Efficacy of Ozone to Reduce Chlorinated Disinfection By-Products in Quebec (Canada) Drinking Water Facilities

The impact of ozonation on the reduction of chlorinated disinfection by-products formation was investigated in 15 full-scale and lab-scale drinking water facilities of Québec (Canada). Total trihalomethanes (TTHM) and the sum of six haloacetic acids (HAA6) were measured after chlorination under uniform formation conditions (UFC). Results showed that before ozonation TTHM and HAA6 average concentrations were 89.4 and 45.3 μg/L, respectively. In full-scale ozonation conditions TTHM-UFC and HAA6-UFC reductions averaged respectively 27 and 32%. After lab-scale ozonation at a O₃/C of 1:1, a decrease of only 9% of TTHM was calculated, while for HAA6, reduction was not significantly impacted (30%). For BDOC, average concentrations of 0.13, 0.46, and 0.69 mg C/L were measured before and after and lab-scale ozonation, respectively. Chlorine demand (Cl₂D) and immediate ozone demand (IOD) were found to be the most appropriate indicators to evaluate NOM reactivity after ozonation.     

Effectiveness of Bio-Activated Carbon Filtration and Ozonation on Control of Halo Acetic Acids Formation during Chlorination of Ganga River Water at Kanpur,India

ABSTRACT

Chlorinated water from River Ganga is the main source of drinking water in Kanpur, India. But, this water contains a significant amount of disinfection by-products (DBPs) that include haloacetic acids (HAAs) as a major contributor, which pose a carcinogenic risk on long-term ingestion. Therefore, in order to control HAAs formation, different combinations of ozonation and bio-activated carbon filtration (BAC-filtration) were studied. The results elucidate that slight ozonation followed by BAC-filtration proved effective in reducing (75.8%) HAAs formation and meet the USEPA drinking standards. These findings open a path to explore cost-effective treatment techniques in continuous mode for safe drinking water.     

Chlorination by-products in surface water treatment process

Chlorine disinfection is carried out for the purpose of sterilization of microbes existing in drinking water. Chlorination may cause the formation of disinfection by-products (DBPs) by the reaction of free chlorine with humic substance in the water. In particular, the DBPs including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and haloketones exist in tap water. The US Environmental Protection Agency (US EPA) suggests 80 μg/L THMs and 60 μg/L HAAs as maximum contamination levels for drinking water. This study was performed to detect the level of DBPs in drinking water and to measure disinfection by-product formation potential (DBPFP) of raw water with four different properties. After 24 h of chlorination, the measured level of trihalomethane formation potential (THMFP), haloacetic acid formation potential, and haloacetonitrile formation potential ranged from 55.0 to 102.6 μg/L, from 9.1 to 23.6 μg/L, and from 10.3 to 33.6 μg/L, respectively. DBPFP was the highest at pH 7.0 and increased with the reaction time. Among the DBPFP, THMFP was detected more frequently than the others. In the treated water, DBPs were measured with a mean value of 47.0 μg/L. Chloroform, dichloroacetic acid, trichloroacetic acid, and dichloronitrile all known as hazardous compounds, were measured as major parts of DBPs.     

Using catalytic ozonation and biofiltration to decrease the formation of disinfection by-products

The effect of catalytic ozonation in a fluidized bed reactor (FBR) on the formation of individual disinfection by-products (DBPs) was investigated. A biofiltration column was used to evaluate the removal efficiency of biotreatment on DBP precursors. Dissolved organic carbon (DOC), simulated distribution system trihalomethanes (SDS THMs), and six simulated distribution system haloacetic acids (SDS HAA6) were monitored. The source water was polluted by domestic and agricultural effluents. Catalytic ozonation removed the concentration of DOC by 8.2-51.4% depending on the dosage of the catalyst. The decreases of SDS THMs and SDS HAA6 were 41.3-51.2% and 31.7-48.3%, respectively, under the same operating conditions. Biotreatment greatly improved the removal efficiency of DOC and decreased the formation of DBPs. Up to 81.7%, 76.1%, and 81.3% of DOC, SDS THMs precursors, and SDS HAA6 precursors were removed after the catalytic ozonation followed by biofiltration, respectively. The treatment processes also influenced the proportions of individual DBP species. The proportion of bromine-containing species from the SDS THMs and SDS HAA6 increased in water samples after being treated by biofiltration alone, ozonation alone, catalytic ozonation, and catalytic ozonation followed by biofiltration.     

