Marine fungi Aspergillus sydowii and Trichoderma sp. catalyze the hydrolysis of benzyl glycidyl ether

Whole cells of the marine fungi Aspergillus sydowii Gc12, Penicillium raistrickii Ce16, P. miczynskii Gc5, and Trichoderma sp. Gc1, isolated from marine sponges of the South Atlantic Ocean (Brazil), have been screened for the enzymatic resolution of (±)-2-(benzyloxymethyl)oxirane (benzyl glycidyl ether; 1). Whole cells of A. sydowii Gc12 catalyzed the enzymatic hydrolysis of (R,S)-1 to yield (R)-1 with an enantiomeric excess (ee) of 24-46% and 3-(benzyloxy)propane-1,2-diol (2) with ee values <10%. In contrast, whole cells of Trichoderma sp. Gc1 afforded (S)-1 with ee values up to 60% and yields up to 39%, together with (R)-2 in 25% yield and an ee of 32%. This is the first published example of the hydrolysis of 1 by whole cells of marine fungi isolated from the South Atlantic Ocean. The hydrolases from the two studied fungi exhibited complementary regioselectivity in opening the epoxide ring of racemic 1, with those of A. sydowii Gc12 showing an (S) preference and those of Trichoderma sp. Gc1 presenting an (R) preference for the substrate.

Comparison of inclined plate sedimentation and dissolved air flotation for the minimisation of subsequent nitrogenous disinfection by-product formation

The formation of disinfection by-products (DBPs), including both nitrogenous disinfection by-products (N-DBPs) and carbonaceous disinfection by-products (C-DBPs), was investigated upon chlorination of water samples following two treatment processes: (i) coagulation-inclined plate sedimentation (IPS)-filtration and (ii) coagulation-dissolved air flotation (DAF)-filtration. The removal of algae, dissolved organic nitrogen (DON), dissolved organic carbon (DOC) and UV(254) by coagulation-DAF-filtration was superior to coagulation-IPS-filtration. On average, 53%, 53% and 31% of DOC, DON and UV(254) were removed by coagulation-DAF-filtration process, which were higher than 47%, 31% and 27% of that by coagulation-IPS-filtration process. Additionally, coagulation-IPS-filtration performed less well at removing the low molecular weight organics than coagulation-DAF-filtration process. The concentrations of chloroform, dichloroacetamide (DCAcAm) and dichloroacetonitrile (DCAN) formed during chlorination after coagulation-DAF-filtration reached their maximum values of 13, 1.5 and 4.7μgL(-1), respectively, and were lower than those after coagulation-IPS-filtration with the maximum detected levels of 17, 2.9 and 6.3μgL(-1). However, the trichloronitromethane (TCNM) concentration after the two processes was similar, suggesting that DON may have less of a contribution to TCNM formation than DCAcAm and DCAN.

Formation and decomposition of new and unknown polar brominated disinfection byproducts during chlorination

Brominated disinfection byproducts (Br-DBPs) are generally more cytotoxic and genotoxic than their chlorinated analogues. A great portion of total organic bromine in chlorinated drinking water is still unknown and may be ascribed to polar Br-DBPs. In this work, a novel approach, precursor ion scan using ultra-performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry, was adopted and further developed for selective detection and identification of polar Br-DBPs, which made it possible to reveal the whole picture of the formation and decomposition of polar Br-DBPs during chlorination. Simulated drinking water samples with chlorine contact times from 1 min to 7 d were analyzed. Many new polar aromatic and unsaturated aliphatic Br-DBPs were detected and tentatively proposed with chemical structures, of which 2,4,6-tribromophenol, 3,5-dibromo-4-hydroxybenzoic acid, 2,6-dibromo-1,4-hydroquinone, and 3,3-dibromopropenoic acid were confirmed or identified with authentic standards. It was found that various polar Br-DBPs formed and reached the maximum levels at different chlorine contact times; high molecular weight Br-DBPs might undergo decomposition to relatively low molecular weight Br-DBPs or even finally to haloacetic acids and trihalomethanes. The decomposition of newly detected intermediate Br-DBPs (including molecular ion cluster m/z 345/347/349/351, 2,4,6-tribromophenol, and 3,5-dibromo-4-hydroxybenzoic acid) during chlorination was investigated in detail. The "black box" from the input of "humic substances + bromide + chlorine" through the output of "haloacetic acids + trihalomethanes" was opened to a significant extent.

