nitrate is 50 mg/l. Water containing excessive amounts of nitrate should not be given to infant with age under one year. It could cause a disease called methemoglobinemia. The purpose of the study was to compare areas pervade of agriculture respectively forestry, and between digged and drilled wells. The study was time dependent as well, from 1975 – 1990 until 2005. The testing points were selected from existing archive and an advertisement in the local paper. The results are shown in tabular forms. The study shows the expected result for digged and drilled wells. The higher amount of nitrate is found in the digged wells, and the concentration of nitrate have exceeded during time. For the drilled wells is the result the opposite. Areas pervade of forestry and agriculture didn't achieve the expected result. Agriculture shows a decrease of the amount of nitrate and forestry an increased amount of nitrate. The cause of increasing nitrate concentration is likely dependent on changed animal husbandry, for example horse keeping. Another reason could be the deposit of different nitrogen compounds.

Iron oxide-bearing minerals have long been recognized as an effective reactive media for arsenic-contaminated groundwater remediation. This research aimed to develop a technique that could facilitate in situ oxidative precipitation of Fe3+ in a soil (sand) media for generating a subsurface iron oxide-based reactive barrier that could immobilize arsenic (As) and other dissolved metals in groundwater. A simple in situ arsenic treatment process was successfully developed for treating contaminated rural groundwater using iron oxide-coated sand (IOCS). Using imbibition flow, the system facilitated the dispersive transport of ferrous iron (Fe2+) and oxidant solutions in porous sand to generate an overlaying blanket where the Fe2+ was oxidized and precipitated onto the surface as ferric oxide. The iron oxide (FeOx) emplacement process was significantly affected by (1) the initial surface area and surface-bound iron content of the sand, (2) the pH and solubility of the coating reagents, (3) the stability of the oxidant solution, and (4) the chemical injection schedule. In contrast to conventional excavate-and-fill treatment technologies, this technique could be used to in situ replace a fresh iron oxide blanket on the sand and rejuvenate its treatment capacity for additional arsenic removal. Several bench-scale experiments revealed that the resultant IOCS could treat arsenic-laden groundwater for extended periods of time before approaching its effective life cycle. The adsorption capacity for As(III) and As(V) was influenced by (1) the amount of iron oxide accumulated on the sand surface, (2) the system pH, and (3) competition for adsorption sites from other groundwater constituents such as silicon (Si) and total dissolved solids (TDS). Although the IOCS could be replenished several times before exhaustion, the life cycle of the FeOx reactive barrier may be limited by the gradual loss of hydraulic conductivity induced by the imminent reduction of pore space over time.