Improving bulk water pump station policies and operations in conditions of uncertain and changing demand

Abstract

South Africa is facing growing and complex changes in water demand; furthermore, acute water scarcity challenges due to drought and degradation of surface water resources threaten its ability to manage the demands. Industrial and power generation sectors in some regions are plagued with water shortages, requiring inter-basin transfer schemes for bulk water transfer to these regions. The complexity in the water demand is further exacerbated when the demand that bulk water transfer systems are designed to manage varies from the demand projections. This has resulted in inefficient pumping operations and unnecessary costs, which are causing great concern as a result of the current water crisis and the increasing cost of electricity in South Africa. This was an investigation to find out how the increasing energy costs and inefficiencies due to uncertainties in demand could be mitigated in bulk water transfer schemes in South Africa. This was done through determination of the impact demand changes and uncertainties have on bulk water transfer pump stations’ adherence to the operational policy, performance, and costs. Approaches to reduce costs associated with the changes in the demand and improve the operational performance of the pump station were proposed. The Jericho pump station in the Mpumalanga province, South Africa, was used as a case study to assess the impact demand changes have on the pump station’s operation and control, as well as the operational energy costs. The results of the assessment showed that all these three aspects of the pump station had been negatively affected by the variability in the demand, particularly the energy costs with operational costs due to pumping operations during peak periods contributing to 33% of the estimated energy costs during the study period. Optimal pump scheduling and a capital investment in the form of a booster pump station to assist the Jericho pumping system and changes to the pump station control policy are proposed, and it is determined that they would ensure a 17.02% saving in annual energy costs. Furthermore, it is shown that operational costs due to pumping operations during peak Time- of-Use (TOU) periods are more than three times the standard and off-peak tariffs, and as such pumping operations during peak periods should be minimized. This research report showed the significance of optimal pump scheduling and how operational policies of bulk water transfer systems should continuously be reviewed and improved if required, especially with the ever-changing demands.