Simulation and optimisation of a SWRO system in Cape Town, South Africa

Abstract

Seawater reverse osmosis (SWRO) system is popular in most islands and coastal areas around the world with limited fresh water resources. A SWRO system was designed to fulfil 50% of the population water demand in Cape Town, South Africa, which can lead up to 383,353 m3/day in the next 15 years. The total dissolved solid (TDS) within the product (i.e. drinking water) was lowered to 600 ppm by referring to standard guideline stated by the World Health Organization (WHO). Design flowrate was set at 766,704 m3/day and the parameters such as feed, permeate, concentrate flowrate, number of vessels, number of membrane elements, number of stages, seawater chemical composition, temperature, pressure, and system configuration were considered in this study. Reverse Osmosis System Analysis (ROSA) 2017 software was integrated the design with simulation to further understand how different parameters affect one another in SWRO system. The TDS standard value of 600 ppm in the products were 73.76 ppm and 181.13 ppm after further optimisation. The efficiency of the SWRO system recovery rate was 75.87% and specific energy consumption (SEC) was 6.18 kwh/m3, greater than the previous value of 50% and 9.7 kwh/m3 in terms of recovery percentage and SEC respectively. The findings indicate that a lower amount of feed and energy is needed to achieve the desired production value. Hence, it is also resulting in major savings in terms of operating cost for SWRO system.