Photolytic degradation of chlorophenols from industrial wastewaters by organic oxidants peroxy acetic acid, para nitro benzoic acid and methyl ethyl ketone peroxide: identification of reaction products.
In this investigation, chlorophenol (CP) containing industrial wastewater was remediated by ultraviolet irradiation in conjunction with organic oxidants, peroxy acetic acid (PAA); para nitro benzoic acid (PNBA); and methyl ethyl ketone peroxide (MEKP). CP mineralization was studied with regard to chemical oxygen demand (COD) and chloride ion release under identical test conditions. COD depletion to the extent of 81% by PAA, 66% by PNBA, and 67% by MEKP was noted along with an upwardly mobile trend of chloride ion release upon irradiation of samples at 254 nm. A 90-99% decrease in CP concentration (as per high pressure liquid chromatography (HPLC) analysis) was achieved with an additional 15.0 ml of organic oxidant in all cases. Gas chromatography high resolution mass spectroscopy (GC-HRMS) results also indicated the formation of such reaction products as are free from chlorine substitutions. This treatment also leads to total decolorization of the collected samples.
UV/Methyl Ethyl Ketone Peroxide Mediated Chlorophenol Congener Degradation in Basic Media
The ubiquitous presence of chlorophenols (CPs) continues to be a cause of concern, owing to their recalcitrant nature. In this context, the present work investigated the degradation of model compounds, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol, by an organic oxidant, methyl ethyl ketone peroxide (MEKP) coupled with ultraviolet irradiation in basic media. Chemical analysis was followed by high-performance liquid chromatography and gas chromatography–mass spectrometry. Despite exhibiting varied patterns of decline, chemical oxygen demand was eventually noted to decrease to the extent of up to 70 %. Simultaneous increase/decrease in the release of chloride ions and decrease in pH indicated that parallel reactions were occurring, which led to the formation of acidic reaction products. First-order dynamics was approximated for all CP congener degradation. The degraded compounds showed absolutely no presence of chlorine atoms, which was a noteworthy feature testifying to the fact that MEKP action was capable of detoxification of CP congeners.
Characterization of the microorganisms from an acclimated activated sludge degrading phenolic compounds
The microorganisms responsible for the degradation of a mixture of phenol, 4-chlorophenol (4CP), 2,4-dichlorophenol (24DCP) and 2,4,6-trichlorophenol (246TCP) were isolated and characterized in terms of its degradation rate. Activated sludge was acclimated for 70 days to 40 mg phenols/l. After this period the microorganisms responsible for the chlorinated phenol degradation were isolated and identified. Four types of Gram negative bacteria ( Aeromonas sp., Pseudomonas sp. Flavimonas oryzihabitans , and Chryseomonas luteola ) and Mycobacterium sp. were identified. The degradation kinetics of each phenol by Aeromonas sp., Pseudomonas sp. Flavimonas oryzihabitans, Chryseomonas luteola and activated sludge were determined. The degradation of phenolic compounds was sequential: phenol and 4CP were first degraded, following by 24DCP and then by 246TCP. The acclimated activated sludge was from one to two orders of magnitude faster than the pure strains, when uptake rates were calculated in terms of the viable biomass (CFU). The qx for acclimated activated sludge varied between 8.2 and 15.8 × 10 −7 mg/CFU-d (407–784 mg/gVSS-d). Aeromonas sp. presented the highest qx of the pure strains, based on a VSS basis (33–57 mg/gVSS-d) but, in terms of viable biomass (5.0–15.6 × 10 −8 mg/CFU-d) Pseudomonas sp. did. Specific substrate uptake rate was 1.8 mg chlorinated phenols/g VSS-d for non-acclimated activated sludge.