Economical evaluation for the improvement strategy of drinking water quality by advanced water treatment in Greter Kaohsiung District

The purposes of this study include: (1) investigating the reasons why drinking water quality degrades during transportation in the distribution system and developing an easy and effective tool to evaluate the status of distribution system; (2) investigating residents¡¦ satisfaction with advanced treated drinking water. It is found that the main reason of drinking water degradation is that most people don¡¦t flush the drinking water storage facilities routinely. It is also found that although most respondents are satisfied with advanced treated drinking water, nearly 40% of local residents still buy bottle water instead of drinking tap water. Therefore, Taiwan Water Supply Corp. (TWSC) should let people know the importance of flushing water storage facilities routinely and what TWSC has done to improve drinking water quality. The LSI (Langelier Saturation Index) of most water samples is negative, which means that the drinking water is corrosive when too much hardness is removed to comply with the regulations. A simple, efficient and cost-effective method is developed to provide TWSC sufficient information to solve the problems regarding water quality degradations in distribution systems. By using contour maps of different water quality parameters, TWSC can easily identifies locations with potential problems and easily assesses the necessity and appropriate locations of building re-chlorination stations, even though the lack of information regarding pipeline material, hydraulic conditions, thickness of biofilm¡Ketc.

ABSTRACT SULPHATE REMOVAL BY NANOFILTRATION FROM WATER Karabacak, Asli M.Sc., Department of Environmental Engineering Supervisor: Prof. Dr. &Uuml / lk&uuml / Yetis Co-advisor: Prof. Dr. Mehmet Kitis December 2010, 152 pages Excess sulphate in drinking water poses a problem due to adverse effects on human health and also due to aesthetic reasons. This study examines the nanofiltration (NF) of sulphate in surface water using a laboratory cross-flow device in total recycle mode. In the study, three NF membranes, namely DK-NF, DL-NF and NF-270, are used. The influence of the main operating conditions (transmembrane pressure, tangential velocity and membrane type) on the steady-state permeates fluxes and the retention of sulphate are evaluated. Kizilirmak River water is used as the raw water sample. During the experimental studies, the performance of NF is assessed in terms of the parameters of UVA254, sulphate, TOC and conductivity of the feed and permeates waters. Results indicated that NF could reduce sulphate levels in the surface water to a level below the guideline values, with a removal efficiency of around 98% with all three membranes. DK-NF and NF-270 membranes showed fouling when the surface water was fed directly to the system without any pre-treatment. MF was found to be an effective pretreatment option for the prevention of the membrane fouling, but no further removal of sulphate was achieved. Parametric study was also conducted. No change in flux values and in the removal of sulphate was observed when the crossflow velocity was lowered. The flux values were decreased as the transmembrane pressure was lowered / however there were not any decrease in the sulphate removal efficiency.

One of the most toxic environmentally mobile compounds found in water is arsenic. It has been used as a pesticide to control insects, fungi, weeds and rodents since the early part of this century because of its high toxicity. Sorption of toxic metals onto a metal oxy-hydroxide is the most popular and practical arsenic removal method from contaminated water. Water treatment with oxy-hydroxides creates arsenic containing residuals, which are usually disposed of in landfills. To prevent leaching, stabilization of the solid residuals is required. It has been reported that calcium may inhibit arsenic desorption and/or benefit arsenic sorption. The objective of this investigation is to assess arsenic leaching in the presence of calcium and phosphate ions at extreme pH. Two hypotheses have been identified to explain the decrease in soluble arsenic in the presence of calcium. One explanation is that arsenic reacts with calcium to form calcium arsenic solids. The second hypothesis is that calcium affects the surface properties of the oxy-hydroxide solid in solution. Results show that calcium enhances the removal by iron oxides and prevents the leaching of arsenic from the residuals. Isotherm experiments show that arsenic adsorption can be described as occurring on nonporous powders or powders with pore diameters larger than micro-pores. Physically, with increase in adsorbate concentration, second and more layers are completed until saturation when the numbers of adsorbed layers becomes infinite. Further, experimental data were fitted to a Brunauer, Emmett and Teller isotherm (BET) model which assumes the initial layer can act as substrate for further adsorption. Finally, calcium-arsenic and calcium-phosphate solids were predicted to be formed by Visual MINTEQ modeling program. Nevertheless, from the x-ray diffraction output calcium-arsenic or calcium-phosphate solids were not identified. Because no calcium arsenate solids were found it was concluded that calcium affects the surface properties of the oxy-hydroxide solids in solution. Increasing the pH produces negative surface charge, which in turn increases repulsion between the negatively charged hydrated arsenate ions and the Fe(OH)3 surface. Calcium’s positive charge might neutralize this effect enhancing the sorption of arsenic onto the oxy-hydroxide. Also, it was concluded that the competition between arsenic and phosphate was reduced by the same mechanisms.

