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.

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Nitrification is a significant concern for drinking water systems employing chloramines for secondary disinfection. Utilities have implemented a range of disinfection strategies that have varying levels of effectiveness in the prevention and control of nitrification events, including optimizing the chlorine-to-ammonia ratio, maintaining chloramine residual throughout the distribution system, controlling pH, and temporal switching to free chlorination. Annual or semi-annual application of free chlorination is practiced by 23% of chloraminating systems on a temporary basis as a preventative measure, even though it has the undesirable consequences of temporarily increasing disinfection byproducts, facilitating coliform detachment, and altering water taste and odor. Although temporal free chlorination and other nitrification control methods have been widely studied in the field and in pilot-scale systems, very little is known about the stress responses of nitrifying bacteria to different disinfection strategies and the role physiological state plays in the resistance to disinfection. It is well known that many commonly studied bacteria, such as Escherichia coli, are able to better resist disinfection by free chlorine and chloramines under nutrient limitation through regulation of stress response genes that encode for DNA protection and enzymes that mediate reactive oxygen species. We compared the genomes of E. coli and the ammonia-oxidizing bacterium Nitrosomonas europaea, and found that many of the known stress response mechanisms and genes present in E. coli are absent in N. europaea or not controlled by the same mechanisms specific to bacterial growth state. These genetic differences present a general susceptibility of N. europaea to disinfection by chlorine compounds. Using an experimental approach, we tested the hypothesis that N. europaea does not develop increased resistance to free chlorine and monochloramine during starvation to the same degree as E. coli. In addition, N. europaea cells were challenged with sequential treatments of monochloramine and hypochlorous acid to mimic the disinfectant switch employed by drinking water utilities. Indicators of activity (specific nitrite generation rate) and viability (LIVE/DEAD® BacLight© membrane-integrity based assay) were measured to determine short-term effectiveness of disinfection and recovery of cells over a twelve day monitoring period. The results of disinfectant challenge experiments reinforce the hypothesis, indicating that the response of N. europaea to either disinfectant does not significantly change during the transition from exponential phase to stationary phase. Exponentially growing N. europaea cells showed greater susceptibility to hypochlorous acid and monochloramine than stationary phase E. coli cells, but had increased resistance compared with exponential phase E. coli cells. Following incubation with monochloramine, N. europaea showed increased sensitivity to subsequent treatment with hypochlorous acid. Complete loss of ammonia-oxidation activity was observed in cells immediately following treatment with hypochlorous acid, monochloramine, or a combination of both disinfectants. Replenishing ammonia and nutrients did not invoke recovery of cells, as detected in activity measurements during the twelve day monitoring period. The results provide evidence for the effectiveness of both free chlorine and chloramines in the inhibition of growth and ammonia-oxidation activity in N. europaea. Furthermore, comparison of viability and activity measurements suggest that the membrane integrity-based stain does not serve as a good indicator of activity. These insights into the responses of pure culture nitrifying bacteria to free chlorine and monochloramine could prove useful in designing disinfection strategies effective in the control of nitrification. / Master of Science

Corrosion of household copper plumbing infrastructure can cause pipe failure and lead to elevated levels of copper in drinking water which can exceed the USEPA health based standard for copper in drinking water of 1.3 mg/L Cu. The purpose of this study was to determine taste thresholds of copper in different types of water, analyze how copper chemistry can affect tasting, determine if common disinfectants influence the taste of copper and evaluate genetic links to copper sensitivity. A one-out-of-five test was used to define thresholds, evaluate disinfectant influences, and examine copper chemistry differences. A difference from control test was used to analyze soluble copper tasting and a one solution test with visual classification was used to discriminate 6-n-propylthiouracil (PROP) taster status. Solutions containing copper sulfate (0.05 – 8 mg/l Cu) were prepared in distilled water, mineral water of varying pH and mineral water with disinfectant added. Geometric mean copper taste thresholds were 0.48 mg Cu/l and 0.41mg Cu/l in distilled and mineral water pH 7.4 respectively. Logistic regression copper taste thresholds were 1.50 mg Cu/l and 1.96 mg Cu/l in distilled and mineral water pH 7.4 respectively. Soluble copper was readily tasted while particulate copper was poorly tasted. Chlorine and chloramines dosed at typical tap water levels had no significant effect on panelists' tasting abilities for water containing 1 mg/l total copper. Geometric mean copper thresholds values did not correlate with (PROP) status so PROP sensitivity would not be a good indicator for copper sensitivity. / Master of Science

