18-Env-A6 Solid Waste Engineering and Management · December 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.); 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.
The goal of a waste characterization study is to establish a statistically defensible, quantitative picture of a community's waste stream — its generation rate, physical composition by category, and relevant physical/chemical properties — so that downstream planning decisions (collection system design, MRF or composting facility sizing, landfill capacity/life projections, diversion-program targets) rest on measured local data rather than generic literature values.
The major steps are: (1) define the study's objectives and the generator categories/geographic area to be covered; (2) design the sampling plan — sample size, sampling frequency/duration (accounting for seasonal variation, see Question 2), and the source(s) from which samples will be drawn (curbside set-outs, transfer-station loads, disposal-facility loads); (3) conduct the field sampling and sorting, following a standard protocol (e.g. ASTM D5231) to hand-sort weighed samples into consistent waste categories; (4) collect supporting quantitative data — total tonnage from scale-house records, moisture content, density measurements; (5) analyze the data statistically (means, standard deviations, confidence intervals) to characterize both the central tendency and the variability of the waste stream; and (6) document and report the findings, including recommendations for how the data should be used and how often the characterization should be refreshed.
A well-executed characterization study is what separates a design built on defensible, site-specific evidence from one built on assumed literature averages, and a professional engineer relying on the latter without disclosure risks a design that under- or over-performs once the facility is operating against the community's actual, rather than assumed, waste stream. The scope and cost of the study itself should be proportioned to the decision it supports: a preliminary planning estimate can lean more heavily on regional literature values, while a facility's final design-basis figures warrant the full local sampling program described above.
