Chloramines 101. Outline of Webinar

Transcription

1 1 Chloramines 101 Texas Section AWWA & TCEQ 1 Outline of Webinar istory and Overview Pros and Cons of Using Chloramines Chemistry of Chloramines Regulatory and Process Management Monitoring Dosing, Boosting, and Blending 2 1

2 Outline of Webinar istory and Overview Pros and Cons of Using Chloramines Chemistry of Chloramines Regulatory and Process Management Monitoring Dosing, Boosting, and Blending 3 4 istory: Chloramines have been used successfully for ~100 years. Overview: Chloramines are currently used successfully throughout Texas and the US. 4 2

3 5 istory Chloramines were identified in the early part of the last century ~1900s Source water for potable water was often impacted by untreated or poorly treated wastewater. Wastewater contained high levels of ammonia, for example, urea. Chlorinating high-ammonia water showed unexpected total chlorine results. Monitoring with orthotolidine could only measure total chlorine, not separate chlorine species. 5 Breakpoint curve discovery Adding chlorine to water with ammonia in it does not act like you think it should. Measured Residual (mg/l) Total Chlorine = Sum of active chlorine species 1:1 NO ammonia in water you add chlorine to Ammonia in the water that you add chlorine to Chlorine added to water (~2: N3-N Ratio) 6 3

4 7 istory Discovery of the breakpoint curve phenomena was enough to allow treatment. By the 1930s, research identified the chemicals that make up total chlorine, and chloramination could be controlled. istorically, public water systems (PWSs) used chloramines to keep a stable residual. For example, the City of Austin started chloraminating in the 1950s. 7 8 Chloramination increased Later, systems started using chloramines for trihalomethane (TM) control. Total TM Rule in the late 80s and thru the 90s Most systems > 100,000 converted Stage 1 Disinfection Byproducts Rule (DBP1) 2002 for large (over 10K), 2004 for small DBP2 Systems were phased in by size; all systems are now regulated under DBP2. 8 4

5 Today, about 1,200 of Texas s 7,000 PWSs distribute chloramines About 90% of 350 PWSs with surface water treatment plants (SWTPs) chloraminate PWSs purchased water systems + several groundwater PWSs in northeast Texas. Technology and best practice have progressed over the last 100 years. We have learned that chloramination can be a very successful disinfection strategy New rules cover most chloramine use In July 2015, new TCEQ rules streamlined use of chloramines for public water systems. All PWSs using chloramines had previously needed site-specific exception approval. (Like a permit. ) The new rule eliminated exception requirements and standardized monitoring, etc. owever, systems blending chloraminated and chlorinated sources must have an approved exception from the TCEQ 10 5

6 11 istory: Chloramines have been used successfully for ~100 years. Overview: Chloramines are currently used successfully throughout Texas and the US Outline of Webinar istory and Overview Pros and Cons of Using Chloramines Chemistry of Chloramines Dosing, Boosting, and Blending Regulatory and Process Management Monitoring 12 6

7 13 Pros: Chloramination pros outweigh cons for systems that have source water with high organic carbon and/or very long water age. Cons: Chloramination cons outweigh pros for systems that can operate with free chlorine Pro: Long-lasting residual Monochloramine is more chemically stable than chlorine. Remains active in water longer, can kill pathogens in pipe biofilms (legionella). Residual levels hold longer in hot climates. Ideal for warmer states with miles of distribution pipe. 14 7

8 Pro: Long-lasting residual Under good conditions, chloramine residuals can last for weeks. Free chlorine residuals may last up to a week. Water age in distribution can vary from days to weeks. igh water age can occur in: Large rural systems. Systems with large storage tanks. Areas with low usage. 15 Chloramine residual lasts weeks. The chloramine residual lasts longer at high p. 16 8