<p>The existence of trihalomethanes (THMs) in a drinking water plant of Nicaragua has been investigated in order to see whether the concentration exceeded the maximum contaminant level recommended by the environmental protection agency of the United States (USEPA) and the Nicaragua guidelines. The influence of pH, temperature, chlorine dose and contact time on the formation of THMs were studied. The contents of organic matter measured by surrogate parameters such as total organic carbon, dissolved organic carbon, ultraviolet absorbance and specific ultraviolet absorbance were also determined in order to show which type of organic matter is most reactive with chlorine to form THMs. Models developed by other researchers to predict the formation of trihalomethanes were tested to see whether they can be used to estimate the trihalomethane concentration. In addition, empirical models were development to predict the THM concentration of the drinking water plant analysed. The raw water was treated by conventional and enhanced coagulation and these processes were compared with regard to the removal of natural organic matter (NOM). The significance of the results was assessed using statistic procedures.</p><p>The average concentration of THMs found at the facility is below the USEPA and Nicaragua guideline values. Nevertheless the maximum contaminant level set by USEPA is sometimes exceeded in the rainy season when the raw water is rich in humic substances. Comparison between the water treated by conventional and enhanced coagulation shows that enhanced coagulation considerably diminished the trihalomethane formation and the value after enhanced coagulation never exceeded the guidelines. This is because enhanced coagulation considerably decreases the organic matter due to the high coagulant dose applied. The study of the trihalomethane formation when varying pH, time, temperature and chlorine dose using water treated by conventional and enhanced coagulation showed that higher doses of chlorine, higher pH, higher temperature and a longer time increases the formation of THMs. However, combinations of two and three factors are the opposite. The predicted THM formation equations cannot be used for the water at this facility, since the results shown that the measured THM differs significantly from the THM concentration predicted. Two empirical models were developed from the data for enhanced coagulation, using linear and non-linear regression. These models were tested using the database obtained with conventional coagulation. The non-linear model was shown to be able to predict the formation of THMs in the Boaco drinking water plant.</p>

<p>Ronneby Miljö- och hälsoskyddskontor ville genom undersökningen få information om nitrathalter i</p><p>enskilda dricksvattenbrunnar inom kommunen, med bakgrund av den nya miljökvalitetsnormen.</p><p>Riktvärdet för nitrat är 50 mg/l. Halter som överstiger detta bör inte ges till barn under ett års ålder på</p><p>grund av risk för methemoglobinemi. Jämförelsen skulle ske mellan områden präglade av jordbruk</p><p>respektive skogsbruk, samt mellan grävda och borrade brunnar. Jämförelsen skulle även ske över tiden,</p><p>mellan 1975-1990 till 2005. Urvalet av provtagningspunkter baserades på en sammanställning från</p><p>befintligt arkiv samt efter en annons i dagspressen. Sammanställning av resultaten har gjorts i</p><p>tabellform. Det framkommer av undersökningen att grävda och borrade brunnar uppvisar det</p><p>förväntande resultatet: de grävda brunnarna svarar för en högre halt av nitrat samt att nitrathalterna har</p><p>ökat under tidsperioden. För de borrade brunnarna är resultatet det omvända. Medan områden präglade</p><p>av skogsbruk samt jordbruk inte har erhållit det förväntade resultatet. Jordbruket uppvisar en minskning</p><p>av nitrathalterna medan skogsbruket har fått en förhöjd nitrathalt. En trolig orsak till de förhöjda</p><p>nitrathalterna kan vara hästhållningen. Samt att deposition av olika kväveföreningar förekommer.</p> / <p>The environment protection and public health department in Ronneby wanted to have a study of nitrate</p><p>concentrations in private water supply. The reason is a new environmental quality standard.</p><p>The contaminant level for nitrate is 50 mg/l. Water containing excessive amounts of nitrate should not</p><p>be given to infant with age under one year. It could cause a disease called methemoglobinemia. The</p><p>purpose of the study was to compare areas pervade of agriculture respectively forestry, and between</p><p>digged and drilled wells. The study was time dependent as well, from 1975 – 1990 until 2005.</p><p>The testing points were selected from existing archive and an advertisement in the local paper.</p><p>The results are shown in tabular forms. The study shows the expected result for digged and drilled</p><p>wells. The higher amount of nitrate is found in the digged wells, and the concentration of nitrate have</p><p>exceeded during time. For the drilled wells is the result the opposite. Areas pervade of forestry and</p><p>agriculture didn't achieve the expected result. Agriculture shows a decrease of the amount of nitrate and</p><p>forestry an increased amount of nitrate. The cause of increasing nitrate concentration is likely</p><p>dependent on changed animal husbandry, for example horse keeping. Another reason could be the</p><p>deposit of different nitrogen compounds.</p>

