Hybrid based bioelectrochemical system (BES) configured with embedded anode and cathode electrodes in soil was tested for the bioelectrochemical degradation of petroleum refinery wastewater (PRW). Four applied potentials were studied to optimize under batch mode operation, among which 2 V resulted in higher COD degradation (69.2%) and power density (725 mW/m(2)) during 7 days of operation. Further studies with continuous mode of operation at optimized potential (2 V) showed that hydraulic retention time (HRT) of 19 h achieved the highest COD removal (37%) and highest power density (561 mW/m(2)). BES function with respect to treatment efficiencies of other pollutants of PRW was also identified with respect to oil and grease (batch mode, 91%; continuous mode, 34%), total dissolved salts (batch mode, 53%; continuous mode, 24%) and sulfates (batch mode, 59%; continuous mode, 42%). Soil microenvironment in association with BES forms complex processes, providing suitable conditions for efficient treatment of PRW.