Year Established: 2020 Start Date: 2020-03-01 End Date: 2021-02-28
Total Federal Funds: $10,000 Total Non-Federal Funds: $20,000
Abstract: A combined electrocoagulation, membrane distillation and crystallization process (EC-MDC) is proposed to treat produced water (PW) generated from hydraulic fracturing operations in the Fayetteville gas shale. Membrane distillation provides an essential pathway to treat PW because of its ability to treat water with high total dissolved solids (TDS), more than 100,000 mg TDS/L. Membrane distillation can theoretically concentrate the feed water to the solubility limit. Combined with crystallization, a near zero liquid discharge will result. However, membrane distillation still suffers from fouling, wetting and high energy requirements.To overcome the high energy requirement, we propose the use of inherent geothermal heat in this process. Due to the moderate temperature needed in membrane distillation (50-70 oC), shale gas PW that contains geothermal heat can be used directly to operate the membrane distillation system. The use of a pretreatment step is essential to suppress the fouling propensity of the membrane used in membrane distillation system. Thus, we propose using electrocoagulation (EC) pretreatment to achieve 90 % and 65 % removal efficiency of total suspended solids (TSS) and organic carbon (TOC), respectively. Preliminary EC data show significant reduction in membrane fouling, which can lead to long term durability of electrocoagulation-membrane distillation system. To mitigate scaling and obtain nearly complete recovery of water, we propose the integrated EC-MDC system. Our primarily results indicate that crystallization will address the issue of forming crystal nuclei in the feed bulk, which may cause inorganic scaling. The use of EC-MDC system can lead to a maximum water recovery of 80 %. In this proposal, we will optimize the design and the operating parameters of the integrated EC-MDC system. Our goal is to achieve more than 80% recovery of water as well as a high recovery of minerals.