Oxidative Treatment of Trace Organic Contaminants in Wastewater Effluents

Transcription

1 Oxidative Treatment of Trace Organic Contaminants in Wastewater Effluents by O 3 and O 3 / 2 O 2 Myint Myint Sein*, Alexandra Jarocki*, Torsten C. Schmidt*, Alfred Golloch*, Clemens von Sonntag** *University of Duisburg-Essen, Instrumental Analytical Chemistry, Lotharstr. 1, Duisburg, Germany **Max Planck Institute for Bioinorganic Chemistry, Stiftstr , Mülheim an der Ruhr, Germany EnviroWater, 2-4 March 2009

2 Outline Introduction Oxidation processes (Direct ozonation, Objective Experimental Results Conclusion Radical reaction) EnviroWater, 2-4 March 2009

3 Introduction Modern wastewater treatment plants are very effective, but traces of organic pollutants are still detected In order to protect the environment these organic pollutants must be removed One of the most promising techniques to solve the problem is the treatment of the wastewater effluents by ozonation EnviroWater, 2-4 March 2009

4 Oxidation Processes Use of Ozone: Disinfection Oxidation of organic micropollutants Two possible pathways during ozonation: Oxidation by direct ozone (olefins, amines, phenols, aromatics with ē donors) Oxidation by free. O Radicals Oxidant Species ydroxyl radicals O Oxygen radical O Oxidation Potential (V) O 3 + M O - At higher p M ox Direct reaction (k O3 = M -1 s -1 ) O + M M' ox Radical reaction (k O = M -1 s -1 ) Ozone O 3 ydrogen peroxide 2 O 2 Chlorine Cl These reaction pathways take place simultaneously.

5 Limitations of Use of Ozone Some organic compounds are refractory towards ozone attack igh energy demand and the handling Formation of BrO 3- (max. allowed limit 10 µg/l in drinking water) To overcome these drawback, ozonation process alone is being modified to increase the oxidising capability Advanced Oxidation Process (AOP) e.g, Oxidation by 2 O 2 + O 3 (Peroxone process) 2 O O 3 2. O + 3 O 2 AOP has become an attractive and increasingly important research field in the use of ozone

6 Objective To investigate the removal efficiency of the selected trace organic substances in wastewater effluent by treating with O 3 and 2 O 2 + O 3 EnviroWater, 2-4 March 2009

7 Selected Organic Trace Pollutants in Wastewater Effluents Diclofenac Substance (non-steroidal anti-inflammatory drug) Tri-n-butyltin chloride (Organotin compounds) Iopamidol (X-ray contrast medium) Tri n-butylphosphate (TnBP) Tris-(1-chloro-2-propyl)- phosphate (TCPP) Uses Commonly used pain killer. 86 t a -1 in Germany (2003) Fungicides (in wood, textiles, paints) Endocrine disruptors In the category 1 in the priority list of compounds. No longer allowed since 1993 in Europe Applied in doses up to 200 g per Person. The global consumption is ~3500 t a -1. Rapidly excreted unchanged Mainly used as a plasticizer, an additive in the clothing industry Used as a flame retardant, applied in insulation for buildings and in refrigerator casings

8 The Reaction Rate Constants of these Selected Organic Trace Pollutants Substances k O 3 (M-1 s -1 ) k O (M -1 s -1 ) (1) Diclofenac 6.3 x x 10 9 (2) Tributyltin Chloride (3) Iopamidol x 10 9 (4) Tributylphosphate (TnBP) ~ x (5) Tris-(1-chloro-2-propyl)- phosphate (TCPP) < 1 - -CO 3 - -CO 3 2- (Radical scavengers) <<1 x 10-2 <1 x x x 10 8

9 Experimental Oxidation (Pure ozonation) Z spec. (AOP) Dose of 2 O 2 mg /mg DOC mg /mg DOC The spec. ozone consumption: Z spec. (mg/ mg) = [ (G O3, gas in G O3, gas out ) Q x dt (D O3 x V)] / DOC G O3 = the gas ozone concentration (mg/l G ) Q = the gas flow rate (L/min) t = the reaction time (min) D O3 = the dissolved ozone concentration (mg/l w ) V = the water volume treated (L) DOC = dissolved organic carbon (mg/l)

10 The Continuous Ozone Reaction of Spiked Wastewater Effluent O 3 analyzer O 3 outlet O 2 O 3 generator Organic compound 150 L/hr O 3 inlet 45 L Reactor 150 L/hr 2 O 2 solution Wastewater effluent p 8 Sample collector

11 Ozone Decomposition in Water Ozone decomposes rapidly in water - igh p, high Temp. - high DOC Before ozonation After ozonation *(t ½ : 0.35 s at DOC 8.5 mg/l; ~ 0.5 s at DOC 4.5 µg/l) [O 3 ] 0 = 4 mg/l * Buffle et al., Water Research, 40(9), 1884, 2006.

12 Results Diclofenac (Non-Steroidal Anti-Inflammatory Drug) OOC N O 3 Cl OOC N Cl Cl O 3 Cl Possible sites of ozone attack EnviroWater, 2-4 March 2009

13 Elimination of diclofenac from wastewater effluent by Ozone (C 0 = 10 mg/l, DOC = 10 ppm, p = 8) Elimination (%) [O 3 ] mg/ DOC Diclofenac k O3 (M -1 s -1 ) 6.3 x 10 5 K O (M -1 s -1 ) 7.5 x 10 9 Well eliminated by ozone direct reaction or/and radical type reaction. O 3 dose 1 mg/ DOC eliminates > 90% diclofenac.

