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A review of the literature published in 2008 on topics relating to water reclamation and reuse is presented. This review is divided into the following sections: (1) General: extent of reuse, research needs, guidelines and monitoring, and health effects, (2) Treatment Technologies: integrated process design, electrodialysis/electrodeionization, membrane treatment, chemical recovery for industrial wastewaters, disinfection, and (3) Planning and Management: public acceptance & education, economics and pricing, water quality planning and management and project/case studies.

The goal of this research was to remove arsenic from groundwater supplies via adsorption into media obtained from waste material generated as by-products from glass recycling programs and the seafood industry such as crushed glass and scallop shells. During the course of this research four new adsorbents were developed: ferric hydroxide coated crushed glass (FHCCG); ferric oxide coated crushed glass (FOCCG); ferric hydroxide coated scallop shells (FHCSS); and ferric oxide coated scallop shells (FOCSS). The adsorbents were characterized through evaluation of their structure, surface area, chemical composition, iron content, and coating stability. Efficiency of the adsorbents to remove arsenic from water was examined through batch kinetic and isotherm adsorption experiments. The adsorption capacity of the adsorbents was also evaluated by performing column experiments using real ground waters and a synthetic water. Arsenic removal to a concentration less than 10 μg/L was achieved with the FHCSS and more than 9000 bed volumes of water were treated before the breakthrough point was reached. The research results revealed that scallop shells coated with ferric hydroxideperformed better than crushed glass coated with ferric hydroxide. Both FOCCG and FOCSS had poor arsenic removal compared with FHCSS and granular ferric hydroxide (GFH). Ferric hydroxide coated scallop shells performed similarly to GFH.

The purpose of this study was to carry out an acute aquatic toxicity assessment on select effluent samples from Atlantic Canadian seafood processing plants. Raw effluent acute aquatic toxicity for the flatfish and salmon effluents was assessed using the acute lethality test and Microtox test. The effectiveness of dissolved air flotation treatment (DAF) in removing acute toxicity from these effluents was evaluated using the Microtox test. The salmon effluent failed the acute lethality test using rainbow trout while the flatfish effluent showed acute toxicity in the Microtox test with a 50% inhibiting concentration (IC(50)) of 38.84%. Subsequent treatment by DAF of the flatfish and salmon effluents increased IC(50) values by 20% and 26% respectively. The findings of this study indicate that all of the processing effluents sampled showed characteristics that could potentially degrade effluent receiving waters and acute toxicity was demonstrated in the two raw finfish effluents. Application of DAF treatment was successful in significantly increasing Microtox IC(50) values, thereby reducing acute toxicity, but failed to entirely remove acute toxicity.

The treatment and disposal of water treatment plant residual solids has become an increasingly important environmental priority for drinking water utilities. This study examines water treatment residual solids (WTRSs) from four North American water treatment plants to determine the role that coagulant types play in phosphate adsorption by the residual solids. In total, two alum residual solids (one solid from a plant that has a raw water with low alkalinity and one solid from a plant that has a raw water with high alkalinity), one lime residual solid and one ferric residual solid were used in batch adsorption experiments with deionized water at a pH of 6.2±0.2 and secondary municipal wastewater effluent at a pH of 6.8. Langmuir isotherm modeling showed that ferric residuals had the highest adsorptive capacity for phosphate ( Q max =2,960 mg/kg), followed by lime ( Q max =1,390 mg/kg) and alum ( Q max =1,110 mg/kg and 1,030 mg/kg) for adsorption experiments with P-spiked deionized water. Of the two alum residuals, the residual with a higher weight percent of metal oxides had a higher adsorptive capacity. The ferric residuals were less affected by competing species in the wastewater effluent, while the lime and alum residuals had a higher rate of phosphate removal from the deionized water compared to the wastewater effluent. Overall, ferric water treatment residuals were the best adsorbent for phosphate adsorption, followed by lime and alum residuals.

This paper presented a simplified ecological risk assessment of the toxicity of alum residuals from water treatment plants to surface water that is based on the framework recommended by United States Environmental Protection Agency (USEPA). Though few studies have investigated the potential for increased aluminum toxicity with discharge of alum residual streams to the aquatic environment, none have explored the use of ecological risk assessment methodologies to gain additional insight into the potential risk. This systematic approach has been used to elucidate the process of aluminum toxicity from oven-dried alum residuals on aquatic habitats. A laboratory experiment was performed to assess the leaching of dried alum residuals to five lake water samples. The tests were also done to evaluate the effect of pH levels (4, 5.5, and 7) and drying mechanism of alum residual (oven, air or freeze–thaw). Total inorganic aluminum leaching from laboratory analysis was used along with toxicity reference values to determine a risk quotient (RQ) for assessment of risk. Results revealed that alum residuals in surface water could reduce aluminum concentration or potential risk (RQ) for fish in some lake waters at natural pH levels. Surface water pH and drying mechanism of alum residuals did not have considerable effect on leachability of aluminum. Lake waters with and without the addition of alum residual showed a potential risk for chronic sub-lethal toxicity for trout species. Both chronic and acute lethal toxicity was observed in some tests depending on the initial aluminum concentrations in the lake water. A detailed review of toxicological effects of aluminum, its exposure and bioaccumulation was studied for appropriate risk assessment.

Treatment systems that utilize natural processes, such as constructed wetlands, offer a sustainable and economical alternative to conventional wastewater treatment. Dairy farm wastewater was loaded into two similar (~100 m2 each) surface flow treatment wetlands in Bible Hill, Nova Scotia, Canada, at an average rate of 65 kg BOD5 ha-1 d-1. A diffused air aeration system was installed in one of the wetlands based on a design oxygen requirement of 3.52 kg O2 d-1. Wetland treatment performance was evaluated over 20 months (September 2002 to April 2004), during which time the aeration system operated for 13 months. The wetlands were monitored intensively for dissolved oxygen (DO), five-day biochemical oxygen demand (BOD5), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), ammonia-nitrogen (NH3-N), nitrate-nitrogen (NO3--N), total phosphorus (TP), and Escherichia coli. Both the aerated and non-aerated wetlands provided effective year-round wastewater treatment. Artificial aeration significantly increased TKN and NH3-N mass reductions (P < 0.001). Aeration did not significantly affect the removal of BOD5, TSS, NO3--N, TP, and E. coli. The data suggest that the benefits of wetland aeration are not great enough to warrant its widespread adoption for small-scale agricultural systems.

