CHLORAMINATION AND CHLORAMINE ANALYSIS

Transcription

1 CHLORAMINATION AND CHLORAMINE ANALYSIS

2 WHY THIS PRESENTATION? Chloramination use increasing ~1,300 utilities Serving 68 million concerns remains

3 TAKE-HOME MESSAGES Nitrification Chemistry and biology Number of useful approaches to preventing/recovering Manageable Nitrosamines Waters vary in ability to form nitrosamines Pre-oxidation beneficial Treatment chemicals a possible culprit Communications Utilities a trusted source Start early and be prepared Tailor messages for different audiences Be open, respectful, helpful, knowledgeable

4 CHLORAMINATION IS NOT NEW

5 INCREASED USE OF CHLORAMINE Comparison data between 2007 and 2010 Total water systems Total States Population Served % Change Nation ,083,661 68,397,713 Texas ,141,645 12,504,394 Florida ,914, California ,676,183 10,771,907 Li, C., Trends and Effects of Chloramine in Drinking Water. Water Conditioning & Purification 2011.

6 CHLORAMINE USE IN THE US

7 Due to Health Effects

8 CHLORAMINATION Chloramination: Purposeful use of chlorine and ammonia to form monochloramine. Minimizes formation of chlorinated organics Ammonia to chlorine Ratio is controlled to favor formation of monochloramine, typically 5:1 Cl 2 :N Total residual chlorine test: All free and combined chlorine species 8

9 COMBINED CHLORINE - CHLORAMINATION Chlorine (HOCl and OCl - ) reacts with ammonia to form chloramines, commonly referred to as combined chlorine The predominate species are monochloramine and dichloramine. A small fraction is trichloramine or nitrogen trichloride 9

10 Total residual chlorine, primarily monochloramine Free residual chlorine Total Chlorine Residual Cl 2 :N < 5:1, typical BREAKPOINT CURVE Cl 2 :N > 5:1, typical Breakpoint Cl 2 :N > 9:1, typical Chlorine Added 10

11 BREAKPOINT CURVE CONSIDERATIONS Shape of the curve is dependent upon amount of ammonia and other chlorine demand substances in the water temperature ph contact time Most effective disinfection, least taste and odor occurs with free residual chlorine Free chlorine may lead to formation of DBP 11

12 CHLORAMINES Less effective disinfection than free chlorine. HOCl is 25X more effective biocide Chloramines require longer contact time and/or greater concentration than free chlorine. Possible taste and odor (dichloramine) More stable than free chlorine (long distribution systems) Generally do not produce DBP (NH 2 Cl may form DBP NDMA being studied) 12

13 CHLORAMINE FORMATION Monochloramine - NH 2 Cl NH 3 + HOCl NH 2 Cl + H 2 O Dichloramine - NHCl 2 NH2Cl + HOCl NHCl2 + H2O Tricholoramine (Nitrogen Trichloride) - NCl 3 NHCl 2 + HOCl NCl 3 + H 2 O Chloramines are not as effective disinfectants as free chlorine 13

14 DEFINITION OF UNREACTED AMMONIA Ammonia in solution as NH 3 Free ammonia gas dissolved in water or; NH 4 - The ammonium ion 14

15 What are chloramines? Where are chloramines used? Chlorine and Ammonia Chloramination Objectives The Dance of Chlorine and Ammonia Building the Chloramination Curve Preventing Nitrification Cl H Cl H H N N H H Cl

16 WHAT ARE CHLORAMINES? The word chloramines describes the group of three compounds formed by mixing chlorine and ammonia together Monochloramine ideal form for drinking water treatment Dichloramine Trichloramine N Cl H H

17 WHERE ARE CHLORAMINES USED? Chloramines are used in drinking water as an alternative to the more aggressive disinfection of chlorine Chlorine reacts quickly with organic materials present in source water, which can cause the formation of undesirable disinfection by products (DBPs) that are regulated by the EPA Monochloramine i. Is less reactive than chlorine ii. Is a weaker disinfectant than chlorine iii. Requires a longer contact time than chlorine iv. Does not form DBPs v. Is more stable and maintains a longer residual vi. Formation is a complex process

18 CHLORINE AND AMMONIA Chlorine When mixed with water, chlorine forms hypochlorous acid and hypochlorite CHLORINE (Cl 2 ) + WATER (H 2 O) HYPOCHLOROUS ACID (HOCl) + HYPOCHLORITE (OCl-) Cl Cl

19 CHLORINE AND AMMONIA Ammonia When hypochlorous acid is mixed with ammonia, chloramines are formed H N H H - MONOCHLORAMINE (NH 2 Cl) HYPOCHLOROUS ACID + AMMONIA - DICHLORAMINE (NHCl 2 ) (HOCl) (NH 3 ) - TRICHLORAMINE (NCl 3 )

