The present invention relates to a flocculant based gelation - solidification - disinfection system for treatment of biomedical waste. Particularly, the present invention relates to the process for preparation of disinfecting composition comprising of a selected nanomaterial as its sol in water and a poly-amino acid containing a basifying agent, which when subjected to mixing with solid or fluid waste samples at a defined volumetric and/or weighted composition leads to instantaneous flocculation / gelation / solidification with >99.9% microbial disinfection. More particularly, the present invention relates to a disinfecting device for treatment of biomedical waste.