14 Main Degradation Pathway of Diclofenac during Ozonation O C O C 2 Cl N Cl O 3 / O 50 COO C 2 Cl N O Cl O 3 / O Cl 2 N C l [Diclofenac] and [Products] / µm O COO C 2 N Cl Cl [Ozone] / µm ( Diclofenac Iminoquinone (major intermediate) 2,6-Dichloroaniline) Sufficient amt. of ozone is needed to eliminate diclofenac and its OPs M. M. Sein et al., Oxidation of diclofenac by ozone, Environ. Sci. Technol, 42(17), 6656, 2008.

15 Tri-n-butyltin Chloride n-butyltin compounds, (Bu (4-n) n)-sn-x n ) (n=1,2,3), (X= Cl, Br, I) Toxicity (Bu) 3 -Sn-X >>> (Bu) 2 -Sn-X >> Bu-Sn-X 2 3 (TBT) (DBT) (MBT) EnviroWater, 2-4 March 2009

16 Elimination of TBTCl from wastewater effluent by ozone and ozone + 2 O 2, (C 0 = 100 µg/l; DOC = 10 ppm, p = 8) Elimination of TBTCl 100 µg/l 1 mg O3 / DOC 2 mg O3 / DOC Elimination (%) without 2O2 1 mg 2O2/DOC 2 mg 2O2/DOC k O3 (M -1 s -1 ) K O (M -1 s -1 ) Reaction products TBT chloride DBT, MBT In pure ozonation, the main reaction pathway must be the radical reaction. ~ 80% TBTCl can be eliminated by 1 mg O 3 /DOC. igher O 3 dose can increase the elimination efficiency, > 90%.

17 Iopamidol (X-Ray Contrast Medium) EnviroWater, 2-4 March 2009

18 Elimination of iopamidol from wastewater effluent by ozone and ozone + 2 O 2 ; (C 0 = 200 µg/l; DOC = 10 ppm, p = 8) Elimination of iopamidol (200 µg/l) 1 mg/l O3 2 mg/l O Elimination (%) w ithout 2O2 0.5 mg 2O2/DOC 1 mg 2O2/DOC Iopamidol k O3 (M -1 s -1 ) 1.4 K O (M -1 s -1 ) 2.8 x 10 9 The main reaction pathway must be by radical reaction. Elimination efficiency can be increased by higher O 3 dose >90%. Addition of 2 O 2 does not much enhance the elimination efficiency.

19 Organophosphates 3 C C C C O C O P O C C O C C C Tri-n-butylphosphate TnBP C 3 C 3 3 C O 3 C C 2 Cl C O P O C C 3 O C C 2 Cl C 2 Cl Tris-2-chloroisopropylphosphate TCPP EnviroWater, 2-4 March 2009

20 Elimination of TnBP (left) and TCPP (right) from wastewater effluent by ozone and ozone + 2 O 2 (C 0 = 25 µg/l; DOC = 10 ppm, p = 8) Elimination (%) mg O3 / DOC 2 mg O3/ DOC Elimination (%) mg O3 / DOC 2 mg O3 / DOC without 2O2 1 mg 2O2/DOC 2 mg 2O2/DOC 0 without 2O2 1 mg 2O2/DOC 2 mg 2O2/DOC k O3 (M -1 s -1 ) K O (M -1 s -1 ) TnBP x TCPP < 1 - The main reaction pathway must be by radical reaction. Elimination efficiency is improved by higher O 3 dose. The addition of 2 O 2 can enhance the elimination to a some extent.

21 Formation of Bromate during Ozone Reaction 140 Bromate [µg/l] O3 ini = 10 mg/l O3 ini = 20 mg/l y = 0,3239x + 3,8618 y = 0,0854x - 6,5342 [Bromate] / µg L Z spec = 0.8 (9 mg/l O 3 ) Z spec = 0.91 (10 mg/l O 3 ) 0 0,5 1 1, Bromide [µg/l] Influence of Br - concentration in the formation of BrO 3 - during ozonation of wastewater effluent (DOC = 14.2 mg/l, TIC = 45 mg/l, p = 8, T = 20 C) (Schumacher, J., PhD Dissertation, Berlin, 2006). Z spec Bromate formation during ozonation of wastewater effluent (DOC = 11.1 mg/l, [Br - ] 0 = 110 µg/l) (Nöthe, T., PhD Dissertation, Dortmund, 2009). BrO 3- formation depends on: -p -DOC - Initial Br - -O 3 exposure

22 To Control the BrO 3- Formation Dosing of N 3 / N 4 + can reduce 40% of BrO 3 - formation. Br - + O 3 BrO - + O 2 BrO 3 - BrO - + N 3 2NBr + O- EnviroWater, 2-4 March 2009

23 Conclusion Oxidation by O 3 turned out to be a promising approach for treatment of wastewater effluents. At higher p, O 3 decomposes into O and thus a concentration reduction of the organic pollutants is achieved. Ozonation of wastewater effluent can be applied in practice (Total cost 5 cent/m 3 at Z spec = 2 mg/mg DOC 0 ) In pure ozonation, the elimination depends on the O 3 concentration. Addition of 2 O 2 (AOP) enhances the elimination only to some extent. EnviroWater, 2-4 March 2009

24 Acknowledgement Federal Ministry of Education and Research Bundesministerium für Bildung und Forschung (BMBF) EnviroWater, 2-4 March 2009

25 Thank you for your attention EnviroWater, 2-4 March 2009