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.
A generalized prokaryotic (bacterial) cell is shown below, from outermost to innermost structure. The capsule is a protective, often mucous/slime layer outside the cell wall that resists desiccation, aids surface attachment (biofilm formation) and can help evade a host's immune defences. The cell wall (peptidoglycan) gives the cell its rigid shape and osmotic protection against lysis in a hypotonic environment (e.g. water/wastewater). The plasma (cell) membrane is the selectively permeable phospholipid-bilayer barrier controlling nutrient/waste transport and housing electron-transport-chain proteins for energy generation. Inside, the cytoplasm is the aqueous medium where metabolism occurs; the nucleoid is the region holding the single circular chromosome (the cell's primary genetic material, unbound by a nuclear membrane); plasmids are small extra-chromosomal circular DNA molecules often carrying accessory traits (e.g. antibiotic resistance); ribosomes are the sites of protein synthesis (translation). External appendages include the flagellum, a rotating helical filament providing motility, and pili, shorter hair-like appendages used for surface attachment and, in some species, DNA transfer (conjugation).
