Chlorination By-products Research Articles

Exposure to Drinking Water Chlorination by-Products and Fetal Growth and Prematurity: A Nationwide Register-Based Prospective Study.

Background:Chlorination is globally used to produce of safe drinking water. Chlorination by-products are easily formed, and there are indications that these are associated with adverse reproductive outcomes.Objectives:We conducted a nationwide register-based prospective study to assess whether gestational exposure to the four most common chlorination by-products [total trihalomethanes (TTHMs)] via tap water was associated with risk of small for gestational age (SGA), preterm delivery, and very preterm delivery. To date, this is one of the largest studies assessing drinking water TTHM-associated adverse reproductive outcomes.Methods:We included all singleton births 2005–2015 (live and stillbirths) of mothers residing in Swedish localities having inhabitants, operating waterworks, adequate information on chlorination treatment, and a sufficient number of routine TTHM measurements in tap water. Individual maternal second and third trimester exposure was obtained by linking TTHM measurements to residential history, categorized into no chlorination, , 5–15, and TTHM/L. Outcomes and covariates were obtained via the linkage to Swedish health and administrative registers. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression using inverse probability weighting. We stratified the analyses by chlorination treatment (chloramine, hypochlorite).Results:Based on approximately 500,000 births, we observed a TTHM dose-dependent association with increased risk of SGA, confined to treatment with hypochlorite, corresponding to a multivariable-adjusted (95% CI: 1.08, 1.33) comparing drinking water TTHM to the unexposed. Similar results were obtained when, instead of unexposed, the lowest exposure category ( TTHM) was used as reference. No clear associations were observed for preterm delivery and very preterm delivery.Discussion:Chlorination by-products exposure via drinking water was associated with increased risk of SGA in areas with hypochlorite treatment. https://doi.org/10.1289/EHP6012

Effective blockage of chloride ion quenching and chlorinated by-product generation in photocatalytic wastewater treatment

Photocatalytic degradation of pollutants in high salinity wastewater usually shows extremely low activities and produces highly toxic by-products, often related to the presence of excess chloride ion (Cl−). Herein, we report for the first time that involvement of Cl− (quenching active species and generating chlorinated by-products) could be effectively blocked during photocatalytic processes. Based on a comprehensive investigation of its mechanism, we found that Cl− could quench superoxide radicals (O2−) through a cyclic indirect quenching model with holes (h+) and hydroxyl radicals (OH) quenching as "initiators". Thus, scavenging h+ and OH could successfully block the chain reactions between Cl− and O2−, and photocatalytic degradation of methyl orange (a refractory dye, with O2− as dominant attacking species) could be enhanced by nearly 50 times, even when Cl− content was up to 10 wt%. More importantly, both HPLC-MS analyses and DFT calculation validated that, by blocking its quenching effect, Cl− could be successfully excluded from the pollutant degradation processes, thus preventing the generation of toxic chlorinated by-products. This work provides new insights into control of chlorinated by-products and proposes feasible strategies to extend photocatalytic technology in high salinity wastewater.

Effect of organic load on the efficacy of activated persulfate in inactivating Escherichia coli O157:H7 and the production of halogenated by-products

