Variety Of Organic Pollutants Research Articles

The treatment of petrochemical wastewater via ozone-persulfate coupled catalytic oxidation: mechanism of removal of soluble organic matter.

Petrochemical wastewater contains a variety of organic pollutants. Advanced oxidation processes (AOPs) are used for deep petrochemical wastewater treatment with distinct advantages, including the complete mineralization of organic substances, minimal residual byproducts, and compatibility with biological treatment systems. This work evaluates the effectiveness of three methods, namely, ozone, persulfate, and O3-PMS (ozone-persulfate) processes, which were compared to remove soluble organic matter. The O3-PMS process offered significant advantages in terms of organic matter removal efficiency. This process involves ozone dissolution in an aqueous persulfate solution, producing a more significant amount of hydroxyl radicals in comparison to single AOPs. The production of hydroxyl radicals and the synergistic effect of hydroxyl radicals and persulfate radicals were investigated. In the O3-PMS process, transition metal ions were added to understand the mechanism of the O3-PMS coupled catalytic oxidation system. The results showed that when the ozone concentration was in the range of 5 ~ 25mg/L, the dosage of persulfate was in the range of 0.01 ~ 0.05mol/L, the dosage of metal compounds was in the range of 0:0 ~ 2:1, and the reaction time was in the range of 0 ~ 2h; the optimum chemical oxygen demand (CODCr) and total organic content (TOC) removal effect was achieved under the coupled system with an ozone concentration of 10mg/L, a persulfate dosage of 0.02mol/L, a 1:2 dosage ratio of between Fe2+ and Cu2+ compounds, and a reaction time of 2h. Under optimal reaction conditions, the rates of CODCr and TOC removal reached 70% and 79.3%, respectively. Furthermore, the removal kinetics of the O3-PMS coupled catalytic oxidation system was analyzed to optimize the removal conditions of COD and TOC, and the mechanism regulating the degradation of dissolved organic matter was explored by three-dimensional fluorescence and GC-MS technology. Thus, O3-PMS coupled catalytic oxidation is an effective process for the deep treatment of wastewater. The careful selection of transition metal ions serves as a theoretical foundation for the subsequent preparation of catalysts for the ozone persulfate oxidation system, and this study provides a suitable reference for removing organic matter from petrochemical wastewater.

Bioremediation of Organic Pollutants in Soil-Water System: A Review.

Soil-water pollution is of serious concern worldwide. There is a public outcry against the continually rising problems of pollution to ensure the safest and healthiest subsurface environment for living beings. A variety of organic pollutants causes serious soil-water pollution, toxicity and, therefore, the removal of a wide range of organic pollutants from contaminated matrix through the biological process rather than physico-chemical methods is an urgent need to protect the environment and public health. Being an ecofriendly technology, bioremediation can solve the problems of soil-water pollution due to hydrocarbons as it is a low-cost and self-driven process that utilises microorganisms and plants or their enzymes to degrade and detoxify pollutants and thus, promote sustainable development. This paper describes the updates on the bioremediation and phytoremediation techniques which have been recently developed and demonstrated at the plot-scale. Further, this paper provides details of wetland-based treatment of BTEX contaminated soils and water. The knowledge acquired in our study contributes extensively towards understanding the impact of dynamic subsurface conditions on engineered bioremediation techniques.

2D/2D BiOIO3/Ti3C2 MXene nanocomposite with efficient charge separation for degradation of multiple pollutants

