Characterization of DOM Removal by Full- Scale Biological Activated Carbon (BAC) Filters Having Different Ages

Transcription

1 Fourth IWA Specialty Conference on Natural Organic Matter: From Source to Tap and Beyond Hilton Orange County Costa Mesa, California July 27 29, 2011 Characterization of DOM Removal by Full- Scale Biological Activated Carbon (BAC) Filters Having Different Ages J. Lohwacharin, Y. Yang, N. Watanabe, A. Phetrak, H. Sakai, M. Murakami, K. Oguma, and S. Takizawa July 27 th, 2011 Urban Water Systems laboratory, Dept. of Urban Engineering, the University of Tokyo

2 Outline of presentation 1. Background 2. Scope and objectives of study 3. Materials and methods i. Assimilable organic carbon (AOC) determination ii. Bacterial regrowth potential (BRP) analysis iii. Batch adsorption and desorption experiments 4. Results i. DOC treatability ii. DOM characterization iii. Biostability 5. Conclusion remarks 6. Question and suggestions? 2011 Jul 27 J. Lohwacharin et al. 2

3 The Global Carbon Cycle The terrestrial C cycle 1. Biological C fixation 2. C mineralization Soil carbon pools 1. Dissolved organic carbon 2. Humic substances Source: (uploaded on 24 Jun 2011) 2011 Jul 27 J. Lohwacharin et al. 3

4 Classifying natural dissolved organic matter Dissolved organic matter (DOM) Colloidal OM Hydrophobic OM Transphilic OM Hydrophilic OM Acids Neutrals Bases Acids Neutrals Bases Bacterial peptidoglycans Fulvic acid Hydrocarbons /tannins Aromatic amines Polyuronic acids Sugars Peptides/ amino acids Adopt from Leenheer and Croué, ES&T Jul 27 J. Lohwacharin et al. 4

5 DOM serves as organic substrate for bacterial regrowth 1. Biodegradable organic carbon (BDOC) 1. Employing incubation period ( 28 days). 2. Utilizing indigenous microbes in water. 2. Assimilable organic carbon (AOC) 1. Estimating biodegradable organic matter from number of bacteria growing in water. 2. Utilizing Pseudomonas fluorescens strain P17 and Aquaspirillum sp. strain NOX (Van der Kooij et al., 1982; APHA, 2005) or others. TOC POC DOC NBOC BDOC e.g. HS AOC P17 NOX e.g. amino acids, carbohydrates, aromatic compounds e.g. mainly carboxylic acids 2011 Jul 27 J. Lohwacharin et al. 5

6 Ozonation biological activated carbon (BAC) process 1. Granular activated carbon (GAC) adsorption 1. One of the best available methods for DOM removal (Pontius, 1996). 2. Ozonation 1. Degrading odorous materials and DBP precursors (Siddiqui et al., 1997). 2. Increasing concentration of AOC (van der Kooij and Hijnen, 1984; Janssens et al., 1984). 3. Ozonation BAC process AOC Ozonation AOC BAC Adsorption Biodegradation AOC Ozonation by-products Carboxylic acids Ketones Aldehydes Microbial development Changes in BAC treatment mechanisms DOC and AOC removals Siddiqui et al., Jul 27 J. Lohwacharin et al. 6

7 Three-stage DOC removal by BAC filter Adopt from Simpson (2008) 1. Period A: Physical adsorption mode. 2. Period B: Transition phase i.e., physical adsorption declines, while the degree of biodegradation increases. 3. Period C: Mainly biodegradation Jul 27 J. Lohwacharin et al. 7

8 Scope and Objectives of Study Water sampling at one of a fullscale drinking water treatment plants in Japan Along water treatment process trains, targeting ozonation and BAC filters. Seasonal variation. DOM characterization Chemical properties e.g. DOC, UVA 254, 3D fluorescence EEM. Physical properties e.g. MW distribution (HP-SEC). Biostability level i.e. AOC and bacterial regrowth potential (BRP) determinations. Objectives of Study 1. To investigate the changes in BAC treatment mechanisms by characterizing DOM in the BAC filter effluent as BAC ages in a full-scale drinking water treatment system. 2. To determine biostability levels after BAC filters of various service time Jul 27 J. Lohwacharin et al. 8

