1. DMR Dansk Miljørådgivning A/S 1 Bài tập đất 5 – chương 9 hãy tóm tắt về đặc tính của MBTE và cách thức mà người ta thành công trong xử lý nó như trong các slide sau Nộp lại max 2 trang A4 viết tay Thanh NK To: K13M1&2

2. DMR Dansk Miljørådgivning A/S 2 What is MTBE? MTBE = Methyl tert-butyl ether: Thêm vào gasoline từ những năm 1985 Tại DK thì thêm max.: 3 vol.% (98 octane) Cho phép đốt tốt hơn => less airpollution Như vậy nó ko phải là vấn đề, vấn đề là đặc tính hóa học của nó MTBE’s là ”unfortunate” với đất và nước ngầm.

3. DMR Dansk Miljørådgivning A/S 3 Sức khỏe và MTBE MTBE có hiệu ứng độc tính trực tiếp thấp, như tại Mỹ người ta cho rằng nó gây ung thư ở nồng độ cao. Vấn đề thấy đầu tiên đó là cảm quan: Strong odour and bad taste; even at low concentrations < 20-40 mg/L

4. DMR Dansk Miljørådgivning A/S 4 How often do we find MTBE? US (1998-1999): Found in ~75-93% of investigations made at leaking tank facilities (level > det.limit) Found in 5-10% of drinking wells in areas with addition of 10-15 vol.-% (99% < 20  g/L) DK – County of Fyn (2000): MTBE detectet in the groundwater at 86% of 72 gasoline stations; hereof 53% > 30  g/L Found in the water at 35% (7 out of 20) of potentially threatened water works (level> det.gr.)

5. DMR Dansk Miljørådgivning A/S 5 Đặc tính hóa học của MTBE’s High water solubility: ° Max: 40–50.000 mg/L; Benzene: 1.750 mg/L ° Max solubility in gasoline mixtures: ~ 6.300 mg/L ° Highest concentration measured (US): 1.900 mg/L Low adsorbtion to activated charcoal and soil: ° MTBE has about same velocity as water (R  1 – 1,05) ° Benzene retarded by 20-25% (R  1,25 – 1,33) Low biodegradability: ° Considered non-degradeable until 1994 Low evaporation: ° K h for MTBE: 0,02; Benzene: 0,22

6. DMR Dansk Miljørådgivning A/S 6 Natural transport Stabilization of the contaminated plume will depend primarily on adsorption and degradation MTBE has low tendency to adsorption + degradation => produces long contaminated plumes

7. DMR Dansk Miljørådgivning A/S 7 In-situ remediation techniques Techniques that work under the soil surface Removal of MTBE from saturated and unsaturated zone.

8. DMR Dansk Miljørådgivning A/S 8 On-site remediation Techniques that work over the soil surface Removal of MTBE from pumped air- or waterstream

9. DMR Dansk Miljørådgivning A/S 9 Natural biodegradation Intrinsic biodegradation can be used as remediation tool BTEX vs. MTBE Potential for Intrinsic biodegradation of MTBE

10. DMR Dansk Miljørådgivning A/S 10 Sediments investigated 4 locations with gasoline & MTBE-contaminated groundwater 6 different sediment types Different stories of contamination Direct and propane stimulated biodegradation was studied

11. DMR Dansk Miljørådgivning A/S 11 Definitions Direct MTBE degradation: Microorganisms can grow on MTBE as sole substrate. MTBE serve as both energy- and carbon source. Cometabolic MTBE-degradation: Microorganisms can not survive on MTBE alone. They need another energy- and carbon source..

