Characterization of dissolved organic matter in Colorado watersheds: The role of nutrients and algae on DBP formation

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1 Characterization of dissolved organic matter in Colorado watersheds: The role of nutrients and algae on DBP formation Amanda Hohner, Alia Khan, Diane McKnight, R. Scott Summers, and Fernando Rosario-Ortiz Department of Civil, Environmental, and Architectural Engineering, University of Colorado at Boulder

2 Overview of Presentation Introduction Motivation for Study Study Design Chlorophyll, Nutrient, and C-DBP Relationships Fluorescence Relationships (Synoptic Lakes) Nitrogenous DBP Findings (Synoptic Lakes) Conclusions and Future Considerations

3 Introduction WW Discharge Nutrients Algal Growth Organic Matter Disinfection Byproducts

4 Impact of Wastewater Increasing populations and urban development have lead to: Increased WW discharges The use of WW impacted drinking water sources WW Effluent Contains high levels of nitrogen and phosphorus which can lead to eutrophication of surface waters Has been linked to high organic nitrogen levels

different character and reactivity towards chlorine Dissolved

5 Algal Organic Matter (AOM) Eutrophic conditions and WW effluent discharges can increase algal activity and OM Algal OM can have different character and reactivity towards chlorine Dissolved Organic Nitrogen (DON) Levels and N-DBP levels can increase due to algal activity

State of NY Study Focused on the development of nutrient criteria 1998 EPA state water quality standards DBP/Algal Toxin Study Relating nutrient indices

6 State of NY Study Focused on the development of nutrient criteria 1998 EPA state water quality standards DBP/Algal Toxin Study Relating nutrient indices to human health indices for potable surface waters Modeling approach used to set threshold values with respect to TTHM levels TP Chlorophyll-a Secchi Depth

7 Motivation for Study State of Colorado (CDPHE) Clean Water Act meets Safe Drinking Water Act Potential to minimize DBP formation based on source water quality Regulation of wastewater discharges Possible development of a chlorophyll-a standard

Sampled one time in late July or early August 2010

8 Study Design 10 Municipal Lakes Sampled from May- October 2010 (~bi-weekly) 7-11 samples/site 38 Synoptic Lakes Sampled one time in late July or early August 2010 Comprehensive range of water qualities, trophic levels, and locations

10 Analytical Parameters Chlorophyll-a (filter) Total Phosphorus Total Nitrogen Nitrate (NO 3- ) Nitrite (NO 2- ) Ammonia (NH 4+ ) Total Organic Nitrogen Total Organic Carbon Dissolved Organic Carbon UV 254 Fluorescence (Subset) TTHM HAA5 Chloropicrin (Subset) HANs (Subset)

11 Chlorination Conditions (UFC) Uniform Formation Conditions (Summers et al, 1996): Samples buffered to ph 8 ± 0.40 Incubation Time= 24 ± 1 hour Temperature= 20 ± 1.0 C 24 hour free chlorine residual=1.0 ± 0.40 mg/l Values represent average WTP chlorination and distribution conditions UFC were used for this study in order to gain a representative idea of DBP levels, with potential development of source water regulations in mind

12 Study Hypothesis Nutrient levels Chlorophyll-a Can we find meaningful correlations between parameters? TOC and ON C-DBP and N-DBPs

13 Chlorophyll a (µg/l) Chlorophyll-a and Nutrients Municipal Lakes Synoptic Lakes y = 107x 0.76 R 2 = y = 469x R 2 = Total Phosphorus (mgp/l) Total Phosphorus (mgp/l) Municipal r 2 Synoptic r 2 Chl-a and TN # of Sites 9 36 # of Samples (n) 82 36

14 TOC (mgc/l) TOC and Chlorophyll a Municipal Lakes Synoptic Lakes y = 0.68x R² = y = 3.2x 0.26 R² = Chlorophyll a (µg/l) Chlorophyll a (µg/l) Municipal r 2 Synoptic r 2 TOC and Chl-a # of Sites 9 36 # of Samples (n) 82 36

15 DBP (µmol/l) DBPs and TOC 3.0 Municipal Lakes 3.0 Synoptic Lakes TOC (mgc/l) TTHM HAA TOC (mgc/l) TTHM HAA5 Municipal r 2 Synoptic r 2 TTHM and TOC HAA5 and TOC # of Sites # of Samples (n) 90 38

