The occurrence of haloanisoles as an emerging odorant in municipal tap water of typical cities in China

Pooled Nanoparticle Screening Using a Chemical Barcoding Approach

We report the development of a small molecule-based barcoding platform for pooled screening of nanoparticle delivery. Using aryl halide-based tags (halocodes), we achieve high-sensitivity detection via gas chromatography coupled with mass spectrometry or electron capture. This enables barcoding and tracking of nanoparticles with minimal halocode concentrations and without altering their physicochemical properties. To demonstrate the utility of our platform for pooled screening, we synthesized a halocoded library of polylactide-co-glycolide (PLGA) nanoparticles and quantified uptake in ovarian cancer cells in a pooled manner. Our findings correlate with conventional fluorescence-based assays. Additionally, we demonstrate the potential of halocodes for spatial mapping of nanoparticles using mass spectrometry imaging (MSI). Halocoding presents an accessible and modular nanoparticle screening platform capable of quantifying delivery of pooled nanocarrier libraries in a range of biological settings.

Trace analysis of taste and odour compounds in drinking water by stir bar sorptive extraction followed by thermal desorption - gas chromatography - mass spectrometry (SBSE-TD-GC-MS)

Because of negative tap water quality perception, people often prefer bottled water over tap water despite the higher energy consumption and production of plastic waste. Taste and odour (T&O) deviations in tap water are an important aspect of this issue and should be avoided. However, T&O compounds typically occur at low concentrations (≤ ng.L-1) and are numerous, originating from various sources, ranging from source water to kitchen taps. Consequently, unravelling T&O events is challenging and causing compounds may remain unknown. Therefore, a multi-compound method (SBSE-TD-GC-MS) was developed, optimised and validated for the simultaneous trace analysis of 45 T&O compounds in drinking water. It covers key compounds of different odour categories with a wide range of physical-chemical properties and originating from the different steps of production and distribution. The intra- and interday precision of the method was shown by relative standard deviations (RSD) lower than 15 % and 23 %, respectively, for 75 % of the measured concentrations. For most of the compounds (>75 %), the detection capability (CCβ) was below 1/3rd of their lowest reported odour threshold concentration (OTC), while for the other 6 compounds, the CCβ was within the reported OTC range. Additionally, the CCβs were comparable to or lower than those in literature. As a proof of concept, the method was used to investigate the occurrence and concentrations of T&O compounds before (surface water) and after drinking water production. The results show a clear removal of compounds related to microbial activity (e.g. geosmin, 2-methylisoborneol, 2,4,6-tribromoanisole) after treatment and an increase of compounds related to disinfection. Although rarely investigated, 3-methylbutanal showed concentrations similar to its OTC in treated drinking water, emphasizing the necessity of a broad ultra-trace analysis to ultimately prevent the occurrence of T&O compounds and guarantee tap water quality.

Pooled nanoparticle screening using a chemical barcoding approach

We report the development of a small molecule-based barcoding platform for pooled screening of nanoparticle delivery. Using aryl halide-based tags (halocodes), we achieve high-sensitivity detection via gas chromatography coupled with mass spectrometry or electron capture. This enables barcoding and tracking of nanoparticles with minimal halocode concentrations and without altering their physicochemical properties. To demonstrate the utility of our platform for pooled screening, we synthesized a halocoded library of polylactide-co-glycolide (PLGA) nanoparticles and quantified uptake in ovarian cancer cells in a pooled manner. Our findings correlate with conventional fluorescence-based assays. Additionally, we demonstrate the potential of halocodes for spatial mapping of nanoparticles using mass spectrometry imaging (MSI). Halocoding presents an accessible and modular nanoparticle screening platform capable of quantifying delivery of pooled nanocarrier libraries in a range of biological settings.

Novel and Simple Method for Quantification of 2,4,6-Trichlorophenol with Microbial Conversion to 2,4,6-Trichloroanisole

Contamination with 2,4,6-trichloroanisole (TCA) often causes taste and odor (T&O) problems in drinking water due to its low odor threshold concentration. Microbial O-methylation of the precursor 2,4,6-trichlorophenol (TCP) would be the dominant mechanism for TCA formation. Simple and rapid measurement of TCP in the low concentration range is necessary to control the problems induced by TCA. In this study, the combination of microbial conversion and instrumental analysis was proposed as a method of TCP quantification. Fungi and bacteria were isolated from various water samples and examined for their ability to produce TCA from TCP. As a result, a strain exhibiting quantitative TCA production and a high growth rate was obtained and named Mycolicibacterium sp. CB14. The conversion rate of TCP to TCA by this strain was found to be high and stable (85.9 ± 5.3%), regardless of the applied TCP concentration, although within the range of 0.1-10 µg/L. The limits of detection and quantification for TCP by this proposed method were determined to be 5.2 ng/L and 17.3 ng/L, respectively. By improving the methods, Mycolicibacterium sp. CB14 could be used for the quantification of TCP at very low concentration levels, which is sufficient to manage the T&O problem caused by TCA.

