Improving understanding of veterinary medicine degradation and fate in manures and anaerobic digestion plants

The presence of veterinary medicines in the environment has been investigated since the late 1990's (Halling-Sorensen et al., 1998) although we still know very little about their environmental fate (Grant et al., 2012; Slana and Sollner Dollenc, 2013; Jechalke et al., 2014). This is important as the Veterinary Medicines Directorate necessitates that veterinary medicines are assessed for environmental risk and appropriate measures are put in place to mitigate against suspected negative environmental impacts. Moreover, the EU Water Framework Directive (WFD), requires that rivers are of good ecological status and this is unlikely to be achieved with our currently limited knowledge of emerging pollutants such as veterinary medicines. Veterinary medicines are often poorly metabolised by livestock (Sarmah et al., 2006), have the potential to persist in manure, soil and water and have been detected in waterbodies throughout the year at concentrations ranging from several hundred up to tens of micrograms per litre (e.g. Boxall et al., 2006; Lissemore et al., 2006). Based on the limited available data (Kolodziejska et al., 2013), it is therefore possible that impacts on ecology may be resulting and that we need improved understanding of options to reduce these.
The central hypothesis that the project will test is that with an improved understanding of veterinary medicine degradation pathways we can mitigate environmental impacts by adopting the use of particular management options. These may include manure storage, use of on-farm anearobic digestors, and avoidance of compounds with the longest half-lives. Specific work packages (WPs) will investigate the affect of manure type and variability on degradation rates (WP1), the influence of manure storage facilities including on-farm anaerobic digestion on veterinary medicine fate (WP2), and the effect of manure application methods (WP3). Potential study compounds have been selected based on high usage and relevance to the different scenarios in which veterinary medicines may be used. Oxytetracycline, sulphamethazine, ceftiofur and flubendazole are likely to be the specific compounds investigated. For WP1 batch degradation experiments will be used to provide currently unavailable persistence data for the study compounds in different manures; grouse and sheep droppings, cattle and poultry manures, and pig slurry. We aim here to develop more robust guidance and methodologies for manure degradation for use in environmental risk assessments. Laboratory leaching columns will then be used to investigate the release of the test substances from the manures and their leaching through soil. Additional plot studies will be used to assess how manure type affects losses of veterinary medicines in overland flow. The collaboration between Leeds and FSL ensures that sufficent experimental facilities are available to carry out this challenging range of experiments. Anaerobic degestion is increasing being used on farms to generate biogas and field studies will determine the impact on degradation at a farm already used by FSL (WP2). For WP3, plot scale investigations at the University of Leeds' farm will be undertaken on arable and pasture land using both surface and sub-surface (injection) applications of manure. All analyses of veterinary medicine concentrations in environmental samples will be undertaken at FSL using one of the largest state of the art Liquid Chromatography-Mass Spectrometry (LC-MS) facilities in the country.