Two-phase biodegradation of phenol in trioctylphosphine oxide impregnated hollow fiber membrane bioreactor

• Trioctylphosphine oxide (TOPO) was impregnated in polypropylene membranes.
• TOPO-containing membranes acted as partitioning phase in two-phase biodegradation.
• 800–3000 mg/L phenol was biodegraded at high cell growth and biodegradation rates.
• Two-phase biodegradation was not limited by interphasic mass transfer of phenol.
• The bioreactor exhibited stability over 400 h of operation.

A hollow fiber membrane bioreactor using trioctylphosphine oxide (TOPO) impregnated in polypropylene hollow fiber membranes was developed for two-phase biodegradation of phenol using Pseudomonas putida ATCC 11172. Scanning electron microscopy revealed white deposits of TOPO impregnated non-uniformly within the cross sections and surfaces of the membranes. The extractant impregnated membranes exhibited high adsorption capacity and rates, whereas biodegradation of 800–2500 mg/L phenol at 200 mL volume in the extractant impregnated hollow fiber membrane bioreactor (EIHFMB) was characterized by high cell growth and biodegradation rates. For example, 1000 mg/L phenol was completely degraded within 12 h at a specific growth rate of 0.73 h−1 while the biomass yield and average biodegradation rate were 0.31 g/g and 86 mg/L h, respectively. The biodegradation capacity and rate in the EIHFMB were improved by increasing the effective length of the fibers by 50%, as demonstrated during the biodegradation of 3000 mg/L phenol. The adsorption/desorption rates were also enhanced with increasing aqueous phase flow rate. EIHFMB performance remained unchanged over 400 h of operation under various operating conditions suggesting the stability of TOPO impregnation within the membrane. These results indicate the use of EIHFMB as a promising technology in solvent-free two-phase biodegradation of phenolic compounds.