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C. T Calculation Math for Water Technology MTH 082 (pg. 468) Math for Water Technology MTH 082 (pg. 468) “Required by Law”

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Presentation on theme: "C. T Calculation Math for Water Technology MTH 082 (pg. 468) Math for Water Technology MTH 082 (pg. 468) “Required by Law”"— Presentation transcript:

1 C. T Calculation Math for Water Technology MTH 082 (pg. 468) Math for Water Technology MTH 082 (pg. 468) “Required by Law”

2 C. T calculation “C” is the concentration of chlorine, “T” is the amount of time the water has been in contact with chlorine before the first user. Calculated daily and compared against the EPA CT “Required” Table “C” is the concentration of chlorine, “T” is the amount of time the water has been in contact with chlorine before the first user. Calculated daily and compared against the EPA CT “Required” Table EPA rules states - “Measurements must be taken on the same day of the week, every week, for one year (52 measurements), during peak hourly flow for that day. Data can be measured manually or with on-line instrumentation.”

3 C. T Calculation Problems To calculate the contact time T, the results of a recent tracer study must be used!! The peak flow must be measured from the effluent side of the clearwell or contact chamber, NOT the flow through the plant. The chlorine residual, pH, and temperature values used to calculate CT must be measured at the effluent side of the clearwell or contact chamber, or before the first user. To calculate the contact time T, the results of a recent tracer study must be used!! The peak flow must be measured from the effluent side of the clearwell or contact chamber, NOT the flow through the plant. The chlorine residual, pH, and temperature values used to calculate CT must be measured at the effluent side of the clearwell or contact chamber, or before the first user.

4 CT Calculation Problems When using the EPA CT tables, make sure you round down for temperature, and round up for pH. log-reduction must equal 3.0 for Giardia When using the EPA CT tables, make sure you round down for temperature, and round up for pH. log-reduction must equal 3.0 for Giardia

5 For surface water systems without filtration, the Surface Water Treatment Rule requires public water systems to? 1.Provide coagulation and filtration 2.Maintain a C X T value above the minimum value 3.Continuously sample for total coliforms 4.Maintain public notification 1.Provide coagulation and filtration 2.Maintain a C X T value above the minimum value 3.Continuously sample for total coliforms 4.Maintain public notification

6 In the application of chlorine for disinfection, which of the following is not normally an operational consideration? 1.Mixing 2.Contact time 3.Dissolved oxygen 4.pH 5.None of these answers are correct 1.Mixing 2.Contact time 3.Dissolved oxygen 4.pH 5.None of these answers are correct

7 The chlorine residual, pH, and temperature values used to calculate CT must be measured at? 1.effluent side of the clearwell 2.effluent side of the contact chamber 3.before the first user 4.Any of the above would be ok 1.effluent side of the clearwell 2.effluent side of the contact chamber 3.before the first user 4.Any of the above would be ok

8 The C. T calculation must be calculated 1.Once a year 2.Once a month 3.Once a week 4.Once a day 1.Once a year 2.Once a month 3.Once a week 4.Once a day

9 The peak flow must be measured as total flow through the plant ? 1.True 2.False 1.True 2.False

10 The final C. T calculation has what units? 1.Mg/L 2.Lbs/day 3.mg-min/L 4.time 1.Mg/L 2.Lbs/day 3.mg-min/L 4.time

11 What is the acceptable log reduction for Giardia?

12 What is the acceptable log reduction for viruses?

13 Four log removal is? % % % % % % % %

14 If your temperature is 8 degrees with a pH of 7.2, you should use the ____ degree page and the _____ pH table (please look at your tables). 1.5, , , , 7 1.5, , , , 7

15 Disinfection CTs have been established for? 1.Free chlorine 2.Chloramine 3.Chlorine dioxide 4.Ozone 5.All of the above 1.Free chlorine 2.Chloramine 3.Chlorine dioxide 4.Ozone 5.All of the above

16 Disinfection C. T are impacted by which of the following? 1.Chlorine residual concentrations (mg/L) 2.Contact Time (min) 3.Water Temperature 4.Water pH 5.All of the above 1.Chlorine residual concentrations (mg/L) 2.Contact Time (min) 3.Water Temperature 4.Water pH 5.All of the above

17 T =contact time= Detention Time “the length of time water is retained in a vessel or basin ” C. T Calculation

18 The units of T in the final CT calculation are ? 1.Seconds 2.Minutes 3.Hours 4.Days 1.Seconds 2.Minutes 3.Hours 4.Days

19 Determining T in CT? Detention time (DT) = volume of tank = MG (1440min) flow rate MGD ( 1day) Want T value to be in minutes Detention time (DT) = volume of tank = MG (1440min) flow rate MGD ( 1day) Want T value to be in minutes T = volume X Baffle Factor (table) flow rate T = volume X Baffle Factor (table) flow rate

