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.
Three well-known waterborne diseases are: (1) cholera, caused by the bacterium Vibrio cholerae, producing severe watery diarrhea and dehydration from a toxin that disrupts intestinal ion transport; (2) typhoid fever, caused by Salmonella Typhi, a systemic bacterial infection transmitted via the faecal–oral route through contaminated drinking water; and (3) giardiasis, caused by the protozoan parasite Giardia lamblia (a chlorine-resistant cyst-forming organism), producing gastrointestinal illness and a common cause of drinking-water-related outbreaks even in treated systems with inadequate filtration. Cryptosporidiosis (Cryptosporidium parvum) and hepatitis A are further common examples. Each of these organisms reaches drinking or recreational water through faecal contamination of the source, which is why source-water protection, adequate filtration for cyst/oocyst removal, and a disinfection CT (Question 1.10) matched to the most resistant organism present are all required together — no single barrier reliably controls all three disease agents at once.
