Three odor control chemicals and formaldehyde were tested for detrimental affects on activated sludge using bench-scale bioreactors. Slug fed and continuous flow bioreactors were monitored for changes in suspended solids, specific oxygen uptake rate, sludge settling and compaction, and effluent COD. The biodegradability of dyes and the generation of foam was also measured.

Formaldehyde and the formaldehyde-based odor control chemical "Aqua-Kem" damaged the ability of activated sludge to treat wastewater. They resulted in deceased suspended solids concentrations and increased effluent COD. Formaldehyde hinders the utilization of normal wastewater substrate by activated sludge. The dye in "Aqua-Kem" is not biodegradable, and surfactants in the chemical generate foam.