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 231-239). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 231-239). Also available on the Internet.

Source Water Protection (SWP) is recognized as the first barrier in the multi-barrier approach to reduce the risk of drinking water contamination. In Canada, provincial water agencies and municipalities lead most of the water management responsibility based on provincial regulations. However, SWP planning and implementation is variable across jurisdictions and influenced by different factors related to local capacity. Much of the water resources literature is focused on capacity-building limitations faced by small and rural water system operators. The purpose of this research is to investigate capacity-building limitations faced by metropolitan water system operators. Information from a questionnaire and document review in four selected Canadian metropolitan areas was gathered and analysed in this study. The results of this study show variability of SWP planning uptake as well as variability in approach toward SWP implementation. While large metropolitan areas may appear to possess ready access to financial capital, technical capability, and other forms of capacity to undertake SWP, the results of this research indicate the opposite. Metropolitan areas in Canada remain reliant on advanced water treatment and other engineering solutions to provide safe drinking water as opposed to SWP planning that invests in preventative measures through land use planning mechanisms. The results of this research contribute to the knowledge and understanding of SWP particularly as applied to metropolitan Canada.

The main goal of this research was to develop a mechanism-based model for photocatalytic disinfection of bacteria in water using suspended catalyst pthesiss in batch reactors. The photocatalytic disinfection process occurs as a semiconductor photocatalyst, most commonly titanium dioxide (TiO2), is irradiated with light of wavelength less than 380 nm to produce hydroxyl radicals and other highly reactive oxidants which can inactivate microorganisms. Photocatalytic disinfection involves a complex interaction of many fundamental mechanisms such as light absorption and scattering by semiconductor pthesiss, electrochemical surface reactions, and heterogeneous colloidal stability. Current models, based largely on chemical reacting systems, do not adequately account for these fundamental mechanisms. Even the Langmuir model developed for heterogeneous systems cannot describe the interactions of such large colloidal pthesiss. As a result, it is difficult to assess the combined effects of many important factors which go into the design of a photocatalytic disinfection system. A mechanistic modeling approach is desirable because it provides a framework to understand the influence of many important parameters on the disinfection process. It requires a description of the physical properties of the catalyst, the nature of the suspending electrolyte solution, the physical and chemical properties of the cell surface, and the energetic aspects that influence the interaction of the pthesiss. All these aspects are interrelated. While it is customary to envision the adsorption of reactants unto a catalyst surface, for photocatalytic disinfection involving suspended catalyst pthesiss, multiple catalyst pthesiss adhere to the bacterial surface. In this work a mechanistic model has been developed that simulates the effect of light intensity and catalyst concentration on the disinfection process. The simulations show good agreement with the experimental data for stable colloidal suspensions, that is, suspensions in which rapid aggregation of cells and TiO2 do not occur. Increased disinfection rates and high levels of inactivation can be achieved by maintaining a relatively low catalyst-to-microbe ratio while maximizing the light intensity. The influence of pH and ionic strength on the disinfection process have been included in the model, but these are only expected to be accurately predicted when the solution remains stable.