Do biosolids have an odour?
The last stage of treatment at the wastewater treatment plant, which produces the biosolids, takes place under anaerobic (without air) conditions. This produces traces of odorous gases. This process is quickly halted once the biosolids are placed in the aerobic (with air) conditions in the field. Furthermore, injecting the biosolids directly into the soil, below the surface, further ensures minimal field odours.
Biosolids may have their own distinctive odour depending on the type of treatment it has been through. Some biosolids have a stronger odour that may be offensive to some people while most biosolids have a slight musty, ammonia odour. Sulphur and ammonia compounds (both plant nutrients) in biosolids are normally the cause of these odours. Typically odours are reduced after the biosolids have been applied and incorporating into the topsoil.
