Review of the effects of wastewater biosolids stabilization processes on odor emissions

Odor emissions from biosolids limit opportunities for their beneficial reuse by land application. Odorous emissions are affected by the operation of stabilization processes via methods such as anaerobic digestion, aerobic digestion, alkaline treatment, thermal drying, or composting. Commonly used sampling and measurement methods for assessing odor emissions were identified and key odorants reported for biosolids produced using different stabilization methods. Generally, dominant odorants from biosolids were volatile sulfur compounds; however other odorants such as trimethylamine, ammonia, indole, p-cresol and pinene may also be sensorially important in different types of stabilized biosolids. Therefore, initial studies should target a range of odorants potentially emitted at different sites. The use of sensory analysis, which was limited in many studies, coupled with analytical methods can be effectively used to characterize nuisance emissions. The processing of the biosolids both before and after stabilization was shown in many studies to affect the resultant biosolids odorous emissions. These findings suggest that not only should the operational performance of biosolids processing before, during and after stabilization should be reported but that the biosolids management systems should consider the whole biosolids processing train, rather than just the operation of the chosen stabilization method.