Harvested rainwater is an alternative water resource that can be utilized to help meet the world's growing demand for fresh water. Although harvested rainwater is often considered to have adequate physical and chemical qualities, its microbial quality has been found lacking. This study sought to better understand the effect of common treatment processes on the quality of harvested rainwater for potable use by examining two treatment processes: (1) batch chlorination followed by filtration, and (2) filtration followed by ultraviolet (UV) irradiation. The batch chlorination studies used rainwater harvested from four pilot-scale roofs in Austin, Texas with different roofing materials: concrete tile, green, Galvalume[Trademark] metal, and asphalt-fiberglass shingle. Chlorine tends to react with natural organic matter and produce disinfection byproducts (e.g., trihalomethanes (THMs)) that are harmful to human health. Chlorinating rainwater harvested from the metal and concrete roofs achieved adequate disinfection (total coliforms less than 1 colony forming unit per 100 mL) without forming THMs that exceed the United States Environmental Protection Agency (USEPA) limit of 80 [mu]g/L for public water systems. Chlorinating rainwater harvested from the shingle roof achieved adequate disinfection but had the potential to form excessive THMs. Chlorinating rainwater harvested from the green roof, which had the highest concentration of dissolved organic carbon, did not achieve adequate disinfection and formed THMs that were four times higher than the USEPA limit. Filtering the chlorinated rainwater from every roofing material with a block activated carbon filter generally resulted in increased bacteria concentrations and decreased THM concentrations. To study the effect of UV irradiation, cistern-stored and treated rainwater were sampled from a full-scale residential system in Austin, Texas, where the owner uses rainwater as his primary potable water supply. UV irradiation at the full-scale system effectively disinfected rainwater when the turbidity and total coliform concentrations were low, but disinfection was compromised as these two parameters increased as the drought progressed in 2011 and the ambient temperature increased. This research suggests that under certain conditions, treatment by either chlorination or UV irradiation can improve the quality of harvested rainwater so that it conforms to drinking water standards for public water systems. / text

published_or_final_version / abstract / toc / Civil Engineering / Doctoral / Doctor of Philosophy

Mémoire (M.Ress.Renouv.)--Université du Québec, 1995. / Document électronique également accessible en format PDF. CaQCU

Impact of Sludge Volume and Water Quality on DBPs in a Full-Scale Water Works The goal of this research was to determine the role of settled sludge on the formation of disinfection by-products in a full-scale water treatment plant. The occurrence of disinfection by-products in chlorinated drinking water has become a major concern to treatment facilities in their effort to comply with strict regulations set by the United States Environmental Protection Agency. Water samples were tested for trihalomethanes and haloacetic acids at both ends of the sedimentation process to evaluate formation over the length of the basin. Sludge volume and other important water quality parameters were also measured at the time of sample collection. Statistical analyses were used to analyze contributions from the sludge and to determine influential factors leading to disinfection by-product formation. The treatment plant incorporated chlorine dioxide into the treatment process seasonally, and effects were evaluated. Predictive models were developed from the data to be used under various treatment methods. The models created for trihalomethanes and haloacetic acids require measurements of chlorine dose, reaction time, total organic carbon, pH, water temperature, and sludge volume. The models performed well in predicting actual trihalomethane and haloacetic acid concentrations and could serve as a valuable tool in the control of disinfection by-products. DBP Formation Potential of Settled Sludge in a Full-Scale Water Treatment Facility It is still a common occurrence for water treatment facilities to store sludge in sedimentation basins for extended periods, rather than relying on mechanical collection equipment. The goal of this research was to characterize contributions from settled sludge to the formation of disinfection by-products (DBPs), and determine whether continuous removal is essential in the control of DBPs. Samples were taken from top and bottom sludge layers in the sedimentation basin and water was extracted either by draining or centrifugation. The water was analyzed for trihalomethanes and haloacetic acids and water quality measurements were recorded. Concentrations of both DBPs were very high in top-layer sludge; trihalomethanes ranged from 321.5 μg/L to 568 μg/L and haloacetic acids ranged from 74.6 μg/L to 409.8 μg/L. Evidence of biodegradation was observed in the bottom-layer sludge. The water samples were dosed with 4 mg/L chlorine, the United States Environmental Protection Agency's maximum residual disinfectant level, to determine if further DBP formation was possible. The extracted water from the bottom-layer sludge was shown to form high trihalomethane concentrations when chlorinated, and haloacetic acid concentrations were observed to increase when samples from the top-layer sludge were chlorinated. / Master of Science

