Nanoparticles within WWTP sludges have minimal impact on leachate quality and soil microbial community structure and function

Mark Durenkamp,Mark Pawlett,Karl Ritz,Jim A Harris,Andrew L Neal,Steve P Mcgrath

doi:10.1016/j.envpol.2015.12.063

Abstract

One of the main pathways by which engineered nanoparticles (ENPs) enter the environment is through land application of waste water treatment plant (WWTP) sewage sludges. WWTP sludges, enriched with Ag and ZnO ENPs or their corresponding soluble metal salts during anaerobic digestion and subsequently mixed with soil (targeting a final concentration of 1400 and 140 mg/kg for Zn and Ag, respectively), were subjected to 6 months of ageing and leaching in lysimeter columns outdoors. Amounts of Zn and Ag leached were very low, accounting for <0.3% and <1.4% of the total Zn and Ag, respectively. No differences in total leaching rates were observed between treatments of Zn or Ag originally input to WWTP as ENP or salt forms. Phospholipid fatty acid profiling indicated a reduction in the fungal component of the soil microbial community upon metal exposure. However, overall, the leachate composition and response of the soil microbial community following addition of sewage sludge enriched either with ENPs or metal salts was very similar.

Highlights

One of the main pathways for consumer product-derived engineered nanoparticles (ENPs) in the environment is via sewage systems entering waste water treatment plants (WWTPs) (Batley et al, 2013), where ENPs tend to accumulate in sludge solids, rather than the watery effluent of WWTPs (Wang et al, 2012)
We showed that soil microbial community structure may be affected by addition of sewage sludge enriched either with ENPs or metal salts, with fungal communities being reduced compared to bacterial communities
A realistic approach was taken to study leaching of Zn and Ag ENPs and their metal salts, by adding these to the influent of a waste water treatment plant and mixing the resulting fully processed sewage sludges with soil

Summary

Introduction

One of the main pathways for consumer product-derived engineered nanoparticles (ENPs) in the environment is via sewage systems entering waste water treatment plants (WWTPs) (Batley et al, 2013), where ENPs tend to accumulate in sludge solids, rather than the watery effluent of WWTPs (Wang et al, 2012). In the EU and US, the majority of these sludges are applied to agricultural soils (Gottschalk et al, 2009), thereby forming the primary pathway for ENPs to enter the human food chain. The agricultural use of WWTP sludges can have variable effects on greenhouse gas (GHG) emissions. ENPs and/or associated metal ions may have detrimental effects on soil bacteria, thereby influencing GHG emissions. 20%) of GHG emissions (Lemke et al, 2007) and any changes in these emissions due to ENP exposure would influence their environmental impact Agriculture is one of the main contributors (approx. 20%) of GHG emissions (Lemke et al, 2007) and any changes in these emissions due to ENP exposure would influence their environmental impact

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