Co-catalysts can achieve efficient separation of photogenerated carriers and are considered as a promising strategy for solar photocatalytic removal of pollutants. Herein, we reported the synthesis of nanocomposite of BiOIO3/Ti3C2 MXene combining two dimensional 2D BiOIO3 with 2D Ti3C2 MXene co-catalyst. The few-layered 2D Ti3C2 MXene provided more adsorption and reaction sites. Furthermore, the synergism of intimate interfacial contact between the two 2D nanosheets and robust metallic electrical conductivity of Ti3C2 MXene significantly accelerated the separation and migration of photogenerated charge carriers. A variety of organic pollutants were proved to be effectively degraded by 2D/2D BiOIO3/Ti3C2 MXene composites. The degradation efficiencies followed the order tetracycline hydrochloride (93.4 %) > diclofenac sodium (87.6 %) > levofloxacin hydrochloride (77.4 %) > 4-nitrophenol (43.3%). Besides, the satisfactory recycling and stability of BiOIO3/Ti3C2 MXene for the degradation of organic pollutants in water under solar irradiation predicted its good prospect for practical applications.

Hydrogen peroxide-assisted and histidine-stabilized copper-containing nanozyme for efficient degradation of various organic dyes

Nanozymes have potential applications in many fields, and a novel copper-containing nanozyme with highly dispersity and uniformity was self-assembled for efficient degradation of various organic dyes in this work. In the nanozyme, histidine was used to coordinate with copper ions, and hydrogen peroxide was prone to Fenton-like reaction to generate hydroxylated copper oxide intermediates. The nanozyme showed good peroxidase-like activity, and also had the ability to catalyze the degradation of various organic dyes efficiently with good storage and recycling ability. Furthermore, the degradation kinetics and mechanism of nanozyme had been further studied, and found that hydroxyl radical and singlet oxygen play vital roles in the catalytic degradation process. Meanwhile, this nanozyme can efficiently degrade two organic compounds at the same time, and this system is capable of dealing with complex practical application scenarios where wastewater contains a variety of organic pollutants.

Bifunctional Ni@NiO catalyst supported on loofah sponge-derived carbon for electrocatalytic air oxidation of biorefractory pollutant in a coupling system.

Oxygen (O2) in the air is a green oxidant, and utilization of air for pollutant removal is highly desired. Herein, we report the preparation and utilization of a novel biomass-based three-dimensional (3D) Ni@NiO/carbon composite for the electro-activation of O2 under room condition. The carbon-coated Ni@NiO nanoparticles are fabricated on a hierarchical 3D porous loofah sponge-derived carbon (LSC) support as the bifunctional catalyst for the activation of O2 via both the electro-oxidation and electro-reduction reactions. An electrocatalytic air oxidation coupling system is constructed with the Ni@NiO/LSC shell-core electrodes for pollutant degradation. A variety of organic pollutants, including pharmaceutics and personal care products (PPCPs), dyes, phenolic compounds, and real waters are mineralized by more than 60% with significantly enhanced biodegradability. Notably, the coupling system obtains high mineralization efficiency of 70.2 ± 1.9% on landfill leachate with significant biodegradability enhancement. The specific energy consumptions of the coupling system are only 6.8 ± 0.7 to 60.2 ± 3.6 kWh kg-TOC-1 in mineralizing different pollutants. The hollow structure of the LSC fibers endows the loaded Ni@NiO with superior intrinsic catalytic activity, which is associated with low reaction resistance and facile electron transfer. The Ni@NiO on LSC presents an electrocatalytic wet air oxidation (ECWAO) catalytic activity higher by 35.8% and cathodic air oxidation (CAO) catalytic activity higher by 22.7% as compared to that loaded on commercial graphite felt.

Polyamide 6.6 Degradation through Photo-Fenton Process

Synthetic polymers have become essential in our life, nevertheless, the high production and the low recycling around the world have caused serious problems of contamination in soil and water. In addition, its fragmentation into microplastics in environmental conditions has exacerbated the ecological problems due to its possible ingestion by organisms and its high capacity to transport and release a wide variety of organic pollutants. Photo-Fenton process was used to evaluated its capacity to degrade PA6.6 microplastic under simulated solar irradiation and natural solar irradiation plus LED visible light in order to get a best knowledge about its behavior in environmental conditions. PA6.6 was degraded for 7 h through photo-Fenton process under simulated solar irradiation. Superficial defects were observed along the PA6.6 microplastic after degradation experiments. However, FT-IR analysis did not show the formation of additional bands which indicated the formation of new products. DSC analysis showed changes in the melting point of the PA6.6 after the photo-Fenton treatment at different times. The assays carried out under natural solar irradiation showed lower degradation of the PA6.6 under the same experimental conditions, nevertheless, it was observed an increase of the specific surface area 90 times higher in the PA6.6 treated for 10 h.