As biological manganese (Mn) removal becomes a more popular water treatment technology, there is still a large gap in understanding the key mechanisms and range of operational characteristics. This research aimed to expand on previous bench-scale experiments by directly comparing small filtration columns inoculated with indigenous biofilms from a Mn filtration plant and filtration columns inoculated with a liquid suspension of Leptothrix discophora SP-6. Batch tests found that in the absence of manganese oxidizing bacteria Mn was not removed by air alone, whereas a mixed population and Leptothrix strain achieved greater than 90% removal of Mn. The bench-scale biofiltration experiments found that biological filters can be inoculated with a pure culture of L. discophora SP-6 and achieve a similar removal of indigenous biofilm. While Mn oxidizing bacteria (MOB) seem to be necessary for the auto-catalytic nature of these biological filters, Mn removal is achieved with a combination of adsorption to Mn oxides and biological oxidation. Additionally, it was demonstrated that biological Mn removal is possible over a broader "field of activity" (e.g., Mn removal occurred at a pH level as low as 6.5) than has previously been reported. The ability of this treatment technology to work over a broader range of influent conditions allows for more communities to consider biological treatment as an option to remove Mn from their drinking water.

Disinfection efficacy was evaluated in four pilot-scale systems that were operated at four water utilities across North America. Through this approach, factors which are difficult to simulate in a laboratory environment (such as water properties, process conditions, climatic conditions) were assessed, in order to determine their influence on disinfectant effectiveness. The results from this study show that a critical level of disinfectant residual ( C crit) was necessary for inhibiting heterotrophic bacterial growth to less than 500 CFUml−1 in the effluent of these pilot-scale systems. When free chlorine was the disinfectant, this critical residual concentration was found to be approximately 0.6 mg L−1. A total chlorine concentration of 1 mg L−1 resulted in low bacterial counts with chloramine disinfectants, though approximately 10–20% of this residual was found to be comprised of slowly degradable organic chloramines which are less effective as disinfectants. A higher ductile iron pipe corrosion rate was observed with a free chlorine disinfectant as compared with chloramines. The results from this study are likely to be of interest to water utilities responsible for the operation and optimization of drinking water distribution systems.

Biological treatment of drinking water to remove manganese (Mn) is becoming more and more common. However, details as to how the technology works remain poorly understood. Some previous studies have focused on bacteria of the genus Leptothrix , identifying them as one of the predominant organisms in Mn oxidizing biofilms. This research took media from inside the filters of four Mn biofiltration plants in the province of New Brunswick, Canada. The water was characterized for all four sites and it was found that Mn removal from all plants is virtually 100%. Biofilm was detached from the sand and tested for presence of Leptothrix using real-tme polymerase chain reaction (RT-PCR) DNA amplification. Less specific testing for Mn oxidizing bacteria was done simultaneously using indicative agar plates. Results showed that only one plant contained Leptothrix in its filters while three of the four plants tested positive for manganese oxidizing bacteria (MOB) through plating. These results, along with other evidence, suggest that while the mechanism of oxidation observed is likely biological, Leptothrix is not necessarily the predominant organism carrying out biooxidation.

The effect of chlorine dioxide ( ClO2 ) pretreatment on subsequent treatment processes (coagulation, flocculation, sedimentation, filtration, and ozonation) was studied at pilot-scale at the Upper San Leandro Water Treatment Plant near Oakland, Calif. Potential impacts of ClO2 on the distribution system were also studied at bench scale using simulated distribution system (SDS) tests. Pilot trials were conducted with one train operating without ClO2 pretreatment (Train 1) and the other with a ClO2 dose of between 0.6 and 1.0 mg∕L (Train 2). Comparison between Trains 1 and 2 showed that ClO2 pretreatment resulted in a 0.1–0.2 NTU decrease in settled water turbidity when compared to no pretreatment. ClO2 pretreatment also resulted in a small (0.01 cm−1 ) decrease in ultraviolet absorbance at 254 nm . Following sedimentation, about 60% of the applied ClO2 formed chlorite ( ClO2− ) , with 10–20% forming chlorate ( ClO3− ) . Ozonation immediately converted all residual ClO2 and ClO2− to ClO3− . There was no sig...

The overall objective of this study was to investigate the impact of blending membrane-treated water treatment plant (WTP) residuals with plant-filtered water on finished water quality in terms of biostability and disinfectant by-product (DBP) formation. Filter backwash water (FBWW) was treated with a pilot-scale ultrafiltration (UF) membrane to produce permeate that was blended with plant-finished water. The batch studies involved storing samples for a specified time with a disinfectant residual to simulate residence time in the distribution system. Both chlorinated and non-chlorinated FBWW streams were evaluated, and the experimental design incorporated free chlorine, monochloramine, and chlorine dioxide in parallel to a model system that did not receive a disinfectant dose. The results of the study found that blending 10% UF-treated FBWW with plant-filtered water did not have an impact on water biostability as monitored with heterotrophic plate counts (HPCs) or DBP concentrations as monitored by TTHM and HAA5 concentrations. However, the presence of preformed THM and HAA species found in chlorinated FBWW streams may result in higher levels of initial DBP concentrations in blended water matrices, and could have a significant impact on finished water quality in terms of meeting specific DBP guidelines or regulations.

