Energy and Cost Analysis of Chlorella vulgaris Harvesting by using Forward Osmosis and Ultrafiltration Membrane Processes
Defghi Arsy Muhammad1, Inggit Kresna Maharsih1, Wahyunanto Agung Nugroho1, Yusuf Wibisono1,2,*

1 Department of Bioprocess Engineering, Faculty of Agricultural Technology, Brawijaya University, Jl. Veteran Malang 65145 Indonesia-

2 MILI Institute for Water Research, Kawasan Industri Jababeka, Bekasi, Indonesia 17530

Email: y_wibisono[at]ub.ac.id

Abstract

Chlorella vulgaris is a microalga which rich of green pigment and widely used as a natural antioxidant. Harvesting of Chlorella vulgaris microalgae is normally employing chemicals by flocculation, yet require extensive chemicals. A more environmentally friendly approach was carried out by means of membrane technology, namely forward osmosis (FO) and ultrafiltration (UF) membrane processes. However, assessment of energy requirement and cost analysis of both processes is not previously conducted. The current study aims to determine the consumption of electrical energy and the cost of harvesting using these two methods. The flux test results in the FO membrane method produced the highest feed solution (FS) flux at a 5M concentration draw solution (DS) of 1735.3 LMH, then the highest DS flux was obtained at a DS concentration of 4.5M of 1930.4 LMH. The highest flux value in the UF membrane method was 4367.8 LMH. The highest RSF value was obtained at a DS concentration of 47386.7 GMH. The UF membrane method has the highest fouling of 0.32 grams. The highest fouling FO was 0.303 grams. For cell density tests, the highest biomass value in the FO membrane method was 10.8 mg/L. The biomass value of the UF membrane method was 9.13 mg L. The electrical energy consumption of the FO membrane method pump during harvesting was 136W. The UF membrane method requires 50.6W of electrical energy. The UF membrane method has a cheaper overall harvesting cost of 1.14 compared to the FO membrane method of 3.06 rupiah. Harvesting using the UF membrane method is more optimal in harvesting Chlorella vulgaris compared to the FO method in terms of higher flux values and the ability to compress biomass every minute and overall energy consumption cycle and lower cost.

Keywords: Chlorella vulgaris, forward osmosis, energy, harvesting, microalgae, ultrafiltration

Topic: Food biotechnology and bioprocess engineering