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

Abstract

Background: 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. 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). Results: An 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. Conclusions: Based 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.

Interaction of lead and cadmium on growth and leaf morphophysiological characteristics of European hackberry (Celtis australis) seedlings

“…Cadmium (Cd) and lead (Pb) are two major heavy metals with strong toxicity effects on all types of life including vegetations [7,18]. From environmental and biological point of view, Pb and Cd are more important than many other heavy metals [6,16]. Cadmium and lead as nonessential elements, can readily be taken up by plant roots and induce adverse effects on plant metabolism, growth, and development [3,8].…”

Effect of Municipal Sewage Sludge on Soil Chemical Properties and Chemical Composition of Spring Wheat

“…That is why, aside from fertilization with sewage sludge, supplementary mineral fertilization should be applied [26]. It was assumed that nitrogen use by spring wheat from this waste would be approximately 90 kg/ha, therefore in the treatment with sludge (2) mineral nitrogen fertilization was supplemented to the level used in the control treatment (1). Nitrogen was also applied in three doses: 20 kg/ha pre-sowing + 20 kg/ha at the beginning of stem elongation (BBCH 31) + 20 kg/ha at the beginning of heading (BBCH 51).…”

“…Municipal sewage sludge should be treated as a raw material with a certain fertilizer or energy value. Environmental use of this waste is an ecologically and economically justified method of processing it [1,2]. This waste is a potential source of organic matter, nutrients, which are used in land reclamation for agricultural purposes [3,4].…”

Integrated nutrient recovery from source-separated domestic wastewaters for application as fertilisers

“…Currently, over 90% of the urban population in Europe and Northern America has a sewer connection [9] and to protect not only human but also environmental health, STPs need to comply with stringent legislation for organic matter (OM) and nutrient removal. In the European Union, around 40% of the produced sewage sludge is used in agriculture [10,11]. Agricultural use of sewage sludge is often limited by legislation regarding e.g.…”