In a field study conducted previously in Pinellas County, Florida, implementing Uv treatment following chemical disinfection hindered control of HPC bacteria and resulted in higher counts in most samples. It was believed that free chlorine and monochloramine were either decaying in the presence of UV light or that they were absorbing uv irradiation. These occurrences would both lead to a decrease in available disinfection and in turn lead to increased bacteria counts. A bench-scale study was conducted to further investigate interactions between uv light and chemical residuals in drinking water. Three separate water sources (surface water, blended water and deionized water) were treated with chlorine, monochloramine or chlorine dioxide at different concentrations, then exposed to low-pressure UV light. It was confirmed that chemical disinfectants decay when samples are exposed to UV light. Specifically, for deionized water free chlorine was lowered to approximately 95% of initial concentration following UV treatment. In contrast, free chlorine was decreased to 89% and 84%, on average, in the tested groundwater and surface water, respectively. A similar range in decreased disinfectant concentration was also observed for chlorine dioxide and chloramines. However, no significant absorption of Uv irradiation by chemical disinfectants was observed. These results provide greater insight into the confounding effects between chlorine-based disinfectants and UV light, which may be important for utilities or institutions that are considering Uv treatment of previously disinfected water.

The goal of this study was to compare disinfection strategies for controlling microbial growth in distribution systems from a blended water source in a warm climate. This research compared the efficacy of chlorine (Cl 2 ) to monochloramine (NH 2 Cl) with and without post-treatment with ultraviolet (UV) light for heterotrophic bacteria control. Two influent streams were pre-treated with either chlorine or monochloramine, and consisted of a blend of groundwater, surface water and desalinated water. Annular reactors (ARS) containing coupons made of PVC material were used to simulate common operating conditions in a distribution system. Two ARs acted as controls and received the chlorinated water or water treated with monochloramine. The remaining two ARs received water that was additionally treated with UV light. The data presented show that treatment with Cl 2 alone was the most effective disinfection strategy against suspended heterotrophic (HPC) bacteria in influent and effluent samples and also against attached HPC bacteria. Chlorine with or without post-UV treatment was more effective than monochloramine at removing suspended and attached HPC bacteria. Levels of free chlorine concentration were reduced following treatment with UV light, which resulted in the increased bacteria counts in the AR. UV treatment also appeared to enable nitrification in the AR treated with NH 2 Cl, as ammonia was completely converted to nitrate in the NH 2 Cl/Uv-treated AR whereas concentrations less than 0.2 mg l -1 of nitrate or nitrite were detectable in the NH 2 Cl-treated AR.

Ultraviolet light is increasing in popularity as a primary disinfectant in drinking water treatment because of its effectiveness against chlorine-resistant pathogens and lack of disinfection by-product (DBP) formation. Previous bench-scale studies have shown that there are possibly synergistic benefits in reducing heterotrophic bacteria when ultraviolet (UV) light is coupled with chlorine (Cl2) or monochloramine (NH2Cl). Additional experiments have demonstrated that synergy exists between various disinfectants in controlling numerous bacteria, viruses, and protozoan. Few studies, to date, have specifically investigated synergy with UV in combination with chlorine-based drinking water disinfectants including chlorine dioxide (ClO2), Cl2, and NH2Cl. This preliminary study looked at the effectiveness of seven disinfection strategies (UV, Cl2, ClO2, NH2Cl, UV/Cl2, UV/ClO2, and UV/NH2Cl) against Escherichia coli in a single-species system at various combinations of disinfectant dose and contact time. Spiked solutions containing E. coli were treated by UV alone, chemical disinfectant alone, or UV coupled with chemical disinfectant. It was found that the combined disinfection strategies achieved the highest removal. Data were additionally analyzed for synergistic benefits, and each combination had a positive result. Results suggest that drinking water utilities may see enhanced removal of bacteria and potentially other pathogens due to synergistic benefits when UV was used in combination with any chlorine-based disinfectant. However, more data are required to conclusively determine synergistic relationship(s) between UV light and chlorine-based disinfectants.

In North America, the rapid movement away from the direct discharge of water treatment plant (WTP) residual streams to receiving environments has resulted in considerable benefits to the drinking water industry in terms of enhancing environmental stewardship practices and supporting source water protection strategies. Over the past 20 years, application based research on appropriate technologies to treat residual streams such as filter backwash water (FBWW) has promoted the development of integrated process design that presents recycling as a viable residual management option. However, as utilities continue to develop and expand their main process lines to comply with more stringent government regulations encompassing both water quality and residual disposal practices, the development of sustainable residual management practices is expected to become a more prominent issue for this industry. The purpose of this paper is to present, from a critical point of view, the matrix of issues that currently exist regarding WTP residual streams and strategic pathways that would enhance future decision making processes for achieving long-term residual management solutions for the drinking water industry.

In this study, fixed bed columns were used to evaluate the effectiveness of phosphorus adsorption on oven dried alum residual solids. The effect of key operating parameters (pH, particle size, and initial phosphorus concentration) on the effectiveness of phosphorus removal was investigated. The results indicated that phosphorus removal using oven dried alum residual solids was effective and comparable to granular activated carbon. Statistical analysis showed that the effect of particle size on the breakthrough pore volume processed was significant, but the effect of pH was inconclusive. Aluminum leaching was found to be higher than 20 mg/L for an influent pH level of 3. The effectiveness of phosphorus removal was affected by initial phosphorus concentration. However, initial phosphorus concentration did not appear to have any considerable effect on aluminum and organic leaching.

This study aims to investigate the effectiveness of alum residuals generated during drinking water treatment for adsorption of phosphorus from secondary municipal effluent. Bench-scale experiments (batch and fixed bed column tests) were conducted using oven-dried alum residuals. Experimental results observed maximum phosphorus removal of 91%-98% using alum residual concentrations of 4 g/L to 16 g/L. Oven-dried alum residual was a more effective adsorbent for orthophosphate phosphorus than total phosphorus. Effluent pH levels were suitable for surface water disposal with little or no lime addition. Aluminum leaching from oven-dried alum residual was not high enough to cause toxicity for aquatic species in surface water. Oven-dried alum residuals were also able to adsorb organic matter. The results indicated that oven-dried alum residuals have potential to provide a low cost technological solution for small- and medium-sized municipalities.

