Relationships Between Disinfection Byproducts and Dissolved Organic Matter in Drinking Water

Transcription

1 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 1

2 Three common DOM models (A mixture of >1k to 10k -15k Daltons molecules) 3-D polymer Micelle (Sutton and Sposito, 2005) Supramolecular Assemblage 2

3 Environmental Effects of DOM Produce disinfection by-products (DBPs) Health concerns: cancers, low birth rate, etc. THMs HAAs US: total THMs: 80 ug/l total HAAs: 60 ug/l Will become more stringent!! Bind to HOPs with high Kow e.g. PAHs & PCBs Cause membrane fouling Cause re-growth of microorganisms in the distribution systems Bind metals 3

4 Objectives Apply a monitoring program for characterizing DOM in surface water & treated water. Understand the relationship and interaction between THMFP in terms of total THMs conc. and other DOM parameters (Fluorescence Distribution, Size, Polarity, Aromatic Structure, KDOM). 4

5 Methods to Characterize DOM Chemical component - Fluorescence Excitation Emission Matrix (EEM) and Fluorescence Regional Integration (FRI) -UV254, DOC, SUVA = UV254/DOC*100 Size - Ultrafiltration (UF) Polarity - Polarity Rapid Assessment Method (PRAM) DOM-water partition coefficients- (KDOM) - Fluorescence Quenching Method 5

6 Water Treatment Processes Castaic Lake Water Agency- DOC = 2.2 mgc/l Long Beach Water Department- DOC = 2.6 mgc/l 6

7 Fluorescence spectroscopyexcitation-emission matrix (EEM) Chemical component Characterize the component of DOM - Three dimensional map of fluorescence response - Fluorescence peaks (Intensity) - Individual components of DOM can be identified 7

8 Fluorescence Regional Integration (FRI) I: Aromatic Proteins - Tyrosine-like material II: Aromatic Proteins - Tyrosine, BOD 5 III: Fulvic acid-like - Humic substances soluble at all ph IV: Microbial by-products - Tyrosine, tryptophan and IV V protein-like material V: Humic acid like - Humic substances I II III precipitate at ph< 1 All regions are characterized by % Fluorescence Distribution (Chen et al., 2003) 8

9 % Fluorescence Distribution % Fluorescence Distribution Raw Raw-waste Ozone Flocculation Clarifier Filters Clearwells Treated I II III IV V Raw Raw-Cl2 Coagulation Clarifier Filter-influent Filter-effluent Pump station Treated Regions I II III IV V Regions FRI results of processes of CLWA and LBWD I: Aromatic Proteins II: Aromatic Proteins III: Fulvic acid-like IV: Microbial by-products V: Humic acid like Treatment process alters the composition of DOM. Fulvic and humic acids are still the main components after treatment. High humic & fulvic acid input indicate of terrestrially derived sources. Coagulation decreases FA in CLWA and FA & HA in LBWD. How would this affect THMs? 9

10 Ultrafiltration Analysis To fractionate the DOM into different size fractions 1 kda, 5 kda and 10 kda molecular weight cutoff membranes are used Test filtrate: < 1 kda, < 5 kda and <10 kda size fractions DI post DI pre = DI corr F10 DI corr = F10 corr Desired Size Fraction Formula Used > 10 kda B F10 corr 10 5 kda F10 corr F5 corr 5 1 kda F5 corr F1 corr < 1 kda F1 corr 10

11 Raw Raw-waste Ozone Flocculation Treated UF results of CLWA and LBWD % % Bulk 10k-5k 5k-1k <1k Raw Clarifier Treated UF Size Fraction >10k 10k-5k 5k-1k <1k UF Size fraction Ozonation decreases the higher MW and increases the smaller MW fractions in CLWA. Ozonation mainly removes 10k- 5kDa fractions at ph 7.9. CLWA treatment process mainly removes 10k-5kDa fraction. LBWD treatment process mainly removes >10kDa fraction by coagulation (FeCl 3 ) at ph 8.0. The DOM size is altered during the treatment process. How would this affect THMs? 11

12 Polar Rapid Assessment Method (PRAM) Uses solid phase extraction (SPE) cartridges of different functionalities - Polar : Diol (Glyceroxypropylsilyl) - Non-polar: C-18 (Octadecylsilyl) - Anion exchange: NH-2 RC (Retention Coefficient) = Percent of UV absorbing material adsorbed by SPE material RC = 1-A/A o 12

13 100 PRAM results of RC (%) Raw Raw-waste Ozone Flocculation Treated Raw Clarifier Treated C18 Diol NH2 Polarity CLWA and LBWD The DOM polarity is altered during the treatment process. Negative charged fractions decrease in CLWA and LBWD after treatment. Ozonation significantly decreases polar and non-polar fractions. RC (%) C18 Diol NH2 Polarity Coagulation increases polar and non-polar fractions in CLWA. Non-polar fraction is stable and polar fraction increases before and after the treatment in LB. How would this affect THMs? 13

