2012 Water Research Foundation. ALL RIGHTS RESERVED.

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1 2012 Water Research Foundation. ALL RIGHTS RESERVED Water Research Foundation. ALL RIGHTS RESERVED. No part of this presentation may be copied, reproduced, or otherwise utilized without permission.

2 Development of a Bench-Scale Test to Predict the Formation of Nitrosamines Project Water Research Foundation. ALL RIGHTS RESERVED.

3 2012 Board Approved Focus Areas Hexavalent Chromium: Filling Critical Knowledge Gaps to Inform Effective Rulemaking and Customer Communication Water Utility Infrastructure: Applying Risk Management Principles to Effectively Manage Deteriorating Infrastructure NDMA and Nitrosamines: Precursor Control, Treatment Practices, and Distribution System Operations to Achieve Regulatory Compliance Carcinogenic VOCs Contaminant Group: Filling Critical Knowledge Gaps to Inform Meaningful Regulation Water Utility Energy Efficiency and Integrated Water-Energy Planning: Developing Tools and Strategies Water Utility Finances: Best Practices for Setting Rates, Financing Capital Improvements, and Achieving Public Support CECs in Drinking Water: Improved Cost-Benefit Analysis of Different Management Approaches Contaminant Risk Communication: Developing Core Messages and Engaging Critical Stakeholders Water Demand: Improving the Accuracy of Forecasts and Management Biofiltration: Defining Benefits, Overcoming Unintended Consequences, and Developing Utility Guidance 2012 Water Research Foundation. ALL RIGHTS RESERVED.

4 Foundation Projects 2678: Factors Affecting the Formation of NDMA in Water and Occurrence 2948: Contribution of Wastewater to DBP Formation 2979: Strategies for Minimizing Nitrosamine Formation 3014: Occurrence and Formation of Nitrogenous DBPs 4180: Development of a Bench-Scale Test to Predict the Formation of Nitrosamines 4209: Development and Applications of a Total Nitrosamine Assay for Disinfected Waters 4295: Anion Exchange Resins s as a Source of Nitrosamines and Nitrosamine Precursors 4343: Transformation of Amines to Nitrosamines on Activated Carbons: Implications for Nitrosamine Analysis 4370: Controlling the Formation of Nitrosamine Formation 2012 Water Research Foundation. ALL RIGHTS RESERVED.

5 Development of a Bench-Scale Test to Predict the Formation of Nitrosamines Stuart W. Krasner, Chih Fen Tiffany Lee, Metropolitan Water District i t of Southern California i William Mitch Yale University Urs Von Gunten EAWAG (Swiss Federal Institute of Aquatic Science and dtechnology)

6 Regulatory Activity 10 ng/l notification level for each of 3 nitrosamines (including N-nitrosodimethylamine [NDMA]) in California 5 nitrosamines on the Contaminant Candidate List 3 (CCL3) Nitrosamines may be regulated by U.S. Environmental Protection Agency in near future

7 Background on NDMA NDMA a by-product of some natural waters and wastewaters with chloramines (Mitch et al. 2003) Certain polymers (e.g., polydadmac) can contribute to NDMA precursor material (Kohut & Andrews 2003) Pre-oxidation with chlorine, chlorine dioxide or ozone can destroy or transform precursors for NDMA (Charrois & Hrudey 2007; Lee et al. 2007) Peak in NDMA formation near breakpoint (Schreiber & Mitch 2007)

8 Oxidative Transformation of NDMA Precursors Selective oxidants (e.g., HOCl) react only with some electron-rich organic moieties, such as deprotonated amines (Lee and von Gunten 2010) e.g., maximum rate constant for oxidation of deprotonated amine would be at ph = average value of pk a of HOCl (7.5) and that of the amine (e.g., for trimethylamine, 98): 9.8): ~86 ~8.6.

9 Objectives Develop bench-scale test to predict nitrosamine formation Evaluate sensitivity of test to variations in Cl 2 /N ratio, ph, temperature, and time Evaluate impact of pre-oxidation Pre-oxidation/disinfection i with chlorine, chlorine dioxide, ozone, ultraviolet (UV) Evaluate tradeoffs in formation of regulated and emerging disinfection by-products (DBPs) Evaluate impact of bromide and nitrite

10 Uniform Formation Condition (UFC) Test for Nitrosamines Samples typically collected at filter effluent of plant Samples chlorinated to target ~2.5 mg/l free chlorine residual 3 min of free Cl 2 contact time before ammonia is added Ammonia added at 4.75:1 Cl 2 :NH 3 -N weight ratio Samples kept at 25 o C and at ph ~8 Samples collected at end of 3 days of Samples collected at end of 3 days of chloramine contact time