Activated persulfate is highly effective in inactivating foodborne pathogens. There is great potential to use this chemical in fresh produce sanitation. The present study evaluated the potential effect of organic load in fresh produce wash water on the bactericidal efficacy of activated persulfate. Romaine lettuce, iceberg lettuce, strawberries, and grapes were used to prepare the produce extracts which were later diluted with water to simulate produce wash water containing different levels of organic matters, represented by the Chemical Oxygen Demand (COD, 100–2000 mg/L). Ferrous activated persulfate (PS/Fe2+) and alkaline activated persulfate (PS/OH−) were prepared in simulated wash water. A five-strain cocktail of Escherichia coli O157:H7 was added to the activated persulfate solution and treated for 2 min. Water properties, including COD, phenolics, protein content, UV254 absorbance, turbidity, pH, and oxidation reduction potential (ORP), were measured and correlated to the microbial reductions. Trihalomethanes, one of the major types of chlorinated disinfection byproducts, were also monitored. Romaine lettuce inoculated with E. coli O157:H7 was used to validate the organic load effect. The results showed that the organic loads in wash water significantly reduced the effectiveness of bacterial inactivation. The microbial reduction decreased from over 8.0 log CFU/mL to near 2.0 log CFU/mL. The organic load had a significantly larger effect on PS/Fe2+ than on PS/OH−. Based on the correlation coefficients, COD, phenolics, and UV254 were found to be the major indicators to predict the organic load effect. However, since UV254 measurement was quicker, UV254 was used as the primary indicator for real produce (romaine lettuce) application. When UV254 was adjusted to 0.75 in the simulated wash water, lower reductions of E. coli O157:H7 on romaine lettuce and higher cross-contamination potentials were observed during washing with PS/Fe2+, PS/OH−, and NaOCl as compared with the lettuce in wash water without additional organic load. In addition, no significant amount of THMs was generated in simulated wash water spiked with produce extracts during activated persulfate treatment. In conclusion, to maintain a high efficacy of activated persulfate for fresh produce washing, the organic load of wash water must be carefully monitored. Activated persulfate is advantageous to traditional chlorine sanitizers as no toxic chlorinated disinfection by-products will be generated.

Estimating Trihalomethane Concentrations in Bottled Spring Water

The chlorination of water has led to a substantial reduction in waterborne disease outbreaks. There are, however, concerns regarding the safety of trihalomethanes (major by-products of chlorination). One of the limitations of much of the existing evidence is the lack of individual trihalomethane exposure estimates, and these estimates should include the concentration of trihalomethanes in bottled water. In Australia, water advertised as ‘spring’ or ‘mineral’ water should, by definition, remain untreated, and should not, therefore, contain any trihalomethanes. We tested this assumption by assessing the concentration of trihalomethanes (bromodichloromethane, bromoform, chloroform, dibromochloromethane, and total trihalomethanes) in the six brands of bottled spring water most commonly consumed by pregnant women in Australia (here labelled A–F). For each water brand, two bottles were purchased from five locations, and this procedure was replicated approximately 2 weeks later. Standard water analysis techniques were used to determine the concentrations of bromodichloromethane, bromoform, chloroform, dibromochloromethane, and total trihalomethanes in each bottle. All 10 samples of brands A and B were positive for trihalomethanes, as was one bottle of brand C. No trihalomethanes were detected in any of the samples of the remaining three brands (D–F). The highest recorded total trihalomethane concentration was 30 µg/L. The trihalomethane concentration in Australian bottled spring water cannot be assumed to be zero. Studies estimating trihalomethane exposures should, therefore, collect data on the brand of the bottled water consumed, and test these brands contemporaneously for their trihalomethane exposures, to strengthen the evidence regarding trihalomethane exposure and human health outcomes.

Disinfection performance and mechanism of the carbon fiber-based flow-through electrode system (FES) towards Gram-negative and Gram-positive bacteria

The disinfection performance of a carbon fiber-based flow-through electrode system (FES) towards Gram-negative bacteria (Escherichia coli and fecal coliform) and Gram-positive bacteria (Enterococcus faecalis and Bacillus subtilis) in normal saline was systematically investigated over a wide range of applied voltages (1–5 V) and hydraulic retention times (HRTs) (1–10 s). It was revealed that the Gram-negative bacteria were more vulnerable to FES for their thinner cell walls, and over 6.5 log removal (no live bacteria detected) was achieved at the applied voltage of 2 V and HRT of 2 s; while Gram-positive bacteria were inactivated at slightly higher voltages (3 V, 2 s) or longer HRTs (2 V, 5 s). Bacterial inactivation was attributed to the change and rupture of cell membrane mainly by anode direct oxidation without bacterial regrowth/reactivation. In addition, negligible generation of the free chlorine at low voltages (≤2 V) can avoid the formation of potential chlorinated disinfection byproducts (DBPs). Hence, FES can offer a potential alternative to conventional disinfection methods for bacterial inactivation in natural and contaminated water.

