Plant Flow & Upgrades  

2. Aeration Tanks - The raw wastewater flows through a distribution box, where it mixes with return activated sludge from the clarifiers and is introduced into biological treatment. Here, microbes remove pollutamts and form floc, which is activated sludge. We have configured the aeration tanks through our PLC system to have low oxygen zones. These zones force the microbes to use nitrogen instead of oxygen, therefore providing nitrogen removal. The aerators are four 75 horsepower mixers, two per tank, that provide mixing and oxygen for the biological process. During the plant upgrade, an anoxic tank will be constructed between the headworks and the aeration tanks. Here, the raw wastewater will be introduced to RAS sludge with no oxygen, only minimal mixing. This will increase our nitrogen removal capabilities, and help to stabilize the process.

3. Secondary Clarifiers - Here the flow from the aeration basins is slowed down, and given time to settle, the cleaned wastewater separates from the activated sludge. As the sludge is settled, a portion is returned to the aeration basin by RAS pumps, and a portion is sent to the Digester building holding tanks for dewatering with the belt filter presses. Daily calculations tell us how much to waste to keep the plant in balance. The upgrade will involve new skimming equipment, to be done by the Town, to remove floating waste, such as grease, from the surface of the secondary clarifiers. A new secondary clarifier is to be constructed, which will increase the hydraulic capacity of the plant.

4. Chlorine Contact Tank - The clarified wastewater flows to the contact tank to be disinfected by sodium hypochlorite. The dose of chemicals is determined by the flow rate, measured at the end of this tank by two ultrasonic flow meters. After the flow meters, the cleaned wastewater flows through a pipe and enters the Connecticut River. The upgrade will involve restructuring of this tank to install an ultraviolet light disinfection system, which will eliminate the use of chemicals.

5. Control Building - The WAS, waste activated sludge, is pumped to two belt filter presses. Polymer is mixed with the sludge to facilitate dewatering. The sludge cake is loaded into the dump truck through a chute, and is taken to Hartford MDC for final disposal. The lab, offices, and garage are part of this building. No improvements are scheduled for this area, as you may recall, both presses were rebuilt in the summer of 2001.

6. Equalization Tanks - The equalization tanks are currently off-line, and plans are to fill them in. This system was originally designed to stabilize Hood's flow through mixing and aeration. The flow from Hood is already mixed and adjusted for pH since additions were made to their facilities in November 1996. This system has always been maintenance intensive due to the heavy grease solids that were formed on the surface. No upgrade is planned for this system.

7. Pump and Chemical Building - This building houses the chemical feed systems, main electrical components, RAS pumps, WAS pumps, emergency generator, and plant water system. The plant water system pumps plant effluent for cleaning and use by the belt filter presses. New pumps for the new secondary clarifier will be installed in this building. At some point, the building will need a ventilation system, none is proposed during the upgrade, as the Town will address this in the future with O & M monies.

8. Digester Building - This is essentially the original plant building. The building houses our belt press sludge pumps, blowers to aerate the equalization and sludge holding tanks, electrical components, maintenance shop, and storage areas. No upgrades are planned for this building.

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