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Dave Mercer, P.E. District Engineer DEQ
Disinfec(on Byproducts (DBPs): TTHMs and HAA5s • DBPs = compounds created when naturally occurring material in water react with the disinfectant used to treat the water
• TTHMs = Total Trihalomethanes: a group of DBPs regulated under the Stage 2 DBPR
• HAA5 = Haloacetic acids: a group of DBPs regulated under the Stage 2 DBPR
Precursor in Water Natural Organic MaAer
Bromide +Added Disinfectant
Chlorine
Chloramines
Chlorine Dioxide
Ozone
How Are DBPs Formed?
= TTHM (Total Trihalomethanes) HAA5 (Haloace(c Acids)
Chlorite
Bromate
DBP
How Are DBPs Formed? Natural Organic
MaAer +Added
Disinfectant = DBP Natural Organic
MaAer +Added
Disinfectant = DBP Natural Organic MaAer +
Added Disinfectant = DBP + Time
Disinfec(on Byproducts TTHM ! MCL = 0.080 mg/l (80 ppb) ! Chloroform ! Dibromochloroform ! Dichlorobromoform ! Bromoform
HAA5 ! MCL = 0.060 mg/l (60 ppb) ! Monochloroacetic acid ! Dichloroacetic acid ! Trichloroacetic acid ! Monobromoacetic acid ! Dibromoacetic acid
TOC ! Based on past 12 months of raw and finished water TOC data
! Determine performance ratio (% TOC actual removal versus required)
TOC Month TOC Raw Alkalinity Raw
TOC Finished
Req'd % Removal
Actual % Removal SUVA Ratio
Removal Ratio
04/13 3.6 17.35 1.1 35 68.55 — 1.96
05/13 3.3 19 1.3 35 61.7 — 1.76
06/13 4.2 16.9 1.8 45 57.2 — 1.27
07/13 5.3 14.9 2.4 45 55.9 — 1.24
08/13 5.7 18.1 2 45 64.3 — 1.43
09/13 5.2 20.1 2.9 45 44.8 — 1
10/13 4.9 15.3 2.5 45 48.9 — 1.09
11/13 4.7 16.8 2.8 45 40.6 — 0.9
12/13 5 18.2 2.7 45 45.5 — 1.01
01/14 5.2 14.6 2.7 45 47 — 1.04
02/14 4.9 14.2 2.1 45 57.6 — 1.28
03/14 3.3 15.5 1.6 35 51.2 — 1.46
Averages: 4.6 2.15 — 1.29
TOC Monitoring Points
Raw Water Clarifiers Filters Clearwell
Chemical Addition
Raw TOC Finished TOC
Prior to chemical addition No later than the CFE
Reducing Total Organic Carbon
Natural Organic MaAer
(measured as TOC)
+Added
Disinfectant = DBP
TOC – Coagula(on ! The removal of natural organic matter, measured as TOC, in a conventional water treatment by the addition of coagulant has been demonstrated by laboratory research and by pilot, demonstration, and full scale studies.
TOC Removal ! TOC plays a key role in DBP formation – even a small increase in TOC can lead to an increase in DBP formation!
! Removal of TOC occurs in most plants, but it may not be optimized!
Enhanced Coagula(on Enhanced coagulation can include one or more of the following operational changes: ! Increasing coagulant dose ! Changing coagulant ! Adjusting pH (using acid to lower the pH as low as 5.5) ! Improving mixing or applying moderate dosage of an oxidant or PAC
! Adding a polymer ! TOC should be 2.0 mg/L or less at the clarifier effluent
Jar Tes(ng ! Jar testing is a method of simulating a full-‐scale water treatment process, providing system operators a reasonable idea of the way a treatment chemical will behave and operate with a particular type of raw water.
! Nowadays, jar testing must include TOC analyses.
Jar Tes(ng ! It is important to simulate physical conditions such as mixing, detention times, and solids recycle in the jar test corresponding to those conditions in the full-‐scale water treatment plant.
Jar Tes(ng The jar testing process can be summarized as follows: ! For each water sample (usually raw water) a number of beakers (jars) are filled with equal amounts of the water sample;
! Each beaker of the water sample is treated with a different dose of the chemical;
! Other parameters may be altered besides dosage, including chemical types, mixing rate, pH, etc.;
! By comparing the final water quality achieved in each beaker, the effect of the different treatment parameters can be determined;
! Jar testing is normally carried out on several beakers at a time, with the results from the first test guiding the choice of parameter amounts in the later tests.
When should jar tests be performed?
Seasonally Daily, Weekly, Monthly
Change in chemical
Change in raw water
quality
New pumps
Change in flow
New mixer motor
pH adjustment
Cost Savings
Jar Test Equipment Overfeeding Underfeeding
$3,000 • Chemical Price • Delivery • Backwash Water • Residuals Disposal
• Disinfectant Price • Violations (public notice) • Consent Order (penalties)
Solids Contact Clarifier – Design ! 30 seconds rapid mix (no greater than) ! 30 minutes flocculation (no less than) ! 3 hours sedimentation (no less than)
Rapid Mix
Flocculation Flocculation
Sedimentation Sedimentation
Solids Contact Clarifier -‐ Design ! Need dimensions of each zone (where are those old plans?)