11 Impact of ph, Temperature, and Time Use UFC protocol as baseline Keep certain parameters constant Free Cl 2 contact time = 3 min Cl 2 /N weight ratio = 4.75:1 Vary other parameters, one at a time ph level: 7, 8, and 9 Temperature: 5, 15, 25, and 35ºC Chloramine contact ttime: 1hr, 1day, 3 days, and d7d days

12 Impact of Cl 2 /N Ratio Use UFC protocol except After 3 min of free Cl 2 2, apply various concentrations of ammonia to produce following Cl 2 /N weight ratios: 3.6 (range in U.S. is ~3 to 5) 5.1 (maximum in breakpoint curve at 5.1) 6.3 (past the maximum) 7.6 (breakpoint at ~8) 8.6 In some tests, some additional ratios In selected tests, ammonia added first In some tests, conducted at ph 7

13 Impact of ph, Temperature, and Time Results

14 Impact of ph and Time at 25 C on NDMA Formation at Plant Using PolyDADMAC (MWDSC s Mills Plant)

15 Impact of ph and Time at 5 C on NDMA Formation at Mills Plant

16 Impact of ph and Temperature on 3-Day NDMA Formation at Mills Plant

17 Impact of ph and Temperature on 3-Day NDMA Formation at Another PolyDADMAC Plant

18 Impact of ph and Temperature on 3-Day NDMA Formation at PolyDADMAC Plant with Nitrified Biofilter (MWDSC Demo Plant*) *Evaluating the ammonia-chlorine process for bromate control

19 Impact of ph and Temperature on 7-Day NDMA Formation at Mills Plant After Implementation of Ammonia-Chlorine Process Biofilter Effluent Filter Influent

20 Hypotheses/Experimental Hypotheses Soluble microbial products (SMPs) from nitrified biofilter another source of NDMA precursors At ph 8 and/or 9, pre-chlorination (3 min) at 25 C destroying more NDMA precursors than at 5 C Testing Hypothesis Evaluate different pre-chlorination (pre-cl 2 2) )/post-chloramination (post- NH 2 Cl) temperatures

21 Impact of Pre-Cl 2 /Post-NH 2 Cl Temperature and ph on 3-Day NDMA Formation in Mills (Nitrified) Biofilter Effluent 20 ph7 ph8 ph9 NDMA (ng/l) No impact at ph 7 e.g., Pre-Cl 2 temperature impact at ph C >25C 5C >5C 25C >25C 25C >5C Pre Cl 2 Temperature/ Post NH 2 Cl Temperature

22 ph and Temperature Effects More of the deprotonated amine present at ph 8 9, which can be destroyed/transformed by Cl 2 Cl 2 more effective at 25 C than at 5 C At ph 7, not much of the amines are deprotonated Not that much deprotonated amine available to destroy NH 2 Cl forms more NDMA at 25 C than at 2 5 C

23 Impact of ph and Temperature on 3-Day NDMA Formation at Wastewater-Impacted Plant

24 Impact of Cl 2 /NH 3 -NRatio Results

25 Effect of Cl 2 /N Ratio (Cl 2 Added 1 st ) on NDMA Formation for Waters Treated w/ PolyDADMAC

26 Difference with Literature Findings Schreiber & Mitch 2007 Tested a model compound (dimethylamine [DMA]) and treated wastewater Added ammonia first and chlorine second Conducted test at ph 7

27 Effect of Cl 2 /N Ratio (Cl 2 Added 1 st ) on NDMA Formation for Wastewater-Impacted Waters ND DMA (ng/l L) Cl 2 /N = 6.3 WW DWTP 1/OI WW DWTP 1/OE WW DWTP Cl 2 /N Weight Ratio (mg/mg)

28 Effect of Cl 2 /N Ratio (NH 3 Added 1 st ) on NDMA Formation (WW DWTP 1/OI Water at ph 7)

29 Simulated Distribution System (SDS) Test Results Site-Specific Conditions Used in SDS Test Cl 2 and NH 3 Doses, Free Cl 2 Contact Time, ph, Temperature, and Detention Time

30 NDMA SDS Validation Median difference = 0.9 ng/l

31 Summary and Conclusions Reactivity and chemistry of NDMA precursors from treated wastewater, polydadmac, and SMPs were different Waters impacted by treated wastewater had peak or substantial NDMA formation at Cl 2 /N ratios approaching breakpoint Some waters had higher apparent NDMA formation at 5ºC than at 25ºC at ph 8 and/or at ph 9 Bench-scale test developed to simulate full-scale formation

