Degradation Of Chloroform Research Articles

Performance of Anaerobic Biotrickling Filter and its Microbial Diversity for the Removal of Stripped Disinfection Byproducts.

The objective of this research was to evaluate the biodegradation of chloroform by using biotrickling filter (BTF) and determining the dominant bacteria responsible for the degradation. The research was conducted in three phases under anaerobic condition, namely, in the presence of co-metabolite (Phase I), in the presence of co-metabolite and surfactant (Phase II) and in the presence of surfactant but no co-metabolite (Phase III). The results showed that the presence of ethanol as a co-metabolite provided 49% removal efficiency. The equivalent elimination capacity (EC) was 0.13 g/(m3.hr). The addition of Tomadol 25 - 7 as a surfactant in the nutrient solution increased the removal efficiency of chloroform to 64% with corresponding EC of 0.17 g/(m3.hr). This research also investigated the overall microbial ecology of the BTF utilizing culture-independent gene sequencing alignment of the 16S rRNA allowing identification of isolated species. Taxonomical composition revealed the abundance of deltaproteobacteria and deltaproteobacteria with species level of 97%. A. oryzae (formally dechlorosoma suillum), A. restrica and Geobacter spp. together with other similar groups were the most valuable bacteria for the degradation of chloroform.

Comparative Study on the Performance of Anaerobic and Aerobic Biotrickling Filter for Removal of Chloroform.

Use of biotrickling filter (BTF) for gas phase treatment of volatile trihalomethanes (THMs) stripped from water treatment plants could be an attractive treatment option. The aim of this study is to use laboratory-scale anaerobic BTF to treat gaseous chloroform (recalcitrant to biological transformation) as a model THM and compare results with aerobic BTF. Additional investigations were conducted to determine the microbial diversity present within the BTFs. Chloroform is a hydrophobic volatile THM known to be difficult to biodegrade. To improve the degradation process, ethanol was used as a cometabolite at a different ratio to chloroform. The experimental plan was designed to operate one BTF under anaerobic condition and the other one under aerobic acidic condition. Higher elimination capacity (EC) of 0.23 ± 0.01 g/[m3·h] was observed with a removal efficiency of 80.9% ± 4% for the aerobic BTF operating at pH 4 for the concentration ratio of 1:40 chloroform to ethanol. For similar ratio, the anaerobic BTF supported lower removal efficiency of 59% ± 10% with corresponding lower EC of 0.16 ± 0.01 g/[m3·h]. Carbon recovery acquired for anaerobic and aerobic BTFs was 59% and 63%, respectively. The loading rate for chloroform on both BTFs was 0.27 g/[m3·h] (per m3 of filter bed volume). Variations of the microbial community were attributed to degradation of chloroform in each BTF. Azospira oryzae and Azospira restrica were the dominant bacteria and potential candidates for chloroform degradation for the anaerobic BTF, whereas Fusarium sp. and Fusarium solani were the dominant fungi and potential candidates for chloroform degradation in the aerobic BTF.

Treatment of Organic Pollutants Using a Solar Energy Driven Photo‐Oxidation Device

Two of the main problems of society in the near future are the access to clean water and energy. In particular, organic pollutants can be a major health threat. Within available methods, a trade‐off can be established between the pollutant treatment price and the final pollutant concentration that can be achieved. In this paper, a water treatment device is proposed in order to decouple these two variables. It consists of a BiVO4 photoanode combined with a thin film silicon solar cell. BiVO4 is an earth‐abundant material with a bandgap energy of 2.4 eV. Here, its good catalytic properties are shown for the degradation of phenol and chloroform when combined with an external bias voltage of 1 V versus Ag/AgCl. In addition, to cover the voltage needs, an a‐Si:H/nc‐Si:H solar cell has been coupled with the BiVO4 photoanode. This solar cell has been specifically designed to work under the transmitted spectrum of BiVO4, with thicknesses of 300 and 2000 nm for the top and bottom cell, respectively. This device has successfully been fabricated, and tested for removal of organic contaminants from an aqueous solution, performing even better than the BiVO4 photoanode alone with a similar external bias voltage applied.

