Sains Malaysiana 50(1)(2021): 73-83

http://dx.doi.org/10.17576/jsm-2021-5001-08

Harvesting Marine Microalgae Nannochloropsis sp. using Dissolved Air Flotation (DAF) Technique

(Penuaian Mikroalga Marin Nannochloropsis sp. menggunakan Teknik Pengapungan Udara Terlarut (DAF))

NURAFIFAH FUAD, ROZITA OMAR*, SURYANI KAMARUDIN, RAZIF HARUN, A. IDRIS & W.A.K.G WAN AZLINA

Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia

Diserahkan: 22 Mac 2020/Diterima: 20 Jun 2020

ABSTRACT

The production of high-value bioproducts from microalgae biomass has been widely investigated. However, their production is hindered by the expensive harvesting process. To date, flocculation followed by DAF process has been accepted as one of the affordable harvesting approaches. In this study, the use of DAF technique was attempted to harvest marine microalgae Nannochloropsis sp. Batch DAF harvesting was carried out using fabricated DAF unit equipped with several compartments including separation column, product collecting vessel and rotary skimmer. Tannin-based biopolymer flocculant, AFlok-BP1 at pH 5 with a concentration of 160 mg/L was used to facilitate the flocculation of particles. The effects of different saturator pressure at 1.8, 2, and 2.2 bar were then evaluated at a constant volume of 6 L microalgae culture. The effects of different microalgae culture volumes (6, 8 and 10 L) were also evaluated at a fixed saturator pressure of 2.2 bar. The highest pressure at 2.2 bar yielded the best result with the highest total solid of 3.19 ± 0.01% and a maximum yield of 1.70 ± 0.05 g/g (wet basis). The microalgae concentration was the lowest (0.027 g/L) when 6 L of culture volume was used. However, the values were significantly higher when the culture volume was increased to 8 and 10 L to approximately 0.035 and 0.050 g/L, respectively. As a conclusion, the study provided evidence for the feasibility of DAF technique in harvesting marine microalgae Nannochloropsis sp.

Keywords: Bubbles; dewatering; flotation; microalgae; saturator

ABSTRAK

Penghasilan produk biologi yang bernilai tinggi daripada biojisim mikroalga telah dikaji dengan meluas. Namun begitu, penghasilan produk biologi ini terhalang oleh proses penuaian yang mahal. Sehingga hari ini, kaedah flokulasi diikuti dengan proses pengapungan udara terlarut (DAF) telah diterima baik sebagai satu kaedah penuaian yang berpatutan. Dalam kajian ini, kaedah DAF telah diguna pakai untuk menuai mikroalga marin Nannochloropsis sp. Penuaian DAF secara kelompok telah dijalankan menggunakan unit DAF yang telah difabrikasi dan dilengkapkan dengan beberapa bahagian termasuklah turus pemisah, vesel pengumpulan produk dan pemeres putar. Flokulan biopolimer berasaskan tanin, AFlok-BP1 telah digunakan pada nilai pH 5 dengan kepekatan 160 mg/L untuk memudahkan proses flokulasi zarah-zarah. Kesan tekanan penyerapan yang berbeza pada 1.8, 2.0 dan 2.2 bar kemudiannya dinilai pada isi padu tetap kultur mikroalga iaitu 6 L. Kesan isi padu mikroalga kultur yang berbeza (6, 8 dan 10 L) juga dinilai menggunakan tekanan penyerapan yang tetap iaitu 2.2 bar. Tekanan paling tinggi pada 2.2 bar memberikan keputusan terbaik dengan jumlah pepejal tertinggi, 3.19 ± 0.01% dan hasil maksimum, 1.70 ± 0.05 g/g (asas basah). Kepekatan mikroalga adalah paling rendah (0.027 g/L) apabila isi padu kultur 6 L digunakan. Walau bagaimanapun, nilai tersebut meningkat secara signifikan dengan penambahan isi padu kultur dari 8 dan 10 L dengan anggaran sebanyak 0.035 dan 0.050 g/L. Kesimpulannya, kajian ini telah membuktikan keupayaan teknik DAF untuk menuai mikroalga marin Nannochloropsis sp.

Kata kunci: Buih; mikroalga; penyahairan; pengapungan; penyerapan

RUJUKAN

Barros, A.I., Goncalves, A.L., Simoes, M. & Pires, J.C.M. 2015. Harvesting techniques applied to microalgae: A review. Renewable and Sustainable Energy Reviews 41: 1489-1500.

Besson, A. & Guiraud, P. 2013. High-pH-induced flocculation-flotation of the hypersaline microalga Dunaliella salina. Bioresource Technology 147: 464-470.

Dassey, A. & Theegala, C. 2012. Optimizing the air dissolution parameters in an unpacked dissolved air flotation system. Water 4: 1-11.

Edzwald, J.K. 2010. Dissolved air flotation and me. Water Research 44: 2077-2106.

