Pilot demonstration of the NH3/CO2 forward osmosis desalination process on high salinity brines

• Published in: Desalination 2013-03, Vol.312, p.67-74
• Main Authors: McGinnis, Robert L., Hancock, Nathan T., Nowosielski-Slepowron, Marek S., McGurgan, Gary D.
• Format: Article
• Language: English
• Subjects: activated carbon; Ammonia carbon dioxide forward osmosis; Brine; Brine concentrator; Brines; Calcium carbonate; Desalination; energy; Evaporation; Filtration; Forward osmosis; Hydraulic fracturing; natural gas; NH3/CO2; Osmosis; Pilots; Produced water; recycling; salinity; shale; Shale gas; Thermal energy; total dissolved solids; vapors
• ISSN: 0011-9164; 1873-4464
• DOI: 10.1016/j.desal.2012.11.032

An NH3/CO2 forward osmosis (FO) membrane brine concentrator (MBC) pilot was tested in the desalination of frac flowback and produced waters from natural gas extraction operations in the Marcellus shale region. The average concentration of these waters was 73,000±4200mg/L total dissolved solids (TDS), with an average hardness of 17,000±3000mg/L as CaCO3. Pretreatment included chemical softening, media filtration, activated carbon, and cartridge filtration. Average pilot performance characteristics were: system recovery of 64±2.2%, nominal water flux of 2.6±0.12L/m2-h, concentrated brine concentration of 180,000±19,000mg/L TDS, and product water with 300±115mg/L TDS. The thermal energy required by the FO MBC pilot, when operated within the efficient flow specification of the draw solution recycling system, averaged 275±12kWhth/m3 of product water, approximately 57% less thermal energy input than that estimated for a conventional evaporator operated in a comparable single stage, non-mechanical vapor compression (MVC) configuration. In an MVC configuration, which uses electrical rather than thermal energy, modeling indicates that the FO MBC process will require 42% less electrical energy than a conventional forced circulation MVC evaporator. ► Frac flowback from the Marcellus shale was treated in a NH3/CO2 FO pilot system. ► Average feed TDS was 73,000±4200mg/L, and hardness was 17,000±3000mg/L as CaCO3. ► Product water concentration was 300±115mg/L TDS. ► Energy use was 57% less than that estimated for an open cycle evaporator. ► Commercial system energy use is projected to be 42% less than MVC evaporators.