So Ive Found High DBPs: What Now

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So Ive Found High DBPs What Now

• Presented at
• KWWOA 50th Annual Conference
• Louisville, KY
• March 27, 2007

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So the IDSE Found High DBPs

• This is to be expected
• The IDSE focused on areas in the distribution
  system that would have high DBPs
• Little to no chlorine residual
• High water age
• Influenced by tanks
• Etc, etc, etc
• But EPA gives systems 3 years to get the DBPs
  under control before the locational running
  annual average kicks in

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Quick Review How Do DBPs Form?

• DBPs form as a result of a disinfectant reacting
  with organics
• Example Free chlorine TOC DBPs
• Example Ozone Bromide Bromate
• Example Chlorine Dioxide TOC Decay
  Chlorite
• The reaction itself is dependent upon
• Time
• Temperature
• Water quality parameters such as pH

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Quick Review Where Do DBPs Form?

• Blame it on the source water
• Surface water has higher organic content (TOC)
  than groundwater
• Reservoirs (or impoundments) usually have higher
  TOC than flowing streams
• Protected watersheds may have lower TOC levels
  than less protected ones
• In other states, highly colored waters have very
  high TOCs
• Florida with tannic lakes have source water TOCs
  over 10 mg/L

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Quick Review Where Do DBPs Form?

• Blame it on the source water
• Higher water temperatures make the TOC chlorine
  DBP reaction go faster
• Summer and early fall in KY have the higher water
  temperatures and thus the higher DBPs

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Quick Review Where Do DBPs Form?

• Blame it on the water plant
• Water plant operations
• Disinfection practices
• Coagulation/flocculation/sedimentation process
  operation
• Start-stop operations can result in water that
  sits in sedimentation basins or clearwells for
  extended periods of time
• Time can increase the TOC chlorine DBP
  reaction

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Quick Review Where Do DBPs Form?

• Blame it on the water plant
• Water plant maintenance
• Excessive sludge/residuals in sedimentation
  basins could contribute TOC within the plant
• Algae in sedimentation basins can also contribute
  TOC through by-products or when they die off

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Quick Review Where Do DBPs Form?

• Blame it on the distribution system
• Water age
• Tanks are primary culprits in increasing DBPs
• Number Too many can increase water age when
  compared to WTP production and consumer usage
• Size Large/oversized tanks can increase water
  age when compared to WTP production and consumer
  usage
• Location Water moving through multiple tanks
• Type Standpipes have the most issues
• Inlet/Outlet configuration Common inlet/outlets
  use the last in-first out concept
• Mixing Very critical and related to inlet
  velocity

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Quick Review Where Do DBPs Form?

• Blame it on the distribution system
• Water line extensions/oversized mains
• Extending lines over many miles to serve very few
  customers
• Oversized mains to future growth areas can
  result in long skinny horizontal mains in the
  ground
• Dead ends
• Distribution systems that have numerous dead ends
  have numerous ends that could have high water age
• Booster chlorination
• Adds more chlorine to the TOC chlorine DBPs
  equation to make more DBPs

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Quick Review Where Do DBPs Form?

• Blame it on the distribution system
• Distribution system operations and maintenance
• No or incorrect system-wide flushing
• Tanks are not inspected and cleaned regularly
• No working cross-connection control program
• Booster chlorination just because its always been
  used
• Corrosion control practices
• As you can see, DBPs are becoming a distribution
  system issue

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DBP Control

• We have the how and the where of DBP formation
• Now we need some solutions

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DBP Control Source Water and Reactions

• The How of DBP formation
• Cant control temperature
• May not be able to control source water
• Surface versus ground
• Source water quality
• Produce versus purchase
• Can look at
• Different intake levels
• Balancing one source against another (if more
  than one source)
• Surface or ground
• Reservoir or river
• One producer or another (for purchasing systems)

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DBP Control Water Plant

• The water plant has been the primary focus of
  Stage 1 with the TOC requirements for surface
  water systems
• TOC requirements remain in Stage 2
• TOC removal is still key
• TOC removal is an art, not a science
• The more TOC in the source water the easier it is
  to remove in the coagulation/flocculation/sediment
  ation process
• The more alkalinity in the source water the more
  difficult it is to remove through treatment
• The lower the treated water pH the more easily it
  becomes to remove TOC

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DBP Control Water Plant

• Improving TOC Removal
• Optimize the entire coagulation process (enhanced
  coagulation) for TOC removal
• Consider lowering the coagulation pH
• But be careful, low pHs encourage HAA formation
• Lower the pH with acid addition, more alum/ferric
  or acidified coagulants
• Although PACls are great for turbidity they dont
  suppress the pH and therefore dont do much for
  TOC removal
• Try powdered activated carbon (PAC)
• TOC removal usually takes more PAC than for taste
  and odor control (can be as high as 20 mg/L)
• Balance with sludge production, cost

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DBP Control Water Plant

• Disinfection practices play a key role in DBP
  formation
• Simply reduce the amount of disinfectant added
• Reducing pre-chlorine dosages and increasing post
  will help
• As TOC is removed, the demand for disinfectant in
  the plant should decrease
• Could result in lower post-disinfection dosages
• Remember to meet C-Ts
• Move the point of pre-chlorination to further in
  the flocculation/sedimentation process
• KY has seen success with this in reducing HAAs
• There are stipulations that must be followed to
  move the point of pre-chlorination

