Fate and removal of silver nanoparticles during sludge conditioning and their impact on soil health after simulated land application

Zainab Abdulsada; Richard Kibbee; Dina Schwertfeger; Juliska Princz; Maria DeRosa; Banu Örmeci

doi:10.1016/j.watres.2021.117757

Fate and removal of silver nanoparticles during sludge conditioning and their impact on soil health after simulated land application

Water Res. 2021 Nov 1:206:117757. doi: 10.1016/j.watres.2021.117757. Epub 2021 Oct 14.

Authors

Zainab Abdulsada¹, Richard Kibbee², Dina Schwertfeger³, Juliska Princz³, Maria DeRosa⁴, Banu Örmeci⁵

Affiliations

¹ Department of Civil and Environmental Engineering, Carleton University, 1125 Colonel by Drive, Ottawa, ON K1S 5B6, Canada; Department of Environmental Engineering, University of Baghdad, Karrada, Al-Jadriya, Baghdad, Iraq (present address).
² Department of Civil and Environmental Engineering, Carleton University, 1125 Colonel by Drive, Ottawa, ON K1S 5B6, Canada.
³ Environment and Climate Change Canada, 335 River Road, Ottawa, ON K1V 1C7, Canada.
⁴ Department of Chemistry, Carleton University, 1125 Colonel by Drive, Ottawa, ON K1S 5B6, Canada.
⁵ Department of Civil and Environmental Engineering, Carleton University, 1125 Colonel by Drive, Ottawa, ON K1S 5B6, Canada. Electronic address: banu.ormeci@carleton.ca.

PMID: 34715524
DOI: 10.1016/j.watres.2021.117757

Abstract

The growing use of silver nanoparticles (AgNPs) in personal care products and clothing has increased their concentrations in wastewater and subsequently in sludge raising concerns about their fate and toxicity during wastewater treatment and after land application of sludge. This research investigated the fate and removal of AgNPs during chemical conditioning of anaerobically digested sludge and their impact on soil bacteria and health after land application. Ferric chloride (FeCl₃), alum (Al₂ (SO₄)₃ • (14-18) H₂O), and synthetic (polyacrylamide) polymer were used for sludge conditioning. All conditioners effectively removed AgNPs from the liquid phase and concentrated them in sludge solids. Concentration analyses showed that out of 53.0 mg/L of silver in the sludge, only 0.1 to 0.003 mg/L of silver remained in the sludge supernatant after conditioning and 12 to 20% of this value were particulates. Morphological analyses also showed that AgNPs went through physical, chemical, and morphological changes in sludge that were not observed in nanopure water and the resulting floc structures and the incorporation of nanoparticles were different for each conditioner. The impact of conditioned AgNPs on the biological activities of soil was evaluated by investigating its impact on the presence of five important phyla (Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria). The results showed that AgNPs at a concentration of 20 mg AgNPs/g soil had a minimal impact on the presence and diversity of the assessed phyla. Also, using different chemicals for sludge conditioning resulted in different growth behavior of studied phyla. This study provides new insight into how the presence of AgNPs and different chemicals used for sludge conditioning might impact the soil biological activities and hence plant growth. The study also provides a solid basis for further research in the risk assessment of nanoparticle toxicity in biosolids amended soils.

Keywords: Conditioning; Inorganic conditioner; Land application; Polymer; Silver nanoparticles; Sludge.

MeSH terms

Metal Nanoparticles*
Sewage*
Silver / analysis
Soil
Wastewater

Substances

Sewage
Soil
Waste Water
Silver