NivaarExam PrepOfficial exam papers ↗

18-Env-B5 Industrial & Hazardous Waste Management · December 2017

Question 9 of 28: Interferences with Water Clarification Processes

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

Notes on this paper

Reference texts: Nemerow & Dasgupta, Industrial and Hazardous Waste Treatment, 2nd ed.; Metcalf & Eddy, Wastewater Engineering: Treatment and Resource Recovery, 5th ed.; Davis & Cornwell, Introduction to Environmental Engineering, 6th ed.; LaGrega, Buckingham & Evans, Hazardous Waste Management, 2nd ed.; CCME, Guidelines for the Management of Biomedical Waste in Canada (1992); Canadian Environmental Protection Act (CEPA), 1999; Basel Convention on the Control of Transboundary Movements of Hazardous Wastes (1989); Canadian Nuclear Safety Commission (CNSC) regulations on radioactive waste; provincial hazardous waste regulations (e.g. BC's Environmental Management Act and Hazardous Waste Regulation).

Question 9: Interferences with Water Clarification Processes (3 marks)

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. Oil, grease or surfactants — coat floc particles and interfere with coagulant charge neutralization, weakening floc formation and settling.
  2. High or variable turbidity/colour spikes — overwhelm a coagulant dose set for average raw-water quality, producing poor floc and carryover to the filters.
  3. Temperature swings — cold water increases viscosity and slows both floc formation kinetics and settling velocity (Stokes' law), reducing clarifier performance in winter.

Other accepted interferences include high alkalinity/hardness competing with the coagulant reaction, algae blooms clogging filters and consuming coagulant, and short-circuiting/hydraulic upsets in the basin itself.