Wastewater Treatment Facility

The wastewater treatment facility is staffed by certified operators who conduct testing and maintenance throughout the year. The staff also maintains the collection system which includes of 20 pumping stations, and over 50 low pressure grinder pumps located throughout the Town. The gravity collection system consists of over 50 miles of mains ranging in size from 6 inches to 36 inches and is constructed mainly of both vitrified clay and PVC piping.

The Amesbury WWTP has been expanded and upgraded to treat an average daily flow of 2.4 million gallons per day and a peak hourly flow of 8.4 million gallons per day. The WWTP is a secondary treatment facility that employs the following unit processes to treat the Town's wastewater and septage; influent pumping, screening, grit removal, secondary biological treatment by means of the conventional activated sludge process, and effluent disinfection with sodium hypochlorite solution.

Functions

The treatment plant performs two basic functions:

1. It separates most of the solids and debris from the liquid
2. It kills most of the pathogenic organisms prior to discharging the final effluent to the Merrimac River

Sludge

A combination of physical, chemical and biological unit operations is employed to treat both the wastewater and the sludge. Sludge is a byproduct of the treatment process. The conventional activated sludge process is simply a biological means of converting organic matter, particularly soluble and colloidal organic matter into settleable solids that are removed through sedimentation in the final settling tanks.

Sludge removed from the wastewater treatment process is aerobically digested, a biological process that serves two functions. Aerobic digestion further reduces both the organic solids content of the sludge and the number of pathogenic micro-organisms contained in the sludge. The sludge is thus stabilized and less odorous. The stabilized sludge is then dewatered by centrifugation and hauled off site to Agresource's compost facility is Ipswich, MA.

Pretreatment Program

The staff has established a pretreatment program with the industrial users to expel industrial waste and heavy metals before entering the Town's collection system. The pretreatment program coordinator conducts industrial user inspections and industrial effluent sampling through out the year.

Additional Operations

In addition, to the operating and maintenance of the WWTP and the satellite pumping stations, the staff also responds to sewer backups, and flushes lines to prevent blockages. Also, the staff conducts inflow and infiltration investigation and removal by means of TV camera observation, and both smoke and dye testing of the collection system.