Techno-economic assessment of seawater reverse osmosis (SWRO) brine treatment with air gap membrane distillation (AGMD)

Authors: Martijn Bindels, Joana Carvalho, Carlos Bayona Gonzalez, Niels Brand, Bart Nelemans

Summary: Reverse osmosis (RO) is a widely used technology to desalinate water. In this work, several methods are proposed to increase the recovery of RO. The proposed methods are hybrid systems with a combination of RO, chemical deposition (CD) coupled with ultrafiltration (UF), nanofiltration (NF) and membrane distillation (MD). The proposed setups were assessed on a techno-economic level. The MD lab tests showed scaling on the membranes which indicate that pre-treatment is needed for treating RO-brine. Secondly, the proposed methods were tested on a pilot-scale to determine the maximum recovery of each system. The sensitivity analysis shows that the cost of water (COW) is mostly influenced by the total water production, which influences the capital cost. Therefore, more work is needed to reduce the capital cost of MD. When adding antiscalant to RO + MD, a base case COW of 0.633 USD/m3 and overall recovery of 84.59% was reached. The other setups had lower recovery, 66.93%, 72.73% and 73.38% for RO + CD + UF + MD, RO + NF + MD and RO + NF + antiscalant+MD, respectively, while the base case COW of these setups were 0.692, 0.7 and 0.698 USD/m3, respectively.

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