Free chlorine and monochloramine application to nitrifying biofilm: comparison of biofilm penetration, activity, and viability

Biofilm in drinking water systems is undesirable. Free chlorine and monochloramine are commonly used as secondary drinking water disinfectants, but monochloramine is perceived to penetrate biofilm better than free chlorine. However, this hypothesis remains unconfirmed by direct biofilm monochloramine measurement. This study compared free chlorine and monochloramine biofilm penetration into an undefined mixed-culture nitrifying biofilm by use of microelectrodes and assessed the subsequent effect on biofilm activity and viability by use of dissolved oxygen (DO) microelectrodes and confocal laser scanning microscopy (CLSM) with LIVE/DEAD BacLight. For equivalent chlorine concentrations, monochloramine initially penetrated biofilm 170 times faster than free chlorine, and even after subsequent application to a monochloramine penetrated biofilm, free chlorine penetration was limited. DO profiles paralleled monochloramine profiles, providing evidence that either the biofilm was inactivated with monochloramine's penetration or its persistence reduced available substrate (free ammonia). While this research clearly demonstrated monochloramine's greater penetration, this penetration did not necessarily translate to immediate viability loss. Even though free chlorine's penetration was limited compared to that of monochloramine, it more effectively (on a cell membrane integrity basis) inactivated microorganisms near the biofilm surface. Limited free chlorine penetration has implications when converting to free chlorine in full-scale chloraminated systems in response to nitrification episodes.

Hypochlorous and peracetic acid induced oxidation of dairy proteins

Hypochlorous and peracetic acids, both known disinfectants in the food industry, were compared for their oxidative capacity toward dairy proteins. Whey proteins and caseins were oxidized under well controlled conditions at pH 8 as a function of the sanitizing concentration. Different markers for protein oxidation were monitored. The results established that the protein carbonyl content was a rather unspecific marker for protein oxidation, which did not allow one to differentiate the oxidant used especially at the lower concentrations. Cysteine, tryptophan, and methionine were proven to be the most vulnerable amino acids for degradation upon hypochlorous and peracetic acid treatment, while tyrosine was only prone to degradation in the presence of hypochlorous acid. Hypochlorous acid induced oxidation gave rise to protein aggregation, while during peracetic acid induced oxidation, no high molecular weight aggregates were observed. Protein aggregation upon hypochlorous acid oxidation could primarily be linked to tryptophan and tyrosine degradation.

Removal of estrogens through water disinfection processes and formation of by-products

Estrogens constitute a recognized group of environmental emerging contaminants which have been proven to induce estrogenic effects in aquatic organisms exposed to them. Low removal efficiency in wastewater treatment plants results in the presence of this type of contaminants in surface waters and also even in finished drinking water. This manuscript reviews the environmental occurrence of natural (estrone, estradiol and estriol) and synthetic (ethynyl estradiol) estrogens in different water matrices (waste, surface, ground and drinking water), and their removal mainly via chemical oxidative processes. Oxidative treatments have been observed to be very efficient in eliminating estrogens present in water; however, disinfection by-products (DBPs) are generated during the process. Characterization of these DBPs is essential to assess the risk that drinking water may potentially pose to human health since these DBPs may also have endocrine disrupting properties. This manuscript reviews the DBPs generated during oxidative processes identified so far in the literature and the estrogenicity generated by the characterized DBPs and/or by the applied disinfection technology.

