Automated CT Study Template

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					Automated CT Study
Presented by: Sam Turner
 Technical Review & Oversight Team
    Public Drinking Water Section

  Public Drinking Water Conference
          August 9-10, 2005
Why Should I Hang
Around For This?
         CT Study Letter
! Every surface water treatment plant must
  have a CT study approval letter on file to
  document that:
 <Current disinfection process has been
 <The facility has the correct information for
  their SWMOR (pages 4 & 5)
  What Does “CT” Mean ?
! “C” refers to concentration
! “T” refers to contact time as T10
! “CT” amount of time disinfectant remains
  in contact with the water
    What Does T10 Mean?

-Estimate of how long the disinfectant will
to be in contact with the water in a treatment

-T10 = detention time x Baffling Factor
       CT Study Letter

! Purpose for new CT letter
! Identifies disinfection zones
! Determines contact time T10 in zones
! Information for SWMOR
 CT Study Letter Elements
! Changing the type of disinfectant
! Moving the point of disinfectant addition
  or monitoring
! Changing physical facilities
! Changing approved capacity of plant
! Other significant changes that would
  affect contact time of disinfectant
We are in receipt of your letter dated October 14,
2003, requesting a revised CT study to reflect the
modifications to the H 2 O Water Treatment Plant
(WTP). According to this letter you are requesting
the change in the disinfection process from free
chlorine to the use of chlorine and liquid
ammonium sulfate. In addition two of the four
clarifiers are also permanently being taken out of
service. Based on our review, we are approving the
CT study. The information in this letter will
replace, not supplement the CT study dated
November 14, 1994.
 CT Study Letter Elements
               Plant Description

! Flow Path
 <Description of the units
 <Flow pattern
! Disinfection Protocol
 <Types of disinfectants used
 <List of injection points
 <List of monitoring points
   Plant Description Example
The H2O WTP has a raw water pump capacity of
0.52 mgd (360 gpm). The WTP contains two
clarifiers, four gravity filters, and one clearwell.
The disinfection protocol involves injecting free
chlorine upstream of the clarifiers .
The LAS is injected prior to the clearwells.
Chlorine residual is monitored downstream of the
clarifiers and downstream of the filters. Chloramine
residual will be monitored at effluent of the
        Letter Elements...
               Disinfection Zone
A disinfection zone is a segment of the
treatment process which begins at a
disinfectant application point and ends at the
subsequent disinfectant monitoring point.
Each application point, regardless of the
frequency of use, represents the beginning of
a separate zone.
      Disinfection Zones
                Divided by

! Treatment units and piping
! Treatment Trains -no common header
! Filters -usually a separate zone
! Disinfection injection points
! Disinfection monitoring points
         Letter Elements
      Table 1: T10 Calculation Information

!   Unit Volumes (gallons)
!   Flow Rate (gpm or MGD)
!   Baffling Factor
!   T10 (minutes)
Table 1: T10 Table for H20 WTP


                                       (2)                     (5)

                                       (3)                     (6)

                                       (4)                     (8)

 (1) Capacity is based on....
     Operation at this flow rate does not meet required.....
     Other specific information
 (2) Dimensions, assumptions, references
 (3) Etc.....
            Letter Elements
         Table 2: SWMOR Parameters

! Flow Rate (MGD)
! T10 (minutes)
! Log Inactivations for
            Table 2: Disinfection
             Process Parameters

                                                       PERFORMANCE STD

                            Disinfection Zones          Log Inactivation
                      D1     D2      D3      D4   D5    Giardia     Virus

Flow Rate (MGD)      0.5    0.25     1.0    NA    NA
                                                         0.5         2.0
T10 Time (minutes)   43.2    10.1   36.0    NA    NA
 Quote from Jack Schulze
    “A CT Study Approval Letter is NOT:
! A plan approval letter
! A letter approving an alternate
  capacity requirement
! The approval to apply chloramine,
  chlorine dioxide, ozone or any other
             It is not...

! An exception letter
! Or anything else
! Unless the letter EXPLICITLY
  says so!!!
    Automated CT Study
     How a small SWTP can save $9000

! Update CT study
! Xcel worksheet
! Do not need consulting firm
! On TCEQ website
     Automated CT Study

! Intended for small & medium size

! Designed for WTP with no more
  than 10 disinfection zones
     Automated CT Study
         Download Template from:
! :
! Utilities & Water Supplies >PDW > DW
  Publications > Forms> SW or GUI >
  Contact Time (CT Template)
! Or call 512/239-4691
   Contents of Template

! Description
! Schematic
! T10 Details
! Summary
! Calculator
T10 Details
              CAPACITY OF
              THE PLANT !!!
  Submitting Your CT Study

! Print, sign, and submit template
! Include cover letter
! Mail to:
            Problem # 1
The water flows to a solids-contact
clarifier. Settled water is transferred to
two gravity filters by two 250-gpm
pumps. After filtration, water flows to
two 42,000 gallon clearwells.
The disinfection protocol involves pre-
chlorination in the clarifiers and
post- chlorination in the clearwells.
                    Problem # 1
Divide Disinfection Zones
Label: Injection Pts. (I1,I2, I3)
Monitoring Pts. (M1,M2,M3)

             Filters are identical and
             flow is evenly split
            Problem # 2
The WTP will be a 8.25 MGD facility. It will
treat raw water from the Rio Bigo River. The
facility has two 4.25 gpm raw water pumps,
two four-stage flocculation basins, two
sedimentation basins, two disinfection
contact chambers, four dual-media gravity
filters, and two 2.0-MG clearwells. The
clearwells are in series.
          Problem # 2

Hint: 5 - Inj. Pts & 7 - Mon. Pts.
       Problem # 1

Clarifier receives disinfectant
Clearwells receives disinfectant
             Problem # 1
     D1                  D2                 D3

                                       I3        M3
I1    M1

      Filters are identical and
      flow is evenly split
           Problem # 2

! Four disinfection zones
! Five disinfection injection points
! Seven disinfection monitoring
! Three trains

I1               I3
            M1               M3     M5 I 5


            M2               M4         M6
I2                I4
   Do You Want To Know
! CT Instruction Manual
! If you want to talk with a “live person”:

  <   Jack Schulze 512-239-6046
  <   Amrit Jhanji 512-239-4729
  <   Sam Turner 409-899-8798
  <   Cindy Bronnenberg 512-239-3465