20 CHLORAMINATION OBJECTIVES Blend Chlorine and Ammonia together in a 1:1 molar ratio The goal is to exclusively form monochloramine Inhibit and/or eliminate the formation of dichloramine and trichloramine Dichloramine and trichloramine are unstable, and create taste and odor problems Minimize the introduction of significant amounts of free ammonia in the distribution system Excess free ammonia will promote the growth of bacteria and biofilms, and can lead to nitrification in the distribution system

21 NITRIFICATION IN THE DISTRIBUTION SYSTEM Circular Problem NH 2 Cl + NH 3 /NH 4+ + NO 2- + NO 3 - Disinf f-nh 3 Distribution System ph DO NO 2 - Alk ph DO NO 3 - Alk Sloughing of biofilm causes Turbidity Flow HPC Customer Complaints

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23 NITRIFICATION Ammonia Nitrite Nitrate NH 3 NO 2 NO 3 Nitrosomonas bateria (slow) Nitrobacter bateria (slower)

24 FACTORS PROMOTING NITRIFICATION Sufficient Ammonia Low Chlorine Residual Long Stagnation Time Warm Temperature High Organic Carbon Bacterial Hiding Places

25 LOW LEVEL CHLORAMINES IN DS Issues: 1. Organic chloramines 1. Poor disinfectants 2. Interfere with analytical methods 2. Nitrification/biofilm 3. Premise plumbing concerns 4. Pathogenic organism continuous

26 NITRIFICATION PREVENTION Water Treatment Plant Storage Tanks Distribution System Chlorination Chlorite addition

27 NOM NATURALLY ORGANIC MATTER 27

28 NATURALLY OCCURRING AMMONIA Always had a problem getting a free residual Chlorine dosage rate seemed high Converts free to total Run a free and total chlorine test at POE If high total and low free you probably have natural ammonia. Not all organics are ammonia 28

29 Total CL 1 min Total CL 10 min Total CL 60 min Total CL 360 min Total Chlorine (mg/l) > 6:1 > 14: Chlorine Added (mg/l) USED WITH PERMISSION, GOLDEN STATE WATER 29

30 Free Ammonia (mg/l) Breakpoint chlorination dose of 16.4 mg/l is needed for complete removal of free ammonia min 10 min 60 min 360 min Chlorine Added (mg/l) USED WITH PERMISSION, GOLDEN STATE WATER 30

31 NITRIFICATION Conversion of ammonia to nitrites and nitrates NH 3 + O 2 NO H + + 2e - Nitrosomonas Nitrosococcus, and Nitrosospira. Conversion of nitrite to nitrate NO 2- + H 2 O NO H + +2e - Nitrobacter Nitrospina, Nitrococcus, and Nitrospira 31

32 INDICATION OF NITRIFICATION Chloramine residual Temperature Dissolved Oxygen ph and/or alkalinity HPC NO 2 /NO 3 32

33 MEASUREMENT Monochloramine Free chlorine Total chlorine ph Alkalinity Nitrite/Nitrate TOC ATP HPC DO Temp Water age Nitrifying bacteria N-BART;

34 CONTROL STRATEGIES FOR DISCUSSION ph Free ammonia Water age Chloramine residual Light TOC 34

35 DISTRIBUTION SYSTEM

36 CHLORINATION & CHLORINE BURN Mixed practices- some never do, some do annually (some states require) Can be done in winter or prior to event (summer/fall) Common dose is 1.0 to 2.0 mg/l It is effective no nitrification during free chlorination Disadvantages increase in total coliform, increase in HPC, increase DBPs, increase T&O, nitrification will return Also, can increase chloramine residual up to 3.5/4.0 mg/l Source: Skadsen, J,

37 LIMITS Know all of your limits Understand how the numbers relate to each other as they go through your system React quickly when numbers go the opposite of the desired direction 37

38 CURRENT LIMITS Chlorine Residual > 4 mg/l leaving plant, < 0.5 mg/l throughout the system Monitor daily Chloramines should be slightly less than chlorine residual Free ammonia - > 0.10 mg/l, preferably >0.05 mg/l Monitor these at least weekly 38

39 LIMITS, CONTINUED Nitrate > 10 mg/l Nitrite > 1 mg/l All chloramination systems should be measuring these monthly at the plant and in your systems. Very critical that the numbers don t rise when they are in your system 39

40 BIOLOGICAL TESTING Monthly Coliform samples only show that colifrom is not present. Heterotrophic plate counts will only show the presence of heterotrophs. Specific testing for species such as amoeba are cost prohibitive. Nitrifiers don t show up on most tests until full blown nitrification event is taking place. ATP testing is non specific but is all inclusive 40

