Suppose each household puts out 028 m3 of waste each weck Pa

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.

Solution

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