Abstract: Volatile organic compounds (VOCs), such as benzene, toluene, ethylbenzene, xylene and methanol may be removed from wastewater obtained from oil or gas exploration or production operations by way of a bioreactor. The bioreactor may employ anaerobic microorganisms that metabolize various VOCs. In some embodiments, such a bioreactor may be configured to selectively change the temperature of the conditions of wastewater placed in the bioreactor, or of wastewater re-circulated through the bioreactor. A centralized valving or control station may optionally control heating or other conditioning elements for both feed and re-circulation systems.