Enhancement of Fenton Performance at Near-Neutral pH by Using Ethylene Diamine Tetra Acetic Acid for Anionic Surfactant Removal from a Laundry Wastewater

Fenton process involving Fe2+ ions and H2O2 produces OH radicals, that act as a strong oxidizing agent for degradation of a variety of organic pollutants. However the process is poor performance at neutral pH limiting its application for industrial wastewater treatment. The short coming problem, in the current study, is solved by introducing ethylene diamine tetra acetic acid (EDTA) as a complexing compound. The degradation was conducted through batch experiment, by varying EDTA concentration and pH. In addition, the Fe2+ and H2O2 concentrations, and the reaction time were optimized. The research results assign that the addition of EDTA could remarkably enhance the degradation of anionic surfactant, that was 96% at pH 6-8. The increase of the degradation was proportional to the concentrations of EDTA and 6 mg/L showed the optimum level. The highest degradation of 162 mg/L anionic surfactant in 20 mL of the laundry wastewater could be achieved within 30 mins by using Fe2+ 10 mM, H2O2 50 mM, and in the pre12sence of EDTA 6 mg/L at pH 7. Key words : Fenton, EDTA, degradation, surfactant, wastewater

Adsorption Properties and Host-guest Effects of Porous Cyclodextrin Polymers for Dye Molecules in Water

Cyclodextrin can form host-guest inclusion complexes with a variety of organic pollutants and has unique advantages in removing complex dye molecules from water. In this study, a porous cyclodextrin polymer (P-CDP) was prepared using a rigid crosslinking agent, and the structure of the P-CDP was characterized by FT-IR, XPS, SEM, BET, and other technologies. The P-CDP was studied using isothermal adsorption and kinetic adsorption experiments. The inclusion adsorption performance and host-guest effect of the P-CDP for dye molecules in water were studied using competitive experiments. The characterization results showed that the P-CDP had strong thermal stability. It had a microporous structure with a specific surface area of 108.745 m2·g-1. The Langmuir model and the pseudo-second-order kinetic model had a higher fitting degree for the adsorption process. The results of the competition experiments showed that the electrostatic effect was stronger than the host-guest effect in the adsorption process. Pollutants whose molecular configurations were highly matched with the cyclodextrin cavity could form inclusion complexes with high molecular stability. Contaminants with strong hydrophobicity were more likely to be encapsulated in the cyclodextrin cavity. After the P-CDP adsorbed the dyes, the removal efficiency after the fifth cycle of elution and regeneration remained above 80%. This study showed that P-CDP has potential application value in the treatment of dye wastewater.

Assessing the endocrine disrupting potentials and genotoxicity in environmental samples from Taiwanese rivers

BackgroundSurface waters receive a variety of organic pollutants via wastewater discharge, and sediment represents a sink for hydrophobic contaminants. In this study, we used in vitro yeast-based reporter gene assays and a Bacillus subtilis Rec-assay to examine the occurrence of endocrine disrupting activities and genotoxic potentials in samples collected from three Taiwanese rivers. Levels of 51 polycyclic aromatic hydrocarbons (PAHs) in muscles of fish captured from same rivers were also analyzed to assess in vivo pollution of PAHs.ResultsAntagonist activities for androgen receptor and retinoid X receptor (RXR) were detected in river water extracts at environmentally relevant concentrations., and sediment extracts exhibited RXR agonist, RXR antagonist, and genotoxic potentials concurrently. Σ16 PAHs in fish muscles ranged from 44.9–242.4 ng g− 1 dry weight, representing 38 to 59% of the total 51 PAHs concentrations, and methylated PAHs of low molecular weight PAHs were often detected as well.ConclusionTaiwanese river sediment samples concomitantly exhibited RXR disrupting potentials and genotoxic activities, whereas RXR agonist and antagonist activities were simultaneously detected in several dry-season sediment extracts. PAH levels in fish muscles were categorized as minimally polluted by aromatic compounds, nonetheless, the presence of methylated PAHs in muscles samples may be of concern owing to the higher toxic potentials than their parent compounds.

