18-Env-A6 Solid Waste Engineering and Management · December 2014
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; Vesilind, Worrell & Reinhart, Solid Waste Engineering; Davis & Cornwell, Introduction to Environmental Engineering (6th ed.); CCME, Guidance Document on Landfill Gas Management; Canadian Environmental Protection Act, 1999.
This paper prints marks IN FRONT of the question number on every line (e.g. "5 1. What are the elements…", "4 16. All 29 questions are answered in full.
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.
Size reduction (shredding, grinding, hammer-milling) reduces MSW to a more uniform particle size, which: produces a more homogeneous feedstock for downstream mechanical separation, composting or combustion; increases bulk density (aiding transport and landfilling efficiency); increases surface area, accelerating biological (composting) and thermal (combustion) reaction rates; and liberates bound/composite materials (e.g. metal fasteners from bulky items) so subsequent magnetic or air-classification separation can recover them. Because nearly every downstream unit operation performs better on a uniform, liberated feed than on raw, bulky, mixed MSW, size reduction is almost always installed as the first mechanical step in a materials recovery facility or waste-to-energy plant.
