Outdoor pilot-scale raceway as a microalgae-bacteria sidestream treatment in a WWTP.

This study aims at demonstrating the feasibility of using microalgae-bacteria consortia for the treatment of the sidestream flow of the supernatant from blackwater dewatering (centrate) in an urban wastewater treatment plant in Northern Italy. A 1200 L raceway reactor was used for the outdoor cultivation of a diverse community of Chlorella spp., Scenedesmus spp. and Chlamydomonas spp. in continuous operation mode with 10 days hydraulic retention time. During the trial, an average daily areal productivity of 5.5 ± 7.4 g TSS m ^-2  day ^-1 was achieved while average nutrient removal efficiencies were 86% ± 7% and 71% ± 10% for NH ₄ -N and PO ₄ -P, respectively. The microalgal nitrogen assimilation accounted for 10% of the nitrogen in the centrate while 34% was oxidized to nitrite and nitrate. The oxygen produced by microalgae fully covert the oxygen demand for nitrification. This suggests that the proposed process would reduce the aeration demand for nitrification in the water line of the plant, while producing algal biomass to be further valorized for energy or material recovery.
Competing Interests: Declaration of competing interest The following authors have affiliations with organizations with direct or indirect financial interest in the subject matter discussed in the manuscript: Marco Mantovani: Università degli Studi di Milano – Bicocca (Italy); Francesca Marazzi: Università degli Studi di Milano – Bicocca (Italy); Riccardo Fornaroli: Università degli Studi di Milano – Bicocca (Italy); Micol Bellucci: Politecnico di Milano (Italy); Elena Ficara: Politecnico di Milano (Italy); Valeria Mezzanotte: Università degli Studi di Milano – Bicocca (Italy).
(Copyright © 2019 Elsevier B.V. All rights reserved.)