Although the kinetics and mechanism of monochloramine decay in organic-free waters are relatively well understood, those in natural waters are not, due to exceedingly complex and poorly defined interactions of monochloramine with natural organic matter (NOM) and particles. Ozonation followed by a biologically activated carbon (BAC) filtration is a commonly practiced process option that affects the characteristics of both dissolved and particulate constituents in the water. However, how these changes in water constituents affect stability of the residual disinfectant, or monochloramine in particular, are currently unknown. Kinetics of monochloramine decay in water samples obtained before and after ozonation and BAC treatments were performed under varying operating conditions were determined by bench-scale batch experiments. Stability of monochloramine in the BAC filter effluent samples obtained at different times after backwashing was determined. It was found that in most cases monochloramine stability was greatly decreased after BAC filtration. Further filtering the BAC effluents with 1.2 and #61549;m polycarbonate membrane resulted in a substantial increase in monochloramine stability. A further increase was observed after filtering the samples using a 0.4 m membrane. This finding suggested that particulate matter generated from the filters could be the major cause of monochloramine instability. The fines from the activated carbon, possible components of the particulate matter eluting from the BAC filters, were found to exert an insignificant monochloramine demand both in the presence and absence of NOM, which is contrary to previous speculation in the literature about their demand for monochloramine. While there appears to exist a relationship between chloramine demand and HPC count of the filter effluent, more research will be needed to determine the effect of nature and type of microorganisms and their byproducts have on chloramine demand. Effect of ozonation on monochloramine stability is also under investigation using both the water sampled from full-scale plant and the synthetic water prepared with Suwannee River NOM.

This thesis documents the relationship among the major water quality parameters during a nitrification episode. Nitrification unexpectedly occurred in a chloraminated pilot drinking water distribution system practicing with a 4.0 mg/L as Cl2 residual dosed at 4.5:1 Cl2:NH3-N. Surface, ground and sea water were treated and disinfected with monochloramines to produce finished water quality similar to regional utility water quality. PVC, galvanized, unlined cast iron and lined iron pipes were harvested from regional distribution systems and used to build eighteen pilot distribution systems (PDSs). The PDSs were operated at a 5-day hydraulic residence time (HRT) and ambient temperatures. As seasonal temperatures increased the rate of monochloramine dissipation increased until effluent PDS residuals were zero. PDSs effluent water quality parameters chloramines residual, dissolved oxygen, heterotrophic plate counts (HPCs), pH, alkalinity, and nitrogen species were monitored and found to vary as expected by stoichiometry associated with theoretical biological reactions excepting alkalinity. Nitrification was confirmed in the PDSs. The occurrence in the PDSs was not isolated to any particular source water. Ammonia for nitrification came from degraded chloramines, which was common among all finished waters. Consistent with nitrification trends of dissolved oxygen consumption, ammonia consumption, nitrite and nitrate production were clearly observed in the PDSs bulk water quality profiles. Trends of pH and alkalinity were less apparent. To control nitrification: residual was increased to 4.5 mg/L as Cl2 at 5:1 Cl2:NH3-N dosing ratio, and the HRT was reduced from 5 to 2 days. Elimination of the nitrification episode was achieved after a 1 week free chlorine burn.

