How the Treatment Plant Works

How the Treatment Plant Works
Your Home
Headworks Building
Bar Rack
Grit Removal Cyclone






From YOUR HOME All District wastewater enters the HEADWORKS BUILDING via a 24” diameter ductile iron sewer.   Removal of large solids by utilizing a vertical mechanical BAR RACK with manual bypass.  Grit and sediment accumulates in a 9’ diameter pista GRIT REMOVAL CYCLONE chamber

Screw Pumps
Primary Clarifiers
Rotating Biological Contractors





Influent flow measurement is ultrasonically determined within a 1.5’ H-Flume.  Two 36’ diameter CPC two speed enclosed SCREW PUMPS lifts all flow to the two rectangular PRIMARY CLARIFIERS.  Flow through the remaining treatment units is by gravity.  The Secondary Treatment of Wastewater consists of ROTATING BIOLOGICAL CONTRACTORS OR RBC’S

Wastewater is deposited in very thin layers on the Biomass as they slowly rotate 40% submerged in their eight cells. Aerobic microorganisms feed upon the dissolved nutrients.  When the Biomass becomes too thick to adhere, it “sloughs” off becoming secondary humus sludge.  Sludge that accumulates in the hopper is then transferred back to co-settle with the primary sludges.

Belt Filter Press
Chlorine Solution Tanks
Outfall Pipe

The blended sludges are dewatered on a 1.25 meter BELT FILTER PRESS, achieving a 22-25% solids dewatered cake

The final treatment phase is disinfection with a CHLORINE SOLUTION TANKS and total dechlorination with metabisulfitesolution.  With the completion of this phase the treated wastewater is safely discharged into the Pemigewasset River through an existing OUTFALL PIPE.