Microfiltration, ultrafiltration and nanofiltration as a post-treatment of biological treatment process with references to oil field produced water of Moran oilfield of Assam

Abstract

The selection of an apt technology for the treatment of Oilfield Produced Water (OFPW) depends mainly on the quality of OFPW and methods of pre-and post-treatment processes. The most challenging part of the OFPW treatment process is the removal of Suspended Solid (SS), Oil & Grease (O&G) and dissolved organics. SS and O&G pose an acute problem to the membrane filtration system by fouling the membrane surface which increases operation & maintenance costs and decreases the life of the membrane. Fouling of the membrane surface is mainly attributed to the presence of low molecular weight aromatic compounds and naphthenic acids in the suspended and dissolved organic compounds. Thus, the removal of these suspended and dissolved organic compounds before membrane filtration proffers a challenge to the researchers. In this research, bioremediation process has been applied to remove the organic compounds and the performance and fouling behaviour of hollow fibre Microfiltration (MF), Ultrafiltration (UF) and Nanofiltration (NF) membranes after the bioremediation process has been analyzed in detail. The level of toxicity was determined by comparing the pollutants with the safe discharge limit for disposal into the environment set by Central Pollution Control Board (CPCB), India. The research presents its novelty by using a hydrocarbon-degrading bacteria, Pseudomonas aeruginosa for the Reduction of Organic Loads (ROL) from OFPW of Moran oil field of Upper Assam as a pre-treatment to membrane filtration. The Total Sum Corrected Area (TSCA) method through chromatographic analyses was used for this. The organic loads removal from OFPW by the TSCA method was found to be 67–100%, 100% and 100% after 7, 14 and 21 days of bioremediation respectively. The major parameters in feed OFPW of Moran oil field were found to be pH (7.5–9.3), Total Dissolved Solid (TDS) (1.79–4.75) ppt, O&G (1.78–2.8) ppt, Salinity (2.94–6.98) ppt, Chloride (Cl⁻) (1.6–3.86) ppt, Bicarbonate (HCO₃⁻) (2.89–4.03) ppt. It was observed that the ranges of pollutants removal by NF was highest such as TDS (26–86%), salinity (81–86%), turbidity (78–94%), hardness (67–75%), O&G (96–99%), Cl⁻ (80–89%) and HCO₃⁻ (95–97%).