18-Env-A1 Principles of Environmental Engineering · December 2013
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — December 2013 — 04-Env-A1 / Principles of Environmental Engineering. 3 hours duration; closed book with an 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.); Guidelines for Canadian Drinking Water Quality (Health Canada); Canadian Council of Ministers of the Environment (CCME) water-quality guidelines; Canadian Environmental Protection Act, 1999 (CEPA).
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.
1. Install (or upgrade to) a cooling tower on the discharge path itself. Even where a cooling tower already rejects most plant waste heat, routing the final effluent through an additional wet or dry cooling stage before it reaches the stream rejects the remaining heat load to the atmosphere rather than to the fishery, directly cutting the thermal load entering cold-water habitat.
2. Use a multiport diffuser outfall (or a cooling pond/wetland ahead of discharge). A diffuser rapidly mixes and dilutes the warm effluent with the receiving stream over a short, engineered mixing zone, so the temperature rise at the edge of that zone meets the thermal criterion protecting the fishery; alternatively, a shallow cooling pond or constructed wetland allows passive heat loss to the atmosphere before the water is released, achieving the same effect without continuous energy input.
1. A noise barrier or earthen berm along the highway right-of-way, which attenuates sound by diffraction over the barrier's top edge; a well-designed barrier of sufficient height and continuous length typically achieves a 5–10 dB reduction at the nearest residences, a substantial perceived-loudness reduction given the logarithmic decibel scale.
2. Source-level and distance controls — open-graded friction-course pavement (which reduces tire-pavement noise generation), lower posted speeds on the adjacent segment, and a vegetated setback/buffer between the highway and the residential lots, which combine reduced source noise with increased geometric attenuation over the 50 m separation distance.
Greenhouse gases (CO₂, CH₄, N₂O and others) are largely transparent to incoming shortwave solar radiation but strongly absorb and re-emit outgoing longwave (infrared) radiation from the Earth's surface. As anthropogenic emissions raise their atmospheric concentration, more of that outgoing infrared energy is trapped rather than escaping to space, increasing the global mean surface temperature — the enhanced greenhouse effect.
Engineering technology: carbon capture and storage (CCS) at a large stationary source such as a coal- or gas-fired power plant, which captures CO₂ from the flue gas (or before combustion) and sequesters it in a deep geological formation rather than releasing it to the atmosphere.
Effectiveness measurement: a continuous emissions monitoring system (CEMS) on the stack, measuring CO₂ mass flow rate both upstream and downstream of the capture unit, combined with periodic third-party verification and reporting under a formal GHG reporting protocol (e.g., Environment and Climate Change Canada's GHG Reporting Program), which together quantify the tonnes of CO₂e captured/avoided against a documented pre-capture baseline.
Sulphur dioxide and nitrogen oxides from fossil-fuel combustion are oxidized in the atmosphere — catalyzed by sunlight and atmospheric moisture — to sulphuric and nitric acid respectively: $$\begin{aligned} 2\,\text{SO}_2 + \text{O}_2 &\rightarrow 2\,\text{SO}_3 \\ \text{SO}_3 + \text{H}_2\text{O} &\rightarrow \text{H}_2\text{SO}_4 \end{aligned}$$ $$\begin{aligned} 2\,\text{NO} + \text{O}_2 &\rightarrow 2\,\text{NO}_2 \\ 3\,\text{NO}_2 + \text{H}_2\text{O} &\rightarrow 2\,\text{HNO}_3 + \text{NO} \end{aligned}$$ These acids dissolve into atmospheric moisture and fall as precipitation with pH well below the natural background of about 5.6, acidifying lakes, soils and forests, often far downwind of the original source.
Engineering solution: wet limestone flue-gas desulphurization on the power-plant stack, which removes SO₂ from the flue gas before it reaches the atmosphere, cutting the primary sulphuric-acid precursor at its source (the same control identified in Q1(i) above, now applied specifically to acid-rain prevention).
