Examination of mechanisms for odor compound generation during lime stabilization

Lime-stabilized biosolids produced from a wastewater treatment plant often emit odors, especially those described as "fishy" and "decaying". These odors can generate public opposition to biosolids land-application programs even though they represent an environmentally friendly recycling of organic material that is beneficial to the agricultural industry. Therefore, it is critical to examine the controlling factors involved in odor production during the lime stabilization process. Results from preliminary experiments examining added polymer and protein material to dewatered limed biosolids show increased trimethylamine (TMA) production with further increases in 1-hour and 4-hour storage times prior to liming. Further experiments with water-silica slurry reaction media reveal that enzymatically facilitated degradation of polymer and protein is the overriding factor in TMA and dimethyldisulfide (DMDS) production. It is hypothesized that macromolecules such as polymer and proteins in biosolids are first broken down enzymatically, upon which the addition of lime causes TMA and DMDS to be released.