Simulation and optimisation of a SWRO system in cape town, South Africa

Abstract

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) must be lowered than 600 ppm by referring to standard guideline stated by the World Health Organization (WHO). The 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 used to determine how different parameters affect one another in the SWRO system. The TDS product concentration obtained from ROSA pre-optimisation simulation results was 74 ppm, which was too low compared to the standard set. Therefore, a ROSA post-optimisation was done to increase TDS value to 181 ppm, which was closer to the standard. The efficiency of the SWRO system recovery rate was 76% and specific energy consumption (SEC) was 6.18 kWh/m3, greater than the previous value of 50% and lower than 9.7 kWh/m3 in terms of recovery percentage and SEC respectively. The a lower amount of feed and energy resulting in major savings in terms of operating cost for the SWRO system.