As anyone in the wastewater industry knows, energy consumption for treating processes is high, resulting in larger carbon footprints and higher cost. Wastewater treatment plants continue to seek solutions that lower energy consumption, from new technology to good, old-fashioned maintenance and upkeep.

Because energy is often the second largest operational cost after labor, efforts to reduce energy consumption can make a substantial difference in cost management. New water treatment plants are being designed with a consideration of maximizing resources and recovering energy, emphasizing a shift towards energy neutral or even energy positive facilities. Of course, even with this new approach, it is important that water quality be maintained as the number one priority, and investments be both fiscally responsible and recoverable in a reasonable timespan.

For existing plants, there are often energy improvements that can be made to reduce energy consumption or recoup energy. For example, a New Mexico plant, Las Cruces Utilities (LCU), invested $1.7 million to install 50 solar panels in its East Mesa Water Reclamation Facility just a couple of years ago. The initial investment allowed the facility to clean 700,000 gallons daily, which was used to irrigate green spaces at several large public locations. This solution also allowed the plant to add additional solar panels as the population and need for water increased.

Ironically, the organic matter in wastewater contains up to five times as much energy as the plant may use, and so figuring out better ways to recover that energy is also at the forefront of the effort. The challenge is finding ways to recover this energy without causing additional energy drains, as well as avoiding other unintended consequences.

New technologies continue to be developed and do offer the greatest promise for minimizing the energy consumption by plants. Water reclamation processes are becoming more efficient and prevalent, as well as the use of alternative energy sources. By exploring a variety of technologies and energy efficient approaches, innovators such as The Metropolitan Water Reclamation District of Greater Chicago (MWRD) has set a target to be energy-neutral by 2023, following the lead of many European plants as well as the East Bay Municipal Utility District in Oakland, California, which has moved beyond net-zero energy to actually selling energy back to the grid.

But what can smaller plants do that can’t afford new technologies and alternative energy sources? A good start is capital improvement plans developed to ensure regular maintenance and replacement of old equipment that does not operate as well, therefore keeping efficiencies high.

In 2010, Alliance Water Resources embarked on a joint project with their partners in Bowling Green, Missouri, to improve water efficiencies and reduce energy consumption. Alliance contracted with Environmental Dynamics, Incorporated and Vandevanter Engineering for the project, which was not only successful in reducing energy consumption, but paid for itself in a mere two years’ time.

The project consisted of several maintenance upgrades to the existing plant, including:

  1. Installing two variable frequency drive (VFD) units to the three blower units which provide air into the two aeration basins
  2. Using the VFD units to slow the rotational speed of the electric motors, resulting in less electricity used and less horsepower produced per blower; these VFDs also slowly ramp up the electric motors as needed, reducing the amount of stress placed on them
  3. Installing a total of 96 Flexair Minipanel diffusers within each of the two aeration basins, replacing the old Jet Tech SBR aeration header with equipment requiring less air, therefore resulting in less horsepower per blower
  4. Elimination of two 40 hp motive pumps which were no longer required for operations, resulting in less electric consumption

The effects realized from these updates were more oxygen transfer for the treatment process, reduced electricity consumption by elimination of motive pumps and the addition to the blowers, and reduced quantity of sludge produced due to better aeration. This reduction in sludge production also meant less sludge had to be hauled to farm fields for disposal.

The total project investment was estimated at $120,000, and the electrical savings estimated at $37,152/year. This, coupled with a one-time utility rebate of $55,000 (savings of $0.05/kW-hour), resulted in project payback of less than two years.

The quest for more efficient water treatment facilities must continue in a variety of ways if the industry as a whole intends to make a considerable difference. Through cooperation with conservation organizations, innovative technologies and common sense maintenance we will continue to see strides made.