Loss rates of urban biocides can exceed those of agricultural pesticides

Biocides and pesticides are used to control unwanted organisms in urban and agricultural areas. After application, they can be lost to surface waters and impair water quality. Several national consumption studies have shown that urban and agricultural use may be in the same range. It is difficult to judge whether this results in similar loadings of surface waters because there is a lack of sound, comparative studies addressing urban and agricultural losses simultaneously. The aim of this study is thus to relate the biocide and pesticide loads found in surface waters to their respective urban and agricultural usage (loss rates). To simultaneously assess the loss rates, we conducted a comprehensive field study in a catchment of mixed land use on the Swiss Plateau. The study area was divided into four sub-catchments with different degrees of urban and agricultural land use. In addition, we studied the only wastewater treatment plant, a combined sewer overflow and a storm sewer within the area. Rain events were sampled at high temporal resolution from March to November, 2007. Information on agricultural applications was gained from local farmers. For urban uses, consumption estimations were conducted based on statistical and product information. Despite substantially lower amounts used, the measured loads of urban biocides were in the same range as the most widely-used agricultural pesticides. The lower usage was compensated by urban loss rates that were up to ten times higher than agricultural ones (0.6 to 15% for urban, 0.4 to 0.9% for agricultural compounds). For most biocides and pesticides, the loads were controlled by rain events. Besides the rain-controlled losses, some urban-used biocides (e.g. diazinon) showed a continuous load independent of rain events and season. This study demonstrates that in catchments with mixed land use, mitigation strategies have to pay sufficient attention to the urban sources.

Understanding the operational parameters affecting NDMA formation at Advanced Water Treatment Plants

N-nitrosodimethylamine (NDMA) can be formed when secondary effluents are disinfected by chloramines. By means of bench scale experiments this paper investigates operational parameters than can help Advanced Water Treatment Plants (AWTPs) to reduce the formation of NDMA during the production of high quality recycled water. The formation of NDMA was monitored during a contact time of 24h using dimethylamine as NDMA model precursor and secondary effluent from wastewater treatment plants. The three chloramine disinfection strategies tested were pre-formed and in-line formed monochloramine, and pre-formed dichloramine. Although the latter is not employed on purpose in full-scale applications, it has been suggested as the main contributing chemical generating NDMA during chloramination. After 24h, the NDMA formation decreased in both matrices tested in the order: pre-formed dichloramine>in-line formed monochloramine≫pre-formed monochloramine. The most important parameter to consider for the inhibition of NDMA formation was the length of contact time between disinfectant and wastewater. Formation of NDMA was initially inhibited for up to 6h with concentrations consistently <10 ng/L during these early stages of disinfection, regardless of the disinfection strategy. The reduction of the contact time was implemented in Bundamba AWTP (Queensland, Australia), where NDMA concentrations were reduced by a factor of 20 by optimizing the disinfection strategy.

Modeling DBPs formation in drinking water in residential plumbing pipes and hot water tanks

Disinfection byproducts (DBPs) in municipal supply water are a concern because of their possible risks to human health. Risk assessment studies often use DBP data in water distribution systems (WDS). However, DBPs in tap water may be different because of stagnation of the water in plumbing pipes (PP) and heating in hot water tanks (HWT). This study investigated occurrences and developed predictive models for DBPs in the PP and the HWT of six houses from three municipal water systems in Quebec (Canada) in a year-round study. Trihalomethanes (THMs) in PP and HWT were observed to be 1.4-1.8 and 1.9-2.7 times the THMs in the WDS, respectively. Haloacetic acid (HAAs) in PP and HWT were observed to be variable (PP/WDS = 0.23-2.24; HWT/WDS = 0.53-2.61). Using DBPs occurrence data from these systems, three types of linear models (main factors; main factors, interactions and higher orders; logarithmic) and two types of nonlinear models (three parameters Logistic and four parameters Weibull) were investigated to predict DBPs in the PP and HWT. Significant factors affecting DBPs formation in the PP and HWT were identified through numerical and graphical techniques. The R(2) values of the models varied between 0.77 and 0.96, indicating excellent predictive ability for THMs and HAAs in the PP and the HWT. The models were found to be statistically significant. The models were validated using additional data. These models can be used to predict DBPs increase from WDS (water entry point of house) to the PP and HWT, and could thereby help gain a better understanding of human exposure to DBPs and their associated risks.

