DESIGN OF FACILITIES FOR PHYSICAL WASTEWATER TREATMENT

NAME:_________________________

IDENTIFICATION1. A device with openings, generally of uniform size, that is used to retain the coarse solid found in

wastewater2. Used for screening devices consisting of perforated plates, wedge wire elements, and wire cloth. 3. Bar Racks have clear openings between____inches bars of or larger.4. Frequently used ahead of pumps.5. Imitates the movements of a person raking the rack6. Also called sewage grinders7. The first machine to address the problems of reducing solids directly inline.8. Are relatively small, with total volume based on 3-min retention at maximum flow.9. Is normally used to create the mixing pattern grit chambers10. The settled grit is normally removed with a _______and buried in a landfill.11. The process of controlling hydraulic velocity, or flow rate, through a wastewater treatment system. 12. Axial mixers can further be subdivided into other categories, the most common of which are

________ and 13. _________14. The volume calculated based on the _________is the theoretical volume. 15. A tank which allows suspended particles to settle out of water or wastewater as it flows slowly

through the tank, thereby providing some degree of purification.16. The main difference between primary and secondary clarifiers.17. The theoretical time wastewater is held in a clarifier.18. Also known as weir overflow rate, is the number of gallons of water passing over a foot of weir per

day.19. A factor expressed in terms of flow per surface area.20. A tank with diameters that ranges from 25 to 150 feet.

MULTIPLE CHOICE1.2.3.4.5.6.7.8.9.10.

TRUE OR FALSE1. Screens with 0.09 to 0.25 inch openings remove 20 % of influent solids.2. In cable-driven bar racks maintenance problems related to slack cables and fouled cable reels is a

major disadvantage.3. Bar racks consists of vertical or inclined bars spaced at equal intervals (usually 2-5 in.)4. Screening removes the smallest materials from the influent wastewater stream5. An Aerated Grit Chamber offers a high-cost but mechanically simple way to remove grit from a

wastewater stream.6. The water-lift pump option is particularly advantageous since the air supply needed for operation of

the aerated grit chamber is already in place.7. Pumps are often employed in equalization basins to achieve homogeneity in and to aerate the

wastewater. 8. The speed ranges for both portable and fixed mounted propeller mixers are 1750 rpm and 350–420

rpm, respectively. 9. The high speed of propeller provides a low degree of shear with high draft velocity10. As a general rule, square or rectangular tanks are more efficient in achieving proper mixing than

circular tanks. 11. A typical plant may have clarifiers located at two different points12. Inlets to rectangular tanks will be designed so as to allow channeling of wastewater in the tank. 13. Detention time is commonly specified as 4 hours for primary tanks serving all types of plants

except when preceding an activated sludge system.14. You can expect wastewater to have a pH of about 5 to 7 depending on the region, water supply and

wastes discharged into the collection system15. If sludge is allowed to remain in the tank it tends to gasify and the entire sludge blanket (depth)

may rise to the water surface in the clarifier.

MATCHING TYPE1.2.3.4.5.6.7.8.9.10.

ENUMERATION1-4 Mechanically cleaned bar racks 6-9 Ways of Disposing Screenings10-13 Types of Comminutors14-19 Design Procedure for Aerated Grit chamber20-24 Factors to consider in basin construction of flow equalization tank25-30 Factors Affecting Clarifier Efficiency

Answer Key

Identification

1. Screening2. Screens3. 5/84. Hand cleaned bar racks

5. reciprocating rake type bar rack6. Comminutors7. In-line Comminutors8. Aerated grit chambers

9. Diffused Air10. Continuous screw11. Flow equalization12. Propeller mixer13. Turbine mixer14. hydrograph method15. Sedimentaton Tank16. Density of sludge handled17. Detention Time18. Weir loading19. Surface Hydraulic Load20. Circular Tank

Multiple Choice

True or False

1. False2. True3. False4. False5. False

6. False7. False8. True9. False

10. False11. True12. False13. False14. False15. True

Matching Type

Enumeration

1. Chain-operated2. Reciprocating rake3. Catenary4. Cable driven5. Removal of hauling to disposal areas6. Disposal by burial on the plant site7. Incineration8. Disposal with municipal solid wastes9. Discharge to grinders or mascerators10. In-line Comminutors

11. Dual Shaft Comminutors12. In-line “Shaft-less” Design13. Hi-Flow Twin Shaft Grinder14. Calculating the peak flow15. Calculating the volume of the grit chamber 16. Calculating the dimensions of the aeration basin. 17. Determining the air-supply requirement 18. Computing the quantity (volume) of grit.19. Checking for surface overflow rate (SOR). 20. basin geometry21. basin construction including cleaning, access, and

safety; 22. mixing and air requirements; 23. operational appurtenances24. pump and pump control systems.25. Types of solids in the wastewater.26. Age (time in collection system) of wastewater

when it reaches the plant27. Rate of wastewater flow as compared to design

flow. 28. Mechanical conditions and cleanliness of clarifier.29. Proper sludge withdrawal30. Suspended solids