Degradation of diclofenac and triclosan residues in sewage sludge compost
¹ Tartu College, Tallinn University of Technology, Puiestee 78, EE51008 Tartu, Estonia
² Estonian University of Life Sciences, Kreutzwaldi 58A, EE51014 Tartu, Estonia
³ Institute of Chemistry, University of Tartu, Ravila 14A, EE51010 Tartu, Estonia
Land application of sewage sludge compost is an important and efficient tool in the remediation of industrial landscapes and agricultural soils in Estonia. A number of studies have shown that, as a rule, pharmaceuticals and personal care products (PPCPs) are neither completely removed by sewage treatment, nor completely degraded in the environment. In this study, degradation rates of diclofenac sodium (DFC) and triclosan (TCS) were determined during sewage sludge composting. Anaerobically digested and dewatered sewage sludge was mixed with sawdust at two different ratios (1:2 and 1:3 sludge/sawdust, v:v). Then aerobic composting was carried out. These ratios were chosen on the basis of previous studies on sewage sludge composting with different bulking agents. The initial concentration of DFC and TCS was 2 mg kg-1 in relation to dry weight (dw). Low quantities of the studied pharmaceuticals were present in sewage sludge that was used for preparing the compost mixtures used in our experiments. The background concentrations of DFC and TCS were never equal to zero. The results showed that the difference between sewage sludge and bulking agent ratios (1:2 vs 1:3) in compost samples did not significantly affect temperature profiles during the experiment. The degradation of pharmaceuticals was more complete in the compost samples where the ratio of bulking agent was higher (1:3 by volume). The average degradation level (in all compost mixtures) was 95% for DFC and 68% for TCS. Pharmaceuticals entering into the soil may affect microbial activity, plant growth and development, and may have adverse effects on living organisms.