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DBP Control Water Plant

• Disinfectant practices (continued)
• Change disinfectants
• However, almost all disinfectants make some kind
  of by-product
• Example Chlorine dioxide makes chlorite
• Example Ozone makes bromate
• Example Chloramines make NDMA (not yet
  regulated but is part of the UCMR 2 monitoring)
• Example UV (no known by-products yet and leaves
  no residual)
• Chlorine dioxide and ozone are pre-disinfectants
• Chloramines and UV are primarily
  post-disinfectants
• Permanganate provides limited disinfection and no
  C-T credit

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DBP Control Water Plant

• Disinfectant practices (continued)
• Change disinfectants (continued)
• Balance the by-products, water quality issues
  (such as nitrification with chloramines) with
  decrease in DBPs
• Example In KY chlorine dioxide does not seem to
  reduce HAAs but is good for THM reductions
• Example Chloraminated water should not mix with
  free chlorinated water (water goes through the
  breakpoint chlorination process and may result in
  no chlorine residual at all)
• An issue with purchasing systems
• Must have DWB approval to change disinfectants
• Must still meet C-Ts in the plant and have a free
  or total distribution system residual

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DBP Control Water Plant

• Water Plant Operations and Maintenance
• Strongly consider 24/7 plant operations
• Reduces time at the plant that the water sits in
  contact with chlorine
• Optimize settled water turbidity
• Lower settled water could translate to higher TOC
  removals
• Evaluate sludge/residual management
• Cover basins to reduce algal growth
• Dont recycle

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DBP Control Distribution System

• Water Age and Storage Tanks
• Increase tank turnover the less time in the
  tank the less time to react further with the
  chlorine and make more DBPs
• Monitor tank levels
• Control tank levels
• Evaluate the flow of water from one tank to
  another
• Evaluate the number and size of tanks
• Too many tanks can cause the water plant to
  operate less and thus create operational and
  water quality problems at the plant
• Too many tanks increased water age

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DBP Control Distribution System

• Water Age and Storage Tanks (continued)
• Model the distribution system flow
• Hydraulic model
• Tracer study
• Evaluate valve operation practices
• Open some, close others to facilitate good flow

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DBP Control Distribution System

• Water Age and Storage Tanks (continued)
• Physical Structure
• Consider a tank type other than a standpipe
• These are commonly used for pressure not storage
• Most are tall and skinny and water warms up
  quickly
• Common inlet/outlet configuration
• Last in-first out
• May encourage temperature stratification
• Mixing within the tank
• Studies have shown that mixing is critical to
  overcoming some water quality issues
• Inlet velocity
• Mixing systems

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DBP Control Distribution System

• Water Lines, Mains and Dead End Areas
• We do need to get safe potable water to everyone
  and
• It is hard to guess at population and industry
  growth but
• Be aware that water quality will suffer if usage
  is low (i.e. water age is high)
• Flushing Either with manpower or automatic
  flush hydrants
• Looping of mains and tanks
• Be careful not to create hydraulic dead ends
  where water in different directions meet and
  dont flow

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DBP Control Distribution System

• Booster Chlorination
• Take a good look at whether booster chlorination
  is still needed
• Can chlorine residuals be maintained by
  better/more flushing?
• Loop lines
• Evaluate if the booster station should be moved
• For safety and security purposes, evaluate the
  need for gaseous chlorine

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DBP Control Distribution System

• Distribution System Operation and Maintenance
• Implement a flushing program
• From the water plant/master meter out
• Base how long to flush on water quality (such as
  chlorine residual)
• Clean and inspect tanks
• Broken/missing vent or overflow screens can allow
  creatures into the tankcreatures contain TOC and
  create a chlorine demand
• Any sediment can be stirred up during the
  fill/empty cyclesthe sediment may contain TOC

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DBP Control Distribution System

• Distribution System Operation and Maintenance
• Develop a cross-connection program
• Any organic introduced into the distribution
  system can react with chlorine to form
  by-products
• With the water plant, evaluate corrosion control
  strategies
• Anything that can clean up a distribution system
  without other adverse consequences can be
  considered
• Cleaner distribution systems require less
  disinfectant and so may lower DBPs
• Phosphates versus pH adjustment (lime or caustic)

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DBP Control Human Factor

• DBPs can be formed in both the water plant and
  the distribution system
• Solving DBP problems should be a joint effort
• Distribution and production
• Producer and purchaser
• Distribution system evaluations and improvements
  will be most critical in purchasing systems

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DBP Control Human Factor

• DBP testing is costly and the solutions can be
  even more soThis will be managements area of
  concern
• Work to budget the costs
• THM Plus versus actual THM/HAA testing
• Plan for the future (5, 10, and 15 year planning)
• New or re-engineered tanks
• Looping mains to eliminate dead ends
• Replacing mains
• New sources
• New chemical feed/disinfection

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Questions?? Comments??

• Julie W. Roney
• Julie.Roney_at_ky.gov
• www.water.ky.gov/dw
• www.epa.gov/safewater/disinfection/stage2