waste and water in civil engineering A flocculation/sedimentation combination ba
ID: 1829056 • Letter: W
Question
waste and water in civil engineering
A flocculation/sedimentation combination basin in a conventional drinking water treatment plant is to be constructed of cast-in-place reinforced concrete. The horizontal flow rectangular basin will be located in NJ. The client must decide whether or not to pay to have the basins covered with a concrete slab or, alternatively, left open. Discuss all the factors that the client should consider when deciding whether or not to cover the floc/sed basin. Discuss all the advantages, disadvantages and considerations that the client should think about. Be clear and complete so the client understands what the choices are and any ramifications of the decision. If the sedimentation basin in problem 1 (ignore the floc basin for this problem) receives a flow of 1400 gallons per minute, and has a depth of 10 feet, what are the length and width dimensions if the basin is designed to remove particles that have a settling velocity greater than 30 feet per day? The basin will have a length to width ratio of 4 to 1. What are the flow through velocity and hydraulic retention time for this basin? A chemical mixing basin is to be designed to blend chlorine and treated wastewater. The basin flow is 700 gallons per minute and the basin dimensions are 5 feet by 5 feet by 5 feet water depth. The basin will have a single mechanical blender that will transfer 100% of the mixing energy from the blades to the water. The wastewater temperature will vary from 35 F to 70 F. The selected mixing intensity in the basin shall be a minimum of 600 1/sec. What size motor (horsepower) is required for the mixer? The following three chemicals in drinking water have been discussed in class. Hardness, Fluoride, and Benzene. Answer the following: What is hardness in water and why is it important? Why is too much fluoride in drinking water a problem? What is the drinking water standard for fluoride? For benzene, what are the federal epa and State of NJ drinking water standards? What is considered a safe level of benzene in drinking water? If you were designing a drinking water treatment facility for the removal of benzene, what would you set as a treatment goal and why? How would you involve the client in the decision?Explanation / Answer
4.1 hardness of water and its use
Many industrial and domestic water users are concerned about the hardness of their water. Hard water requires more soap and synthetic detergents for home laundry and washing, and contributes to scaling in boilers and industrial equipment. Hardness is caused by compounds of calcium and magnesium, and by a variety of other metals. Water is an excellent solvent and readily dissolves minerals it comes in contact with. As water moves through soil and rock, it dissolves very small amounts of minerals and holds them in solution. Calcium and magnesium dissolved in water are the two most common minerals that make water "hard."
The hardness of water is referred to by three types of measurements: grains per gallon, milligrams per liter (mg/L), or parts per million (ppm). Typically, the water produced by Fairfax Water is considered "moderately hard" to "hard." The table below is provided as a reference.
Water Hardness Scale
Grains Per Gallon
Milligrams Per Liter (mg/L)or Parts Per Million (ppm)
Classification
less than 1.0
less than 17.1
Soft
1.0 - 3.5
17.1 - 60
Slightly Hard
3.5 - 7.0
60 - 120
Moderately Hard
7.0 - 10.5
120 - 180
Hard
over 10.5
over 180
Very Hard
Often, when you purchase a new dishwasher or washing machine, the manufacturer has recommended settings that depend on the hardness of the water. The table below provides the historical range of "hardness" of water in the Fairfax Water system.
Fairfax Water Hardness Scale
Grains Per Gallon
Milligrams Per Liter (mg/L) or Parts Per Million (ppm)
Classification
2.3 - 10.1
40 -172*
Slightly Hard to Hard
*This range of data is taken from 5 years (2006
Water Hardness Scale
Grains Per Gallon
Milligrams Per Liter (mg/L)or Parts Per Million (ppm)
Classification
less than 1.0
less than 17.1
Soft
1.0 - 3.5
17.1 - 60
Slightly Hard
3.5 - 7.0
60 - 120
Moderately Hard
7.0 - 10.5
120 - 180
Hard
over 10.5
over 180
Very Hard
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