Spatial Distribution and Congener Profiles of Polybrominated Diphenyl Ethers in Surface Sediment from Sanmen Bay and Xiamen Bay, Southeast China.

Coastal areas are influenced by anthropogenic input of a variety of organic pollutants, among which polybrominated diphenyl ethers (PBDEs) represent an important group. In the present study, we investigated the contamination status of PBDEs in surface sediment from two economically important Bays in Southeast China, Sanmen Bay (SMB; n = 29) and Xiamen Bay (XMB; n = 10). Concentrations of ∑PBDEs ranged from 2.2 to 78.5ng/g dw (median 5.7ng/g dw) in SMB and 7.9-276.0ng/g dw (median 43.5ng/g dw) in XMB, respectively. A nearshore-offshore decreasing trend was observed for both ∑PBDEs and BDE-209 concentrations, indicating strong urban influences. Although the current levels would not produce any significant impact on benthos and aquatic ecosystems of the studied regions, continuous monitoring is needed to understand the temporal trends of contamination in the important coastal waters and whether sediment-associated PBDEs constitute a potential source to aquatic ecosystems.

LaoABCR, a Novel System for Oxidation of Long-Chain Alcohols Derived from SDS and Alkane Degradation in Pseudomonas aeruginosa.

The opportunistic pathogen Pseudomonas aeruginosa strain PAO1 is able to use a variety of organic pollutants as growth substrates, including the anionic detergent sodium dodecyl sulfate (SDS) and long-chain alkanes. While the enzymes initiating SDS and alkane degradation are well known, the subsequent enzymatic steps for degradation of the derived primary long-chain alcohols have not yet been identified. By evaluating genes specifically induced during growth with SDS, a gene cluster encoding a putative alcohol dehydrogenase (PA0364/LaoA), a probable inner membrane protein (PA0365/LaoB), and a presumable aldehyde dehydrogenase (PA0366/LaoC) was identified and designated the Lao (long-chain-alcohol/aldehyde-oxidation) system. Growth experiments with deletion mutants with SDS, 1-dodecanol, and alkanes revealed that LaoA and LaoB are involved in the degradation of primary long-chain alcohols. Moreover, detection of 1-dodecanol oxidation in cell extracts by activity staining revealed an interdependency of LaoA and LaoB for efficient 1-dodecanol oxidation. An in silico analysis yielded no well-characterized homologue proteins for LaoA and LaoB. Furthermore, a gene adjacent to the lao gene cluster encodes a putative transcriptional regulator (PA0367/LaoR). A laoR deletion mutant exhibited constitutive expression of LaoA and LaoB, indicating that LaoR is a repressor for the expression of laoABC Taken together, these results showed that the proteins LaoA and LaoB constitute a novel oxidation system for long-chain alcohols derived from pollutants.IMPORTANCE The versatile and highly adaptive bacterium Pseudomonas aeruginosa is able to colonize a variety of habitats, including anthropogenic environments, where it is often challenged with toxic compounds. Its ability to degrade such compounds and to use them as growth substrates can significantly enhance spreading of this opportunistic pathogen in hygienic settings, such as clinics or water distribution systems. Thus, knowledge about the metabolism of P. aeruginosa can contribute to novel approaches for preventing its growth and reducing nosocomial infections. As the Lao system is important for the degradation of two different classes of pollutants, the identification of these novel enzymes can be a useful contribution for developing effective antibacterial strategies.