9 Chloramine persistence simulator EPA Office of Research and Development (ORD) provides chloramine simulators online: General Chloramine Chemistry Application: usepaord.shinyapps.io/unified-combo/ This tool can be used to calculate the ideal chloramine residuals attainable, and see the impact of changes in water quality. For example, p Pro: Less regulated DBPs Chloramines produces fewer harmful regulated disinfection byproducts than free chlorine: Trihalomethane (TM) and aloacetic acid (AA). Chloramination is a cost-effective alternative for reducing DBP formation. It is listed as a Best Available Technology for consecutive systems serving <10,ooo population in the DBP2 rule. 18 9

10 Con? Do chloramines smell bad? Chloramines smell fine unless they are dosed or maintained wrong. Some web sites say that chloramines smell bad. Monochloramine the disinfectant species smells a bit like chlorine. Di- and tri-chloramine stink. But they are not present when treatment is done right. Web sites devoted to pools identify that the smell of di- and trichloramine indicate a problem Con? Do they cause illness? Chloramines do not cause direct health issues. Some web sites blame various symptoms on chloramines, but there is no science (epidemiology) showing any adverse impacts to humans from drinking chloraminated water. This research is summarized in the DBP rule preambles. Old dialysis units (ca. 1980) are sensitive to chloramines. Fish are quite sensitive to chloramines

11 21 Con? What about NDMA? Chloramines have been linked to formation of an unregulated disinfection byproduct called N- Nitrosodimethylamine (NDMA). And other nitrosamines. Some are known carcinogens. EPA s Unregulated Contaminant Monitoring Regulation (UCMR) sampled for nitrosamines. No regulations are anticipated at this time Good news: Dosing correctly limits NDMA formation Con: Not as strong as free chlorine. Less effective for pathogen removal than chlorine As a primary disinfectant, takes much longer to kill harmful organisms than chlorine. Need to hold a higher residual due to lower disinfection efficiency. Costs more money

12 Con: Potential nitrification. Nitrification can result in drastic loss of chloramine residual. Nitrification is a biological process where the excess ammonia is eaten by nitrifying bacteria to form nitrite, then nitrate. Nitrification Action Plans (NAPs) can help a PWS detect, prevent, and respond to nitrification. A follow-up TAWWA webinar will cover NAPs. 23 Con: Elastomer degradation Sometimes, chloraminated water can cause more rapid degradation of toilet seals, other elastomeric plumbing appurtenances

13 YR1 25 Con: More chemistry to learn! And that is the next topic in the webinar Pros: Chloramination pros outweigh cons for systems that have source water with high organic carbon and/or very long water age. Cons: Chloramination cons outweigh pros for systems that can operate with free chlorine

14 Slide 25 YR1 We got 15 minutes for Pros and Cons, I will see what I can add Yadhira Resendez, 9/26/2016

15 Outline of Webinar istory and Overview Pros and Cons of Using Chloramines Chemistry of Chloramines Regulatory and Process Management Monitoring Dosing, Boosting, and Blending Chemistry: Chemistry is just algebra with explosive potential. Chloramines: You have the ability to understand chloramine chemistry well enough to disinfect water successfully

16 The Chemicals of Interest (1) Water! 2O! 29 The Chemicals of Interest (2) ydrogen ion ( + ) positive charge. p = - log [ + ] Negative log of hydrogen ion concentration. p is a measurable quantity. When + goes UP, p goes DOWN Electrons negative charge. e - The concentration of electrons is not a measurable quantity

17 The Chemicals of Interest (3) Elemental oxygen Oxygen is O2 in air Also, dissolved in water Elemental nitrogen Nitrogen is usually N2, gas, in air Elemental chlorine Gas chlorine is 2, gaseous 31 The Chemicals of Interest (4) Free Chlorine ypochlorite ion and hypochlorous acid In equilibrium - O (concentrations depend on p) Free Available Ammonia Ammonia and ammonium ion In equilibrium (concentrations depend on p) N O N + N 32 16

18 The Chemicals of Interest (5) N The chloramine family: Monochloramine A good disinfectant. Dichloramine Not a good disinfectant. Stinky and reactive. Trichloramine (nitrogen trichloride) N The most undesirable family member. A very odoriferous gas. N 33 Chlorine-to-ammonia-nitrogen mass ratio ( 2 :N 4 -N): Introduction Chemical reactions are a function of the quantities of chemicals available to react. The ratio of chlorine molecules and nitrogen molecules determines which chloramine species is present. Nitrogen comes from ammonia. Water treatment plants add the correct amount of chlorine and ammonia (nitrogen) at the correct ratio to get the desired monochloramine

