Rapid gravity filters used in the treatment of drinking water are subject to small continuously occurring flow rate fluctuations known as surges. Large, step changes in the rate of flow have been shown to have a detrimental effect on filtrate quality. However, less is known about the effects of surging flow on rapid filter performance. Measurements by previous researchers have found that surges from 2 to 10 % of the flow rate are common and can occur as many as one hundred times per minute. It has been suggested that surging may significantly influence rapid filter performance but the effect has yet to be confirmed under well-controlled conditions and the mechanisms critically examined. Measurements taken by this author at local water treatment plants confirmed the presence of surging flow in the rapid gravity filters of a similar nature to other researchers' findings. Evidence suggested the degree of surging present was related to the design of the filtrate piping and some design recommendations are made on this basis. Two rapid gravity filters were developed in the laboratory to investigate the influence of surging flow on filter performance. The filters were constructed from Perspex pipe and comprised 600 mm of 0.5 to 1.0 mm filter sand. The filters were operated at 30°C at an approach velocity of 8.0 metres per hour with a test suspension of PVC particles. Reproducible performance was established before applying surges to one filter only. A range of surging characteristics similar to those observed at full-scale plants was applied during the test programme. Measurements of head loss and turbidity were taken at a range of depths within the filter media periodically during each test. Samples were collected for particle size distribution analysis from selected tests. The surging flow was found to inhibit the performance of the laboratory filters. The fluctuations in flow rate were found to reduce the removal efficiency of turbidity' and retard the rate of head loss development. The surges were found to inhibit the removal of all particle sizes present in the test suspension. The magnitude of the effect on filter performance was found to be dependent on the magnitude and frequency of occurrence of the surges applied. The experimental results obtained suggest that surging does have an effect on full- scale rapid filter performance and has implications for drinking water quality.

ABSTRACT With an increasing population density throughout the world and the current drive to provide fresh water to as many people as possible, innovative methods of providing safe drinking water are in very high demand. In 2002, the United Nations stated in their millennium declaration that one of their priority goals was “to halve, by the year 2015, the proportion of people who are unable to reach or to afford safe drinking water” (UNESCO, 2000). This goal was set with high standards, and will require a great deal of water treatment related research in the short coming years. Over the past two decades, drinking water treatment via membrane filtration has been widely accepted as a feasible alternative to conventional drinking water treatment. Membrane processes are used in environmental, chemical, food, beverage, pharmaceutical, and various other industries for separation applications. Since the early 1990’s, there has been rapid growth in the use of low-pressure hollow fibre membrane processes for the production of drinking water. These membrane systems are increasingly being accepted as feasible technologies for drinking water treatment. Like with any innovative process, it has limitations; the primary limitation being membrane fouling, which is an accumulation of particles on the surface and inside the pores of the membrane surface. Membrane fouling has the ability to reduce the flux, in doing so, requiring a higher pumping intensity to maintain a consistent volume of water being treated. This project investigated chemical coagulation as a pre-treatment to membrane ultra-filtration, with the goal of mitigating fouling impact in order to maintain a consistent permeate flux, while monitoring several water quality parameters before and after treatment such as turbidity, alkalinity, pH and total organic carbon (TOC). Two different raw water sources were studied: Grand River water taken from the Hidden Valley intake, located in Kitchener, ON, and Lake Ontario water taken from the Woodward Water Treatment Plant in Hamilton, ON. The evaluated coagulants include alum and ferric chloride, which are widely used hydrolyzing metal salt (HMS) coagulants; and three polyaluminum chloride (PACl) products, which are pre-hydrolyzed coagulants formed by the controlled neutralization of aluminum chloride solution. Phase 1 of the project involved the coagulation of water using various aluminum and iron-based coagulants. Synthetic water was used at the outset, followed by the use of raw water obtained from two water treatment plants: one on the Grand River and one on Lake Ontario. A series of jar test trials was conducted to determine optimum coagulant dosages for the removal of NOM. These doses were then used as a baseline for subsequent membrane trials in phase 2 of this project. Phase 2 involved the treatment of raw and coagulated waters with a hollow fibre bench scale UF unit (Zenon Environmental Inc.®, ZeeWeed-1). Membrane trials were performed with the coagulants applied at optimal and sub optimal dosages in order to evaluate the integrated process for mitigation of organic fouling. As all trials were conducted at a constant flowrate, membrane fouling was evaluated by monitoring trans-membrane pressure (TMP) over time. The raw and treated water were fractionated to obtain quantitative information on the size components of NOM contributing most to fouling. Results will be presented comparing how the different coagulants affected the concentration of each NOM MW fraction in the raw and treated waters. Collectively, results showed that all four coagulants substantially decreased the rate of TMP increase, particularly with the Grand River water which contained much higher turbidity and TOC concentrations than the Lake Ontario water. During the trials conducted with Grand River, alum performed best, reducing the TMP by 57 % over a 3-day period. The PACl coagulants performed best at reducing the TMP during the Lake Ontario membrane trials; reducing the TMP by 21 % and 19 % for SP 70 and SP respectively. The system’s ability to maintain a permeate turbidity level of 0.1 NTU or lower was met, and TOC removals varied a small amount across the four coagulants, ranging from 45-65 % and 15-35 % for the Grand River and Lake Ontario trials, respectively.

