Optimization of microalgae harvesting by sedimentation induced by high pH

Author(s)

Leite, Luan de Souza ^[1] ; Daniel, Luiz Antonio ^[1]

Affiliation

^[1] Univ Sao Paulo, Dept Hydraul & Sanitat, Sao Carlos Sch Engn, Av Trabalhador Sao Carlense 400, BR-1356659 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: WATER SCIENCE AND TECHNOLOGY; v. 82, n. 6, p. 1227-1236, SEP 15 2020.
• Web of Science Citations: 4

Abstract

Microalgae harvesting is a major hurdle for the production of high-value microalgal bioproducts on a large scale. Among harvesting techniques, pH-induced sedimentation stands out as an inexpensive and technically viable method. Nevertheless, there is little information available on the application of this method for microalgae cultivated in wastewater. In this context, the present study investigated the optimization of sedimentation parameters forChlorella sorokinianaharvesting from wastewater. Parameter optimization was statistically determined by the response surface methodology. The optimal values included a velocity gradient of 250 s(-1), mixing time of 10 seconds, and pH of 12, which enabled microalgae harvesting efficiencies of more than 97.8%. These optimal parameters also showed resilience through the physico-chemical variation of the photobioreactor effluent. Furthermore, wastewater quality improved significantly after microalgae harvesting. High removal was found for turbidity (97.9-98.3%), apparent color (92.2-97.2%), total Kjeldhal nitrogen (91.0-94.4%), and total phosphorus (92.8-98.6%). Centrifugation, as the dewatering method, and its operational parameters were also evaluated. Sedimentation followed by centrifugation increased the initial microalgae concentration by about 123 times. This study shows the importance of operational optimization and the results can be used as practical guidelines for microalgae harvesting on a large scale. (AU)

• FAPESP's process: 13/50351-4 - Recovering nutrients and carbon from concentrated black water: a sustainable decentralized approach for wastewater treatment
• Grantee: Luiz Antonio Daniel
• Support Opportunities: Regular Research Grants
• FAPESP's process: 17/14620-1 - Optimization of Chlorella sorokiniana cultivation in a flat panel photobioreactor and harvest for use as fertilizer
• Grantee: Luan de Souza Leite
• Support Opportunities: Scholarships in Brazil - Master