Pentachlorophenol biodegradation in a two-phase system operated with absorptive polymer: Box-Behnken experimental design and optimization by response surface methodology

The biodegradation of pentachlorophenol (PCP), the most toxic among chlorophenols, was extensivelyinvestigated in solid-liquid two-phase bioreactors (according to Box-Behnken experimental design) todemonstrate the feasibility of this technological platform. Process performance optimization for the sub-sequent scale up was also performed. The process was catalysed by an acclimated microbial consortiumand the partitioning phase consisted of Hytrel 8206 polymer. The virtuous combination of polymeruptake/release and microbial biodegradation allowed achieving practically complete biodegradationefficiencies and rates in the range of 4.0-7.8 mg/(L h) for PCP concentrations up to 100 mg/L far abovethose previously tested. Detected biodegradation rates are one order of magnitude higher than the onesreported for suspended biomass reactors. A regression model based on 3 independent variables (initialPCP and biomass concentration and polymer-to-water ratio) was formulated to predict the volumetricbiodegradation rate. The significance of independent variables and their interactions was tested by theanalysis of variance (ANOVA) with 95% confidence limit. The model resulted adequate and the polymer-to-water ratio was identified as the most significant factor affecting the system response. Maximizationof the biodegradation rate has been achieved for PCP concentration of 100 mg/L, biomass concentrationof 1 gVSS/L and polymer-to-water ratio of 9%.