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New Sac manual ch 3
Test questions- multiple choice
| Question | Answer |
|---|---|
| What is the purpose of coaguation and flocculation? | To remove particulate impurities. |
| What is coagulation? | Clumping together of fine particles into larger particles with chemicals. |
| What is flocculation? | Gathering together of particles by gentle stirring. |
| How long should the coagulation reaction last? | A few seconds |
| Why are coagulant aids used? | To add density and toughness to flocs. |
| What is the most commonly used coagulation chemical? | Alum |
| How can operator verify the effectiveness of the coagulant chemicals and dosages being applied at the flash mixer? | Perform jar tests |
| What is the disadvantage of mechanical mixers in coagulation? | Higher electricity use than other methods. |
| What is the purpose of the flocculation process? | To create floc of good size, density and toughness. |
| How are the proper type and amount of coagulant chemicals determined? | By conducting daily jar tests. |
| How can poor process performance be spotted early so that corrective measures can be taken? | Monitor water quality throughout the water treatment process. |
| What is the detention time (min) in a rectangular floc basin when flow is 0.9 MGD? Basin is 24x12x8 ft. | 28 min. 24 x 8 x 12 x 7.48 x 24 hr/day x 60 min/hr. Divide by 900,000. |
| What is the basic purpose of the jar test? | Duplicate plant detention times and mixing and settling conditions in the lab. |
| After a jar test is completed, what does a hazy settled water indicate? | Poor coagulation. |
| Which of the following factors are not important when evaluating jar test results? | Paddle construction. |
| Determine the setting on a dry alum feeder in pounds per day when the flow is 1.2MGD. Jar tests indicate that the best alum dose is 9 mg/L | 90 lbs/day. 1.2MGD x 9 mg/L x 8.34 lbs/gal |
| What is best described as floc appearance? | popcorn flake |
| A water treatment plant used 24 pounds of cationic polymer to treat 1.4 MG of water during a 24 hr. period. What is the polymer dosage in mg/L? | 2.1 mg/L. 24 divided by (1.4 x 8.34) |
| Why should operators keep polymer powders off of floors? | They become extremely slippery when wet. |
| Liquid polymer is supplied to a water treatment plant as a 15 percent solution. How many gallons of liquid polymer should be mixed in a barrel with water to produce 100 gallons of 0.5 percent solution | 3.33 gal. (0.5 % x 100 lbs)/ 15 % solution. |
| Which items are adjusted in the enhanced coagulation process? | pH and coagulant dosage |
| What is the purpose of the hydrocyclones in ballasted flocculation? | To separate microsand from the sludge. |
| Ballasted floc process has 2 hydrocyclones in operation (2 trains) with an influnt flow of 4000 gpm w/microsand slurry recirculation rate of 300 gpm. Six samples of microsand at 30 (3), 25 (2) and 40 (1). Volumes in cone averaged 2000 mL. | 3.8 g/L. Average of six samples = 30mg/L. Multiply 30 by 300gpm x 1 Train x 1700 (bulk density conversion factor). Divide by (4000 gpm x 2000 mL) = 1.8 g/L. Multiply by 2, the number of trains. 3.8 g/L. |
| Why should operators maintain a diluted feed solution in ballasted floculation? | To minimize microsand losses from the hydrocyclone. |
| What is the fist step in optimizing a ballasted flocculation process? | Optimize the coagulant dose. |
Created by:
sgaskell