Water treatment plants produce significant amounts of aluminium-rich residual solids (i.e. sludge) as a result of various processes to treat raw source water. Monofilling of these alum-based residual solids or other alum-rich sludge or leachates can be performed cost-effectively with geosynthetic clay liners (GCLs). However, there is currently a paucity of literature related to aluminium migration through GCLs and the influence of this aluminium migration on the engineering behaviour of GCLs. This paper presents results of GCL hydraulic conductivity, diffusion, and batch testing performed with aluminium sulfate solutions. Hydraulic conductivity test results show that modest increases in hydraulic conductivity with the aluminium solutions are observed after hydration with distilled water (k < 5 × 10−11 m/s). Diffusion testing with the same GCL has established an aluminium diffusion coefficient, Dt, of 1.5 × 10−10 m2/s and a linear distribution coefficient, Kd, of 30 ml/g. Batch testing performed confirms an initial high rate of aluminium uptake to the sodium bentonite, as well as non-linear behaviour. Adsorbed cation distributions on the bentonite and differential thermal analysis after 22 pore volumes of permeation with the aluminium solutions suggest that cation exchange and precipitation are mechanisms responsible for the attenuation observed as well as changes in hydraulic conductivity. An illustrative example is provided in the text to provide some perspective on the possible use of results presented herein for alum residual monofills.

Aquaculture process waters are often scrutinized for loading phosphorus discharges into surface water. With the growing regulatory control of discharge from aquaculture process industries, it has become very important to address low cost and effective technological solution for aquaculture facilities. This study aims to investigate the effectiveness of alum residuals, which were generated during drinking water treatment for adsorption of phosphorus from aquaculture process water. Alum residuals were dried using an oven at 105 °C for 24 h. Particle size ( d 60 ) was similar to conventional adsorbent, granular activated carbon. Bench scale experiments (batch and fixed bed column tests) were conducted using oven dried alum residuals. Fixed bed column tests also looked at the effect of influent pH on the effectiveness of oven dried alum residuals. Experimental results observed phosphorus removal of 94–99% using an alum residuals concentration of 4–16 g/L. Freundlich adsorption isotherm was effective in explaining partitioning among solid and liquid phases. Oven dried alum residuals were a better adsorbent for orthophosphate phosphorus than total phosphorus. Effluent pH levels for both batch and fixed bed column tests were within range of 6–9 for most of the samples tested and therefore, suitable for surface water disposal. There were no effects of pH observed on the breakthrough pore volume processed during fixed bed column test. There was aluminum leaching from oven dried alum residuals, however, not high enough to cause toxicity for aquatic species if disposed in surface water. Oven dried alum residuals were also able to adsorb organic matter from aquaculture process water. The effluent BOD 5 was below 30 mg/L for most of the samples with an exception of a few samples where BOD 5 was beyond the limit for surface water disposal guidelines. The results indicated that oven dried alum residuals have potential to provide a technological solution for small aquaculture facilities.

Low cost and effective phosphorus adsorbents are required for the treatment of small or decentralized wastewater systems. The goal of this study was to examine phosphorus adsorption on different low-cost media. Bone char and oven dried alum sludge had the highest Freundlich adsorption constants (Kd) of 1.031 and 0.484, respectively. Maximum adsorption density from the Langmuir isotherm plot was 0.674 mg P g–1 for oven dried alum sludge and 1.787 for air dried alum sludge. pH levels at equilibrium were close to 7 for various dried alum sludge. Experiments conducted at 16 g/L of adsorbent on secondary municipal wastewater showed that all types of dried alum sludge and bone char were the most effective adsorbents of phosphorus. pH levels for oven and air dried sludge were in the range of 6.5–7, whereas the blast furnace slag and cement kiln dust exceeded a pH of 9. Consequently further work was recommended for water plant residuals.Key words: phosphorus, adsorption, Freundlich, Langmuir, alum residual.

This study evaluates the synergistic effects of ultraviolet (UV) and secondary disinfectants on water quality in a model distribution system. Chemical disinfectants evaluated for residual disinfection include chlorine dioxide, monochloramine, and free chlorine. Results suggest that there may be synergistic effects between UV and the chemical disinfectants for controlling microbiological re-growth in drinking water distribution systems. UV disinfection appeared to increase the vulnerability of bacteria located in suspension or within biofilms to chemical disinfection, although only at low disinfectant residual concentrations of 0.25, 0.50, and 1.0 mg/L for chlorine dioxide, free chlorine, and monochloramines, respectively. At high disinfectant residual concentrations of 0.50, 1.0, and 2.0 mg/L for chlorine dioxide, free chlorine, and monochloramines, respectively, results indicated that chemical disinfection alone would be adequate for microbial control. In the reactors receiving UV pre-treatment, both chlorine dioxide and free chlorine disinfection were far more effective in reducing the growth of suspended heterotrophic bacteria than without UV pre-treatment. Similar biofilm and suspended bacterial levels were observed without subsequent chemical disinfection regardless of the presence or absence of UV treatment. Overall, these findings imply that UV treatment prior to chemical disinfection enhances microbial control in distribution systems. These results indicate the use of UV pre-treatment can be effective at reducing the disinfectant concentration necessary for microbial control, therefore reducing the potential for the formation of disinfectant by-product in the system.Key words: drinking water, UV pre-treatment, chlorine dioxide, chlorine, monochloramines, disinfection.

The objective of this paper was to assess the effects of secondary disinfectants on internal corrosion and water quality in copper piping under stagnant conditions. In particular, this study evaluated the effects of free chlorine, monochloramine, chlorine dioxide, and no disinfectant as a control on copper release under a range of corrosion inhibition conditions. Corrosion inhibition factors that were considered include pH and alkalinity. Each of the corrosion factors and each chemical disinfectant was varied at two levels e.g., high and low concentration to create a 2 3 factorial design for each chemical disinfectant. The water in the copper pipes was sampled and replaced after a 72 h stagnation period. Results show a decrease in copper release for all disinfectants used as compared to the control. In particular, the highest copper concentration measured was 2.55 mg/L, which corresponded to a pH of 7.2 and alkalinity of 100 mg/L and no chemical disinfectants. The lowest total copper concentration was 0.29 mg/L, which corresponded to the high pH and low alkalinity for the high dose of chlorine.