The ban on lead plumbing materials in the Safe Drinking Water Act (1986) and the EPA Lead and Copper Rule (1991) have successfully reduced lead contamination of potable water supplies. The success of these regulations gave rise to a belief that serious lead contamination was an important past problem that had been solved, and that additional fundamental research was therefore unnecessary. This work carefully re-examined the lead contamination issue from the perspective of 1) new regulations causing a shift from chlorine to chloramine disinfectant, 2) assumptions guiding sampling strategies, 3) existing performance standards for brass, and 4) galvanically driven corrosion of lead bearing plumbing materials. The results were instrumental in uncovering and understanding a serious problem with lead contamination in Washington, D.C. A critical reading of the literature indicates that chloramines can accelerate corrosion of lead bearing materials and increase lead contamination of water. When a new sampling protocol was conceived and used in Washington homes to assess the nature of the problem, hazardous levels of lead were found to be present in some drinking water samples. Contrary to the conventional wisdom, lead was not always highest in first draw samples, but often increased with flushing. This has several important implications for monitoring and public health. For instance, well-intentioned public education materials were causing consumers to drink water containing very high levels of lead in some circumstances. Laboratory and field-testing proved that chloramines were causing serious lead corrosion problems. That testing also discovered that, unbeknownst to scientists and utilities, free chlorine itself can act as a corrosion inhibitor, reducing lead solubility and contamination of water. The net result is that changing disinfectant from free chlorine to chloramine can sometimes trigger serious lead contamination of water. While the worst problems with lead in Washington, D.C. came from the lead services, significant levels of lead were occasionally sampled from homes with solders or brass as the lead source. This prompted re-evaluation of the ANSI/NSF 61, Section 8 standard, which is relied on to protect public health from in-line brass plumbing devices that might leach excessive lead to potable water. In-depth study of the standard revealed serious flaws arising from use of a phosphate buffer in the test waters and a failure to control carbonate dissolution from the atmosphere. Due to these deficiencies, small devices made of pure lead could actually pass the performance test. The public therefore has no assurance that devices passing NSF Section 8 testing are safe and reforms to the standard are obviously needed. Other problems arise from connecting copper pipe to lead bearing plumbing in practice. The copper is cathodic and dramatically accelerates corrosion of the lead anode via a galvanic current. Corrosion and hydrolysis of released Pb²⁺ can lower pH near the surface of the lead and increase its solubility. A similar galvanic effect can arise from cupric ions present in the water via deposition corrosion mechanism. In cases where part of a lead service line is replaced by copper pipe, the galvanic corrosion effect can create a serious long-term problem with lead contamination. Such partial lead service line replacements are occurring in many US cities and the practice should be stopped. Lead contamination of potable water is not only a problem of the past but also of the present. While additional research is necessary before regulators, utilities and homeowners can anticipate and mitigate such problems with confidence, this work provides sound fundamental basis for future progress. / Master of Science

Normal ranges of values for hematological parameters of bluegill gathered seasonally from three lakes were determined. Sexual, seasonal, and inter-lake variations were found. Effects of 2-wk exposure to turbidity on blood parameters included an increase in rbc size and a decrease in small lymphocytes. Effects of 3-hr exposure were increases in rbc count, hemoglobin, and pH and decreases in PG2 and large lymphocytes. The effects of 0.44 and 0.88 ppm chloramines were an increase in blood pH, a decrease in MEV, and severe spastic reactions resulting in loss of equilibrium or death in 90% of the fish. Effects of Flexibacter columnaris included an increase in transformed lymphocytes and a decrease in small lymphocytes.

<div>Polyamide based reverse osmosis (PA-RO) membranes are applied for the desalination of halide-containing waters such as seawater and brackish groundwater. They are the industry standard because of their high selectivity and ability to withstand a wide range of pH. However, one of their pitfalls is their propensity to undergo biofouling, which is deterioration due to biological growth. Biofouling is known to dramatically decrease membrane performance and increase energy consumption. In order to overcome biofouling, a disinfectant, typically free chlorine, is applied; however, free chlorine is known to react with the polyamide layer and result in further membrane deterioration and performance loss.<br></div><div>One topic that has garnered less attention is the application of chloramines and their interactions with the PA-RO membrane when applied as a biofouling control. Furthermore, the role of halides (e.g. chloride, bromide, and iodide) in the presence of chloramines must be further explored because they are known to react to form secondary species which are reactive toward PA-RO membranes. In Chapter 2, the PA based monomers benzanilide (BA) and N-Methyl-N-phenylbenzamide (N-CH₃-BA) were used to model the PA layer. Monomers were exposed to halide containing waters and chloraminated with pre-formed NH₂Cl over a wide range of pH. The decay and by-product formation after exposure were evaluated using HPLC-DAD, LC/MS, and/or GC/MS. Results indicated that pH of the system and bromide concentration controlled parent compound decay and brominated by-product formation, where low pH and high bromide concentrations led to the highest formation of brominated by-products.</div><div>In Chapter 3, commercially made PA-RO membranes (SWC4-LD) were chloraminated or chlorinated with and without halides over a wide pH range. Their performance was evaluated after exposure through flux experiments using a dead-end flow cell. Results indicated that exposure to free chlorine led to the greatest change in flux and monochloramine resulted in the smallest change in flux. During chloramination of the membranes, the reactors containing bromide led to further change in flux than the chloramine only conditions. This was likely due to formation of secondary species that were reactive toward the PA membrane. Furthermore, Chapter 4 summarizes overall research contributions from this work and proposes future work pertaining to this topic.</div>

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