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What's New

Cost Effective & Efficient

The Mattabassett District, the fifth largest facility in Connecticut, continues to be in the top ten in lowest costs per gallon of wastewater treated, and one of the most efficient.


In 1992, the District was one of the first wastewater treatment plants in the northeast to install a Supervisory Control and Data Acquisition (SCADA) System with programmable logic controllers (PLCs) to monitor and control the treatment process. This enables one person on each shift to manage the entire facility from the control room and still have time to perform other tasks. One of the biggest benefits is that staff no longer walk several miles a day, just to turn equipment on and off. Operating the facility through SCADA is analogous to flying an airplane on auto-pilot.

Leading Technologies

The Mattabassett District maintains high standards of excellence in all areas and continually evaluates and installs the best available leading-edge technologies. A few of the many systems we are using are wet-packed tower odor scrubbing, biofiltration, carbon adsorption for incinerator mercury emissions control, and ultra-high efficiency filters for sub-micron particle removal from incinerator emissions.

In 2003, in response to Connecticut DEP nitrogen removal requirements, The Mattabassett District converted two empty aeration tanks into nitrification/denitrification treatment systems. This, and a number of process changes to our secondary treatment processes, resulted in successfully modifying a facility which was not originally designed to remove nitrogen into one that removes over 50% of the nitrogen entering the facility.

In February 2007, The Mattabassett District's new outfall – a 140-foot extension with 160 feet of 16 diffusers located in the deeper part (a depth of 20-plus feet) of the Connecticut River – went online. This has meant that The Mattabassett District's treated effluent discharge is no longer visible. Also, it mixes over a wider segment of the river and is more quickly assimilated.

In April 2007, The Mattabassett District's two new 1.5 megawatt emergency generators became operational. This means that, for the first time, The Mattabassett District can provide power to the entire facility if there is a power failure in the CL&P system. It also means that should the CL&P system be overtaxed and needs additional power, The Mattabassett District's power generators can be activated immediately and we can not only supply our own power, but can add an additional 1.4 megawatts to the grid.