饮用水处理中氯化消毒副产物三卤甲烷和卤代乙酸研究进展

三卤甲烷和卤代乙酸是饮用水氯化消毒的典型副产物。该文结合国内外学者对三卤甲烷和卤代乙酸的研究成果对这两类物质的形成的影响因素、主要检测方法及控制方法进行了总结。     

饮用水中消毒副产物的形成机理与控制技术研究

饮用水中消毒副产物主要存在形式为三卤甲烷类和卤乙酸类有机物。对饮用水中消毒副产物的形成机理及目前控制饮用水中消毒副产物的方法和特点进行了论述     

共存离子对饮用水中5种卤乙酸生成的影响

以腐殖酸作为天然水体中消毒副产物(DBPs)前体物,模拟了饮用水消毒过程。研究了水体中共存金属离子Ca2+、Mg2+、Cu2+、Al3+、Zn2+、Fe3+、Fe2+和非金属离子NH4+、As3+、F-等对饮用水氯消毒过程中5种卤乙酸(HAAs)包括一氯乙酸(MCAA)、一溴乙酸(MBAA),二氯乙酸(DCAA),三氯乙酸(TCAA)、二溴乙酸(DBAA)和总HAAs生成量的影响。结果表明,以上离子对5种HAAs和总HAAs生成量和含量分布均产生影响,但影响程度有所不同。除了水中F-在研究含量范围内对HAAs的生成影响不明显以外,Ca2+、Mg2+、Cu2+、NH4+、As3+等离子对HAAs总体上产生抑制作用,而Al3+、Zn2+、Fe3+、Fe2+等离子对HAAs的生成总体有促进作用。     

The Effect of Bromide Ion on the Formation of Organohalogen Disinfection By-products During Ozonation

Ozonation of water containing bromide ion (Br^?) leads to the formation of brominated disinfection byproducts (DBPs). The purpose of this study was to examine the influence of bromide ion upon the distribution and variation of organohalogen DBPs. Bromide ion concentration had a negative effect on chloroform formation as opposed to increased formation of brominated trihalomethanes (THMs). The results of factor analysis lead clearly to the interpretation that the bromide ion was strongly correlated with brominated THMs and less strongly with brominated HANs (haloacetonitriles). Compared to THMs and HANs, brominated HAAs (haloacetic acids) demonstrated a relatively weak correlation to bromide ion concentration. The addition of alkalinity enhanced the formation of chloroform when ozonation time was 10 to 30 minutes, while concentrations of other bromide ion-containing THMs decreased with increasing alkalinity.     

Optimization and Control of Ozonation Plant Using Raw Water Characterization Method

This study was undertaken to devise an innovative method for optimization and control of ozone dosage in drinking water ozonation treatment plants. The method is based upon a specifically-conceived analytical procedure, which can accurately measure the ozone decomposition rate. This was found to consist of two apparent phases: an instantaneous ozone demand (ID) phase and a relatively slower ozone decay (pseudo first-order rate constant, kc) phase. Those parameters, ID and kc were measured in a demonstration plant by the testing procedure in order to characterize raw water and process water, and utilized an Automatic Ozone Control Unit (ACU) to optimize preozonation (with parameter, ID) and postozonation (with parameter, kc).     

Influence of Preozonation on the Formation of Chlorination Disinfection By-products – A Case Study: The Úzquiza Reservoir Water

The influence of preozonation on the formation of chlorination disinfection by-products (DBPs) is studied for three different types of water: a natural water from the Úzquiza Reservoir (Burgos, Spain), synthetics waters prepared using natural fulvic and humic acids extracted from the Úzquiza Reservoir and a synthetic water prepared using a commercially supplied humic acid. The main factors intervening in this process have been reviewed: the delay time between ozonation and chlorination, the ozone reaction pathway, the type of NOM, the applied ozone dose and the presence of bromide ion. Preozonation decreases trihalomethane formation potential (THMFP) for both humic and fulvic acids, being this effect more significant for the humic acids. The molecular pathway of ozone seems to be more selective than the radical pathway for THMFP removal from humic acids. Ion bromide content of the raw water greatly influences the effect of preozonation on THMFP. The influence of preozonation on the formation of some minority DBPs has been studied too.     

Ozonation of Drinking Water: A Design Methodology

The formation of potentially carcinogenic organic halides has been shown to result from drinking water disinfection with chlorine. xidative treatment of organic halide precursors with ozone prior to chlorination has surfaced as an attractive technique for reducing the formation of these compounds. In addition to reduction of precursor levels, preozonation has been reported to effect other beneficial results in water treatment. This paper presents design methodologies to optimize the implementation of the ozonation process for water treatment applications. Pre-design considerations common to all ozonation design processes are discussed. Subsequently, design procedures for the ozone generation and contacting systems are reviewed.     

