Eliminating pathogens in biosolids by alkaline stabilization

The Cañaveralejo wastewater treatment plant (PTAR-C) based in Cali-Colombia, produces almost 100 t-day-1 of biosolids. Although do not have heavy metals restrictions, it is class B for high contents of pathogens microorganisms and parasites. The alkali stabilization was done with a 9% of dose (w/w) of quicklime and hydrated lime applied to different 0.5 ton piles of wet biosolids (66.5% humidity) and dry biosolids an environmental temperature (25-31°C) for 72 hours (50.1% humidity). The experiment had a completely randomized design and it was composed by 6 treatments with their respective duplicated. With the alkali stabilization, the pH increments above 12 units during enough time to assure pathogens and parasites reduction in order to achieve a class A material level. On the other hand, the dry biosolids facilitate the conditions for lumps formation that reduce the homogenization of the substrate with the alkali material, which it is and undesirable factor for pathogen reduction.