Fuad, N., Omar, R., Kamarudin, S., Harun, R., Idris, A. & Wan Azlina, W.A.K.G. 2018. Effective use of tannin based natural biopolymer, AFlok-BP1 to harvest marine microalgae Nannochloropsis sp. Journal of Environmental Chemical Engineering 6: 4318-4328.

Gerardo, M.L., Van, D.H.S., Vervaeren, H., Coward, T. & Skill, S.C. 2015. Harvesting of microalgae within a biorefinery approach: A review of the developments and case studies from pilot-plants. Algal Research 11: 248-262.

Gulden, S.J., Riedele, C., Kopf, M.H. & Nirschl, H. 2020. Potential of flotation as alternative separation process in biotechnology with focus on cost and energy efficiency. Chemical Engineering Science 218(8): 115117.

Han, M., Kim, T. & Kim, J. 2007. Effects of floc and bubble size on the efficiency of the dissolved air flotation (DAF) process. Water Science and Technology 56: 109-115.

Harun, R., Singh, M., Forde, G.M. & Danquah, M.K. 2010. Bioprocess engineering of microalgae to produce a variety of consumer product. Renewable and Sustainable Energy Reviews 14: 1037-1047.

Henderson, R.K., Parsons, S.A. & Jefferson, B. 2008. Successful removal of algae through the control of zeta potential. Separation Science and Technology 43: 1653-1666.

Kim, T., Park, H. & Han, M. 2017. Development of algae removal method based on positively charged bubbles. KSCE Journal of Civil Engineering 7(21): 2567-2572.

Kim, M.S. & Kwak, D.H. 2020. Auto/bio-flocculation conditions to separate algal particles without chemical coagulants for flotation and sedimentation processes. Separation Science and Technology 55(6): 1185-1196.

Kwon, H., Lu, M., Lee, E.Y. & Lee, J. 2014. Harvesting of microalgae using flocculation combined with dissolved air flotation. Biotechnology and Bioprocess Engineering 19: 143-149.

Laamanen, C.A., Ross, G.M. & Scott, J.A. 2016. Flotation harvesting of microalgae. Renewable and Sustainable Energy Reviews 58: 75-86.

Leite, L.D.S., Santos, P.R.D. & Daniel, L.A. 2019. Microalgae harvesting from wastewater by pH modulation and flotation: Assessing and optimizing operational parameters. Journal of Environmental Management 254: 109825.

Liu, J., Song, Y. & Qiu, W. 2017. Oleaginous microalgae Nannochloropsis as a new model for biofuel production: Review & analysis. Renewable and Sustainable Energy Reviews 72: 154-162.

Lin, Z., Kuang, Y.L. & Leng, Y.W. 2011. Harvesting microalgae biomass by instant dissolved air flotation at batch scale. Advanced Materials Research 236-238: 146-150.

Ndikubwimana, T., Chang, J., Xiao, Z., Shao, W., Zeng, X., Ng, I.S. & Lu, Y. 2016. Flotation: A promising microalgae harvesting and dewatering technology for biofuels production. Biotechnology Journal 11: 315-326.

Niaghi, M., Mahdavi, M.A. & Gheshlaghi, R. 2015. Optimization of dissolved air flotation technique in harvesting microalgae from treated wastewater without flocculants addition. Journal of Renewable and Sustainable Energy 7: 1-20.

Omar, R., Idris, A., Harun, R., Kamarudin, S., Wan Azlina, W.A.K.G., Kamal, S.M., Biak, D.R.A. & Fuad, N. 2017. Comparison of lipid quality of Nannochloropsis sp. flocculated via autoflocculation, AFlok-BP1 and Alum. 5th International Symposium on Applied Engineering and Sciences (SAES2017), Universiti Putra Malaysia, Serdang, Selangor, 14^th -15^th November 2017.

Sharma, K.K., Garg, S., Li, Y., Malekizadeh, A. & Schenk, P.M. 2013. Critical analysis of current microalgae dewatering techniques. Biofuels 4: 397-407.

Wiley, P.E., Brenneman, K.J. & Jacobson, A.E. 2009. Improved algal harvesting using suspended air flotation. Water Environment Research 81: 702-708.

Zhang, X., Hewson, J.C., Amendola, P., Reynoso, M., Sommerfeld, M., Chen, Y. & Hu, Q. 2014. Critical evaluation and modeling of algal harvesting using dissolved air flotation. Biotechnology and Bioengineering 111: 2477-2485.

Zhang, W.H., Zhang, J., Zhao, B. & Zhu, P. 2015. Microbubble size distribution measurement in a DAF system. Industrial & Engineering Chemistry Research 54: 5179-5183.

Zhang, X., Wang, L., Sommerfeld, M. & Hu, Q. 2016. Harvesting microalgal biomass using magnesium coagulation-dissolved air flotation. Biomass and Bioenergy 93: 43-49.

Zhang, H., Lin, Z., Tan, D., Liu, C., Kuang, Y. & Li, Z. 2017. A novel method to harvest Chlorella sp. by co-flocculation/air flotation. Biotechnology Letters 39: 79-84.

*Pengarang untuk surat-menyurat; email: rozitaom@upm.edu.my