Operations - Lincoln Sanitary District


The wastewater treatment at the Lincoln Sanitary District facility consists of a dual train, two stage, rotating biological contactor (RBC) process with primary and secondary settling, influent screening, aerated grit removal, chlorine gas disinfection and discharge to the Penobscot River. Treatment begins with a manually cleaned bar rack followed by aerated grit chambers with bucket conveyer grit removal to an inline screw type grit classifier followed by a communitor. When flows exceed the original design flow of 1.07 MGD but no more than a one hour peak of 2.8 MGD, another manually cleaned bar rack and a vortex degritter can be placed in service which can handle an additional 5.7 MGD during early spring rain and snow melt events. The flow is then sent to primary clarifiers followed by air driven rotating biological contactors, secondary clarifiers and chlorine contact chambers.

Primary sludge is removed from the primary clarifiers and combined with secondary sludge sloughed off of the RBCs. The combined sludge is dewatered (two one meter belt presses), composted and removed for beneficial use as a soil conditioner and low nitrogen fertilizer.


There are no industrial waste contributors to the facility. Commercial wastes are limited to discharges from schools, a hospital, restaurants, a laundromat / dry cleaner, a nursing home and a car wash. Wastewater is collected utilizing 17.4 miles of sanitary sewers with 11 pump stations. Wastewater is pumped to the treatment facility from 2 independent pump stations, Creamery Court Pump Station and Military Road Pump Station. Wastewater to the plant is a combination of domestic and commercial discharges. The strength (BOD5 and TSS concentrations) total load (BOD₅ and TSS daily mass), and temperature of the wastes are highly variable. This is mostly due to infiltration and other wet weather flows contributing to the wastewater.

Process Problems at the Lincoln Treatment Plant