Chlorinated phenols biodegradation

Baird et al. [40] utilized gas chromatography in his study of the biodegradability of chlorinated phenols in sewage sludge. 

Haggblom, M. M., Rivera, M. D. Young, L. Y. (1993). Influence of alternative electron acceptors on the anaerobic biodegradability of chlorinated phenols and benzoic acids. applied and Environmental Microbiology, 59, 1162-7. 

Smith, J. A. Novak, J. T. (1987). Biodegradation of chlorinated phenols in subsurface soil. Water, Air and Soil Pollution, 33, 29-42. 

Portier, R. J., and K. Fujisaki. 1986. Continuous biodegradation and detoxification of chlorinated phenols using immobilized bacteria. Toxic Assess. 7(4) 501-13. 

The chlorophenoxyalkanoic acids constitute yet another economically important group of halogenated aromatic hydrocarbons. They are widely used as herbicides to control dicotyledonous weeds. The most important of them are 2,4-D and its propionic and butyric acid homologs, 4-chloro> 2-methylphenoxyacetic acid (MCPA), and 2,4,5>trichlorophenoxyacetic add (2,4,5-T). In all the cases studied, aerobic biodegradation proceeds by removal of the aliphatic side chain with the formation of the corresponding chlorinated phenoL Thus, formation of 2,4 chlorophenol from both 2,4-D and 4-(2,4-dichlorophenoxy)-butyric acid, 4-chloro-o-cresol from MCPA, and 2,4,5-trichlorophenol from 2,4,5-T has been... 

The application of highly-chlorinated phenols is in rapid decline production is banned in a number of countries, due to their poor biodegradability and the possibility of producing dioxins and dibenzofurans in their manufacture. 

The BAT system operates based on principles of aerobic cometabolism. In cometabohsm, enzymes that the microbes produce in the process of consuming one particular compound (e.g., phenol) have the collateral effect of transforming another compound that normally resists biodegradation (e.g., chlorinated ethenes, especially lesser chlorinated ethenes such as dichloroethene or vinyl chloride). The BAT system operates under these principles by sorbing the chlorinated compounds from a vapor stream onto powdered activated carbon (PAC) where they are cometabolically transformed into a combination of end products, including new biomass, carbon dioxide, inorganic salts, and various acids. 

Bioremediation and thermal desorption are the most frequently selected innovative technologies for NPL sites with SVOCs, which are the second most common contaminants found at NPL sites. Also, SVE has been selected for some of the most volatile SVOCs (e.g., phenols and naphthalenes). Current research efforts are focused on biodegradation of chlorinated aliphatic hydrocarbons, such as trichloroethylene (TCE) and vinyl chloride, which occur at many sites. Thermal desorption most effectively treats PAHs and PCBs, and it may be particularly useful to pretreat organics prior to metal treatment. 

Fem complexes were reported as effective photocatalysts for oxidation of many different organic pollutants, eg alcohols and their derivatives [20,29] organic acids, such as formic [50,53,56], oxalic [37], citric [57], and maleic [58] EDTA [11,20-23], phenol and its derivatives [35, 36, 45,59,60], other aromatic pollutants [38,43,51, 61-64], non-biodegradable azo dyes [40, 41, 48, 55, 59, 65], herbicides [54, 66-70], pesticides [32, 46, 71, 72], insecticides [44], pharmaceuticals and wastewater from medical laboratories [39,47,73], chlorinated solvents [33,74], municipal wastewater [75], and many others [20], The photo-Fenton process was explored as photochemical pre-treatment to improve its biodegradability, especially of biorecalcitrant wastewater from the textile industry [76, 77] the method was also proposed for water disinfection [78,79],... 

The feasibility of applying solar radiation as a source of UV-visible radiation has made the photo-Fenton system an economical and competitive process. Within this context an alternative method has been developed based on solar photocatalytic oxidation and natural processes of wastewater treatment [5], as well as sunlight-driven degradations of many compounds, such as EDTA [30], phenols [7,13], pesticides [31-33], surfactants [34], diclofenac [24], formic acid [22], azo-dyes [19], non-biodegradable chlorinated solvents [35], nitroaniline [16], and other organic compounds [21, 36]. 

Phenols of enviromnental interest are derived from a wide variety of industrial sources, or present as biodegradation products of humic substances, tannins, and lignins, and as degradation products of many chlorinated phenoxyacid herbicides and organophosphorous pesticides. Phenols, especially chlorophenols, are persistent, and toxic at a few pg/1. Therefore, phenols are hsted at the US-EPA hst of priority pollutants and the EU Directive 76/464/EEC as dangerous substances. The samples to be analysed can be surface waters or industrial effluents. 

Important classes of nonionic surfactants are aliphatic poly-ethoxylate alcohols (AEO), and octyl or nonyl phenol polyethoxylates (OPEO and NPEO). The alkylphenol ethoxylates (APEO) attracted special attention due to their supposedly endocrine disrupting properties (Ch. 8.3). LC-MS analysis may also involve nonylphenolethoxycarboxylates (NPEC), biodegradation products of NPEO, and halogenated analogues, generated in chlorine disinfection treatments in drinking water production plants. 

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