19 Chlorine-to-ammonia-nitrogen mass ratio ( 2 :N 4 -N): Mass VS. Number The number of molecules is important for understanding chemicals and reactions. For example, 1 monochloramine molecule has 1 atom of chlorine and 1 atom of nitrogen (and 2 hydrogens). The mass of chemicals is important for treating and monitoring water. For example, we talk about pounds of chlorine added and milligrams per liter. 35 Chlorine-to-ammonia-nitrogen mass ratio ( 2 :N 4 -N): Mass VS. Number When we discuss chemical reactions, we refer to numbers of atoms and molecules. (The term molar describes large numbers of atoms and molecules.) When we discuss treatment, we use mass. And, for monitoring, concentration (mass per volume). The commonly used ratio term: 2 :N 4 -N is based on the mass ratio of chlorine (as 2 ) to nitrogen (Nitrogen, as N, which is available from ammonia.) 36 18

20 Yuefeng Xie s Bar Theory of Chloramination This chlorine molecule walks into a bar At first, there are lots of free available ammonia molecules. Later, a chlorine molecule walks into a bar And all the free available ammonia molecules were used up N 37 Bar Theory of Chloramination N N N N N 38 19

21 Breakpoint curve discovery Adding chlorine to water with ammonia in it does not act like you think it should. Measured Residual (mg/l) Total Chlorine = Sum of active chlorine species 1:1 NO ammonia in water you add chlorine to Ammonia in the water that you add chlorine to Chlorine added to water (~2: N3-N Ratio) 39 Monochloramine Chemistry (N 2 ) O N & N & O O + N 3 N O Equilibrium means that hypochlorous acid and ammonia are present with monochloramine 40 20

22 Monochloramine (N 2 ) O N & N & O Monochloramine (N 2 ) formation O + N 3 N O Free chlorine in contact with ammonia forms monochloramine and water, in equilibrium. Monochloramine is the desired species for chloramination in drinking water treatment It is the desired disinfectant. Forms fastest at p 8.3 Dominates when 2 :N 4 -N mass ratio is 0 to ~5:1 Total chlorine increases at about 1:1 during monochloramine formation 42 21

23 Residual Total Chlorine (All species as 2 ) N 0:1 5:1 7:1 Monochloramine Chlorine:Ammonia-nitrogen ( 2 :N 4 -N) mass ratio O Up to a ~5:1 2 :N 4 -N mass ratio it is mostly monochloramine (1:1 ratio of atoms) N 43 Dichloramine (N 2 )Chemistry from monochloramine and hypochlorous acid N & O N & O N 2 + O N O 44 22

24 Dichloramine (N 2 ) chemistry from monochloramine autodecomposition O N & N & O N 2 N 2 N 2 + N 3 In water. N Dichloramine Formation Two reactions O + N 2 N 2 + 2O Monochloramine reacts further with chlorine to give dichloramine and water, essentially 1-way Occurs at p <8 2N 2 N 2 + N 3 Autodecomposition of monochloramine into dichloramine equilibrium When you are getting significant dichloramine, the total chlorine curve will start dropping

25 Residual Total Chlorine (All species) N 0:1 5:1 7.5:1 Dichloramine Chlorine:Ammonia-nitrogen ( 2 :N 4 -N) mass ratio O Between 5:1 and 7:1 2 :N 4 -N mass ratio, it is dichloramine N 47 Trichloramine (N 3 ) Chemistry (nitrogen trichloride) O O & O N & N N 2 + O N O 48 24

