The identification and mechanism of a Scenedesmus spp. causing bio-fouling of an oil field produced water treatment plant

Crude oil extraction generates vast amounts of water known as produced water. The US DoE estimates that two to three barrels of water are produced for every barrel of oil and that approximately 140 million barrels of water are produced daily worldwide. In order to reduce oil in water and chemical oxygen demand (COD), a water treatment plant incorporating bioreactors was constructed to allow for disposal of produced water to the environment from an onshore production facility. However, since the attempted commissioning of the plant, process issues have been encountered due to heavy biofouling upstream of the bioreactor. Analysis by Fourier transform infra-red (FTIR) spectroscopy indicated that the causative agent was biological in origin. Extraction with 90% acetone and scanning spectroscopy identified the presence of chlorophyll a. DNA sequencing using 454 Pyrosequencing confirmed that the slime was microbial in nature and was composed predominantly of Scenedesmus species. A site audit was carried out to isolate the cause of the problem. This identified high phosphate levels from a storm drain entering the system and high bicarbonate concentrations likely from oil biodegradation. This likely contributed to growth of the algae identified in biofouling of the produced water treatment system. (C) 2015 Elsevier Ltd. All rights reserved.