Fate of natural organic matter and oxidation/disinfection by-products formation at a full-scale drinking water treatment plant

ABSTRACT This paper investigates the fate of natural organic matter (NOM) during the full-scale drinking water treatment plant supplied by Danube river bank filtration. After the recent reconstruction of the plant, special attention was devoted to the effects of ozone dose and granulated activated carbon (GAC) filtration on the formation and behaviour of oxidation by-products (carbonyl compounds and bromate), as well as carbonaceous and nitrogenous chlorination by-products. For the oxidation of aromatic NOM moieties that absorb light at UV254, a lower ozone dose (1.0 g O3/m3) is sufficient, whereas to achieve a measurable reduction (about 20%) of total organic carbon, an ozone dose of 1.5 g O3/m3 is required. The content of carbonyl compounds in the water after ozonation increases relative to the content before oxidation treatment, and is up to 12 times higher in the case of aldehydes and up to 2 times higher in the case of carboxylic acids. Seasonal variations, including changes in temperature and the amount of precipitation, were also shown to affect the content of organic matter in the raw water, with slight effects on the quality of the treated water. In the winter, the organic matter content is slightly higher, meaning their transformation products aldehydes and carboxylic acids, are also higher during the winter than the summer.

+Chlorination by-products in indoor swimming pools: Development of a pilot pool unit and impact of operating parameters

Chlorine addition in swimming pools ensures the microbiological quality of the water and the bathers’ safety. However, water chlorination is associated with disinfection byproducts (DBP) formation and adverse health effects. The impact of operating parameters and innovative water treatment systems on DBPs levels has been reported in several studies, but sampling campaign in real pools remain difficult to carry out, mainly due to unexpected attendance variations. This study presents the development of a pilot pool plant allowing to perform experiments under controlled and reproducible conditions. Bathers inputs were simulated both for the organic load and for the mechanical agitation of water. Two sampling campaigns were performed during the building of the pilot, before and after the hall was closed. Key operating parameters such as chlorine dose, water temperature and attendance were controlled and monitored. DBP levels in the pilot plant were representative of French indoor swimming pools and the impact of bathers’ activity was visible on volatile DBPs. Furthermore, correlations could be stated between operating parameters and DBP levels. Stripping effectively reduced volatile DBP concentrations in water. Moreover, energy consumption data, which are usually very scarce in experimental studies, showed the influence of heat pump consumption on the global energy consumption.

Novel Chlorination Byproducts of Tryptophan: Initial High-Yield Transformation Products versus Small Molecule Disinfection Byproducts

Because of the difficulty of carbon–carbon bond cleavage needed to liberate the small molecule chlorine disinfection byproducts (DBPs; e.g., trihalomethanes), they typically form at <1% yields. By ...

Age-sex specific and cause-specific health risk and burden of disease induced by exposure to trihalomethanes (THMs) and haloacetic acids (HAAs) from drinking water: An assessment in four urban communities of Bushehr Province, Iran, 2017

Health risk and burden of disease induced by exposure to trihalomethanes (THMs, four compounds) and haloacetic acids (HAAs, 5 compounds) from drinking water through ingestion, dermal absorption, and inhalation routes were assessed based on one-year water quality monitoring in four urban communities (Bandar Deylam, Borazjan, Bushehr, and Choghadak) of Bushehr Province, Iran. The total average concentrations of THMs and HAAs at all the communities level were determined to be 92.9 ± 43.7 and 70.6 ± 26.5 μg/L, respectively. The dominant components of the THMs and HAAs were determined to be tribromomethane (TBM, 41.6%) and monobromoacetic acid (MBAA, 60.8%), respectively. The average contributions of ingestion, dermal absorption, and inhalation routes in exposure to the chlorination by-products (CBPs) were respectively 65.0, 15.4, and 19.6%. The total average non-carcinogenic risk as the hazard index (HI) and incremental lifetime cancer risk (ILCR) of the CBPs at all the communities level were found to be 4.03 × 10−1 and 3.16 × 10−4, respectively. The total attributable deaths, death rate (per 100,000 people), age-weighted disability-adjusted life years (DALYs), and age-weighted DALY rate for all ages both sexes combined at all the communities level were estimated to be 1.0 (uncertainty interval: UI 95% 0.3 to 2.8), 0.27 (0.08–0.75), 30.8 (11.3–100.1), and 8.1 (3.0–26.4), respectively. The average contribution of mortality (years of life lost due to premature mortality: YLLs) in the attributable burden of disease was 94.7% (94.4–95.6). Although in most of cases the average levels of the CBPs were in the permissible range of Iranian standards for drinking water quality, the average values of ILCRs as well as attributable burden of disease were not acceptable (the ILCRs were higher than the boundary limit of 10−5); therefore, implementation of interventions for reducing exposure to CBPs through drinking water especially in Kowsar Dam Water Treatment Plant is strictly recommended.

