The presence of micropollutants, particularly pesticides, in surface waters across Canada has been of concern not only for their environmental impact, but also for their potential effects on human health and recalcitrant nature to conventional water treatment methods. Although ozone has been mainly applied for disinfection of drinking water, oxidation of trace organics by ozonation has been considered potentially effective. In an effort to meet increasingly stringent drinking water regulations, different solid catalysts have been used to enhance the removal of water contaminants by ozonation. In spite of the increasing number of data demonstrating the effectiveness of heterogeneous catalytic ozonation, the influence of different factors on the efficiency of micropollutants oxidation is still unclear.<p> In the present work, application of three solid catalysts in ozonation of two model micropollutants in pure water was examined using a laboratory-scale reaction system over a range of operating conditions. The three catalysts investigated were activated carbon, alumina, and perfluorooctyl alumina, and the two model micropollutants were the pesticides atrazine and 2,4-dichlorophenoxyactic acid. The effects of solution pH, presence of a radical scavenger, pesticide adsorption on catalyst, and catalyst dose on micropollutant removal were investigated. Solution pH was found to significantly influence the catalyst ability to decompose ozone into free hydroxyl radicals. The effect of these free radicals was markedly inhibited by the radical scavenger resulting in a negative impact on pesticides degradation. In general, the removal rate of pesticides was found to increase with increasing doses of catalyst.<p> In the ozonation process in the presence of activated carbon, atrazine removal rates increased four and two times when using a catalyst dose of 0.5 g L-1 at pH 3 and 7, respectively, whereas observed reaction rates for 2,4-D increased over 5 times in the presence of 1 × 10-4 M tert-butyl alcohol at pH 3. In the ozonation system catalyzed by 8 g L-1 alumina, the observed reaction rate constant of atrazine removal notably improved at neutral pH by doubling the micropollutant removal rate. For the pesticide 2,4-D in the presence of 1 × 10-4 M tert-butyl alcohol at pH 5, the observed removal rate was over ten times higher than that for the non-catalytic ozonation process using also using a catalyst dose of 8 g L-1. Modification of alumina to produce perfluorooctyl alumina resulted in a material able to significantly adsorb atrazine, while not exhibiting affinity for adsorption of 2,4-D. In spite of its adsorptive properties, perfluorooctyl alumina was found to enhance neither molecular ozone reactions nor ozone decomposition into hydroxyl radicals. Thus, the observed removal rates for atrazine and 2,4-D by ozonation in the presence of perfluorooctyl alumina did not increase significantly.

This current study is a lab-scale investigation focused on the treatment of stormwater runoff generated in wood-storage areas. The main target constituents of the proposed treatment were: metals (Cu, Cd, Co, V, Pb, Zn, Ni, Cr, Fe, As), COD, TOC, Phenols, and color. The method implemented for this project follows the main concept of using low-cost and environmentally friendly technologies and had as main steps the use of a by-product of wood-based industries - wood fly ashes as sorbents - followed by oxidation with H2O2 (Hydrogen Peroxide). The results obtained during this investigation were vey promising since satisfactory removal % was achieved. Removal rates of 98.5%, 86%, 89.6%, 79.6% were achieved for color, chemical oxygen demand (COD), total organic carbon (TOC) and phenols respectively. Furthermore a decrease in metals concentrations was also observed with the exception of chromium. The study showed that for 300 ml storm water, optimum conditions were with 7g wood fly ash, 5 hours time reaction, pH≈11.46 and 150 μl of a 30% H2O2 solution in a room temperature. To conclude it can be stated that the use of a by-product from wood industry to treat contaminated water from the same sector, following the concept of a closed-loop system, is promising and possible. However further studies need to be conducted in order to evaluate such system in scaled-up conditions.