Degradation of chloroform by Fenton-like treatment induced by electromagnetic fields: A case of study

The objective of this study of chloroform degradation by the first time through Fenton-like processes induced by electromagnetic fields. Fenton-like processes were carried out at natural pH with 25mg/L of H2O2 and different iron sources: i) FeCl3·6H2O (5, 50 and 100mg/L Fe3+); ii) magnetite (1g/L); iii) clay (80g/L). These treatments were driven in absence and presence of radiofrequency (RF) with an intensity of electromagnetic field of 3.68kA/m. Aqueous solution of chloroform (CHCl3) was also used to study which oxidant species are responsible for the degradation of organic matter. Because of chloroform is scavenger of primary superoxide radicals (•O2−.) and required of hydroxyl radical for their total degradation. Initial assays of ferromagnetic material/H2O2/RF processes achieved promising results in terms of DOC removal. The highest DOC removal yield (69%) in the treatment of an aqueous solution of CHCl3 was obtained by Fenton/RF treatment using 100mg/L of Fe(III) and 25mg/L of H2O2. In addition, the combination of Magnetite and Fe(III) reached notable values of CHCl3 degradation. The synergetic effect caused by the ferromagnetic properties of Magnetite and the coagulation-flocculation effect caused by iron salts at natural pH is able to reduce the organic matter in water samples. Furthermore, this treatment can be intensified by induction of RF reaching 63% of DOC removal in the CHCl3 solution.

Two-stage co-fermentation of lipid-extracted microalgae waste with food waste leachate: A viable way to reduce the inhibitory effect of leftover organic solvent and recover additional energy

This study aimed to mitigate the inhibitory effect of leftover organic solvent (CH3Cl, chloroform) on anaerobic digestion of lipid-extracted microalgae waste (LEMW). Food waste leachate (FWL) was added as a co-substrate and a two-stage fermentation process (H2 production with acidogenesis + methanogenesis) was adopted. The result of the first batch experiment, conducted in the absence of chloroform, showed that as the FWL addition ratio increased up to 60% on chemical oxygen demand (COD) basis, there was a gradual increase in the amount of H2 produced. At 80% addition, however, there was a huge drop in H2 yield, accompanied by a drop in pH. In the presence of chloroform (100–900 mg CH3Cl/L), the mixture (LEMW:FWL = 40:60) exhibited a much higher tolerance than that of LEMW alone, which could be ascribed to the co-metabolic degradation of chloroform by FWL addition. At 600 and 900 mg CHCl3/L, the degradation efficiency dropped below 40% for LEMW alone, while it was maintained above 90% in the mixture. A H2 yield of 36 mL H2/g COD, equivalent to 2.6% of the energy content in the feedstock, was attained from the mixture at 600 mg CHCl3/L. The H2 fermented effluent was then fed to a continuous methanogenic reactor at HRT 40 d, and 82% of energy content in the feedstock was further gained in the form of CH4. Although the energy gained from H2 production was negligible, most of the chloroform was degraded during acidogenesis, which resulted in a successful CH4 conversion.

Preparation of Coated CMC-nZVI Using Rheological Phase Reaction Method and Research on Degradation of Chloroform in Water

This study reported the synthesis of nanoscale zero-valent iron (nZVI) by rheological phase reaction method in the presence of sodium (CMC). The synthesized CMC coated nZVI (CMC-nZVI) was then characterized with x-ray diffraction (XRD) and transmission electron microscope (TEM) and was tested for the removal of chloroform from simulated groundwater. The investigated parameters in the uptake experiments included different adsorbents, initial concentrations of chloroform and different water flow. The results show that:(1) the prepared CMC-nZVI has good stability and dispersibility; (2) when the concentration of chloroform is 0.1 mg/L, the dosage of CMC-Fe0 is 0.01 g, the removal rate of chloroform is 91.2%;(3)The reaction follows the first-order kinetic reaction equation, and the apparent reaction rate constant increases with decreasing the concentration of chloroform.

