18-Env-A6 Solid Waste Engineering and Management · May 2015
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.); Freeze & Cherry, Groundwater; 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.
3.1 Approach. I would combine a records-based generation-rate survey with a direct field composition study. First, generation rates would be established from existing tipping-floor weigh-scale records at the disposal facility, disaggregated by collection route/hauler so tonnage can be attributed back to source category (residential, commercial, institutional, industrial) and expressed per capita or per establishment. Second, waste composition would be determined by a statistically designed load-of-refuse sort following a recognized protocol (e.g., ASTM D5231): randomly select loads stratified by source and by season, hand-sort each sample into standard categories (paper, food waste, yard waste, plastics, metals, glass, other), and weigh each category as a percentage of the sampled load. Sampling would be stratified across at least a full seasonal cycle and across all source types, since both generation rate and composition vary materially between a residential route and a commercial/institutional route.
3.2 Estimating the seasonal factor in 30 days. With no time to directly observe seasonal variation, I would not attempt to re-derive it from scratch; instead I would apply a seasonal-adjustment factor borrowed from an established external source and superimpose it on the 30-day measured baseline. Two practical routes: (i) use the community's own historical weigh-scale billing/tonnage records (even a coarse monthly total, if available, reveals the shape of the community's own seasonal curve, e.g. a summer yard-waste peak) to scale the 30-day sample up or down to an annual-average basis; or (ii) where no local history exists, adopt a published seasonal-peaking factor from a climatically comparable community or from the literature (e.g., a commonly cited summer yard-waste/food-waste peak of roughly 20–40% above the annual mean, tapering to a winter trough), and apply it as a correction factor to the 30-day sample depending on which season it was taken in. Either way, the estimate should be reported explicitly as a seasonally adjusted approximation, not a measured annual average, pending a full-year follow-up study.