! Need flow through clarifier (gpm) 50 ft
12 ft
12 ft
8 ft
16 ft
2 ft
Example
Solids Contact Clarifier -‐ Design ! Determine rapid mix zone volume (gal)
! Volume of cylinder ! Determine flocculation zone volume (gal)
! Volume of frustum (V= π ·∙ ·∙ (R2 + Rr + r2)) ! Determine sedimentation zone volume (gal)
! Total volume minus flocculation zone volume
h
3
Ques(ons aIer reviewing design: ! Is the rapid mix rapid? ! Is the clarifier operating as designed (anything need to be repaired)?
! Can the flow through the clarifiers be slowed down? ! Is one clarifier being overloaded?
Chlorine Control
Natural Organic MaAer
(measured as TOC)
+Added
Disinfectant = DBP
Required Chlorine Residuals ! Maintain at the Point of Entry
! no less than 1.0 mg/L free chlorine ! no less than 2.0 mg/L total chlorine for chloramines systems
! no greater than 4.0 mg/L (RAA) free or total chlorine
! Maintain in the Distribution System ! System no less than 0.2 mg/L free chlorine
! System no less than 1.0 mg/L total chlorine for chloramines systems
OUT
Secondary Cl2 = 2 ppm
Cl2= 3.2 ppm
IN PUMP
Maximize CT – Minimize DBP’s Add the chlorine needed to achieve at least 0.5 log removal of Giardia, add the rest downstream.
Cl2= 1.2 ppm
POE Free Chlorine Residual Modifica(on
! The minimum free chlorine residual at the POE shall be at 1.0 mg/l. For supplies that document they meet or exceed the inactivation requirements in OAC 252:631-‐3-‐3(a)(1), the minimum free chlorine residual at the POE shall be 0.2 mg/l.
-‐ OAC 252:631-‐3-‐3(d)(2)
OUT
Secondary Cl2 = 2 ppm Cl2= 2.5 ppm
IN PUMP
Maximize CT – Minimize DBP’s Add the chlorine needed to achieve at least 0.5 log removal of Giardia, add the rest downstream.
Cl2= 0.5 ppm
Modification Potential Benefits Potential Issues
Enhanced Coagulation
• may improve disinfection effectiveness • can reduce bromate formation by reducing pH • can reduce DBP formation
• may adversely impact finished water turbidity • lower pH can cause corrosion problems • may see increased inorganics concentrations in finished water • issues with disposal of residuals
Decreasing pH • same inactivation can be achieved with lower disinfectant dose or shorter free chlorine contact time • lower pH may reduce some TTHMs
• may increase HAA5 • can adversely affect treatment plant equipment • may impact settling and sludge dewatering • can cause corrosion problems • may be difficult to maintain a residual
Moving the Point of Chlorination Downstream
• reduces DBP concentrations • reduces amount of disinfectant used
• May impact ability to meet CT requirements • provides less effective treatment for iron or manganese
Conclusion ! PWS will find improving and optimizing current operations is the best first step when making changes to achieve compliance. ! No major capital improvements. ! Operators are already familiar with the processes. ! Operational improvements could lead to less expensive or simpler technologies
! Adding new technology may not have the desired effect if existing technologies aren’t optimized.
Representative Ext. Kay Coffey 8145 (Manager) Shane Hacker 8108 Steven Hoffman 8143 (Team Leader; AWOP) Dawn Hoggard 8149 Dave Mercer 8147 Zach Paden 8106 Brian Schwegal 8105 Candy Thompson 8103 * District assigned by color code Administrative Assistant Ramona Haggins 8107
Interim *
Brian S.
Haskell
Latimer Le Flore
Choctaw McCurtain
Pushmataha
Bryan
Atoka
Kingfisher
Canadian Oklahoma
Blaine Logan
Public Water Supply Sec(on District Assignments (May 20, 2014)
Cleveland
Mcclain
Johnston
Stephens
Love
Carter
Garvin
Murray
Marshall
Zach P. Custer
Dewey
Major
Beaver Cimarron Harper Texas Woods
Woodward
Ellis
Roger Mills
Alfalfa Grant
Candy T.
Sequoyah
Cherokee
Creek
Mayes Rogers
Tulsa
Okmulgee
Wagoner
Muskogee
Hughes Pittsburg
Coal
Pontotoc
Garfield
Payne
Kay
Noble
Osage
Pawnee
Pottaw
atom
ie
Seminole
McIntosh Okfuske
e
Lincoln
Was
hing
ton
Adair
Craig
Delaware
Ottawa Nowata
Steven H.
Dawn H.
Jefferson
Tillman
Caddo
Comanche
Cotton
Greer
Jackson
Kiowa
Washita Beckham Grady
Dave M.
Shane H.
Interim *
Interim *
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