18-Env-A6 Solid Waste Engineering and Management · May 2016
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.
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.
(1) Moisture content — the single most influential operating variable; generation rate rises markedly as moisture approaches field capacity. (2) Waste composition — the proportion of readily, moderately and slowly biodegradable organic material present. (3) Temperature — controls the metabolic rate of the methanogenic consortium. (4) pH — methanogens are sensitive to pH and operate best near neutral (roughly 6.8–7.2); accumulation of volatile fatty acids during the initial acid phase can depress pH enough to inhibit methanogenesis until buffering capacity develops. (5) Particle size — smaller particles present more surface area to microbial attack, accelerating hydrolysis and gas generation. (6) Oxygen availability (redox condition) — methanogenesis requires strict anaerobic conditions; oxygen intrusion from a poorly sealed cover or shallow placement inhibits the methane-forming population and can shift the zone toward aerobic decomposition instead.