26 49 Trichloramine (N 3 ) formation Trichloramine, AKA Nitrogen trichloride (N 3 ) O + N 2 N 3 + 2O Dichloramine reacts with chlorine to form nitrogen trichloride. Favored at low p, only detectable at p < 4. Trichloramine is not soluble in water, it off-gasses. Present at 2 :N 4 -N mass ratios ~ 7:1 8:1. It smells terrible. Present at the breakpoint the dip of the breakpoint curve. 49 Residual Total Chlorine (All species) N 0:1 5:1 7:1 Trichloramine, Other products Chlorine:Ammonia-nitrogen ( 2 :N 4 -N) mass ratio O Starting around ~7:1 2 :N 4 -N mass ratio, it is trichloramine and other chemicals, mostly N 2, many gaseous N 50 25

27 Other Reactions at Breakpoint O O O N & N N O N 2 + O N O Other Products in Breakpoint Zone N2 Intermediates Products In addition to N 3, other products are formed: N 2, 2 O, -, +, NO 3 -, About 90% N 2 And tiny bits of other things These do not contribute to total chlorine residual or to total ammonia residual Some dissipate as gas, some become non-reactive Intermediates are unstable molecules N 2 + O N O Estimate of reactions (Benefield) 52 26

28 53 Organic Amines In drinking water treatment, chlorine and chloramines react with naturally occurring organic molecules This reaction can form stable organoamines Commonly expressed as R-Nx Normal field tests may detect organoamines as total ammonia Breakpoint Curve elps us understand the chloramination process. elps us interpret results of laboratory/field tests. elps us visualize where we are in the chloramination process. elps us optimize disinfection

29 Breakpoint curve Total Chlorine Species Free Ammonia Monochloramine Dichloramine Total Chlorine = The sum of all active chlorine species Free Chlorine Trichloramine 2 :N 4 -N mass ratio 5:1 7: Breakpoint Curve Example: What can we measure? NOT dichloramine or trichloramine. What do we need to measure to completely characterize chloramine water quality? 56 28

30 Chlorine Residuals: Total and Species (mg/l) 2 1 IF: Total Chlorine = 1.5 mg/l Where are you on the curve? Do you have enough information? Monochloramine Free Ammonia Total Chlorine 2:N3-N ratio 5:1 7:1 Free Chlorine Chlorine Residuals: Total and Species (mg/l) IF: Total Chlorine = 1.5 mg/l Total Chlorine Monochloramine Free Ammonia 2:N3-N ratio 5:1 7:

31 Chlorine Residuals: Total and Species (mg/l) IF: Total Chlorine = 1.5 mg/l AND Monochloramine = 1.2 mg/l Total Chlorine Monochloramine Free Ammonia Free Chlorine 2:N3-N ratio 5:1 7:1 59 Chlorine Residuals: Total and Species (mg/l) IF: Total Chlorine = 1.5 mg/l AND Monochloramine = 1.2 mg/l AND Free Ammonia = 0.4 mg/l Monochloramine Free Ammonia Total Chlorine 2:N3-N ratio 5:1 7:1 Free Chlorine 60 30

32 What do you need to monitor to fully describe where you are on the breakpoint curve? A. Total chlorine B. Monochloramine C. Free ammonia D. Free chlorine E. A, B, and C F. All of the above Chemistry: Chemistry is just algebra with explosive potential. Chloramines: You have the ability to understand chloramine chemistry well enough to disinfect water successfully

33 Outline of Webinar istory and Overview Pros and Cons of Using Chloramines Chemistry of Chloramines Regulatory and Process Management Monitoring Dosing, Boosting, and Blending Chloramine effectiveness: Monitoring results reveal whether you have the right chlorine-to-ammonia-nitrogen mass ( 2 :N 4 -N) ratio for effective chloramination. Minimum: Regulatory monitoring is a minimum. YMMV

34 65 Regulatory monitoring istorically, chloramine monitoring requirements were conditions of the site-specific TCEQ exception approval letter. Since July 2015, the monitoring requirements are in the Chapter 290 rules. 30 TAC : Disinfectant Residuals One-Time Source Water Monitoring Baseline and Ongoing Routine Monitoring Regulatory monitoring: Outline Just total chlorine: Regulatory minimum residual, representative sites. Weekly <250 connections, Daily >250. Total chlorine & monochloramine & ammonia Chloramine-effectiveness suite at least weekly. Representative: At least all EPs, low/average/high water age sites in each pressure plane. Baselines: Source water ammonia, nitrite/nitrate. Nitrification detection: Nitrite/nitrate in distribution 66 33

