Continuous trichloroethylene biodegradation by Pseudomonas putida F1 in a biofilm reactor and determination of an optimal feeding path via a response surface model

Abstract

Reactor design and feeding strategies are the key to successful trichloroethylene (TCE) treatment via cometabolism. An easy to maintain and operate laboratory scale packed-bed biofilm reactor, featuring recycled gas and liquid effluent streams, was developed for continuous aerobic aqueous-phase TCE biodegradation using Pseudomonas putida F1 as the biocatalyst and toluene as the primary substrate. The impacts of the influent toluene and TCE concentrations, flow rates, and recycle rates on TCE biodegradation were studied. Multivariate factors, including influent toluene and TCE concentrations, their interactions, and flow rates were further analyzed via a response surface model (RSM). Results showed that such bioreactor design eliminated oxygen limitation and removed or substantially reduced toluene competitive inhibition on TCE degradation. A TCE removal efficiency of >90% was achieved at an influent TCE concentration of ≤0.3 mg/L under an ˜8-min mean hydraulic retention time. Toluene and TCE concentrations, in both linear and quadratic forms, were the most significant factors for TCE degradation, indicating both cell regenerating and inhibiting effects from toluene and a toxic effect from TCE. This RSM analysis has successfully identified an optimal influent toluene concentration path for each influent TCE concentration and provided insight for an extended TCE degradation at higher TCE concentrations.