Comparison of formation of disinfection by-products by chlorination and ozonation of wastewater effluents and their toxicity to Daphnia magna.

This study compared the two most frequently used disinfectants (i.e., chlorine and ozone) to understand their efficiency in wastewater effluents and the ecotoxicity of disinfection by-products created during chlorination and ozonation. Four trihalomethanes (THMs) and nine haloacetic acids (HAAs) were measured from a chlorine-disinfected sample and two aldehydes (i.e., formaldehydes and acetaldehydes) were analyzed after ozonation. Chlorination was effective for total coliform removal with Ct value in the range of 30-60 mg-min/L. Over 1.6 mg/L of ozone dose and 0.5 min of the contact time presented sufficient disinfection efficiency. The concentration of THMs increased with longer contact time (24 h), but that of HAAs showed little change with contact time. The measured concentration of formaldehyde at the ozone dose of 1.6 mg/L and the contact time of 9 min showed the greatest value in this study, approximately 330 µg L(-1), from which the corresponding ecotoxicity was determined using an indicator species, Daphnia magna. The ecotoxicity results were consistent with the toxicological features judged by occurrence, genotoxicity, and carcinogenicity. Both the disinfection efficiency as well as the DBP formation potential should therefore be considered to avoid harmful impacts on aquatic environments when a disinfection method is used for wastewater effluents.

Biologically active carbon filtration for haloacetic acid removal from swimming pool water.

A biologically activate carbon (BAC) filter was continuously operated on site for the treatment of haloacetic acids (HAAs) in an outdoor swimming pool at an average empty bed contact time (EBCT) of 5.8 min. Results showed that BAC filtration was a viable technology for direct removal of HAAs from the pool water with a nominal efficiency of 57.7% by the filter while the chlorine residuals were 1.71 ± 0.90 mg/L during the study. THMs and TOC were not removed and thus were not considered as indicators of the effectiveness of BAC filtration. Increased EBCT in the range of 4.5 and 6.4 min led to improved HAA removal performance, which could be best fit by a logarithmic regression model. BAC filtration also affected the HAA speciation by removing more dichloroacetic acid (DCAA) than trichloroacetic acid (TCAA), resulting in a lower ratio of DCAA/TCAA in the filtered effluent. However, the observation of an overall constant ratio could be attributable to a complex formation and degradation mechanism occurring in swimming pools.

Formation of haloacetonitriles and haloacetamides and their precursors during chlorination of secondary effluents.

The formation of dichloroacetonitrile (DCAN), dichloroacetamide (DCAcAm) and trichloroacetamide (TCAcAm) during chlorination of secondary effluents was evaluated under different conditions. The formation of DCAN and DCAcAm increased, then decreased with increasing contact time and chlorine dose, while TCAcAm formation increased continually, exceeding DCAcAm formation after a relatively long contact time or in response to a relatively high chlorine dose (20-80 mg L(-1)). Increasing the sample pH from 6 to 9 reduced the formation of DCAN and TCAcAm, while DCAcAm formation was highest at pH 8. Precursors in the secondary effluent were characterized by separating the organic matter into several fractions using membrane filtration and XAD resins and then measuring the formation of DCAN, DCAcAm and TCAcAm from each fraction during chlorination. Dissolved organic matter (DOM) with a molecular weight less than 1 kDa dominated the formation of DCAcAm and TCAcAm. However, particle-associated DCAN precursors were detected in addition to potent DCAN precursors in the DOM fractions. Among the XAD fractions of DOM, the hydrophilic neutral fraction prevailed in the secondary effluent and produced the most DCAN, DCAcAm and TCAcAm per volume, and the hydrophilic basic fraction with a low organic content had the highest yields of DCAN, DCAcAm and TCAcAm on a DOC basis, so their dominant precursors were associated with hydrophilic matter.

Peptide bonds affect the formation of haloacetamides, an emerging class of N-DBPs in drinking water: free amino acids versus oligopeptides.

Haloacetamides (HAcAms), an emerging class of nitrogenous disinfection by-products (N-DBPs) of health concern, have been frequently identified in drinking waters. It has long been appreciated that free amino acids (AAs), accounting for a small fraction of the dissolved organic nitrogen (DON) pool, can form dichloroacetamide (DCAcAm) during chlorination. However, the information regarding the impacts of combined AAs, which contribute to the greatest identifiable DON portion in natural waters, is limited. In this study, we compared the formation of HAcAms from free AAs (tyrosine [Tyr] and alanine [Ala]) and combined AAs (Tyr-Ala, Ala-Tyr, Tyr-Tyr-Tyr, Ala-Ala-Ala), and found that HAcAm formation from the chlorination of AAs in combined forms (oligopeptides) significantly exhibited a different pattern with HAcAm formation from free AAs. Due to the presence of peptide bonds in tripeptides, Tyr-Tyr-Tyr and Ala-Ala-Ala produced trichloroacetamide (TCAcAm) in which free AAs was unable to form TCAcAm during chlorination. Moreover, peptide bond in tripeptides formed more tri-HAcAms than di-HAcAms in the presence of bromide. Therefore, the peptide bond may be an important indicator to predict the formation of specific N-DBPs in chlorination. The increased use of algal- and wastewater-impacted water as drinking water sources will increase health concerns over exposure to HAcAms in drinking water.