COP-compost: a software to study the degradation of organic pollutants in composts

Composting has been demonstrated to be effective in degrading organic pollutants (OP) whose behaviour depends on the composting conditions, the microbial populations activated and interactions with organic matters. The fate of OP during composting involves complex mechanisms and models can be helpful tools for educational and scientific purposes, as well as for industrialists who want to optimise the composting process for OP elimination. A COP-Compost model, which couples an organic carbon (OC) module and an organic pollutant (OP) module and which simulates the changes of organic matter, organic pollutants and the microbial activities during the composting process, has been proposed and calibrated for a first set of OP in a previous study. The objectives of the present work were (1) to introduce the COP-Compost model from its convenient interface to a potential panel of users, (2) to show the variety of OP that could be simulated, including the possibility of choosing between degradation through co-metabolism or specific metabolism and (3) to show the effect of the initial characteristics of organic matter quality and its microbial biomass on the simulated results of the OP dynamic. In the model, we assumed that the pollutants can be adsorbed on organic matter according to the biochemical quality of the OC and that the microorganisms can degrade the pollutants at the same time as they degrade OC (by co-metabolism). A composting experiment describing two different (14)C-labelled organic pollutants, simazine and pyrene, were chosen from the literature because the four OP fractions simulated in the model were measured during the study (the mineralised, soluble, sorbed and non-extractable fractions). Except for the mineralised fraction of simazine, a good agreement was achieved between the simulated and experimental results describing the evolution of the different organic fractions. For simazine, a specific biomass had to be added. To assess the relative importance of organic matter dynamics on the organic pollutants' behaviour, a sensitivity analysis was conducted. The sensitivity analysis demonstrated that the parameters associated with organic matter dynamics and its initial microbial biomass greatly influenced the evolution of all the OP fractions, although the initial biochemical quality of the OC did not have a significant impact on the OP evolution.

Novel integrated reactor for evaluation of activity of supported photocatalytic thin films: Case of methylene blue degradation on TiO 2 and nickel modified TiO 2 under UV and visible light

In this paper we present an integrated batch reactor for testing of the activity of photocatalysts supported in the form of thin films. The reactor vessel is a custom-built glass cuvette containing the catalyst sample and the solution of a model organic pollutant. The irradiation is provided by a tubular UV lamp or a white LED array fitted to the cuvette lid, while the solution is constantly stirred to minimize external mass-transfer effects. The concentration of contaminant is followed in situ by an integrated photometric system using a low-power laser to match the absorption spectra of model dyes such as methylene blue, reactive black and malachite green. In the current research, the reactor is used to determine the effect of incident radiation on the apparent rate constants of degradation of an organic dye (methylene blue) via thin films of titanium dioxide (Degussa P25) and nickel-modified TiO 2. The catalyst performance under various UV and visible light illuminations was estimated using the novel reactor system in just 1 h of experimental time: 30 min of dark adsorption of the dye and 30 min of irradiation. The reactor is suitable for fast screening of the reaction rate of processes utilizing not only titanium dioxide, but also other common photocatalysts and a variety of organic pollutants.

Coalescence/Filtration of an Oil-In-Water Emulsion in a Granular Organo-Clay/Anthracite Mixture Bed

