Biomass recovery from algal ponds by dissolved air flotation (DAF)

D.M. Torres1*, A.C. Brito2, R.Oliveira3, A.L.C. Araújo2,4 and M.A. Camargo-Valero5,6

1 Department of Natural Resources, Federal Institute for Education, Science and Technology of Paraiba. Guarabira-PB, Brazil. 2 Post-Graduation Program of Sanitary Engineering, Federal University of Rio Grande do Norte. Natal-RN, Brazil. 3 Department of Civil Engineering, Paraiba State University. Campina Grande-PB, Brazil. 4 Department of Natural Resources, Federal Institute for Education, Science and Technology of Rio Grande do Norte. Natal-RN, Brazil. 5 School of Civil Engineering, University of Leeds, Leeds LS2 9JT, UK. 6 Departamento de Ingeniería Química, Universidad Nacional de Colombia, Sede Manizales


This work evaluated the performance of a DAF system for biomass recovery from the effluent of algal ponds used for sewage treatment in Northeast Brazil. Two different coagulants and effluent samples were tested following a random-factor experimental design (34-1 – 4 factors and 3 levels), in triplicate. Factor analysis showed that coagulant dose was the most important factor, independently of the type of coagulant and sample characteristics. For poly aluminium chloride it is possible to work with the original sample pH at the lower recirculation rate (10%) and flocculation time (10 minutes), being able to recovery an algal mass of around 1200 kg/day and 550 kg/day (dry basis) from the primary facultative and maturation pond, respectively. As for ferric chloride, the DAF was more efficient, however it is necessary a pH correction to the value of 5.0, so this can generate a dry basis mass of solids around 1150 kg/day for the facultative pond and 830 kg/day for the maturation pond. Removals of suspended solids, turbidity, and chlorophyll-a were above 60%, reaching at optimal conditions removals up to 90%.

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