High activity of CeO2-TiO2 composites for deep oxidation of 1,2-dichloroethane

CeO2-TiO2 catalysts prepared by different methods were investigated for deep oxidation of 1,2-dichloroethane (DCE), as a typical representative of the chlorinated volatile organic compounds (CVOCs). Characterization analysis reveals that CeO2-TiO2 catalysts prepared by sol-gel and coprecipitation methods exhibit higher specific area, CeO2 and TiO2 particles are highly dispersed into each other and the reducibility and mobility of active oxygen species are obviously promoted due to the strong interaction between the two catalysts CeO2 and TiO2, resulting in higher catalytic activity for DCE oxidation to and less chlorinated byproduct. The high calcination temperature would lead to the formation of a new monoclinic phase Ce0.3Ti0.7O2 and sintering, which is the main reason for the catalytic activity for DCE oxidation markedly decreases.

Assessment of drinking water quality along Port Said Canal treatment plants, Suez Canal corridor, Egypt

Port Said Canal is one of the man-made Nile branches in Egypt that gain its water supply via the Ismailia Canal. The canal extended parallel to the Suez Canal navigation route providing the surrounding region the necessary drinking and irrigation waters. The water treatment plants along the canal use the surface water as a crude supply without preliminary pre-filtration process, and chlorination is applied in two phases, which may impose some health hazards. The study aims to ensure that the finished water is safe to drink and meet the international drinking water regulations. The public water purification systems in four treatment plants along Port Said Canal were tested for their efficiency and chlorination by-products. Raw and treated waters in these plants were analyzed for organic, toxic, trace, and heavy elements. Flow measurements were implemented at five sections along the main canal course during the summer and the winter seasons. Results indicated that the treated water suffers from low filtering effectiveness and exceeds the drinking water standards for the trihalomethane species. Furthermore, the change of canal flow from influent to effluent conditions during the winter season increases the contaminants’ concentrations. Also, the heavy metal concentrations in the treated water samples from all treatment works were much higher than that of the raw water samples, especially for those higher in suspended particulate matter. The study proposed a better purification system including, sedimentation and gravel pre-filtration combined with slow sand filtration and underground water passage for the elimination of the existing pollution problems.

Efficient natural organic matter removal from water using nano-MgO coupled with microfiltration membrane separation

Excess natural organic matter (NOM) in water not only lead to unpleasant black color and dissolved oxygen depletion in wastewater and natural water body but also causes carcinogenic chlorinated organic byproduct during drinking water chlorine disinfection. We try to develop a novel cost-effective and green technology for water NOM removal. In our simulated NOM removal process using humic acid (HA) as typical organic matter, we find that mesoporous nano-MgO performs an abnormally high NOM removal capacity (1260 mg-HA/g-MgO, or 446 mgC/g-MgO) when coupled with microfiltration membrane separation, which can’t be illustrated by traditional adsorption mechanism. Actually, Mg2+ from dissolved Mg(OH)2 contributes ∼ 92% NOM removal via coagulation while Mg(OH)2 is responsible for the residue ∼ 8% via adsorption. MgO serves as a two-in-one coagulant and adsorbent. The MgO treatment process is highly pH sensitive and weak acidic condition is favored for high NOM removal efficiency. MgO can be regenerated for more than 10 circulations by annealing Mg(OH)2/Mg-NOM composite at 500 °C, so that our MgO recycling process will be sustainable without the need of continuous chemical purchase. More importantly, no solid waste is generated in this novel process. This MgO-recycling NOM-removal process is simple, efficient, and sustainable for water NOM removal and will be significant in promoting novel sustainable technologies for NOM- or HA-related water remediation and treatment while minimizing the generation of solid waste.

