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18-Env-A1 Principles of Environmental Engineering · December 2018

Question 4 of 7: Population, Urbanization and Energy Use as Causes of Environmental Pollution

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

Notes on this paper

National Exams — December 2018 — 18-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; 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); Bies & Hansen, Engineering Noise Control; Andrews, Canadian Professional Engineering and Geoscience (professional ethics).

Question 4: Population, Urbanization and Energy Use as Causes of Environmental Pollution (20 marks)

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.

(i)–(iii) Environmental Impacts and Engineering Solutions by Growth Driver

Population growth, intense urbanization and increased energy use each stress air emissions, water demand and wastewater treatment through different mechanisms, which is why the nine-cell comparison below is useful: it forces a distinct, concrete pair of impacts and matching engineering solutions for each intersection rather than one generic answer for “growth.”

2 impacts & 2 solutions, by growth area
2-Impacts & 2-Solutions(i) Population Growth(ii) Intense Urbanization(iii) Increased Energy Use
Air Emissions Impacts: rising aggregate vehicle-km travelled and residential heating emissions as population grows; increased open burning/waste-related emissions where collection infrastructure lags growth.
Solutions: transit-oriented development and vehicle-emission standards to limit per-capita transport emissions; mandatory tie-in to managed waste collection/disposal to eliminate open burning.		 Impacts: concentrated point- and area-source emissions (traffic congestion, construction dust, building heating/cooling) within a dense urban footprint; urban heat-island effect increasing ground-level ozone formation.
Solutions: district energy/low-carbon heating systems and dust-control bylaws for construction sites; green/reflective roofing and urban tree canopy targets to reduce the heat-island–ozone linkage.		 Impacts: increased combustion emissions (SO2, NOx, particulates, CO2) from expanded fossil-fuel generation; localized air-quality degradation near new/expanded generating stations.
Solutions: flue-gas desulfurization and selective catalytic reduction at new/expanded plants; a shift in generation mix toward lower-emission sources (hydro, wind, natural gas in place of coal).
Water Demand Impacts: rising total potable-water demand outpacing existing supply/distribution capacity; increased pressure on shared aquifers or surface sources as more households draw from the same system.
Solutions: tiered/increasing-block water pricing and mandatory low-flow fixtures to curb per-capita demand; phased capacity expansion of supply and distribution infrastructure tied to population projections.		 Impacts: increased impervious surface reducing natural aquifer recharge that helps sustain the supply; concentrated peak-hour demand straining distribution-system pressure.
Solutions: low-impact development (LID) and green infrastructure to sustain groundwater recharge as the urban footprint grows; smart metering and peak-demand management to flatten the daily demand curve.		 Impacts: large cooling-water withdrawals for thermal power generation competing with other users; lowered river/lake levels or groundwater tables near withdrawal points during peak demand.
Solutions: closed-loop (recirculating) cooling systems in place of once-through cooling to cut withdrawal volumes; water-use permitting with withdrawal caps tied to environmental-flow requirements.
Wastewater Treatment Impacts: rising aggregate flow and organic/nutrient loading to municipal treatment plants as population grows; more septic systems in unserviced growth areas raising groundwater contamination risk.
Solutions: staged capacity expansion and tertiary nutrient-removal upgrades ahead of projected population growth; extension of centralized sewer service (or upgraded septic standards) to unserviced growth areas.		 Impacts: increased impervious area driving combined-sewer-overflow (CSO) frequency and hydraulic overload at the plant; higher peak-flow variability from concentrated stormwater runoff.
Solutions: separation of combined sewers or CSO storage/treatment facilities; distributed stormwater detention (LID) to reduce peak flows reaching the collection system.		 Impacts: thermal (heated) cooling-water discharge and, for some generation types, ash-pond/scrubber-wastewater streams requiring specialized treatment.
Solutions: cooling towers/ponds or a diffuser outfall to control thermal discharge (see Problem 3(iii)); dedicated ash-pond/scrubber wastewater treatment (settling, chemical precipitation) before discharge or recycle.