On the degradation of metformin and carbamazepine residues in sewage sludge compost
¹University of Technology, Tartu College, Puiestee 78, EE51008 Tartu, Estonia
²University of Tartu, Institute of Chemistry, Ravila 14A, EE51010 Tartu, Estonia
³Estonian University of Life Sciences, Kreutzwaldi 58A, EE51014 Tartu, Estonia
Recent decades have shown intensive studies devoted to the fate of pharmaceuticals in the environment. These studies have involved the development of analytical tools, determination of pharmaceuticals in different compartments, composting technologies, and plant uptake of pharmaceuticals. The presence of organic pollutants in sewage sludge, including pharmaceuticals, is a problem of major concern. The re-use of sewage sludge should be encouraged since it represents a long-term solution provided that the quality of the sludge re-used is compatible with public health and environmental protection requirements. Composting is a widely recognized way of making the soil application of sewage sludge safer.
In this study, the impact of sewage sludge composting on the degradation of metformin (MET), by far the most often prescribed antidiabetic drug worldwide, and carbamazepine (CBZ), a poorly biodegradable but widely used as an anticonvulsant drug to cure depression and seizures, were analysed. The anaerobically digested and dewatered sewage sludge samples were collected from municipal wastewater treatment plant. Composting experiments were performed under fixed conditions during 30 days. The results of the experiment showed that during a 1-month composting period more than 90% of MET residues degraded, but no degradation of CBZ took place during the composting period. The half-life of MET was 3 days for the compost mixture with the ratios of 1:3 and 1:2 (v:v). The results of this study show that composting maylead to the efficient degradation of MET, whereas for the elimination of CBZ from sewage sludge different means should be used.