18-Env-B5 Industrial & Hazardous Waste Management · May 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
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 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.
21.1 – Plug-flow. A municipal activated-sludge plant treating a relatively steady, well-characterized domestic sewage flow is a good plug-flow candidate: the influent quality is fairly uniform, so the tapering food-to-microorganism gradient along a plug-flow basin (high substrate at the inlet, progressively lower toward the outlet) gives better effluent quality, better settling sludge, and higher treatment efficiency per unit volume than complete-mix, with no shock-load risk to guard against.
21.2 – Complete-mix. An industrial wastewater treatment system receiving a highly variable, potentially shock-loaded or intermittently toxic discharge (e.g. a batch-process chemical plant) is a good complete-mix candidate: instantaneous, complete blending dilutes any incoming toxic slug or organic shock load across the entire basin volume immediately, protecting the biomass from a concentration spike that could otherwise upset or kill a plug-flow reactor's more exposed inlet zone.
