Investigations into potential risks associated with the use of treated municipal sludge on agricultural land

Healy, M.G.1*, Fenton, O.2, Cummins, E.3, Clarke, R.,3 Peyton, D.P.1,2, Fleming, G.T.A.4, Wall, D.2, Morrison, L.5, and Cormican, M.6

1 Civil Engineering, National University of Ireland, Galway, Co. Galway, Ireland, 2Teagasc, Environment Research Centre, Johnstown Castle, Co. Wexford, Ireland, 3School of Biosystems and Food Engineering, Agriculture and Food Science Centre, University College Dublin, Belfield, Dublin 4, Ireland, 4Microbiology, National University of Ireland, Galway, Co. Galway, Ireland.

5Earth and Ocean Sciences and Ryan Institute, National University of Ireland, Galway, Co. Galway, Ireland, 6 School of Medicine, National University of Ireland, Galway, Co. Galway, Ireland.



Recycling to land is currently considered the most economical way for sewage sludge management. However, there is considerable concern over the presence of metals, nutrients, pathogens, pharmaceutical and personal care products (PPCPs), which may cause environmental and human health problems. The main aims of this research were to (1) quantify the range of concentrations of metals and the antimicrobials triclosan and triclocarban (two of the most abundant PPCPs in the world), in biosolids from a range of wastewater treatment plants in Ireland (2) undertake a field-scale experiment to assess losses of nutrients, metals,  triclosan and triclocarban, and microbial matter following successive rainfall events on grassland onto which biosolids had been applied (3) to measure the uptake of metals by ryegrass for a period of time after the application of biosolids (4) conduct a risk assessment of potential hazards of human health concern based on the experimental data.

Biosolids; land application; metals; public health; triclosan; triclocarban.


In 2010, more than 10 million tonnes of municipal sludge was produced in the European Union (EU) (Eurostat, 2014). The amount of sludge production has generally increased, which is reflective of changes in European legislation, such as the Urban Waste Water Treatment Directive (91/271/EC; Council of European Communities 1991) regarding the treatment of wastewater. Recently, legislation such as the Waste Framework Directive (2008/98/EC; Council of European Communities 1998) has imposed measures to reduce potential environmental impact arising from the generation and management of waste. A major driver for these changes has been the concept of a ‘circular economy’ (EC 2015), which fosters the concept that products, materials and services are maintained within the economy for as long as possible, in order to attain the notional goal of a ‘zero waste’ society (Grace et al. 2016). This has prompted those within the waste management community to consider municipal sewage sludge as a resource. Consequently, many uses have been found for it, such as the production of energy, construction materials and other potentially useful compounds (Healy et al. 2015). To date, municipal sewage sludge is most commonly disposed of by application to land, with some countries, such as Ireland, reusing up to 80% of it in agriculture (Eurostat, 2016).

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