Name: Sara Aparecida Francisco
Type: MSc dissertation
Publication date: 31/03/2016

Namesort descending Role
Sérvio Túlio Alves Cassini Advisor *

Examining board:

Namesort descending Role
Ann Honor Mounteer External Examiner *
Edumar Ramos Cabral Coelho Internal Examiner *
Sérvio Túlio Alves Cassini Advisor *

Summary: Harvesting is a critical step in microalgae biomass production process for many purposes. Among the existing techniques available for harvesting and dewatering microalgae biomass, recovery from aqueous medium by coagulation-flocculation has been the most economically viable process, although highly dependent on pH. This study aims to assess alternative coagulants for microalgae biomass recovery as compared with the standard coagulant aluminium sulphate from anaerobic effluent of domestic sewage treatment. The effluent quality was also analysed after biomass recovery. Coagulants represented by modified tannin, cationic starch and aluminium sulphate recovered more than 90% of algae biomass, at concentrations greater than 80 mg/L, in the pH range 7-10. Cationic starch promoted higher microalgae biomass recovery with the wider pH range. Seeds of Moringa Oleifera and Hibiscus esculentus (okra) gum promoted biomass removal of 50%, only in the acidic range of pH. The effluents after sedimentation of the microalgae biomass showed removal >80% for phosphorus and nitrogen and >50% for BOD and COD, using aluminium sulphate, cationic starch and modified tannin. MBM recovered from aluminum sulphate (AS-BMA) presented higher EC50 values, while MBM recovered from natural organic polymers resulted in EC50 values 50% lower then BMA-AS. Natural organic coagulants in a wide pH range can replace aluminium sulphate, which is a reference in microalgae biomass recovery, without decreasing microalgae biomass harvesting efficiency and the quality of the final effluent.

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