18-Env-A1 Principles of Environmental Engineering · December 2017
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — December 2017 — 04-Env-A1 / Principles of Environmental Engineering. 3 hours duration; closed book with a candidate-prepared 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.); Sawyer, McCarty & Parkin, Chemistry for Environmental Engineering and Science; Mihelcic & Zimmerman, Environmental Engineering: Fundamentals, Sustainability, Design; Guidelines for Canadian Drinking Water Quality (Health Canada); Canadian Council of Ministers of the Environment (CCME) water-quality and municipal solid-waste guidelines; Canadian Environmental Protection Act, 1999 (CEPA) and Canadian Environmental Assessment Act (CEAA 2012); ISO 14040/14044 (Life Cycle Assessment); Bies & Hansen, Engineering Noise Control; Andrews, Canadian Professional Engineering and Geoscience (professional ethics).
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.
For VOC emissions, a regenerative thermal oxidizer (RTO) is a widely accepted BACTEA technology: it combusts the VOC-laden exhaust stream at high temperature (typically 800–850 °C) while recovering heat from the outgoing clean gas to preheat incoming exhaust, achieving destruction removal efficiencies of 95–99% at relatively modest ongoing fuel cost. For $PM_{10}$, a fabric-filter baghouse is the corresponding BACTEA technology: particle-laden gas is forced through woven or felted filter media that captures particulate down to sub-micron sizes at collection efficiencies typically exceeding 99%.
Contingencies needed to ensure ongoing emission compliance: for the RTO, continuous monitoring of combustion-chamber temperature and destruction efficiency (or a surrogate such as total hydrocarbon breakthrough) is required, together with a documented startup/shutdown/malfunction plan, since DRE can drop sharply below the design combustion temperature; a leak-detection-and-repair (LDAR) program for upstream fugitive VOC sources (valves, flanges, pump seals) is also needed, since a well-controlled stack means little if uncontrolled fugitive losses bypass the RTO entirely. For the baghouse, continuous differential-pressure monitoring across the bag bank is needed to detect bag failure or blinding in near-real time (a torn bag can cause a sudden, large particulate excursion that a periodic stack test would miss), along with a bag replacement/maintenance schedule, proper handling and disposal of the collected dust (which may itself be a hazardous waste depending on the source), and temperature control upstream to avoid moisture condensation that would blind or damage the filter media.
Three long-term engineering strategies to reduce a large municipality’s solid waste generation by 50% over a 20-year horizon:
| Strategy | Advantage | Challenge | Relative Cost |
|---|---|---|---|
| Expanded source-separated organics diversion (green-bin program with residential/commercial coverage) | Targets the single largest waste fraction (food and yard organics, roughly 30–40% of the municipal stream), diverting it to composting or anaerobic digestion instead of landfill | Participation and contamination rates depend heavily on public compliance and ongoing education; processing capacity must scale with collection volume | Moderate |
| Extended producer responsibility (EPR) and packaging-reduction regulation | Shifts the incentive to design less wasteful, more recyclable packaging upstream to the producer, reducing waste generation at the source rather than only managing it after disposal | Requires provincial/regional regulatory authority and industry buy-in; municipality alone cannot mandate it | Low (municipal cost) to moderate (sector-wide) |
| Advanced residual-waste processing (mixed-waste material recovery plus waste-to-energy for the non-recyclable, non-compostable remainder) | Recovers additional recyclables from the residual stream and converts otherwise-landfilled residual waste to energy, further cutting landfill volume beyond diversion alone | High capital cost, long permitting/siting timeline, and public/community opposition to combustion-based facilities and their air emissions | High |
An environmental Guideline is a non-legally-binding, recommended numeric or narrative benchmark intended to protect a defined use or receptor — it states what level of a parameter is considered protective, but carries no direct enforcement or penalty mechanism. The CCME Canadian Water Quality Guidelines for the Protection of Aquatic Life are a typical example: a recommended concentration for a given substance in a receiving water, used by regulators and proponents as a technically defensible benchmark for site-specific risk assessment, water-quality objective-setting, or as an input to a discharge permit, without itself being directly enforceable.
An environmental Standard is a legally binding, enforceable numeric limit set out in regulation or in a facility-specific permit/approval, with defined compliance monitoring and penalty provisions for exceedance. A provincial industrial wastewater discharge permit limit (e.g., a maximum daily or monthly-average concentration for total suspended solids or a specific contaminant, set under provincial environmental protection legislation) is a typical example: exceeding it is a regulatory offence subject to enforcement action.
The choice between the two reflects the purpose: a Guideline is used where scientific/technical benchmarking flexibility is wanted — e.g., translating a general water-quality objective into a site-specific limit that accounts for local background conditions, or providing guidance in areas without the political/scientific consensus needed to legislate a single national number. A Standard is used where consistent, enforceable protection at a specific, controllable point (such as a permitted discharge) is required and where non-compliance needs a clear legal consequence to be effective — a permitted discharger’s emissions are a controllable point source, so an enforceable numeric limit is both practical to set and necessary to ensure compliance, whereas the CCME aquatic-life benchmark applies broadly across receiving waters influenced by many uncontrolled and diffuse sources, where a single legally enforceable national number would be far harder to apply consistently.
