Detailed organic characterization of process water to evaluate reverse osmosis membrane fouling in industrial wastewater treatment

Abstract

One of the major waste streams within the oil and gas (O&G) industry is produced and process water generated during hydrocarbon production and treatment, respectively. In gas production facilities, process water typically has lower salinity (i.e., <10,000 mg/L) which present opportunities for these wastewaters to be treated for beneficial reuse applications via advanced water treatment technologies, such as reverse osmosis (RO) membranes. One of the key challenges for RO membranes application to industrial wastewater treatment is fouling which is frequently attributed to the soluble organics present in the water and/or associated with field chemicals. In this study, a detailed organic characterization methodology, using liquid chromatography with organic carbon detector (LC-OCD) was applied to characterize the organics on a real process water collected from industrial wastewater treatment plant at a gas production facility. Additionally, a rigorous bench-scale testing procedure was implemented to assess the performance of a full-scale RO system with and without activated carbon filter (ACF) pretreatment, making this study the first one to apply LC-OCD methodology on real wastewater to evaluate the fouling of RO membranes deployed at an industrial treatment plant. Bench-scale RO results showed that in the absence of ACF pretreatment, a 12 % decline in membrane permeability (from 1.78 to 1.57 L/(m2-bar-h)) was observed, while no permeability decline was measured after ACF treatment. The organic fouling was confirmed by mass balance calculations on the bench scale experiments as well as Fourier Transform Infrared (FTIR) analysis on the membrane coupons. Moreover, LC-OCD analysis showed that the ACF inlet has a TOC concentration of approximately 3.06 mg/L; of those 1.29 mg/L (42 %) are hydrophobic, and 1.77 mg/L (58 %) are hydrophilic. After ACF treatment, the hydrophobic organics decreased to 0.65 mg/L, revealing that the ACF is removing >50 % of hydrophobic organics which are likely responsible for membrane fouling. Bench-scale operational and water quality results were comparable to the full-scale RO performance data validating the lab testing procedure implemented in this study.