ABSTRACT With an increasing population density throughout the world and the current drive to provide fresh water to as many people as possible, innovative methods of providing safe drinking water are in very high demand. In 2002, the United Nations stated in their millennium declaration that one of their priority goals was “to halve, by the year 2015, the proportion of people who are unable to reach or to afford safe drinking water” (UNESCO, 2000). This goal was set with high standards, and will require a great deal of water treatment related research in the short coming years. Over the past two decades, drinking water treatment via membrane filtration has been widely accepted as a feasible alternative to conventional drinking water treatment. Membrane processes are used in environmental, chemical, food, beverage, pharmaceutical, and various other industries for separation applications. Since the early 1990’s, there has been rapid growth in the use of low-pressure hollow fibre membrane processes for the production of drinking water. These membrane systems are increasingly being accepted as feasible technologies for drinking water treatment. Like with any innovative process, it has limitations; the primary limitation being membrane fouling, which is an accumulation of particles on the surface and inside the pores of the membrane surface. Membrane fouling has the ability to reduce the flux, in doing so, requiring a higher pumping intensity to maintain a consistent volume of water being treated. This project investigated chemical coagulation as a pre-treatment to membrane ultra-filtration, with the goal of mitigating fouling impact in order to maintain a consistent permeate flux, while monitoring several water quality parameters before and after treatment such as turbidity, alkalinity, pH and total organic carbon (TOC). Two different raw water sources were studied: Grand River water taken from the Hidden Valley intake, located in Kitchener, ON, and Lake Ontario water taken from the Woodward Water Treatment Plant in Hamilton, ON. The evaluated coagulants include alum and ferric chloride, which are widely used hydrolyzing metal salt (HMS) coagulants; and three polyaluminum chloride (PACl) products, which are pre-hydrolyzed coagulants formed by the controlled neutralization of aluminum chloride solution. Phase 1 of the project involved the coagulation of water using various aluminum and iron-based coagulants. Synthetic water was used at the outset, followed by the use of raw water obtained from two water treatment plants: one on the Grand River and one on Lake Ontario. A series of jar test trials was conducted to determine optimum coagulant dosages for the removal of NOM. These doses were then used as a baseline for subsequent membrane trials in phase 2 of this project. Phase 2 involved the treatment of raw and coagulated waters with a hollow fibre bench scale UF unit (Zenon Environmental Inc.®, ZeeWeed-1). Membrane trials were performed with the coagulants applied at optimal and sub optimal dosages in order to evaluate the integrated process for mitigation of organic fouling. As all trials were conducted at a constant flowrate, membrane fouling was evaluated by monitoring trans-membrane pressure (TMP) over time. The raw and treated water were fractionated to obtain quantitative information on the size components of NOM contributing most to fouling. Results will be presented comparing how the different coagulants affected the concentration of each NOM MW fraction in the raw and treated waters. Collectively, results showed that all four coagulants substantially decreased the rate of TMP increase, particularly with the Grand River water which contained much higher turbidity and TOC concentrations than the Lake Ontario water. During the trials conducted with Grand River, alum performed best, reducing the TMP by 57 % over a 3-day period. The PACl coagulants performed best at reducing the TMP during the Lake Ontario membrane trials; reducing the TMP by 21 % and 19 % for SP 70 and SP respectively. The system’s ability to maintain a permeate turbidity level of 0.1 NTU or lower was met, and TOC removals varied a small amount across the four coagulants, ranging from 45-65 % and 15-35 % for the Grand River and Lake Ontario trials, respectively.

