Removal of TOC and Disinfection By-product Precursors Using H2O2/VIS-UV Photo-oxidation and Biodegradation PDF Download

Author: Julie Mialaret Davis
Publisher:
ISBN:
Category : Biodegradation
Languages : en
Pages : 250

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Book Description

Author: Gerald E. Speitel
Publisher: American Water Works Association
ISBN: 0898679737
Category : Drinking water
Languages : en
Pages : 172

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Book Description

Author:
Publisher: DIANE Publishing
ISBN: 1422330001
Category :
Languages : en
Pages : 60

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Author: Erin Daugherty
Publisher:
ISBN:
Category : Water
Languages : en
Pages : 171

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Book Description
Disinfection byproducts are the result of reactions between natural organic matter (NOM) and a disinfectant. The formation and speciation of DBP formation is largely dependent on the disinfectant used and the natural organic matter (NOM) concentration and composition. This study examined the use of photocatalysis with titanium dioxide for the oxidation and removal of DBP precursors (NOM) and the inhibition of DBP formation. Water sources were collected from various points in the treatment process, treated with photocatalysis, and chlorinated to analyze the implications on total trihalomethane (TTHM) and the five haloacetic acids (HAA5) formations. The three sub-objectives for this study included: the comparison of enhanced and standard coagulation to photocatalysis for the removal of DBP precursors; the analysis of photocatalysis and characterization of organic matter using size exclusion chromatography and fluorescence spectroscopy and excitation-emission matrices; and the analysis of photocatalysis before GAC filtration. There were consistencies in the trends for each objective including reduced DBP precursors, measured as dissolved organic carbon DOC concentration and UV absorbance at 254 nm. Both of these parameters decreased with increased photocatalytic treatment and could be due in part to the adsorption to as well as the oxidation of NOM on the TiO2 surface. This resulted in lower THM and HAA concentrations at medium and high photocatalytic treatment levels. However, at no UV exposure and low photocatalytic treatment levels where oxidation reactions were inherently incomplete, there was an increase in THM and HAA formation potential, in most cases being significantly greater than those found in the raw water or control samples. The size exclusion chromatography (SEC) results suggest that photocatalysis preferentially degrades the higher molecular mass fraction of NOM releasing lower molecular mass (LMM) compounds that have not been completely oxidized. The molecular weight distributions could explain the THM and HAA formation potentials that decreased at the no UV exposure samples but increased at low photocatalytic treatment levels. The use of photocatalysis before GAC adsorption appears to increase bed life of the contactors; however, higher photocatalytic treatment levels have been shown to completely mineralize NOM and would therefore not require additional GAC adsorption after photocatalysis.

Author:
Publisher: DIANE Publishing
ISBN: 1422331792
Category :
Languages : en
Pages : 117

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Author: Remilekun Yetunde Adedapo
Publisher:
ISBN:
Category : Water
Languages : en
Pages : 216

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Book Description
As far back as the early 1900's when it was discovered that water could be a mode of transmitting diseases, chlorine was used to disinfect water. In the 1970's, the formation of disinfection by-products (DBPs) from the reaction of chlorine with natural organic matter was discovered. Since then there have been various studies on alternative disinfectants that could inactivate microorganisms and at the same time form less or no disinfection by-products. More recently the ultraviolet (UV) irradiation has been used to both disinfect and remove organic contaminants in drinking water. Though the use of UV irradiation has been found to be very effective in the inactivation of microorganisms, it does not provide a residual effect to maintain the water's microbial quality in the distribution system. Due to this, a secondary disinfectant such as chlorine has to be used to achieve microbial stability, suggesting that the formation of chlorination disinfection by-products would still occur but perhaps in different quantities and with different chemical species. In this research, the use of factorial experiments and single factor experiments were used to determine the effects of pH, alkalinity and UV-fluence (dose) on the formation of three classes of disinfection by-products; haloacetic acids (HAAs), haloacetonitriles (HANs) and trihalomethanes (THMs). These disinfection by-products were measured in water samples following post-UV chlorination and the UV treatment was either UV photolysis or UV/H2O2. From the factorial experiment results, treatment of synthetic water with UV/H2O2, an advanced oxidation process (AOP), produced fewer post-UV chlorination disinfection by-products (PCDBPs) than UV photolysis. For chlorinated PCDBPs, the percentage difference between UV photolysis and UV/H2O2 was 55, 65 and 38% for total HAAs (HAA9), total HANs (THANs) and total THMs (TTHMs) respectively. The percentage difference between UV photolysis and UV/H2O2 for brominated PCDBPs was 41 and 42% for HAA9 and TTHMs respectively. Both the use of pH and alkalinity proved to be factors that were significant in affecting the yields of the PCDBPs studied. Increases in alkalinity were found to increase the formation of PCDBPs in the treatment of synthetic water with UV/H2O2. Alkalinity had the opposite effect for PCDBP formed under UV photolysis conditions. Increases in pH always decreased the formation of PCDBPs. In the single factor experiments, haloacetic acid concentrations were unaffected as alkalinity was increased but dichloroacetonitrile and chloroform increased in concentration under treatment conditions of UV photolysis followed by chlorination. The UV/H2O2 treatment resulted in a decrease in concentration of the PCDBPs. In the pH studies, water samples were subjected only to the UV/H2O2 treatments and a reduction in concentration of PCDBPs occurred between pH 7 and 9.

Author: Vedat Uyak
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659428609
Category :
Languages : en
Pages : 164

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Book Description
Chlorination is the most commonly employed chemical disinfectant in drinking water treatment nowadays. However, several studies reported that chlorination of organic matter in fresh water resulted in formation of disinfection by-products (DBP). Because of concerns over the health effects of organic by-products of chlorination, the use of alternative disinfectants of chloramines, ozone, and chlorine dioxide as primary or secondary disinfection agents is increasing. However, each of these alternatives has also been shown to form its own set of DBP. Concerns regarding the potential health effects of DBP prompted several industrialized countries to develop a number of regu-lations. The disinfectant/disinfection by-product (D/DBP) regulation in United States of America (USA) has set maximum contaminant levels for trihalomethanes (THM) and haloacetic acids (HAA) of 80 and 60 ug/l, respectively.

Author: 梁幃杰
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: David William Hand
Publisher:
ISBN:
Category :
Languages : en
Pages : 410

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Book Description

Author: Harvey Wayne Sorensen (Jr.)
Publisher:
ISBN:
Category : Carcinogens
Languages : en
Pages : 244

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Book Description