Characterization of disinfection byproduct formation potential in 13 source waters in China

The formation potential of four trihalomethanes (THMFP) and seven haloacetic acids (HAA7FP) in 13 source waters taken from four major water basin areas in China was evaluated using the simulated distribution system (SDS) chlorination method. The specific ultraviolet absorbance (SUVA254: the ratio of UV254 to dissolved organic carbon (DOC)), which ranged between 0.9 and 5.0 L/(mg x m), showed that the organic compounds in different source waters exhibited different reactivities with chlorine. The HAA7FP of source waters ranged from 20 to 448 microg/L and the THMFP ranged from 29 to 259 microg/L. The HAA7FP concentrations were higher than the THMFP concentrations in all but one of the samples. Therefore, the risks of haloacetic acids (HAAs) should be of concern in some source waters. TCM (chloroform) and BDCM (bromodichloromethane) were the major THM constituents, while TCAA (trichloroacetic acid) and DCAA (dichloroacetic acid) were the major HAA species. Br-THM (brominated THM species) were much higher than Br-HAA (brominated HAA species), and the formation of Br-DBP (Br-THM and Br-HAA) should be of concern when the bromide concentration is over 100 microg/L.

Nanofiltration for enhanced removal of disinfection by-product (DBP) precursors in swimming pool water-retention and water quality estimation

Three nanofiltration (NF) membranes with a chlorine tolerance > or = 1 mg L-1 were applied to reduce DBPs and their precursors in swimming pool water. A lab scale plant with crossflow modules was installed in by-pass at the sand filter outlet of a swimming pool for a period of several weeks. The chlorine tolerances of the membranes SB90 and NP030 were found to be adequate for filtration under swimming pool water conditions over the given experimental period. Retention of dissolved organic carbon (DOC) and adsorbable organic halogens (AOX) were about 70% and 80% for SB90 and 50% and 40% for NP030, respectively. DOC accumulation in the pool and the expected fresh water consumption for a treatment system consisting of ultrafiltration (UF) and NF with backwash water treatment were estimated by mass balances based on the results. Mass balances were calculated also for a German public swimming pool with a conventional water treatment system (flocculation-sand filtration-chlorination) and were compared to DOC on-line measurements. Calculation of DOC mass balances for different UF-NF treatment scenarios showed that pool water quality could be improved significantly compared to the conventional treatment system.

Chlorine disinfection of Pseudomonas aeruginosa, total coliforms, Escherichia coli and Enterococcus faecalis: revisiting reclaimed water regulations

Pathogenic organisms can be transmitted orally through drinking water or through skin and mucosae by both direct and indirect contact, and their presence in water thus has a negative impact on public health. In wastewater treatment plants (WWTP), water is disinfected to inactivate pathogens. The quantification of several microbial indicators in aquatic systems is required to estimate the biological quality of such systems. So far, coliform bacteria have been used as traditional indicators world-wide. This study has assessed the resistance of total coliforms, Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis to three dosages of sodium hypochlorite (NaClO) at two exposure times. The bacteria were isolated from secondary effluents of a WWTP located in Hidalgo, Mexico. The results show that the number of colony-forming units of all studied bacterial types decreased when both the NaClO concentration and exposure times increased. However, they were not eliminated. The inclusion of the species Pseudomonas aeruginosa in regulations for treated wastewater quality as a new indicator is highly recommended due to its importance as an opportunistic pathogen. The detection of this species along with the traditional organisms could be particulary significant for reclaimed water to be used with direct human contact.

Synthesis and structure-activity study of quaternary ammonium functionalized beta-cyclodextrin-carboxymethylcellulose polymers

