Impact of Lime Dose and Mixing Quality on Odor Generation by Lime-Stabilized Biosolids

Odor generated from lime-stabilized biosolids with various lime doses and mixing regimes was studied during two bench scale experiments over four weeks of storage to determine the correlation between the lime stabilization process and odor strength. For the first bench scale experiment, dewatered solids were mixed with various lime doses (4.5% and 11.7% by wet weight) under various mixing conditions (poorly mixed and thoroughly mixed). For the second bench scale experiment, odors generated by various lime doses that were thoroughly incorporated were analyzed.The bench study indicates the various roles of lime dose and mixing quality on odor generation over time. During the initial week of storage, lime dose was more important than mixing quality. A low lime dose had a weaker odor strength (lower dilution-to-threshold) and less offensive odor (more neutral hedonic tone) than a high lime dose. However, mixing quality became more important over the course of time. A well-mixed biosolid product had weaker odor strength (lower dilution-tothreshold) than a poorly mixed product. The well-mixed biosolid product also had a relatively stable hedonic tone whereas the poorly mixed products became increasingly more offensive over time.