The Superintendent and the Assistant Superintendent offices are located in the administration building. Testing parameters of the wastewater is done according to the Environmental Protection Agencies (EPA) National Pollutant Discharge Elimination System Permit (NPDES).

Here the dewatered cake is mixed with amendments (woodchips and sawdust) and placed into piles inside the composting shed. The piles must generate temperatures in excess of 55 degrees Celsius for 3 days and greater than 40 degrees Celsius for 14 days to demonstrate the pathogen and vector attraction reduction as per the regulations. After a minimum of 21 days, the compost is then screened through a trommel screen. This is done to recover amendments for re-use.

The compost is then moved to an outside curing pile for 30 days. Once this process is completed the compost is ready for use.

Chlorine gas is used to disinfect the treated effluent at the facility. Sulfur Dioxide gas is used to de-chlorinate the effluent prior to discharge to the Town River.

Headworks consists of comminutor, aerated grit removal system, and primary sludge pumps.

Comminutor

A device that cuts and shreds any solids in the wastewater that passes through its screen. All particles passing through the comminutor are cut to 5/16-inch or smaller.

Aerated Grit Removal System

The system consists of positive displacement rotary blowers to supply required air for the air diffusers, screw conveyor, and the grit cyclone classifier.

Grit is removed from the plant influent flow to prevent abnormal wear on plant equipment due to the abrasive nature of the grit particles (such as sand, cinders, wood chips, coffee grounds, etc.). In addition, grit removal prevents the accumulation of these materials in the Primary Clarifiers which would cause a loss of usable tank volume.

Primary Sludge Pumps

Pump the settled sludge from bottom of the Primary Clarifiers to the sludge holding tank.

Septage receiving station at the facility accepts septage from private haulers and stores it until the plant conditions allow this additional waste to be added to the system. Within the tanks there are submersible mixers that prevent the solids from settling while its being pumped.

 

100 Morris Avenue
Bridgewater, MA 02324

There 2 primary clarifiers. Each clarifier 40 feet in diameter with a side water depth 7 feet.

The primary clarifiers remove settleable solids, scum, and a portion of the BOD from the wastewater, preparing it for further treatment The removal of the settleable solids is accomplished by allowing the wastewater to move through the clarifiers at such a reduced velocity that the larger particles settle out. The floatable solids (scum) that rise to the surface are removed by skimmers that scrape this material to the scum box.

General Description of RBC Process

The rotating biological contactor (RBC) treatment system is a biological treatment process which utilizes a concentrated mass of microorganisms to stabilize organic matter in the wastewater. Rather than the organisms being suspended in an aeration basin, as with the activated sludge process, the biological growth is attached to large-diameter corrugated plastic discs mounted on a horizontal shaft.

A series of these shafts are placed in a rectangular tank so that the discs are immersed to approximately 40% of their diameter. The discs are spaced so that, during submergence, wastewater can enter the separations between the corrugated surfaces, providing the microorganisms with a food source. When rotated out of the tank, the liquid trickles out of the plastic media and is replaced by air, providing a source of oxygen to satisfy the respiratory requirement of the microorganisms. The rotation of the discs and the biological activity on them maintains a constant thickness of biologic growth. Growth sloughed from the discs is separated from the flow in the secondary clarifiers.

There 2 secondary clarifiers. Each clarifier is 48 feet in diameter with a side water depth 10 feet.

The secondary clarifiers remove suspended solids and scum present in the effluent from the rotating biological contactor units. The removal of the settleable solids is accomplished by allowing the wastewater to move through the clarifiers at such a reduced velocity that the larger particles settle out. The floatable solids (scum) that rise to the surface are removed by skimmers that scrape this material to the scum box.

Basis of Operation

The belt filter press contains three zones of operation which are the gravity drainage, medium pressure and drum pressure zones. The sludge is increasingly dewatered as it passes through the different zones. The gravity zone provides initial water removal independent of the pressure zones. In the medium pressure zone the sludge passes beneath a heavy rubber "drag blanket" which causes a weighted resistance to the sludge mass. In the final (drum) zone the sludge moves, between two belts, alternately over and under a series of drums which squeeze and flex the belts and the sludge "cake" which is between them. The drums are arranged in size so that the greatest pressure is created just prior to discharge from the belt filter press.

After this process the cake rides on a conveyor belt to the sludge truck.

The purpose of the dewatered sludge truck is to load sludge from the belt filter presses and transport it to the facilities sludge composting facility. The sludge and bulking agents, such as woodchips and sawdust, are combined in the truck mounted compost mixing unit.