Solving the Hydrogen Sulfide Odor Problem

Oxygenation assists aerobic and facultative anaerobic bacteria to reproduce faster than anaerobes, thus out-competing them for nutrients. 

Hydrogen Peroxide
Hydrogen peroxide has been injected, upstream of the headworks or primary clarifiers, to react with hydrogen sulfide forming sulfur and water. Excess hydrogen peroxide decomposes to release oxygen and water, thereby increasing the dissolved oxygen in the stream. Generally 90% of the reaction between hydrogen peroxide and hydrogen sulfide takes place within 10 to 15 minutes, with the balance reacting in an additional 20 to 30 minutes.

Disadvantages: For small installations, 500 lb. drums are purchased. Larger installations buy in tank-trucks or tank-cars. Special safety handling including protective clothing, face shields must be worn during bulk storage loading, and repair and maintenance of the facility. Spontaneous combustion is another possible problem. 

Chlorine has been applied to wastewater in a dose that is at least three to nine times the concentration of sulfide to be oxidized. Chlorine combines with water to form hypochlorous and hydrochloric acids.

Disadvantages: Chlorine kills the natural (and Clear-Flo®) waste-degrading bacteria. Chlorine combines with the urine in the waste stream to form chloramines, which are difficult to remove. Toxic or carcinogenic chlorinated hydrocarbons may form during treatment. Chlorine is a hazardous material, requiring special safety precautions.

By reacting certain metal salts, such as ferrous sulfate, with hydrogen sulfide, an insoluble metallic sulfide will be formed. The dose is 4.5 grams of ferrous sulfate for each gram of sulfide to be oxidized. This is less expensive than peroxide or chlorine.

Disadvantages: These products may contain a high free acid content which causes detrimental changes in the pH and alkalinity of the stream, which can interfere with biodegradation of the waste.

Potassium permanganate is a strong oxidizing agent that can react with hydrogen sulfide in a variety of ways, depending on whether the stream is acidic or alkaline. In acidic conditions, the following reaction takes place: 

Under conditions that are in between acidic and alkaline pHs, a variety of reactions occur, yielding elemental sulfur, sulfate, thionates, dithionates and manganese sulfide end products. Potassium permanganate has been fairly effective when added to the sludge dewatering operation, where it is added to the suction side of the sludge pumps feeding the dewatering unit.

Disadvantages: Dosages are difficult to predict and control in most liquid applications. The high cost and high dose, 6 or 7 parts of potassium permanganate are needed for each part of hydrogen sulfide, are discouraging. Safety precautions are required for handling and storage.