Comparative studies of transformation behaviors and mechanisms of halophenols in multiple chemical oxidative systems

Due to wide applications, halophenols (HPs), especially bromophenols, chlorophenols, and fluorophenols, are commonly detected but resistant to biological removal in wastewater treatment plants (WWTPs). This study investigated the overall transformation behaviors of three representative HPs (2,4-dichlorophenol: 24-DCP, 2,4-dibromophenol: 24-DBP, 2,4-difluorophenol: 24-DFP) in six chemical oxidative systems (KMnO₄, K₂FeO₄, NaClO, O₃, UV, and persulfate (PS)). The results revealed fast removal of selected HPs by O₃, PS and K₂FeO₄, while a large discrepancy in their removal efficiencies occurred under UV irradiation, KMnO₄ oxidation and particularly chlorination. Based on the analysis of the identified intermediates and products, coupling among the five routes was the general route, and dimers were the main intermediates for HP oxidation. The effect of the halogen atom on the transformation pathways of HPs was highly reaction type dependent. Among the six chemical treatments, PS could induce HPs to yield relatively low-molecular-weight polymers and obtain the highest coupling degree. Transition state (TS) calculations showed that the H atom linked to the phenoxy group of HPs was the most easily abstracted by hydroxyl radicals to form the coupling precursor, i.e., phenoxy radicals. This high coupling behavior further resulted in the increased toxicity to green algae. Characterization revealed that HP reaction solutions treated with PS had a severely negative effect on algae growth, photosynthetic pigment synthesis, and the antioxidant enzyme system. These findings can shed light on the reaction mechanisms of advanced oxidation technologies and some risk management and control of PS technique may be considered when treating phenolic pollutants.

Uncorking Haloanisoles in Wine

Haloanisoles in wine have devastating effects on the aroma and quality of the wine. 2,4,6-trichloroanisole (TCA) was discovered and coined as “cork taint” in 1982. However, we now understand that there are many more haloanisoles that contribute to these musty odors, including 2,4,6-Tribromoanisiole (TBA), 2,3,4,6-tetrachloroanisole (TeCA), and pentachloroanisole (PCA). While TCA, TeCA, and PCA can all be traced back to the cork, TBA’s phenol precursor is ubiquitous in building material as a fire retardant, making it a much larger vector. All haloanisoles have the ability to aerosolize and resettle onto surfaces in the winery, making this a very difficult problem to eliminate. This literature review will cover the multiple haloanisoles found in wine, their sensory impacts, their effect on wine quality, and current methodologies with regard to their analysis.

Degradation of odorous 2,4,6-trichloroanisole in chlorinated water by UV-LED/chlorination: kinetics and influence factors

2,4,6-Trichloroanisole (2,4,6-TCA) has aroused a special concern for their odor problem and potential threats. In this study, the degradation of 2,4,6-TCA by UV/chlorination with different UV sources was compared, including low-pressure mercury lamp (LPUV, 254 nm) and ultraviolet light-emitting diode (UV-LED, 275 and 285 nm). The maximum removal of 2,4,6-TCA can be achieved by 275-nm UV-LED/chlorination in neutral and alkaline conditions which was 80.0%. The reaction, kinetics, and water matrix parameters on 2,4,6-TCA degradation were also evaluated. During UV-LED (275 nm)/chlorination, 2,4,6-TCA degradation was mainly caused by direct UV photolysis and indirect hydroxyl radical (HO·) oxidation, while reactive chlorine radicals (RCSs) had a negligible contribution. The second-order rate constant between HO· and 2,4,6-TCA was determined as 3.1 × 10⁹ M^-1 s^-1. Increasing initial chlorine dosage and decreasing 2,4,6-TCA concentration or pH value significantly promoted 2,4,6-TCA degradation during UV/chlorination process. The presence of natural organic matter (NOM) and bicarbonate (HCO₃^-) can inhibit 2,4,6-TCA degradation, while chloride ion (Cl^-) had a negligible effect. The kinetic model for 2,4,6-TCA degradation was established and validated, and the degradation pathways were proposed based on the identified intermediates. Furthermore, UV-LED (275 nm)/chlorination also exhibited a promising effect on 2,4,6-TCA removal in real water, which can be used to control 2,4,6-TCA pollution and odor problems.

Management of biogenic taste and odour: From source water, through treatment processes and distribution systems, to consumers

Biogenic taste and odour (T&O) have become a global concern for water utilities, due to the increasing frequency of algal blooms and other microbial events arising from the combined effects of climate change and eutrophication. Microbially-produced T&O compounds impact source waters, drinking water treatment plants, and drinking water distribution systems. It is important to manage across the entire biogenic T&O pathway to identify key risk factors and devise strategies that will safeguard the quality of drinking water in a changing world, since the presence of T&O impacts consumer confidence in drinking water safety. This study provides a critical review of current knowledge on T&O-causing microbes and compounds for proactive management, including the identification of abiotic risk factors in source waters, a discussion on the effectiveness of existing T&O barriers in drinking water treatment plants, an analysis of risk factors for biofilm growth in water distribution systems, and an assessment of the impacts of T&O on consumers. The fate of biogenic T&O in drinking water systems is tracked from microbial production pathways, through the release of intracellular T&O by cell lysis, to the treatment of microbial cells and dissolved T&O. Based on current knowledge, five impactful research and management directions across the T&O pathway are recommended.