This research investigates organic polymers, inorganic coagulants and separate unit operations for their effect on the total tri-halogenated (TTHM) residuals in a finished water. The water samples utilized for this project were taken from a highly colored Central Florida potable water supply which is used by municipality which has a TTHM concentration in the finished water in excess of the proposed Federal limit. Results indicate that (1) organic polymers are not a significant source of THM precursors, (2) organic polymers, when used as a settling aid after coagulation in Jar tests, are an effective means of filtration for removing THM precursors, (3) THM residuals produced after coagulation increased directly with chlorination pH, (4) there was no significant difference in the THM precursor removal after coagulation for any coagulant tested and (5) coagulation removed a significant amount of THM precursor from the raw water.

In an effort to maintain compliance with current and future United States Environmental Protection Agency regulations governing haloacetic acids (HAAs) and trihalomethanes (THMs), the Blacksburg, Christiansburg, VPI (BCVPI) Water Authority in Radford, Virginia elected to eliminate prechlorination and replace it with preoxidation using chlorine dioxide (ClO2). Prior to full-scale application at the BCVPI Water Treatment Plant, jar testing was done to determine the effects of ClO2 on the formation of HAAs and THMs. Jar testing results showed a significant reduction in THM formation potential when 2.0 mg/L ClO2 was applied to raw water and chlorination was delayed. Chlorine dioxide doses less than 2.0 mg/L were statistically insignificant in the reduction of THM formation potentials below samples that were prechlorinated according to the BCVPI Water Treatment Plant's current practice. Likewise, ClO2 did not alter HAA formation potentials in such a way that statistical differences could be detected between ClO2 pretreatment and prechlorination, even at a dose of 2.0 mg/L ClO2. The two inorganic byproducts of ClO2, chlorite and chlorate, were also measured following jar tests. Chlorite concentrations increased with an increased ClO2 dose, but remained below 1.0 mg/L. Chlorate was formed in all jar-test samples. / Master of Science

No description available.

Eight natural waters from throughout the United States were subjected to different degrees of alum coagulation and activated carbon adsorption treatment (not in series). The concentration of trihalomethanes (THMs) formed by the reaction between the natural aquatic organics and doses of free chlorine were determined by gas chromatography at ten discrete time intervals over a total of 168 hours of reaction time. Since bromide ion concentration and temperature were held constant, and the chlorine dose was based on the final nonvolatile total organic carbon (NVTOC) concentration, THM formation was modeled with the independent variables: reaction time, pH, and a surrogate parameter for organic precursor. Several surrogate parameters were investigated to quantify the THM formation potential. A multiplicative surrogate (UV*TOC) representing the product of the NVTOC concentration and the UV adsorbance at 254 nm was found to be the best surrogate for activated carbon treated waters and was found to be approximately equivalent to NVTOC for alum treated waters. The THM formation was found to fit a two stage reaction with respect to reaction time; relatively rapid formation in the first eight hours followed by a slower formation from 24 to 168 hours. The data base was analyzed with a statistical software package that performs multiple linear regression analysis. Three types of models were developed: a linear model, a nonlinear model and a logarithm transform model. The models were checked for predictive accuracy by a number of methods including the examination of statistics from the regression analyses, scatterplots of predicted versus observed THM values, and the number of predicted values within 20% of the observed value. The logarithm transform model was found to be the best overall model, although other models were more accurate for specific applications as to reaction time or water type. Gel permeation chromatography (GPC) was employed to examine the molecular weight distribution of the aquatic organics in three of the eight waters and to determine the effects of alum coagulation and activated carbon adsorption on these distributions. In general, alum coagulation preferentially removed high molecular weight organics while activated carbon removed a broad spectrum of molecular weight organics.