14 DOM-water partition coefficients-(kdom) Fluorescence Quenching Method KDOM is the partition coefficient between HOPs and DOM and describes the binding ability of DOM. KDOM PAH (soluble, free) + DOM <---> PAH-DOM (bound) C = K C s ( w / w) DOM free ( w / v) Cbound = [ DOM ] C total C [ DOM ] free = K [ DOM ] [ DOM ] DOM C K DOM % bound = K DOM free (Carter and Suffet, 1995; Mackenzie et al., 2002) 14

15 KDOM analysis of CLWA and LBWD Water Sample DOC SUVA Log (mgc/l) (L/mg/m) CLWA Raw Ozone KDOM Coagulation Treated LBWD Raw Coagulation Treated

16 Correlations-THMs & DOM Parameters Bulk UV254 for all samples shows the best positive correlation (88%) with Log THMs. This means the more aromatic the structure, the higher the THMs Log THMs LogTHMs R 2 = 0.88 P < 0.05 = 0.73LogUV Log UV 254 (cm -1 ) 16

17 Correlations-THMs & DOM Parameters DOM with higher conc., aromaticity, and molecular weight have more ability to form THMs. Parameters R 2 TOC 0.85 UV SUVA 0.68 TOC for > 10 kda 0.77 TOC for 10-5 kda 0.79 UV 254 for > 10 kda 0.63 UV 254 for 10-5 kda 0.72 UV 254 for 5-1 kda 0.56 UV 254 for < 1 kda 0.71 Some specific aromatic structures existing in < 1 kda size fractions also can lead increasing conc. of THMs. 17

18 Correlations- K DOM & DOM Parameters Log K DOM R 2 LogK = 0.74 DOM = 0.45SUVA SUVA (L mg -1 m -1 ) SUVA for all samples of CLWA and LBWD shows a good positive correlation (74%) with Log K DOM. DOM with higher aromaticity can have better ability to bind with HOPs. 18

19 Correlations- K DOM & DOM Parameters Lower positive correlations of <60% versus Log K DOM Parameters Vs Log KDOM Bulk UV254 FA in Fl 5-10 kda in TOC UV254 of > 10 kda UV254 of 5-10 kda R-square 50% 58% 44% 54% 46% The change of these parameters are not sufficient to understand the mechanism of change of KDOM. In the future, we will look at multi-variance correlation 19

20 PAC Treatment Effects on drinking water quality HYDRODARCO B powdered activated carbon (Nort Americas Inc., USA) was used. Benefits 1) removes the precursors of THMs 2) color and taste 3) the common PAC used in drinking water treatment plant What s the effects of PAC on DOM characteristics monitoring in this study?? 20

21 PAC Treatment Effects- Changes in TOC, SUVA and UV254 PAC decreased TOC, 35% and 38%, and UV, 26% and 39%, for LBWD and MWD raw waters. PAC removed some aromatic parts of the DOM. However, SUVA increased after PAC treatment in LBWD but did not change significantly in MWD. This indicates site specificity of DOM. Size fractions of DOM were adsorbed differently by PAC. This also indicates site specificity of DOM. 5 TOC SUVA UV (HYDRODARCO B (Nort Americas Inc., USA) Bulk 20 ppm Bulk 20 ppm Changes of TOC, SUVA and UV254 after 20 mg/l PAC reacted with (a) LBWD & (b) MWD raw water. 21

22 Change of KDOM and THMs during Water Treatment After PAC treatment, THMs decreased 22% and 26% for LBWD and MWD, nonetheless, KDOM for hydrophobic organic pollutants(hops) remained constant. The THMs decrease is due to bulk TOC and UV254 decreases and some size fractions of DOM decreases causing removal of THMs reaction sites on the DOM. KDOM remained constant as sufficient binding sites to PAHs remained: KDOM PAH (soluble, free) + DOM <---> PAH-DOM (bound) KDOM is the partition coefficient between HOPs and DOM and describes the binding ability of DOM TOC (mgc/l) LBWD Log K DOM THMs (µg/l) TOC (mgc/l) MWD Log K DOM THMs (µg/l) Raw Raw+PAC

23 Conclusions Objective: Understand the relationship and interaction between THMFP in terms of total THMs conc. and other DOM parameters (Fluorescence Distribution, Size, Polarity, Aromatic Structure). Bulk TOC (85%), UV254 (88%) and SUVA (68%) show positive and high correlation with THMs. This indicates the more total DOM and aromatic the structure, the higher the formation of THMs. TOC for > 10 kda (77%), 10-5 kda (79%) and UV254 for > 10 kda (63%), 10-5 kda (72%) show positive and high correlation with THMs. This indicates DOM with higher molecular weight and aromatic structure can form more THMs. Understand the correlations between different characteristics of DOM and DBPs => assist to optimize water treatment agency operation!! 23

24 Conclusions PAC treatment PAC (20 mg/l) can remove 35-38% of DOM from LBWD & MWD raw waters. PAC can remove aromatic contents, a portion of fulvic acids and nonpolar parts of DOM that might be the precursors of THMs and thus decrease THMs formation. On the other hand, raw water samples of LBWD & MWD still had the same KDOM values after PAC removed DOM and thus continued to keep its ability to bind with HOPs and keep HOPs less bioavailable in the DOM-HOPs complex. Therefore: Under the conditions studied, PAC is an effective method to control: 1) THMs and 2) The hazard potential of HOPs The approach of this study can guide water agencies towards optimization of water treatment processes and obtaining better water quality. 24

