CT: Its Role in Surface and Groundwater Systems

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C-TIts Role in Surface and Groundwater Systems

• KY Water and Wastewater Operators Association
• 52nd Annual Conference
• March 23, 2009
• Department for Environmental ProtectionEnergy
  and Environment Cabinet

To Protect and Enhance Kentuckys Environment
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C-T Not a New Concept

• The C-T concept began with the original Surface
  Water Treatment Rule in 1991
• The Guidance Manual associated with this rule
  became the bible for C-Ts
• Now is applicable to
• groundwater systems
• (think Canada)

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What is C-T?

• C-T
• A measure of microbial disinfection efficiency
• To be effective, the microbe must be sensitive to
  a disinfectant
• Giardia, Legionella, bacteria, viruses (Whats
  Missing?)
• Components
• Concentration of disinfectant residual
• Retention Time
• Also relies on temperature, pH and flow

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Why is C-T Important?

• SWTR
• Requirements to meet 3-log Giardia and 4-log
  virus removal/inactivation
• In KY, a well-operated surface water plant is
  granted 2 log Giardia/virus removal credit
• The remaining logs must be met through
  disinfection
• ESWTR and LT1SWTR
• Any changes in disinfection practices requires a
  disinfection profile and benchmark
• Relies on 12 months of C-T data
• Attempts to balance disinfection with DBP control

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Why is C-T Important?

• Groundwater Rule
• If disinfection is provided (which is required in
  KY), a 4-log inactivation of viruses must be
  provided
• Groundwater systems will be required to meet
  daily C-Ts through a system-specific minimum free
  chlorine residual
• This will be determined through C-T evaluations
• This will be monitored and recorded continuously
  with an on-line analyzer

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Disinfection Profile and Benchmark

• Primarily applicable to surface water systems as
  disinfection practices can influence DBP
  formation
• Change in disinfection practices
• Type of disinfectant
• Change in feed point
• Change in dosage if significant (i.e., if
  reducing from a residual of 1 ppm to 0.2 ppm)
• The profile is the 12 months of C-T data
• The benchmark is the lowest monthly average of
  those 12 months
• Any change in disinfection should not lower the
  daily C-T to less than this benchmark

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Determining C-Ts

• Basic WTP information
• Plant diagram
• Basin/process sizes
• Clearwell levels
• Flow rates
• Basic water quality data
• Minimum disinfectant residuals
• Maximum pH levels
• Minimum temperature

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Plant Diagram--Example
Rapid Mix 166 Gallons Chlorine Added Alum

• Shows
• Volumes
• Flows
• Chemical Feed

Raw Water Pumps 350 GPM
Flocculator 8,455 Gallons
Sedimentation 100 Tubes 5,328 Gallons
Chlorine and Fluoride Added
Filters 69 sq. ft total 1,290 Gallons
Clearwell 200, 000 Gallons
High Service 350 GPM
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Plant Diagram--Example
To Distribution
Filters 8 9
New Clearwell
Old Plant
Sed Basin 1
2o Floc 1-2
Tubes
Filters 1 - 7
Old Clear well
Tubes
Sed Basin 2
1o Floc 6-7
2o Floc 3-4
Sed Basin 5
Sed Basin 3
Tubes
Sed Basin 4
Rapid Mix
70 flow
2o Floc 5
1o Floc 8-9
Zone 1 Old Plant through the old Clearwell Zone
2 New Plant through Filters 89 Zone 3 New
Clearwell
30 flow
New Plant
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Basin/Process Size

• Dont always believe the plans
• Go take an actual measurement
• Use actual operating depth of water in basins to
  calculate volume, not the depth of the wall
• If the process routinely maintains any
  sludge/residuals depth, subtract that depth out
• Measure the depth of water over the filters

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Clearwell Level and Volume

• Clearwells have a set total volume but the levels
  tend to fluctuate
• Calculate gallons per foot of depth
• For the total depth, use the highest operating
  depth, not the height of the clearwell walls or
  the overflow
• Determine the type of baffling present
• Baffling determines if adequate water flow and
  mixing is being achieved
• Prevents short circuiting and dead zones

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• Examples of Baffling Factors

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Top Views
0.3 Baffling
0.7 Baffling
In
In
Out
Out
0.5 Baffling
In
Out
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Top Views
0.3 Baffling
In
0.7 Baffling
In
Out
Out
In
0.5 Baffling
Out
In
Out
0.5 to 0.7 Baffling
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Top Views
Side View
0.1 Baffling
In
In and Out
Out
0.3 Baffling or verify with a tracer study
0.3 Baffling
In
Out
Out
In
0.7 Baffling
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Plant Flow Rates

• Raw Water flow rates are set by pumps
• Typically these are designed at 1 particular flow
  rate
• Once the water enters the plant, flow is
  influenced by the presence of multiples
• Multiple flocculators, basins, upflow units, etc
• Multiple filters
• Multiple clearwells
• Chances are very good that the flows are
  different if multiples are present
• The different rates need to be determinedespecial
  ly if dramatically different

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Water Quality Data

• To get a more accurate picture for C-Ts, the WTP
  must sample more than once a day
• Remember, the goal is to find maximum and minimum
  values over the course of the operating day
• This goes for clearwell depth as well

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All Disinfectants Are Not Created Equal

• Free chlorine is effective against Giardia and
  even more so against viruses
• Its pH dependent
• If you meet the 1-log inactivation for Giardia,
  the disinfection more than exceeds the 2-log
  needed for viruses
• Total chlorine (chloramines) is virtually
  inactive for Giardia and viruses
• Its not pH dependent
• Chlorine dioxide and ozone work well against both
  Giardia and viruses
• These are not pH dependent

