Produced Water Treatment by Semi-Continuous Sequential Bioreactor and Microalgae Photobioreactor

Abstract

Abstract Produced water (PW) from oil and gas exploration has adverse effects on aquatic life and living organisms that need to be treated before discharge. However, proper treatment is essential to meet the permissible limits. In the study, the PW was first pre-treated with activated sludge. The pre-treated PW was then utilized as a feed for the Scenedesmus obliquus microalgae in a 13 L photobioreactor. Initially, 10% of the PW was introduced in 90% microalgae culture, and after exponential growth, an additional 25% of PW was added without any additional nutrients. This study has demonstrated the impact of semi-continuous treatment on the growth of microalgae as well as the removal of pollutants including total organic carbon (TOC) and heavy metals. Moreover, salinity, electrical conductivity (EC), pH, and total dissolved solids (TDS) of the PW-microalgae culture were assessed. The removal efficiency for TOC, TDS and EC was 64, 49.8, and 49.1% respectively. Furthermore, S. obliquus has effectively removed barium, iron, and manganese heavy metals 95, 76, and 52% respectively. S. obliquus has been found to be able to grow in a mixotrophic environment as it has reduced TOC in the PW.