Research

Assessment of risks related to agricultural use of sewage sludge, pig and cattle slurry

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Abstract

In April 2017, the Organic Business Development Team released a report with 25 recommendations for the Minister of Environment and Food (Det økologiske erhvervsteam 2017). Among these was a recommendation that organic farmers should have opportunities for utilizing nutrients from treated domestic wastewater for nutrient recycling. A prerequisite for future use of nutrients from treated wastewater is, that quality requirements are met and that application can be explained to (and accepted by) consumers. In partial fulfilment of this, the business team identified a need for a scientific overview of the risks of using nutrients from treated municipal wastewater in relation to other authorized fertilizer sources – e.g. conventional animal manures. Thus, it was assumed that a comparative approach to assess potential risk of using sewage sludge and conventional manures, could usefully inform decision makers in the future regulation of organic farming systems. Dependent on the result of the scientific investigation, the Organic Business Development Team foresaw that Denmark could chose to work to expand Annex 1 of the EU Ecology Regulation, to allow the organic farmers to use nutrients from municipal wastewater or other acceptable derived sludge products. Mobilization of support for this should be done by the Ministry of Environment and Food in collaboration with the Organic Farming Industry. Thus, based on available literature, this report aims at creating an overview of the environmental and human risks associated with application of pig and cattle slurry as well as sewage sludge to agricultural soils. The risk evaluation was performed for the following compound groups: Metals, Chlorophenyls, Dioxins, Furans, Halogenated aliphatic and aromatic hydrocarbons (HAH), Linear alkylbenzenesulfonates (LAS), Polyaromatic hydrocarbons (PAH), Polybrominated diphenyl ethers (PBDE), Polychlorinated biphenyls (PCB), Poly- and perfluorinated alkylated substances (PFAS), Phenols, Phosphate-triesters VII, Phthalates, Polychlorinated naphtalenes (PCN), Polychlorinated alkanes (PCA), Triclosan, Triclocarban, Medicines, Estrogens, Antibiotic resistance genes. Additionally the fertilizer potential of the two nutrient sources was characterized and compared.