16-Civ-A3 Elementary Environmental Engineering · December 2017
Question 7 of 7: Water Resource Management
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Notes on this paper
Paper format. National Exams, December 2017 — 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.
Davis, M.L. & Cornwell, D.A., Introduction to Environmental Engineering, 5th ed., McGraw-Hill — material and energy balances, reactor kinetics, hardness, disinfection, water and wastewater unit processes.
Masters, G.M. & Ela, W.P., Introduction to Environmental Engineering and Science, 3rd ed., Pearson — mass/energy balances on power plants, air-emission estimation, growth–pollution linkages.
Fogler, H.S., Elements of Chemical Reaction Engineering, 5th ed., Prentice Hall — CSTR design and gas-phase stoichiometry with change in total moles.
Canadian context. Answers use the Canadian regulatory frame: the Guidelines for Canadian Drinking Water Quality (GCDWQ) and Canadian Environmental Quality Guidelines (CCME), provincial water and wastewater regulations, the federal Impact Assessment Act / BC Environmental Assessment Act, and the Engineers Canada / EGBC code of ethics whose canons appear in Problem 2(iii).
Part (i) — Protecting a multi-use fresh-water lake (8 marks)
The lake serves three designated uses — recreation, drinking-water supply and aquatic habitat — whose common requirement is good, stable water quality; the strategies protect that quality at source, at the intake and over the long term.
Watershed / source-water protection (non-technical, planning). Establish a source-protection plan under a watershed authority: control land use in the drainage basin, buffer riparian zones, and limit nutrient and contaminant inputs from agriculture, stormwater and development. Protecting the catchment prevents problems (eutrophication, pathogen loading) rather than treating them, which serves all three uses and the long term.
Point- and non-point-source loading control (technical). Upgrade upstream wastewater treatment to nutrient removal and control stormwater/CSO discharges so that phosphorus loading — the driver of algal blooms that close beaches, foul intakes and deoxygenate fish habitat — stays below the lake's assimilative threshold.
Monitoring, standards and adaptive management (non-technical). A sustained water-quality monitoring network tied to enforceable objectives (recreational, drinking-water and aquatic-life guidelines) provides early warning and the basis to adjust management as conditions or pressures change, protecting both short- and long-term uses.
Part (ii) — Protecting an intake from CSOs and plant bypasses (6 marks)
Technical: reduce overflow frequency and volume by providing wet-weather storage and sewer separation / CSO treatment — storage tunnels or tanks that hold combined flow for treatment after the storm, high-rate clarification/disinfection at overflow points, and progressive separation of storm and sanitary sewers — so far less untreated flow reaches the source water near the intake.
Non-technical: implement real-time monitoring with public notification and an intake-management protocol: instrument the CSO and bypass points, and when an overflow occurs, alert the water treatment plant so it can adjust treatment or temporarily draw from an alternate/deeper intake, plus enforce reporting requirements that drive infrastructure investment. Inflow-and-infiltration reduction programs (a policy/maintenance measure) also cut the wet-weather peaks that cause bypasses.
Part (iii) — Water reuse to address summer shortages (6 marks)
Technical: build a water-reclamation scheme that treats municipal wastewater to a high standard (tertiary filtration + disinfection, and for stricter uses, membranes) and delivers it through a separate distribution/irrigation network for agricultural irrigation, so that river withdrawals for tobacco farming are offset by reclaimed water during low-flow months.
Non-technical: establish a reuse policy and allocation framework — water-taking permits that cap summer river withdrawals, incentives or requirements for farms to accept reclaimed water, and public/agricultural outreach to build acceptance and set fit-for-purpose quality standards.
One potential problem with farm reuse: reclaimed water can carry residual salts, nutrients, trace contaminants or pathogens; over time salt and contaminant accumulation in the soil (or crop-contact pathogen risk) can harm soil health, crops and food safety unless the water quality, irrigation method and crop type are carefully matched and monitored.