9 Water samples Cl 2 Materials Cl 2 Raw water Coagulation/1 st rapid sand filtration Ozonation BAC filters 2nd sand Distribution New GAC was replaced during Nov Dec weeks weeks weeks 6 yrs Ozone dose and water quality of ozonation effluent BAC filters: Retention time 15 min 250 m/day Parameter Unit Average Stdev Min Max DOC * mg/l UVA 254 * cm ph * Ozone dose mg-o 3 /L (mg-o 3 /mg-doc) (0.47) (0.22) (0.21) (0.93) Residual ozone mg-o 3 /L Temperature C * Samples were prefiltered with 0.45-μm PTFE membrane Jul 27 J. Lohwacharin et al. 9

10 AOC determination Method 33 μl of 30 g/l Na 2 S 2 O μl of mineral medium 1) Pasteurized at 75ºC, 30 min 2) Cool down Strains P17 + NOX (Initial 500 CFU/mL each) 3) Incubated at 15ºC 7 9 days 4) Colony count by spread plate on R2A agar 5) Incubated at 25ºC, 3 4 days NOX P17 40 ml N max Y ( CFU/mL) 1000 ( ml/l) ( CFU/ μg acetate C/L) = AOC ( μg acetate C/L) N max is the maximum colony count (CFU/mL). Y is a yield coefficient: CFU/μg acetate-c (strain P17) and CFU/μg acetate-c (strain NOX) (van der Kooij and Hijnen, 1984; van der Kooij and Veenendal, 1995) Jul 27 J. Lohwacharin et al. 10

11 BRP analysis Method The BRP method is based on the growth of inoculated indigenous microbes in sterilized water samples with a minor modification made to the method proposed by Sathasivan and Ohgaki (1999). 19 ml of sterilized sample + 1 ml of concentrated (20x) inocula (initial CFU/mL of original water sample) 20 ml 100 rpm 45º 1) Incubated at 20ºC 5 days 2) Colony count by spread plate on R2A agar 3) Incubated at 20ºC, 7 days Mixed cultures BRP (CFU/mL) = colony count the number of bacteria in the inocula 2011 Jul 27 J. Lohwacharin et al. 11

12 Virgin GAC and 6-years-service BAC Materials Top BAC Mid BAC Bottom BAC 500 μm 500 μm 500 μm Parameter GAC BAC (Top) BAC (Mid) BAC (bottom) BET surface (m 2 /g) Pore volume (cm 3 /g) Pore diameter (nm) Measured using a BELSORP-mini II volumetric adsorption analyzer (BEL Japan Inc., Osaka, Japan) Jul 27 J. Lohwacharin et al. 12

13 Adsorption test and Analytical methods Adsorption isotherm/desorption test: three-vial-one point technique. Ozone effluent used as an adsorbate solution. One dosage 3 x 7 vials + one control Horizontally shaking at 120 rpm and 25ºC for 4 or 25 days. Analytical methods Parameter Method Analyzer Dissolved organic carbon (DOC) Apparent MW Non-purgeable organic carbon (NPOC) Size exclusion chromatography TOC-5000A Shimadzu (Japan) LC-10ADvp Shimadzu on Protein Pak60 Waters (USA) DOM component 3D fluorescence EEM Hitachi F-4500 (Japan) Phosphate Ion chromatography 861 compact IC Metrohm (Switzerland) 2011 Jul 27 J. Lohwacharin et al. 13

14 DOC treatability and Biostability RESULTS AND DISCUSSION 2011 Jul 27 J. Lohwacharin et al. 14

15 DOC (mg-c/l) DOC distribution along the treatment process SUVA 254 Raw 1st sand Ozone BAC filters 1. DOC removals: 29% by coagulation-1 st rapid sand filtration. 54% of ozone effluent by BAC filters. 2. Significant reduction of SUVA 254 after 1 st sand filtration and ozonation. n/a 2nd sand Mean temperature ( c) Jul 27 J. Lohwacharin et al SUVA 254 (L/mg-m) Dec 16-Dec 27-Dec 18-Jan 15-Feb 7-Mar 22-Apr 2-Jun 14-Jun SUVA25 4 SUVA 254 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Avg. precip. (mm) Source: weather.com