Bentonite organo-clay has been used as a sorbent in removing awide variety of organic pollutants including oil in the past. Thepercentage oil removal by this sorbent has been reported to be inthe range of 65 to 100. However, breakdown (filtration, coalescence) mechanisms involved in a granular organo-clay/anthracite mixture bed treating an oil-in-water emulsion have not been understood so far. The purpose of thisresearch was to evaluate the applicabilities of the well-knownCarman-Kozeny filtration equation and Sherony and Kintner coalescence model to a 1000 mm organo-clay/anthracite bed treating a standard mineral oil-in-water emulsion using six different flow rates (12, 16, 20, 24, 28 and 32 mL min-1). The analysis of the experimental data showed that the Carman-Kozeny constant values were 4.29 and 5.54 for single-phaseand two-phase flows, respectively. In addition, the values of the specific permeability coefficients for single-phase and two-phase flows were found to be 2.7 × 10-8 m2and 1.4 × 10-8 m2, respectively, which showed 48.1% reduction in the case of two-phase flow. The shape factorvalue was found to be 1.0 for the mixture. The results also showed that the head-loss across the organo-clay/anthracite filter can be well predicted using the Carman-Kozeny filtrationequation for single-phase flow. In two-phase flow, the Carman-Kozeny model may not yield accurate predictions at highflow rates. The coalescence efficiency within the bed increasedas flow rate increased and decreased as the bed depth increased. The coalescence efficiency ranged from 4.4 to 17.5% in theorgano-clay/anthracite bed. Overall, the study indicated possiblesimultaneous occurrence of filtration and coalescence of the oil-in-water emulsion used in the organo-clay/anthracite filter.

Characterization of organic pollutants in industrial effluents using liquid chromatography–atmospheric pressure chemical ionization–mass spectrometry

Contaminated industrial effluents often contain a variety of organic pollutants which are difficult to analyse by standard GC–MS methods since this technique often misses the more polar or non-volatile fraction of these organic compounds. In the present work a method for the characterization of complex mixtures of organic contaminants present in various industrial effluents is proposed. The protocol consists of setting-up a methodology based on solid phase extraction (SPE) using an Automated Sample Preparation with Extraction Columns system (ASPEC XL) and Lichrolut EN sorbent material for preconcentrating 300–500 ml of water volumes spiked with a variety of pollutants: phenolic compounds, benzophenone, isothiocyanate-cyclohexane, ethylbenzoate, 1-methyl-2-pyrrolidinone, 2-methylbenzenesulphonamide, benzidines, acridine, 1,1,3,3-tetramethyl-2-thiourea, 2,2-dimethyl-1,3-propanediol, phosphates, phthalates and non-ionic detergents characterized by LC–MS using atmospheric pressure chemical ionization in the positive and negative ion modes. The developed protocol permitted unequivocal identification of target analytes such as pentachlorophenol, tributyl phosphate, 4-nonylphenol, dibutylphthalate, dimethylphthalate, bis(2-ethylhexyl)phthalate, isothiocyanate-cyclohexane, ethylbenzoate, 2-methylbenzene-sulphonamide, tetramethyl-thiourea, 2,2-dimethyl-1,3-propanediol and 1-methyl-2-pyrrolidinone at concentration levels varying from 0.16 to 54.4 μg l-1. © 1997 John Wiley & Sons, Ltd.

Characterization of organic pollutants in industrial effluents using liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry

Contaminated industrial effluents often contain a variety of organic pollutants which are difficult to analyse by standard GC–MS methods since this technique often misses the more polar or non-volatile fraction of these organic compounds. In the present work a method for the characterization of complex mixtures of organic contaminants present in various industrial effluents is proposed. The protocol consists of setting-up a methodology based on solid phase extraction (SPE) using an Automated Sample Preparation with Extraction Columns system (ASPEC XL) and Lichrolut EN sorbent material for preconcentrating 300–500 ml of water volumes spiked with a variety of pollutants: phenolic compounds, benzophenone, isothiocyanate-cyclohexane, ethylbenzoate, 1-methyl-2-pyrrolidinone, 2-methylbenzenesulphonamide, benzidines, acridine, 1,1,3,3-tetramethyl-2-thiourea, 2,2-dimethyl-1,3-propanediol, phosphates, phthalates and non-ionic detergents characterized by LC–MS using atmospheric pressure chemical ionization in the positive and negative ion modes. The developed protocol permitted unequivocal identification of target analytes such as pentachlorophenol, tributyl phosphate, 4-nonylphenol, dibutylphthalate, dimethylphthalate, bis(2-ethylhexyl)phthalate, isothiocyanate-cyclohexane, ethylbenzoate, 2-methylbenzene-sulphonamide, tetramethyl-thiourea, 2,2-dimethyl-1,3-propanediol and 1-methyl-2-pyrrolidinone at concentration levels varying from 0.16 to 54.4 μg l-1. © 1997 John Wiley & Sons, Ltd.

