Compounds contributing to odors from pulp and paper mill biosolids - Anaerobic biological activity a contributing cause

Compounds contributing to the manure-type odors associated with biosolids processing and dewatering in pulp and paper mills were identified as several volatile fatty acids (propanoic, isobutyric, butyric, isovaleric and valeric), a phenol (p-cresol), indole, 3-methyl indolc (skatole) and the four reduced sulphur gases: hydrogen sulphide, methyl mercaptan, dimethylsulphide and dimethyldisulphide. A Preliminary study of the concentrations of these odor-causing components at three mills indicates that they appear to be present at relatively low concentrations in the ambient air of the biosolids processing areas, well below literature threshold limit values (TLV). Nevertheless, the odors can be a nuisance and options need to be evaluated for their potential control.