35 Monitoring Overview Total Chlorine Free Ammonia Monochloramine Nitrite and Nitrate Routine Chloramine-effectiveness Monitoring At or After the Entry Point(s) At least weekly. At least weekly. At least weekly. Monthly for at least 6 months to set baseline, then quarterly. Upstream and Downstream of Any Chlorine or Ammonia Injection Points Weekly and before and after adjusting the chlorine or ammonia feed rate. Weekly and before and after adjusting the chlorine or ammonia feed rate. Weekly and before and after adjusting the chlorine or ammonia feed rate. Routine sampling not required. (May be part of a Nitrification Action Plan.) In the Distribution System Daily / weekly. At least weekly. At least weekly. 67 At least quarterly, and in response to action level triggers Ammonia One Time Source Water Monitoring Requirement: Ammonia Baselines for each source Test Frequency at each source (including purchased water take points) Ammonia Once or more to determine the availability of source water (as nitrogen) ammonia for chloramine formation. If source has more than 0.5 mg/l free ammonia (as nitrogen), monitor monthly for six months to establish baseline. *If you have already completed this source water monitoring in the past and have the results, there is no requirement to take new samples

36 69 Nitrite/Nitrate Source Water Monitoring Requirement: Baselines Baseline determination: If you don t have a baseline: On-going monitoring: After a baseline is set: Monthly for six (6) months at each Entry Point Or use quarterly compliance samples, if present. (Or more sampling if needed/wanted) Quarterly at each EP. Quarterly in distribution at representative sites where total/mono/ammonia are collected As part of Nitrification Action Plan: As a response action: If other sampling triggers response actions. Entry point samples may be collected at entry point sample site, or first customer 69 Process management monitoring Regulatory monitoring may not identify issues early enough to avoid problems. You are the expert on your system: You can identify additional sampling to avoid problems before they start. Development and implementation of a Nitrification Action Plan (NAP). Process management monitoring may save you from bad situations

37 Monitoring by location Follow the water: Raw water: Determine baselines. In-plant: (Treating source water, or boosting disinfectant residual in distribution) Entry points: Defined as where water enters the distribution system Distribution: Representative sites 71 Raw water sampling The main purpose of sampling raw water is to determine whether ammonia is present in source water. Some PWSs may have chloramines present, but think they have free chlorine. Notably Gulf Coast, Carrizo-Wilcox NE Nitrite and nitrate baselines can be found at EPs. Source monitoring is needed for situations where multiple sources feed a single EP. Which is the bad source? 72 36

38 In-plant sampling The main purpose of sampling raw water is to determine whether chemicals are being injected correctly to accomplish treatment objectives. 73 Monitor treatment before and after chemical injection Treatment monitoring is required to make sure 2:N4-N mass ratio is right. by Subchapter F, [ (c)(4)(E)] Total Chlorine Free Ammonia Monochloramine Nitrite and Nitrate Upstream and Downstream of Any Chlorine or Ammonia Injection Points Weekly and before and after adjusting the chlorine or ammonia feed rate. Weekly and before and after adjusting the chlorine or ammonia feed rate. Weekly and before and after adjusting the chlorine or ammonia feed rate. Routine sampling not required

39 Ideal chloramination monitoring Inject chlorine Mix Inject ammonia Mix Measure total chlorine, monochloramine ammonia Measure chlorine Base ammonia dose on measured chorine residual 75 Entry point (EP) sampling The purposes of sampling at entry points is: Determine effectiveness of dosing: Is the residual adequate to get chloramines to adequate levels throughout the system? Determine how much ammonia is present: Because it can serve as food for nitrifying bacteria Establish expected baseline levels of nitrite and nitrate: In order to know when levels are not normal, which can indicate nitrification