16 DOC treatability by BAC filters Effluent DOC/Influent DOC Adsorption 50 % removal Non-adsorbable DOM Adsorption + biodegradation Biodegradation Service time (weeks) 40 weeks (10 months) DOM removal process shifted from physical adsorption to biodegradation between 30 and 54 weeks (after 40 weeks service) Jul 27 J. Lohwacharin et al. 16

17 DOC removal rate (mol/m 3 BAC h) DOC removal rates μm 1-4 weeks weeks Adsorption shifted to biodegradation weeks 100 μm 100 μm 6 years 1. Elimination of adsorptive sites on BAC. 2. Increase in biological activities Jul 27 J. Lohwacharin et al. 17 Average BET surface area (m 2 /g) Top Mid Bottom 100 μm Accumulation of organic and inorganic compounds.

18 SUVA 254 of BAC filter effluent SUVA 254 (L/mg-m) Ozone effluent SUVA Service time (weeks) weeks Ozone effluent 1. SUVA 254 remained at a similar level (1.34 L/mg-m) to that of ozone effluent at transition period. 2. Increase in the SUVA 254 was associated with increased biodegradation as water temperature went up. SUVA 254 (L/mg-m) 2011 Jul 27 J. Lohwacharin et al Ozone effluent SUVA 254 SUVA DOC removal (%) Water temperature ( C) DOC removal (%)

19 MW distribution of DOM in BAC filter effluent 661 UVA 254 response 6 years weeks weeks weeks 3 3 weeks weeks Ozone effluent Molecular weight (Da) Phosphate buffer ph 6.8, Protein Pak60 column (Waters Corp., USA) 2011 Jul 27 J. Lohwacharin et al. 19

20 MW of DOM in BAC filter effluent M W (Da) M w = N h M i i= 1 N h i= 1 M w of ozone effluent DOM removed by new BAC i i DOM desorbed from aged BAC Service time (weeks) h i is the height of the UVA chromatogram at any elution time. M i is obtained from a calibration curve of PSS salt standards. q e (mg-c/g-gac) Desorbed amount (mg-c/g-bac) 10 Desorption C e (mg-c/l) 10 Adsorption q e = 5.65(C e /D 0 ) q e = 3.72(C e /D 0 ) days Predicted_4 days 25 days Predicted_25 days C e /D 0 (mg-c/g-gac) 2011 Jul 27 J. Lohwacharin et al. 20

21 Aromatic-rich DOM desorbed from aged BAC UVA 254 response g/l Ozone effluent + NaN g/l 0.5 g/l Molecular weight (Da) Ozone effluent 100 After 25-day desorption with ozone effluent (+0.1 N NaN 3, ph 7.7, 25ºC, 120 rpm). DOC: 1.0 mg/l Ex (nm) Ozone effluent + 0.1N NaN Control Em (nm) Ex (nm) Desorption BAC 2 g/l Raman unit (R.U., nm -1 ) After desorption Em (nm) Ex (nm) Em (nm) Fluorophore Symbol Humic-like C Fulvic-like A M C A Marine humic-like M DOM desorbed from 6-year-service BAC showed humic-like and fulvic-like signatures with MW of 1,150 and 2,300 Da Jul 27 J. Lohwacharin et al. 21

22 3D F-EEM across the treatment process Ex (nm) Ex (nm) Ozone influent O 3 influent M B T B T C A Em (nm) 13-week-service BAC 13 weeks BAC Em (nm) Ex (nm) Ex (nm) Ozone effluent O 3 effluent M B T B T C A Em (nm) 44-week-service BAC weeks BAC Em (nm) Ex (nm) Em (nm) Fluorophore Symbol Humic-like C Fulvic-like A Marine humiclike Ex (nm) year service BAC Em (nm) 6 years BAC Tryptophan protein-like Tyrosine-, protein-like Raman unit (R.U., nm -1 ) M T B Source: Coble, 1990; Hudson et al., 2007 Samples were collected on 15 Feb Jul 27 J. Lohwacharin et al. 22

