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.
Each growth driver stresses air quality, water demand and wastewater treatment differently, and the engineering solutions differ accordingly — a demand-side (efficiency, planning) response versus a supply-side (control technology, capacity) response. The 3×3 table below summarizes two major impacts and two corresponding solutions for each of the nine growth-area / environmental-medium combinations.
| 2 Impacts & 2 Solutions | (i) Population Growth | (ii) Economic Growth | (iii) Increase in Energy Use |
|---|---|---|---|
| Air Emissions | Impacts: more vehicle-kilometres-travelled and residential space-heating raise criteria-contaminant and GHG emissions; unplanned growth increases small open-burning sources. Solutions: transit-oriented densification to cut per-capita travel; tighter building-emission/energy codes for new construction. | Impacts: expanded industrial/manufacturing activity increases point-source SOx/NOx/VOC/PM emissions; growth in freight/commercial traffic. Solutions: best-available-control-technology (BACT) permitting for new/expanding industrial sources; incentives for cleaner freight (electrification, rail modal shift). | Impacts: higher combustion-based generation raises GHG and criteria-contaminant emissions; energy-intensive industry emissions grow with demand. Solutions: demand-side energy-efficiency programs to flatten load growth; shifting new generation to lower-emission sources. |
| Water Demand | Impacts: rising per-capita and aggregate potable demand strains source-water yield; higher peak-day demand stresses distribution infrastructure. Solutions: water-efficient fixture/appliance standards with tiered pricing; non-revenue-water (leak) reduction and demand-management programs. | Impacts: industrial/commercial process water demand competes with municipal supply; risk of over-allocating a shared source. Solutions: industrial water-reuse/recycling requirements in permits; source-water allocation planning with reserved environmental flows. | Impacts: added thermoelectric generation capacity increases cooling-water withdrawal/consumption; fossil fuel extraction/processing adds water use. Solutions: closed-loop (recirculating) cooling instead of once-through cooling; prioritizing low-water-intensity generation (wind, solar PV). |
| Wastewater Treatment | Impacts: increased hydraulic and organic loading can exceed existing plant capacity; more combined-sewer overflow events in older systems. Solutions: phased plant-capacity expansion sized to a long-range population forecast; sewer separation or added wet-weather storage/treatment capacity. | Impacts: industrial effluent with higher-strength or non-conventional pollutants (metals, specific organics) can exceed the municipal plant’s design basis and inhibit biological treatment. Solutions: industrial pretreatment programs with discharge permits/local limits; on-site treatment for non-conventional pollutants before sewer connection. | Impacts: cooling-water blowdown adds thermal loading to receiving waters (see Question 4(iii)); treatment plants are themselves energy-intensive, so growth compounds sector-wide energy demand. Solutions: temperature control of cooling-water discharge before release; energy-efficiency retrofits and biogas/combined-heat-power recovery at treatment plants. |
(i) Population growth most directly stresses per-capita infrastructure demand across all three media; land-use planning (densification, efficient fixtures) is generally the most cost-effective lever because it reduces demand growth itself rather than only adding downstream treatment capacity.
(ii) Economic growth concentrates its impact at industrial point sources, so permitting-based controls (BACT, pretreatment programs, allocation planning) that constrain the source directly are the most effective response, since a growing economy’s emissions and effluent are typically far more concentrated and technically controllable than population-driven diffuse demand.
(iii) Increase in energy use couples all three media together through the electricity-water-emissions nexus (thermoelectric cooling water, combustion emissions, and the energy embedded in treating water and wastewater), so solutions that reduce energy demand (efficiency) or shift to low-water, low-emission generation address multiple impacts simultaneously rather than trading one medium’s impact for another’s.
