The Town of Barre Wastewater Treatment Plant is a secondary treatment facility. It is designed for an average daily flow of 0.30 MGD. Peak hydraulic capacity is 1.15 MGD.
Wastewater is directed to the facility through a separate sanitary sewer collection system with the assistance of four (4) pump stations. The facility also receives septage delivered by truck. Septage that enters the facility is accepted through a septage receiving area where it is stored and aerated for a period of time, usually 24 hours, and then gradually pumped to the headworks to be treated.
Flow into the facility enters through an open channel of the headworks, then passes through the Grit King mechanical grit removal system and then through a channel monster grinder and an auger monster to remove large debris and wash the organics off of the captured debris. Poly Aluminum Chloride is then added for phosphorus removal. Grit and other solids removed from the system are disposed with sludge at the local landfill.
Following grit and coarse solids removal, the wastewater then travels to a 60,000 gallon tank that has been set up as an anoxic zone. Hydrated lime is added to this tank to maintain alkalinity and pH. The tank is constantly mixed. A portion of the return activated sludge is also pumped to this tank.
The wastewater then flows to a second 60,000 gallon equalization tank where flow is regulated by level transducers and pumps operated through a supervisory control and data acquisition (SCADA) system to maintain an even flow over a twenty four hour period.
From the equalization tank, wastewater then passes through a parshall flume where measurements are sent back to the SCADA system. Flow then enters the oxidation ditches through the distribution box where flow is equally split between the two ditches.
In the oxidation ditches, wastewater is mixed with return activated sludge. It is aerated to maintain a dissolved oxygen level of approximately 2.5 mg/l. The aerators are automatically operated by the SCADA system, receiving oxygen readings through a Hach LDO system. There are also 2 Flygt mixers in each ditch to keep the mixed liquor well mixed. Handheld dissolved oxygen readings throughout the ditches are taken daily and checked against the LDO system.
The oxidation ditches have a hydraulic retention time of about 25 hours. The discharge from the oxidation ditches passes over discharge weirs and into an outlet box where flow is then split equally between two 30-foot-diameter clarifiers. In the clarifiers, solids settle to the bottom while scum floats on the surface. A skimmer mechanism collects and removes the scum, which is then pumped back to the headworks to be reprocessed. Sludge is collected and then returned to the oxidation ditches and anoxic zone through pumps located in the basement of the plant. Once or twice per week, depending on the amount of solids in the system, sludge is removed to a waste holding tank and aerated. From this tank waste activated sludge is pumped to the belt filter press and dewatered. Polymer is used to assist in dewatering. Dewatered sludge is disposed at the local municipal landfill along with grit and screenings. Water from the belt filter press is sent to the septage holding tank and then pumped to the headworks for treatment.
Treated wastewater from the clarifiers passes over the weirs into an effluent trough. The effluent flows by gravity to the disinfection process, which consists of two ultraviolet light (UV) disinfection units. Disinfected effluent then flows by gravity, through the effluent flow meter. Treated effluent then flows by gravity to the Ware River.