Carboxymethylcellulose (CMC) and beta-cyclodextrin (beta-CD)-based polymers functionalized with two types of quaternary ammonium compounds (QACs), the alkaquat DMB-451 (N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride) (DMD-451) named polymer DMB-451, and FMB 1210-8 (a blend of 32 w% N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride and 48 w% of didecyldimethylammonium chloride) named polymer FMB 1210-8, were synthethized and characterized by Fourier transform infrared spectroscopy. The antimicrobial activities of these polymers against Eschericia coli were also evaluated at 25 degrees C in wastewater. The results have indicated that the polymer FMB 1210-8 possesses a high-affinity binding with bacterial cells that induces a rapid disinfection process. Moreover, in the same experimental conditions of disinfection (mixture of 1.0 g of polymer and 100 mL of wastewater), the polymer FMB 1210-8 has a higher antimicrobial efficiency (99.90%) than polymer DMB-451 (92.8%). This phenomenon might be associated to a stronger interaction with bacterial cells due to stronger binding affinity for E. coli cells and greater killing efficiency of the C10 alkyl chains QAC of polymer FMB 1210-8 to disrupt the bacterial cell membrane as compared to N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride. Together, these results suggest that the polymer FMB 1210-8 could constitute a good disinfectant against Escherichia coli, which could be advantageously used in wastewater treatments due to the low toxicity of beta-CD and CMC, and moderated toxicity of FMB 1210-8 to human and environment.

Leaching of additives from construction materials to urban storm water runoff

Urban water management requires further clarification about pollutants in storm water. Little is known about the release of organic additives used in construction materials and the impact of these compounds to storm water runoff. We investigated sources and pathways of additives used in construction materials, i.e., biocides in facades' render as well as root protection products in bitumen membranes for rooftops. Under wet-weather conditions, the concentrations of diuron, terbutryn, carbendazim, irgarol 1051 (all from facades) and mecoprop in storm water and receiving water exceeded the predicted no-effect concentrations values and the Swiss water quality standard of 0.1 microg/L. Under laboratory conditions maximum concentrations of additives were in the range of a few milligrams and a few hundred micrograms per litre in runoff of facades and bitumen membranes. Runoff from aged materials shows approximately one to two orders of magnitude lower concentrations. Concentrations decreased also during individual runoff events. In storm water and receiving water the occurrence of additives did not follow the typical first flush model. This can be explained by the release lasting over the time of rainfall and the complexity of the drainage network. Beside the amounts used, the impact of construction materials containing hazardous additives on water quality is related clearly to the age of the buildings and the separated sewer network. The development of improved products regarding release of hazardous additives is the most efficient way of reducing the pollutant load from construction materials in storm water runoff.

Treatment of disinfection by-product precursors

Formation of harmful disinfection by-products (DBPs), of which trihalomethanes (THMs) and haloacetic acids (HAAs) are the major groups, can be controlled by removal of natural organic matter (NOM) before disinfection. In the literature, removal of precursors is variable, even with the same treatment. The treatment of DBP precursors and NOM was examined with the intention of outlining precursor removal strategies for various water types. Freundlich adsorption parameters and hydroxyl rate constants were collated from the literature to link treatability by activated carbon and advanced oxidation processes (AOPs), respectively, to physico-chemical properties. Whereas hydroxyl rate constants did not correlate meaningfully with any property, a moderate correlation was found between Freundlich parameters and log K(ow), indicating activated carbon will preferentially adsorb hydrophobic NOM. Humic components of NOM are effectively removed by coagulation, and, where they are the principal precursor source, coagulation may be sufficient to control DBPs. Where humic species remaining post-coagulation retain significant DBP formation potential (DBPFP), activated carbon is deemed a suitable process selection. Anion exchange is an effective treatment for transphilic species, known for high carboxylic acid functionality, and consequently is recommended for carboxylic acid precursors. Amino acids have been linked to HAA formation and are important constituents of algal organic matter. Amino acids are predicted to be effectively removed by biotreatment and nanofiltration. Carbohydrates have been found to reach 50% of NOM in river waters. If the carbohydrates were to pose a barrier to successful DBP control, additional treatment stages such as nanofiltration are likely to be required to reduce their occurrence.

Applicability of microwave-assisted extraction combined with LC-MS/MS in the evaluation of booster biocide levels in harbour sediments

A new sample treatment method for the determination of four common booster biocides (Diuron, TCMTB, Irgarol 1051 and Dichlofluanid) in harbour sediment samples has been developed that uses liquid chromatography-tandem mass spectrometry (LC-MS/MS) after microwave-assisted extraction, followed by clean-up and a solid phase extraction preconcentration step (MAE-SPE). The effects of different variables on MAE-SPE were studied. The recoveries obtained were greater than 75%, and the relative standard deviation was less than 7%. The detection limits ranged between 0.1 and 0.3 ng g⁻¹. The developed methodology was successfully applied to the evaluation of the presence of booster biocides in sediment samples from different harbours and marinas of Gran Canaria Island (Canary Islands, Spain).

