Scaling control during membrane distillation of coal seam gas reverse osmosis brine

Abstract

We systematically assess the efficiency of chemical cleaning and report a simple but elegant approach to control scaling during membrane distillation (MD) of brine from reverse osmosis (RO) treatment of coal seam gas (CSG) produced water. Results reported here show that increased feed water salinity and the permeation of CO2 from the feed solution resulted in only a small and gradual decrease in water flux. On the other hand, the precipitation of sparingly soluble salts on the membrane at high water recovery (>70%) led to a significant flux decline. Among the three chemical cleaning agents investigated, a reverse osmosis scale cleaning agent (denoted as MC3) was the most effective at restoring the water flux; however, MC3 cleaning was not able to completely remove scale deposits from the membrane and restore its surface hydrophobicity to the original value because of the complexation of scalants with CSG RO brine. The remaining scalants (i.e., silicates) reduced the membrane surface hydrophobicity and could possibly enhance concentration polarisation and act as seeding for further scale formation. Thus, a gradual decrease in MD performance with respect to both water flux and salt leakage was observed after each MC3 cleaning cycle. It was noted that the chemical cleaning agents themselves did not alter the hydrophobicity of the membrane; thus, the gradual decline in MD performance was attributed to the remaining scale deposits on the membrane after each cleaning cycle. Results reported here highlight the need to prevent membrane scaling and only use chemical cleaning as the last resort during MD treatment of CSG RO brine. Moreover, membrane scaling could be prevented by reducing concentration polarisation via limiting feed temperature and thus water flux. MD treatment of CSG RO brine with up to 80% water recovery without any observable membrane scaling was achieved at the feed temperature and the water flux of 35°C and 10L/m 2 h, respectively. AbstractWe systematically assess the efficiency of chemical cleaning and report a simple but elegant approach to control scaling during membrane distillation (MD) of brine from reverse osmosis (RO) treatment of coal seam gas (CSG) produced water. Results reported here show that increased feed water salinity and the permeation of CO 2 from the feed solution resulted in only a small and gradual decrease in water flux. On the other hand, the precipitation of sparingly soluble salts on the membrane at high water recovery (>70%) led to a significant flux decline. Among the three chemical cleaning agents investigated, a reverse osmosis scale cleaning agent (denoted as MC3) was the most effective at restoring the water flux; however, MC3 cleaning was not able to completely remove scale deposits from the membrane and restore its surface hydrophobicity to the original value because of the complexation of scalants with CSG RO brine. The remaining scalants (i.e., silicates) reduced the membrane surface hydrophobicity and could possibly enhance concentration polarisation and ...

Optimising thermal efficiency of direct contact membrane distillation by brine recycling for small-scale seawater desalination

“…Thus, the measured water flux deviated considerably from the calculated values, especially at high water recoveries. In addition, because the polarisation effects are magnified by elevating feed temperature, and hence increasing water flux [15,32], the deviation of the measured flux from the calculated values occurred at lower water recovery in the experiments conducted at higher feed temperature (Fig. 4A).…”

Graphene/PVDF flat-sheet membrane for the treatment of RO brine from coal seam gas produced water by air gap membrane distillation

“…In Australia, CSG produced water is mainly composed of sodium, bicarbonate and chloride [1,2]. Due to potential impacts of directly discharging CSG produced water on local ecological systems, there is a strong need to develop sustainable treatment process for its environmental safety [1,3,4,5]. CSG produced water requires advanced technologies for treatment such as RO because the salt removal from CSG produced water is a crucial point [4,6].…”

Treatment of Simulated Coalbed Methane Produced Water Using Direct Contact Membrane Distillation

“…In Australia, CBM-produced water has been mainly treated by reverse osmosis (RO) desalination before discharging to the environment, but there was a limitation in complete water recovery and operation costs [9]. Recently, membrane distillation process has been investigated for the treatment of coal seam gas produced water [10,11]. Pangarkar et al [12] noted that membrane distillation has some great advantages as compared to RO process, including performance and operation cost.…”