Temporal hydrochemical and microbial variations in microcosm experiments from sites contaminated with chloromethanes under biostimulation with lactic acid

ABSTRACTThe aim of this research was to identify the sequence of degradation processes that leads to the selective enrichment of microorganisms involved in the degradation of carbon tetrachloride and chloroform under conditions of natural attenuation and lactic acid biostimulation. To this end, a comparative study using microcosm experiments was conducted to analyze these two scenarios. The authors used groundwater and sediment collected from a field site located at a petrochemical complex to create the microcosms. Chemical, compound-specific isotope and microbial analyses were performed. A significant finding of this work was the abiotic degradation of carbon tetrachloride. Another result was the identification of biotic reductive dechlorination of chloroform by a bacterium of the Clostridiales order. This study showed that biostimulation with lactic acid produced faster degradation rates of carbon tetrachloride and chloroform. Lactic acid acted as an electron donor and promoted a decrease in the concentration of other electron acceptors such as nitrate and sulfate, which competed with chloromethanes. Thus, biostimulation could be an efficient remediation strategy for sites contaminated with chloromethanes, especially when a site's complex pollution history results in chemical background concentrations that are high in compounds that could potentially reduce natural attenuation.

High activity and regenerability of a palladium–gold catalyst for chloroform degradation

High activity and regenerability of a palladium–gold catalyst for chloroform degradation

Decomposition of gas-phase chloroform using nanophotocatalyst downstream the novel non-thermal plasma reactor: by-products elimination

Combination the non-thermal plasma technique by photocatalytic oxidation can enhance volatile organic compounds degradation. In this study, the decomposition of chloroform vapors in a novel non-thermal plasma reactor as well as an integrated system of this reactor in conjunction with the photocatalysis process was investigated. Expanded graphite was used as discharge electrode of dielectric barrier discharge reactor and the support of TiO2 and ZnO catalysts as well. Results showed that chloroform degradation increased in hybrid system. The non-thermal plasma reactor had high content of NO and NO2, whereas the concentration of these two pollutants dropped dramatically in hybrid system; moreover, the generated ozone from the non-thermal plasma process was degraded on the photocatalyst and consequently was not detected in the output gas of the combined system. The generated organic by-products in non-thermal plasma process (phosgene and trichloroacetaldehyde) were reoxidized with un-oxidized chloroform in the second stage of the combined system. This increased the selectivity of CO2 and Cl2.

Identification of Active Radical Species in Alkaline Persulfate Oxidation.

A proposed mechanism for alkaline activation of persulfate involves generation of sulfate (SO(4)(-)), hydroxyl (HO·), and superoxide radicals (O(2)(-)). The present study investigated the feasibility of chloroform (CF) degradation using alkaline activated persulfate and identified the active radical species using a radical inhibition technique. 2-propanol (PrOH) (preferentially reacted with HO·), phenol (preferentially reacted with both HO· and SO(4)(-)), and carbon tetrachloride (CT) (preferentially reacted with O(2)(-)) were used to inhibit the degradation of CF, and the extent of inhibited degradation was used to indicate the predominant radical species. Additions of PrOH and phenol appeared to significantly scavenge SO(4)(-) and HO· and resulted in inhibited CF degradation. Here, the authors demonstrated that SO(4)(-) and HO· were predominant radicals in the alkaline activated persulfate system. The presence of O(2)(-) scavengers (i.e., CT) resulted in a partial inhibition of CF degradation and, hence, one can speculate that O(2)(-) is a minor radical species.

The Use of Alkaline Hydrolysis As a Novel Strategy for Chloroform Remediation: The Feasibility of Using Construction Wastes and Evaluation of Carbon Isotopic Fractionation