Contaminant Fate and Transport Modeling in Distribution Systems: EPANET-C

Typically, computer-based tools built on mathematical models define the time-series behavior of contaminants, in dissolved or colloidal form, within the spatial boundaries of water distribution systems (WDS). EPANET-MSX has become a standard tool for WDS quality modeling due to its collaboration with EPANET. The critical challenges in applying EPANET-MSX include conceptualizing the exchanges among multiple reacting constituents within the WDS domain and developing the scientific descriptions of these exchanges. Moreover, due to its complicated user interface, the EPANET-MSX application demands programming skills from a software engineering viewpoint. The present study aims to overcome these challenges by developing a novel computer-based tool, EPANET-C. Via built-in and customizable conceptual and mathematical models’ directories, EPANET-C simplifies WDS water quality modeling for users, even those lacking programming expertise. Due to its flexibility, EPANET-C can become a de facto standard tool in WDS quality modeling study both for the industry and the academia.

Simulation degradation of bromophenolic compounds in chlorine-based advanced oxidation processes: Mechanism, microscopic and apparent kinetics, and toxicity assessment

Chlorine-based advanced oxidation processes (AOPs) have been extensively studied to remove contaminants through generating HO^• and reactive chlorine species, including ClO^• and Cl^•. In this work, 2,4,6-tribromoanisole (246TBA) and 2,4,6-tribromophenol (246TBP) were selected as model to investigate the reaction mechanisms and micro-kinetics of brominated contaminants with HO^•, ClO^• and Cl^• in chlorine-based AOPs. Also, the apparent degradation kinetics of two compounds were simulated at pH 3.0-9.5 under UV/H₂O₂, UV/chlorine and UV/NH₂Cl. Calculated results showed that neutral 246TBA and 246TBP exhibited similar reactivity to HO^• and ClO^•, which was different from anionic 2,4,6-tribromophenolate (246TBPT): radical adduct formation (RAF) and H atom abstraction (HAA) were predominant mechanisms for the HO^• and ClO^• initiated reactions of 246TBA and 246TBP, while RAF and single electron transfer (SET) for 246TBPT; the reaction rate constants of 246TBA and 246TBP with HO^• and ClO^• were lower than 10⁷ M^-1 s^-1, and such rate constants dramatically increased to 10¹⁰ M^-1 s^-1 once 246TBP was deprotonated to 246TBPT. The apparent degradation kinetics of 246TBA at pH 3.0-9.5 was simulated in the order of UV/NH₂Cl > UV/chlorine > UV/H₂O₂, and UV/chlorine and UV/NH₂Cl were more effective for the removal of 246TBP and 246TBPT than UV/H₂O₂. UV and/or Cl^• dominated 246 TBA degradation under three AOPs. The main radicals mediating 246TBP and 246TBPT degradation are respectively HO^• under UV/H₂O₂, ClO^• under UV/chlorine, and HO^• and Cl^• under UV/NH₂Cl. The transformation products of 246TBA, 246TBP and 246TBPT, especially methoxylated and hydroxylated polybrominated diphenyl ethers (MeO-PBDEs and HO-PBDEs), were still toxic pollutants.

Computational insight into biotransformation of halophenols by cytochrome P450: Mechanism and reactivity for epoxidation

Halophenols (XPs) have aroused great interests due to their high toxicity and low biodegradability. Previous experimental studies have shown that XPs can be catalytically transformed into epoxides and haloquinones by cytochrome P450 enzymes (CYPs). However, these metabolites have never been detected directly. Moreover, the effects of the reaction site and the type and number of halogen substituents on the biotransformation reactivity of halophenols still remain unknown. In this work, we performed density functional theory (DFT) calculations to simulate the CYP-mediated biotransformation of 36 XPs with mono-, di-, and tri-halogen (F, Cl, and Br) substitutions to unravel the mechanism and relevant kinetics of XPs epoxidation. The whole epoxidation process consists of initial rate-determining O-addition and subsequent ring-closure steps. The simulation results show that the epoxidation in low-spin (LS) state is kinetically preferred over that in high-spin (HS) state, and the formation of epoxide metabolite is strongly exothermic. For all XPs, the epoxidation reactivity follows the order of ortho/para O-addition > meta O-addition. Moreover, the O-addition with higher energy barriers roughly corresponds to chlorophenols and fluorophenols with more halogen atoms. Compared with dichlorophenols, the additional ortho-Cl substitution on trichlorophenols can slightly increase the energy barriers of meta O-addition. By contrast, the additional inclusion of an ortho-Cl to monochlorophenols enhances the meta O-addition reactivity of dichlorophenols. Overall, the present work clarifies the biotransformation routes of XPs to produce epoxides, and identifies the key factors affecting the epoxidation reactivity, which are beneficial in understanding comprehensively the metabolic fate and toxicity of XPs.

