CIVL 456: Wastewater Treatment

Homework #1- Fall 1996

Due Date: 28 August 1996

Part 1 Calculate the pumping horsepower required at the Indianapolis WWTP for each of their `secondary' screw lift pumps. These four (4) pumps collectively lift the bioroughing effluent a distance of 18 feet, with the discharge then being directed into the so-called `Oxygen Nitrification System.' You should determine the HP based on a maximal design flow for the plant of 125 MGD; you can also assume these pumps have an efficiency level of 75%. Show any other assumptions you need to make in order to derive this calculation.

Part 2: How many kwh would these pumps consume per day, and how much would it cost to run them for the same period? You may assume they operate at 110 VAC (which is not actually true, as they are 440 VAC), and that the City of Indianapolis is able to buy electricity at at a rate equal to one-half the rate typically paid by the city's average homeowner (due to their large consumption of electricity).

Part 3: a) On average, how many tons of dry sludge are produced each day at US POTW's. You may assume that only 65% of the US population is connected to POTW's. b) Assuming that one-third of all of this sludge is incinerated at only 146 POTW's, what is the average number of tons of sludge burned each day at these latter plants?

Last Modified: 23 August 1996; alleman@ce.ecn.purdue.edu