40 77 Monitoring: Entry point Total Chlorine, Monochloramine and Ammonia (as N): Weekly. Nitrite and Nitrite: If you don t have a baseline: Monthly for six (6) months After a baseline has been set: Quarterly Samples may be collected at first customer OR entry point. If quarterly entry point samples are collected by TCEQ, those can be used. [ (c)(5) ] Entry Point(s) Total Chlorine At least weekly. Free At least weekly. Ammonia Monochloramine At least weekly. Nitrite and Nitrate Monthly for at least 6 months to set baseline, then quarterly Sample all entry points (EPs) Surface Water Treatment Plant EP001 Purchased Water Take Point EP002 Well EP003 Booster plant EP

41 Monitoring: Distribution Purpose 1: Distribution residual compliance. The purpose of daily/weekly total chlorine residual monitoring is to determine levels throughout system. Purpose 2: Chloramine stability. The purpose of required weekly monitoring for monochloramine and ammonia along with total chlorine is to make sure the chloramines are at the right ratio and nitrification is not occurring Monitoring: Distribution Total Chlorine, Monochloramine and Ammonia (as N): Weekly at the same time as a routine total chlorine minimum residual compliance sample. Nitrite and Nitrite quarterly: More frequently would be better. [ (c)(5)(D) ] In the Distribution System Total Chlorine Daily/ weekly. a Free Ammonia At least weekly. b Monochloramine At least weekly. b Nitrite and At least quarterly, and Nitrate in response to action level triggers

42 Monitoring: Distribution sites Representative means: Minimum at least one site at low, medium, high water age in each pressure plane. (If a pressure plane has a single entry point, the low water age and entry point sample can be the same.) More sites may be needed for high water age. Consider dead-end main flushing locations & DBP sites Sites used for coliform monitoring can be used (but that is not required) Sites used for routine total chlorine monitoring should be used Distribution system (1 pressure plane) Water Treatment Plant EP001 Low water age igh water age Average water age igh water age? igh water age 82 41

43 Distribution sites: Use Critical Control Points Recommended that critical control points are also selected, where high value information is obtained. Areas where water is controlled. Areas where a problem can be corrected quickly. Areas where problems are encountered, for example, complaints or low residual. Examples: Tanks, pump stations, interconnections, pressure plane entrance, booster plants, etc Critical control points EP001 Before/after booster plant Complaints Before/after storage tank Area with poor water quality 84 42

44 85 Chloramine effectiveness: Monitoring results reveal whether you have the right chlorine-to-ammonia-nitrogen ratio for effective chloramination. Minimum: Regulatory monitoring is a minimum. YMMV. 85 Outline of Webinar istory and Overview Pros and Cons of Using Chloramines Chemistry of Chloramines Regulatory and Process Management Monitoring Dosing, Boosting, and Blending 86 43

45 87 Dosing: Start right, stay right. Boosting: Don t spend money on ammonia if you don t need to. Blending: Don t do it if you don t control the ratio. 87 Dose chemicals correctly At treatment plants and booster stations, base the chemical dose on monitoring not theory. Chlorine demand in source water can cause theoretical ammonia dose to be too high: Feeds nitrifying organisms that eat ammonia. Wastes money on extra ammonia. If mixing is imperfect or incomplete, localized breakpoint environments can cause lower than theoretical monochloramine concentration

46 Dosing Rules of Thumb If free ammonia is present, you are in the monochloramine zone. If free chlorine is approximately equal to total chlorine, you are past the breakpoint. You always get a little tiny drop of free chlorine but if free ammonia is present, free chlorine CAN T be present 89 Dosing rules of thumb Responding to Issues What to change: Monochloramine (or total chlorine) too high Reduce BOT ammonia AND chlorine feed. Total chlorine drops after ammonia addition Increase ammonia feed OR reduce chlorine feed (or possibly both). Ammonia too high Reduce ammonia feed OR increase chlorine feed (possibly both, one at a time). Total chlorine higher than monochloramine Reduce chlorine feed

