Process for nutrient recycling from intensive aquaculture through microalgae-bacteria consortium

Ángela Perales-Pérez; María D Macías-Sánchez; Jesús Ruiz; José A Perales; Carmen Garrido-Pérez

doi:10.1016/j.scitotenv.2023.165848

Process for nutrient recycling from intensive aquaculture through microalgae-bacteria consortium

Sci Total Environ. 2023 Nov 25:901:165848. doi: 10.1016/j.scitotenv.2023.165848. Epub 2023 Aug 1.

Authors

Ángela Perales-Pérez¹, María D Macías-Sánchez², Jesús Ruiz³, José A Perales⁴, Carmen Garrido-Pérez⁵

Affiliations

¹ Department of Environmental Technologies, Marine Research Institute, INMAR, Faculty of Marine and Environmental Sciences, University of Cadiz, Campus Universitario de Puerto Real, 11510 Cadiz, Spain. Electronic address: angela.perales@uca.es.
² Department of Chemical Engineering and Food Technology, Science Faculty, University of Cadiz, Campus Universitario de Puerto Real, 11510 Cadiz, Spain. Electronic address: dolores.macias@uca.es.
³ Department of Environmental Technologies, Marine Research Institute, INMAR, Faculty of Marine and Environmental Sciences, University of Cadiz, Campus Universitario de Puerto Real, 11510 Cadiz, Spain. Electronic address: jesus.ruizgonzalez@uca.es.
⁴ Department of Environmental Technologies, Marine Research Institute, INMAR, Faculty of Marine and Environmental Sciences, University of Cadiz, Campus Universitario de Puerto Real, 11510 Cadiz, Spain. Electronic address: joseantonio.perales@uca.es.
⁵ Department of Environmental Technologies, Marine Research Institute, INMAR, Faculty of Marine and Environmental Sciences, University of Cadiz, Campus Universitario de Puerto Real, 11510 Cadiz, Spain. Electronic address: carmen.garrido@uca.es.

PMID: 37536584
DOI: 10.1016/j.scitotenv.2023.165848

Abstract

This work studies a biological process based on a microalgae-bacteria consortium for recycling nutrients in a recirculating aquaculture system (RAS) implanted in an intensive marine aquaculture farm. Additionally, some techniques were used for microalgae biomass harvesting and tested the effectiveness of filtration by a column with multi-layer sand to reduce the solids concentrations in the effluent. The consortium was grown in photobioreactors in batch and semi-continuous operation modes using the solids concentrated stream generated in the RAS system. The semi-continuous operation showed a high percentage of TDN and TDP removal, achieving final concentrations of 1.09 ± 0.02 mg·L^-1 and 0.01 ± 0.01 mg·L^-1, respectively, while DOC was reduced to 3.87 ± 0.06 mg·L^-1. The values of productivity 44 ± 9 mg TSS·L^-1 indicated that the studied stream is a suitable culture medium for the growth of the microalgae-bacteria consortium. A combination of harvesting techniques was studied, coagulation-flocculation-settling and coagulation-flocculation-flotation. The first step was to optimise the dose of FeCl₃ through the coagulation-flocculation test to pre-concentrate the biomass generated, achieving an optimal dose of 0.106 mg Fe·mg TSS^-1. Then, two separation processes were applied to the stream and compared: settling and flotation. The maximum removal efficiency (90.2 ± 0.3 %) was obtained in the settling process, so the coagulation-flocculation-settling was select as the best combination of harvesting techniques. Finally, sand filtration was studied as an effluent refining process to improve solids reduction of the water obtained in the harvesting step resulting in an effluent with 17.18 ± 1.49 mg TSS·L^-1. The proposed sequence process is capable of recycling nutrients from an intensive marine aquaculture farm by using these resources via transformation into microalgae biomass and generating quality effluent.

Keywords: Harvesting; Intensive marine aquaculture; Microalgae - bacteria consortium; Nutrient removal; Sand filtration.