32 Tradeoffs in DBP Formation During Chloramination Following Pre-Oxidation for Nitrosamine Control William Mitch Amisha Shah h Department of Chemical and Environmental Engineering Yale University Stuart Krasner Chih-Fen Tiffany Lee Metropolitan Water District of Southern California Urs von Gunten EAWAG Bernie Bubnis NovaChem

33 NDMA Formation Kinetics New Reaction Pathway: Competition (1) HN Cl Cl + k d1 CH 3 Cl CH 3 3 HN CH 3 H N N CH 3 UDMH-Cl Steady State Assumption (2a) Cl H Cl N N UDMH-Cl CH 3 + CH 3 HN (2b) O O N N CH 3 + Cl Cl k d2 k d3 Products H 3 C N N O [UDMH-Cl] d[ndma] dt ss k k [NHCl ][DMA] d1 2 [NHCl ] k [O (g)] d2 2 d3 2 k d 3 [O 2 (g)][udmh-cl] ss H CH 3 UDMH-Cl C H 3 NDMA d [NDMA] kd1 [NHCl 2 ] kd3 [O 2 (g)][dma] dt k [NHCl ] k [O (g)] d2 2 d3 2

34 Strong Pre-oxidants to destroy precursors BUT There is no free lunch Chlorine: forms THMs/HAAs Ozone: forms bromate/chloropicrin Chlorine dioxide: chlorite UV: no chemicals no problem? no residual must combine with chlorine/chloramines Goal: evaluate tradeoffs in reducing nitrosamines vs. promoting other DBPs for different pre-oxidant/chloramine combinations

35 Why UV? MP UV emission overlaps nitrate/nitrite sorption spectrum reactive nitrogen species form ONOOH/ONOO - pk a = nm = nm = Dominant < 280 nm NO 3 - h NO * + O* - * nm = h h 7000 n * 6000 NO 2- + ~300 nm O* = Dominant > 280 nm 1 cm -1 ) a (M NO 3 - LP lamp NO 2 - NO Wavelength ( ) (nm) cm -1 ) a (M - Further rxns to NO 2 *, NO*, O 2 * -, OH*, and NO 2- or NO 3 - And dependent on ph and dissolved CO 2 NO 2* + OH - k =! x M -1 s -1 NO OH* NO * + O* - h 351 nm = a (M -1 cm -1 ) MP lamp NO NO Wavelength ( ) (nm) a (M -1 cm -1 )

36 MP UV-Enhanced TCNM Formation Utility A: <0.5 mg/l nitrate Cincinnati: 1.1 mg/l_n nitrate TCNM O 280 mj/cm 2 Utility A Cl Cl Cl N + O - ICR median Disinfection range Significant TCNM formation at native nitrate for MP UV, not LP UV 62% of utilities using UV use MP UV

37 Reaction conditions Apply pre-oxidants at native ph for CTs relevant to disinfection Chlorine: mg*min/l Ozone: 0-2 mg*min/l Chlorine dioxide: 0-25 mg*min/l UV: MP UV mj/cm 2 relevant e to disinfection through AOP Chloraminate with simulated distribution system (SDS) assay ph with borate buffer add chlorine to achieve 2.5 mg/l residual after 3 min add ammonia at 4.75:1 ammonia:chlorine weight ratio let sit in dark at room temperature for 72 h4.75:1 Cl 2 :NH 3 -N

38 Wastewater-Impacted Plant EPA Region 8: Pre-chlorination THMs/HAAs near MCL NDMA (n ng/l) NDMA THMs HAAs TCA Other DBPs ( g/l) TCA = trichloroacetaldehyde (chloral hydrate) Pre-Chlorine Exposure (mgxmin/l)

39 Wastewater-Impacted Plant EPA Region 8: Pre-ozonation Bromate near MCL Increase in chloropicrin and trichloroacetaldehyde

40 Wastewater-Impacted Plant EPA Region 8: Pre-chlorine dioxide Chlorite near MCL

41 Wastewater-Impacted Plant EPA Region 8: Pre-MP UV MP UV deactivates precursors! Increase in chloropicrin and trichloroacetaldehyde

42 Wastewater-Impacted Plant EPA Region 8: comparison: Chlorine/ozone more efficient than MP UV or chlorine dioxide 30 Cl 2 O 3 80 NDM MA (ng/l) NDMA THMs HAAs TCA Other DBP Ps ( g/l) Pre-Chlorine Exposure (mgxmin/l) ClO 2 MPUV

