13. Filt Dissolved solids a. b. Colloidal solids c. Suspended solids d. Volatile

Question

13. Filt Dissolved solids a. b. Colloidal solids c. Suspended solids d. Volatile solids 14. Polymers aid in chemical coagulation primarily by what me a. Charge neutralization b. E c. Adsorption and interparticle bridging d. Zeta potential enhancement nmeshment in a precipitate mechanism? 15. The primary ind cator of mixing intensity in a flocculation basin is: a. Backmix factor b. Destabilization gradient c. Mixing intensity factor d. Velocity gradient 16. The e settling of discrete particles in water is known as: a. Type 1 settling b. Type 2 settling c. Differential settling d. Zone settling settlin g of a concentrated suspension of floc particles in water is known as a. Type 1 settling b. Type 2 settling c. Differential settling d. Zone settling 18. The parameter that primarily determines the surface area of a settling basin is: a. Weir overflow rate b. Surface overflow rate c. Horizontal water velocity d. System loading rate 19. At a surface water treatment plant, headloss monitoring typically would be done on the: a. Rapid mix basin b. Flocculation basin c. Sedimentation basin d. Filters e. All of the above 20. The filter that typically is operated at the highest filter loading rate is: a. Rapid sand filter b. Dual media filter c. Mixed media filter d. Deep bed filter

Explanation / Answer

13) The answer   is C.Water flows through a filter designed to remove particles in the water. The filters are made of layers of sand and gravel, and in some cases, crushed anthracite. Filtration collects the suspended impurities in water and enhances the effectiveness of disinfection. The filters are routinely cleaned by backwashing.

14)The answer   is A. In water treatment, coagulation flocculation involves the addition of polymers that clump the small, destabilized particles together into larger aggregates so that they can be more easily separated from the water. Coagulation is a chemical process that involves neutralization of charge whereas flocculation is a physical process and does not involve neutralization of charge. The coagulation-flocculation process can be used as a preliminary or intermediary step between other water or wastewater treatment processes like filtration and sedimentation. Iron and aluminium salts are the most widely used coagulants but salts of other metals such as titanium and zirconium have been found to be highly effective as well.

15)The answer   is C and D.optimum performance is achieved by reducing the intensity of mixing as the water proceeds through flocculation (known as tapered or staged flocculation). Engineers have developed methods of determining appropriate stir rates, called “mixing intensity values” or “velocity gradient” abbreviated as the letter “G.”

16)The answer   is A.

•settling of discrete particles in dilute suspensions.

•particles have no tendency to flocculate.

•they settle as individual entities and there is no significant interaction with neighboring particles.

17)The answer   is D.Hindered or Zone settling –The mass of particles tends to settle as a unit with individual particles remaining in fixed positions with respect to each other.

18)C

19)B

20)A

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