Wastewater Processing

Main Plant

The Berlin Pollution Control Facility started operating in August of 1979. The facility was designed to treat an average flow of 2.64 million gallons per day of wastewater and produce an effluent that will enhance the waters of the Androscoggin River; our recent upgrade project increased design flow to 3.0 million gallons a day.

Berlin Pollution Control is a Grade III secondary treatment, conventional activated sludge treatment facility. Located on the east side of the City on Shelby Street the Berlin Pollution Control Facility presently treats the domestic sewerage and some industrial wastes from the City of Berlin; it also receives septage from Motor Homes and from the surrounding communities.

The wastewater collection system includes six pumping stations which feed the main pumping station at Watson Street where large solids, rags, sticks, etc are removed by an automated bar screen and wash press in order to protect the mechanical equipment at the Treatment Plant. Three large Centrifugal pumps deliver the collected sewerage across the River to the Headworks structure from where it flows by gravity through the Treatment Process.

At the Headworks the wastewater flows through two aerated grit chambers, in which air is circulated causing organic material to stay in suspension and sand, grit, etc to settle to the bottom of the chambers for removal.

Degritted wastewater enters the primary clarifiers where settleable solids settle to the bottom. The accumulated mass is called primary sludge and removed from the bottom with 3 Positive Displacement pumps; it is delivered to Gravity Thickeners where it is blended with Secondary Sludge.

The supernatant wastewater then goes into 3 Aeration Tanks into which air is diffused through a branch network of fine bubble diffusers. The naturally occurring microorganisms (bugs) are supplemented here by the addition of Secondary Sludge, thus "activating" them in the presence of oxygen where they digest the organic and dissolved wastes.This activated sludge then flows into 3 Secondary Clarifiers where it settles out in a sludge blanket. A portion of this settled sludge is recycled to activate the supernatant entering the aeration tanks. The remainder is mixed with primary sludge in 2 Gravity Thickening tanks.

In the final step of the process, the treated wastewater flows into tanks where Sodium Hypochlorite is added for disinfection; subsequent addition of Sodium Bisulfite removes any residual chlorine before it is discharged into the Androscoggin River. The thickened sludge is dewatered with a screw press and delivered to the Mt. Carberry landfill for inhumation.