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Process of Biosolids

  1. The Saint Peter Wastewater Treatment Facility processes biosolids in a "Class A exceptional quality" by first pumping in liquid form at two percent solid, from the clarifiers to a sludge storage tank
  2. From there, biosolids are pumped to the belt filter presses, which squeeze the water from the liquid biosolids to produce a “cake” that is 25 to 30 percent solid material.
  3. The cake then travels by conveyor to the lime-heat treatment system, where lime is added to the cake to raise the temperature to 150 degrees Fahrenheit.
  4. After that temperature has been maintained for a minimum of 30 minutes, the cake is dropped to another conveyor that transports it to a storage bunker for finished biosolids.
  5. The finished biosolids are 40 to 45 percent dry solid and the bunker where they are stored can hold up to 180 days of biosolids production.
  6. After being processed the final material is classified as a deregulated "Class A exceptional quality" biosolid that can be easily disposed to agricultural land where it is used as fertilizer because it contains many nutrients that are beneficial for soil conservation and recycling.