Laboratory and field-scale pilot experiments were performed to evaluate the feasibility of chloroform degradation by alkaline hydrolysis and the potential of δ(13)C values to assess this induced reaction process at contaminated sites. In batch experiments, alkaline conditions were induced by adding crushed concrete (pH 12.33 ± 0.07), a filtered concrete solution (pH 12.27 ± 0.04), a filtered cement solution (pH 12.66 ± 0.02) and a pH 12 buffer solution (pH 11.92 ± 0.11). The resulting chloroform degradation after 28 days was 94, 96, 99, and 72%, respectively. The experimental data were described using a pseudo-first-order kinetic model, resulting in pseudo-first-order rate constant values of 0.10, 0.12, 0.20, and 0.05 d(-1), respectively. Furthermore, the significant chloroform carbon isotopic fractionation associated with alkaline hydrolysis of chloroform (-53 ± 3‰) and its independence from pH in the admittedly limited tested pH range imply a great potential for the use of δ(13)C values for in situ monitoring of the efficacy of remediation approaches based on alkaline hydrolysis. The carbon isotopic fractionation obtained at the lab scale allowed the calculation of the percentage of chloroform degradation in field-scale pilot experiments where alkaline conditions were induced in two recharge water interception trenches filled with concrete-based construction wastes. A maximum of approximately 30-40% of chloroform degradation was achieved during the two studied recharge periods. Although further research is required, the treatment of chloroform in groundwater through the use of concrete-based construction wastes is proposed. This strategy would also imply the recycling of construction and demolition wastes for use in value-added applications to increase economic and environmental benefits.

Soluble and stable alternating main-chain merocyanine copolymers through quantitative spiropyran–merocyanine conversion

A combined experimental and theoretical study on the synthesis and solution isomerization behavior of main chain copolymers with multiple spiropyran incorporation is presented. A series of alternating copolymers P(SP-alt-Cx) of spiropyran (SP) and flexible linkers (Cx, x = 6,8,10) is synthesized by Suzuki polycondensation (SPC). Careful 1H NMR polymer end group analysis is carried out to reveal termination reactions that limit molecular weight. Although methylene indoline and salicyl aldehyde end groups are found arising from SP cleavage during polymerization, acceptable Mn,SEC up to 34 kg mol−1 is achieved. P(SP-alt-Cx) can be transformed into the corresponding protonated form of the red alternating merocyanine (MC) polymer, P(MCH+-alt-Cx), in quantitative yield by direct acidification or pulsed ultrasound. The origin of the latter method lies in the sonochemical degradation of chloroform, which provides a continuous source of hydrochloric acid. Deprotonation of P(MCH+-alt-Cx) occurs upon the addition of a base resulting in the blue form P(MC-alt-Cx), as characterized by UV-vis spectroscopy and confirmed by density functional theory (DFT) calculations of model compounds. DFT further reveals P(MCH+-alt-Cx) to be the thermodynamically most stable form. It is proposed that the para-linkage to the phenyl-based comonomer Cx decreases acidity of protonated merocyanine and hence increases stability of P(MCH+-alt-Cx), which poses a marked difference compared to the commonly employed 6-nitro-substituted analogs.

Treatment characteristics and statistical optimization of Chloroform using sonophotocatalysis

The experimental design and response surface methodology were applied to optimization of the sonophotocatalytic degradation of Chloroform. The sonophotocatalytic reactions were mathematically described as a function of parameters such as Chloroform concentration, UV intensity, and TiO2 concentration using the Box–Behnken method. Statistical analysis showed that the responses of Chloroform removal in sonophotocatalysis were fitted to linear interaction effect model. The response surface methodology using the Box–Behnken method yields the following equation as an uncoded unit: y=90.7017+5.3371(UV)-4.2315(Chloroform)-0.3550(TiO2)-0.8101(UV)(Chloroform)+0.1072(UV)(TiO2)+0.0574(Chloroform)(TiO2). As for main effect factors of the model formula, concentration of Chloroform posted the biggest effects followed by UV intensity and TiO2 concentration. The impact of various factors on removal rate was higher when Chloroform concentration was lower, TiO2 concentration was higher, and number of UV lamp was higher.