Simultaneous determination of three chloroacetic acids, three herbicides, and 12 anions in water by ion chromatography.

An ion chromatography method was developed for the simultaneous detection of three soluble herbicides (glyphosate, bentazone and picloram), three chlorine disinfection byproducts (monochloroacetic acid, dichloroacetic acid and trichloroacetic acid) and 12 anions in water (Cl(-), Br(-), SO4(2-), CO3(2-), ClO3(-), ClO4(-), BrO3(-), PO4(3-), NO2(-), NO3(-), CH3COO(-) and COO(-)). High linearity (r(2) > 0.996) was observed for all target analytes for each respective concentration range. The limit of detection and limit of quantitation were between 0.21-0.85 and 0.06-25.46 µg/L, respectively. However, the interference effect of Cl(-), NO3(-) , SO4 (2-) and CO3(2-) on some target analytes must be considered during the analysis. Sample pre-treatment by a hydrogen column (H-column) required to reduce the negative effect of CO3(2-). Additionally, sample pre-treatment by a sliver-hydrogen column (Ag-H-column) is required when Cl(-) > 100 mg/L and SO4(2-) < 50 mg/L, and pre-treatment by both a barium column (Ba-column) and an H-column is required when Cl(-) > 100 mg/L and SO4(2-) > 50 mg/L. When Cl(-) > 100 mg/L, SO4(2-) > 50 mg/L and CO3(2-) > 20 mg/L, the sample pre-treatment by either an Ag-H-Ba-column or an Ag-H-column and Ba-column is required to minimize interference.

Simultaneous quantification of trihalomethanes and haloacetic acids in cheese by on-line static headspace gas chromatography-mass spectrometry.

Trihalomethanes (THMs) and haloacetic acids (HAAs) are the two most prevalent classes of disinfection by-products (DBPs) that are present in treated water. Four THMs and six HAAs are regulated by several countries in drinking waters but no regulation for these DBPs has been established in foods. THMs are volatile species that can easily be determined by static headspace (SHS)-GC-MS, but HAAs require a derivatisation step to make them suitable for GC due to their polar and hydrophilic nature. This paper describes the first analytical method that performs the simultaneous determination of 10 THMs and 13 HAAs (chlorinated, brominated and iodinated) in cheeses by SHS in one unique GC-MS run. Parameters controlling leaching, centrifugation, derivatisation and volatilisation were optimised taking into account the high volatility of THMs and the thermal instability of HAAs. To increase sensitivity, 3g of cheese was extracted with 10mL of water at pH 4.5-7.7, and after centrifugation the supernatant (∼8mL) was introduced into an HS vial for the derivatisation (HAAs) and volatilisation (HAA esters and THMs) of the species in an automatic SHS unit coupled to GC-MS. Detection limits within the range of 0.05-0.50 and 0.15-0.85µg/kg for THMs and HAAs, respectively, were obtained, and the relative standard deviation was lower than 10% for all the target analytes. Recoveries throughout the whole method were between 85-90% and 92-97% for THMs and HAAs, respectively. The SHS-GC-MS method was applied for the determination of THMs and HAAs in 3 groups of Spanish cheeses, which can be contaminated through contact with treated water during the manufacturing steps. Up to 2 THMs and 4 HAAs were found at µg/kg levels in the samples analysed.

Predicting human exposure and risk from chlorinated indoor swimming pool: a case study.

This study predicted human exposure to disinfection by-products (DBPs) in a chlorinated indoor swimming pool. Human exposure was predicted through ingestion, inhalation, and dermal routes while ingestion exposure was accidental with water intake of 18-34 mL/h. The number of pool attendants and duration and frequency of swimming were in the ranges of 14-62 persons/day, 40-85 min/event, and 26-48 times/year, respectively. Trihalomethanes (THMs) in pool water and air were 28.7-95.5 µg/L and 44.1-133.6 µg/m(3), respectively, while haloacetic acids (HAAs) in pool water were 68.9-158.9 µg/L. The brominated THMs in water and air were 95.4 and 94.3% of total THMs, respectively, while brominated HAAs were 94.4 % of total HAAs. Chronic daily intakes of THMs and HAAs were 2.16 × 10(-5)-3.14 × 10(-3) and 8.4 × 10(-8)-4.6 × 10(-6) mg/kg-day, respectively. The cancer risk from three THMs and two HAAs was 2.46 × 10(-5) with a range of 8.1 × 10(-6)-5.7 × 10(-5), in which THMs contributed 99.6% of total risks. Approximately 99.3% of risks were through inhalation and dermal routes, indicating that the ingestion route may be insignificant. The cancer risks from THMs in swimming pool were 4.06-6.64 times to the cancer risks from THMs in drinking water.

Pentafluorobenzyl esterification of haloacetic acids in tap water for simple and sensitive analysis by gas chromatography/mass spectrometry with negative chemical ionization.