43 DADMAC-Using Plant EPA Region 9: pre-cl 2 THMs/HAAs below MCL Bromide = 80 g/l TOC = 2.5 mg/l SUVA = 1.52 L/mg*m ph = 8.0 Nitrite <10 g-n/l Nitrate = 0.4 mg-n/l

44 DADMAC-Using Plant EPA Region 9: pre-mpuv Bromide = 80 g/l TOC = 2.5 mg/l SUVA = 1.52 L/mg*m ph = 8.0 Nitrite <10 g-n/l Nitrate = 0.4 mg-n/l

45 DADMAC-Using Plant EPA Region 9: pre-o 3 Bromide = 80 g/l TOC = 2.5 mg/l SUVA = 1.52 L/mg*m ph = 8.0 Nitrite <10 g-n/l Nitrate = 0.4 mg-n/l

46 DADMAC-Using Plant EPA Region 9: pre-clo 2 Bromide = 80 g/l TOC = 2.5 mg/l SUVA = 1.52 L/mg*m ph = 8.0 Nitrite <10 g-n/l Nitrate = 0.4 mg-n/l ClO 2 least effective of the oxidants

47 DADMAC-Using Plant chlorine EPA Region 9 MP UV O 3 ClO 2

48 Pre-chlorination may increase NDMA Water A: wastewater effluent nitrite 290 g/l-n nitrite spike increased NDMA Water E: wastewater-impacted river water nitrite 31 g/l-n no effect of nitrite spiking N DMA (ng/l L) A E Pre-Chlorine Exposure (mgxmin/l)

49 Wastewater Plant 1 Nitrite effect: (1) O H O Cl + N HO - + O - O N O Cl O O O N + (2) N + N O O - Cl O - O N + O - + Cl - (3a) O H CH 3 C O - 3 O - + N NO + HN N + 2 N + N O - CH 3 H 3 C O O Dimethylnitramine - CH 3 O CH (3b) O N NO 3 + H N HO N N O CH 3 H 3 C N O NDMA At ph 6.7 Same water with 0 mg/l_n nitrite and chlorine for 30 seconds then ammonia 5 ng/l NDMA Same water with 0.28 mg/l_n nitrite and chlorine for 30 seconds then ammonia 25 ng/l NDMA At ph 8: nitrite addition doesn t matter (OCl - ) Nitrite can matter for wastewater effluent, but not for drinking water

50 Pre-chlorine dioxide may increase NDMA Wastewater DADMAC Anion-exchange

51 Comparison of Pre-Oxidants Efficiency of deactivation at 1/3 of CT range chlorine: ~40 mg*min/l ozone: ~0.7 mg*min/l ClO2: ~7 mg*min/l Generally O3 > chlorine > ClO2 > MP UV MP UV: ~40 mj/cm2

52 Comparison of Pre-Oxidants Generally did not exceed MCLs even with high pre-oxidant dose But can increase overall exposure TABLE 2: Formation of Other DBPs for exposure/exposure MAX = Pre Chlorine Minimum Median Maximum n g/l g/l g/l THMs HAAs Trichloroacetaldehyde < Pre Ozone Bromate < Chloropicrin < Trichloroacetaldehyde < Pre Chlorine Dioxide Chlorite Pre MP UV Chloropicrin Tihl Trichloroacetaldehyde ld h d <

53 Bromide Effect: Wastewater-Impacted Water Does bromide catalyze nitrosamine formation? Quinnipiac River samples Impact generally not noticeable until 500 g/l

54 Temperature Effect 4 C = open circles Room temp = closed circles Low temp less deactivation at low CT NDM MA (ng/l) Pre-Ozone Exposure (mgxmin/l)

55 Conclusions and Future Work There is no free lunch each pre-oxidant is effective, but each promotes other regulated and unregulated DBPs Whether tradeoffs approach MCL highly water-specific test with new SDS protocol Ozone generally most efficient, but chlorine or can also be water specific MP UV deactivates nitrosamine precursors! insights into precursor structure efficiency low Bromide catalysis of nitrosamine formation during chloramination starts to get important at ~500 g/l Low temperature can enhance nitrosamine formation at low CT Low temperature can enhance nitrosamine formation at low CT less deactivation temperature effect less important at high CT

56 Controlling the Formation of Nitrosamines During Water Treatment (WaterRF 4370) Task 1 Case Studies at Full-Scale Drinking Water Treatment Plants Task 2 Oxidation Strategies Task 3 Polymer Optimization Task 4 Precursor Removal Task 5 Other Sources Task 6 Decision Document and Cost/Benefit Analysis

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58 Questions and Answers 2012 Water Research Foundation. ALL RIGHTS RESERVED.