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This study has demonstrated the applicability of a simple technology such as the sequencing batch reactor (SBR), operated with suspended biomass, to the aerobic biodegradation of a highly toxic compound, the pentachlorophenol (PCP). An enrichment of a microbial consortium, originated from the biomass of an urban wastewater treatment plant, was performed and 70 days were sufficient to achieve removal efficiencies of ∼90% with the compound fed as only carbon and energy source Once completed the start-up period, the SBR was operated with the acclimatized biomass for 60 days at a feed concentration of PCP in the range of 10-20 mg L(-1). Improved performance was observed at increased influent concentration and the reached removal efficiency for the highest concentrations was stable at values≥90%. Kinetic and stoichiometric characterization of the acclimated biomass was performed with biodegradation tests carried out in the bioreactor during the reaction phase. The classical and a modified four-parameter forms of the Haldane equation were applied to model the substrate inhibited kinetics. Both models provided reliable predictions with high correlation coefficients (>0.99). The biomass characterization was completed with the evaluation of the growth yield coefficient, Y (0.075 on chemical oxygen demand base) and endogenous respiration rate, b (0.054 d(-1)). The aerobic SBR, operated in the metabolic mode with a mixed culture, showed superior performance in comparison to continuous systems applied in the same range of PCP influent loads and achieved removal rates are suitable for application.

This study verifies the potential applicability of horizontal-flow anaerobic immobilized biomass (HAIB) reactors to pentachlorophenol (PCP) dechlorination. Two bench-scale HAIB reactors (R1 and R2) were filled with cubic polyurethane foam matrices containing immobilized anaerobic sludge. The reactors were then continuously fed with synthetic wastewater consisting of PCP, glucose, acetic acid, and formic acid as co-substrates for PCP anaerobic degradation. Before being immobilized in polyurethane foam matrices, the biomass was exposed to wastewater containing PCP in reactors fed at a semi-continuous rate of 2.0 microg PCP g(-1) VS. The applied PCP loading rate was increased from 0.05 to 2.59 mg PCP l(-1)day(-1) for R1, and from 0.06 to 4.15 mg PCP l(-1)day(-1) for R2. The organic loading rates (OLR) were 1.1 and 1.7 kg COD m(-3)day(-1) at hydraulic retention times (HRT) of 24h for R1 and 18 h for R2. Under such conditions, chemical oxygen demand (COD) removal efficiencies of up to 98% were achieved in the HAIB reactors. Both reactors exhibited the ability to remove 97% of the loaded PCP. Dichlorophenol (DCP) was the primary chlorophenol detected in the effluent. The adsorption of PCP and metabolites formed during PCP degradation in the packed bed was negligible for PCP removal efficiency.

This study focuses on the use of non-viable Aspergillus niger biomass, for the biosorption of pentachlorophenol (PCP) from aqueous solutions. Various forms of the biomass-autoclaved and chemically conditioned, were tested for their potential in the removal of PCP from aqueous solutions. It was found that PCP removal was pH dependent; PCP removal decreased with the increase in pH for all type of biomass, except for cetyltrimethylammonium bromide (CTAB) biomass. For CTAB biomass, a near complete removal of PCP was observed at all pHs. Therefore, CTAB biomass was used in further studies. PCP removal was rapid, with an equilibrium time of 2h. The rate of adsorption kinetics was well described by a pseudo-second order model. Isotherm models of the type one and two parameter models were found to fit the isotherm data. PCP biosorption was found to be exothermic in nature; the amount of PCP sorbed decreased with an increase in temperature. Desorption was carried out using deionized water, dilute HCl and dilute NaOH, and it was found that most of the PCP was irreversibly bound to the biomass. The addition of inorganic salts did not affect the removal of PCP from aqueous solutions. Among the surface functional groups present on the biomass, carboxyl, amide and hydroxyl groups seem to have played a role in PCP biosorption. It was concluded that CTAB treated biomass was an excellent adsorbent for the removal of PCP from aqueous solutions.