Jambalaya
Only trained personnel should respond to a chlorine leak. All others in the area should ________.
Leave the area until it is deemed safe to return.
Determine the required chlorinator setting in lb/day given:
Steady flow rate of 5.5 MGD, Target chlorine residual = 2.5 mg/l, Average chlorine demand = 2.5 mg/l
(A) 229 lbs/day
(B) 251 lbs/day
(C) 195 lbs/day
(D) 213 lbs/day
(A) 229 lbs/day
Contact time varies from state to state. Most states require either 15 or 30 minutes at design average flow rate. Why is a minimum contact time so important for disinfection?
A. Chlorine gas is hazardous and has to be regulated.
B. To allow excess chlorine gas to dissipate.
C. To allow the chlorine time to inactivate the microorganisms.
Calculate the chlorine dosage required if it is desired to have a chlorine residual of 0.5 mg/L and the chlorine demand is 6.0 mg/L.
Chlorine Dosage = Chlorine Demand + Chlorine Residual
Chlorine Dosage = 6.0 mg/L + 0.5 mg/L
Chlorine Dosage = 6.5 mg/L
Which of the following conditions increases chlorine demand?
(A) Increase in organic matter
(B) Increase in alkalinity
(C) Increase in phosphate concentration
(D) Decrease in pH
(A) Increase in organic matter
Name 3 types of pathogenic organisms that can cause disease in a host.
Pathogenic organisms consist of bacteria, viruses, and cysts that can cause disease in a host.
A chlorine demand test will show the:
(A) Number of lbs required to kill 100% of coliforms (B) Amount of chlorine required to satisfy the biochemical oxygen demand
(C) Safe amount of chlorine that may be fed without killing fish
(D) Amount of chlorine required to give a desired residual after a given time
(D) Amount of chlorine required to give a desired residual after a given time
Compute the lagoons detention time. Surface area = 6.0 acres, Average depth = 3.0 ft, Average daily flow = 0.25 MGD
(A) 24 days
(B) 8 days
(C) 29 days
(D) 3 days
(A) 24 days
If chlorine costs $0.21/lb, what is the daily cost to chlorinate a 5 MGD flow rate at a chlorine dosage of 2.6 mg/l?
(A) $21.34
(B) $18.95
(C) $31.22
(D) $22.77
(D) $22.77
Calculate the chlorine demand given:
flow rate = 120 mgd; chlorine feed rate = 8000 lb/d; chlorine residual = 1.0 mg/l after contact time.
(A) 8 mg/L
(B) 6 mg/L
(C) 5 mg/L
(D) 7 mg/L
(D) 7 mg/L
Chlorine and its various forms are powerful oxidants that will kill most pathogenic organisms that are harmful to human and animal life. Name the typical forms of chlorine used in wastewater treatment.
Elemental Chlorine
Hypochlorite
Chlorine Dioxide
Chlorine applied minus ____ equals chlorine residual (A) Total chlorine
(B) Combined chlorine
(C) Chlorine demand
(D) Chlorine dose
(E) Free chlorine
(C) Chlorine demand
A 20-ft diameter clarifier with a depth of 8.25 ft receives a flow of 0.314 mgd. What is the detention time?
(A) 2.25 hours
(B) 1.48 hours
(C) 1.22 hours
(D) 1.75 hours
(B) 1.48 hours
How many pounds of chlorine/day should be dosed to a flow of 5.7 MGD if the chlorine demand for the secondary effluent is 7.8 and the desired residual is 0.3 mg/L?
Dosage = Demand + Residual
= 7.8 mg/L + 0.3 mg/L = 8.1 mg/L
= 5.7 MGD x 8.1 mg/L x 8.34 lbs/gal = 385 lbs/day
If you need a chlorine residual of 1 mg/l, how many pounds of chlorine must be applied each day if the flow is 2.5 mgd and the chlorine demand is 15 mg/l?
(A) 312 lb/d
(B) 419 lb/d
(C) 516 lb/d
(D) 334 lb/d
(E) 291 lb/d
(D) 334 lb/d
What compound is first formed when chlorine is applied to water?
(A) Chloramines
(B) Hydrochloric acid
(C) Free chlorine ions
(D) Hypochlorous acid
(D) Hypochlorous acid
Chlorine demand = _______ - chlorine residual.
(A) Breakpoint
(B) Dose
(C) Combined chlorine
(D) Free chlorine
(B) Dose
Compute the detention time in hours in a final clarifier given: Diameter = 95' Depth = 11' Flow rate = 7.0 MGD
(A) 1 hr. 55 min
(B) 2 hrs. 10 min
(C) 2.0 hrs
(C) 2.0 hrs
How many lbs of chlorine gas are required to treat 4,000,000 gal of wastewater at a dosage of 2 mg/l
(A) 65
(B) 69
(C) 61
(D) 67
(D) 67
The effluent chlorine demand is 12 mg/l, the target chlorine residual is 1.2 mg/l, and the plant flow is 5.6 MGD. How many lbs/day of 65% hypochlorite solution will be required?
(A) 948 lbs/day
(B) 776 lbs/day
(C) 113 lbs/day
(A) 948 lbs/day
As water temperatures decrease, the disinfecting action of chlorine:
(A) Remains the same
(B) Decreases
(C) Depends on the altitude
(D) Increases
(B) Decreases
If a 1-mgd plant has an effluent chlorine demand of 4.5 mg/l and maintains a residual of 1.0 mg/l, what is the estimated required chlorine feed rate in pounds per day?
(A) 51
(B) 46
(C) 38
(D) 68
(B) 46
Feed Rate, lbs/day = Flow (MGD) x Dosage (mg/L) x 8.34 lbs/gal
What is the average detention time in a clarifier given the following: diameter = 80' depth = 12.2' flow = 5 MGD
(A) 1.68 hrs
(B) 2.4 hrs
(C) 2.2 hrs
(C) 2.2 hrs
How many pounds of chlorine will be used in one day if the flow is 700,000 gal/d and a uniform dose of 1.2 mg/l is applied?
(A) 70.1 lb
(B) 698.3 lb
(C) 7.0 lb
(D) 7005 lb
(C) 7.0 lb
In a conventional activated sludge plant, oxygen demand is highest
(A) At the head end of the tank
(B) In the middle of the tank
(C) At the outlet of the tank
(D) Nowhere, oxygen demand is uniform throughout the tank
(A) At the head end of the tank