Energy–water and GHG nexus: A South African water industry case

Water and energy are resources that are dependent on each other. Water is needed for the production of energy for fuel extraction, cooling power plants, and 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. This research reviews a representative subset of the SA water industry to evaluate energy efficiency and harmful gas emissions optimisation potential. The first component of this study involves a review of the current energy efficiency potential in water distribution systems in SA. On the basis of a literature review, three technologies/practices were identified as being imperative in optimising water utilities in SA. The second part of this study involves the implementation of some performance indicators that illustrate 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 third component of research is developing a novel multi-layered structural water distribution system model by incorporating 29 metrics extracted from the literature reviewed. Analysis of this model is then conducted using a MULTI-MOORA (Multi-Objective Optimization by Ratio Analysis) technique accompanied by a Triangular Fuzzy Number set. The aim of this was to assist water utility managers to identify the most influential performance indicators for attaining the nexus objectives.