1.)

A rapid mixing rate process must provide a minimum hydraulic residence time of 50 sec. The water

production rate is 0.70 MGD. Two identical tanks are provided in parallel. If the tanks are cylindrical with

a liquid depth equal to the radius, the minimum liquid depth (ft) is most nearly:

2.)

A lime soda softening plant produces a municipal supply of 7 MGD. The plant includes two clarifiers,

each with a diameter of 75 ft and sidewater depth of 14 ft. The clarifier residence time (hr) for parallel

operation is most nearly:-

3.)

A rapid sand filter has four cells with the following dimensions:

4.)

What is the most likely sequence of unit operations and processes for a surface water treat facility?

5.)

A lime soda softening filtration plant produces a municipal supply of 6.5 MGD. The plant includes six

filters of a surface area of 225 ft² per filter. The design filtration rate (gpm/ft²) with one unit offline is

most nearly:

6) A consulting engineer is performing a diagnostic evaluation of a 0.7-MGD water treatment plant. The

engineer is required to evaluate the existing chlorination system, which consists of two 150-lb cylinders.

Using a chlorine dosage of 4.5 mg/L, the number of days of disinfection the system will provide without

running out is nearly:

7.)

A 12.5-MGD water treatment plant is to be designed with eight identical rectangular clarifiers with

length-to-width ratio of 5:1. The clarifiers will be in parallel. If the clarifiers are 16 ft deep with a

horizontal velocity of 0.5 ft/min, the dimensions (ft) of each clarifier need to be most nearly:

8.)

A circular clarifier is being designed to receive a flow of 3.5 MGD. If the clarifier depth is 12 ft and the

detention time is 2 hours, the tank diameter (ft) is most nearly

9.)

With a design retention time of 1 min, dynamic viscosity of 2.735*10-5 lb-sec/ft2, and a velocity gradient

value of 700 sec, the power (ft-lb/sec) that must be imparted to 2 MGD of water passing through a rapid

mix unit is most nearly:

10) 20-ft x 40-ft dual media drinking water filter is to be cleaned using an air wash followed by & water

wash. The air wash is at a rate of 5 sefm/ft². The recommended airflow rate (scfm) for the air wash is

most nearly:

12.)

A typical primary clarifier is needed to remove 64% of the suspended solids of the treated water.

the flow rate is 1.5 cfs, what is the necessary surface area of the clarifier?

13.).

A filtration system is used to treat water. The water has a terminal settling velocity of 10 m/s, and the

porosity of the fluid bed is 0.1. At what velocity should the system be backwashed?

14.)

A turbulent flow impeller is used in a rapid mix water treatment system. If the turbine has 6 curved

Blades and operates at a rotational speed of 125 rpm, how much power is needed to run the turbine?

The diameter of the impeller is 0.3 m, the water density is 1000 kg/m³, and the flow is turbulent.