Simultaneous removal of ammonia and volatile organic compounds from composting of dead pigs and manure using pilot-scale biofilter

Odor emission is one of the most common problems associated with dead animals composting. Biofiltration treatment for eliminating exhaust odors formed during dead pigs and manure composting has been studied. The composting and biofiltration process consisted of two series of tests. Composting experimental trials lasted 6 weeks, and composting was performed using six pilot-scale reactor vessels. A total of 37 kinds of volatile organic compounds (VOCs) present in the air were identified, and temporal variations were determined during the 42 days of composting. Dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), and trimethylamine (TMA) were identified as the main odors VOCs component according to odor active values (OAVs). Nine biofilter vessels containing mature compost were used in studying the effect of different (30, 60, and 100 s) empty bed retention times (EBRT) on the simultaneous removal efficiencies (REs) of NH₃, DMS, DMDS, DMTS, and TMA. Results indicated that the inlet concentration of NH₃ applied was 12-447 mg m^-3, and the average removal efficiencies were 85.4%, 88.7%, and 89.0% for EBRTs of 30, 60, and 100 s, respectively. The average REs of DMS, DMDS, DMTS, and TMA were 79.2%-95.4%, 81.9%-94.0%, 76.7%-99.1%, and 92.9%-100%, respectively, and their maximum elimination capacity (ECs) were 220, 1301, 296, and 603 mg m^-3 h^-1, respectively. The optimal EBRT for the stimulation removal of NH₃, DMS, DMDS, DMTS, and TMA was 60 s.Implications: Dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), and trimethylamine (TMA) were identified as the main odors VOCs component during dead pigs and manure composting. Biofilter with mature as media can be used to stimulation remove NH₃, DMS, DMDS, DMTS, and TMA, the optimal empty bed retention times EBRT was 60 s.

Modeling the Formation and Propagation of 2,4,6-trichloroanisole, a Dominant Taste and Odor Compound, in Water Distribution Systems

2,4,6-trichloroanisole (2,4,6-TCA) formation is often reported as a cause of taste and odor (T&O) problems in water distribution systems (WDSs). The biosynthesis via microbial O-methylation of 2,4,6-trichlorophenol (2,4,6-TCP) is the dominant formation pathway in distribution pipes. This paper attempted to utilize the reported data on the microbial O-methylation process to formulate deterministic kinetic models for explaining 2,4,6-TCA formation dynamics in WDSs. The pipe material’s critical role in stimulating O-methyltransferases enzymatic activity and regulating 2,4,6-TCP bioconversion in water was established. The kinetic expressions formulated were later applied to develop a novel EPANET-MSX-based multi-species reactive-transport (MSRT) model. The effects of operating conditions and temperature in directing the microbiological, chemical, and organoleptic quality variations in WDSs were analyzed using the MSRT model on two benchmark systems. The simulation results specified chlorine application’s implication in maintaining 2,4,6-TCA levels within its perception limit (4 ng/L). In addition, the temperature sensitivity of O-methyltransferases enzymatic activity was described, and the effect of temperature increase from 10 to 25 °C in accelerating the 2,4,6-TCA formation rate in WDSs was explained. Controlling source water 2,4,6-TCP concentration by accepting appropriate treatment techniques was recommended as the primary strategy for regulating the T&O problems in WDSs.

Biotransformation of halophenols into earthy-musty haloanisoles: Investigation of dominant bacterial contributors in drinking water distribution systems

Microorganisms in drinking water distribution systems (DWDSs) can O-methylate toxic halophenols (HPs) into earthy-musty haloanisoles (HAs). However, the dominant HA-producing bacterial species and their O-methylation properties are still unknown. In this study, eight bacterial strains from DWDS were isolated and the community abundances of the related genera in bulk water and biofilms as well as their O-methylation properties were investigated. Among the genera discovered in this study, Sphingomonas and Pseudomonas are dominant and play important roles in DWDSs. All bacteria could simultaneously convert five HPs to the corresponding HAs. Two Sphingomonas ursincola strains mainly produced 2,3,6-trichloroanisole (2,3,6-TCA) (2.48 × 10^-9-1.18 × 10^-8 ng/CFU), 2,4,6-trichloroanisole (2,4,6-TCA) (8.12 × 10^-10-3.11 × 10^-9 ng/CFU) and 2,4,6-tribromoanisole (2,4,6-TBA) (2.95 × 10^-9-3.21 × 10^-9 ng/CFU), while two Pseudomonas moraviensis strains preferred to generate 2-monochloroanisole (2-MCA) (1.19 × 10^-9-3.70 × 10^-9 ng/CFU) and 2,4-dichloroanisole (2,4-DCA) (3.81 × 10^-9-1.20 × 10^-8 ng/CFU). Among the chloramphenicol-susceptible strains, four strains contained inducible O-methyltransferases (OMTs), while the O-methylations of the others were expressed constitutively. All bacteria could use S-adenosyl methionine as methyl donor. Potential taste and odor (T & O) risks of five HAs in DWDS followed an order of 2,4,6-TBA > 2,4,6-TCA > 2,3,6-TCA > 2,4-DCA > 2-MCA. The recommended 2,4,6-TCP criteria for T & O control is 0.003-0.07 mg/L.

