Water and wastewater systems have been estimated to account for 4% of total electricity demandin the US. The demand for water from a growing population is rapidly outstripping the supplyavailable from the highest quality water sources, so agencies are turning to lower quality sourcesof supply. To treat these waters and at the same time meet increasingly stringent drinking waterregulations, agencies are implementing sophisticated advanced treatment technologies (ATT),such as ozonation and UV, methods that require more and more electrical energy. The energyconsumption issue is further aggravated by the ever-increasing energy cost. While the cost oftreatment equipment has been decreasing due to advancements in technology, the cost of energycould be escalating. For example, due to the significant decrease in membrane costs during thelast 20 years, energy consumption is now the second largest fraction of unit water cost (capitalrecovery represents the largest fraction) for seawater reverse osmosis (RO) desalination. For oneof the most recently constructed plants, at Point Lisas, Trinidad, energy represents 23% of thetotal water cost. This AwwaRF funded project surveys 11 participating utilities that utilizevarious types of ATT. Energy consumed by UV process is found to be merely 0.001 kWh/kgal,and ozonation process consumes 0.05-0.12 kWh/kgal of energy. This study also concludes thatenergy efficiency is greatly affected by the ratio of operation capacity to design capacity. Energyefficiency is much higher (lower energy consumption per unit of water produced) when thesystem is operated at or close to the design capacity. When the system is operated at lowerproduction such as during winter time, energy efficiency decreases sharply.
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