75% energy savings from Enaqua UV solution

Ayer WWTP has saved more than $38,000 a year on energy and increased life time expectations of the UV disinfection system.



Project Background

Ayer Wastewater Treatment Plant (WWTP) operated two relatively new UV Disinfection systems that were not meeting disinfection permit requirements. The WWTP received a Notice of Noncompliance in February 2012 and was told to correct their deficiency. Ayer’s Sewer Department Staff therefore began to look for a UV solution that could meet their requirements and address their large operational costs from power consumption.


The Enaqua Solution

Ayer WWTP received two Non-Contact UV units from Enaqua in January 2013. These were placed in parallel as were the previous UV systems. Due to the disinfection effectiveness of Enaqua’s solution, Ayer only uses one unit at a time alternating every 2 weeks to prolong the lifetime of the units and to save energy. Enaqua’s Non-Contact UV solution is designed so that it does not require a fixed water level in order to operate, but accommodates the natural flow of the water coming into the system. With the integration of Enaqua’s Flow and Level Pacing system, automatically only the necessary UV lamps are turned on.


Advantages and Benefits

Today, Ayer only uses one of the UV units at a time, because of the high performance of the unit. This not only lowers the energy consumption, but also lengthens the lifetime of each unit. Ayer WWTP has moreover gone from an annual energy bill of $ 50,458 to a bill of $ 12,334 – an energy reduction of 75%. The return on investment horizon is therefore significantly lower than initially expected and the system life time considerably prolonged.

"The fecal kill is down to single numbers. I have never seen that before on UV systems. And we are only using one unit at a time – half the energy – because of the excellent performance of the units."

Ayer Wastewater Treatment Plant


System design parameters
Peak Design Flow2.4 MGD
Average Daily Flow1.4 MGD
UV Transmittance65%
Base ProductC-Series
Upstream TreatmentActivated Sludge
Year Installed2013