According to the literature, the deterioration of water quality in pipeline networks of water distribution is not solely due to the deterioration of raw water quality outlet from water treatment plants, but primarily due to the multiplication of microorganisms in water distribution pipelines, a phenomenon known as after-growth or re-growth. Presently, the most effective method of a biological stability in treated water for controlling microbial re-growth is by limiting nutrients, including nitrogen, phosphorus, and organic carbon. The content of assimilable organic carbon (AOC) within organic carbon is considered to be the most main factor for controlling the growth of microorganisms in the water distribution systems. The objects of this work were to study the Cheng Ching Lake Water Treatment Plant (CCLWTP) in Kaohsiung and the Gong Yuan Water Treatment Plant (GYWTP) in Chiayi. Water samples were collected once a month from December 2008 to November 2009. The major difference between the study objects was that front one is an advanced water treatment plant, and the other a traditional one. In order to understand the difference in biological stability between these two water treatment plants, AOC meaurement was conducted. The goals of this study were: (1) to understand the water purification process of advanced and traditional water treatment plants, and to understand the concentration in AOC fluctuation in their water distribution networks; (2) to learn about differences in how the two water treatment plants remove AOC, and to know where is improvement ; (3) to use program analysis to produce a simple formula and AOC-related water quality parameters for the two water treatment plants, providing AOC control and management strategies in the future. The results concluded that the raw water of the two water treatment plants was primarily a hybrid of hydrophobic and hydrophilic molecules, and the highest values of AOC were found in winter. The CCLWTP had an overall removal rate of 54 %, and the GYWTP had an overall removal rate of 36 %. The CCLWTP conformed to the additions of an advanced water purification unit, but the water treatment process was relatively complex. Its AOC concentration varied considerably during the course of the water treatment process, while that of the GYWTP showed more stable measurements. The CCLWTP used coagulation precipitation, rapid filtration, and biological activated carbon filtration to effectively remove the AOC. The coagulation precipitation unit used by the GYWTP was most effective process in the removal of AOC and rapid filtering was less effective one. The treated water of CCLWTP maintained an AOC concentration under 51 £gg acetate-C/L in its water distribution network, while the treated water of GYWTP mostly kept a concentration of AOC lower than 71 £gg acetate-C/L. Although the CCLWTP water pipe network had lower AOC values, it demonstrated unstable changes in levels of AOC concentration. This shows that oxidation and disinfectants in the water treatment process cannot successfully oxidize all organic matter into AOC. In contrast, the GYWTP showed a more stable removal in AOC content. For the artificial neural network system simulation, the simulation values of CCLWTP water treatment process and water distribution network are correlated less closely with the measured actual value than those of the GYWTP do. This is found to be mostly due to the relatively large fluctuations in AOC in the CCLWTP. The AOC values in the CCLWTP water treatment process and water distribution network are highly correlated to TOC, TDS, and NH3-N. For the GYWTP, AOC values were mostly correlated to TOC, temperature, and NH3-N. Finally, the two common factors for water quality at both water plants were TOC and NH3-N, we recommend that these two items can be taken into consideration to control and manage AOC in water treatment.

