18-Env-A6 Solid Waste Engineering and Management · May 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.
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) An adequate biodegradable organic substrate as the carbon/energy source for the microbial population. (2) Sufficient moisture (typically 40–60% by weight) to support microbial metabolism without excluding oxygen from the pore spaces. (3) An oxygen supply to sustain aerobic decomposition, provided by turning or forced/passive aeration. (4) A viable, balanced microbial population (naturally present on the feedstock) with a favourable carbon-to-nitrogen ratio (roughly 25–30:1) to support efficient, odour-free decomposition. Without all four present together the process either stalls (no substrate, no oxygen), proceeds too slowly to be practical (moisture or nutrient-limited), or goes anaerobic and produces odour and leachate rather than a stabilized, marketable compost product — so a site assessment before start-up should confirm each is achievable with the intended feedstock and equipment.
