PUMPING SYSTEM ASSESSMENT IN WATER TREATMENT PLANTS. CASE STUDY: MEXICALI, BAJA CALIFORNIA, MEXICO

摘要

Energy and hydraulic efficiency are important goals for the sustainable development of water supply systems. The objective of these systems is to guarantee the delivery of enough water with good quality to populations. Although in order to achieve that, energy for pumping is needed, representing the main cost for the companies to operate the systems, since the energy costs vary with the amount of pumped water and the daily energy tariff. Water and energy are critical resources that affect virtually all aspects of daily life. Ensuring these resources are available in sufficient quantities when and where society needs them entails significant investments in planning, infrastructure development, operations and maintenance bills. Ever-increasing utility costs reduce profits, erode capital and maintenance budgets, increase product costs, and reduce competitiveness. Pumping systems are critically important to the operations of a water treatment plant. The amount of energy consumed by many long-running pumping systems often results in a substantial addition to a plant's annual operation costs. Therefore, these systems are a natural target to reduce energy consumption. Producers and users of pumps must design highly efficient pumping systems. The efficiency of these systems must be evaluated involving the multiple factors that often are difficult to understand for many users, consequently they overlook the energy costs and energy reduction potential on these systems. Methodologies that can maximize energy cost savings while satisfying system performance criteria should be sought for the design and management of the water distribution systems. This paper compares operating characteristic curves (OC curves) from a pump manufacturer with the curves obtained with field data, and evaluates the efficiency of the pumping system of raw water of a water treatment plant in Mexicali, Baja California, Mexico, which consists on a group of parallel identical pumps. The assessment also analyses the potential savings in costs and emissions of GHG related to the energy consumption of the pumping system if the operation conditions were the optimal, with the objective of minimize negative effects to the sustainable development of the region. Measurements of hydraulic and electrical parameters of the pumping system were made and efficiencies calculated. Actual characteristic operation curves were plotted and compared to those from the pump's manufacturer and up to 31% (average) difference in the efficiencies was found. Also emission factors of the electrical generation system of the state were applied to obtain the amounts of actual GHG emissions due to the operation of the pumps. The software PSAT was used to compute potential annual savings in MWh and costs and the results employed to calculate possible reduction in emissions.