Increasingly stringent water quality regulations concerning microbiological parameters govern the use of groundwater resources that are vulnerable to mixing with surface waters. These drinking water sources are at higher risk for infiltration by pathogenic microorganisms, including the oocysts of the human enteroparasite Cryptosporidium spp. Cryptosporidium can cause severe gastroenteritis in humans, and the characteristics of Cryptosporidium oocysts, including low infectious dose, high resistance to inactivation, and long survival in the environment pose a significant risk to public health if present in treated drinking water. Bacillus subtilis is widely used as a surrogate for biocolloid transport in saturated porous media, and recognized as a conservative indicator for the transport of Cryptosporidium parvum oocysts during filtration. However, no study has directly compared the transport of spores from different strains within the Bacillus subtilis species. Strain variability has the potential to impact retention in porous media based on differences in size and electrophoretic mobility. The transport behaviour of four strains of Bacillus subtilis (wild-type and laboratory type, subspecies subtilis and subspecies spizizenii; 1.9 to 2.9µm diameter) is contrasted in this research to two sizes of fluorescent polystyrene microspheres (1.1µm and 4.5µm diameter) through packed saturated crushed quartz sand. A peristaltic pump was used to introduce (bio)colloids into the duplicate column apparatus at a loading rate of 0.1m/day. (Bio)colloid removal was assessed and compared by constructing breakthrough curves of normalized concentrations and box-and-whisker diagrams of percent removal of Bacillus subtilis strains. Under unfavourable conditions minimal reduction (<0.22log10) in effluent spore concentration was observed over the column depth of 15cm. In favourable attachment conditions up to 0.69 log10 reduction was observed but the sampling schedule employed was insufficient to clearly identify a pseudo steady-state plateau. An analysis of variance was used to determine the statistical significance of spore strain, subspecies, and type. A significant difference between the four strains was observed at the lower ionic strength, with spore subspecies and type affecting spore removal in unfavourable conditions (p < 0.05). Some sensitivity to settling and laboratory storage suggests that standardized sample handling procedures are required. Differences observed here between the strains of Bacillus subtilis spores indicate that riverbank filtration performance assessments and drinking water treatment plant process demonstrations may benefit from a recommended strain for use.

Increasingly stringent water quality regulations concerning microbiological parameters govern the use of groundwater resources that are vulnerable to mixing with surface waters. These drinking water sources are at higher risk for infiltration by pathogenic microorganisms, including the oocysts of the human enteroparasite Cryptosporidium spp. Cryptosporidium can cause severe gastroenteritis in humans, and the characteristics of Cryptosporidium oocysts, including low infectious dose, high resistance to inactivation, and long survival in the environment pose a significant risk to public health if present in treated drinking water. Bacillus subtilis is widely used as a surrogate for biocolloid transport in saturated porous media, and recognized as a conservative indicator for the transport of Cryptosporidium parvum oocysts during filtration. However, no study has directly compared the transport of spores from different strains within the Bacillus subtilis species. Strain variability has the potential to impact retention in porous media based on differences in size and electrophoretic mobility. The transport behaviour of four strains of Bacillus subtilis (wild-type and laboratory type, subspecies subtilis and subspecies spizizenii; 1.9 to 2.9µm diameter) is contrasted in this research to two sizes of fluorescent polystyrene microspheres (1.1µm and 4.5µm diameter) through packed saturated crushed quartz sand. A peristaltic pump was used to introduce (bio)colloids into the duplicate column apparatus at a loading rate of 0.1m/day. (Bio)colloid removal was assessed and compared by constructing breakthrough curves of normalized concentrations and box-and-whisker diagrams of percent removal of Bacillus subtilis strains. Under unfavourable conditions minimal reduction (<0.22log10) in effluent spore concentration was observed over the column depth of 15cm. In favourable attachment conditions up to 0.69 log10 reduction was observed but the sampling schedule employed was insufficient to clearly identify a pseudo steady-state plateau. An analysis of variance was used to determine the statistical significance of spore strain, subspecies, and type. A significant difference between the four strains was observed at the lower ionic strength, with spore subspecies and type affecting spore removal in unfavourable conditions (p < 0.05). Some sensitivity to settling and laboratory storage suggests that standardized sample handling procedures are required. Differences observed here between the strains of Bacillus subtilis spores indicate that riverbank filtration performance assessments and drinking water treatment plant process demonstrations may benefit from a recommended strain for use.

