Biosolids are a nutrient-rich, organic byproduct of the wastewater treatment process. They are formed from stabilized municipal sludge and are suitable for beneficial recycling. This fact sheet explains how biosolids are produced and what they contain. Here, municipal sludge is separated from the wastewater during primary and secondary treatment. What's in sewage sludge depends largely on the location and population of the community that produces it.
Wastewater is comprised mostly of human waste, which contains bacteria and viruses.
It also contains varying concentrations of industrial and household hazardous waste. Anaerobic digestion stabilizes the sludge and destroys many disease-causing organisms, reduces volume and odour. Biosolids possess an earthy odour that is, to some people, less offensive than raw animal manure. For this reason,, control measures such as incorporating biosolids into the soil can minimize odours at land application sites. Effective odour management will help build a biosolids program that is continuous and successful.