Dave Mercer, P.E. District Engineer DEQ

Transcription

1 Dave Mercer, P.E. District Engineer DEQ

2 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

3 How Are DBPs Formed? Precursor in Water Natural Organic MaAer Bromide Added Disinfectant + Chlorine Chloramines Chlorine Dioxide Ozone = TTHM DBP (Total Trihalomethanes) HAA5 (Haloace(c Acids) Chlorite Bromate

4 How Are DBPs Formed? Natural Organic MaAer + Added Disinfectant = DBP Natural Organic MaAer + Added Disinfectant = DBP Natural Organic MaAer + Added Disinfectant + Time = DBP

5 Disinfec(on Byproducts TTHM! MCL = mg/l (80 ppb)! Chloroform! Dibromochloroform! Dichlorobromoform! Bromoform HAA5! MCL = mg/l (60 ppb)! Monochloroacetic acid! Dichloroacetic acid! Trichloroacetic acid! Monobromoacetic acid! Dibromoacetic acid

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7 TOC! Based on past 12 months of raw and finished water TOC data! Determine performance ratio (% TOC actual removal versus required)

8 TOC Month TOC Raw Alkalinity Raw TOC Finished Req'd % Removal Actual % Removal SUVA Ratio Removal Ratio 04/ / / / / / / / / / / / Averages:

9 TOC Monitoring Points Raw Water Clarifiers Filters Clearwell Raw TOC Chemical Addition Finished TOC Prior to chemical addition No later than the CFE

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11 Reducing Total Organic Carbon Natural Organic MaAer (measured as TOC) + Added Disinfectant = DBP

12 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.

13 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!

14 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

15 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.

16 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.

17 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.

18 When should jar tests be performed? Seasonally Change in chemical ph adjustment Change in raw water quality New pumps Change in flow Daily, Weekly, Monthly New mixer motor

19 Cost Savings Jar Test Equipment Overfeeding Underfeeding $3,000 Chemical Price Delivery Backwash Water Residuals Disposal Disinfectant Price Violations (public notice) Consent Order (penalties)

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21 Solids Contact Clarifier Design! 30 seconds rapid mix (no greater than)! 30 minutes flocculation (no less than)! 3 hours sedimentation (no less than) Sedimentation Rapid Mix Sedimentation Flocculation Flocculation

22 Solids Contact Clarifier - Design! Need dimensions of each zone (where are those old plans?)! Need flow through clarifier (gpm) 12 ft 50 ft 2 ft 12 ft 8 ft 16 ft Example

23 Solids Contact Clarifier - Design! Determine rapid mix zone volume (gal)! Volume of cylinder! Determine flocculation zone volume (gal)! Volume of frustum (V= π (R 2 + Rr + r 2 ))! Determine sedimentation zone volume (gal)! Total volume minus flocculation zone volume h 3

24 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?

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26 Chlorine Control Natural Organic MaAer (measured as TOC) + Added Disinfectant = DBP

27 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

28 Maximize CT Minimize DBP s Add the chlorine needed to achieve at least 0.5 log removal of Giardia, add the rest downstream. OUT PUMP IN Secondary Cl 2 = 2 ppm Cl Cl ppm 2 = 1.2 ppm

29 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: (a)(1), the minimum free chlorine residual at the POE shall be 0.2 mg/l. - OAC 252: (d)(2)

30 Maximize CT Minimize DBP s Add the chlorine needed to achieve at least 0.5 log removal of Giardia, add the rest downstream. OUT PUMP IN Secondary Cl 2 = 2 ppm Cl Cl 2 = 2 = ppm

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32 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

33 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.

34 Public Water Supply Sec(on District Assignments (May 20, 2014) Steven H. Cimarron Texas Beaver Harper Interim * Woods Alfalfa Grant Kay Dave M. Washington Nowata Craig Ottawa Delaware Osage 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 Woodward Ellis Dewey Roger Mills Custer Dawn H. Washita Beckham Greer Kiowa Jackson Tillman Major Blaine Caddo Comanche Cotton Zach P. Kingfisher Canadian Grady Garfield Jefferson Logan Oklahoma Noble Cleveland Mcclain Garvin Pontotoc Payne Interim * Lincoln Pottawatomie Seminole Interim * Hughes Coal Pawnee Okfuske e Cree k Pittsburg Atoka Tulsa Okmulgee McIntosh Rogers Wagoner Muskoge e Haskell Latimer Pushmataha Mayes Cheroke e Candy T. Sequoyah Le Flore Adai r Stephens Shane H. Murray Johnston Carter Marshall Love Bryan Choctaw Brian S. McCurtain