Everyone is searching for ways to be greener, including communities looking for opportunities to make operations more energy efficient. One such opportunity offering excellent potential is your wastewater treatment plant (WWTP) - turning brown into green.
Wastewater and water treatment consumes up to 2% of the total electricity production in the United States. Increasing levels of treatment and maintenance are expected to cause operational costs to rise 30% to 40% over the next 20 years. [Wastewater Engineering: Treatment and Reuse. (2002). Metcalf & Eddy, Inc., Edition: 4th]
There are many ways to reduce energy consumption in WWTPs, which can improve the bottom line or provide regulatory-rate relief to the citizens of your community. Even if your plant is operating at peak efficiency, you might benefit now or in the future from the following suggestions for reducing your plant’s carbon footprint.
1. Upgrade Pump Stations
A significant portion of a utility’s energy usage is attributed to one or more pump stations used in virtually every community’s collection system. Older pumps were typically designed to operate at a single speed and on/off cycling. Today’s pump/motor/drive combinations are more efficient over a wider range of flows. Upgrading older pumps can produce long-lasting operation and maintenance savings. Inexpensive and more reliable variable frequency drives can also be used to match pump speeds to flow rates, further reducing energy needs.
2. Optimize Aeration
The aeration system in an activated sludge wastewater treatment plant accounts for over 50% of the annual electricity usage. You could optimize aeration by upgrading the blowers and air distribution system components with variable frequency drives and installing dissolved oxygen control systems, which can decrease the blowers’ electricity consumption. If you have aging blowers, consider replacing them with a single high-efficiency turbo blower, which has a wide range of operation and can be controlled based on dissolved oxygen. Do you have an aging diffuser system? If so, replacing the diffuser grid with new fine-pore or ultra-fine-pore diffusers will improve oxygen transfer efficiency and reduce the amount of air needed for treatment.
3. Improve Sludge Management
Solids handling processes use over 20% of the energy at a wastewater treatment facility, and pumping and disposing of solids requires energy every step of the way. Options to save money and energy are abundant, from minimizing transported water and solids to utilizing biogas for producing electricity and heating water, also known as co-generation.
4. Recover/Recycle Essential Nutrients
Phosphorus is an essential component in fertilizers. If your plant is currently utilizing or evaluating biological phosphorus removal you may consider the feasibility of creating a marketable commercial grade fertilizer. This turns a necessary operational cost into a new source of revenue for the utility while improving sidestream performance of the plant by reducing phosphorus loading in the recycle streams.
5. Go Light on Disinfection
Eliminate costly and hazardous chemicals by replacing your chlorine disinfection with an ultraviolet (UV) light disinfection system. Chlorine and dechlorination chemicals are expensive and energy-intensive to manufacture and transport. Energy usage of UV disinfection systems is minimal, and the decommissioning of hazardous chlorine disinfection systems is a major safety benefit.
6. Update Lighting and HVAC Systems
Operating a large facility consumes a significant amount of energy (averaging 9.3%) through lighting, heating, and cooling the enclosed spaces. If you have old T-12 fluorescent lighting fixtures in your plants, consider updating them to new high-efficiency T-8 fixtures, which will result in savings. In addition to energy savings, rebates are often available for these types of improvements.
7. Maximize Gravity
Mother Nature provides gravity for free, and we recommend you take advantage of it when making process improvements at your WWTP. Consider how your plant transports flow. Are you making the most of gravitational forces? If not, can your process be configured to let gravity, instead of electric motors, do the work?
8. Automate Operations
Supervisory Control and Data Acquisition (SCADA) can provide real-time data on the treatment processes in your plant. SCADA can automate the operation of your plant or allow the operator to control the plant remotely. The system can monitor equipment and alert the operator of emerging issues. When properly planned and integrated, the SCADA system can provide operators with the desired amount of hands-on versus hands-free control, freeing operators to perform other duties. Continuous monitoring and trending of various processes and equipment can reveal periods when energy usage can be reduced or peak energy loads can be shaved.
As you can see, there are many sustainable solutions in the area of wastewater processes that can help your community maximize the efficiency and minimize the carbon footprint of its system. The sooner you begin implementing these solutions, the quicker your Brown will turn into Green, and even help you save some green!