Three clean products from co-mingled waste using a novel hydrodynamic separator

Abstract

Mixed municipal solid waste currently landfilled contains a high percentage of packaging glass, varying from 33% to 80% by weight according to several sample characterizations, due to the lack of high throughput separation technology. The hydrodynamic separator proposed is a closed-loop device developed to separate co-mingled waste into plastics, glass and other dense particles and organic sludge. The glass and other dense material stream is cleaned by the system, permitting efficient downstream optical sorting to take out metals and ceramics and, if required, glass sorted by colour. The plastics and the organic sludge are separate, processable waste streams. As the solid waste is introduced in the separator, the action of water jets located on the ramps of a fixed sinusoidal-shape bottom and the presence of hydrofoils at the upper part of the tank produce a flow pattern that lead plastics towards its collection point on the surface, while glass and ceramics are settled to the bottom of the tank and transported to the extraction point. Organics and other fine particles are obtained from lamellas, before reintroducing the clarified fluid into the flow loop. The sludge obtained from this process is suitable for feedstock to Anaerobic Digestion processes. In the present paper the equipment and the methodology is described and the physical principles of the separation process are explained. Results from a full scale trial designed to process 9.7 tonnes per hour at a municipal UK waste site operating in Nov 2015 – Feb 2016 are presented.