Combined system for wastewater treatment: ozonization and coagulation via tannin-based agent for harvesting microalgae by dissolved air flotation

• Published in: Environmental technology Vol. 43; no. 9; pp. 1370 - 1380
• Main Authors: Oliveira, Gislayne Alves, Machado, Ênio Leandro, Knoll, Rhauani Segatto, Dell'Osbel, Naira, Colares, Gustavo Stolzenberg, Rodrigues, Lúcia Ribeiro
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 16-04-2022; Taylor & Francis Ltd
• Subjects: Algae; Ammonia; Aquatic microorganisms; Biomass; Coagulants; Coagulation; Electrical resistivity; eutrophication; Flocculation; Flotation; integrated system; Microalgae; Microalgae harvesting; Ozone; Performance evaluation; Pollution monitoring; Recovery; Separation techniques; tannin-based coagulant; Tannins; Turbidity; Venturi tube; Waste Water; Wastewater treatment; Wastewater treatment plants; Water treatment; tannin-based coagulant; Venturi tube; Microalgae harvesting; eutrophication; integrated system; wastewater treatment
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2020.1830181

This study evaluated the performance of urban wastewater treatment in pilot-plant by an integrated system consisting of anaerobic reactor, microalgae cultivation, Venturi tube ozone recirculation, coagulation/flocculation with tannin-based agent natural coagulant, and dissolved air flotation (DAF). Ozone concentrations (without ozone, 0.13 and 0.25 mg O
3
/mg of biomass) and tannin dosages (65, 85 and 105 mg/L) were evaluated regarding microalgae separation and their influences on wastewater treatment performance. During the experiments, it was verified that the treatment efficiency increased when ozone was applied and with higher tannin dosages. The best results were found with 0.13 mg O
3
/mg of biomass and 105 mg/L of tannin, obtaining excellent removal of turbidity removal (99.4%), apparent colour at 420 nm (94.5%), TN (83.2%), N-NH
3
(100%), TOC (86.8%), BOD
5
(86.5%) and COD (100%), 47.6% reduction in electric conductivity, 46.1% in TDS, 66.4% TP removal for the integrated system and 84% microalgae biomass recovery were obtained. Our results showed that the system proved to be a viable alternative for the treatment of urban wastewater and the recovery of microalgae through the insertion of ozone via Venturi tube combined with tannin-based agent.