Question

The town of Pittsford, NY is in need of a new water treatment plant to meet its average daily demand of 18, 000 m3/d and is accepting proposals from consulting firms. EMW Environmental has proposed to construct a plant which will be capable of producing 1750 m3/h and will have a storage reservoir to hold 3, 975m3of water. A second firm, EnviroSolution, is proposing Pittsford construct a plant which will produce 2, 250 m3/h, but will not have any storage capacity. Which proposal do you recommend? Show all calculations and provide a multi-sentence explanation of your decision.

Answer 1

The 1st plant with a storage reservoir is a better option as compared to that of the 2nd plant.

Step-by-step explanation:

Suppose the factor for variation in hourly demand is 2 So the average hourly demand is given as

Average Hourly Demand=Factor x Average Daily Demand

AHD=2 x 18000 m3

AHD=36000 m3

For the first pump

The Quantity in storage tank is 3975 m3

So the amount of pumping required is

`Q_(pump1)=AHD-Q_(reservoir)\\Q_(pump1)=36000-3975 \\Q_(pump1)=32025 m^3`

For this value the pump will work for following hours

`t_(pump1)=(Q_(pump))/(pumping rate_1)\\t_(pump1)=(32025)/(1750)\\t_(pump1)=18.3 \, hours`

So the pump 1 can complete the demand of the town by working for 18.3 hours.

Now in order to complete the demand, the second pump is given as

`Q_(pump2)=AHD\\Q_(pump2)=36000 m^3`

For this the pump will work for as

`t_(pump2)=(Q_(pump2))/(pumping rate_2)\\t_(pump2)=(36000)/(2250)\\t_(pump2)=16 \, hours`

So the pump 2 requires 16 hours to complete the demand of the town.

Here it is important to note that the realistic demand of the water can vary from the average value and thus when there is a drastic requirement of water in certain cases, the pump 2 will fail. Also pump 2 has to be run continuously and will produce excessive water which will be wasted if the hourly demand is less than that of the production value.

In context of this, the 1st plant with a storage reservoir is a better option as compared to that of the 2nd plant.