18-Env-B5 Industrial & Hazardous Waste Management · December 2014
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; provincial Environmental Protection / Hazardous Waste Regulations (e.g. BC's Hazardous Waste Regulation, O.Reg. 347 in Ontario); Montgomery & Runger, Applied Statistics and Probability for Engineers (for Q1–Q5's basic-statistics content).
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.
Because no on-site data exists for a not-yet-built facility, the footprint estimate is built up from published per-animal-unit loading factors rather than direct measurement, following four steps. (1) Establish the per-hog waste generation rate. Published livestock-waste engineering references (e.g. ASABE/agricultural-engineering standards, provincial agricultural waste management guides) give typical values on the order of 4–7 L/day of manure/wastewater per finishing hog and roughly 0.10–0.20 kg BOD5 per hog per day, depending on animal size/growth stage and whether flush or scrape manure management is used — the specific published factor adopted should be stated explicitly as an assumption. (2) Scale to the total herd. Multiply the per-hog factor by 5,000 to obtain total daily flow (m3/day) and organic loading (kg BOD5/day) — for example, at an illustrative 5 L/hog·day and 0.15 kg BOD5/hog·day, this gives roughly 25 m3/day and 750 kg BOD5/day. (3) Select a treatment technology appropriate to a livestock operation's characteristic high-strength, high-solids waste (e.g. an anaerobic lagoon/digester as primary treatment, given the waste's very high organic strength relative to municipal wastewater, followed by a storage/land-application or aerobic polishing step), and obtain (or assume, citing the source) a typical design loading rate for that technology — e.g. an anaerobic lagoon organic loading rate in kg BOD5/m3·day, or a storage lagoon design retention time and depth. (4) Divide the total loading by the selected design loading rate (or compute the required storage volume from the retention time) to get the required treatment volume, then divide by a design depth to obtain the footprint area (plus buffer/setback area required by provincial livestock-siting regulations, which is often the larger constraint in practice). The result should be presented as an order-of-magnitude estimate with its governing assumptions stated explicitly, since it is inherently no more precise than the published per-animal factors it is built from.
