16-Civ-A3 Elementary Environmental Engineering · December 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Paper format. National Exams, December 2014 — 98-Civ-A3 Environmental Engineering. Three hours, closed book with one candidate-prepared double-sided aid sheet. Seven problems, each worth 20 marks; any five constitute a complete paper (maximum 100 marks), and only the first five answers in the work book are marked. All seven problems are solved below, because the set is a study resource rather than an exam attempt.
Reference texts. Davis & Cornwell, Introduction to Environmental Engineering; Mihelcic & Zimmerman, Environmental Engineering: Fundamentals, Sustainability, Design; Metcalf & Eddy, Wastewater Engineering: Treatment and Resource Recovery; Crittenden et al. (MWH), Water Treatment: Principles and Design; CCME Canadian Environmental Quality Guidelines; Impact Assessment Agency of Canada, Impact Assessment Act guidance.
Check: two source inconsistencies are carried through deliberately. (1) Problem 1(i) prints the dipropylene glycol formula as C6H14O2 (118.2 g/mol); the actual compound is C6H14O3 (134.2 g/mol). (2) The same sentence states the dose as “76 kg (1000 mol)”, which implies a molar mass of 76 g/mol and matches neither formula — 1000 mol of the real compound is 134 kg. The mole quantity is the load-bearing datum for a closed-system balance, so 1000 mol is adopted and both molar masses are reported where a mass concentration is asked for. NOTE 1 on page 1 expressly invites this kind of stated assumption.
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 matrix below carries the answer; each cell gives two impacts followed by the two corresponding engineering solutions, and the discussion after it draws out the cross-cutting themes the marking scheme rewards.
| 2 Impacts & 2 Solutions | (a) Urban expansion and intensification | (b) Increasing energy use per capita | (c) Industrial park intensification |
|---|---|---|---|
| Atmospheric emissions | Impacts: traffic-driven NOx and fine particulate from longer commutes and congestion, producing ground-level ozone and elevated PM2.5; the urban heat island, which raises cooling demand and accelerates photochemical smog formation. Solutions: transit-oriented density with electrified rapid transit and active-transport networks that cut vehicle-kilometres travelled; a green-infrastructure programme of urban tree canopy, cool and reflective roofs and permeable surfaces to suppress the heat island. | Impacts: higher combustion-derived greenhouse gas and criteria pollutant loading per person; regional acid deposition and mercury from fossil generation. Solutions: demand-side management — stringent building energy codes, envelope retrofits, heat pumps and district energy — which is the cheapest tonne of abatement available; supply-side decarbonisation to hydro, wind and solar with flue-gas desulphurisation and selective catalytic reduction retained on any remaining thermal plant. | Impacts: concentrated point-source emissions of air toxics and volatile organics from process vents and fugitive leaks; cumulative effects where many facilities share one airshed, so each permit is met yet the ambient standard is exceeded. Solutions: best-available-technology controls at source — regenerative thermal oxidisers, vapour recovery, leak detection and repair programmes; airshed-scale cumulative-effects modelling with a facility emissions cap and a shared continuous ambient monitoring network. |
| Water and wastewater infrastructure | Impacts: increased impervious cover raising peak stormwater flows, channel erosion and first-flush pollutant washoff; combined and sanitary sewer overflows as intensification outstrips legacy collection capacity. Solutions: low-impact development — bioswales, rain gardens, permeable pavement and green roofs — to restore predevelopment hydrology at source; sewer separation and real-time control with equalisation storage, staged against a hydraulic model of the existing system. | Impacts: large thermal-plant cooling-water withdrawals with entrainment and thermal discharge; the substantial energy embedded in water and wastewater service itself, often the largest single item in a municipal energy budget. Solutions: closed-cycle or dry cooling and diffuser design to meet thermal criteria; energy optimisation of the utility — fine-bubble aeration with dissolved-oxygen control, high-efficiency pumping and variable frequency drives, and anaerobic digestion with combined heat and power to move the plant toward energy neutrality. | Impacts: high-strength and toxic process effluents that upset municipal biological treatment or pass through it; large consumptive water withdrawals competing with municipal and ecological needs. Solutions: a sewer-use bylaw with enforced pretreatment at each discharger, backed by surcharge agreements and monitoring; industrial symbiosis and water reuse, cascading one plant's treated effluent to another's lower-grade demand and closing cooling loops. |
| Solid waste management | Impacts: rising per-capita generation with shrinking landfill availability near the urban edge; illegal dumping and litter loading into the storm system. Solutions: source separation with three-stream collection and organics diversion to composting or anaerobic digestion, supported by pay-as-you-throw pricing; strategically located transfer stations and materials recovery facilities to cut haul distance and emissions. | Impacts: greater volumes of packaging and short-lived consumer goods, and a growing stream of electronic waste containing lead, mercury and brominated flame retardants. Solutions: extended producer responsibility regulation making manufacturers fund end-of-life management and design for disassembly; energy recovery from the genuinely residual fraction, with full flue-gas cleaning, ranked below diversion in the waste hierarchy. | Impacts: hazardous and characteristic wastes requiring secure handling; large volumes of process residuals, slags and sludges. Solutions: cradle-to-grave manifesting and licensed secure landfill or high-temperature treatment for the hazardous fraction; by-product exchange within an eco-industrial park, so that one facility's residual is another's feedstock — slag to cement, waste heat to a neighbouring process. |
Three themes run across the matrix and are worth stating explicitly. First, source control consistently outperforms end-of-pipe treatment on both cost and reliability: a trip not driven, a kilowatt-hour not consumed and a package not manufactured require no capital works at all. Second, intensification is not simply bad — compact urban form reduces per-capita vehicle emissions, servicing costs and land consumption, and the engineering task is to pair density with the transit, stormwater and collection capacity it presupposes rather than to resist it. Third, cumulative effects are the recurring regulatory blind spot: each of the three drivers produces impacts that are individually permittable and collectively unacceptable, which is precisely why airshed and watershed-scale assessment, rather than facility-by-facility permitting, is the direction Canadian practice has moved.
