A key benefit of public-private partnerships  for municipal water and wastewater systems is cost savings. Such savings can be derived from a number of areas: chemicals, equipment, power, sludge, etc.
As an industry, partnerships and their inherent cost savings have existed in the U.S. since Burlingame, Calif., partnered with a private operator in 1972. With more than three decades of operating, maintaining, servicing and managing water and wastewater utilities, private operators have the expertise to effectively utilize and maximize these facilities. With an estimated 11% of a water utility’s budget going to energy, reductions in consumption are one way private operators help municipalities generate savings.
Long viewed as a financial burden, power consumption is now considered a major environmental burden. Individuals and industry are both looking for ways to reduce energy consumption because of the current “green” movement. While nothing new, private operators are approaching power consumption as more than a way to save clients money—reduction of greenhouse gases is playing a larger role in these operators’ corporate responsibility programs.
For instance, Severn Trent Services  has documented energy reductions at projects for years. Beginning its partnership with Kingwood, Texas, in 1974, the company trimmed electricity costs at the 0.378-million-gal-per-day (mgd) Montgomery County Municipal Utility District 48 wastewater treatment plant (WWTP) by $6,000 a month by installing soft-start contactor and timers for the blowers.
In Jackson, Miss., Severn Trent reduced energy costs by 30% at the outset of the partnership, which began in 1985. By retrofitting the 46-mgd Savanna WWTP’s aeration system from coarse bubble to fine bubble, power costs have been reduced, saving the city $650,000 per year.
In 2008, Severn Trent undertook a program to identify additional areas of energy reductions at major (flow > 1 mgd) WWTPs the company operates in order to reduce greenhouse gases. Targeting five facilities geographically dispersed across the U.S., the company rolled out its pilot Site Energy Management Program (SEMP). Severn Trent’s Technical Services Group developed process/plant optimization models, with additional opportunities being identified by onsite personnel.
Following the plant optimization process, successful energy reductions were realized at all five facilities when year-over-year energy usage (kWh/million gal) was compared:
- Lehigh Acres, Fla., achieved a 26% reduction by continuous improvement in process control, allowing use of low-horsepower blowers to reduce energy consumption.
- Genoa, Mich., achieved a 21% reduction by an improved utilization of sequencing batch reactors, upgrading to HVAC systems and a continuous improvement in process control to save power.
- Newbern, Tenn., achieved a 16% reduction by process optimization, resulting in reduction on aeration and decreased levels in the oxidation ditch to lower amperage pull on motors and reduce energy use.
- Chandler, Ariz., achieved a 9% reduction by minimizing power usage through reductions in blower demand and optimization of recirculation pumps.
- Chickasha, Okla., achieved a 9% reduction by improved control of the sludge pasteurization system, which requires 600 amps of 480V electricity and reduction in the use of high-horsepower blowers.
Using the U.S. Environmental Protection Agency’s Greenhouse Gas Equivalencies Calculator  , the energy reductions above saved more than 806 tons of carbon dioxide (CO2)—equivalent to CO2 emissions from 83,012 gal of gasoline consumed or the annual greenhouse gas emissions from 134 passenger vehicles.
In these economically and environmentally challenging times, municipalities can prove to be sustainable on both counts through a public-private partnership. Operating more than 415 municipal water and wastewater facilities with combined flows totalling more than 677 mgd, Severn Trent plans to implement its SEMP at additional facilities this year, calculating further reductions in greenhouse gases.
Call it what you will—corporate responsibility, sustainability or going green—but such reductions are a step in the right direction that began more than three decades ago. As the environmental adage goes: “Think globally, act locally.” And don’t forget the cost savings to the client.