The use of dissolved air flotation (DAF) for drinking water treatment has steadily grown in popularity in Atlantic Canada for the treatment of low turbidity water supplies with high levels of algae or dissolved organic matter. Runoff from high intensity rainfall events may cause a rapid increase in turbidity and dissolved organic matter in rivers and lakes used for drinking water. A technical evaluation of a DAF water treatment plant (WTP) was conducted to determine the contributing factors to clearwell turbidity increases resulting from increased raw water turbidity and colour during intense rainfall and runoff events. The effect of chemical and operational factors on treatment of a low turbidity and colour water source as well as a high turbidity and colour water source were examined, including coagulant dose, coagulation pH, polyaluminum chloride (PACl) coagulant basicity and DAF recycle rate. In response to deteriorating water quality, it was found that increased coagulant addition inadvertently caused the loss of coagulation pH control in a full-scale DAF WTP, resulting in potentially elevated dissolved aluminum residuals entering the clearwell. This would have led to excessive aluminum hydroxide precipitation in the clearwell, and resulted in turbidity increases above the acceptable limit of 0.2 NTU. Turbidity was found to be better removed, and dissolved aluminum residuals minimized, when coagulation pH was set to the pH of minimum aluminum solubility vs. a lower pH of 6.0 during bench-scale DAF testing. A higher dose of coagulant was required to produce optimal removal of turbidity and dissolved organics at the pH of minimum solubility. The difference in bench-scale DAF treatment performance was found to be minimal when comparing sulphated PACl coagulants with 50 and 70+ % basicity. Charge analysis parameters zeta potential and streaming current were found to have a strong correlation in bench-scale testing, though the relationship between the two was affected by the coagulation pH. The results suggest that utilizing streaming current for coagulant dose control at a full-scale WTP would be best accomplished by establishing a consistent relationship between raw water quality, pH and other factors with streaming current experimentally before relying streaming current targets for dose control. Equivalent or improved DAF efficacy for solid-liquid separation was found when the recycle rate was lowered from 12 to 6 % in bench-scale tests and 12 to 8% in full-scale tests. The results suggested that maintaining an optimum air:solids ratio improved treatment performance, possibly by providing adequate bubble contact opportunities while minimizing excess shearing of the sludge blanket. The most significant finding of this research was that maintaining the coagulation pH in WTPs utilizing PACl coagulants is of utmost importance during source water quality deterioration in order to optimize treatment performance as well as prevent excess dissolved and precipitated aluminum from entering a public drinking water supply.

"The goals of this study were (1) to evaluate the impacts of pesticides used for mosquito control on drinking water and (2) to investigate the removal of permethrin from water using activated carbon. A review of current literature on pesticide usage, toxicity, occurrence in the environment, and treatment techniques to remove pesticides from drinking water was conducted. The focus of the literature review was on pesticides used for mosquito control. Permethrin is a synthetic pyrethroid insecticide used extensively in the United States (US) for mosquito control and in agriculture, with approximately 2 million pounds applied each year. Permethrin was selected for investigation based on its widespread use in the US, its inclusion on the Contaminant Candidate List 3 (CCL3), its health hazards, and the lack of previous research on the removal of permethrin from drinking water. The removal of permethrin from water using powdered activated carbon (PAC) was investigated. Equilibrium adsorption experiments to assess removal of cis-, trans-, and total permethrin were conducted using two types of PAC (WPH 650 and WPH 1000). Initial total permethrin concentrations ranged from 2.0 to 4.6 ug/L. PAC doses ranged from 0.0 to 10 mg/L. Results showed that PAC addition is an effective method for removing permethrin from water. Total permethrin concentrations were reduced by 38% with 0.05 mg/L of PAC WPH 650, and reduced to below the detection limit with 3 mg/L of PAC WPH 650. Total permethrin concentrations were reduced by 35% with 0.05 mg/L of PAC WPH 1000 and by 83% with 5 mg/L of PAC WPH 1000. Results for cis- and trans- permethrin were similar. The Freundlich isotherm model provided appropriate fits to the data with an R-squared value of 0.91 for both WPH 650 and WPH 1000."

