RESUMO
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 0.25â mg O3/mg of biomass) and tannin dosages (65, 85 and 105â 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 0.13â mg O3/mg of biomass and 105â mg/L of tannin, obtaining excellent removal of turbidity removal (99.4%), apparent colour at 420â nm (94.5%), TN (83.2%), N-NH3 (100%), TOC (86.8%), BOD5 (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.
Assuntos
Microalgas , Biomassa , Floculação , Taninos , Águas ResiduáriasRESUMO
The removal of nutrients by Scenedesmus sp. in a high-rate algal pond, and subsequent algal separation by coagulation-flocculation or flotation with ozone to recover biomolecules, were evaluated. Cultivation of Scenedesmus sp. in wastewater resulted in complete NH3-H removal, plus 93% total nitrogen and 61% orthophosphate removals. Ozone-flotation obtained better water quality results than coagulation-flocculation for most parameters (NH3-N, NTK, nitrate and nitrite) except orthophosphate. Ozone-flotation, also produced the highest recovery of lipids, carbohydrates and proteins which were 0.32⯱â¯0.03, 0.33⯱â¯0.025 and 0.58⯱â¯0.014â¯mg/mg of biomass, respectively. In contrast, there was a low lipid extraction of 0.21â¯mg of lipids/mg of biomass and 0.12-0.23â¯mg of protein/mg of biomass in the coagulation-flocculation process. In terms of biomolecule recovery and water quality, ozone showed better results than coagulation-flocculation.