Possible Applications

The biofilter at Hyperion Treatment Plant using HD Q-PAC^® will be scaled up to pretreat large volumes of exhaust air which is now being processed by conventional wet scrubbers.

Wastewater treatment plants in urban areas are among the world''s largest consumers of sodium hypochlorite.

By removing 90% or more of the H₂S using atmospheric oxygen, the operating cost of chemical oxidants for the scrubbers can be cut by hundreds of thousands of dollars per year. The existing scrubbers will continue to function as a "polishing" stage, and as a back-up in case of any problems with the trickling biofilters.

These biofilters are particularly well suited for odor control at isolated pumping stations and other facilities where there is no-one to operate a conventional wet scrubber, even if a water system could afford the equipment and the chemicals needed to scrub small air streams at many scattered locations. These filters are simple enough to run automatically without operator attention, and with no need to store hazardous chemicals at multiple unguarded sites.

In many developing countries, the capital and operating costs of wet scrubbers are more than treatment plant budgets can bear. The simplicity of trickling biofilters, and their ability to operate without expensive chemicals, provide a badly needed alternative in this situation.

Trickling biofilters may also find use as simple pretreatment stages for conventional biofilters for VOC removal. They can humidify air and greatly reduce its sulfur content, extending the useful life of water-absorbent biofilter media while eliminating the need for treatment chemicals.

References

1.Bohn, H., "Soil and compost filters for malodorous gases," J. Air Pollution Control Assoc. 25, p.953 (1975).

2. Ottengraf, S. and Van Den Oever, A., "Kinetics of organic compound removal from waste gases with a biological filter," Biotechnol. Bioeng., 25, p. 3089, (1983)

3. Devinny, J., Deshuesses, M., Webster, T., "Biofiltration for Air Pollution Control," Lewis Publishers, Boca Raton, p. 74, (1999).

4. Lutz, M. and Farmer, G., "Pulling double duty: A Colorado plant''s trickling filters treat odor while reducing wastewater nitrogen content," Water Environment Federation Operations Forum, 16 (7), pp.10-17 (1999)

5. Steve Johnson, Hyperion Wastewater Treatment Plant, Los Angeles, California (personal communication)

6. Devinny, J., Deshuesses, M., Webster, T., "Biofiltration for Air Pollution Control," Lewis Publishers, Boca Raton, p. 9, (1999).