Kinetic and mechanistic investigation into odorant haloanisoles degradation process by peracetic acid combined with UV irradiation

This study reported the kinetics and mechanism of degradation of odorant haloanisoles by peracetic acid combined with UV irradiation (PAA/UV). The removal efficiency of haloanisoles by PAA/UV was more than 92 % after 1 h reaction at pH 5, 25 °C, [HAs] =50 μg/L and [PAA] = 10 mg/L. The degradation of haloanisoles was fitted by the first-order kinetic model, and the rate constants of various haloanisoles followed the order: 2,4,6-tribromoanisole (2,4,6-TBA, (9.25 ± 0.71)×10^-2 s^-1) > 2-monochloroanisole (2-MCA, (8.00 ± 0.34)×10^-2 s^-1) > 2,4-dichloroanisole (2,4-DCA, (6.24 ± 0.55)×10^-2 s^-1) > 2,4,6-trichloroanisole (2,4,6-TCA, (5.05 ± 0.04)×10^-2 s^-1). The contribution of PAA (mainly composed of free radicals produced from PAA activation by UV) to the degradation rate of chloroanisoles in PAA/UV process ranged from 24 % to 36 %, while 25 % to the degradation rate of bromoanisole. Direct photolysis contributed much more to the removal of bromoanisole (42 %) than chloroanisoles (9-14 %). The inhibition of tert-butanol on degradation demonstrated the existence of ·OH, and superoxide radical and carbon-centered radicals were also probably existed in PAA/UV process. Combining density functional theory (DFT) calculation and products analysis, the degradation pathway of haloanisoles in PAA/UV process were determined. The odor and toxicity evaluation indicated PAA/UV process could reduce olfactory discomfort and health risk of haloanisoles.

Ultraviolet-mediated peroxymonosulfate diminution of earthy and musty compound trichloroanisole in water

Taste and odor (T&O) problem in water is one of the main obstacles to improve the quality of drinking water, and efficient water treatment processes are urgently needed to control T&O compounds. Ultraviolet-mediated peroxymonosulfate (UV/PMS) diminution of trichloroanisole (TCA) in water was investigated in this paper. The treatment of 2,3,6-trichloroanisole (2,3,6-TCA) by three advanced oxidation processes (UV, UV/H₂O₂ and UV/PMS) was compared, and UV/PMS stood out. SO₄^•- and HO• were produced in the UV/PMS, and their specific contributions to 2,3,6-TCA oxidation were investigated. The competitive kinetic model was applied to determine the second-order reaction rate between 2,3,6-TCA and SO₄^•- or HO•. The products of 2,3,6-TCA generated in UV/PMS were analyzed with gas chromatography/high resolution-mass spectrometry (GC/HR-MS), and the degradation mechanism was proposed. The effects of water matrices (chloride, bicarbonate and humic acid) on UV/PMS performance were studied, and the decontamination of 2,3,6-TCA in real water was carried out. The disinfection byproducts (DBPs) alteration from 2,3,6-TCA by UV/PMS - chlorination treatment was explored. Overall, UV/PMS can effectively deal with the T&O pollution of TCA in water.

Health impact of odor from on-situ sewage sludge aerobic composting throughout different seasons and during anaerobic digestion with hydrolysis pretreatment

Aerobic composting and anaerobic digestion with hydrolysis pretreatment are two mainstream methods used to recycle and reclaim sewage sludge. However, during these sludge treatment processes, many odors are emitted that may cause severe emotional disturbance and health risks to those exposed. This study identified odor pollution (i.e. sensory influence, odor contribution, and human risks) from samples collected during sludge aerobic composting throughout different seasons as well as during anaerobic digestion with hydrolysis pretreatment. Odor intensity, odor active values, and permissible concentration-time weighted averages for ammonia and five volatile sulfur compounds were assessed. The results revealed serious odor pollution from all sampling sites during aerobic composting, especially in winter. Excessively strong odors were identified in the composting workshop, with total odor active values between 997 and 8980 which accounted for 78.45%-96.18% of the total sludge aerobic composting plant. Levels of ammonia and dimethyl disulfide in the ambient air were high enough to harm employees' health. During anaerobic digestion, excessively strong odors were identified in dehydration workshop 2, and the total odor active values of six odors reached 32,268, with ammonia and hydrogen sulfide levels significant enough to harm human health.