Analysis of trihalomethanes in water and air from indoor swimming pools using HS-SPME/GC/ECD

Headspace solid phase microextraction (HS-SPME) with further quantification by gas chromatography and electron capture detector (GC/ECD) was used to analyze trihalomethanes (THMs) in water and air from indoor swimming pools (ISPs). High correlation coefficients were obtained for the calibration lines in water with detection limits of 0.2 μg/L for trichloromethane (TCM) and bromodichloromethane (BDCM), 0.1 μg/L for dibromochloromethane (DBCM) and 0.5 μg/L for tribromomethane (TBM). Coefficients of variation values were 5-10% for repeatability and 15-25% for reproducibility. In air analysis, high correlation coefficients were also obtained for the calibration lines with detection limits of 2.5 μg/m(3) for TCM and BDCM and 1.25 μg/m(3) for DBCM and TBM. Repeatability and reproducibility coefficients of variation were the same as in water analysis. Analytical results from a survey in four Portuguese ISPs showed that the mean concentration of total trihalomethanes (TTHMs) in water ranged from 22±2 to 577±58 μg/L. In the lack of European specific regulation for THMs in water from ISPs and taking into consideration that ingestion is a form of exposure, TTHMs' values were compared with European drinking water maximum contamination level (100 μg/L, Directive 98/83/CE). From the reported TTHMs mean concentration values in ISPs' water, 40% exceeded that value. TTHMs values determined in the air (T = 30°C) ranged from 98±10 to 1225±123 μg/m(3) and from 51±5 μg/m(3)to 519±52 μg/m(3)at 5 and 150 cm above the water surface, respectively. As expected, swimmers are more exposed to high concentrations of THMs than lifeguards. As there is no European specific regulation for THMs in ISPs' air, the highest TCM values were compared with maximum values reported in the literature for ISPs (1630 μg/m(3)) and with the inhalation exposure limit (10,000 μg/m(3)) established for TCM by European occupational legislation (Directive 2000/39/CE).

Formation of disinfection byproducts in typical Chinese drinking water

Eight typical drinking water supplies in China were selected in this study. Both source and tap water were used to investigate the occurrence of chlorinated disinfection byproducts (DBPs), and seasonal variation in the concentrations of trihalomethanes (THMs) of seven water sources was compared. The results showed that the pollution level for source water in China, as shown by DBP formation potential, was low. The most encountered DBPs were chloroform, dichloroacetic acid, trichloroacetic acid, and chlorodibromoacetic acid. The concentration of every THMs and haloacetic acid (HAA) compound was under the limit of standards for drinking water quality. The highest total THMs concentrations were detected in spring.

Evaluation and improvement of total organic bromine analysis with respect to reductive property of activated carbon

A collective parameter and a toxicity indicator for all the halogenated organic disinfection byproducts in a water sample is total organic halogen (TOX), which can be differentiated as total organic chlorine (TOCl), total organic bromine (TOBr) and total organic iodine. The TOX method involves concentration of organic halogens from water by adsorption onto activated carbon (AC). A previous study showed that a portion of TOCl can be reduced to chloride during the adsorption procedure, which can be minimized by ozonation of the AC. In this study, a portion of TOBr was sometimes found to be reduced by AC to bromide, and the reduction was generally less than that of corresponding TOCl. The results suggested that around 10% of brominated Suwannee River fulvic acid was reduced to bromide. However, some brominated amino compounds (especially glycylglycine, phenylalanine, and cytosine) were found to be more reactive with the AC. For the iodinated compounds studied, the reduction to iodide was not significant. The method for the TOBr measurement was improved by using ozonated AC when reduction occurred on the original AC. The improved method was also evaluated on treated wastewater and swimming pool water samples.

