Phenol degrading and chromium (VI) reducing biofilm system : effect of shock-loading

Abstract

Hexavalent chromium [Cr(VI)] which are discharged together with organic pollutants in effluent streams from industry pose a health hazard to humans. The present study observed the reduction of Cr(VI) in presence of phenol using microbial culture consortium originally obtained from Brits Waste Water Treatment Works (North West Province, South Africa) immobilised on ceramic beads in a packed bed reactor. The reactor was stabilised under a phenol feed of 1,500 mg/L and 30 mg/L of Cr(VI). After introducing a shock-loading of 40 mg/L of Cr(VI) and 1,500 mg/L of phenol, Cr(VI) concentration approached influent values in less than 3 HRTs (48-51 h). It took about 144 h for the system to recover after the feed conditions were re-established to 10 mg/L Cr(VI) and 400 mg/L of phenol, and the reactor achieved complete removal efficiency at operating condition of 10 mg/L Cr(VI) influent concentration. Results from this study also suggest that intermediates from the degradation of phenol served as electron donors in the reduction of Cr(VI), whilst the primary compound, which is phenol, remained relatively the same, thus, its degradation was inhibited by intermediates. The microbial culture consortium from Brits have the potential for efficient and simultaneous removal of organic pollutants and heavy metals in complex wastewaters.