Autocatalytic cathodic dehalogenation triggered by dissociative electron transfer through a C–H⋯O hydrogen bond

A combined action of the C-H···Oalkoxide hydrogen bonding and Cl···πpyrazolyl dispersive interactions facilitates intramolecular electron transfer (ET) in the transient {Mo(I)(NO)(Tp(Me2))(Oalkoxide)}˙(-)···HCCl3 adduct ([Tp(Me2)](-) = κ(3)-hydrotris(3,5-dimethylpyrazol-1-yl)borate), setting off a radical autocatalytic process, eventually leading to chloroform degradation. In the voltammetric curve, this astonishingly fast process is seen as an almost vertical drop-down. The potential at which it occurs is favorably shifted by ca. 1 V in comparison with uncatalyzed reduction. As predicted by DFT calculations, crucial in the initial step is a close and prolonged contact between the electron donor (Mo(I) 4d-based SOMO) and acceptor (σ(*)(C-Cl)-based LUMO). This occurs owing to the exceptionally short (dH···O = 1.82 Å) and nearly linear C-H···Oalkoxide bonding, which is reflected by a large ΔνC-H red-shift of 380 cm(-1) and a noticeable reorganization of electronic density along the H-bond axis. The advantageous noncovalent interactions inside the cavity formed by two pyrazolyl (pz) rings are strengthened during the C-Cl bond elongation coupled with the ET, giving rise to possible transition state stabilization. After the initial period, the reaction proceeds as a series of consecutive alternating direct or Mo(II/I)-mediated electron and proton transfers. Alcohols inhibit the electrocatalysis by binding with the {Mo(I)-Oalkoxide}˙(-) active site, and olefins by trapping transient radicals. The proximity and stabilization effects, and competitive inhibition in the studied system may be viewed as analogous to those operating in enzymatic catalysis.

Microbial degradation of chloroform

Chloroform (CF) is largely produced by both anthropogenic and natural sources. It is detected in ground and surface water sources and it represents the most abundant halocarbon in the atmosphere. Microbial CF degradation occurs under both aerobic and anaerobic conditions. Apart from a few reports describing the utilization of CF as a terminal electron acceptor during growth, CF degradation was mainly reported as a cometabolic process. CF aerobic cometabolism is supported by growth on short-chain alkanes (i.e., methane, propane, butane, and hexane), aromatic hydrocarbons (i.e., toluene and phenol), and ammonia via the activity of monooxygenases (MOs) operatively divided into different families. The main factors affecting CF cometabolism are (1) the inhibition of CF degradation exerted by the growth substrate, (2) the need for reductant supply to maintain MO activity, and (3) the toxicity of CF degradation products. Under anaerobic conditions, CF degradation was mainly associated to the activity of methanogens, although some examples of CF-degrading sulfate-reducing, fermenting, and acetogenic bacteria are reported in the literature. Higher CF toxicity levels and lower degradation rates were shown by anaerobic systems in comparison to the aerobic ones. Applied physiological and genetic aspects of microbial cometabolism of CF will be presented along with bioremediation perspectives.

Large Carbon Isotope Fractionation during Biodegradation of Chloroform by Dehalobacter Cultures

Compound specific isotope analysis (CSIA) has been applied to monitor bioremediation of groundwater contaminants and provide insight into mechanisms of transformation of chlorinated ethanes. To date there is little information on its applicability for chlorinated methanes. Moreover, published enrichment factors (ε) observed during the biotic and abiotic degradation of chlorinated alkanes, such as carbon tetrachloride (CT); 1,1,1-trichloroethane (1,1,1-TCA); and 1,1-dichloroethane (1,1-DCA), range from -26.5‰ to -1.8‰ and illustrate a system where similar C-Cl bonds are cleaved but significantly different isotope enrichment factors are observed. In the current study, biotic degradation of chloroform (CF) to dichloromethane (DCM) was carried out by the Dehalobacter containing culture DHB-CF/MEL also shown to degrade 1,1,1-TCA and 1,1-DCA. The carbon isotope enrichment factor (ε) measured during biodegradation of CF was -27.5‰ ± 0.9‰, consistent with the theoretical maximum kinetic isotope effect for C-Cl bond cleavage. Unlike 1,1,1-TCA and 1,1-DCA, reductive dechlorination of CF by the Dehalobacter-containing culture shows no evidence of suppression of the intrinsic maximum kinetic isotope effect. Such a large fractionation effect, comparable to those published for cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC) suggests CSIA has significant potential to identify and monitor biodegradation of CF, as well as important implications for recent efforts to fingerprint natural versus anthropogenic sources of CF in soils and groundwater.

