Reducing Generation Of Biogenic Hydrogen Sulfide In Wastewaters

By Dr. Rakesh Govind

Lagoons, also known as stabilization ponds, are earthen facilities for the biological treatment of wastewater. Lagoons are designed to remove Biochemical Oxygen Demand (BOD) and to reduce the concentration of disease causing organisms. Large lagoons have been known to generate hydrogen sulfide odors even with extensive aeration, mainly because of inadequate dissolved oxygen dispersion in the water. Another major issue with lagoons is inadequate mixing in the water to allow adequate dissolved oxygen dispersion.

Problems associated with lagoons are:

• Odor, mainly ammonia and/or hydrogen sulfide;
• Sludge build-up, requiring periodic dredging and solids removal; and
• Inadequate water discharge quality, in terms of total nitrogen, ammonia, fecal coliforms count, and phosphorus concentration

Conventional methods that have been tried with limited success includes the use of biocides (Hodges and Hanlon, 1991), which are added to the water to reduce bacterial growth. The main reason for limited success is the dissipation of biocide in reducing growth of all bacteria – aerobic, anaerobic, sulfate reducing, etc., some of which are needed for biological treatment of the water. The sulfate reducing bacteria (SRBs) responsible for generation of biogenic sulfide and hydrogen sulfide mainly reside within biofilms in the sediment, and most biocides are unable to penetrate and kill these robust biofilms (Hamilton, 1985). Another approach is aeration of the water or use oxidants to oxygenate the water, which reduces the effectiveness of SRBs.

However, aeration of water is expensive and results in increased emissions of hydrogen sulfide initially as it strips the dissolved gas from the water.