Economical evaluation for the improvement strategy of drinking water quality by advanced water treatment in Greter Kaohsiung District

Cheng-Ching Lake water treatment plant (CCLWTP), the largest water treatment plant in southern Taiwan serving the Kaoping region, uses the Kaoping River water as the source water. The plant has encountered both technical and managerial challenges to implement advanced water treatment system since 2004 in order to provide high quality drinking water to the residents living in the Kaoping metropolitan area and to meet future stringent drinking water standards. Granular activated carbon (GAC), derived from wood, bituminous coal, lignite, or other carbon-containing materials, and is the most widely utilized adsorbent for treating water and wastewater. It is usually used after the sand filtration process in water or wastewater treatment plant; the exhausted GAC is re-activated by a combustion process. Moreover, biological activated carbon (BAC) filtration (biofiltration) has become one of the advanced treatment techniques applied in the water treatment plant. In general, BAC offers a large internal surface area for the adsorption of taste, odor, and color compounds, excess chlorine, toxic and mutagenic substances (e.g., bromide, chlorinated organic compounds, including trihalomethanes), trihalomethane precursors, pesticides, phenolic compounds, dyes, toxic metals, and substances that cause biological after growth. After the biofiltration process, a final disinfection is necessary to ensure the microbial quality of the treated water. Because biofiltration is usually not capable of removing biorefractory substances, pre-oxidation with ozone is usually applied for oxidizing the most biorefractory organic matters and also improving their biodegradability before the water is treated in the BAC process. Hence, using ozone pre-oxidation will greatly enhances the effectiveness of the subsequent BAC process. The CCLWTP effluent meets the current drinking water quality established by Taiwan Environmental Protection Administration (TEPA). However, the microbial regrowth due to the residual minute quantity of organic carbons causes pipe corrosion, and the formation of disinfectant by-products (DBPs) in the distribution system leading to potential contaminations of the clean water after it enters into the distribution system. Thus, monitoring the water quality in water distribution systems necessity to develop appropriate strategies for managing both the treatment plant and following distribution systems. Chlorine is often used in municipal water treatment plant for disinfecting drinking water; it can react with naturally occurring organic matter to form trihalomethanes (THMs), e.g. chloroform, bromodichloromethane, chlorodibromomethane and bromoform that causes long-term health hazards to consumers through oral ingestion, dermal absorption and inhalation. The lifetime cancer risk and the hazard index of THMs through oral ingestion, dermal absorption, and inhalation exposure from tap water in 9 districts in Kaohsiung City are estimated. In the first part of this study, water samples were periodically collected from each treatment process of Cheng-Ching Lake Water Treatment Plant (CCLWTP) to assess the AOC (assimilable organic carbon) removal. In the second part of this study, the role of BAC filtration used in advanced water treatment plant and its capability to remove pollutants (AOC, bromide, bromate, and iron) were evaluated. Additionally, the efficiency of biofiltration process using GAC and anthracite as the fillers was also assessed with a bench-scale GAC adsorption column. In third part of the study, the distribution system of CCLWTP was selected for conducting the case study for understanding the fate and transport of water quality indicators in the distribution system. The last part of the study concentrated on undertaking multipathway exposure assessment based on the concentrations of various THMs found in the water samples collected at various locations of Kaohsiung City water supply system. The AOC removal efficiency of the advanced water treatment processes of the CCL was assessed using data collected in the field during the first phase of this study. However, the effect of two different filling materials on the efficiency of biofiltration process was evaluated using a laboratory bench-scale column study. Results of both laboratory study and field investigation show that a significant AOC removal efficiency was achieved by the BAC system implemented in CCLWTP. Conclusions of this study are summarized as follows: 1. Significant AOC removal efficiency was achieved in CCLWTP and the AOC concentrations in the effluent could meet the current established standards. 2. The increased AOC concentrations after the treatment of preozonation and chlorination may be caused by the oxidation of organic matters to more biodegradable and assimilable products. 3. The removal of AOC is correlated with the decrease in concentrations of other drinking water indicators, e.g., coliform, TPC, TDS, and particle counts). 4. The addition of sodium thiosulfate in water samples could enhance the performance of the AOC analysis (the accuracy and reliability). 5. The BAC filtration has been demonstrated to play an important role in the removal of the trace AOC. Thus, the application of BAC for AOC removal is feasible and should be included as a required treatment unit in the advanced WTP. The field study completed in the second part assessed the removal efficiencies of AOC and other water quality indicators in CCLWTP, while the effects of using two different filling materials on the efficiency of biofiltration process and microorganisms growing were evaluated using a laboratory bench-scale column study. Conclusions of this study include the following: 1. The BAC filtration system is capable of removing trace pollutants including organics and metals. 