18-Env-B9 Environmental Chemistry and Microbiology · May 2013
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — May 2013 — 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 (11 questions, 50 marks) and Section 2: Microbiology (14 questions, 50 marks) — twenty-five 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, disinfection, water/wastewater microbiology, indicator organisms); Metcalf & Eddy (Tchobanoglous, Stensel, Tsuchihashi & Burton), Wastewater Engineering: Treatment and Resource Recovery (5th ed.) (chemical unit processes, chemical phosphorus precipitation, biomass stoichiometry, activated-sludge microbiology); Guidelines for Canadian Drinking Water Quality (Health Canada); MWH's Water Treatment: Principles and Design (3rd ed.) (chlorine disinfection, contact-tank sizing).
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.
This is the classic epidemiologic transition: over the past century, engineered public-health interventions — safe drinking-water treatment and disinfection, sanitary sewerage, vaccination programs, and antibiotics — dramatically reduced mortality from infectious/waterborne diseases (cholera, typhoid, and similar illnesses that once dominated the mortality tables, directly the subject of this exam's Chemistry/Microbiology content). As infectious-disease deaths fell sharply and life expectancy rose, a much larger share of the population now survives long enough to die of chronic, non-infectious conditions — cardiovascular disease, cancer, diabetes — whose incidence rises steeply with age, together with lifestyle/diet changes (caloric excess, reduced physical activity, tobacco use) that independently increase chronic-disease risk. The apparent “increase” in non-infectious deaths is therefore driven both by an aging population living long enough to develop them and, in absolute terms, by their share of total mortality rising as the infectious-disease share fell — the two trends are directly linked, not independent.
