18-Env-A1 Principles of Environmental Engineering · December 2013
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — December 2013 — 04-Env-A1 / Principles of Environmental Engineering. 3 hours duration; closed book with an 8.5×11 in double-sided aid sheet; Casio or Sharp approved calculator only. Any five questions constitute a complete paper (first five answers marked); all seven are solved below for completeness. Each question is worth 20 marks.
Reference texts. Davis & Cornwell, Introduction to Environmental Engineering (6th ed.); Metcalf & Eddy, Wastewater Engineering: Treatment and Resource Recovery (5th ed.); MWH’s Water Treatment: Principles and Design (3rd ed.); Guidelines for Canadian Drinking Water Quality (Health Canada); Canadian Council of Ministers of the Environment (CCME) water-quality guidelines; Canadian Environmental Protection Act, 1999 (CEPA).
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.
Sulphur dioxide (SO₂) from fossil-fuel combustion. Coal- and oil-fired boilers and smelters emit SO₂ to the airshed; it oxidizes in the atmosphere and returns as acid precipitation, acidifying lakes, streams and forest soils (a watershed impact that originates as an air emission). The established engineering solution is a hard one: wet limestone flue-gas desulphurization, which scrubs SO₂ from the stack gas before release and can remove 90–95% of the load.
Particulate-bound heavy metals (e.g., mercury, cadmium) from smelting and combustion. Fine particulates carrying trace metals are emitted to the airshed, deposit onto land and surface water, and bioaccumulate up the aquatic food chain, producing chronic toxicity in fish and, ultimately, in people who eat them. A hard solution is high-efficiency particulate capture (electrostatic precipitators or baghouses); a complementary soft solution is process substitution — switching to a cleaner ore-processing or fuel-blending practice that reduces the trace-metal loading at the source rather than only capturing it downstream.
Thermal pollution of surface water from once-through power-plant cooling. Warm cooling water discharged to a river or lake lowers dissolved oxygen and stresses cold-water fisheries (directly relevant to Q7(i) below). Technology: cooling towers (wet or dry), which reject the waste heat to the atmosphere by evaporative and convective heat transfer instead of to the receiving water, so the plant no longer needs a large thermal discharge at all.
Groundwater contamination from fossil-fuel extraction and ash management. Produced water from oil/gas extraction and leachate from coal-ash impoundments can infiltrate to underlying aquifers. Technology: engineered composite liners with a leachate collection system beneath ash ponds and produced-water storage, whose key principle is hydraulic containment — an impermeable barrier plus a collection layer that keeps the hydraulic gradient directed away from the aquifer and intercepts any leakage before it reaches groundwater.
The pyramid is not the classic expanding-population triangle: its widest section sits in the 35–54 age bands (the post-war “baby-boom” cohort, roughly 1.15–1.25 million per five-year band per sex) while the base (ages 0–14) is narrower, at roughly 0.9–1.05 million per band. That shape — a bulge above the base rather than a broad base — is the signature of a maturing, low-fertility population: birth rates have fallen below replacement, and the demographic weight is shifting upward through the pyramid as the boomer cohort ages.
Two factors that will drive environmental pollution over the next 25 years: (1) the boomer bulge is moving into its highest lifetime energy- and resource-consumption years and then into retirement, so per-capita demand for housing, healthcare and heating/cooling infrastructure rises even without population growth; and (2) as the note states, the population is concentrated in large cities near large water bodies, so growth in energy demand is spatially concentrated, straining urban generation, transmission and water-cooling infrastructure exactly where receiving waters and airsheds are already most loaded.
Two engineering measures for 25-year energy sustainability: (1) expand low-carbon generation (hydro, wind, nuclear refurbishment) with transmission upgrades sized to the concentrated urban demand centres identified above, reducing the fossil share serving the largest population clusters; and (2) a demand-side retrofit and cogeneration program targeting the aging urban building stock (insulation, high-efficiency HVAC, district energy/cogeneration), which offsets the rising per-capita demand from an aging, urbanized population without requiring proportional new generation capacity.