氯胺消毒对管网中消毒副产物的控制

相对氯消毒,氯胺具有消毒副产物生成量低的特点。本试验模拟管网,取典型的停留时间2d,考察了氯胺消毒时,pH和C12：N对管网中的消毒副产物（三卤甲烷和卤乙酸）浓度的影响。试验表明,消毒副产物的浓度及其含溴的程度基本上随着pH降低、C12：N升高而增大。试验条件下,氯胺生成的卤乙酸量大都高于三卤甲烷,并且以二卤乙酸为主,这和自由氯时所生成三卤甲烷多、卤乙酸以三卤乙酸为主的倾向正好相反。     

Using Fractionated Natural Organic Matter to Quantitate Organic Byproducts of Ozonation

An improved procedure was used to isolate and fractionate natural organic matter (NOM) in water for subsequent ozonation and disinfection by-product (DBP) and color removal quantisation. Isolated NOM fractions from two different sources, accounting for approximately 50 to 60% of the dissolved organic material and 60 to 75% of the color, were characterized and then ozonated under conditions approximating those encontered during drinking water treatment. The natural waters also were ozonated. Organic DBPs of either health concern or which may contribute to biological instability of finished water were investigated, including aldehydes, oxoacids and low molecular weight carboxylic acids. pH and ozone dosage were the parameters having the greatest effect on DBP formation. On the basis of UV absorbance measurements, the fulvic acid fractions studied taken together accurately represented the natural water and may be the primary sources of precursor material for aldehydes and oxoacid DBPs. However, as yet unidentified NOM fractions contribute significantly to carboxylic acid formation upon ozonation.     

Characteristics of Natural Organic Matter and Formation of Chlorinated Disinfection By-Products from Two Source Waters that Respond Differently to Ozonation

This study investigated the characteristics of natural organic matter (NOM) in two different raw surface water sources that respond differently to ozonation: one for which ozonation decreases the disinfection by-product (DBP) formation potentials (i.e., Capilano Reservoir, Vancouver, Canada), and one for which ozonation does not (i.e., South Thompson River, Kamloops, Canada); and evaluated the effect of ozonation on these characteristics and on the DBP formation potential of the different size and polar fractions of the NOM. Although the South Thompson River and the Capilano Reservoir waters had relatively similar total organic carbon concentrations, the characteristics of the NOM (e.g., size and polar distribution, specific UV absorption), in these water sources differed significantly. In general, no clear and consistent trend was observed with respect to the tendency of different size and polar fractions of NOM to generate DBPs. Nonetheless, the results from the present study suggest that hydrophobic NOM has a higher tendency to form DBPs. In addition, when considering individual size and polar fractions, specific UV absorption was a good overall indicator of the DBP formation potential for a given water source. The effect of ozonation on South Thompson River and Capilano Reservoir waters also differed significantly. For both source waters, ozonation appeared to have a greatest effect on the more hydrophilic fractions, generally increasing the DBP formation potential of the smaller more hydrophilic NOM, while generally decreasing that of the larger more hydrophilic NOM. The beneficial effect of ozonation on reducing haloacetic acid (HAA) formation potentials was due to a reduction in both the dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) formation potentials, while the negative effect of ozonation on increasing HAA formation potentials was due to an increase in the DCAA formation potentials. The results from the present study clearly indicate that the use of ozone as a primary disinfectant does not necessarily reduce the DBP formation potential of NOM in all water sources, further demonstrating the complex structure of NOM and the fact that NOM from different sources cannot be simply treated as one entity and compared with one another.     

The Effect of Bromide ion in Water Treatment. II. A Literature Review of Ozone and Bromide ion Interactions and the Formation of Organic Bromine Compounds

Where bromide ion is found in water used as a source of drinking water, and chlorination is used for disinfection, bromide ion is oxidized to bromine and can result in the formation of organic bromine compounds. There are presently no treatment techniques available for economic removal of bromide ion. A potential treatment strategy is to use an alternative oxidant; ozone is one such alternative. This review presents the reactions of ozone and bromide ion. Understanding of these reactions leads to possible treatment strategies when ozone is used, in the presence of bromide ion, to minimize the formation of trihalomethanes.     

Bromate in Drinking Water A problem in Switzerland?

Ozonation of bromide-containing waters causes the formation of bromate which is considered to be potentially carcinogenic. An investigation in Switzerland on water works using ozone (85) has shown that the new drinking water standard of 10?µg/L for bromate is generally not exceeded. This is mainly due to the relatively small bromide concentrations which are typically below 25?µg/L. There is a characteristic relationship between bromate formation and the ozone exposure in a particular water type. This can be used to estimate the integral ozone exposure from the bromate formation which allows the assessment of the efficiency of the disinfection. This new concept is illustrated by means of two examples.     

