18-Env-B9 Environmental Chemistry and Microbiology · May 2017
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — May 2017 — 04-Env-B9, Environmental Chemistry/Microbiology. 3 hours duration; closed-book exam (approved Casio or Sharp calculator only). The paper has two sections — Section 1: Chemistry (6 questions, 50 marks) and Section 2: Microbiology (12 questions, 50 marks) — eighteen questions constitute the complete exam and all are answered below. Total examination mark 100.
Reference texts. Davis & Cornwell, Introduction to Environmental Engineering (6th ed.) (water chemistry, coagulation, sludge chemistry, disinfection); Metcalf & Eddy (Tchobanoglous, Stensel, Tsuchihashi & Burton), Wastewater Engineering: Treatment and Resource Recovery (5th ed.) (chemical phosphorus precipitation, biomass stoichiometry, activated-sludge microbiology, SRT/F:M); Madigan, Martinko, Bender, Buckley & Stahl, Brock Biology of Microorganisms (14th ed.) (bacterial structure, growth kinetics, microbial physiology); Guidelines for Canadian Drinking Water Quality (Health Canada).
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.
Reclaiming drinkable water from raw municipal wastewater requires two stages in series: conventional secondary treatment to remove the bulk of BOD/TSS/nutrients, followed by an advanced multi-barrier train that removes the residual dissolved solids, trace organics and pathogens to a potable standard. The train sketched below is screening & grit removal → primary clarification → nitrifying activated sludge → secondary clarification → micro-/ultrafiltration (particulate/pathogen barrier) → reverse osmosis (dissolved-solids/trace-organic barrier) → UV/advanced oxidation (AOP) disinfection → product water, with primary and waste-activated sludge routed to solids handling, membrane backwash returned for reprocessing, and the RO concentrate (brine) sent to disposal/further treatment.
