Energy efficiency – it’s not just a catch phrase. It is something we can all take part in to ease the burden on the power grid and to our rate payers.
This a very popular and appropriate term being used quite extensively these days, certainly in our field of wastewater treatment we can and do see ways to apply this every day. Whether it is in the way we go about more efficiently performing tasks or in this case the way we use the energy needed to run the Wastewater Treatment Plants (WWTP) we are involved with.
When thinking of ways to apply energy efficiency, one that certainly comes to mind is the generation of energy. This can be accomplished via many ways within the WWTP; one way is through co-generation (Co-Gen) using anaerobic digesters. The gases created inside the digester are siphoned off via a foul air draw system and feed to a boiler to create steam which in turn runs a turbine generating electricity. This electricity is used to power most of if not all of the systems throughout the WWTP. In some instances the co-gen facility can generate enough electricity to not only meet the needs of the plant but has extra that can then be sold back to the power grid. This serves two purposes, saving the WWTP a significant charge for their power needs and creating a revenue stream for the WWTP that helps with the costs associated with running and maintaining the plant.
Throughout the New England area WWTPs are seeking out new technologies to increase energy efficiency; besides co-generation, wind and solar are also seeing an uptick in their respective applications to help with the energy needs of the plant. These two options have several advantages, first they are limitless sources of energy. They are non-polluting and they are relatively inexpensive to install & maintain. As part of the equation of deciding which technology to pursue, a facility needs to consider their location respective to terrain and within their respective municipality. Those plants still on the outskirts of town may want to look at both the solar and wind generation options, if growth has brought development close to the boundary of the facility then maybe the wind option will serve you best. Wind generation generally entails a smaller footprint.
In Pittsfield, MA the WWTP is going to bring on line a combination of wind & solar to ease their energy needs. They envision the system providing enough power to eventually take the plant off the gird. Likewise in Bangor, ME they are installing a small wind farm to generate 45-50% of their electricity needs over the next 20 years. They will use this electricity to power the control building and run the heating/cooling systems throughout the facility.
A key area that is being looked at throughout the industry is the huge amount of power being consumed daily by the Aeration basins. Without a properly set controller the blowers run continuously. The aeration basin is the single largest consumer of power in a WWTP; the average aeration system uses 35% of the total power consumed on a daily basis. One way to help negate this power usage is with a DO set point controller and DO sensors placed at key points within the basins. This allows plant operators to monitor the oxygen transfer rate and eliminate excess run time on the blowers. This saves wear and tear on the pumps and saves energy.
Energy efficiency, it’s not just a catch phrase, it is something we can all take part in to ease the burden on the power grid and to our rate payers.
Written by: Dallas Schwartz, NEWEA Sustainability Committee Liaison
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