The Hydrozon-Kompakt Process-A New Method for Treatment and Disinfection of Swimming Pool and Bathing Water

The Hydrozon (R) Kompakt process (ozonation – sand filtration – bromination) relies on bromine (hypobromous acid/hypobromite ion) as the residual disinfectant in swimming pool and bathing water. As it performs its disinfection work, bromide ion is formed. Pool exit water is ozonized, not only to oxidize bather-added contaminants, but also to oxidize bromide ion back to hypobromous acid/hypobromite ions. Consequently, bromine is recycled in the pool water. However, the original process forms brominated hydrocarbons (brominated trihalomethanes), particularly bromoform, in excess of current German drinking water standards for total THMs (25 ug/L).     

The occurrence of bromate and perbromate on BDD anodes during electrolysis of aqueous systems containing bromide: first systematic experimental studies

Bromide electrolysis was carried out on laboratory-scale cells in the range of 1–1,005 mg [Br⁻] dm⁻³ using boron-doped diamond (BDD) anodes. These studies were part of fundamental research activities on drinking water electrolysis for disinfection. Synthetic water systems were mostly used in the experiments, which varied the temperature between 5 and 30 °C, the current density between 50 and 700 A m⁻², and the rotation rate of the rotating anode between 100 and 500 rpm (laminar regime). Hypobromite and bromate were found as by-products, as expected. Bromite was not detected. Higher bromate levels were formed at higher current density, but no clear relationship was observed between bromate concentration and the rotation rate or temperatures between 5 and 30 °C. Bromate yields higher than 90% were found at higher charge passed. Perbromate was found as a new potential synthesis or disinfection by-product (DBP), but no perbromate was detected at the lowest bromide concentrations and under drinking water conditions. The perbromate yield was about 1%, and somewhat lower when bromate was used as a starting material instead of bromide. At a temperature of 5 °C more perbromate was detected compared with experiments at 20°. Approximately 20 times more perchlorate was formed compared with perbromate formation in the presence of chloride ions of equimolar concentration. State of mechanistic considerations is presented and a mechanism for perbromate formation is proposed. The reaction from bromate to perbromate was found to be limited that is in contrast to the earlier studied chlorate-to-perchlorate conversion. In the measured concentration range, reduction processes at the mixed oxide cathode showed a much higher impact on the resulting concentration for perbromate than for bromate.     

Kinetics of the formation and decomposition of chlorination by-products in surface waters

The presence of organic chlorination by-products (CBPs) in drinking waters has caused great public health concerns. One of the most important factors affecting their formation during the disinfection procedure is reaction time. The kinetics of the formation of CBPs can be different for the different categories or species of compounds, depending also on the chlorine dose, organic matter content and the presence of bromide ion. Decomposition of some CBPs also occurs due to hydrolysis or reactions with residual chlorine. Therefore, the final concentrations of individual species of CBPs reaching the consumers’ tap may deviate from the predictions. The aim of the present investigation was the determination of formation or decomposition kinetics of CBPs during chlorination of natural waters. 24 CBPs were studied in chlorinated water from three different sources. Different speciation of CBPs and different formation rates were observed for different water quality regarding bromide ion presence and organic matter content. Decomposition of some CBPs occurred, specifically haloketones, BCA and DBA, after an initial formation step. The percentages of incorporation of chlorine and organic matter into CBPs indicated that other halogenated compounds not identified during the present study have also been formed during chlorination. The importance of chlorine dose for the formation of CBPs and for the incorporation of organic matter was highlighted. Moreover, linear correlations were observed between the concentrations of chloroform-MCA, chloroform-DCA and chloroform-TCA as well as between total THMs and total HAAs, in all waters studied.     

高铁酸盐控制饮用水中消毒副产物的研究进展

消毒是饮用水处理中特别重要的一步。随着工农业经济的飞速发展,水源中检测出大量种类复杂的有机污染物质,在消毒过程中这些有机物与消毒剂反应会产生一些对人体健康具有潜在危害的消毒副产物(DBPs),例如三卤甲烷、亚氯酸盐、溴酸盐等。因此,能否有效控制DBPs的产生成为了评价饮用水消毒质量效果的一项重要指标,而去除消毒副产物前体物是控制DBPs产生的关键。高铁酸盐作为一种绿色高效的新型水处理剂,具有强氧化还原能力,处理后的水中基本不会产生DBPs且能有效地抑制一些常见DBPs。文中综述常见的DBPs及前体物的种类、DBPs控制方法以及高铁酸盐在饮用水处理中对DBPs的控制。