Rapid-mixing tanks with mechanical mixers are a common design used in treatment plants. Yet, the role of such rapid-mixing systems on the effectiveness of the coagulation performance is unclear. This study looked at optimizing the direct energy used in the coagulation process for removal of natural dissolved organic matter (DOM). The role of coagulation mixing intensity (G-value) on total organic carbon (TOC) and turbidity removal was examined for the water types with high organic content, with a specific ultraviolet absorbance (SUVA) of at least 2-2.5 units of m(-1) of absorbance per mg/L. A standard jar test using ferric sulfate coagulant was performed to optimize the chemical condition in coagulation for removal of dissolved organics as well as particles. The jar test analysis at an acidic pH (4.5 ± 0.3) required an iron dose

Bench-scale experiments investigated the role of iron and aluminum residuals in lead release in a low alkalinity and high (> 0.5) chloride-to-sulfate mass ratio (CSMR) in water. Lead leaching was examined for two lead-bearing plumbing materials, including harvested lead pipe and new lead: tin solder, after exposure to water with simulated aluminum sulfate, polyaluminum chloride and ferric sulfate coagulation treatments with 1-25-μM levels of iron or aluminum residuals in the water. The release of lead from systems with harvested lead pipe was highly correlated with levels of residual aluminum or iron present in samples (R2 = 0.66–0.88), consistent with sorption of lead onto the aluminum and iron hydroxides during stagnation. The results indicate that aluminum and iron coagulant residuals, at levels complying with recommended guidelines, can sometimes play a significant role in lead mobilization from premise plumbing.

North American drinking water utilities are currently re-evaluating their disinfection strategies for controlling microbiological growth in distribution systems. Most water systems in North America use free chlorine as a secondary disinfectant. Since chlorine is known to form potentially carcinogenic byproducts in drinking water, utilities are looking for an alternative to maintain a disinfectant residual in the distribution system. The objective of this study was to evaluate the response of model drinking water distribution systems to a change in disinfectant from either free chlorine or chloramines to chlorine dioxide, in terms of its impact on microbiological water quality (bulk water and biofilm). Switching from a chlorine residual of 0.5 mg/L to a chlorine dioxide residual of 0.25 mg/L did not impact (negatively or positively) microbial water quality as quantified by heterotrophic and total cell counts (sample size = 8 data points). Thus, on the basis of the mass of disinfectant applied, chlorine dioxide was more efficient than free chlorine at controlling microbiological growth in the model distribution system. Similarly, chlorine dioxide was more efficient than chloramines, as a chlorine dioxide residual of 0.25 mg/L inactivated 0.75–1 log more suspended organisms than 1.0 mg/L residual of chloramines. Therefore, under the tested conditions, chlorine showed similar or better disinfection efficiency than free chlorine and chloramines, respectively.

Recirculating biofilters (RBFs) were studied as an option for treating domestic wastewater. In particular, the objective of this investigation was to examine the hydraulic (hydraulic loading rates or HLRs), operational (dosing frequency and recycle ratio), and media characteristics that significantly impact treatment performance. Four types of filter media were examined in this study: sand, crushed glass, peat, and geotextiles. Laboratory controlled experiments demonstrated that dosing frequency impacted treatment performance significantly. A dosing frequency of 96 times per day resulted in significantly higher BOD5 removal than a low dosing frequency of 48 times/d. The average BOD5 concentration in effluent for 96 times/d was 6.2 mg/L, where it was less than half for a dose frequency of 48 times/d (13.3 mg/L). Crushed glass was found to perform similarly as silica sand; which represents an alternative for biofiltration media. Peat filter resulted in the lowest NH4+-N (84.5%) removals and sand filter provided the highest NH4+-N removal (98.0%). Geotextile provided the highest total phosphorus removal (73.8%). Scanning electronic microscope (SEM) images of the biofilm around particles at different depth of filter suggested that filter depth should be considered as a design criterion as well. From a practical perspective this study provides a greater understanding of the critical design factors for RBFs and also demonstrated the feasibility and limitations of possible filter media alternatives (i.e., crushed glass, peat, and geotextile).Key words: recirculating sand filters, sand, crushed glass, peat, geotextiles.

The main objective of this paper was to evaluate the effectiveness of silica sand, crushed glass, peat, and geotextile as a medium in RBFs in the removal for organic matter, nutrients and bacteria from domestic wastewater based on a field-scale study. In particular, this field-scale study was conducted to treat domestic wastewater from a small community of 10 households from the Municipality of Lunenburg, Nova Scotia, Canada. The average influent 5d biochemical oxygen demand (BOD(5)) and total suspended solids (TSS) concentrations into the field filter system were 381+/-64 (mean+/-standard deviation) and 46+/-21 mg/L, respectively. The results showed that crushed glass could be an effective medium in RBFs since the crushed glass filter produced stable effluent BOD(5) and TSS concentrations of less than 20mg/L. Geotextile was found to be another successful alternative filter medium with the effluent BOD(5) and TSS of 18+/-11 and 11+/-7 mg/L, respectively, even though the porosity of geotexitle filter was as high as 0.90. Peat was not able to provide efficient performance due to its poor BOD(5) and NH(4)(+)-N removals. This study measured the water quality variation at different components of the RBFs. The results of this study showed that the recirculation tank was the main facilitator of the denitrification process. In addition, this study found that RBFs could efficiently treat domestic wastewater for BOD(5) removal under the organic loading rates as high as 0.070 kg/m(2)/d.