41 HPC HETEROTROPIC PLATE COUNT A procedure for estimating the number of live heterotrophic bacteria in water. This test can provide useful information about water quality and supporting data on the significance of coliform test results. 41

42 HPC Widely recogonized test Only recognizes heterotophic bacteria Takes 24 hours for results 42

43 ADENOSINE TRI PHOSPHATE Energy carrier for all cells At least one molecule in every cell If you can extract and count the amount of ATP you can quantify the total amount of biological activity Not species specific Does indicate the total amount of activity 43

44 MEASUREMENT 1 pg/ml of ATP indicates good biological control This level indicates very little biological activity 10 pg/ml of ATP is a level at which you should consider taking corrective action. 10 indicates that there are starting to be some fairly good colonies of organisms growing or that there are a few larger organisms floating around Our old friend the Amoeba. Nitrifiers 44

45 ATP ADVANTAGES Can be done in the field Samples can be collected, chilled and run within 24 hours Results are on obtained in real time. No waiting Progress in remediation can be measured quickly. Species specific testing can be used as a follow up 45

46 ATP DISADVANTAGES Expensive test to run $ 10 per test Meant to be used when it is critical to get a quick results Not meant as a system wide testing method. 46

47 DO - DISSOLVED OXYGEN Measures the amount of oxygen content in water. Higher is better Recent testing has shown it to be very effective at early recognition of nitrification Bugs need oxygen to live, 10% decrease compared to the plant indicate problems Important to understand the relationship of temperature and DO. DO reading go the opposite of temperature. Compare readings at the plant to system 47

48 DO ADVANTAGES Very easy, quick test to run No real cost per test Anybody can run the test Immediate results Probe can be attached to multi parameter meter so additional test can be run (ph, conductivity) 48

49 SUMMARY Test for free and total at the POE Test for free and total through the system Look for areas where total chlorine drops significantly Run a system biological scan. Know what is in your influent water Make sure you understand the relationship of your testing numbers to recognize problems in very early stages 49

50 BREAKPOINT CHLORINATION CURVE I II III Ideal zone for DW disinfection

51 CHLORAMINATION MONITORING & CONTROL Parameters Monochloramine Ammonia Total Chlorine Free Chlorine Data from each of the parameters above can help determine where water is on the breakpoint curve H O Cl

52 CHLORAMINATION MONITORING & CONTROL If the plant does a test for total chlorine, and obtains a result of 3 mg/l Total chlorine = 3.0 mg/l Where on the breakpoint curve are they? What part of the curve makes a significant difference

53 Where is 3 mg/l Total Chlorine? I II III 3 mg/l

54 CHLORAMINATION MONITORING & CONTROL More tests in addition to total chlorine are needed to determine in what zone of the curve the data point falls Monochloramine Free Ammonia Total Ammonia Free Chlorine

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56 CHLORAMINATION MONITORING & CONTROL Laboratory Tests Monochloramine and free ammonia with Monochlor-F reagent Colorimetric method One method sequentially determines monochloramine and free ammonia Can be run on spectrophotometers and some colorimeters Indophenol chemistry Free Chlorine/Total Chlorine DPD colorimetric method Chloramine can produce false positive results Autocat 9000 Autotitrator for chlorine Ammonia ISE (ion selective electrode) Colorimetric ammonia test

57 CHLORAMINATION MONITORING & CONTROL Process Analyzers CL17 Free or Total Chlorine Same colorimetric DPD chemistry as laboratory Different reagents for free or total chlorine CL10 Free (CLF10) or Total (CLT10) chlorine Amperometric chlorine analyzer reagentless chlorine analyzer Ammonia Amtax sc ammonia analyzer APA6000 Monochloramine and Free ammonia analyzer

58 CHLORAMINATION MONITORING & CONTROL Based on data from other tests, the analyst/operator will be able to tell where they are on the breakpoint curve

59 Zone 1 Monochloramine = Total Cl 2 Free ammonia > 0 Zone II Monochloramine < Total Cl 2 Free Ammonia = 0 Zone III Total Cl 2 > 0 Free Ammonia = 0 Monochloramine = 0

60 CHLORAMINATION MONITORING & CONTROL Total Chlorine Free Chlorine Monochloramine ph Alkalinity Nitrate/Nitrite DO HPC ATP DBP Nitrifying Bacteria Temperature

61 Lessons learned Source water implications. What test should you be running? What is the ideal ratio? Why? What is your source water demand? You need to know it. How do you calculate this number? Having problems? Test, test and more test. But know what and why you are testing. Make sure you are using the correct method!

62 QUESTIONS? 62