Microbial community dynamics in hybrid biological reactor treating petrochemical wastewater

Abstract

Hybrid biological reactor (HBR) was developed by adding carriers to the aeration tanks, and could be applied to improve the poor nitrification ability of overloaded petrochemical wastewater treatment plants. Using the normal activated sludge process (ASP) as a control, the performance of ASP combined with HBR for the treatment of petrochemical wastewater was studied. When the influent load was 0.97 kg COD_Cr/m³ d (COD_Cr, Chemical Oxygen Demand with the oxidant of K₂Cr₂O₄), effluent of ASP contained 138.2 mg/L COD_Cr and 8.2 mg/L -N, and the COD_Cr and -N concentration in effluent of HBR was 120.8 and 1.6 mg/L, respectively, indicating that both processes had good removal capacities for petrochemical wastewater. When the load was increased to 1.94 kg COD_Cr/m³ d, there was no apparent change in effluent COD_Cr values of HBR and ASP. However, a great difference in the removal efficiency of -N between HBR and ASP was observed. -N concentration in effluents of ASP and HBR was 16 and 1.7 mg/L, respectively, suggesting that HBR had a much better treatment capacity for -N than ASP. Using ribosomal intergenic spacer analysis fingerprinting and 16S rDNA sequence analysis, a big difference in microbial community structure was found between the two processes. And there existed simultaneous nitrification and denitrification in HBR system. Compared with ASP, HBR had more advantages, such as high utilization of oxygen, less sludge generation, and lower power consumption.

Keywords:

• Petrochemical wastewater
• Hybrid biological reactor
• Organic loading rate
• Nitrification
• RISA

Acknowledgments

This work was supported by the Fundamental Research Funds for the Central Universities (DUT14LAB09) and the National Crucial Research Project for Water Pollution Control of China (2012ZX07202-002).