Evaluation of water quality through the distribution system in Cancún, Mexico

A water distribution system must maintain water quality throughout the entire network to guarantee public health. Although several studies have focused on changes in water quality along distribution systems, very few have evaluated the entire process from the water source to household containers. The aim of this study was to evaluate the effectiveness of bacteriological control and to determine the critical points of potential contamination along the distribution system in Cancún, Mexico. We addressed three aspects: 1) physicochemical and bacteriological analysis of water, 2) biochemical oxygen demand (BOD5) and nitrate-nitrite associated with organic matter, and 3) trihalometanes (THMs) as chlorine by-products from the disinfection process. The results showed that the water supply met the required quality standards in most parts of the distribution system but that there are critical points that could increase the risk of recontamination, specifically the geological setting and the critical aspects in irregular urban development in the area of water extraction. Mexico and any other country that relies on groundwater as a drinking water source must review and reinforce the regulations to protect areas with extraction wells and encourage the maintenance of containers to ensure water quality.

Associations between exposure to drinking water chlorination by-products and being born small or preterm - a nation-wide register-based prospective study including 500,000 singleton births

OPS 24: Drinking water contamination and children’s health, Room 411, Floor 4, August 27, 2019, 10:30 AM - 12:00 PM Background: Chlorination is used globally for the production of clean drinking water, but by-products such as trihalomethanes (THM) are easily formed. There are indications that chlorination by-products may increase the risk of some adverse reproductive outcomes, but results are inconsistent. We conducted a nation-wide register-based prospective study to assess whether gestational exposure to THM via drinking water was associated with risk of small-for-gestational-age (SGA), preterm birth (PTB) and very preterm birth (VPTB). Methods: We included all singleton births 2005-2015 of mothers residing in Swedish localities having >10,000 inhabitants, ≤ two operating water treatment plants, adequate information on chlorination procedures and sufficient number of routine THM measurements in tap water. Individual maternal exposure was obtained by linking THM measurements to residential history, categorized into no chlorination, <5, 5-15 and >15 µg THM/L. We also stratified by chlorination procedure. Outcomes and covariates were obtained via the linkage to Swedish health and administrative registers. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by logistic regression using inverse probability weighting. Results: Based on ~500,000 births and after full multivariable adjustment, we observed no clear association between THM exposure and risk of SGA based on all assessments. Stratifying by chlorination procedure revealed dose-dependent increased risk of SGA for hypochlorite (OR, 1.20; 95% CI, 1.08-1.33), comparing highest THM exposure with no chlorination, but not for monochloramine. For PTD and VPTD, we observed ORs 0.94 (95% CI, 0.88-1.00) and 0.83 (95% CI, 0.70-0.98), respectively comparing highest THM exposure with no chlorination. Conclusions: This is one of the largest studies assessing drinking water THM-associated adverse reproductive outcomes and we were able to consider time-specific windows of exposure and all relevant individual confounders. After considering the chlorination procedure we observed indications of increased risk of SGA which occurred at a lower exposure than previously observed.

Contaminant signatures and stable isotope values qualify European conger (Conger conger) as a pertinent bioindicator to identify marine contaminant sources and pathways

To evaluate the capacity of the European conger (Conger conger) as a reliable bioindicator to investigate marine contaminant sources and pathways, the muscles of 24 individuals caught in a semi-enclosed industrialized bay (Gulf of Fos, France) were analyzed for numerous organic compounds, metal elements, and stable isotopes. The contaminant levels were elevated to moderate, which relates to the great anthropic pressure from the surrounding industries and maritime traffic. Stable isotope analyses finely discriminated between three geographical areas and between two age groups. Mercury (Hg) and arsenic (As) concentrations (nd-1.35 mg.kg −1 and 5.94-60.1 mg.kg −1 wet weight (ww), respectively), as well as chlorination by-products, were elevated in particular areas, identifying specific industrial sources. Levels of Σ 42 PCB (7.15-28.67 µg.kg −1 ww), Σ 16 PAH (3.64-9.48 µg.kg −1 ww) and Σ 10 pesticides (1.91-18.42 µg.kg −1 ww) in fish muscles, as expected, did not differ among sites.