20 Baffle Factor? in out Poor circulation Baffling efficiency = 5-10% Poor circulation Baffling efficiency = 5-10% in out Poor circulation Baffling efficiency = 5-10% Poor circulation Baffling efficiency = 5-10% in out No circulation Baffling efficiency = 0% No circulation Baffling efficiency = 0%

21 Baffle Factor? in No circulation Baffling efficiency = 0% No circulation Baffling efficiency = 0% in out Good circulation Baffling efficiency = 30-50% Good circulation Baffling efficiency = 30-50% Superior circulation Baffling efficiency = 70% Superior circulation Baffling efficiency = 70% in out

22 Baffle Factor? Perfect circulation Baffling efficiency = 100% Perfect circulation Baffling efficiency = 100% Poor circulation/hydropneumatic tank Baffling efficiency = 10% Poor circulation/hydropneumatic tank Baffling efficiency = 10% No circulation/Bladder type pressure tank Baffling efficiency = 0% No circulation/Bladder type pressure tank Baffling efficiency = 0% inout in out

23 Baffle Factor? Unbaffled Tank0.1 Poor Baffling0.3 Average Baffling0.5 Superior baffling0.7 Pipe Flow1.0 “How well the chlorine is in contact with the water”

24 What is the average detention time in a basin that is 1240 ft 3 when the flow rate is 4.1 MGD? min min min 4.435,512 min

25 What is the average detention time in a basin given the following: diameter = 80' depth = 12.2' flow = 5 MGD min min min min

26 Determine T at the effluent side of a superior baffled contact chamber basin that has the following: diameter = 30' depth = 15' flow = 700 gpm min min 3.75 min min.

27 DRAW: Given: Formula: Solve: DRAW: Given: Formula: Solve: Determine T at the effluent side of a superior baffled contact chamber basin that has the following: Length of = 30ft, width of 20 ft, depth = 15' flow = 700 gpm? tank= L X W X D, Flow rate 700 gpm, BF=0.7 T= DT X BF T= volume of tank/flow rate X BF Vt= L X W X D Vt=30 ft X 20 ft X 15 ft= 9000 ft ft 3 (7.48 gal/1ft 3 )= gal DT=VT/FR X BF Time = 67,320 gal/700gpm X 0.7 Time= min X 0.7 Time= min tank= L X W X D, Flow rate 700 gpm, BF=0.7 T= DT X BF T= volume of tank/flow rate X BF Vt= L X W X D Vt=30 ft X 20 ft X 15 ft= 9000 ft ft 3 (7.48 gal/1ft 3 )= gal DT=VT/FR X BF Time = 67,320 gal/700gpm X 0.7 Time= min X 0.7 Time= min in 700 gpm out 30 ft 20 ft 15 ft min min min 4.9 min min min min 4.9 min

28 Disinfection CT Requirements Chlorine residual concentrations (mg/L) Contact Time (min) Water Temperature Water pH Disinfection power= [residual chlorine] time of its contact Chlorine residual concentrations (mg/L) Contact Time (min) Water Temperature Water pH Disinfection power= [residual chlorine] time of its contact

29 Disinfection CT Calculation CT= [ disinfection concentration mg/L] contact time (min) CT units= mg/L min or mg min/L Required CT CT required is # established by EPA to provide log inactivation. Based on Giardia cysts. Look up in charts Actual CT CT actual is # established by multiplying actual chlorine residual by hydraulic detention time and baffle factor. CT= [ disinfection concentration mg/L] contact time (min) CT units= mg/L min or mg min/L Required CT CT required is # established by EPA to provide log inactivation. Based on Giardia cysts. Look up in charts Actual CT CT actual is # established by multiplying actual chlorine residual by hydraulic detention time and baffle factor.

30 Disinfection CT Calculation CT actual =[Residual chlorine]hydraulic detention timebaffle factor (table) Hydraulic detention time = volume/flow rate CT act / CT req = ratio must be > or = to 1. CT act / CT req > 1.0 “You want to make sure that you are actually meeting the necessary requirements” CT actual =[Residual chlorine]hydraulic detention timebaffle factor (table) Hydraulic detention time = volume/flow rate CT act / CT req = ratio must be > or = to 1. CT act / CT req > 1.0 “You want to make sure that you are actually meeting the necessary requirements”

31 Disinfection CT Rules 1.Chlorine residuals used for CT calculations are measured after contact, but before first customer. 2. Contact times are determined by calculating the hydraulic detention time (HDT) as water flows through pipes and tanks. Based on highest flow of day. 1.Chlorine residuals used for CT calculations are measured after contact, but before first customer. 2. Contact times are determined by calculating the hydraulic detention time (HDT) as water flows through pipes and tanks. Based on highest flow of day.

32 Disinfection CT Rules 3. Water flowing through pipes provides contact times that are equal to the calculated HDT. Circular or rectangular tanks used for contact time are given only partial credit due to short circuiting.

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