1. 10th International Conference on Clean Energy (ICCE-2010) Famagusta, N. Cyprus, September 15-17, 2010 Flocculation of Microalgal Biomass for Biofuels Production by Flocculation using pH Adjustment and Coagulant Addition RifkaAisyah1, Kuei-Ling Yeh1, Chun-Yen Chen1,2 and Jo-Shu Chang 1,2,3 1Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan 2Sustainable Environment Research Center, National Cheng Kung University, Tainan, Taiwan 3Center for Biosciences and Biotechnology, National Cheng Kung University, Tainan, Taiwan 1st University Road, National Cheng Kung University, Tainan, 701, Taiwan Corresponding author: email: changjs@mail.ncku.edu.tw

3. The ability to address some major limitationsassociated with the application of first and second generation of biofuels

4. Capability of all round year production

5. Be able to be cultivated in non-productive land2

7. The costrequired for downstream processing can be up to

8. Biofuels are low-value productsHARVESTING IS VERY CHALLENGING! 20-30% of the total costs production Harvesting should be energy-efficient and relatively inexpensive

10. Allowsrapid handling of large quantities of microalgal culturesCentrifugation Flocculation Filtration Flotation Electrolytic process Gravity sedimentation

12. Al2(SO4)3

13. FeCl3

14. etcPolyelectrolyte addition Bioflocculation

15. The Objectives of Study To compare the performance of two types of flocculation methods, flocculation using pH adjustment and flocculation using AlCl3 as coagulant To evaluate the influence of initial biomass concentration and coagulant concentration on flocculation performance 6

16. Species Chlorella vulgaris ESP-31 Culture condition 7 MethodsMICROALGAL STRAIN AND CULTIVATION CONDITION

18. 0.67 g/l (OD688, initial = 3.36)

19. 1.27 g/l (OD688, initial = 6.34)

20. Final pH = 10.00 and 12.00, respectively

21. Working volume = 250 ml

22. Initial pH = 7.00

23. 0.47 g/l (OD688, initial = 2.35)

24. 1.55 g/l (OD688, initial = 7.76)

25. 2.60 g/l (OD688, initial = 13.00)

26. AlCl3 concentration = 0; 0.1; 0.3; 0.5; 0.7; 0.9; 1.5 g/l

28. 0.67 g/l (OD688, initial = 3.36)

29. 1.27 g/l (OD688, initial = 6.34)

30. Final pH = 10.00 and 12.00, respectively

31. Working volume = 250 ml

32. Initial pH = 7.00

33. 0.47 g/l (OD688, initial = 2.35)

34. 1.55 g/l (OD688, initial = 7.76)

35. 2.60 g/l (OD688, initial = 13.00)

36. AlCl3 concentration = 0; 0.1; 0.3; 0.5; 0.7; 0.9; 1.5 g/l

38. MethodsFLOCCULATION USING AlCl3 AS COAGULANT Add AlCl3 (g/l) 0.5 0.1 0.3 0.7 0.9 1.5 Blank pH = 7.00 [Initial biomass] = 0.47 g/l 20 ml Take the samples at 0.5 0.1 0.3 0.7 0.9 1.5 Blank 2/3 from bottom of tube pH = 7.00 [Initial biomass] = 1.55 g/l 1/2 from bottom of tube Cell density Measurement using UV (Wavelength = 688 nm) 0.5 0.1 0.3 0.7 0.9 1.5 Blank 11 pH = 7.00 [Initial biomass] = 2.60 g/l

40. Specific flocculation rateSpecific flocculation rate was evaluated by taking the highest slope of the graph which correlates the flocculation efficiency and flocculation time. 12 MethodsFLOCCULATION PERFORMANCE PARAMETERS

41. 13 Experimental ResultsMICROALGAE GROWTH ON BASAL MEDIUM Growth condition increase

42. 14 Experimental ResultsFLOCCULATION USING PH ADJUSMENT (1) Percent flocculation efficiency using pH adjustment method at different final pH and different initial biomass concentration 75.71% 60.95% 47.63% [Initial biomass] = 0.67 g/l 30.10% [Initial biomass] = 1.27 g/l 4 4 At fixed initial biomass concentration, increasing in pH value resulted in increasing in flocculation efficiency

45. Specific flocculation rate of Chlorella vulgaris ESP-31 at different initial biomass and coagulant concentration 17 Experimental ResultsFLOCCULATION USING AlCl3 AS COAGULANT Increase! Increase! Data used in this experiment originated from the samples taken at two-thirds from the bottom of tube

46. 18 Experimental ResultsFLOCCULATION USING AlCl3 AS COAGULANT (2) Highest flocculation efficiency of Chlorella vulgaris ESP-31 at different initial biomass concentration and coagulant concentration Increase! Increase! The highest flocculation efficiency pertime was determined from flocculation efficiency at 4 h of settling time

49. Conclusion Oil-rich microalgae strain Chlorella vulgaris ESP-31 can be harvestedusing flocculation by pH adjustment and flocculation by coagulant addition Flocculation using AlCl3as coagulant showed much faster specific flocculation rate For a fixed initial biomass concentration, increase in dosage of AlCl3 tended to increase the flocculation efficiency Increasing in initial biomass concentration increase the dosage of AlCl3 needed to obtain more than 90% of flocculation efficiency 21

50. Thankyou for your attention !! 22