18-Env-A6 Solid Waste Engineering and Management · December 2013
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Reference texts: Tchobanoglous, Theisen & Vigil, Integrated Solid Waste Management: Engineering Principles and Management Issues; Freeze & Cherry, Groundwater (Darcy's Law, vadose zone); CCME, Guidance Document on Landfill Gas Management; EGBC/Engineers Canada 04-Env-A6/18-Env-A6 examination syllabus.
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Incoming mixed municipal solid waste is first weighed and dumped at the receiving/tipping floor, where a manual pre-sort removes bulky or hazardous items and easily hand-picked recyclables that would otherwise damage downstream equipment. The remaining material passes through a shredder for size reduction, exposing and liberating individual material types so mechanical separators can act on them. A magnetic separator then pulls out ferrous metal, followed by an eddy-current separator, which induces circulating currents in non-ferrous conductors (chiefly aluminum) to eject them without attracting steel. A trommel screen (rotating cylindrical screen) next splits the stream by size: undersize material (glass, grit, fine organics) drops through the screen for separate recovery or disposal, while oversize combustible material passes on to an air classifier, which uses an air stream to split it further into a light fraction (paper, plastic, textiles) suitable as refuse-derived fuel (RDF) for waste-to-energy combustion, and a heavy fraction of non-recoverable residue sent to landfill. This staged sequence — size reduction, then progressively finer physical/magnetic/aerodynamic separation — is the essential architecture common to virtually all mixed-waste resource recovery plants, whatever the specific equipment selected at each stage.
