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

Received: 22 March 2020/Accepted: 20 June 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

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*Corresponding author; email: rozitaom@upm.edu.my