Enhanced reduction of COD and aromatics in petroleum-produced water using indigenous microorganisms and nutrient addition

Abstract

Petroleum reservoir produced water is a high volume waste stream that is frequently hypersaline with a high chemical oxygen demand (COD) as well as containing water soluble aromatic compounds such as phenols. Biological treatment of produced water is problematic due to the high saline content, which inhibits conventional wastewater treatment systems. Phenol, benzoic acid, and para-hydroxybenzoic acid degrading Halomonas sp. were isolated from hypersaline produced water (100 g l−1 NaCl) from a standard storage facility demonstrating that the indigenous microbial population had the potential to degrade aromatic compounds. Addition of specific nitrogen, phosphorous, and carbon sources under aerobic conditions was shown to stimulate the indigenous population. Chemical oxygen demand reduction increased from 20% without additions to as much as 65–80% with the addition of low levels of phosphate combined with alanine or glucuronic acid, or tryptone in combination with glucuronic acid. Phenol and benzoic acid were also shown to be significantly reduced in those cultures where significant improvement in COD reduction was observed. The results indicated that the indigenous microbial population in hypersaline produced water can be used to successfully reduce the COD and remove aromatic compounds using nutrient addition without dilution of the saline content.