2. Significant overall treatment efficiency can be achieved in the CCLWTP, and concentrations of the water quality indicators in the effluent will meet the drinking water standards established by TEPA. 3. The increased AOC concentrations after ozonation and chlorination processes may be caused by the oxidation of organic matters into more biodegradable and assimilable organic products. 4. GAC is a more appropriate filling material than anthracite in the biofiltration system for the removal of AOC. 5. More microorganisms were observed in GAC column than in BAF column. This may be due to the effect that GAC has more specific surface area than anthracite. Additionally, more microbial growth was observed at depth of 5 cm than 0 and 40 cm in both columns indicating that 5 cm below the column surface is rich in both dissolved oxygen and biodegradable that causes higher microbial populations. 6. The BAC filtration plays an important role in the removal of the trace AOC; it should be included as a required treatment unit in future advanced WTP. Additionally, the BAF filtration column filled with anthracite is not as effective as the GAC-filled column in removing AOC. Thus, GAC should be used for the proposed BAF filtration unit. 7. The oxidation process using ozone will increase the amount of carbonyl group organics in the oxidized water leading to poor biological stability. Therefore, the oxidation should be combined with a subsequent GAC or biological process to minimize the AOC formation potential. The third study, Using the oxidation/reduction potential (ORP) along with other water quality parameters to indicate the water quality in the CCLWTP distribution systems was assessed and focused. Behavior of water quality parameters by monitor and investigate was made a replacement of corrosive pipe line. The results reveal that the treated water leaving CCLWTP (clear water) meets the drinking water standards in Taiwan. However, the water is re-contaminated by a number of factors including the corrosion of old pipes while it is flowing in the distribution system. Major conclusions of this study are summarized in the following sections: 1. The free residual chlorine concentration in CCLWTP distribution system is adequate to meet the drinking water standards established by TEPA. 2. The residual AOC concentration is well correlated with the TOC concentration in the samples collected at various sites in different administrative areas. 3. Ratios of AOC/TOC in six administrative areas were higher than 9%, indicating that the biofilms were fall and increased organic matter of tap water distribution systems. 4. The average AOC concentrations were increased with followed variations of UV-254 value. 5. A number of factors (AOC, pH, redox potential, TOC, UV-254, and chlorine residual) control the growth of microorganisms on pipe surfaces. 6. DO have a negative relationship between THMs and HAAs concentrations. Because that oxygen have higher electronegative than chlorine and bromine, and apt utilization of organic carbon. 7. Results were shown of pH, DO and ORP had a positive relationship (Need to be more specific about the correlationship. 8. Major chemical reactions in the distribution system involve both electrons and protons transfers; they are pH- and Eh (ORP)-dependent. Therefore, chemical reactions in pipe net often can be characterized by pH and Eh together with the activity of dissolved chemical species. 9. The results reveal that the non-scaling water in LSI of distribution systems of CCL close to saturation (LSI = 0) (Cannot be understood). As show the other results, located K and M1 areas in LSI¡@were -0.002 and -0.012, respectively. The appearance of the pipe in K and M1 areas were corrosion and undersaturated with CaCO3 (needs to be re-written). 10. The RSI value was between 7.0 and 7.5 showing potential corrosion and prioritizes replacement of the pipe. 11. The DO value has a correlation with the reverse in Fe and Fe3+ concentrations. 12. High oxidation conditions and elevated Fe3+ concentrations of exist inside the corrosion scales of the corroded water distribution pipes. 13. The Fe concentrations in the samples collected in various administrative areas exceed the TEPA drinking water standards. 14. The appearance of CCL distribution system of shows severe corrosive and oxidized conditions. The last part of this study concentrated on evaluating the association between trihalomethanes (THMs) exposure through three different pathways and long-term health risks. The results show that the consumer has a higher risk of cancer through Inhalation route. This is different from the results reported by other research. Because most residents living in Taiwan are accustomed to drinking boiled water, the lifetime cancer risks through oral ingestion of water-borne CHBrCl2, and CHBr2Cl in tap water in all 9 districts were higher than 10-6. By oral ingestion the lifetime cancer risk for total THMs was highest in the 7th district, while the lowest lifetime cancer risk for total THMs was in the 4th district. Chloroform poses a higher cancer risk to Kaohsiung City residents through dermal exposure than the other three THMs. This study showed that residents in 7th district had the highest cancer risk