Sewage sludge for sustainable agriculture: contaminants\u2019 contents and potential use as fertilizer

Lucrezia Lamastra,Marco Trevisan,Nicoleta Alina Suciu

doi:10.1186/s40538-018-0122-3

Lucrezia Lamastra, Marco Trevisan + Show 1 more

Open Access

https://doi.org/10.1186/s40538-018-0122-3

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Abstract

BackgroundSewage sludge, the inevitable byproduct of municipal wastewater-treatment plant operation, is a key issue in many countries due to its increasing volume and the impacts associated with its disposal. According to the report of European Commission published in 2010, 39% of sewage sludge produced in the European Union is recycled into agriculture. Management options require extensive waste characterization, since many of them may contain compounds, which could be harmful to the ecosystem, such as heavy metals, organic pollutants, etc. The present study aims to show the results of 2 years’ sampling of sewage sludge—based on 130 samples collected from 35 wastewater-treatment plants situated in the North of Italy—and to assess its suitability as soil fertilizer regarding contents of nonylphenol (NP), nonylphenolethoxylates (NPnEOs), and phthalates (DEHP).ResultsAn effective analytic method for organic pollutants detection in the sewage sludge has been developed, showing an excellent repeatability and recoveries. Ecotoxicological risk assessment was evaluated using risk quotients (RQs) for sludge-amended soil. Most of the analyzed samples do not contain NP, NPnEOs, and DEHP at levels higher than the limit established by the draft-working document of the European Commission on Sludge. The assessment using RQs reports that NP and NPnEOs never give values higher than 1, and for DEHP the obtained RQs exceed the value of 1 just three times. Data obtained were compared to the data from other European and Asiatic countries, showing a huge variability for all the compounds considered.ConclusionsBased on the obtained results, it appears that the proposed EU limits for the selected substances on sewage sludge intended to be used as soil fertilizer in agriculture are sufficiently conservative to avoid negative effects on soil fauna.

Highlights

Sewage sludge, the inevitable byproduct of municipal wastewater-treatment plant operation, is a key issue in many countries due to its increasing volume and the impacts associated with its disposal
The PECsoil were calculated as per the following the equation: PECsoil = Csludge ∗ APPLsludge /(DEHPT ∗ BDsoil), where Csludge is the measured concentration of selected compounds in dry sewage sludge, A PPLsludge is the drysludge application rate (0.5 kg m−2), DEPTHsoil is the average depth of soil (0.20 m), and BDsoil is the bulk density of wet soil (1700 kg m−3)
The concentrations of NP, NPnEOs, and DEHP in the sewage sludge, expressed as dry matter, are reported in Figs. 1, 2, and 3, respectively, and in Additional file 1: Table S1. 130 samples from 35 treatment plants in the North of Italy were analyzed during the 2-year study period (2013–2014)

Summary

Introduction

The inevitable byproduct of municipal wastewater-treatment plant operation, is a key issue in many countries due to its increasing volume and the impacts associated with its disposal. The present paper aims to show the Italian reality, regarding short-chain nonylphenols (NP and NPnEOs with n, indicating the number of ethoxy units, ranging from 1 to 2) and phthalates’ content in sewage sludge, and to evaluate their potential risk for soil organisms.

Results

Conclusion