18-Env-B9 Environmental Chemistry and Microbiology · May 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — May 2016 — 04-Env-B9, Environmental Chemistry/Microbiology. 3 hours duration; closed-book exam (one 8.5×11" aid sheet, both sides, permitted; any non-communicating calculator permitted). The paper has two sections — Section 1: Chemistry (8 questions, 50 marks) and Section 2: Microbiology (12 questions, 50 marks) — twenty 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, BOD/SRT/F–M); Guidelines for Canadian Drinking Water Quality (Health Canada); MWH's Water Treatment: Principles and Design (3rd ed.) (advanced treatment, UV disinfection, potable reuse).
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.
1. Designing and operating biological treatment. Activated sludge, trickling filters, anaerobic digestion and nutrient removal are all engineered microbial ecosystems; sizing and operating them (F/M, SRT, DO) requires understanding microbial growth kinetics.
2. Protecting public health. Assessing and managing pathogen risk in drinking water, recreational water and wastewater discharge (Questions 8 and 13) depends on knowing how waterborne organisms are transmitted, survive treatment, and are indicated/monitored.
3. Diagnosing and troubleshooting process upsets. Problems such as sludge bulking (Question 18), foaming, or loss of nitrification are microbiologically-driven and are diagnosed by identifying which organisms are dominant and why.
4. Selecting and interpreting monitoring/analytical methods. Tests like BOD, MPN/coliform enumeration and nitrification assays are themselves biological assays whose results can only be interpreted correctly with an understanding of the underlying microbiology.
5. Managing disinfection and by-product formation. Choosing and dosing a disinfectant (chlorine, UV, ozone) to reliably inactivate target organisms (Question 14) while limiting harmful by-products requires knowing organism resistance (e.g. Cryptosporidium’s chlorine resistance vs. UV susceptibility).