Elimination of trichloroanisoles by UV/H2O2: Kinetics, degradation mechanism, water matrix effects and toxicity assessment

The elimination of 2,3,6-trichloroanisole (2,3,6-TCA), which produces a musty-earthy off-odor in water, by an ultraviolet (UV)/H₂O₂ process was assessed. The removal of 88.1% of 2,3,6-TCA in ultrapure water (UPW) was achieved using an initial 2,3,6-TCA concentration of 1 μg L^-1 (4.73 nM), a H₂O₂ concentration of 20 mg L^-1 (0.588 mM), a UV intensity of 1.44 mW cm^-2 and a pH of 8.2. The reaction was found to be pseudo first order with a rate constant (k_obs) of 0.0340 min^-1. Both the removal efficiency and k_obs increased significantly upon increasing the H₂O₂ concentration from 10 to 50 mg L^-1. The second order rate constant (k_{HO·,2,3,6-TCA}) in competition kinetic trials was determined to be 8.17 × 10⁷ M^-1s^-1. Degradation products generated during both the UV photolysis and UV/H₂O₂ treatment of 2,3,6-TCA solutions were analyzed using ultrahigh resolution gas chromatography/mass spectrometry, and the degradation mechanism was proposed. The toxicities of water solutions during both processes were assessed via a luminescence method in conjunction with Vibrio fischeri. The pH and Cl^-, HCO₃^- and natural organic matter concentrations of the aqueous medium were all found to significantly affect the removal of 2,3,6-TCA. The degradation rates of trichloroanisoles (TCAs) in real-world water samples demonstrated that UV/H₂O₂ has significant potential with regard to controlling TCAs as pollutants in water.

Formation of odorant haloanisoles and variation of microorganisms during microbial O-methylation in annular reactors equipped with different coupon materials

Taste and odor (T & O) issues in drinking water have become serious problems which cannot be ignored by customers. Several studies have confirmed that microbes in water can biotransform halophenols (HPs) to haloanisoles (HAs) with earthy and musty flavors via microbial O-methylation. In this paper, the formation of 2-chloroanisole (2-CA), 2,4-dichloroanisole (2,4-DCA), 2,4,6-trichloroanisole (2,4,6-TCA), 2,3,6-trichloroanisole (2,3,6-TCA) and 2,4,6-tribromoanisole (2,4,6-TBA), and the microbial variation during the microbial O-methylation were investigated in annular reactors (ARs) with three coupon materials. For precursors, 42.5% of 2-CP and 68.9% of 2,4-DCP decayed during the reaction. Among the five HAs, the formation rate constant followed an order of 2,4,6-TCA > 2-CA > 2,4,6-TBA > 2,4-DCA ~ 2,3,6-TCA, while [HA]_max followed a totally opposite one. The simulated flow velocity had no significant effect (p > 0.05) on HA formation. Ductile iron (DI) AR could produce more HAs than stainless steel (SS) and polyvinyl chloride (PVC) ARs. The final HA molar concentration followed an order of 2,3,6-TCA > 2,4-DCA > 2,4,6-TBA ~ 2,4,6-TCA > 2-CA, which might be explained by multiple factors including HP's dissociation degree, halogen atom's steric hindrance and specificity of HP O-methyltransferases. During the reaction, the microbial biomass dramatically increased 6.8-9.0 times in bulk water but dropped significantly on coupon biofilms. The effect of HPs significantly changed the bacterial communities on coupon in terms of composition and diversity, and declined the relative abundance of HA-producing bacteria, while fungi and their HA-producing genus showed better resistance ability towards HPs. By using Pearson correlation analysis, a significant correlation (p = 0.0003) was found between [HA]_max and initial coupon biofilm biomass. Finally, a linear relationship was established between initial total biomass and HA formation potential.

Odor assessment of NH3 and volatile sulfide compounds in a full-scale municipal sludge aerobic composting plant

Methods for assessing odors in municipal sewage sludge aerobic composting plants (MSSACPs) have been ineffective. This study identified the emission amount of typical odor-producing compounds, including NH₃ and volatile sulfide compounds from a full-scale MSSACP, and evaluated risks of odor emissions based on odor intensity and odor active value. Results revealed all sampling sites (i.e. sludge stacking yard, composting workshop, and screening workshop) produced serious odors, especially in the composting workshop. In the composting workshop, the amounts of DMDS (174.59 μg·dry kg^-1) and DMS (71.64 μg·dry kg^-1) emitted were far lower than that of NH₃ (6062.56 μg·dry kg^-1). However, DMDS and DMS showed a similar intensity as NH₃ according to odor intensity assessment. Furthermore, both of their odor active values were higher than that of NH₃. Using results from both odor intensity and odor active value were more reliable for the assessment of odors from MSSACPs.