through inhalation of chloroform among the 9 districts, and the residents in 6th district had the least cancer risk. Residents in 7th district has the highest risk of cancer due to exposure of THMs during showering and bathing as compared with residents in 4th district Males have a higher cancer risk than females through dermal absorption when exposed to THMs. The results of noncarcinogenic risk assessment for THMs indicate that if the main pathways are through oral ingestion and dermal absorption, 7th district has the highest hazard index of the four chemicals, while 4th district has the lowest hazard index. According to the above results, the quality of drinking water in Kaohsiung City is in general in accordance with the guidelines for drinking water quality as recommended by the World Health Organization. A better drinking water quality can be achieved by reducing the quantity of disinfection by-products (DBPs) through the removal of DBP precursors using modified treatment practices. Coagulation, granular activated carbon, membranes and ozone-biofiltration can all remove natural organic matter. Additionally, source water protection and control are effective non-treatment alternatives to control water-borne precursors. Optimized applications of disinfectants as primary and secondary disinfectants can further be implemented to control DBPs. Although research efforts continue to develop new treatment methods that will reduce the levels of DBPs during disinfection, it is generally accepted that risks to health caused by water-borne DBPs in drinking water are relative small in comparison with risks associated with water-borne diseases due to inadequate disinfection. Thus, it is important that the disinfection process should not be compromised in attempting to control water borne DBPs. The predominant DBPs group has been shown to be THMs, with chloroform and BDCM as the most dominant THMs. Although THMs are only one subgroup of the many DBPs formed during chlorination, they are useful as indicators of the overall DBP formation. It is concluded that, given the current state of knowledge, a risk assessment based on THMs would provide the greatest level of confidence regarding the ability of a drinking water guideline to protect against risks of cancer and other long-term health hazards. In conclusion, in order to reduce the cancer risk and hazard as indexed by THM concentrations in the drinking water, some methods could be used including controlling to reduce THMs precursors and microbial contaminants in raw water, and aged pipeline, optimizing all treatment processes to ensure that concentrations of disinfectant are adequate, using alternative disinfectants and reducing water age in distribution system. The potential human risks associated with drinking water disinfection are largely unknown, even though some information is available from toxicological and epidemiological studies. More research is needed to determine the risks associated with DBPs. The next progress will facilitate a more realistic assessment of risk due to drinking water contaminants without increasing the levels of uncertainty in risk estimates.

One of the most toxic environmentally mobile compounds found in water is arsenic. It has been used as a pesticide to control insects, fungi, weeds and rodents since the early part of this century because of its high toxicity. Sorption of toxic metals onto a metal oxy-hydroxide is the most popular and practical arsenic removal method from contaminated water. Water treatment with oxy-hydroxides creates arsenic containing residuals, which are usually disposed of in landfills. To prevent leaching, stabilization of the solid residuals is required. It has been reported that calcium may inhibit arsenic desorption and/or benefit arsenic sorption. The objective of this investigation is to assess arsenic leaching in the presence of calcium and phosphate ions at extreme pH. Two hypotheses have been identified to explain the decrease in soluble arsenic in the presence of calcium. One explanation is that arsenic reacts with calcium to form calcium arsenic solids. The second hypothesis is that calcium affects the surface properties of the oxy-hydroxide solid in solution. Results show that calcium enhances the removal by iron oxides and prevents the leaching of arsenic from the residuals. Isotherm experiments show that arsenic adsorption can be described as occurring on nonporous powders or powders with pore diameters larger than micro-pores. Physically, with increase in adsorbate concentration, second and more layers are completed until saturation when the numbers of adsorbed layers becomes infinite. Further, experimental data were fitted to a Brunauer, Emmett and Teller isotherm (BET) model which assumes the initial layer can act as substrate for further adsorption. Finally, calcium-arsenic and calcium-phosphate solids were predicted to be formed by Visual MINTEQ modeling program. Nevertheless, from the x-ray diffraction output calcium-arsenic or calcium-phosphate solids were not identified. Because no calcium arsenate solids were found it was concluded that calcium affects the surface properties of the oxy-hydroxide solids in solution. Increasing the pH produces negative surface charge, which in turn increases repulsion between the negatively charged hydrated arsenate ions and the Fe(OH)3 surface. Calcium’s positive charge might neutralize this effect enhancing the sorption of arsenic onto the oxy-hydroxide. Also, it was concluded that the competition between arsenic and phosphate was reduced by the same mechanisms.