Electrospray ionization mass spectrometry characterization of interactions of newly identified water disinfection byproducts halobenzoquinones with oligodeoxynucleotides

Four halobenzoquinones, 2,6-dibromo-1,4-benzoquinone, 2,6-dichloro-1,4-benzoquinone, 2,6-dichloro-3-methyl-1,4-benzoquinone, and 2,3,6-trichloro-1,4-benzoquinone, were recently identified as drinking water disinfection byproducts. Understanding their interactions with biomolecules could provide useful insights into their potential toxic effects. We report here electrospray ionization mass spectrometry characterization of the interactions between these new halobenzoquinone disinfection byproducts and oligodeoxynucleotides. The study demonstrates that 2,6-dibromo-1,4-benzoquinone exhibits much stronger binding to single- and double-stranded oligodeoxynucleotides than chlorobenzoquinones. The binding affinity of 2,6-dibromo-1,4-benzoquinone to oligodeoxynucleotides is similar to that of ethidium bromide, a well-known intercalator and carcinogen. Tandem mass spectrometry characterization confirms the formation of 1:1 and 2:1 complexes of 2,6-dibromo-1,4-benzoquinone binding to oligodeoxynucleotides. Collision-induced dissociation analysis of these adducts demonstrates neutral loss and charge separation, suggesting that 2,6-dibromo-1,4-benzoquinone binds to oligodeoxynucleotides through partial intercalation and H-bonding modes. The three chlorobezoquinones also form 1:1 adducts with the oligodeoxynucleotides, but their binding to the oligodeoxynucleotides was much weaker compared to that of 2,6-dibromo-1,4-benzoquinone. The relative binding affinity of the studied disinfection byproducts to oligodeoxynucleotides is in the order of 2,6-dibromo-1,4-benzoquinone≫2,6-dichloro-1,4-benzoquinone > 2,6-dichloro-3-methyl-1,4-benzoquinone ∼ 2,3,6-trichloro-1,4-benzoquinone, indicating potential structural effects on the interactions of halobenzoquinones with oligodeoxynucleotides.

Effects of Ca2+ and Mg2+ on defluoridation in the electrocoagulation process

Because aqueous ions can influence the defluoridation of the electrocoagulation (EC) process, the effects of Ca(2+) and Mg(2+) were investigated. The behaviors and mechanisms of EC defluoridation in Ca(2+)-containing systems were different from those in Mg(2+)-containing systems. An increase in Ca(2+) concentration improved the defluoridation efficiency (ε(F)), but it could not change the optimal molar ratio of OH(-) and F(-) to Al(3+) (r(OH+F)). The highest ε(F) can usually be obtained at r(OH+F) = 3 for defluoridation. Only a small portion of Ca(2+) entered into the flocs, and Ca(2+) could not influence the mechanism of EC defluoridation. For the Mg(2+)-containing system, the optimal r(OH+F) increased with increasing Mg(2+) concentration. The optimal r(OH+F) was maintained at 3 after the Mg(2+) concentration was corrected using the obtained correction coefficient of 0.3435. About 50% to 70% of the total Mg(2+) entered into the flocs. From the XRD analysis, it was found that some Mg-Al-F layered double hydroxides (LDHs) were formed by Mg(2+), F(-), and Al(3+) during electrolysis. It is proposed for the first time that the formation of Mg-Al-F LDH is one of the mechanisms for EC defluoridation in systems containing both F(-) and Mg(2+).

Depleting methyl bromide residues in soil by reaction with bases

Despite generally being considered the most effective soil fumigant, methyl bromide (MeBr) use is being phased out because its emissions from soil can lead to stratospheric ozone depletion. However, a large amount is still currently used due to Critical Use Exemptions. As strategies for reducing the postfumigation emissions of MeBr from soil, Ca(OH)(2), K(2)CO(3), and NH(3) were assessed as means of promoting MeBr degradation. Ammonia aqueous solution (NH(4)OH) was the most effective, because MeBr can be degraded by both hydrolysis and ammonolysis. At 20 °C, the half-lives (t(1/2)) of MeBr were 18.0, 2.5, and 1.3 h in 0.1, 1.0, and 2.0 M NH(4)OH, respectively. In 1.0 M NH(4)OH, increasing the solution temperature to 40 °C reduced the half-life of MeBr to 0.23 h. Ammonia amendment to moist soil also promoted MeBr transformation, and the MeBr degradation rate increased with increasing soil temperature. NH(4)OH (30%, 16 M) very effectively reacted with MeBr that was contained under plastic film. Under Hytibar (a virtually impermeable film, VIF), over 99.5% of the MeBr could be destroyed by 30% NH(4)OH in 8 h at 20 °C. On the basis of these results, good management practices (i.e., VIF plus NH(4)OH) could be developed for continued use of MeBr as a soil fumigant under Critical Use Exemptions, without significant emissions.

