(701g) Pilot Scale Osmotic Concentration Process for Reducing Injected Wastewater Volumes in Gas Field Operations

Over the past 10-15 years, there has been increasing attention in the development of forward osmosis (FO) technology as a low-energy technical solution to wastewater treatment. The significant energy benefit arises in applications where direct recovery of the permeate product from the draw solution (DS) is obviated such as osmotic concentration (OC) process.
In the current work, a flexible pilot-scale unit, based on FO process, was designed and constructed for the treatment produced and process water from Qatar’s gas operations. The FO pilot unit, without the DS recovery step, was applied as an option for wastewater volume reduction for gas field operations in Qatar. The pilot unit uses seawater (40 g/L TDS) as a DS and wastewater generated during gas operations as a feed. This feed water is of comparatively low conductivity (~ 2 g/L TDS), making it unusually suited to treatment by OC. The diluted DS could be directly discharged into the ocean; so the energy-intensive step of DS recovery is entirely eliminated.
Two hollow fiber FO membranes (Toyobo and NTU) were tested to assess their performance and fouling propensity on both synthetic and real wastewaters. Results demonstrated that the membrane can achieve feed water recoveries up to 90% without any scaling issues. Flux ranges from 2.25 to 12 LMH for feed recoveries between 60 and 90% using a constant 4X dilution rate of the draw solution. Furthermore, the pilot unit maintained a stable water flux of 10 and 1.92 LMH at 75% feed recovery using NTU and Toyobo respectively. The robustness of the pilot unit was investigated for over 48 h of continuous operation. This work will present the operational data of the pilot unit for both membrane modules under synthetic and real wastewaters