25 Conclusions Objective : Apply a monitoring program for characterizing DOM in surface water & treated water. Water treatment process alters the composition of DOM as shown by changes of size distribution, polarity and fluorescent character of DOM UF - DOM size distribution PRAM - DOM polarity Fluorescence Excitation Emission Matrix (EEM) and Fluorescence Regional Integration (FRI) - chemical component TOC - DOM total conc. Effectively characterize DOM Quick, Cost Effective Can be applied in drinking water treatment plants process water, source water, or stormwater as daily monitoring to disentangle DOM complexity UV254 - DOM aromatic structure 25

26 Thank you. Can I make anything clearer?

27 References Carter, C. W. ; Suffet. I.H.. Environ. Sci. Technol. 1982, 16, Chen, W.; Westerhoff, P.; Leenheer, J. A.; Booksh, K. Environ. Sci. Technol. 2003, 37, Gauthier, T. D.; Shane, E. D.; Guerin, W. F.; Sitz, W. R.; Grant, C. L. Environ. Sci. Tech. 1986, 20, Mackenzie, K.; Georgi, A.; Kumke, M.; Kopinke, F-D. Environ. Sci. Tech. 2002, 36, Ramos, E. U., Meijer, S. N., Vaes, W. H. J., Verhaar, H. J. M., Hermens, J. L. M. Environ. Sci. Technol. 1998, 32, Revchuk, A.D.; Suffet, I.H. Water Research. 2009, 43, Rosario-Ortiz, F.L.; Snyder, S.; Suffet, I.H Environ. Sci. Technol. 2007, 41, 14, Rubhun, M.; Meir, S.; Laor, Y. Environ. Sci. Technol. 1998, 32, Sutton, R; Sposito, G. Environ. Sci. Technol. 2005, 39, 23,

28 Changes of DOM Polarity After PAC Treatment The DOM charge decreases, Hydrophobicity decreased, & Hydrophilicity increased. By decreasing the negative charges and non-polar fractions, the polar fractions increased Bulk 20ppm (a) Bulk 20ppm (b) RC (%) RC (%) C18 Diol NH2 0 C18 Diol NH2 Polarity Polarity PRAM analysis of PAC dose 20 mg C/L reacted with (a) LBWD and (b) MWD raw water.

29 Changes in DOM Fluorescence After PAC Treatment Fluorescence shows: PAC used in this study adsorbed more fulvic acids and aromatic proteins. After this occurred, the DOM had a larger microbial by-products fraction. % Fluorescence Distribution Bulk 20ppm I: Aromatic proteins I II: Aromatic proteins II III: Fulvic acids TOC= 2.6 mg C/L IV: Microbial byproducts V: Humic acids I II III IV V (a) % Fluorescence Distribution Bulk 20ppm TOC= 2.6 mg C/L I II III IV V (b) Regions Regions FRI results of PAC dose 20 mg C/L reacted with (a) LBWD and (b) MWD raw water.

30 Changes in DOM Size Fractions After PAC Treatment TOC Different for Each Water Source & % Removal was different LBWD- PAC removed DOM sizes > 10 kda, 5-1 kda & < 1 kda; 10-5 kda remained. MWD- PAC removed DOM sizes > 10 kda & < 1 kda; 10-5 kda & 5-1 kda remained. At PAC dose of 20 mg/l: %Removal TOC: LBWD- TOC= 35%; MWD= 38%. TOC (mg C/L) (a) > 10k 10k-5k 5k-1k <1k Bulk 20ppm TOC= 2.6 mg C/L >10k 10k-5k 5k-1k <1k UF Size Fraction UF Size Fraction UF analysis in mg C/L by TOC of PAC dose 20 mg/l reacted with (a) LBWD and (b) MWD raw water. TOC (mg C/L) TOC= 2.6 mg C/L (b) Bulk 20ppm

31 Changes in DOM Size Fractions After PAC Treatment UV254 absorbance- Different for Each Water Source LBWD- PAC removed DOM sizes 10-5 kda, 5-1 kda, < 1 kda; > 10 kda remained. MWD- PAC removed DOM sizes > 10 kda, 10-5 kda, < 1 kda; 5-1 kda remained. At PAC dose of 20 mg/l: %Removal UV: LBWD- 26%; MWD- 39%. DOM removal mechanisms were different for TOC and UV254 analysis. UV254 absorbance(cm -1 ) (a) Bulk 20ppm UV254 absorbance (cm -1 ) Bulk 20ppm (b) 0.00 >10k 10k-5k 5k-1k <1k >10k 10k-5k 5k-1k <1k UF Size Fraction UF Size Fraction UF analysis byuv254 abs. (cm-1)- PAC dose 20 mg/l reacted with (a) LBWD & (b) MWD raw water.