16 Molar Yield (µmol/mgc) DBP Yields and SUVA 0.5 Municipal Lakes 0.5 Synoptic Lakes SUVA TTHM HAA SUVA TTHM HAA5 Municipal r 2 Synoptic r 2 TTHM Molar Yield and SUVA HAA5 Molar Yield and SUVA # of Sites # of Samples (n) 90 38

17 Summary of C-DBP formation Similar increase in DBP levels with nutrients and chlorophyll- a Interdependence on TOC levels restricts any strong conclusions for regulations or standards Multi-linear Regression: Statistically significant relationships (p<0.05) TTHMs: SUVA, DOC, TP HAA5s: SUVA Molar Yields: SUVA

18 Fluorescence and N-DBPs 1. Fluorescence can be a useful indicator of algal organic matter Fluorescence Index= Ratio of intensities at 470/520 nm at excitation of 370 nm 2. Algae produce large amounts of organic nitrogen 3. Organic nitrogen can react to form nitrogenous DBPs Protein Peak Humic Peaks

19 Organic Nitrogen (mgn/l) Organic Nitrogen and Chlorophyll y = 0.17x 0.45 R² = Chlorophyll a (ug/l))

20 Fluorescence Index Fluorescence Relationships Algal/Microbial R 2 = Terrestrial High FI is indicative of algal organic matter and lower FI corresponds with terrestrially derived organic matter Chlorophyll a (µg/l) Synoptic r 2 FI and C:N 0.64 FI and SUVA 0.63 # of Sites 38 # of Samples (n) 38

21 N-DBPs (umol/l) N-DBPs and TOC TOC (mgc/l) HANs Chloropicrin Synoptic r 2 HANs and TOC 0.75 Chloropicrin and TOC 0.56 # of Sites # of Samples (n) 31-38

22 HAN Molar Yield (µmol/mgc) HANs and C:N y = 0.30x -1.5 R² = C:N Poor/no correlation with C:N for Chloropicrin

23 DBAN and CBAN Molar Yield (umol/mgc) Fluorescence and N-DBPs y = 1E-11e 13.0x R² = Terrestrial Fluorescence Index Algal/Microbial Poor/no correlation with FI for Chloropicrin or DCAN

Humic Peaks and N-DBPs Humic Fluorescence Peak Peak A Intensity Peak C Intensity TTHM r 2 HAA5 r 2 DCAN r 2 Chloropicrin r 2 0.74 0.40 0.62 0.70 0.

24 Humic Peaks and N-DBPs Humic Fluorescence Peak Peak A Intensity Peak C Intensity TTHM r 2 HAA5 r 2 DCAN r 2 Chloropicrin r Poor correlations with humic peaks (A and C) for DBAN and BCAN Poor correlations with protein peaks (B and T) for all DBP species

25 Conclusions Nutrients, Chlorophyll, and DOC were positively correlated Correlations were found between nutrient levels and chlorophyll concentrations with DBP formation, however variables are interdependent The fluorescence index proved useful for identifying organic nitrogen and algal enriched waters Fluorescence index was correlated with BCAN and DBAN formation, but not DCAN or Chloropicrin formation Peak A and Peak C intensities indicate TTHM, DCAN, and Chloropicrin formation potentials

26 Future Considerations More in depth fluorescence analysis PARAFAC Additional Samples Analysis of ON components(moieties) in water samples Analysis of other N-DBP species Nitrosamines Haloacetimides

27 Acknowledgements Caitlin Glover, CU Kate Dowdell, CU Carleigh Samson, CU Julie Korak, CU Dorothy Noble, CU Jim Saunders, CDPHE Becky Anthony, CDPHE All participating utilities

28 References Callinan, Clifford. Final Report for the Disinfection By-Product/Algal Toxin Study. Prepared for USEPA Region 2. September McKnight, D.; Boyer, E.; Westerhoff, P.; Doran, T.; Kulbe, T.; Andersen, D. Spectrofluorometric characterization of dissolved organic matter for indication of precursor organic material and aromaticity. Limnology and Oceanography. 46(1), 2001, Summers, R.S.; Hooper, S.; Shukairy, H.; Solarik, G.; Owen, D. Assessing DBP yield: uniform formation conditions. Journal of the American Water Works Association. June 1996.

Relationships Between Disinfection Byproducts and Dissolved Organic Matter in Drinking Water

Relationships Between Disinfection Byproducts and Dissolved Organic Matter in Drinking Water Meng-Horng (Chris) Hsu, I. H. (Mel) Suffet Environmental Science and Engineering Program UCLA Los Angeles, CA