"I am always ready to learn, but I do not always like being taught."  Winston Churchill

Part 1: Solve the following three problems (you are not required to use an Excel spreadsheet)

Carbon Dioxide Removal #1

• Groundwater containing 20 mg/l of carbon dioxide is to be degasified using a multiple-tray aerator with 5 trays. In this water treatment facility, there are 10 aerators operating in parallel. For maintenance reasons, only 8 of the aerators are available at any one time. The design population is 40,000 persons, and the maximum day demand is 150 gal/person-day. The k value is 0.35, and the hydraulic loading is 4 gpm/ft.². Determine:
  

1. The carbon dioxide content of the product water.

2. The size of the trays if the length-to-width ratio is 2:1 and the trays are made in 1 in. increments.

Carbon Dioxide Removal #2

• Groundwater containing 35 mg/l of carbon dioxide is to be degasified using a multiple-tray aerator. The design population is 150,000 persons, and the maximum day demand is 150 gal/person-day. The k value is 0.36, and the hydraulic loading is 3 gpm/ft.². Determine:
  

1. Determine the total number of trays in an aerator required to reduce the carbon dioxide content of the product water by 90%.

2. Determine the number of aerators, operated in parallel, required for the water treatment facility if the size of each tray is 1,000 ft.².

Disinfection

• The following is actual data for a virus exposed to an experimental disinfectant. Estimate the contact time required to obtain a reduction of 1/50,000 of the original number of viruses.  
   

Note: A solution to the problems in Part One will be available after the due date.

Part 2:  Use Excel to develop a table containing the removal of carbon dioxide in a water treatment process using the aeration model we described in class.
       
Develop a spreadsheet where the number of aeration trays, n, varies with the row, and the rate constant, k, varies with the column.  Also, allow the initial effluent concentration to be a parameter in your calculations.  In other words, store the value of C ₀ in a cell outside the table.

Click here for an Excel template spreadsheet for this problem. Your name should appear at the top left, and the assignment number and date should appear at the top right.

The calculation of the carbon dioxide during aeration involves the use of the Excel EXP() Function.

Be very careful with your cell references (relative and absolute cell referencing) when trying to copy your formula into the table.  Pay special attention to which parameters vary along the row and which vary along the column.

Part 3:  Use Excel to demonstrate the effects of coagulant on effluent turbidity (NTU) as recorded in the lab.

1. From the jar test data, plot the supernatant turbidity (NTU) verse the coagulant dosage. Click here for jar test data.

2. Determine the best dosage of coagulant from your observations and measurements.

3. Using the dosage found in Part b, calculate the quantity (lb.) of the coagulant needed to treat 20 million gallons per day (MGD).

Part 4. Read the Chapters 3 and 4 in the "A Mind for Numbers" by Barbara Oakley.

A web page describing the CIVL 1112  Excel Homework Policy is available. Read it before you turn in each assignment this semester. You will be graded according to the policy outlined in it.

Coversheet for homework