Assessment of the performance of an anoxic-aerobic microalgal-bacterial system treating digestate

Andrés F Torres-Franco; Maribel Zuluaga; Diana Hernández-Roldán; Deborah Leroy-Freitas; Cristian A Sepúlveda-Muñoz; Saúl Blanco; César R Mota; Raúl Muñoz

doi:10.1016/j.chemosphere.2020.129437

Assessment of the performance of an anoxic-aerobic microalgal-bacterial system treating digestate

Chemosphere. 2021 May:270:129437. doi: 10.1016/j.chemosphere.2020.129437. Epub 2020 Dec 29.

Authors

Andrés F Torres-Franco¹, Maribel Zuluaga², Diana Hernández-Roldán², Deborah Leroy-Freitas¹, Cristian A Sepúlveda-Muñoz³, Saúl Blanco⁴, César R Mota⁵, Raúl Muñoz⁶

Affiliations

¹ Department of Chemical Engineering and Environmental Technology, Valladolid University, Dr. Mergelina, s/n., 47011, Valladolid, Spain; Institute of Sustainable Processes, Dr. Mergelina, s/n, 47011, Valladolid, Spain; Department of Sanitary and Environmental Engineering, Federal University of Minas Gerais, Belo Horizonte, 31270-010, Brazil.
² Department of Chemical Engineering and Environmental Technology, Valladolid University, Dr. Mergelina, s/n., 47011, Valladolid, Spain; Institute of Sustainable Processes, Dr. Mergelina, s/n, 47011, Valladolid, Spain; Faculty of Environmental Engineering UPAEP University, Puebla, 21 Sur 1103, Barrio de Santiago, 72410, Puebla, Mexico.
³ Department of Chemical Engineering and Environmental Technology, Valladolid University, Dr. Mergelina, s/n., 47011, Valladolid, Spain; Institute of Sustainable Processes, Dr. Mergelina, s/n, 47011, Valladolid, Spain.
⁴ University of León, Campus de Vegazana, 24071, León, Spain; Laboratory of Diatomology, Institute of Environment, Natural Resources and Biodiversity, La Serna 58, 24007, León, Spain.
⁵ Department of Sanitary and Environmental Engineering, Federal University of Minas Gerais, Belo Horizonte, 31270-010, Brazil.
⁶ Department of Chemical Engineering and Environmental Technology, Valladolid University, Dr. Mergelina, s/n., 47011, Valladolid, Spain; Institute of Sustainable Processes, Dr. Mergelina, s/n, 47011, Valladolid, Spain. Electronic address: mutora@iq.uva.es.

PMID: 33429236
DOI: 10.1016/j.chemosphere.2020.129437

Abstract

The performance of an anoxic-aerobic microalgal-bacterial system treating synthetic food waste digestate at 10 days of hydraulic retention time via nitrification-denitrification under increasing digestate concentrations of 25%, 50%, and 100% (v/v) was assessed during Stages I, II and III, respectively. The system supported adequate treatment without external CO₂ supplementation since sufficient inorganic carbon in the digestate was available for autotrophic growth. High steady-state Total Organic Carbon (TOC) and Total Nitrogen (TN) removal efficiencies of 85-96% and 73-84% were achieved in Stages I and II. Similarly, PO₄^3--P removals of 81 ± 15% and 58 ± 4% were recorded during these stages. During Stage III, the average influent concentrations of 815 ± 35 mg TOC·L^-1, 610 ± 23 mg TN·L^-1, and 46 ± 11 mg PO₄^3--P·L^-1 induced O₂ limiting conditions, resulting in TOC, TN and PO₄^3--P removals of 85 ± 3%, 73 ± 3%, and 28 ± 16%, respectively. Digestate concentrations of 25% and 50% favored nitrification-denitrification mechanisms, whereas the treatment of undiluted digestate resulted in higher ammonia volatilization and hampered nitrification-denitrification. In Stages I and II, the microalgal community was dominated by Chlorella vulgaris and Cryptomonas sp., whereas Pseudoanabaena sp. was more abundant during Stage III. Illumina sequencing revealed the presence of carbon and nitrogen transforming bacteria, with dominances of the genera Gemmata, Azospirillum, and Psychrobacter during Stage I, II, and III, respectively. Finally, the high settleability of the biomass (98% of suspended solids removal in the settler) and average C (42%), N (7%), P (0.2%), and S (0.4%) contents recovered in the biomass confirmed its potential for agricultural applications, contributing to a closed-cycle management of food waste.

Keywords: Digestate; Microalgae; Microalgal-bacterial symbiosis; Nitrification-denitrification; Photobioreactor.

MeSH terms

Bioreactors
Chlorella vulgaris*
Denitrification
Food
Microalgae*
Nitrification
Nitrogen
Refuse Disposal*
Waste Disposal, Fluid
Wastewater

Substances

Waste Water
Nitrogen