Valorization of selenium-enriched sludge and duckweed generated from wastewater as micronutrient biofertilizer

Selenium (Se) is an essential trace element for humans and animals with a narrow window between deficiency and toxicity levels. Application of conventional chemical Se fertilizers to increase the Se content of crops in Se deficient areas could result in environmental contamination due to the fast leaching of inorganic Se. Slow-release Se-enriched biofertilizers produced from wastewater treatment may therefore be beneficial. In this study, the potential of Se-enriched biomaterials (sludge and duckweed) as slow-release Se biofertilizers was evaluated through pot experiments with and without planted green beans (Phaseolus vulgaris). The Se concentration in the bean tissues was 1.1–3.1 times higher when soils were amended with Se-enriched sludge as compared to Se-enriched duckweed. The results proved that the Se released from Se-enriched biomaterials was efficiently transformed to health-beneficial selenoamino acids (e.g., Se-methionine, 76–89%) after being taken up by beans. The Se-enriched sludge, containing mainly elemental Se, is considered as the preferred slow-release Se biofertilizer and an effective Se source to produce Se-enriched crops for Se-deficient populations, as shown by the higher Se bioavailability and lower organic carbon content. This study could offer a theoretical reference to choose an environmental-friendly and sustainable alternative to conventional mineral Se fertilizers for biofortification, avoiding the problem of Se losses by leaching from chemical Se fertilizers while recovering resources from wastewater. This could contribute to the driver for a future circular economy.

This work has been financially supported by the Special Research Fund (BOF, BOFCHN2017000801) from Ghent University as well as the Chinese Scholarship Council (CSC, 201606300023). P.T. wishes to acknowledge the FWO for his personal funding (FWO, 12Q7718 N). The authors acknowledge Ana María Murillo Abril for her assistance with the lab work, as well as the DUBBLE staff, FWO and NWO for their support during synchrotron experiments at ESRF. Ivet Ferrer is grateful to the Government of Catalonia (Consolidated Research Group 2017 SGR 1029)

Peer Reviewed

Objectius de Desenvolupament Sostenible::6 - Aigua Neta i Sanejament

Objectius de Desenvolupament Sostenible::12 - Producció i Consum Responsables

Postprint (author's final draft)