Accelerated oxidation of 2,4,6-trichlorophenol in Cu(II)/H2O2/Cl- system: A unique “halotolerant” Fenton-like process?

The roles of chloride in enhanced oxidative degradation of refractory organic pollutants are recently identified in the Cu(II)/H2O2/Cl− system, but the identity of the reactive oxidants and potential conversion of inorganic chloride to organochlorine in such oxidizing environment remain obscure. Here we report that Cu(II)/H2O2/Cl− system is a unique “halotolerant” Fenton-like process that works most efficiently in saline water among the five tested redox-active metals ions (i.e. Cr(VI), Ce(III), Co(II), Mn(II) and Cu(II)). The observed pseudo first-order rate constant for 2,4,6-trichlorophenol (TCP) degradation was linearly correlated with the elevated Cl− content. The TCP degradation rate at [Cl−]0 = 1000 mM by the Cu(II)/H2O2 system was approximately 46-fold higher than that at [Cl−]0 = 5 mM. The optimal mineralization rate of TCP and percentage of absorbable organic halogens (AOX) decrease were 31.6% and 63.8%, respectively, in the tested Cu(II)/H2O2/Cl− system. However, the detection of fused chlorinated byproducts (i.e. chloro-anthracene-pentaol, dioxine, chlorinated dibenzofuran) reminds us of cautiousness in evaluating the applicability of Cu(II)-catalyzed Fenton-like reaction, particularly while it is to be applied to the treatment of wastewater contaminated with chlorophenols. Two independent models (i.e. “Cu(III) model” and “OH model”) were developed to describe the kinetics of Cu(II)/H2O2/Cl− system. The failure of “OH model” to rationalize the observed AOX decay has disproved the “OH model” through reductio ad absurdum. The ability of “Cu(III) model” to adequately explain the experimental data demonstrates that Cu(III)-chloro complexes, rather than OH, is the major product resulting from reactions between Cu(I)-chloro complexes and H2O2 at neutral pH.

UV-LED/PMS preoxidation to control fouling caused by harmful marine algae in the UF pretreatment of seawater desalination

Preoxidation is gaining spotlight in the mitigation of ultrafiltration (UF) membrane fouling caused by algal organic matter (AOM). Although it is known to be beneficial in freshwater, its applicability in seawater treatment has barely been explored. This study first evaluated the effect of UV/permonosulfate (PMS) oxidation for UF process against marine harmful algal blooms (HAB). The transition of AOM released from Pseudo Nitzchia was investigated which produces a neurotoxin, domoic acid (DA). Specifically, UV light emitting diodes (LED) were employed as UV source. The results indicated UV-LED/PMS treatment effectively reduces the fouling potential of AOM. However, the participation of abundant chloride ions generated free chlorine and disinfection byproducts, thus, PMS addition below 0.5 mM was suggested for seawater applications. With respect to PMS 0.5 mM, TOC and cake layer resistance were reduced by 10% and 85%, respectively, and this was followed by significant improvements in water permeability, flux reversibility and permeate quality of UF process. Furthermore, PMS exhibited significant reactivity for decomposing DA achieving rapid disappearance of 1 ppm of DA within a minute. The aforementioned results encourage the use of PMS as a bulk oxidant in seawater treatment to simultaneously mitigate membrane fouling and improve permeate quality.

Formation of chlorination by-products in drinking water treatment plants using breakpoint chlorination