Chloroform aerobic cometabolism by butane-growing Rhodococcus aetherovorans BCP1 in continuous-flow biofilm reactors

This work focuses on chloroform (CF) cometabolism by a butane-grown aerobic pure culture (Rhodococcus aetherovorans BCP1) in continuous-flow biofilm reactors. The goals were to obtain preliminary information on the feasibility of CF biodegradation by BCP1 in biofilm reactors and to evaluate the applicability of the pulsed injection of growth substrate and oxygen to biofilm reactors. The attached-cell tests were initially conducted in a 0.165-L bioreactor and, then, scaled-up to a 1.772-L bioreactor. Glass cylinders were utilized as biofilm carriers. The continuous supply of growth substrate (butane), which led to the attainment of the highest CF degradation rate (8.4 mg(CF) day(-1) m (biofilm surface)(-2)), was compared with four schedules of butane and oxygen pulsed feeding. The pulsed injection technique allowed the attainment of a ratio of CF mass degraded per unit mass of butane supplied equal to 0.16 mg(CF) mg (butane)(-1), a value 4.4 times higher than that obtained with the continuous substrate supply. A procedure based on the utilization of integral mass balances and of average concentrations along the bioreactors resulted in a satisfactory match between the predicted and the experimental CF degradation performances, and can therefore be utilized to provide a guideline for optimizing the substrate pulsed injection schedule.

Application of the growth substrate pulsed feeding technique to a process of chloroform aerobic cometabolism in a continuous-flow sand-filled reactor

A process of chloroform (CF) aerobic cometabolic biodegradation by a butane-growing consortium was studied for 354days in a 2-m continuous-flow sand-filled reactor. The study was aimed at (a) investigating the oxygen/substrate pulsed injection as a tool to control the clogging of the porous medium, to attain a wide bioreactive zone and to reduce substrate inhibition on CF cometabolism; (b) developing a reliable model of CF cometabolism in porous media. While the continuous supply of butane rapidly led to the clogging of the porous medium due to excessive biomass growth, the testing of six types of oxygen/substrate pulsed feeding led to the identification of a feeding schedule capable to prevent aquifer clogging and to lead to the development of a long bioreactive zone and to satisfactory CF degradation performances. The tested model of aerobic cometabolism allowed a suitable interpretation of the experimental data as long as the ratio of CF degraded to butane consumed was ≤0.27mgCFmgbutane−1. A long-term 1-D simulation of the best-performing schedule of pulsed oxygen/substrate supply extended to a 30-m aquifer length resulted in a 20-m bioreactive zone and in a 96% CF removal.

Degradation of chloroform by immobilized cells of Bacillus sp. in calcium alginate beads

A Bacillus sp., capable of degrading chloroform, was immobilized in calcium alginate. The beads in 20g alginate l(-1) (about 2×10(8)cells/bead) could be re-used nine times for degradation of chloroform at 40μM. The immobilized cells had a higher range of tolerance (pH 6.5-9 and 20-41°C) than free cells (pH 7-8.5 and 28-32°C). At 5g alginate l(-1), leakage of the cells from the beads was 0.51mg dry wt ml(-1). This species is the first reported Bacillus that can degrade chloroform as the sole carbon source.

Enhancement of chloroform degradation by the combination of hydrodynamic and acoustic cavitation

The decomposition of chloroform by the combination of hydrodynamic and acoustic cavitation (Hydrodynamic–Acoustic-Cavitation/HAC) has been investigated. The flow rate and the hole diameter of the orifice plate remarkably affect the conversion of chloroform in the combined system. The conversion increases with increasing fluid velocity without any restriction. With a 2.8 mm orifice plate the conversion reaches an optimal value. A synergistic effect has been obtained by the hybrid method of acoustic and hydrodynamic cavitation. The total synergistic effect achieves 17% and 73% per pass, respectively. The analysis of the energy efficiencies shows different results. Due to high optimization potential, this hybrid method can be visualized as a new step for wastewater treatment.