18-Env-B5 Industrial & Hazardous Waste Management · December 2017
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.
Aerobic biological treatment needs nitrogen and phosphorus, in addition to carbon (the BOD5/COD substrate), to build new microbial cell mass. The classical minimum ratio, expressed relative to the BOD5 removed, is:
BOD5 : N : P ≈ 100 : 5 : 1 (by mass) for conventional aerobic (activated sludge) systems.
Anaerobic treatment, which produces far less biomass per unit substrate consumed, needs proportionally less: roughly BOD (or COD) : N : P ≈ 100 – 350 : 5 : 1 (i.e. a lower nutrient demand per unit of organic load than the aerobic case, since less new cell mass is synthesized).
