The Upper Blackstone wastewater treatment facility provides
advanced wastewater treatment using biological nutrient removal (BNR). The solids that are removed during treatment
are managed using incineration. The
sterile ash that is generated is landfilled, and the air emissions are treated
to stringent standards. Click on the PROCESS TITLES for further
details.
PRELIMINARY TREATMENT PRIMARY TREATMENT BIOLOGICAL
NUTRIENT REMOVAL SYSTEM DISINFECTION
(ACTIVATED SLUDGE)
SLUDGE THICKENING AND DEWATERING SLUDGE COMBUSTION AIR POLLUTION CONTROL SYSTEM
Mechanically Cleaned Bar Screens remove large objects such as rocks, metal objects
and other material that could either clog or damage downstream equipment.
Aerated Grit Chambers remove grit and freshen
raw wastewater by bubbling air
through the wastes helping separate dense materials such as sand from the
lighter organic matter. Grit that is relatively free of organic material is
removed and landfilled
Parshall Flume measures flow.
Primary Clarifiers remove approximately half of the suspended solids
(SS) and 30 percent of organic material from raw wastewater by settling. The material settles to the tank bottom, and
the resulting sludge is pumped to holding tanks. Grease, oil and other floating matter (scum)
are skimmed from the water surface and pumped to holding tanks.
Biological Nutrient Removal System
removes such contaminants as fine solids, organic
material, ammonia, phosphorus, and dissolved metals. The system includes bio-reactors and final
settling tanks.
Bio-reactors provide an environment in which a living organisms,
including bacteria and plankton (termed activated sludge) remove pollutants
from the wastewater by feeding upon the organic matter and by absorption. Mechanical mixers and air diffusers provide
the necessary oxygen to maintain the organisms and the process.
Final Settling Tanks allow the activated sludge formed in the
bio-reactors to settle, removing the material from the treated water prior to
further treatment. Most of the settled
sludge is then returned to the aeration tanks by sludge recirculation pumps,
and a portion is wasted to flotation thickeners for further treatment.
Chlorine Contact Tanks provide sufficient detention time for the
treated wastewater to be disinfected using sodium hypochlorite. Following disinfection, the treated effluent
is dechlorinated using sodium bisulfite prior to discharge into the
Flotation Thickeners reduce the water content of waste activated
sludge (from the final settling tanks) concentrating it for further
processing. In this operation, dissolved
air flotation enhanced by polymer addition thickens the sludge while excess
liquid is returned to the liquid process for treatment.
Sludge Holding Tanks provide storage and blending for the thickened waste activated sludge,
primary sludge, imported sludges, and scum before
further processing.
Belt Filter Presses further reduce the water content of sludge so that it may be
efficiently burned, forming a cake of 20 to 25 percent solids. Polymers are also used here to enhance
process performance. Excess liquids are
returned to the liquid process for treatment.
COMBUSTION
Multiple Hearth Furnaces thermally reduce the filter cake to an inert
ash, which is then disposed of at our on-site landfill. Excess heat from this system is used for
building heat.
The contaminants in the
exhaust from the multiple hearth furnaces are removed in an air pollution
control system. The system is a state of
the art process in which particulate matter, acid gasses, metals, and volatile
organic compounds are either removed from the gas stream or thermally
destroyed.
Venturi Scrubber removes some particulate matter and volatile
metals by liquid contact and condensation.
Tray Scrubber removes acid gasses and additional metals by liquid contact,
absorption and chemical neutralization in a caustic spray system.
Wet Electrostatic Precipitator removes
additional amounts of fine particulate matter and associated metals not removed
in the venturi scrubber by liquid contact and condensation enhanced by
electrostatic precipitation.
Regenerative Thermal Oxidizer (RTO) thermally converts volatile organic compounds to
carbon dioxide by combustion of gasses at 1,400 degrees Fahrenheit (F).
Stack assures dispersion of off gasses by discharge through 125-foot
high exhaust stack.
Other plant facilities
Chemical Storage & Feed Building provides for safe receipt and storage of liquid
sodium hypochlorite and sodium bisulfate.
Plant Water Building houses pumps for the plant water supply.
Maintenance Building & Annex house the machine shop, parts storage, garage space, a lunchroom, a locker and
shower room, and offices for maintenance personnel.
Administration Building houses the administrative, laboratory and
engineering staff, the laboratory and the board room.
Standby Power Generators provide
emergency power to operate preliminary treatment and disinfection in case of a
power failure.