Case Study: Municipal Wastewater Treatment – Biosolids Odor Control

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INTRODUCTION:

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.

INVESTIGATION:

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.

IMPLEMENTATION:

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.

RESULTS:

Neighbor complaints of nuisance odors have been eliminated.