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A novel hybrid fed-batch moving-bed bioreactor (MBBR) system was developed for the treatment of refinery wastewater containing a wide range of phenol (250–1,000 mg/L) and ammonia-nitrogen (50 mg/L) using an indigenous mixed microbial culture. A hybrid system containing a native mixed microbial consortium and comprising three MBBR units connected in series and operating with a 24-day hydraulic retention time (HRT) and a recycle ratio of 1.0 was evaluated under three environmental conditions. MBBR units in the system were operated in anaerobic, anoxic, and aerobic conditions in fed-batch mode. The hybrid system proficiently removed the phenol (99%), ammonia-nitrogen (95%), and reduced chemical oxygen demand (COD) (98%) from maximum feed concentrations of 1,000, 50, and 3,077±6 mg/L , respectively. The overall NH4-N removal efficiency of the system decreased by 4.7%, and COD reduction efficiency increased by 2% while varying the feed phenol concentration from 250 to 1,000 mg/L. However, the removal rate for phenol (20.72 to 82.42 mg/L·day) and NO3-N (10.57 to 17.81 mg/L·day) increased in the anaerobic and anoxic reactor, respectively. The ammonia removal rate for the aerobic reactor decreased from 8.14 to 7.377 mg/L·day. Ultraviolet (UV)-visible spectroscopy and gas chromatography-mass spectroscopy (GC-MS) were used to identify the formation of intermediates (catechol and muconic acid) during the biotransformation of phenol. Scanning electron microscopy (SEM) analysis showed better adhesion of the mixed microbial community in the pores of the carrier media. The best fit of the modified Stover-Kincannon model confirmed that phenol and NH4-N utilization is a function of organic loading rate under steady-state conditions. The results of this investigation suggest that the newly developed hybrid system with indigenous mixed microbes can treat the heterogeneous pollutants discharged in refinery wastewater. [ABSTRACT FROM AUTHOR]

In this study, a sequential fed-batch anaerobic–anoxic–aerobic (A2/O) moving bed biofilm reactor (MBBR) (A2/O MBBR) system will be employed for the simultaneous treatment of highly concentrated phenol, ammonia (NH4), and oxyanions [e.g., nitrate (NO3) and sulfate (SO42-)] from wastewater. The A2/O system efficiently removed phenol (99%) and NH4–nitrogen [NH4–N (95%)] with a 99% reduction in the chemical oxygen demand (COD) of the effluent for 3,000 and 200 mg/L of the maximum initial feed concentration, respectively with a 10-day hydraulic retention time (HRT). However, high removal of SO42- was achieved under anaerobic conditions (96%) for 100 mg/L of the initial feed concentration. The increasing feed phenol concentration (1,500–3,000 mg/L) inhibited NO3 reduction by releasing significant levels of NO3 in the anoxic reactor effluent and increased the SO42- accumulation in the anoxic and oxic reactors. Heterotrophic denitrification was reduced in the anoxic reactor by 15%–17% and increased the phenol concentration from 2,000 to 3,000 mg/L due to the highly toxic effect on the denitrifying microbes. NH4 removal by the anaerobic (R1) and anoxic (R2) reactors reduced from 87% to 65% and 66% to 46%, respectively, and increased the phenol concentration from 1,500 to 3,000 mg/L but the oxic reactor showed stable performance. Scanning electron micrographs (SEM) of the carrier media showed the better adherence of well-grown round and rod-shaped mixed microbes in different environments. Bacillus licheniformis was identified as the dominant species in the anoxic and oxic reactors by the VITEK 2 COMPACT system. Similarly, Kocuria kristinae was the predominant microbe identified in the anaerobic reactor. The outcome of this study revealed that an A2/O MBBR system that had an established indigenous mixed microbial culture could be a feasible technique to treat highly concentrated phenol combined with NH4 and oxyanions that are present in wastewater. [ABSTRACT FROM AUTHOR]