16-Civ-A3 Elementary Environmental Engineering · May 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Paper format. National Exams, May 2018 — 16-Civ-A3 Elementary Environmental Engineering. Three hours; closed book with one candidate-prepared 8½ × 11 double-sided aid sheet; approved Casio or Sharp calculator only. Seven problems are printed, each worth 20 marks, and any five constitute a complete paper (maximum 100 marks). All seven are solved here, because the set is intended as a study resource rather than an exam script. Section marks are shown in brackets at the left margin of each question and are reproduced from the final-page Marking Scheme.
Reference texts.
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.
A technical control is an end-of-pipe or in-process engineering device that physically captures or destroys the pollutant; a non-technical control is a management, regulatory or source-substitution measure that reduces the emission without a treatment device. VOCs (gaseous organic vapours) and PM10 (respirable particulate, aerodynamic diameter ≤ 10 µm) require different technical devices, so a representative device is chosen for each pollutant.
| Control | How it works | Two advantages | Two limitations |
|---|---|---|---|
| Technical — regenerative thermal oxidiser (RTO) for VOCs and a fabric-filter baghouse / electrostatic precipitator for PM10 | The oxidiser destroys VOCs at 760–820 °C (95–99% destruction); the baghouse or ESP removes PM10 by filtration or electrostatic capture (>99%). | (1) Very high, reliable removal of the targeted pollutant; (2) treats the actual exhaust regardless of upstream process changes. | (1) High capital and, for the oxidiser, fuel/energy cost (and CO2 from combustion); (2) a technology chosen for gases (oxidiser) does not remove particulate and vice-versa, so two devices are needed. |
| Non-technical — source reduction / material substitution and administrative controls (low-VOC or water-based solvents, enclosed handling, permit emission limits, preventive maintenance) | Reformulating to water-based coatings and enclosing dusty transfer points lowers the VOC and PM generated at the source, before any device sees it. | (1) Prevents the emission rather than treating it, so it avoids operating cost and secondary wastes; (2) often the cheapest and most durable reduction and improves worker exposure at the same time. | (1) A substitute product may not meet the product-performance spec, and reductions are limited by what the process can tolerate; (2) relies on management commitment and enforcement — harder to guarantee and verify than a metered device. |
The source water carries both dissolved solids (which pass a conventional filter and so demand a membrane or softening step) and taste-and-odour compounds (dissolved organics such as geosmin/MIB, best removed by adsorption or oxidation). Three main processes therefore anchor the train: (1) conventional coagulation/flocculation/sedimentation to strip turbidity and colloids ahead of the sensitive downstream units; (2) granular activated carbon (GAC) adsorption (or ozone/advanced oxidation) to remove the odour compounds; and (3) reverse-osmosis / nanofiltration membrane softening to remove the dissolved solids. Disinfection and a clearwell finish the train before distribution.
Two non-technical principles to protect potable quality through the distribution system. (1) Maintain a protective disinfectant residual and a multi-barrier management programme — a monitored free-chlorine or chloramine residual to the far ends of the network, backflow-prevention by-law, cross-connection control, and routine main flushing/valve exercising, all under an operator-certification and source-to-tap safety-plan framework. (2) Sustained monitoring, record-keeping and public reporting under the GCDWQ — regular bacteriological and residual sampling, prompt boil-water advisories, asset-renewal budgeting for aging mains, and transparent reporting to the public, so that deterioration is detected and corrected before consumers are exposed.