Sunlight caused interference in outdoor N, N-diethyl-p-phenylenediamine colorimetric measurement for residual chlorine and the solution for on-site work

Chlorination is the most common method to control water qualities, in some case on-site outdoor measurements are required to measure easily-decaying residual chlorine concentration appropriately without delay. In this study sunlight-induced unexpected colour development (UCD) of N, N-diethyl-p-phenylenediamine (DPD) colorimetric measurement was studied under several sun exposure conditions. The colour development level was evaluated with reference to chlorine concentration (mg/L) and relationships between colour development rate (mg/L min) and intensities of solar were investigated. UCD was found to be related to both exposure intensity and time. By means of exposure experiment under specific wavelength of ultraviolet (UV), it was confirmed that both middle and short wavelength of UV radiation being responsible for such an unexpected measurement. Consequently, a simple device was designed using three commercially available anti-UV films, one of which could effectively prevent the UCD from direct sun exposure.

Electroactive Modified Carbon Nanotube Filter for Simultaneous Detoxification and Sequestration of Sb(III)

Herein, we rationally designed a dual-functional electroactive filter system for simultaneous detoxification and sequestration of Sb(III). Binder-free and nanoscale TiO₂-modified carbon nanotube (CNT) filters were fabricated. Upon application of an external electrical field, in situ transformation of Sb(III) to less toxic Sb(V) can be achieved, which is further sequestered by TiO₂. Sb(III) removal kinetics and capacity increase with applied voltage and flow rate. This can be explained by the synergistic effects of the filter's flow-through design, electrochemical reactivity, small pore size, and increased number of exposed sorption sites. STEM characterization confirms that Sb were mainly sequestered by TiO₂. XPS, AFS, and XAFS results verify that the Sb(III) conversion process was accelerated by the electrical field. The proposed electroactive filter technology works effectively across a wide pH range. The presence of sulfate, chloride, and carbonate ions negligibly inhibited Sb(III) removal. Exhausted TiO₂-CNT filters can be effectively regenerated using NaOH solution. At 2 V, 100 μg/L Sb(III)-spiked tap water generated ∼1600 bed volumes of effluent with >90% efficiency. Density functional theory calculations suggest that the adsorption energy of Sb(III) onto TiO₂ increases (from -3.81 eV to -4.18 eV) and Sb(III) becomes more positively charged upon application of an electrical field.

Nanoscale iron (oxyhydr)oxide-modified carbon nanotube filter for rapid and effective Sb(iii) removal

Herein, nanoscale iron (oxyhydr)oxide-coated carbon nanotube (CNT) filters were rationally designed for rapid and effective removal of Sb(iii) from water. These iron (oxyhydr)oxide particles (<5 nm) were uniformly coated onto the CNT sidewalls. The as-fabricated hybrid filter demonstrated improved sorption kinetics and capacity compared with the conventional batch system. At a flow rate of 6 mL min⁻¹, a Sb(iii) pseudo-first-order adsorption rate constant of 0.051 and a removal efficiency of >99% was obtained when operated in the recirculation mode. The improved Sb(iii) sorption performance can be ascribed to the synergistic effects of convection-enhanced mass transport, limited pore size, and more exposed active sorption sites of the filters. The presence of 1–10 mmol L⁻¹ of carbonate, sulfate, and chloride inhibits Sb(iii) removal negligibly. Exhausted hybrid filters can be effectively regenerated by an electrical field-assisted chemical washing method. STEM characterization confirmed that Sb was mainly sequestered by iron (oxyhydr)oxides. XPS, AFS and XAFS results suggest that a certain amount of Sb(iii) was converted to Sb(v) during filtration. DFT calculations further indicate that the bonding energy for Sb(iii) onto the iron (oxyhydr)oxides was 2.27–2.30 eV, and the adsorbed Sb(iii) tends to be oxidized.

Herein, nanoscale iron (oxyhydr)oxide-coated carbon nanotube (CNT) filters were rationally designed for rapid and effective removal of Sb(iii) from water.

Measurement of volatile organic compounds and associated risk assessments through ingestion and dermal routes in Dongjiang Lake, China

This study aims to investigate the occurrence, distribution and risk assessment of volatile organic compounds (VOCs) in Dongjiang Lake of China. Twenty two kinds of VOCs were detected, and the major VOCs were alkene compounds. The total concentration of VOCs (∑VOCs) ranged from 2.93 to 4.69 µg/L, and none of the VOCs detected in Dongjiang Lake exceeded the concentration limits set in the National Drinking Water Quality Standards (GB5749-2006) or the National Environmental Quality Standards for Surface Water (GB3838-2002) of China. Risk quotients (RQ) model, Multimedia Environment Pollutant Assessment System (MEPAS) and value of odor hazard index (OHI) were used to assess the ecological risk, lifetime carcinogenic risk and olfactory risk of VOCs in Dongjiang Lake, respectively. The RQ_total values varied from 3.95 × 10^-3 to 0.34 and the RQ values for all the 22 detected VOCs in 12 sample locations of Dongjiang Lake were below 0.01, which means negligible risk to aquatic organisms. The cancerous and non-cancerous risk indices were in the range of 2.31 × 10^-9-5.16 × 10^-7 and 1.68 × 10^-7-1.45 × 10^-2, respectively. Bromodichloromethane and 1,1-dichloroethene were associated with the highest and lowest carcinogenic risks in all 12 sample locations. Results also demonstrated that the olfactory risk in Dongjiang Lake is negligible. These data suggest that the VOCs in Dongjiang Lake may not lead great ecological and health risks for organism and human.