Chlorine is the most widely used disinfectant for control of waterborne diseases in drinking water treatment. It can react with natural organic matter in water and form haloacetic acids (HAAs). For analysis of HAA levels, derivatization with diazomethane is commonly recommended as the standard methodology in Japan. However, diazomethane is a carcinogenic alkylating agent. Therefore, in this study, a safe, simple, and sensitive quantification method was developed to monitor HAAs in drinking water. Pentafluorobenzyl esterification was used for pretreatment. The pentafluorobenzyl-ester derivative was detected by gas chromatography-negative ion chemical ionization-mass spectrometry analysis with very high sensitivity for HAAs analysis. The method has low detection limits (8-94 ng L(-1)) and good recovery rates (89-99%) for HAAs. The method was applied to 30 tap water samples from 15 cities in the Kansai region of Japan. The levels of HAAs detected were in the range 0.54-7.83 µg L(-1). Dichloroacetic acid, trichloroacetic acid, and bromochloroacetic acid were the major HAAs detected in most of the tap water, and accounted for 29%, 20% and 19% of the total HAAs, respectively. This method could be used for routine monitoring of HAAs in drinking water without exposure of workers to occupational hazards.

Determination of haloacetic acids in swimming pool waters by membrane-protected micro-solid phase extraction.

In this study, a simple and efficient extraction method for determining haloacetic acids (HAAs) in swimming pool waters has been developed. HAAs are toxic organic pollutants of disinfection origin most commonly detected in swimming pool and drinking waters at trace level concentrations. For the first time, a highly efficient sorbent was developed using rice husk and used for micro-solid phase extraction (µ-SPE) technique. To increase the extraction capability of rice husk silica, iron oxide was incorporated via sol-gel process. In µ-SPE device, the novel sorbent was packed and used for extraction of HAAs prior to analysis using ultra performance liquid chromatography-ultraviolet detection (UPLC-UV). Various extraction parameters were optimized to improve the extraction efficiency of µ-SPE. Under optimum conditions, linearity (coefficient of determination, r(2)≥0.991 over the concentration range of 1-150 µg/L), detection limits in the range of 0.001-0.092 µg/L, mean recoveries up to 110% with corresponding relative standard deviations of 2-7% (n=3) had been obtained. Finally, the method was applied to swimming pool water to evaluate its feasibility. The mean concentrations for HAAs from the pool waters were in the range of 6.8 and 48.6 µg/L which are far below the standard values set by United States Environmental Protection Agency.

Haloacetic acid removal by sequential zero-valent iron reduction and biologically active carbon degradation.

An innovative haloacetic acid (HAA) removal process was developed. The process consisted of a zero-valent iron (Fe(0)) column followed by a biologically active carbon (BAC) column that were efficient in degrading tri- and di-HAAs, and mono- and di-HAAs, respectively. The merit of the process was demonstrated by its performance in removing trichloroacetic acid (TCAA). An empty bed contact time of 10 min achieved nearly complete removal of 1.2 µM TCAA and its subsequent products, dichloroacetic acid (DCAA) and monochloroacetic acid (MCAA). HAA removal was a result of chemical dehalogenation and biodegradation rather than physical adsorption. Preliminary kinetic analyses were conducted and the pseudo-first-order rate constants were estimated at ambient conditions for Fe(0) reduction of TCAA and biodegradation of DCAA and MCAA by BAC. This innovative process is highly promising in removing HAAs from drinking water, swimming pool water, and domestic or industrial wastewater.

Assessing the role of trichloroacetyl-containing compounds in the natural formation of chloroform using stable carbon isotopes analysis.

Chloroform (CHCl(3)) is an environmental contaminant widely distributed around world, as well as a natural compound formed in various aquatic and terrestrial environments. However, the chemical mechanisms leading to the natural formation of chloroform in soils are not completely understood. To assess the role of trichloroacetyl-containing compound (TCAc) in the natural formation of chloroform in forest soils, carbon stable isotope analyses of chloroform and TCAc in field samples and chlorination experiments were carried out. The isotope analysis of field samples have revealed that the δ(13)C value of natural chloroform (δ(13)C(mean)=-25.8‰) is in the same range as the natural organic matter (δ(13)C(mean)=-27.7‰), whereas trichloromethyl groups of TCAc are much more enriched in (13)C (δ(13)C(mean)=-9.8‰). A similar relationship was also observed for TCAc and chloroform produced by chlorination of natural organic matter with NaOCl. The strong depletion of (13)C in chloroform relative to TCAc can be explained by carbon isotope fractionation during TCAc hydrolysis. As shown using a mathematical model, when steady state between formation of TCAc and hydrolysis is reached, the isotope ratio of chloroform is expected to correspond to isotope composition of NOM while TCAc should be enriched in (13)C by about 18.3‰, which is in good agreement with field observations. Hence this study suggests that TCAc are likely precursors of chloroform and at the same time explains why natural chloroform has a similar isotope composition as NOM despite large carbon isotope fractionation during its release.