Course: BFM 203 Water Treatment and Control

Lecture

(5/9)

Utilities and Reduced Energy Usage

Pumping is a huge cost for both water and wastewater utilities (over 90 percent in many cases). Methods implemented to help reduce the amount of power consumed helps reduce carbon emissions into the air. Many electrical companies also give rebates if varying frequency drives (VFDs) are purchased and used for pumping. These VFDs help save energy by ramping a pump up and down instead of running it at a constant speed.

Blower operation can account for almost 60 percent of a facility's total power usage. Use of automation and new technology (such as turbo blower) can also cut down the amount of power used for aeration.

In a converse process, wastewater digestion can help offset power costs at a plant. For example, the East Bay Municipal District in Oakland, California, converts post-consumer food scraps to energy using wastewater digestion processes (http://epa.gov/region9/waste/features/foodtoenergy/). The methane gas produced by the digestion process is captured and converted for use as fuel to run the power plant. One study showed that anaerobic digestion of food waste has approximately three times the methane production potential by volume than municipal wastewater solids.

Waste isn't just paper or plastic. It can also mean people/talent, financial waste, etc. Waste reduction techniques can also result in income/cost savings. Creative ways of getting rid of waste include production of fertilizer from biosolids. Encouraging customers to use less water or use it more efficiently is another method of cost savings.

Other technologies such as solar panels, wind turbines, etc., can also help offset dependence on carbon-based fuels. Some of these methods may require a large capital investment, but they save dollars over the life of the investment.

The table below outlines the savings achieved by one utility based on implementation of energy use reduction strategies.

Energy Efficiency Improvement | Annual Baseline Energy Cost | Annual Post-Implementation Energy Cost | Annual Estimated Savings
Cogenerate electricity and thermal energy on-site from waste methane | $4.6 million | $2.9 million | $1.7 million
Install high-efficiency pumps and motors with variable-frequency drives | $535,000 | $262,000 | $273,000
Discontinue second-state activated sludge mixing | $223,000 | $0 | $223,000
Add plastic balls to oxygen production vaporizer pit | $397,000 | $199,000 | $198,000
Inter-tie pipes on gas recirculation blowers | $167,000 | $0 | $167,000
Discontinue use of one digester | $158,000 | $0 | $158,000
Replace two small compressors at the pure oxygen plant with one large unit | $618,000 | $541,000 | $77,000
Estimated Total Annual Savings |  |  | $2.796 million