Abstract
Global population growth, climate change and economic expansion have become a concern since it will affect water supply in the future. Overcrowded townships in most developing countries experience low water supply. Numerous nations are looking into ways to supplement their current water supply to deal with the issue. One feasible and sustainable way to ensure a sufficient supply of potable water is through water reclamation.
This study highlights some of the crucial success criteria that should be taken into account when considering water reclamation from the secondary discharge emanating from municipal wastewater treatment works for the expanding township of Diepsloot, in Johannesburg (South Africa). As of 2022, Diepsloot had a population of around 350 000. Consequently, the lack of bulk water facilities to supply the area causes frequent water shortages. A direct potable water reclamation plant from treated municipal wastewater has been proposed.
The water treatment plant process was designed and simulated using Aqueous Material Balance (AqMB)®, a process modeling simulator program for water treatment processes to estimate water quality and quantity. Based on the findings, the quantity and quality of water, as well as the selection of treatment technology are key. The simulated treatment process proposed here-in includes clarification, ultra-filtration, reverse osmosis and disinfection steps, and indicated successful removal of contaminants (turbidity, NH3, NO3, NO2, Mn and bacteria) to acceptable SANS 241:2015 drinking water standards. A population of 350 000 people can be supplied with 109 L/day of potable water. This suggests that there is a potential for direct potable water reclamation to supplement the current water supply to support expanding populations in areas with limited natural water sources.
An economic assessment of the simulated process plant was performed and suggested that the project is economically viable since it showed a positive Net Present Value (NPV) of R 72 725 058.26 using a discount rate of 9% over a period of 20 years, an Internal Rate of Return (IRR) of 11.290%, higher than the discount rate of 9% used in the NPV calculation, a positive Return on Investment (ROI) and a Payback Period (PP) of 14.10 years, shorter than a typical economic lifetime of 20 years for these types of processing plants. It is then concluded that the proposed system is technical and financial feasible.