A novel hybrid system for continuous biodegradation and toxicity removal of low molecular weight phthalates

Abstract

Dimethyl phthalate (DMP) and diethyl phthalate (DEP) are environmental toxicants that can interfere with the endocrine system and cause adverse health impacts by mimicking the natural hormone activity. The present study focused on the biodegradation of DMP and DEP mixture by Cellulosimicrobium bacteria in a bioreactor under batch, fed-batch, continuous and continuous with biomass recycle modes. Biomass recycling was done followed by microfiltration using an indigenous low-cost tubular ceramic membrane. Under the batch mode of operation, maximum degradation values of 85 % and 58 % were observed at 1000 and 2000 mg/L initial concentrations of DMP and DEP, respectively, in mixture, whereas, complete degradation was achieved in the fed-batch system at the same initial concentrations. In continuous operation mode at 24 h hydraulic retention time, complete degradation was achieved for all inlet DMP and DEP concentrations. The biomass recycle operation mode was found to be the best strategy owing to complete degradation of the phthalates, even at very high inlet concentrations and at a short hydraulic retention time (HRT) of 16 h. A high germination index (GI) value of 91.86 % and 0 % brine shrimp mortality further demonstrated the potential of the biomass recycle system for the treatment of phthalate containing wastewater.