Process improvement of sea water reverse osmosis (SWRO) and subsequent decarbonization

Abstract

An enhanced RO desalination system is presented which improves the efficiency of the coagulation system and helps to maintain (or even increase) first-pass recovery ratios, while simultaneously reducing the need for industrial acids, and antiscalants in the second-pass that potentially cause biofouling. The aim is to eliminate the use of expensive industrial acids for acidification of seawater during RO pretreatment processes; instead carbon dioxide (CO2) is injected after capturing it from the exhaust of power plants. The injection of CO2 into seawater essentially reduces the carbon footprint of the RO process. CO2 addition reduces scaling potential of carbonates and allows a higher recovery operation, it will also make acid and antiscalant dosing obsolete. The dissolved CO2 in seawater passes through the RO membranes. Consequently, the CO2 addition also lowers the pH of the RO permeate and brine, the presence of additional CO2 in RO permeate reduces the need of food grade CO2 in the post-treatment process. Low pH brine stream is an ideal condition for further brine concentration processes. Based on the cost of the carbon capture technology, a Life-Cycle Cost Analysis (LCCA) has been performed to access different alternatives for seawater acidification and determine the most cost-effective option.