47 Breakpoint curve Total, Free Ammonia Residual Monochloramine dominates, free ammonia is present & decreasing ( 2 :N 4 -N mass ratio 0:1 to 5:1) Dichloramine (and others) form and decay, free ammonia is not present (5:1 to 7:1) Free chlorine increases with dose, no free ammonia present ( 2 :N 4 -N mass ratio above 7:1) 2 :N 4 -N 5:1 7:1 mass ratio 91 Dosing source water Start right, stay right! Is there any ammonia in the source water? If so, monitor periodically and use the measured amount in dose calculations

48 Dosing source water Total chlorine residual Sources suggest over 2.0 mg/l is best. The lower the residual, the greater the risk. Ammonia Minimize ammonia entering the distribution system target of just detectable. If you think you can control it at zero okay but watch out, you may slide towards breakpoint. If residual starts dropping, troubleshoot by increasing ammonia. 93 Dosing chloramines: Order and targets Generally, chlorine must be added first. The free chlorine added should equal the target total chlorine before adding ammonia. After adding ammonia, some free ammonia will be detectable. Free available ammonia should be low, but present. After adding both chlorine and ammonia, there should be little change in the total chlorine The total chlorine should equal the monochloramine after reaction

49 Dosing source water: Order of addition, mixing Order of addition for source water treatment: (For an undisinfected, raw source) Add chlorine first for dosing raw water. Adding chlorine first provides a safety factor for viral inactivation. NOTE: SWTP can get exception to add ammonia first with additional 1-log viral inactivation. Adding ammonia first is easier, especially in water that tends to form high DBPs, like Rio Grande. 95 Ideal source water chloramination Inject chlorine Mix Inject ammonia Mix Measure total chlorine, monochloramine ammonia Measure chlorine Base ammonia dose on measured chorine residual 96 48

50 Reality of some chloramination Inject chlorine Inject ammonia Mix Measure total chlorine, monochloramine ammonia No room to measure chlorine Ammonia dose is calculated based chlorine dose 97 Boosting chloramines Measure the free ammonia, total chlorine, and monochloramine before boosting. Measure free chlorine if desired, but don t place too much importance on the result. Do some ratio math based on measurements: Target between a 4:1 to 5:1 :N4-N ratio. You are aiming for the sweet spot. The peak of the curve. While trying to stay out of the dip. The dip = the breakpoint

51 Breakpoint curve Total, Free Ammonia Residual Monochloramine dominates, free ammonia is present & decreasing ( 2 :N 4 -N mass ratio 0:1 to 5:1) Dichloramine (and others) form and decay, free ammonia is not present (5:1 to 7:1) Free chlorine increases with dose, no free ammonia present ( 2 :N 4 -N mass ratio above 7:1) 2 :N 4 -N 5:1 7:1 mass ratio 99 Booster treatment: Order of addition, mixing Order of addition for booster treatment of previously disinfected water: Add ammonia first to boost water containing chloramines. Add chlorine first to boost water containing free chlorine

52 Ideal booster chloramination design Inject Ammonia-Measure Inject Measure IF needed total, chlorine Measure total chlorine, mono, total chlorine, monochloramine, ammonia monochloramine, ammonia ammonia Mix Mix Base ammonia dose on desired monochloramine residual Base chlorine dose on measured ammonia residual 101 Boosting chloramines If you are purchasing and redistributing chloraminated water, you need to know what is in there. Especially if you add more disinfectant ( boosting ). And especially if you are blending chlorinated and chloraminated water, Which is generally a bad idea

53 Boosting chloramines Measure the free ammonia, total chlorine, and monochloramine before boosting. Measure free chlorine, too, but don t place too much importance on the result. Do some math: You are aiming for the sweet spot. Trying to stay out of the dip. 103 Special breakpoint study: To learn more about your water You can do a breakpoint curve on your water: Put some of your source water in a series of jars. Add a little ammonia (measured). (Not like source-treating plant where ammonia is 2 nd ) Add chlorine in increasing amounts (measured) to each jar. Incubate for desired hold time (eg: 1 day). Calculate the :N4-N ratio to decide how much Draw a graph of Total Chlorine (Y axis) and Ammonia Added (X axis). Voila! Personalized breakpoint curve

