"Gravitation can not be held responsible for people falling in love" - Albert Einstein

Objective

The purpose of this assignment is to estimate the hydraulic loading rate on a filter and to determine the required backwash velocity and the depth of the expanded medium bed in a sand filter.

Part One - Using the data obtained in the first week of water filtration lab, present, analyze, and discuss the data. Your data should be presented in graphical form. Remember that Ms. Ashman is not an engineer—explain the concepts in terms that will help her understand the data and make an informed choice about the filter.

Part Two - Consider the filters in the lab using only sand as the filter medium. The flowrate through the filter is 900 ml/min, the diameter of the filter is 3.5 inches, the depth of the filter bed is 6 inches, the sand has a particle diameter of 0.5 mm or 0.02 inches with a settling velocity of 0.27 ft/s, and the porosity of the sand is 0.30.

1. Determine the hydraulic loading rate in gpd/ft².
    
2. Based on hydraulic loading rate, classify the filter as either a slow sand filter or a rapid sand filter.
    
3. Determine the required backwash velocity to expand the sand filters in lab to a porosity of 0.80.
    
4. Determine the depth of the expanded filter bed.

Part Three - Develop the equations to describe filter efficiency. Click here for a sample description.

Part Four - Read Chapter 11 in the Strategies for Creative Problem Solving by Fogler and LeBlanc.

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