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Worse Case Annual C-T

• Initially determine the worse situation if all
  the negatives came into play all at the same time
• Highest flow, lowest temperature
• Lowest residual, highest pH
• The thought is that if a plant can meet C-Ts
  under these adverse conditions, it can meet the
  C-Ts year around

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Annual Worse Case C-T Form
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• Calculating C-T

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Basic C-T Calculations

• The calculation is a string of multiplication and
  division
• Basic Formula
• Step 1 Capacity (gallons) / Flow (gpm)
  Detention Time (minutes)
• Step 2 Detention Time (minutes) x Baffling
  Factor Actual Detention Time (minutes)
• Step 3 Actual Detention Time (minutes) x
  Disinfectant Residual (mg/L) Calculated C-T

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Basic C-T Calculations

• Using the charts in the guidance manual or other
  sources, determine the Required C-T
• Note This is C-T not log at this point, just a
  number that represents Concentration x Time
• For Giardia there are several complex charts
• For viruses, the charts are simpler

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C-T Chart from the SWTR Guidance ManualGiardia
pH
Temperature
Chlorine Residual
Log
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C-T Giardia Chart -- Extrapolated
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Virus C-T Using Free Chlorine
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Going from C-T to Log

• And just what is a Log
• We arent talking timber here
• 1 Log is 90.00
• 2 Log is 99.00
• 3 Log is 99.90
• 4 Log is 99.99

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Going from C-T to Log

• For surface systems, remember all you need a
  l-Log inactivation for Giardia
• Calculated C-T/Required 1 Log C-T Log
  Inactivation
• If you meet the Giardia 1-log inactivation, your
  plant automatically meets the 4-log virus
  inactivation
• For groundwater systems, remember you need a
  4-log inactivation of viruses only
• (Calculated C-T/Required 4-Log C-T) x 4 Log
  Inactivation
• Since the GW Rule is looking for a comparison to
  4-Log inactivation, log math requires that you
  multiply by 4

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Surface Water Daily C-T Form
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Groundwater Daily C-T Form
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Thats Sure a Lot of Numbers

• Remember that microbial contamination causes
  acute (i.e. quick and fast) illness that can be
  deadly
• By assuring adequate disinfection the majority of
  microbial illnesses can be controlled
• The main goal in the public health industry

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C-T in the 21st Century

• Any new WTP or an expansion at an existing WTP
  means a new C-T evaluation is needed
• This is initially done during the plans review
  process
• Is done again when the plant/expansion is on-line
  to set up the Daily C-T form
• Groundwater systems should easily meet the 4-log
  virus inactivation with existing clearwellswith
  a few exceptions

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Groundwater Rule Challenges to C-T

• Groundwater systems with conventional
  clearwells are easy to evaluate
• Groundwater systems with bladder tanks or
  pressure tanks are a different story
• No way to easily get a volume measurement or
  clearwell level
• These tanks tend to cycle the water in and out
  depending upon external factors (such as pressure)

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Groundwater Rule Challenges to C-T

• If KY is not able to determine C-Ts for a system
• KY can require that those system conduct
  triggered source water monitoring based on any
  positive routine bacts
• Positive bact results in groundwater source
  testing for E.coli (fecal indicator)
• Require a tracer study of the non-conventional
  clearwell to determine C-T (long process)
• Or the system can install a conventional
  clearwell

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More Groundwater Rule ChallengesLocation,
Location, Location
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More Groundwater Rule Challenges

• The GWR is effective in December 2009
• The KY drinking water program had 2 staff that
  were handling the GWR in addition to staff in the
  groundwater section
• All 4 have moved onBut
• The good news is that the DWCTAS is in the
  process of hiring a GWR compliance officer and
  Jackie Logsdon is returning to Technical
  Assistance2 is better than nothing!

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More Groundwater Rule Challenges

• GW systems will have the big Sanitary Surveys
  that cover the 8 elements just like SW systems
• Will include both GW (131) and GWP (25)
• This is on top of the SW (150) and SWP (176)
  systems that must be done under the Surface Water
  Rules
• Initially done every 3 years if a community
  system or 5 years if non-community
• Can move a community system to a 5-year cycle if
  that system is outstanding or provides a 4-log
  inactivation of viruses
• May be considered but can become a tracking
  nightmare
• Significant deficiencies require a consultation
  with the state within 30 days of notification and
  a corrective action plan within 120 days
• KY must identify 1 significant deficiency for
  each of the 8 elements in order to have GWR
  primacy

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Groundwater Systems How to Prepare

• Begin more plant water quality sampling in
  preparation for C-Ts
• Gather compliance records in neat orderly fashion
• Update WHP and GWPP
• Computer capability
• Management and financial questions will be asked
  on the SS

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What to Remember

• Surface water systems
• Do your daily C-Ts and adjust treatment to meet
  the required 1 log inactivation
• If a new plant or upgrade, contact your Technical
  Assistance person for assistance in re-doing the
  C-Ts
• Groundwater systems
• Technical Assistance staff will be evaluating the
  groundwater producers for ability to meet a 4-log
  virus inactivation
• May be asking other technical assistance
  providers to help with these evaluations
• Provide advise to DOW on handling the
  bladder/pressure tanks

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Questions?? Comments??

• Presented by Julie W. Roney
• For Assistance contact
• Drinking Water Compliance and Technical
  Assistance Section
• Lastname.Firstname_at_ky.gov