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Case Study: Municipal Wastewater Treatment – Biosolids Odor Control


A 75 MGD U.S. water reclamation plant serves a city of 400,000 population. The treatment process stabilizes biosolids in 4 anaerobic digesters. After years of use, the lids on two of the digesters collapse forcing emergency repairs.


In order to repair the digester lids, an outside contractor is hired to remove and dewater the biosolids using two belt presses. The presses are located outside, near the digesters.

  • The digesters contain biosolids of 7-11 %. The solids are diluted with water and pressed at a rate of 300 gallons per minute.
  • The solids are dewatered for 12 hour/day, 5 days/week.
  • High sulfide levels are released during dewatering, generating odor complaints.


975 - UNITED CARUSOL® Liquid Permanganate is added into the dilution water, treating the biosolids as they are pumped to the belt presses.

  • The metering pumps are set to 5 gph - an average dosage is 100 mg/L, as permanganate.
  • After 1-hour, the staff reports that odors are significantly lower.


Neighbor complaints of nuisance odors have been eliminated.