In drinking water treatment plants generally chlorination is applied for disinfection using Cl2, ClO2, or NaOCl reagents. In Hungary due to the relatively high ammonium ion concentration of source water originating from deep aquifiers, not only the disinfection but simultaneously the ammonium ion removal is also a crucial task to prevent the nitrite formation. For this purposes the breakpoint chlorination is used which needs approximately 10 times more chlorine than the disinfection resulting in enhanced formation of organic and inorganic by-products. Chlorination by-product formation was investigated in twelve drinking water treatment plants applying breakpoint chlorination. Trihalomethanes were detected in the highest concentration (14.7 μg/L to 143 μg/L), followed by haloacetic acids and haloacetonitriles. In 50% of the investigated water treatment plants, the concentration of trihalomethanes in finished water exceeded the Hungarian parametric value, but it was the same range as in water supplies using chlorine for disinfection. The concentration of trihalomethanes, haloacetic acids, haloacetonitriles and adsorbable organic halides in finished water was found to correlate with residual free chlorine (r > 0.5) and raw water temperature (r > 0.48). At high bromide concentration (cBr- > 0.2 mg/L) of the raw water the proportion of brominated by-products (trihalomethanes and haloacetic acids) increased up to 50%. Chlorate concentration was particularly high at drinking water treatment plants using hypochlorite (0.66–2.0 mg/L).By-products are mostly generated at breakpoint chlorination, but their additional formation within the water distribution system is also significant, especially where the concentration of free chlorine is high and the residence time is long. Elimination (potentially biodegradation) of haloacetic acids and haloacetonitriles was observed at several sampling sites. The efficiency of the granulated activated carbon filters in removing adsorbable organic halides, trihalomethanes and haloacetic acids amounted generally under 25%.

An efficient SnyMn1-yOx composite oxide catalyst for catalytic combustion of vinyl chloride emissions

A series of SnyMn1-yOx composite oxide catalysts with different Sn/Mn molar ratios (y = 1.0, 0.8, 0.6, 0.3 and 0) were prepared by a co-precipitation method. The catalysts were investigated for the catalytic combustion of vinyl chloride (VC), which is a typical chlorinated volatile organic compound (CVOC). It is found that the existence of Sn-Mn-O solid solution structure over SnyMn1-yOx catalysts can increase the specific surface area and tune the valence state of Mn and the surface properties. As a result, the redox property and the ability of adsorbing oxygen species of SnyMn1-yOx catalysts are enhanced. Meanwhile, more weak and medium acid sites are present on the catalyst surface. Under the synergetic effects of these above-mentioned factors, the catalytic activity of SnyMn1-yOx catalyst for VC oxidation is significantly improved compared with pure SnOx and MnOx catalysts. Moreover, the Sn/Mn molar ratio significantly affects the catalytic activity of SnyMn1-yOx catalysts, among which Sn0.6Mn0.4Ox catalyst possesses the best catalytic activity and excellent resistance to Cl poisoning and water-resisting ability. It can retain VC conversion of 100% without any chlorinated byproducts for 100 h at the reaction temperature of 340 °C.

Decomposition of β-N-methylamino-L-alanine (BMAA) and 2,4-diaminobutyric acid (DAB) during chlorination and consequent disinfection byproducts formation

β-N-methylamino-L-alanine (BMAA) and 2,4-diaminobutyric acid (DAB) are two newly identified algal toxins, and they may react with chlorine to undergo decomposition and generate disinfection byproducts (DBPs) during pre-chlorination as well as chlorine disinfection. In this study, the decomposition of BMAA and DAB during chlorination and the consequent DBPs formation were investigated. The BMAA and DAB concentrations in source waters were determined, the decomposition kinetics of BMAA and DAB and the formation of DBPs during chlorination were studied, the formation pathways of DBPs from BMAA and DAB were explored, and the factors which may affect the decomposition and DBPs formation were examined. The results revealed that BMAA and DAB were commonly detected in source waters from Taihu Lake, and the highest level of BMAA reached 230.8 ng/L, while the concentrations of DAB were generally around 2.0 ng/L. The decomposition of BMAA and DAB during chlorination both followed pseudo-first-order decay while the decomposition rate constant of DAB was significantly higher than that of BMAA. Trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetonitriles (HANs) were all generated during the chlorination of BMAA and DAB with relatively high yields. Notably, the THMs, HAAs, and HANs yields of each carbon atom from BMAA and DAB were significantly higher than that from other organic precursors, and the formation of HANs from DAB was significantly higher than that from BMAA. The formation pathways of DBPs from BMAA and DAB were tentatively proposed and verified through theoretical calculations. Of note, the proposed formation pathways of THMs and HAAs from BMAA were similar to that from DAB, while the proposed formation pathways of HANs from BMAA and DAB showed some differences. Chlorine dose, pH and temperature all affected the decomposition of BMAA and DAB and DBPs formation during chlorination.