During the water treatment process, each processing unit releases the sludge from the sedimentation process, and the wastewater from the rapid sand wash and filtration process, to the wastewater pond followed by the wastewater sedimentation pond. The sediment sludge is allowed to enter the sludge thickening pond while the supernatant is recycled for further treatment. The sludge is released to the sludge pond where it is treated with certain chemicals and squeezed to form the sludge cake. The sludge cake is removed and transported by a legitimate cleaning service company to an authorized location. The present study is focused on the investigation of the feasibility of recycling the wastewater and the dewatering of the sludge from the water treatment plant. The analysis of the samples collected from the wastewater treatment plant showed that the recycled supernatant had a pH of 7.16~8.21, a conductivity of 371.1~769.1 £gmho/cm, a total dissolved solid (TDS) of 193.3~399.9 mg/L, and a turbidity of 0.901~54.3 NTU. The suspended solids (SS) of the recycled supernatant was found to be 0.4~45.6 mg/L, lower than the standard value in the Effluent Standards (50 mg/L). The ammonia nitrogen (NH3-N) and the Total Organic Carbon (TOC) of the recycled supernatant were found to be 0.06~1.5 mg/L and 1.533~17.437 mg/L, respectively. The analysis of the Chemical Oxygen Demand (COD) of the wastewater treatment plant showed a concentration of 12.1~128.5 mg/L in the sample of the recycled supernatant. The COD in the Effluent Standards is required to be no more than 100 mg/L. For sludge conditioning and dewatering, a sludge conditioning experiment was conducted in the laboratory to plot the curve of the experimental result. The curve was used for the actual sludge conditioning and dewatering in the Fongshan Water Treatment Plant to verify the feasibility of the application for the actual process in the water treatment plant.

N-Nitrosodimethylamine (commonly known as NDMA) is a probable human carcinogen that has been recognized as an emerging drinking water contaminant in recent years. Previous studies have shown that certain N-containing organic compounds may form NDMA in reaction with chlorine or monochloramine and the NDMA yield is affected by the structure of the organic-N compounds, water conditions and treatment parameters. Many amine-based water treatment polymers contain organic-N functional groups and thus have been suspected as potential NDMA precursors in water treatment systems. The purpose of this research was to systematically assess the potential NDMA formation from different structural types of water treatment polymers in reactions with various oxidants and probe the possible factors that influence the NDMA formation. Robust analytical methods for detection of NDMA and the well-known NDMA precursor dimethylamine (DMA) in the reaction samples were established. The cationic polyacrylamide (cationic PAMS), aminomethylated polyacrylamide (Mannich), poly-diallyldimethylammonium chloride (polyDADMAC) and polyamine polymers were evaluated in reactions with nitrite, free chlorine, monochloramine or chlorine dioxide in aqueous solutions at circumneutral pH and room temperature conditions. This study employed high dosages of polymer and oxidant and long reaction time in order to assess the maximum potential to form NDMA. A range of operational parameters that may affect the above reactions were also evaluated.

