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

Question 25 of 28: Cost-Effective Treatment for a Seasonal Wastewater with a Nearby Municipal Plant

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 25: Cost-Effective Treatment for a Seasonal Wastewater with a Nearby Municipal Plant (5 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. Characterize the seasonal wastewater — flow, BOD5/COD/TSS/nutrient/toxic constituent concentrations, and the actual duration and timing of the production season, since the whole cost comparison hinges on how short and how strong the discharge period actually is.
  2. Confirm the municipal plant's available capacity (hydraulic and organic headroom) during the industry's production season, and the sewer-use bylaw's numeric pretreatment limits and surcharge/user-fee structure.
  3. Assess what pretreatment (if any) is needed to meet the sewer-use bylaw — typically just removal of anything the bylaw specifically restricts (fats/oils/grease, pH extremes, certain metals), which is usually far less treatment than a full stand-alone plant would need.
  4. Develop a life-cycle cost comparison of the realistic options — (a) pretreat-and-discharge to the municipal sewer under an agreement/surcharge, (b) build a stand-alone seasonal treatment plant (which sits idle, and its fixed/capital cost, most of the year), and (c) a hybrid (equalize on-site, haul or pretreat, discharge to sewer only during the season).
  5. Weigh the seasonal-idle-capital penalty against a stand-alone plant explicitly — a plant sized for peak season flow but operated only a few months a year has poor capital utilization, which is usually the single biggest cost driver favouring the municipal-discharge option.
  6. Recommend the lowest life-cycle-cost option that reliably meets the applicable standard, and negotiate the sewer-use agreement/surcharge rate with the municipality if that is the recommended route.