Screening of Flocculating Agents for Harvesting of Mixed Microalgae Cultivated in Domestic Wastewater

Sohana Shabnam, Hishamuddin Omar, Shahrizim Zulkifly, Ahmad Ismail

Abstract


One of the recent focuses of microalgal research is sustainable biomass production for biofuel and low-cost resource recovery of mixed microalgae cultivation in wastewater. However, dealing with their small size and low concentration in the culture media is the foremost challenge for efficient harvesting of mass production. In this study, the efficiency of four different flocculating agents for harvesting mixed microalgae cultivated outdoor in domestic wastewater was investigated. The tested flocculants were metal salts (ferric chloride and alum), lime (calcium hydroxide), and organic polymer (Aflok®). The effects of culture-medium pH, flocculants concentration, biomass concentration, temperature, and sedimentation time on flocculation efficiency of harvesting mixed microalgae from domestic wastewater system were evaluated. The experimental results showed that the flocculants needed to obtain the high flocculation efficiency largely influenced by the condition of media as well as microalgae biomass concentration. In optimum condition, high flocculation efficiency (95- 100%) can be obtained from both FeCl3 (0.04-0.08 g/L) and Aflok® (0.084-0.112 g/L) in 60-90 min. However, compared to inorganic flocculant FeCl3, organic biopolymer Aflok® exhibited better harvesting efficiency over a range of pH (6-8) and temperature (25-35°C) within 60 min of sedimentation time when microalgae biomass concentration was below 0.6 g/L. Furthermore, Aflok® was found significantly more efficient (P < 0.001) than FeCl3 to produce >95% biomass flocculation for outdoor mass harvesting. This study demonstrates that Aflok® would be appropriate for sustainable microalgae biomass recovery from wastewater.

Aus. & NewZe J. Soci Busi. Env. Sus. Vol 5(1), April 2019, P 32-45


Keywords


Flocculant, Flocculation efficiency, Mixed microalgae, Microalgae culture, Biomass harvesting, Wastewater

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