23 Assimilable organic carbon (AOC) AOC μg acetate C/L to 184 μg-c/l 184 to 62 μg-c/l 66% NOX P17 DOC 2 1 DOC concentration (mg/l) Samples were collected on 15 Feb 11 Total AOC = AOC NOX + AOC P17 P17 0 Raw water 1st sand effluent Ozone effluent 13-week BAC 44-week BAC 6-year BAC 0 AOC-P17: e.g. amino acids, carbohydrates, some carboxylic acids, alcohols, some aromatic compounds 1. Ozonation markedly increased the AOC concentration. 2. The 6-year BAC was effective in removing AOC-P17, providing the total AOC level of 62 μg acetate-c/l Jul 27 J. Lohwacharin et al. 23

24 Bacterial regrowth potential (BRP) Colony count (x10 5 CFU/mL) Raw water 89 μg-p/l Raw water 1st sand effluent Ozone effluent 26-week BAC 30-week BAC BRP PO4 4 -P DL of PO 4 -P 61-week BAC 6-year BAC Samples were collected on 14 Jun 11 PO 4 concentration (μg-p/l) Ozone effluent 6-year BAC 61-week BAC 1. Ozone increased BRP level by CFU/mL, but based on N max of AOC, ozone increased N max by CFU/mL (strain NOX) and CFU/mL (strain P17). This suggests that P is nutrient limiting in the ozone effluent. 2. BRP declined by 45% with 6-year-service BAC, providing a minimum BRP level of CFU/mL Jul 27 J. Lohwacharin et al. 24

25 Change in levels of BRP by P addition Colony count ( 10 5 CFU/mL) BRP BRP-P BRP/P BRP/P ( 10 7 CFU/μg-P) Samples were collected on 22 Apr 11 BRP: without adding PO 4 -P BRP-P: adding PO 4 -P (Na 2 HPO 4 ) to the initial P concentration of raw water BRP/P: increased colony count per μg-p added. 1st sand effluent Ozone effluent 54-week BAC The rates of colony count increased (CFU/μg-P) suggest that P became a nutrient limiting in the ozone effluent ( CFU/μg-P), whereas easily biodegradable organic carbon might be a nutrient limiting in the effluents of primary sand-filtration and BAC filters Jul 27 J. Lohwacharin et al. 25

26 Concluding remarks 1. The major DOM removal process shifted from physical adsorption to biodegradation between 30 and 54 weeks. 2. The initial stage BAC removed 87% of DOC, of which DOM having MW larger than 1,000 Da was preferentially removed but the removal declined as BAC aged. 3. Both AOC and BRP results indicated that DOM supporting bacterial growth can be removed more efficiently by aged BAC than new BAC despite the results that aged BAC had lower DOC removal rates than new BAC Jul 27 J. Lohwacharin et al. 26

27 References 1. APHA, 2005, Standard methods for examination of water and wastewater. 21 th edn., Washington, DC. 2. Coble, P.G. 1996, Marine Chem. 51(4), Hudson, N., Baker, A. & Reynolds, D. 2007, River Res. Applic. 23, Janssens, J.G., Meheus, J. & Dirickx, J. 1984, Wat. Sci. Technol. 17, Leenheer, J.A. & Cruoé, J.P ES&T, 37(1), 18A-26A. 6. Pontius, F.W. 1996, J. Am. Water Works Assoc. 88(3), Sathasivan, A. & Ohgaki, S. 1999, Water Res. 33(1), Siddiqui, M.S., Amy, G.L. & Murphy, B.D. 1997, Water Res. 31(12), Simpson, D.R. 2008, Water Res. 42, van der Kooij, D. & Hijnen, W.A.M. 1984, Appl. Environ. Microb. 47(3), van der Kooij, D. & Veenendaal, H.R Determination of the concentration of easily assimilable organic carbon (AOC) in drinking water with growth measurement using pure bacterial cultures. The AOC manual SWE , KIWA, Nieuwegein, Netherlands. 12. van der Kooij, D., Visser, A. & Hijnen, W.A.M. 1982, J. Am. Water Works Assoc. 74(10), Jul 27 J. Lohwacharin et al. 27

28 Acknowledgements This study was supported by the Environment Research and Technology Development Fund (S-8) of the Ministry of the Environment, Japan, Grant-in-Aid for Scientific Research (# ), the CREST Project Fund by JST, and the JSPS Postdoctoral Fellowship (# ), provided by Japan Society for the Promotion of Science. The authors thank to persons in charge at the water treatment plant for water sampling management. Thank You for Your Kind Attention 2011 Jul 27 J. Lohwacharin et al. 28