Abstract
M.Ing. (Engineering Management)
Water, energy and Greenhouse Gases (GHG) are components that are dependent on each other. Water is needed for the production of energy for fuel extraction, cooling power plants, processing of fossil fuels. In water cycles, energy is needed for, pumping, treatment and distribution of water and wastewater to and from customers. In South Africa (SA), the energy used in the water industry is generated mostly from fossil fuels, which has a significant negative impact on the environment. In light of this relationship, there is a growing recognition by energy practitioners that saving water helps save energy and GHGs that are associated with the production of electricity.
This research reviews a representative subset of the SA water industry to evaluate energy efficiency and harmful gas emissions optimisation potential. This is in line with the commitment the South African government has made in the Paris Agreement of 2015.
The first component of this study focuses on the review of the current energy efficiency in water distribution systems in SA. On the basis of the literature review, three technologies or practices are identified as being imperative in optimising water utilities in SA, to be more energy efficient; leak management, use of variable speed drives (VSD); and energy production from wastewater treatment plants.
The second component of this study involved the implementation of some performance indicators that show the interdependence of water loss, energy consumption and CO2, NOX and SOX emissions. These indicators are used to compare a few possible mitigation scenarios involving water loss reduction and increasing the system’s energy efficiency. The proposed indicators were applied to a complex urban water supply system serving the city of Johannesburg (CoJ). The CoJ water network has 7 regions, 89 water reservoirs, 10 depots, 28 water towers, 6 wastewater works,31 water & 35 sewer pump stations, 92 164 valves & hydrants and 12 581 of water pipelines supplying approximately 1574 Ml/day. The current pumping systems for all seven regions within CoJ are analysed and compared with an alternative pumping system which uses VSDs. The difference in energy consumption and greenhouse emissions in the two systems is noted. The potential energy generation from wastewater treatment plant is also investigated and compared to current practice at these facilities within CoJ.
The presented scenario analysis (use of VSD, leak management and co-generation of electricity) concluded on the following:..