Aerobic biological fluidized bed technology treatment of sulfur and high ammonia-nitrogen waste water in a petroleum refinery

Wastewaters from petrochemical plants are of two types; high sulfur wastewater with high levels of sulfur, oil, chemical oxygen demand (COD) and phenol; and high ammonia-nitrogen wastewater emanating from catalyst workshops, which contains large concentrations of ammonia-nitrogen, salinity, suspended solids (SS) and lower organic pollutants. Conventional biological treatments are expensive and not very effective at handling both kinds of wastewater stream. In this paper, a new aerobic biological fluidized bed technology (ABFT) process is proposed, whereby a mixture of the two kinds of wastewater is treated. A pilot experiment has been conducted to examine the feasibility of treating the mixed wastewater stream. In the experiment, the initial mean concentrations of contaminants in the mixed wastewater are: COD = 2090 mg·L-1, NH4+-N = 600 mg·L-1, volatile phenol = 27 mg·L-1, and sulfide = 154 mg·L-1. After treatment by the ABFT process, the mean concentrations are as follows; COD = 95 mg·L-1, NH4+-N = 4.0 mg·L-1, volatile phenol 0.30 mg·L-1 and sulfide 0.0067 mg·L-1. The results meet the demands of China's National First-grade Standard for Integrated Wastewater Discharge. In the ABFT process, methods of dynamic oxidation, mixing and sedimentation are applied to wastewater pretreatment, with the use of immobilized microorganisms on a patented synthesized polymer carrier providing the core technology. The carrier employed as fluidized media in the ABFT reactor has a porous reticular structure, and it exhibits excellent mechanical strength and chemical characteristics. Highly efficient B350 microorganisms have been selected that can be immobilized on the carrier by chemical bonds. The Kjeldahl-Gunning test for nitrogen determination indicates that the mean average immobilized biomass on the carrier is 32 g·L-1 (H2O). Experimental investigations show that the proposed ABFT process has overwhelming advantages over the conventional sequencing biological reactor (SBR) process, particularly with regard to treatment of high ammonia-nitrogen wastewater. Meanwhile, the treatment efficiency and the resistance capacity against sudden changes in loading are both significantly increased.