Scaling mitigation in submerged vacuum membrane distillation and crystallization (VMDC) with periodic air-backwash

The applicability of periodic air-backwash to alleviate crystal fouling in submerged VMDC for inland brine water treatment was investigated in this study. Using polypropylene membrane and modelled inland brine solution at very high concentrations, the effect of air-backwash was evaluated against water production for operation parameters, such as backwash pressure, frequency and duration. At the optimized operation parameters, the flux decline was successfully delayed, resulted in up to 150% and 25% increase in permeate productivity and crystal production, respectively. Incorporation of feed stirring and relaxation mode to submerged VMDC operation with air-backwash further increased the permeate productivity and crystal production by 230% and 32%. Application of chemical cleaning once every 10 h of submerged VMDC operation using 2 wt% of citric acid and 50 wt% of ethanol resulted in sustained performance up to 6 cycles of operation for accelerated tests of highly concentrated feed.