Analysis of industrial effluents to determine endocrine-disrupting chemicals

Contaminated industrial effluents often contain a variety of organic pollutants that can disturb the development of the endocrine system and the organs that respond to endocrine signals in organisms. Total characterisation of the effluents to detect all these potential endocrine disruptors by standard GC-MS methods is difficult since this technique often misses the more polar or non-volatile fraction of these organic compounds. The wide spectrum of endocrine-toxic substances and their low concentrations require powerful analytical approaches like LC-MS for their identification. Furthermore, the methods for the detection of endocrine effects developed up to now do not show all the possible oestrogenic effects and results of the different tests are not comparable to one another. Therefore, further ecotoxicological research should be carried out so that new strategies can be proposed. In this article, an overview of the analytical methods for determining organic contaminants in industrial effluents and tests for the identification of endocrine disruptors and their effects is presented.

Inhibition of fertilization in the sea urchinParechinus angulosusby organic pollutants: correlation with molecular valence connectivity indices

The percentage fertilization of eggs of the urchin Parechinus angulosus (Leske), following exposure of the sperm to a variety of organic pollutants, was used to test the possibility of predicting toxicities from a consideration of molecular structure. A correlation is demonstrated between concentrations resulting in 50-per-cent inhibition of fertilization (EC 50 or FID 50) and the zero, first-order and second-order molecular-valence connectivity indices of the substances concerned. This correlation is more marked when a series of alcohols rather than a variety of non-alcoholic substances is used. A log or power expression best describes the relationship.

Effects of organic pollutants on methanogenesis, sulfate reduction and carbon dioxide evolution in salt marsh sediments

Anaerobic salt marsh sediments were amended with a variety of organic pollutants and the effects on methanogenesis, sulfate reduction and carbon dioxide evolution were examined. Addition of 1000 μg g −1 (dry weight sediment) Arochlor 1221, lindane, endrin, benzene and phenanthrene resulted in no significant effects on the activities studied. Methanogenesis was inhibited by 1000 μg g −1toxaphene, PCP, chlordane, naphthalene, DDT, Kepone and heptachlor and by 100 μg g −1 PCP and toxaphene. At 1000 μg g −1 naphthalene and toxaphene and 100 μg g −1 PCP, a period of initial inhibition of methanogenesis was followed by stimulation relative to controls. Arochlor 1254 (1000 μg g −1) and Temik (500 and 10 μg g −1) stimulated methanogenesis from the outset. Temik at 500 μg g −1 gave the greatest stimulation of methanogenesis (900% of controls) of any of the compounds studied. Sulfate reduction was inhibited by 1000 μg g −1 PCP, toxaphene, naphthalene and chlordane and by 500 μg g −1 atrazine and 100 μg g −1 heptachlor. Sustained inhibition of sulfate reduction by naphthalene, toxaphene and PCP may have contributed to the stimulation of methanogenesis. Carbon dioxide evolution was not significantly affected by most of the compounds studied except for 100 μg g −1 PCP and 1000 μg g −1 aphthalene, each of which gave significant inhibition in only one of three experiments. Concentrations of individual organic pollutants required to cause observable effects were high. It is concluded that, except for highly polluted sediments, methanogenesis, sulfate reduction and CO 2 evolution would not be affected by the compounds studied here at concentrations typically found in the environment.