Disinfection byproducts (DBPs), such as organic chloramines, THMs, HAAs, and nitrosamines, are formed during mandatory disinfection processes in drinking water treatment. Many of these DBPs have been shown to be potentially carcinogenic. Extensive research has been conducted on the occurrence and formation of these DBPs. However, there has been limited research on their relationships with each other, which may be important for the understanding of their formation mechanisms, and the nature of their precursors is still relatively unknown. Ultimately, this information will be key for the development of possible improvements in treatment technologies. Results of this study improve the understanding of DBP formation in swimming pool water. Some BFAs and PCP additives were identified as potential DBP precursors. Influence of BFAs and PCP additives on DBP formation in swimming pool water was also illustrated. Results provided feasible strategies to minimize DBP formation while maintaining the efficiency of disinfection.

Disinfection byproducts (DBPs), such as organic chloramines, THMs, HAAs, and nitrosamines, are formed during mandatory disinfection processes in drinking water treatment. Many of these DBPs have been shown to be potentially carcinogenic. Extensive research has been conducted on the occurrence and formation of these DBPs. However, there has been limited research on their relationships with each other, which may be important for the understanding of their formation mechanisms, and the nature of their precursors is still relatively unknown. Ultimately, this information will be key for the development of possible improvements in treatment technologies. Results of this study improve the understanding of DBP formation in swimming pool water. Some BFAs and PCP additives were identified as potential DBP precursors. Influence of BFAs and PCP additives on DBP formation in swimming pool water was also illustrated. Results provided feasible strategies to minimize DBP formation while maintaining the efficiency of disinfection.

Application of low pressure membranes in drinking water treatment, including both microfiltration (MF) and ultrafiltration (UF), have witnessed a rapid increase in the past decades. Low pressure membranes are considered a good technology in retrofitting existing conventional drinking water treatment plants or in newly constructed plants to meet the stringent regulations for drinking water treatment that aim at preventing health risks of waterborne diseases. Enteric viruses are one of the major types of waterborne pathogens, and they can be commonly found and are persistent in the environment. Both the United States and Canada require a 99.99% (4-log) removal of viruses during the drinking water treatment train. Unlike MF membranes, UF membranes have a very good potential for removing enteric viruses from the water due to their smaller pores comparable to the size of viruses. Drinking water regulations/guidelines in both the United States and Canada do not grant UF membranes any removal credit for viruses by default; however they have the provision that, in certain cases, virus removal credit may be granted based on pilot scale challenge testing. A better understanding of the interaction between the UF membranes and virus rejection can help to establish a removal credit for UF membranes. An essential part of this will be the effect of the membrane operation on the rejection of viruses to determine if UF membranes can offer a consistent removal of viruses. Membrane fouling is one of the major problems in membrane operation and it can affect the rejection characteristics of the membrane and improve its performance. The aim of this study was to investigate the removal of virus surrogates (MS2 and φX174 bacteriophage) using a commercial UF membrane under different conditions, to obtain information about the removal mechanisms of viruses. The experimental filtration unit was designed to have similar conditions like the full scale membrane treatment plants. The UF membrane used in this study provided very good removal of both MS2 and φX174 bacteriophage. The obtained results were consistent and in agreement with the expected removals based on the membrane characterization results and types of virus surrogate. As part of this work, a detailed study to improve methods for characterizing the pore size distribution of membranes was conducted. In the second part of the study, two different types of surface waters were used to study the effect of membrane fouling on virus removal. It was found that mainly hydraulically irreversible fouling could significantly improve the virus removal by UF membranes. Different cleaning regimes that are used in treatment plants had varying effects on virus removal. After maintenance cleaning, virus removal remained higher than that of clean membranes, and only chemical cleaning was effective for completely removing membrane foulants and returning virus removal back to base levels. Advanced analytical techniques were used to define the nature of the fouling layer on the membrane surface and how the foulants affected the rejection of viruses. Finally, our study showed that UF membranes are a robust treatment technology for removing different types of enteric virus surrogates from water under different operational conditions. Close monitoring of the UF unit performance and direct integrity testing can possibly detect membrane problems that can affect the rejection of viruses. Based on the virus physical characteristics and a detailed study of the membrane surface characteristics, especially the pore size distribution of the membrane, the removal of the specific virus can be closely estimated.