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‘Biosolids’ is a generic name for several types of biological waste, the main ones being municipal waste water sludge and residues from agriculture and foodstuff industry. Although generated as waste, biosolids contain valuable organic matter. Large volumes of these materials are therefore reused in agriculture, forestry and landscaping, in full alignment with the European Circular Economy concept. Stabilization and hygienization are compulsory for biosolids, prior to their reuse. Liming is a proven and highly effective process to stabilize and hygienize biosolids.
Biological sludge is an inevitable result of municipal waste water treatment, as prescribed by European legislation. The biological sludge is thickened and dewatered in the waste water plant, but this sludge cannot be reused directly due to:
- Bio-degradability resulting in odour generation and organic acids release (biological sludge stabilization is not standard in all waste water plants).
- Presence of pathogens harmful for human health and environment.
Untreated animal by-products have similar hazardous properties.
Biological stabilization and hygienization are the minimum treatment steps required to enable safe reuse of biosolids in agriculture or similar branches.
Lime can provide multiple effects in biosolids treatment:
- Flocculation of liquid sludge by the common effect of lime and iron or aluminium salts; therefore it is widely used to intensify the dewatering processes.
- Efficiency increase in most types of dewatering equipment, thanks to lime’s mineral load effect.
- Pathogens devitalizing, thanks to exothermic quicklime hydration.
- Long-term odour reduction, thanks to high pH, thus keeping odour substances in a dissociated form.
Carmeuse developed the BioCalco® product range to match the main processes in biosolids treatment.