Comparison of byproduct formation in waters treated with chlorine and iodine: relevance to point-of-use treatment

Due to their efficacy in deactivating a range of microbial pathogens, particularly amoebic cysts, iodine-based disinfectants have been a popular option for point-of-use (POU) drinking water disinfection by campers, the military, and rural consumers in developing countries. Recently, concerns regarding the formation of cytotoxic and genotoxic iodinated disinfection byproducts (I-DBPs) have arisen during chloramine disinfection of iodide-containing waters in the developed world; similar concerns should pertain to iodine-based POU disinfection. Because there are alternative POU disinfection techniques, including chlorine-based disinfectants, this paper compared disinfection byproduct formation from a range of iodine-based disinfectants at their recommended dosages to chlorination and chloramination under overdosing conditions. Just as chloroform was the predominant trihalomethane (THM) forme during chlorination or chloramination, iodoform was the predominant THM formed during iodination. Conditions fostering THM formation were similar between these treatments, except that THM formation during chlorination increased with pH, while it was slightly elevated at circumneutral pH during iodination. Iodoform formation during treatment with iodine tincture was higher than during treatment with iodine tablets. On a molar basis, iodoform formation during treatment with iodine tincture was 20-60% of the formation of chloroform during chlorination, and total organic iodine (TOI) formation was twice that of total organic chlorine (TOCl), despite the 6-fold higher oxidant dose during chlorination. Based upon previous measurements of chronic mammalian cell cytotoxicity for the individual THMs, consumers of two waters treated with iodine tincture would receive the same THM-associated cytotoxic exposure in 4-19 days as a consumer of the same waters treated with a 6-fold higher dose of chlorine over 1 year. Iodoacetic acid, diiodoacetic acid, and other iodo-acids were also formed with iodine tincture treatment, but at levels <11% of iodoform. However, testing of a Lifestraw Personal POU device, which combines an iodinated anion exchange resin with activated carbon post-treatment, indicated minimal formation of I-DBPs and no iodine residual. Although N-nitrosamines have been associated with oxidant contact with anion exchange resins, N-nitrosamine formation rapidly declined to low levels (4 ng/L) using the Lifestraw device after the first few flushes of water.

Simultaneous potentiometric determination of cationic and ethoxylated nonionic surfactants in liquid cleaners and disinfectants

A sensitive potentiometric surfactant sensor based on a highly lipophilic 1,3-didecyl-2-methyl-imidazolium cation and a tetraphenylborate (TPB) antagonist ion was used as the end-point detector in ion-pair potentiometric surfactant titrations using sodium TPB as a titrant. Several analytical and technical grade cationic and ethoxylated nonionic surfactants (EONS) and mixtures of both were potentiometrically titrated. The sensor showed satisfactory analytical performances within a pH range of 3-10 and exhibited satisfactory selectivity for all CS and EONS investigated. Ionic strength did not influence the titration except at 0.1M NaCl, in which a slight distortion of the second inflexion corresponded with the nonionic surfactant. Two-component combinations of four CS and three EONS were potentiometrically titrated using the sensor previously mentioned as the end-point detector. The quantities of the surfactants varied between 2 and 6 μmol for CS and 2.50 and 7.50 μmol for EONS. The known addition methodology was used for determination of the surfactant with considerably lower concentration in the mixture. Three commercial products containing cationic surfactants as disinfectants and nonionic surfactants were potentiometrically titrated, and the results for both type of surfactants were compared with those obtained with standard conventional methods.