Factors affecting the water odor caused by chloramines during drinking water disinfection

Chloramine disinfection is one of the most common disinfection methods in drinking water treatment. In this study, the temporal variability of water odors during monochloramine auto-decomposition was investigated to elucidate the characteristics of odor problems caused by adopting chloramine disinfection in tap water. Odor intensities and dominant odorant contributions were determined using the flavor profile analysis (FPA) and odor active value (OAV), respectively. During auto-decomposition of monochloramine, Cl₂/N molar ratio, pH, temperature, and the presence of NOM all affected odor intensity and odor temporal variation in drinking water. In general, decreasing pH from 8.5 to 6.0 led to increasing perceived odor intensity due to the formation of dichloramine. The major odorants responsible for chlorinous odor under acidic and non-acidic conditions were dichloramine and monochloramine, respectively. Chloraminated water with a Cl₂/N molar ratio of 0.6 or NOM concentration <2 mg-C L^-1 inhibited odor intensity. Furthermore, the influence of rechlorination on chlorinous odor intensity for chloraminated water should not be neglected. The results of this study will be beneficial for the control of chlorinous odors caused by chloramine disinfection in drinking water.

Pilot investigation on formation of 2,4,6-trichloroanisole via microbial O-methylation of 2,4,6-trichlorophenol in drinking water distribution system: An insight into microbial mechanism

Taste & odor (T&O) problems in drinking water are always complained by customers. Recent studies have indicated biofilms in drinking water distribution system (DWDS) are always ignored as potential sources of T&O compounds. In this paper, the formation of 2,4,6-trichloroanisole (2,4,6-TCA), one of the dominant T&O compounds, was investigated in a pilot-scale DWDS. The addition of precursor 2,4,6-trichlorophenol (2,4,6-TCP) of 0.2 mg/L induced the formation of 2,4,6-TCA with a maximum yield of ∼400 ng/L, and the formation kinetics can be described by a pseudo-first-order kinetic model. Effects of water distribution factors such as pipe material, temperature, flow velocity, and residual chlorine on the formation of 2,4,6-TCA were evaluated, and the pipe material was found to have the most remarkable effect. Ductile iron and stainless steel pipes produced much more 2,4,6-TCA than polyethylene (PE) pipe. The biofilm microbial communities on the three types of pipe walls were then comprehensively analyzed by heterotrophic plate count and 16S rRNA/ITS1 genes high throughput sequencing. The links between the 2,4,6-TCA formation potential and the microbial activity in genus and enzymatic levels in DWDS have been revealed for the first time. According to the characteristics of microbial assemblages of producing 2,4,6-TCA, quorum-sensing (QS) bacterial signaling system and extracellular DNA (eDNA) may be two promising targets for biofilm treatment and 2,4,6-TCA control in DWDS.

Contribution of filamentous fungi to the musty odorant 2,4,6-trichloroanisole in water supply reservoirs and associated drinking water treatment plants

In this study, the distribution of 2,4,6-trichloroanisole (2,4,6-TCA) in two water supply reservoirs and four associated drinking water treatment plants (DWTPs) were investigated. The 2,4,6-TCA concentrations were in the range of 1.53-2.36 ng L^-1 in water supply reservoirs and 0.76-6.58 ng L^-1 at DWTPs. To determine the contribution of filamentous fungi to 2,4,6-TCA in a full-scale treatment process, the concentrations of 2,4,6-TCA in raw water, settled water, post-filtration water, and finished water were measured. The results showed that 2,4,6-TCA levels continuously increased until chlorination, suggesting that 2,4,6-TCA could form without a chlorination reaction and fungi might be the major contributor to the 2,4,6-TCA formation. Meanwhile, twenty-nine fungal strains were isolated and identified by morphological and molecular biological methods. Of the seventeen isolated fungal species, eleven showed the capability to convert 2,4,6-trichlorophenol (2,4,6-TCP) to 2,4,6-TCA. The highest level of 2,4,6-TCA formation was carried out by Aspergillus versicolor voucher BJ1-3: 40.5% of the original 2,4,6-TCP was converted to 2,4,6-TCA. There was a significant variation in the capability of different species to generate 2,4,6-TCA. The results from the proportions of cell-free, cell-attached, and cell-bound 2,4,6-TCA suggested that 2,4,6-TCA generated by fungi was mainly distributed in their extracellular environment. In addition to 2,4,6-TCA, five putative volatile by-products were also identified by gas chromatography and mass spectrometry. These findings increase our understanding on the mechanisms involved in the formation of 2,4,6-TCA and provide insights into managing and controlling 2,4,6-TCA-related problems in drinking water.