Presentation on theme: "Math for Water Technology MTH 082 (pg. 468)"— Presentation transcript:
1 Math for Water Technology MTH 082 (pg. 468) C.T Calculation“Required by Law”Math for Water TechnologyMTH 082(pg. 468)
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” TableEPA 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 calculationSurface Water Treatment Rule: all surface water and GWUDI systems require 99.9% (3-log removal) and/or inactivation of Giardia and 99.99% (4-log) removal of viruses through disinfection and treatmentGround Water Treatment Rule: If a system is fecal positive may be required to achieve inactivation of 99.99% (4-log) removal of viruses through disinfection and treatment
4 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.
5 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
6 For surface water systems without filtration, the Surface Water Treatment Rule requires public water systems to?Provide coagulation and filtrationMaintain a C X T value above the minimum valueContinuously sample for total coliformsMaintain public notification
7 In the application of chlorine for disinfection, which of the following is not normally an operational consideration?MixingContact timeDissolved oxygenpHNone of these answers are correct
8 The chlorine residual, pH, and temperature values used to calculate CT must be measured at? effluent side of the clearwelleffluent side of the contact chamberbefore the first userAny of the above would be ok
9 The C.T calculation must be calculated Once a yearOnce a monthOnce a weekOnce a day
10 The peak flow must be measured as total flow through the plant? TrueFalse
11 The final C.T calculation has what units? Mg/LLbs/daymg-min/Ltime
12 What is the acceptable log reduction for Giardia? 1234
13 What is the acceptable log reduction for viruses? 1234
14 Four log removal is?90.00 %99.00 %99.90 %99.99 %
15 If your temperature is 8 degrees with a pH of 7 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).5, 1910, 8.55, 7.510, 7
16 Disinfection CTs have been established for? Free chlorineChloramineChlorine dioxideOzoneAll of the above
17 Disinfection C.T are impacted by which of the following? Chlorine residual concentrations (mg/L)Contact Time (min)Water TemperatureWater pHAll of the above
18 T =contact time= Detention Time C.T CalculationT =contact time= Detention Time“the length of time water is retained in a vessel or basin ”
19 The units of T in the final CT calculation are ? SecondsMinutesHoursDays
20 Want T value to be in minutes Determining T in CT?Detention time (DT) = volume of tank = MG (1440min)flow rate MGD (1day)Want T value to be in minutesT = volume X Baffle Factor (table)flow rate
24 Baffle Factor? Unbaffled Tank 0.1 Poor Baffling 0.3 Average Baffling 0.5Superior baffling0.7Pipe Flow1.0“How well the chlorine is in contact with the water”
25 What is the average detention time in a basin that is 1240 ft3 when the flow rate is 4.1 MGD? 3.3 min.03 min303 min435,512 min
26 What is the average detention time in a basin given the following: diameter = 80' depth = 12.2' flow = 5 MGD132 min101 min144 min105 min
27 Determine T at the effluent side of a superior baffled contact chamber basin that has the following: diameter = 30' depth = 15' flow = 700 gpm65.8 min.79.1 min75 min.86.1 min.
28 96.17 min 67.32 min 12.85 min 9 min 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?DRAW:Given:Formula:Solve:tank= L X W X D , Flow rate 700 gpm, BF=0.7T= DT X BFT= volume of tank/flow rate X BFVt= L X W X DVt=30 ft X 20 ft X 15 ft= 9000 ft39000 ft3 (7.48 gal/1ft3)= galDT=VT/FR X BFTime = 67,320 gal/700gpm X 0.7Time= min X 0.7Time= minin700 gpmout30 ft20ft15 ft96.17 min67.32 minmin9 min
29 Disinfection C•T Requirements Chlorine residual concentrations (mg/L)Contact Time (min)Water TemperatureWater pHDisinfection power= [residual chlorine] • time of its contact
30 Disinfection C•T Calculation C•T= [disinfection concentration mg/L] • contact time (min)C•T units= mg/L• min or mg •min/LRequired C•TCTrequired is # established by EPA to provide log inactivation. Based on Giardia cysts. Look up in chartsActual C•TCTactual is # established by multiplying actual chlorine residual by hydraulic detention time and baffle factor.
31 Disinfection C•T Calculation C•T actual =[Residual chlorine]•hydraulic detention time•baffle factor (table)Hydraulic detention time = volume/flow rateC•Tact/ CTreq= ratio must be > or = to 1.C•Tact/ CTreq > 1.0“You want to make sure that you are actually meeting the necessary requirements”
32 Disinfection C•T Rules Chlorine residuals used for C•T 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.
33 Disinfection C•T 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.
34 Removal Credits Requirements Viruses Table 7.2: Typical Removal Credits and Inactivation Requirements for Various Treatment TechnologiesProcessTypical LogRemoval CreditsResultingDisinfection LogInactivationRequirementsGiardiaVirusesConventionalTreatment2.52.00.5DirectFiltration1.03.0Slow SandDiatomaceousEarth FiltrationUnfiltered4.0* Systems must demonstrate to the State by pilot study or other meansthat the alternative filtration technology provides the required logremoval and inactivation shown in Table 7-1.