Suppose each household puts out 0.28 m3 of waste each weck. Packer trucks with a
ID: 2311470 • Letter: S
Question
Suppose each household puts out 0.28 m3 of waste each weck. Packer trucks with a compaction ratio of 4.2 take 30 seconds per customer to collect the residential waste. Two trucks are being considered: a larger truck that makes two trips per day to the disposal site, and a smaller truck that makes three. 8. Larger truck Smaller truck Trips per day to disposal site Truck volume (m) Annualized truck cost (S/year) Total time driving, unloading, breaks (min/day) 28 125,000 150 14 72,000 195 a. Operating five days per week, with once-per-week pick-up, how many household would cach truck service? b. How many hours per day would each truck and crew have to operate to fill the trucks each day? c. With the cost of crew being $48 per hour, what is the total annual cost of trucks and crew for cach system? From that, find the annual cost per household. As the municipal engineer, which truck would you recommend to the citizen to minimize the cost? d.Explanation / Answer
per week waste generation = 0.28 m3 / week
operation 5 days per week
compaction ratio is 4.2
if the volume of the truck is V then
no of family N Per week = V*5*4.2 /0.28
For Large truck N= 28*5*4.2/.28=2100
For small truck N= 14*5*4.2/.28=1050
b)
each day they are serving
Large truck = 2100/5 = 420 families
small truck = 1050/5 = 210 families
time for large truck 420*30/60+150 = 360 min = 6 hr
time for small truck 210*30/60+195= 300 min = 5 hr
c)
total no of working days in year = 52*5 = 260 days ( 5 days/week)
cost of crew for large truck = 48*260*6 = $74880
cost of crew for small truck = 48*260*5 = $62400
total annual cost for large truck = $125000 +$74880 =$199880
total annual cost for small truck = $72000 +$62400=$134400
annual cost per households for large truck = $199880/2100 = $95.181
annual cost per households for small truck = $134400/1050 =$128
d)
clearly we can see large truck is of minimum cost