This study sought to understand the performance of arctic treatment systems and the impact of wastewater effluent on benthic invertebrate communities in arctic receiving water habitats. Effluent quality and benthic impacts were monitored in the receiving water of five communities across Nunavut that differed in the type and level of treatment achieved by wastewater infrastructure, the volume of effluent and receiving water mixing environment. We detected minimal impacts to benthic communities (225 m linear distance from the effluent source) in four out of the five communities (Grise Fiord, Kugaaruk, Pond Inlet, and Pangnirtung), where the population was2000 people. In these small communities impacts were characterized by increases or decreases in species richness, diversity, evenness, and density, and some differences in benthic species composition. This was in contrast to benthic sediments in Iqaluit (population 6699), which were devoid of benthic fauna up to 580 m from the effluent source in response to sediment anoxia. Variation in benthic community response between sampling locations was attributed primarily to differences in effluent volume, with effluent quality and receiving water hydrodynamics playing secondary roles. The results of this study will help to inform the development of northern specific treatment performance standards which will aid in prioritizing community wastewater system upgrades in arctic communities.

Drinking water utilities may be required to change disinfectant to improve water quality and meet more stringent disinfection regulations. This research was conducted to assess and compares chlorin...

The objective of this project was to evaluate the impact of secondary disinfectants on internal corrosion and water quality in old, unlined cast-iron water distribution system pipes. The disinfectants evaluated for this study were free chlorine, chloramines, chlorine dioxide and chlorite. The investigation was conducted with five recirculating pipe loops, one for each disinfectant and one control, to observe the impacts of corrosion. The loops were evaluated over a period of 220 days. Collected samples were evaluated for corrosion rate, total and dissolved iron, and turbidity. Results indicate that monochloramine and free chlorine increase corrosion rate within distribution systems, with average rate of 5.9 and 3.3 ml per year (mpy), respectively. Chlorine dioxide, at levels used for drinking water treatment, did not impact corrosion, as the rates were similar to those observed in the control loop, with an average rate of 2.2 mpy. The average corrosion rate in the control loop was 2.1 mpy. Corrosion rates decreased, with respect to the control, when chlorite was used, with an average rate of 0.9 mpy over the course of experimentation. Similar trends were observed for total and dissolved iron. Iron levels were higher for free chlorine, monochloramine and chlorine dioxide (2.82, 1.36 and 0.72 mg l −1 , respectively), with respect to the control (0.11 mg l −1 ). However, iron levels were lower when chlorite was used (0.03 mg l −1 ). It is hypothesized that chlorite was reacting with soluble Fe 2+ and other metals and thereby reducing corrosion and red water. Overall, these findings indicate that disinfection with chlorite decreased the corrosion rate within the distribution system and chlorine dioxide produced corrosion rates comparable to the control pipe loop.

Spent filter backwash water (SFBW) and clarifier sludge comprise the majority of the waste streams from conventional surface water treatment plants and collectively are referred to as composite residuals stream. Composite residuals streams can comprise up to 3–10% of the plant throughput and generally consist of concentrated metals (e.g., aluminum), colloidal material, natural organic matter (NOM), and pathogens (e.g., Giardia and Cryptosporidium). This research project evaluated the performance of four different treatment processes in terms of their capability of restoring this waste stream to a quality that was equal to or better than that of the source water quality. The unit operations evaluated were (i) gravity thickening, (ii) sedimentation with reflocculation, (iii) dissolved air flotation (DAF) with reflocculation, and (iv) ultrafiltration (UF). The water quality from the optimal trials met or exceeded the average raw water quality of the source water for all measured parameters with the exception of manganese. The optimal pH for sedimentation was determined to be 6.0 with no alum addition. The best coagulant dosage and recycle ratio for dissolved air flotation (DAF) were found to be 30 mg/L and 20%, respectively. The optimum settling time for thickening was determined to be 0.8–1.0 d, after which soluble metal concentrations began to increase because of re-solubilization. Ultrafiltration required no coagulant and yielded superior results to the other unit operations evaluated. Key words: filter backwash water, residual treatment, gravity thickening, sedimentation, dissolved air flotation, ultrafiltration.

Sedimentation is a widely used separation method for treating agricultural waste. There are several chemical and biological characteristics, which can affect the settling behavior and liquid waste. The optimization of cation balances and potential for nitrification are among these processes. In addition to sedimentation, it can also affect the dewaterability of the samples. Liquid hog manure was used during the laboratory based experiments to investigate the effects of Ca2+ and Mg2+ ions and nitrification inhibition on the overall settling and dewatering characteristics. The results indicated that settling and dewatering characteristics improved during the course of the experiments. However, the improvement in settling and dewatering characteristics was inconsistent and not statistically significant. Cation addition in aerated reactor increased the highest settling velocity (94%). The improvement in dewaterability, as quantified by capillary suction time, was also not consistent. The greatest filterability observed in the supernatant was a capillary suction time of 40 s for a M:D ratio of 2:1. Initial NH 4 + concentration was more important than the nitrification inhibitor, as the presence of nitrification inhibitor increased the nitrification rate by over 300% because of the high initial NH 4 + concentration and low volatile suspended solid. The results from these experiments provide the basis for further field evaluation of cation optimization.

Swine wastewater (agricultural wastewater) is normally stored in a storage holding tank for a certain time before released to the other treatment units, such as anaerobic lagoon and aerobic wetland. One of the characteristics for this treatment approach is that all the processes are open systems that are generally more passive in design and operation. As a consequence, seasonal variability including temperature and precipitation can have substantial impact on treatment efficacy and effluent water quality. This paper examines seasonal impacts of temperature on swine wastewater quality and treatment efficacy at a farm in East Leicester, Nova Scotia, Canada. During warm temperatures denitrification was noticeable in the anaerobic conditions, which would reduce the TSS removal rate from 76.6% in moderate temperatures to 42.1% in the warmest period recorded. Rainfall improved final effluent water quality, although this was shown to be through dilution rather than improvement of treatment efficacy. Following precipitation events the contaminant removals were negatively impacted in the aerobic lagoon, as BOD5 removal decreased from 61.6% before rainfall to 41.5% after rainfall, TSS from 71.4% to 59.3%, VSS from 73.4% to 59.3%, TKN from 59.9% to 42.1%, and NH4+ -N from 51.3% to 41.6%. In comparison to the aerobic conditions, the removal rates were increased for anaerobic condition with the rainfall dilution (e.g., TSS from 18.2% to 34.3%), which lead to an overall treatment improvement for the entire system. Thus the case study data presented in this paper provides an assessment of the operational and design issues that are particularly relevant for passive treatment systems that are used in the agriculture industry.