Neste trabalho desenvolveu-se uma metodologia analítica para determinação do teor de trialometanos THMs em amostras de águas potáveis, utilizando a técnica de purga e armadilha acoplada à cromatografia a gás (GCPT). Os THMs são subprodutos da cloração da água que devem possuir um limite máximo de 100 μg.L-1 segundo a legislação brasileira, estes compostos são suspeitos carcinogênicos humanos com base em estudos em animais de laboratório. A técnica de purga e armadilha extrai eficientemente estes compostos da água e a separação no cromatógrafo a gás ocorre utilizando coluna de leve polaridade e detector por captura de elétrons. Este detector é seletivo e o mais sensível para estes compostos halogenados. A metodologia desenvolvida foi validada nos itens de: linearidade, seletividade, exatidão, precisão, limite de quantificação, limite de detecção e robustez. O limite de detecção para os THMs foi menor do que 0,5 μg.L-1. A exatidão e precisão foram adequadas para ensaios de compostos traços. As amostras de água potável foram coletadas na cidade de Suzano-SP, que pertence à região do Alto do Tietê, nesta região nas margens do rio a vegetação é predominante. Entre todos os THMs, o composto encontrado na água potável em maiores concentrações foi o clorofórmio onde os resultados quantitativos, utilizando esta metodologia apresentaram teores entre 15,9 à 111,0 μg.L-1 em águas potáveis. / This work shows an analytical methodology developed and optimized to determine trihalomethanes level THMs, in drinking water samples, using purge and trap coupled to gas chromatography (GC-PT). THMs are byproducts water chlorination, these compounds must have a maximum of 100 μg.L-1 under Brazilian law, due these compounds be suspected human carcinogens base on studies in laboratory animals. The technique of purge and trap efficiently extracts these compounds from water, and the gas chromatograph separates the THMs. The GC uses a light polarity column and electron capture detector. This detector is selective and more sensitive in the detection of these compounds. The methodology was validated in terms of: linearity, selectivity, accuracy, precision, quantification limit, detection limit and robustness. The detection limit was less than 0,5 μg.L-1. The accuracy and precision were adequate for testing the trace compounds. The drinking water samples were collected in the city of Suzano-SP, which belongs to Alto do Tietê, in this region lay Tietê river with predominant vegetation. The THMs compound found in drinking water at higher concentrations was chloroform where the spread of values found between 15,9 to 111,0 μg.L-1 in drinking water.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2018. / Trihalomethanes (THMs) are a group of four compounds that are formed, along with other disinfected by-products. This happens when chloride or other disinfectants are used to control microbial contamination in drinking water, which then reacts with natural organic or inorganic substances in water. Trihalomethanes are better known by their common names such as chloroform, bromodichloromethane, chlorodibromomethane and bromoform. These four compounds are known to be classified as cancer group B carcinogens (shown to cause cancer in laboratory animals). Trihalomethane levels tend to increase with pH, temperature, time and the level of “precursors" present. Precursors are known to be organic substances which react with chloride to form THMs. One significant way of reducing the amount of THMs in water is to eliminate or reduce chlorination before filtrations and reduce precursors. There are guideline limits for THMs in the SANS 241:2015 document, but they are not continuously monitored and their levels in natural water are not known. The aim of this study is to develop a rapid, fast and reliable liquid-liquid microextraction technique, to determine the presence of THMs in natural water sources. This study particularly focuses on different water sources e.g. river, underground, borehole and chlorinated water. Chlorinated water is the water that has been presumably treated for bacteria and fungus growth. The results that were obtained for chlorinated water are as follow, 10.120 μg/L − 11.654 μg/L for chloroform, 2.214 μg/L - 2.666 μg/L for bromodichloromethane, 0.819 μg/L − 0.895 μg/L chlorodibromomethane and 0.103 μg/L - 0.135 μg/L for bromoform from validation data. All these THMs concentrations have been found to be below the SANS 241:2015 limits. Natural water shows a very high affinity for chloroform. This is what is expected under normal conditions as chloroform is the most abundant THM of all THMs present in natural water. The liquid-liquid microextraction technique that was optimized and used for the determination of THMs in this study is a rapid, simple and inexpensive technique that provides low limits of detection (LOD) e.g. 0.1999 μg/L chlorodibromomethane and 0.2056 μg/L bromoform and wide dynamic range (LOQ) of 0.6664 μg/L chlorodibromomethane and 0.6854 μg/L bromoform for the determination of THMs.