Population, Economic Growth and Industrialization as Causes of Pollution: 18-Env-A1 Principles of Environmental Engineering, May 2015, Q4

Question 4: Population, Economic Growth and Industrialization as Causes of 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.

Population growth, rising water use and industrial expansion each place additional demand on the same three environmental media — air, water supply and wastewater treatment — but the dominant impact mechanism differs by growth driver, and so does the most effective engineering response. The 3×3 matrix below pairs the two major impacts and two corresponding engineering solutions requested for each cell.

2 impacts & 2 solutions, by growth area and environmental medium
Impact & Solutions	Urban Growth	Water Use	Industrial Expansion
Air Emissions	Impacts: increased vehicle-km travelled (mobile-source $\text{NO}_x$/VOC/PM) and space-heating emissions from new housing stock. Solutions: transit-oriented/compact land-use planning to cut vehicle-km; district energy or electrified heating to displace combustion heating.	Impacts: energy consumed pumping/treating/distributing a larger water supply (indirect emissions from the electrical grid); emissions from any new water-supply infrastructure construction. Solutions: demand-side water conservation (reduces pumping/treatment energy 1:1 with volume saved); energy-efficient pump/aeration equipment at the treatment plant.	Impacts: stack emissions of $\text{SO}_2$/$\text{NO}_x$/particulates and process VOCs from new industrial fixed sources. Solutions: best-available-control-technology (BACT) emission controls (scrubbers, baghouses, catalytic oxidizers) as a permit condition; fuel-switching to lower-emission process energy sources.
Water Demand	Impacts: peak-day demand growth outstripping existing supply/distribution capacity; increased impervious cover reducing natural groundwater recharge. Solutions: low-impact development (permeable pavement, bioswales) to sustain recharge; tiered/volumetric water pricing and mandatory low-flow fixtures to flatten peak demand.	Impacts: direct increase in withdrawal from the source (river/aquifer), risking over-allocation and reduced environmental flows. Solutions: water-use efficiency and reclaimed-water reuse for non-potable demands (irrigation, industrial cooling); source diversification (conjunctive use of surface and groundwater) to spread withdrawal risk.	Impacts: large process-water withdrawals competing with municipal and ecological demand, especially for water-intensive industries. Solutions: closed-loop/recirculating process water systems to cut fresh-water intake; industrial water-reuse permits tied to a facility's demonstrated efficiency.
Wastewater Treatment	Impacts: growing sanitary flow and combined-sewer overflow frequency exceeding existing plant/collection-system capacity. Solutions: staged plant capacity expansion tied to a growth-management plan; sewer separation and green infrastructure to cut wet-weather flow.	Impacts: higher hydraulic loading diluting/straining biological treatment capacity as overall water (and hence wastewater) volumes rise. Solutions: water-conservation programs that flatten wastewater flow growth alongside supply demand; flow equalization to smooth peak hydraulic loading on the plant.	Impacts: industrial effluent with elevated or unusual (potentially toxic) loadings threatening biological treatment performance at the municipal plant. Solutions: industrial pretreatment programs/sewer-use bylaws requiring on-site treatment before discharge; dedicated industrial-effluent treatment trains separate from the municipal biological process.

Concept & Theory

Topic. Environmental pressures of population, water-use and industrial growth across the air/water-supply/wastewater media.

Key relations. Growth pressure × medium matrix; demand-side management as a first-line mitigation common to all three growth drivers.

Why this works. Every cell in the matrix reduces to the same underlying logic: growth increases either a load (emissions, effluent) or a withdrawal (water demand), and the engineering response either reduces that load/withdrawal at the source (efficiency, pretreatment) or expands the system's capacity to absorb it (staged expansion, diversified supply) — forcing both onto the same page makes the trade-off between "reduce the pressure" and "grow the infrastructure" explicit for the planner.

Common pitfall. Answering "build more capacity" for every cell without any source-reduction/demand-side measure, which is neither sustainable nor consistent with the question's requirement to meet strict environmental requirements under continued growth.

Source. Davis & Cornwell, Introduction to Environmental Engineering, ch. 1 (population/growth pressures) and ch. 2 (sustainability); CCME source-water and municipal wastewater guidance.

Question 4 of 7: Population, Economic Growth and Industrialization as Causes of Pollution

Question 4: Population, Economic Growth and Industrialization as Causes of Pollution (20 marks)