Spent filter backwash water (SFBW) and clarifier sludge generally comprise the majority of the waste residual volume generated and in relative terms, these can be collectively referred to as combined filter backwash water (CFBW). CFBW is essentially a low-solids wastewater with metal hydroxide flocs that are typically light and slow to settle. This study evaluates the impact of adding calcium and magnesium carbonates to CFBW in terms of assessing the impacts on the sedimentation and DAF separation processes. Representative CFBW samples were collected from two surface water treatment plants (WTP): Lake Major WTP (Dartmouth, Nova Scotia, Canada) and Victoria Park WTP (Truro, Nova Scotia, Canada). Bench-scale results indicated that improvements in the CFBW settled water quality could be achieved through the addition of the divalent cations, thereby adjusting the monovalent to divalent (M:D) ratios of the wastewater. In general, the DAF process required slightly higher M:D ratios than the sedimentation process. The optimum M:D ratios for DAF and sedimentation were determined to be 1:1 and 0.33:1, respectively. It was concluded that the optimisation of the cation balance between monovalent cations (e.g., Na(+), K(+)) and added divalent cations (i.e., Ca(2+), Mg(2+)) aided in the settling mechanism through charge neutralisation-precipitation. The increase in divalent cation concentrations within the waste residual stream promoted destabilisation of the negatively charged colour molecules within the CFBW, thereby causing the colloidal content to become more hydrophobic.

Ozone (O3) is a powerful oxidant and is becoming popular in various aquaculture systems for disinfection and improving water quality by oxidation of inorganic and/or organic compounds. However, the use of ozone in marine-based aquaculture systems has been limited because of the potential to form bromate, which is formed during the oxidation of naturally occurring bromide by ozone. Because bromate is a human carcinogen, there are concerns with its chronic impact on fish health. In addition, the use of O3 is hindered by lack of quantitative as well as qualitative design and performance information on O3 for recirculating systems. This study investigated the application of ozonation to control pathogens and enhance the process water quality in a recirculating aquaculture system while minimizing bromate formation. A field scale monitoring program was conducted on process water quality from Atlantic halibut (Hippoglossus hippoglossus) recirculating systems. Ozonated modules showed reduction of 15% total organic carbon (TOC) and less than 25 μg/l bromate concentration was formed. In addition, ozonated modules showed reduction in nitrate, color and suspended solids, as compared to those that did not use ozone. The results of this study elucidates the formation of bromate in marine water recirculation systems.

In recent years, model distribution systems have become valuable tools for understanding physical, chemical and microbiological processes that occur in full-scale distribution systems. These systems enable numerous treatment strategies to be examined in controlled conditions and without adversely affecting the water quality at a customer9s tap. Many model reactors have been developed for obtaining water quality data for evaluating very specific processes that occur in the distribution system (e.g. trihalomethane formation). The simulated distribution system (SDS) test is used to predict the formation of trihalomethanes in the distribution system, annular reactors (AR) are commonly used for biofilm studies and pipe rig systems can be used for a variety of studies including corrosion and biofilm. Of the three model reactors, pipe rig systems provide the most flexibility, however relatively few standard or de facto testing procedures have been developed in comparison to the other laboratory-based model systems (e.g. SDS test protocol). There are several hydraulic configurations that can be modelled along with various lengths and diameters of different pipe materials. However, this flexibility and the lack of standard pipe rig designs cause difficulties in making broad comparisons among research projects. This paper outlines the important design variables of a pipe rig system and provides examples of different options for each variable. Based on a thorough review of previous pipe rig studies, a framework was developed to assist in the design and selection of pipe rig configurations. It is recommended that the framework provides a method for selecting the physical and hydraulic configuration for future pipe rig investigations. Ultimately, the framework would provide the water industry with potential designs that would allow for improvement in data evaluation and strategies for minimizing water quality degradation in distribution systems.

Filter performance has traditionally been assessed using turbidity as the main water quality parameter. However interest in process optimization and the ability to accurately monitor filtration and particle removal has led to particle counting becoming increasingly more popular. The objective of this research was to evaluate filtration performance and filter ripening at four full-scale water treatment plants. Most of the plants investigated in this study were capable of achieving 2 log total particle removal as well as an effluent turbidity of 0.1 NTU. In some cases 2 log removal was achieved in the lower particle size ranges of 2-5 and 5-10 microm. Log removals in this study compare particle counts in the filtered and raw water. For water treatment plants that do not filter to waste, the ripening period following a filter backwash represents a time where the plant may be most vulnerable to breakthrough of waterborne pathogens. For the plants studied, the ripening period which was defined as the time required to reach peak particle removal and a turbidity of 0.1 NTU, were very similar in duration. The ripening period generally lasted for one hour after the backwash event had been completed. Because the times to reach 2 log total particle removal and 0.1 NTU are similar, the practice of using 0.1 NTU turbidity as a measure of filter ripening may be a useful benchmark for utilities that do not have particle counters.