<p>Equilibrium isotherms and the adsorption kinetics of heavy metals onto chitosan were studied experimentally. Chitosan, a biopolymer produced from crustacean shells, has applications in various areas, particularly in drinking water and wastewater treatment due to its ability to remove metallic ions from solutions. The adsorption capacity of chitosan depends on a number of parameters: deacetylation degree, molecular weight, particle size and crystallinity. The purpose of this work was to study the adsorption of copper, zinc, mercury, and arsenic on chitosan produced from shrimp shells at a laboratory level.</p><p>The experimental work involved the determination of the adsorption isotherms for each metallic ion in a batch system. The resulting isotherms were fitted using the Langmuir model and the parameters of the equation were determined. Kinetic studies of adsorption for different metallic ions at different concentrations and with different particle sizes were performed in batch and column systems. Simplified models such as pseudo-first-order, pseudo-second-order, and intra-particle diffusion equations were used to determine the rate-controlling step. Some preliminary studies were carried out to address the application of chitosan as an adsorbent in the removal of heavy metals or other metallic ions from natural water and wastewater. The regeneration of chitosan was also studied.</p><p>The results showed that the adsorption capacity depends strongly on pH and on the species of metallic ions in the solution. The optimum pH value for the metallic cation adsorption was between 4 and 6, whereas for arsenic adsorption it was about 3. When the pH is not controlled, the adsorption capacity is independent of the initial pH with the solution reaching a final pH of about 7. It was also found that the Langmuir equation described very well the experimental adsorption data for each metallic ion. The adsorption capacity for the metals on chitosan follows the sequence Hg>Cu>Zn>As.</p><p>The study of the adsorption kinetics of these metallic ions shows that the particle size has a significant influence on the metal uptake rate for copper; but that it has only a slight influence on the adsorption rate of zinc and mercury in the range studied. Arsenic adsorption exhibited an interesting behaviour which depends strongly on the pH of the solution; the uptake increased at short adsorption times and then decreased at long times. The analysis of kinetic models showed that the pseudo-second-order adsorption mechanism is predominant, and the overall rate of the metallic ion adsorption process is therefore controlled by adsorption reactions and not by mass transfer for the range of particle sizes examined in this study.</p><p>With regard to the regeneration of chitosan, it was found that sodium hydroxide is a good agent for zinc and arsenic desorption, whereas ammonium sulphate and sodium chloride were the most suitable for copper and mercury desorption, respectively. The ability of chitosan to remove arsenic from natural water, and copper and zinc from mining waste water was verified. The use of these results for designing purposes is a subject for future work.</p>

Hydrogen sulfide imparts odors and taste to drinking water and can be corrosive to distribution systems. Groundwater sources used to produce drinking water tend to have sulfide concentrations ranging from below 0.1 to over 3 mg/L. Under anaerobic conditions, hydrogen sulfide can be formed from reduction of sulfate and elemental sulfur through chemical or biological reactions. Therefore, to decrease the potential for hydrogen sulfide in water systems, control of all forms of sulfur should be consistent. Hydrogen sulfide in groundwater can be controlled through conversion or removal mechanisms. Conversion reactions result from chemical or biological reactions that oxidize hydrogen sulfide to elemental sulfur or sulfate, depending on the reaction conditions. Removal reactions include stripping, anion exchange, or formation of a precipitate that can be removed through solid/liquid separation processes. In many groundwater treatment systems, hydrogen sulfide is controlled through aeration, chlorine oxidation, or a combination of these two methods. In addition to chlorine, other oxidizers can be used including hydrogen peroxide, UV, ozone, or potassium permanganate. The main factors that influence whether hydrogen sulfide is oxidized to elemental sulfur and/ or sulfate are pH, temperature, and the type and dose of oxidant. In recent years alternative treatments technologies such as anion exchange, have become available. It is interesting to note that this technology was proposed as early as the middle of last century. Although large scale anion exchange has not been implemented, its application for the removal of hydrogen sulfide is feasible based on anion exchange principles. This research was designed to evaluate feasible options for controlling hydrogen sulfide from groundwater sources. The feasibility of using anion exchange was investigated through pilot-scale testing of four groundwater sources. In addition, the performance of typical and alternative chemical oxidizers to control hydrogen sulfide was evaluated.