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18-Env-A6 Solid Waste Engineering and Management · May 2013

Question 16 of 17: Packer Truck Trips per Collection Day

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

Notes on this paper

National Examination, May 2013 — 04-Env-A6 / 18-Env-A6, Solid Waste Engineering and Management. 3 hours duration, closed book, one letter-sized aid sheet permitted. All 17 questions constitute a complete paper (100 marks total).

Reference texts: Tchobanoglous, Theisen & Vigil, Integrated Solid Waste Management: Engineering Principles and Management Issues; Vesilind, Worrell & Reinhart, Solid Waste Engineering; Davis & Cornwell, Introduction to Environmental Engineering (6th ed.); CCME, Guidance Document on Landfill Gas Management.

Check: several questions on this paper (Q1, Q13, Q14, Q17) supply an incomplete data set and explicitly invite the candidate to "make and state" assumptions. Every assumed value below is called out where it is introduced and is chosen from standard solid-waste-engineering practice; the governing METHOD, not the specific assumed number, is what the exam is testing.

Question 16: Packer Truck Trips per Collection Day (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.

Given. 300 single-family residences at 4 residents each; 400 people in multi-family units; residential generation rate 1.1 kg/capita/day (Table 2); 2 curb-side pickups/week; packer truck capacity 4 t.

Find. Trips per collection day for one truck to serve the area.

  1. Total population served. $$P = (300\times4) + 400 = 1{,}200 + 400 = 1{,}600\ \text{people}$$
  2. Daily waste generation. $$m_{day} = 1{,}600 \times 1.1\ \text{kg/cap/d} = 1{,}760\ \text{kg/d}$$
  3. Waste accumulated per collection event. With 2 pickups/week, each pickup clears waste from the preceding $7/2=3.5$ days. $$m_{pickup} = 1{,}760 \times 3.5 = \boxed{6{,}160\ \text{kg}}$$
  4. Trips needed. $$\dfrac{6{,}160\ \text{kg}}{4{,}000\ \text{kg/trip}} = 1.54\ \text{trips} \Rightarrow \boxed{2\ \text{trips}}$$ (rounded up — a partial fourth-tonne load still requires a full trip).
QuantityValue
Population served1,600
Waste per collection day6,160 kg
Trips needed2