Reclaimation of petroleum-based wastewater by novel ozone immobilized biological activated carbon process

Wastewater reclamation in the petroleum industries in Northern China is important because of the shortage of water resource. Conventional treatment technology used in treating petroleum-based wastewater, namely the 3-phase biological process, typically removes COD, BOD, grease, volatile hydrobenzenes, cyanides, sulfides and suspended solids. However, the process is often ineffective in ammonia-nitrogen removal, and thus the treated effluent quantity can't meet the required standards for reuse. This paper investigated a novel ozone immobilized biological activated carbon (O₃-IBAC) process for ammonia nitrogen removal from petroleum-based wastewater. Operated at a HRT (Hydraulic Retention Time) of 15 minutes in IBAC1 and 27 minutes in IBAC2, the O₃-IBAC process achieved ammonia nitrogen removal efficiency of 91%. In addition, the removal efficiencies of COD, volatile hydrobenzenes, suspended solids, turbidity and petroleum-based micro-pollutants were all above 90%. Competition between the autotrophs and heterotrophs was observed, which was indicated by an increase of ammonia nitrogen removal with a decrease of COD removal, and vise versa. Nitrite accumulation in IBAC1 followed by erobic shortcut denitrification in IBAC2 led to 28% of the Total Nitrogen removal efficiency. Pollutant reduction in the IBAC process was achieved by a rapid physical adsorption and bio-degradation on the activated carbon, which effectively retained the pollutants in the system despite the short hydraulic retention time.