12. DMR Dansk Miljørådgivning A/S 12 Direct MTBE-degradation Aalborg gytje: High activity in batch no 3 Degradation to under detection limit 2 new additions of MTBE Lack of nutrients (P) after ca. 40 days Batch no3 was divided into 3 new batches after ca. 50 dage

13. DMR Dansk Miljørådgivning A/S 13 Direct MTBE-degradation Aalborg gytje: Similar degradation pattern Renewed high activity MTBE degraded < 6 d Activity increasing with time

14. DMR Dansk Miljørådgivning A/S 14 Cometabolisk MTBE-nedbrydning Ølstykke sediments: Limestone: Concentrations stop decreasing at 2-3 mg/L Sandy moraine clay: Degradation continue below detection limit

15. DMR Dansk Miljørådgivning A/S 15 Degradation rates Rates normalized to dry matter content of the samples

16. DMR Dansk Miljørådgivning A/S 16 Summary Direct MTBE-degradation in 2 (3) of 6 sediments; Propane degradation in all 6 sediments Propane stimulated MTBE degradation in 5 of 6 sediments Basis for intrinsic biodegradation of MTBE

17. DMR Dansk Miljørådgivning A/S 17 Microbial degradation of MTBE Direct degradation MTBE primary substrate Co-metabolic degradation Primary substrate: Propane,Butane, Pentane and other Max degradation rates 280-890 mg MTBE g -1 celler t -1 Max degradation rates 220-490mg MTBE g -1 celler t -1 High affinity for MTBE K m 0.3-2.5 mg/l Low affinity for MTBE: K m 40-240 mg/l High affinitet for primary substrat K m 3.5-9mg/l Low affinitet for O 2 K m 6.2mg/l High affinity for O 2 K m 0.28 mg/l Low growth rate T d 3-30 dage Higher growth rate T d 0.5-1.3 dage Low cell yield Omkring 0.2g/g MTBE High cell yield 0.4-0.9 g/ g substrat

18. DMR Dansk Miljørådgivning A/S 18 Microbial degradation of MTBE MTBE as primary substrate An increasing number of pure and mixed cultures are available. PM1, ENV735 Hydrogenophaga flava BC1 -BC4 Pure and enrichment cultures difficult to grow Cometabolic degradation Primary substrate: Short chain n/iso-alkanes (n=3-6) Mycobacterium vaccae Pseudomonas aeruginosa ENV 425 Enrichment cultures easy to grow from organic rich soil

19. DMR Dansk Miljørådgivning A/S 19 Stimulated in situ degradation TreatmentMTBE halflifeO 2 koncentration Control plot693 days<1 mg/l + O 2 (puls addition) 99 days> 2mg/l - 20mg/l + O 2, + BC-4 (MTBE degrading culture) 18 days> 2mg/l - 20mg/l Example of established biobarriere (Salanitro et al., 1999) Port Hueneme: Gasoline pollution with MTBE (2-8 mg/l). Size of plume 1300m x 130m x 3.5m.

20. DMR Dansk Miljørådgivning A/S 20 SBR biofilter (alternative to chemical charcoal filter) Removal of MTBE from pumped waterstream On-site remediation

21. DMR Dansk Miljørådgivning A/S 21 On site treatment - Sequential batchreactor set up.

22. DMR Dansk Miljørådgivning A/S 22 Substrate kinetics for co-metabolic MTBE degradation

23. DMR Dansk Miljørådgivning A/S 23 Oxygen sensitivity

24. DMR Dansk Miljørådgivning A/S 24 BTEX inhibition of cometabolic MTBE degradation

25. DMR Dansk Miljørådgivning A/S 25 SBR results and model predictions for propane

26. DMR Dansk Miljørådgivning A/S 26 SBR results and model predictions for MTBE

27. DMR Dansk Miljørådgivning A/S 27 Example of SBR biofilter upscaling A full scale SBR facility with the following design criteria ° 5 m 3 /h ° 10°C ° 2 g biomass/L ° 90% removal 10 -> 1 mg MTBE/L Gives the following results: ° Hydraulic retention time < 2 hours ° 2 tanks with volume 10m 3 ° < 1 g propan/g MTBE removed (~ 0,25 Dkr/m 3 )

28. DMR Dansk Miljørådgivning A/S 28 Conclusion Easy to grow propaneoxidizing MTBE-degraders Good perspectives for full scale implementation of SBR bioreactor technology.

29. DMR Dansk Miljørådgivning A/S 29 MTBE degradation pathways TBATBF