Enhancing the treatment of petrochemical wastewater using redox mediator suspended biofilm carriers

Abstract

The treatment efficiency of petrochemical wastewater via the traditional activated sludge process is generally unsatisfactory due to the complex and toxic features of petroleum compounds. Redox mediator (RM) can improve the biodegradation of organic contaminants by participating in the microbial extracellular electron transfer process. However, the continuous dosing of the soluble redox mediator would lead to secondary pollution and rise operation cost. In this study, an insoluble and economical redox mediator material (biochar) was introduced into high-density polyethylene (HDPE) to prepare suspended biofilm carriers (RM-modified carriers), and applied in anaerobic/oxic (A/O) reactors. The reactor filled with RM-modified carriers (R3) showed the removal efficiency of chemical oxygen demand (COD) and phenol in the anaerobic zone were 34.6 % and 43.0 % respectively at organic loading rates (OLRs) of 22.2 kg COD/(m3·d), which increased by 6.8 % and 8.3 % respectively compared with that of the reactor filled with conventional HDPE carriers (R2), and increased by 12.4 % and 17.7 % respectively compared with that of the reactor without filled with carriers (R1). Microbial analysis proved that the relative abundance of Bacteroides that participated in electron transfer of R3 improved by approximately 6.3 % compared with that of R2. These findings demonstrated that RM-modified carriers improved the abundance of relevant functional bacteria and enhanced the degradation efficiency of the contaminants in petrochemical wastewater.