The objective of this project was to determine the impact hydraulic dispersion has on the calibration of a flow-through model ultraviolet (UV)-disinfection system with chemical actinometry (potassium ferrioxalate) and MS 2 bacteriophage. Fluence was supplied by a medium-pressure ultraviolet lamp to a quartz tube (19 mm diameter) situated in a ventilated galvanized casing. The UV lamp was attached to a vertical position guide, for UV fluence to be varied by positioning the UV lamp at various vertical heights above the quartz tube. Water was pumped through the quartz tube at rates of 100-300 mL/min. An in-line pipe mixer was installed prior to the UV system to ensure adequate mixing with the bulk liquid and chemical actinometer and to mitigate jet formation within the quartz tube. Tracer studies were conducted with and without the in-line mixer using potassium chloride (3 mM). Dispersion coefficients were obtained from the tracer study and incorporated into an axial-dispersion model to determine the rate coefficient of potassium ferrioxalate in the model UV system. A numerical model was used to determine the fluence supplied by the lamp with a reduction in exposure time. After dispersion and kinetics are accounted for within the UV system, the model predicted UV fluence that was in general agreement with UV design curves for inactivation MS 2 bacteriophage. The differences in the design curves and the fluence-response model in the present investigation were found to be related to the experiment errors introduced from using a flowing system and because a medium pressure lamp was used in the present investigation.

The objective of this project was to evaluate the performance of a pressure filter utilizing crushed glass as the filter media in a dual media anthracite–glass filter compared to a dual media anthracite–sand filter. In general, the particle removal capabilities of the crushed-glass filter were slightly poorer than those of a sand filter, as quantified in a field application in the community of Orangedale, Nova Scotia. It was found that the crushed glass used in this project had a higher angularity and slightly higher uniformity coefficient then the sand tested. After 6 months of use the crushed-glass filter was able to produce a filter effluent of 50–70 particles/mL (diameter >2 μμm), which is greater than the 25–50 particles/mL (diameter >2 μμm) that was produced by sand filter. Over the course of the 6-month study the dual media crushed-glass filter was able to achieve a 1.4-log removal, which was only slightly greater than the dual media silica sand filter that achieved a 1.6-log removal of particles with diameters >2 μμm. Key words: filtration, drinking water, recycled glass, sustainability, particle counting.

Drinking water utilities may have to consider changing disinfectant to improve water quality and meet more stringent disinfection regulations. The objective of this study was to evaluate the response of a full-scale drinking water distribution system to a change in disinfectant from chlorine to chlorine dioxide, in terms of its impact on microbiological stability and disinfection by-product formation. Chlorine dioxide residuals were consistently present above detection limits throughout the distribution system (>0.20 mg/L). Over a study period of 3.5 months, no degradation of bacterial water quality occurred after implementing the new disinfectant. Chlorine dioxide maintained total bacteria (microscopic counts) and heterotrophic plate count levels below 2 x 105 cells/mL and 1000 CFU/mL, respectively. The change in disinfectant from chlorine to chlorine dioxide led to an 85% reduction in trihalomethanes (i.e., from 30 to 5 μμg/L) and a 60% reduction in haloacetic acids (i.e., from 20 to 8 μμg/L). Chlorine dioxide represents a valuable tool to produce high quality water and is a strong alternative to chlorine for certain distribution systems. Key words: distribution system, chlorine dioxide, drinking water quality, disinfection by-products.

The number and complexity of natural organic matter (NOM) species limits identification of individual NOM compounds. The objective of this study was to employ several characterization techniques (resin fractionation, high performance size exclusion chromatography (HPSEC), and strategic UV254 absorbance) to samples from seven surface water sites in North America, and overcome the shortfalls of each tool. Resin fractionation indicated the samples were all high in hydrophobic acids (HOA), hydrophilic neutrals (HIN) and hydrophilic acids (HIA). Site B was the only site where HIAs were the highest NOM contributors. In the HPSEC analysis, each fraction exhibited a particular molecular weight (MW) range: 100-300 Da (HIN), 1-2 kDa (HOA), and the HIA fractions exhibited MWs between these two ranges. Strategic UV254 measurements were taken at two sites to supplement the HPSEC results, and determine the difference in UV absorbance per unit dissolved organic carbon (SUVA value). Most fractions showed SUVA values of approximately 5 L/mg-m; however, the hydrophilic bases and hydrophobic neutral fractions could not be accurately evaluated due to the very low DOC concentrations for these two fractions (0.2 mg/L). These methods are complimentary NOM characterization techniques, and the combined methodology addresses the analytical limits of each tool.

Aqueous chlorination kinetics of the lipid regulator gemfibrozil and the formation of reaction products were investigated in deionized water over the pH range 3 to 9, and in two wastewater matrices. Chlorine oxidation of gemfibrozil was found to be highly dependent on pH. No statistically significant degradation of gemfibrozil was observed at pH values greater than 7. Gemfibrozil oxidation between pH 4 and 7 was best represented by first order kinetics. At pH 3, formation of three reaction products was observed. 4'-C1Gem was the only reaction product formed from pH 4-7 and was modeled with zero order kinetics. Chlorine oxidation of gemfibrozil in two wastewater matrices followed second order kinetics. 4'-C1Gem was only formed in wastewater with pH below 7. Deionized water rate kinetic models were applied to two wastewater effluents with gemfibrozil concentrations reported in literature in order to calculate potential mass loading rates of 4'C1Gem to the receiving water.

Research has shown biological filtration to be a successful treatment for the removal of manganese (Mn) from groundwater and surface water. In this study, bench-scale direct biofiltration was used to remove Mn and dissolved organic carbon (DOC) from a pH 6 surface water source in Halifax, Nova Scotia, Canada. Three factors were examined for their effects on Mn and DOC removal: media type (granular activated carbon and anthracite), pH (6 and 9–11), and nutrient enhancement with phosphorus (P; 20 and 200 μg/L). pH was a significant factor in Mn removal (α=0.05). The P-enhanced pH 6 biofilters for both media obtained an average 91% Mn removal; the P-enhanced pH 9–11 filters for both media achieved an average 70% Mn removal. An average of 23% DOC removal was achieved with P enhancement, compared to 12% DOC removal without P enhancement. Mn was likely removed by biological oxidation and biogenic oxide adsorption. These results show that direct biofiltration of raw surface water at pH 6 can remove Mn t...