One hundred forty miles of sewer main varying from 8 inches to 60 inches in diameter, collect wastewater from approximately 40,000 customers and transport it to the Board of Public Utilities (BPU’s) Wastewater Treatment Plant (WWTP) on Quaint road in Falconer, NY.
How Wastewater Treatment Works
By the time your waste reaches the treatment plant, it is not recognized as the waste you ground up in your garbage disposal or flushed down your toilet. The action of the waste being washed through mains breaks it up into tiny particles which are suspended in the water.
Mechanically operated bar screens remove large objects and debris which may plug downstream piping and equipment. Some examples of items captured in the bar screens are sticks, small rocks, and occasionally small children’s toys and dentures.
The wastewater then passes through the grit removal system, which removes any sand, stone chips, and cinders that may damage pumps.
Primary clarifiers remove coarse solids by settling and removing floating solids, oil and grease by skimming. Sludge that settles to the bottom is pumped to thickeners. WWTP personnel skim the floating solids off the tank into a trough which goes into a bin for removal offsite.
After passing through the clarifiers, the wastewater enters the trickling filter process. Wastewater is pumped underground beneath two trickling filters and up through a central 18 foot rotating column through spray arms extending from the center column. The wastewater is sprayed over plastic media, which is 16 feet deep and is enclosed by a circular wall. Water pressure causes the arms to move so wastewater is continuously sprayed onto the media. As the water trickles down through the plastic media, natural-occurring microscopic organisms that have attached themselves to the plastic media, eat the organic materials left in the wastewater. As the organisms die off they are washed off and carried away to the next treatment process.
Secondary clarifiers remove solids produced in the trickling filter process by settling.
The wastewater then goes through the final clarifiers for additional settling and removal of solids before going through the rapid sand filters. The sand beds filter out particles as the water passes through the sand. As the beds fill up and reach capacity, a travelling bridge moves over the surface and vacuums the particles away from the sand. Chlorine is added at this treatment stage to disinfect the water before it goes through chlorine contact tanks, which give more time for the chlorine to treat the water. Sodium Bisulfite is added at this stage to remove any chlorine still present in the water before it is discharged into Cassadaga Creek.
The solids collected throughout the plant processes go to the thickeners, where the sludge volume is reduced by settling and decanting.
Thickened sludge is fed to anaerobic digestion tanks for stabilization. Anaerobic digestion is a biological decomposition process that occurs in closed, heated and mixed tanks. This process reduces the volume of sludge, creates methane gas and renders the material more conducive to dewatering.
Methane Generates Electricity
Methane produced from the digestion process is utilized in a micro-turbine which generates electricity to offset electrical needs at the WWTP. A methane boiler utilizes methane to produce heat for buildings and helps to heat the digesters.
Two belt-type filter presses dewater the stabilized sludge from the digesters. The sludge is conditioned with polymer to separate the water from the sludge before it reaches the press units. The presses squeeze water out of the sludge before it is dropped into bins and taken to the landfill for disposal.