Kalinichenko K. Bioextraction of heavy metals from colloidal sludge systems with their utilization

A new biocolloidal process of heavy metals extraction from the sludge solids is worked out, it includes enhancing vital ability of heterotrophic microorganisms by introducing easily metabolized nutrient substrates, synthesis of metabolites with the properties of heavy metals extractants and flocculants, biocolloids sedimentation, separation of the sludge suspension into solid and liquid (bioextract) phases and obtaining biomineral fertilizer with immobilized bioelements as sludge depot and bioextract included in the hydrogel matrix. The efficiency of heavy metals removal from colloidal sludge in bioextraction process with heterotrophic and chemotrophic (sulphur oxidizing) microorganisms and chemical extraction was compared. The advantages of metals bioleaching process at heterotrophic metabolism is shown. The efficacy of heavy metals removing from sludge varied from 80 % (Zn) to 15 % (Cr) and follow the order: Zn > Mn > Cu > Ni > Cd > Pb > > Cr. The changing in colloid-chemical properties of natural sludge system in the processes of heavy metals leaching under the action of metabolizing microorganisms is studied. It is established that under metals bioleaching with heterotrophes participation sludge colloids hydrophobization and their negative charge reducing occur. The leaching of heavy metals leads to destabilization of the sludge suspension, maximal in biological processes. The optimal conditions for detoxification, flocculation and sedimentation of sludge colloids are identified. The efficiency of the biomineral fertilizers obtained in vegetation experiments is demonstrated.