18-Env-A1 Principles of Environmental Engineering · December 2015
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exam — December 2015 — 04-Env-A1 Principles of Environmental Engineering (Closed Book, 3 hours; candidate-prepared 8½×11" double-sided aid sheet permitted). Any five (5) of the seven (7) problems below constitute a complete paper; all seven are solved here as a full study resource.
Reference texts: Davis & Cornwell, Introduction to Environmental Engineering, 6th ed.; Metcalf & Eddy, Wastewater Engineering: Treatment and Resource Recovery, 5th ed.; Mihelcic & Zimmerman, Environmental Engineering: Fundamentals, Sustainability, Design; 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 (CEPA, 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.
| Method | Advantage | Limitation | Most appropriate application |
|---|---|---|---|
| Activated-carbon adsorption — VOC-laden gas passed through a carbon bed that adsorbs organics onto its high-surface-area pore structure | Very high removal efficiency (>95%) for a wide range of VOCs at low-to-moderate concentrations; carbon can be thermally regenerated and reused | Bed becomes saturated and needs periodic regeneration/replacement; poor performance for humid streams or very high VOC loading (rapid breakthrough) | Solvent-recovery operations and paint/printing facilities emitting benzene or other VOCs at low-moderate, fairly steady concentration |
| Thermal/catalytic oxidation (afterburner) — VOC stream heated (directly, or over a catalyst at lower temperature) to combust organics to CO2 and H2O | Can achieve >99% destruction of VOCs including acetone and other oxygenated solvents, with no spent-media disposal issue | Significant fuel/energy cost to sustain combustion temperature (catalytic oxidation lowers but does not eliminate this); catalyst can be poisoned by certain compounds | High-concentration, continuous VOC streams such as chemical/pharmaceutical manufacturing off-gas |
| Baghouse fabric filtration (for particulate air toxics, e.g., PM10 metals-bearing dust) | Very high PM10 collection efficiency (>99%), including fine particulate that cyclones miss | Fabric can blind/foul with sticky or moist particulate, and requires periodic bag replacement | Cement kilns, metal smelting, and other fixed sources with dry particulate-laden fixed-source emissions |
Any two of the methods above (adsorption paired with oxidation for VOCs, or either paired with baghouse filtration for particulate-bound toxics) satisfy the question; the common engineering principle is matching the control technology to the phase (vapor vs. particulate) and concentration regime of the specific air toxic being targeted.
| Issue | Strategy 1 | Strategy 2 | Standards/guideline link |
|---|---|---|---|
| Noise | Perimeter earthen berm and vegetated buffer between active tipping face and nearest residences, sized using a predictive noise model | Operational controls: restrict heavy-equipment and truck movements to daytime hours, and require backup alarms compliant with reduced sound-power limits | Predicted receptor sound level held below the provincial environmental noise guideline (commonly 40–55 dB(A) depending on time of day/land use) |
| Dust | Daily/intermediate soil cover over the active tipping face, plus water-truck dust suppression on unpaved haul roads | Wheel-wash station at the site exit to prevent trackout of contaminated soil/waste dust onto public roads | Site fugitive-dust management plan required under the provincial air-quality/landfill operating permit; keeps ambient PM10 below the CCME/provincial air quality objective at the property line |
| Truck traffic congestion | Dedicated haul-road access with a scheduled/staggered arrival system (booking windows) to spread truck arrivals across the day | Truck route agreement with the municipality directing traffic away from residential streets and school zones onto arterial roads | Complies with the municipal traffic bylaw and the landfill's site-specific transportation management plan condition in its operating certificate |
Sizing each strategy for the full 25-year operating life matters because the tipping face, haul routes and traffic volumes will migrate across the site as cells are sequentially filled and closed; the berm/buffer, cover program and haul-road plan should therefore be phased to track the active cell location rather than fixed to the site's initial layout.
