This thesis investigates the susceptibility of various bacterial species to standard purification process.

No description available.

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.

The prevalence of the cyanobacterial metabolites: MIB, geosmin and microcystin in drinking water is a major concern to the water industry as these metabolites can compromise the quality of drinking water. Consequently, effective removal of these metabolites from drinking water is paramount. The combination of ozone (O3) and granular activated carbon (GAC) has been shown to be effective for the removal of these metabolites from drinking water. In this study, the ozonation of MIB and geosmin was affected by the character of natural organic material (NOM). In particular, NOM containing compounds of high UV absorbing properties and high molecular weight (MW) resulted in greater destruction of MIB and geosmin due to the formation of hydroxyl (OH) radicals. In addition, alkalinity also affected the ozonation process, with waters containing higher alkalinity resulting in decreased destruction of MIB and geosmin. Laboratory scale minicolumn experiments, coupled with the homogenous surface diffusion model (HSDM), were found to be ineffective in predicting the GAC breakthrough behaviour of MIB and microcystin at two different pilot plants. This can be attributed to the biological degradation of the metabolites at the pilot plants which cannot be modelled by the HSDM. In addition, the volume of GAC used in the minicolumn experiments may not have been appropriate for the predictions, rather, larger laboratory scale columns were found to be more applicable in mimicking pilot plant results. Microcystins were shown to be readily degraded by the bacteria attached to the GAC. Furthermore, the lag period prior to the onset of degradation, which is indicative of most biological degradation studies, was effectively eliminated and in one instance abated. This finding suggests that biological filtration of microcystin is practically feasible especially since the occurrence of microcystins in water supplies is seasonal. This study expands on previous research in the area of O3 and GAC for the treatment of MIB, geosmin and microcystin. With the imminent increase of the use of O3 and GAC in Australian water treatment plants (WTPs), this study provides valuable information for the use of these processes both alone and in combination, particularly since minimal research in this area has been conducted in Australia. / thesis (PhDAppliedScience)--University of South Australia, 2004.

Thesis (M. Sc.)(Microbiology)--University of Pretoria, 2005. / Includes summary. Includes bibliographical references (leaves 87-108). Available on the Internet via the World Wide Web.

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.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 205-211). Available also in a digital version from Dissertation Abstracts.

To effectively minimize biofilms, which are prevalent in chlorinated drinking water distribution systems, the effect of biofilm age on antimicrobial tolerance and resistance must be investigated. It was our hypothesis that antimicrobial tolerance emerges quickly during biofilm development and that both antimicrobial tolerance and resistance increase as the biofilm ages. We further hypothesized that antimicrobial tolerance and resistance vary among the individual community members. In this study, young and mature biofilms of Pseudomonas aeruginosa, a model biofilm organism, were grown and exposed to antimicrobial agents in several different treatments. Results showed that the increased antimicrobial tolerance of intact biofilms compared to planktonic cells arises early (i.e., within hours) in biofilm development. The short-term tolerance of resuspended mature biofilm cells to antimicrobial agents peaked at a biofilm age of 14 days and subsequently declined; the peak and decline in antimicrobial tolerance may be related to periodic detachment events in the biofilm. The antimicrobial resistance of resuspended mature biofilm cells continuously exposed to antimicrobial agents increased with biofilm age. Furthermore, individual members in mature biofilm communities exhibited variation in antimicrobial tolerance, thereby highlighting divergence of the biofilm community from the original parent strain.

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