54 Special breakpoint study: To learn more about your water Simulated Distribution System (SDS) study 105 Special decay (bucket) study: To learn how long your residual lasts You can do a decay study your water: Put some of your source water in a bucket. Measure total chlorine, etc. till it is all gone

55 Blending chloramines and chlorine In Texas, PWSs that blend chloraminated and chlorinated water in their system must request an exception. Case-by-case, site-specific review. Contact TCEQ Plan and Technical Review Section. Submit a description of how water is blended, monitoring, plans, specifications as needed. 107 Blending Scenarios Blending: In distribution. In a tank. Not blending: ydraulically isolated areas served with different disinfectants are not considered blending. For example, isolation valves. Special blending scenarios: Seasonal and emergency

56 Blending in distribution What is your ratio? Is it the same everywhere? SWTP 109 Purchased Water Take Point? Well Well Consider: Blending in Distribution Blending zones may vary depending on: Sources and seasonal utilization. Flow and demand. Concern: :N4-N ratio will be unknown, and PWS may see low residuals in blending areas. Monitoring must be conducted upstream, downstream, and in the blending zone(s)

57 Blending in a Tank SWTP Well Consider: Blending in a Tank Monitoring must be conducted on both sources prior to entering the tank. Know what is going in. Flow AND chemicals. Monitoring must be conducted on the water leaving the tank. Know what is coming out. Know what to monitor: Total? Free? ow can you ensure the water in the tank is properly mixed? Could localized degradation occur due to poor mixing?

58 113 ydraulic isolation Chloramines Free Chlorine SWP Well 2 Well 3 PS Consider: ydraulic isolation Ensure that water with different disinfectants is completely separate. Monitor upstream and downstream of valves to find and stop leaks. Inspect valves to make sure they are working. ave an Emergency Blending Plan and SOP for when it is necessary to open the valve and blend. NOTE: Chloraminated area must meet the TCEQ chloramine rules

59 Special Blending Scenarios: Seasonal Seasonal Blending. Blending only occurs a few months a year (e.g. summer months) Example: Groundwater system on free chlorine year round, but purchase chloraminated water in the summer to meet demand. 115 Special Blending Scenarios: Seasonal Seasonal Blending Monitoring must be conducted during the blending periods to ensure protection of public health by maintenance of stable residual

60 Special Blending Scenarios: Emergency Emergency Blending. Example: Chloraminated system with wells maintained as backup for emergencies. 117 Special Blending Scenarios: Emergency Emergency Blending Exercising emergency wells Water sent to distribution Water not sent to distribution If emergency >14 days, give TCEQ a call

61 119 Dosing: Start right, stay right. Boosting: Don t spend money on ammonia if you don t need to. Blending: Don t do it if you don t control the ratio Chloramines are an important tool. Chloramines help systems control regulated disinfection byproducts, and maintain continuous, stable residuals. Monitoring is key to successful chloramination. Monitor chloramine effectiveness using total chlorine, ammonia, and monochloramine. Detect nitrification using nitrite and nitrate

62 Thanks! Questions? 121 Presenter contact information Alicia Diehl, P.E. Ph.D. Altamira Water LLC, TCEQ contractor Marlo Wanielista Berg, P.E., TCEQ WSD Yadhira A. Resendez, E.I.T., M.S.E, TCEQ WSD

63 References M20 Water Chlorination and Chloramination Practices and Principles, Second Edition, American Water Works Association Drinking Water Distribution Systems: Assessing and Reducing Risks, National Academies of Science, 2006 White s andbook of Chlorination and Alternative Disinfectants, Black & Veatch Corporation, EPA references General information: Web based chloramine simulators: Presentation on the web-based applications (starts at 31 minutes into the recording): General Chloramine Chemistry Application: usepaord.shinyapps.io/unified-combo/ Breakpoint Chloramine Chemistry Application: usepaord.shinyapps.io/breakpoint-curve/

64 TAWWA resources: Next webinar: Nitrification Action Plans for Public Water Systems using Chloramines Recommendations and TCEQ Requirements November 17, 2016 Register at TAWWA.org