Municipal (Sanitary) Wastewater Odor Control in Biosolids Dewatering

Sulfides and other organic and inorganic compounds can form in the biosolids handling operation of a wastewater system due to anaerobic conditions. These gases can be released during the dewatering step causing the rotten egg odor that is created by toxic hydrogen sulfide and other sewage related compounds. Sulfides can react with moisture in the atmosphere to form acids, which will corrode equipment. Aqueous solutions of permanganate help eliminate wastewater odor caused by hydrogen sulfide, mercaptans, amines, and other organic nitrogen and sulfur based compounds and prevent the formation of corrosive acids. The result is a safe, odor-free environment that minimizes corrosion due to sulfides. Permanganate will not oxidize ammonia.

In the treatment of sanitary sewage, biosolids are separated from the liquid. These biosolids are concentrated and dewatered using filter presses, centrifuges, or other devices. Hydrogen sulfide is released during the dewatering operation.

Hydrogen sulfide measurements are made around the dewatering equipment. Permanganate (1% to 20% solution) is then applied at a convenient point either into the biosolids holding tank or directly ahead of the solids transfer pumps. The reaction with sulfides is immediate. Feed rates are adjusted to adapt to changing conditions such as flow and temperature. The direct injection of aqueous potassium permanganate solutions into the wastewater biosolids eliminates odors except ammonia.

For each part of sulfide, 4-6 parts of permanganate is required. For wastewater odor control of biosolids, testing usually starts at 100 ppm KMnO4 (10 lbs. per dry ton). The dosage is normally reduced to 5 to 8 lbs. KMnO4 per dry ton after the system is stabilized.

To effectively introduce permanganate into the system, proper feed equipment is necessary and available from Carus. No other changes are needed. Operators should be properly trained to handle permanganate and be aware of safety and emergency procedure.

Permanganate reacts rapidly with the functional groups of the odorous compounds, destroying the wastewater odor without having to fully mineralize (degrade) the compound. Dewatering improvements have been shown when permanganate is added to septic biosolids to eliminate hydrogen sulfide. In some cases, the reduction in polymer is dramatic and offsets the cost of permanganate addition. Employees are no longer subjected to toxic hydrogen sulfide and neighbor complaints about wastewater odor are reduced or completely eliminated.

Pisarczyk, K. S., Rossi, L. A., Sludge Odor Control and Improved Dewatering with Potassium Permanganate, 55th Annual Conference of the Water Pollution Control Federation, St. Louis, Mo. (Oct 1982). Carus Form CX #4005

Ficek, K. J., Potassium Permanganate Controls Sewage Odors, (1980). Carus Form CX #4007

Staff, Permanganate Treatment Brings Odor Control Success, WATER/Engineering and Management. Carus Form CX #4009

Pope, R. J. , Weber, R. A., Odor Control With Chemicals, Operations Forum, Vol.11, No. 4, (April 1994). Carus Form CX #3760

Carus Corporation, the CAIROX® Solution System. Carus Form CX #4900 (1997)