Anaerobic treatment of sewage sludge containing selective serotonin reuptake inhibitors

The selective serotonin reuptake inhibitors citalopram, sertraline, paroxetine, fluvoxamine and fluoxetine have been investigated in 10 l anaerobic lab-scale digesters with continuous stirring and mesophilic conditions at 37 °C to investigate whether they would be reduced or accumulated in sewage sludge depending on whether the bacteria present were able to use the SSRIs as a carbon source or not. The total SSRI concentration had a significant reduction in concentration during the anaerobic treatment process from theoretically 0.58 mg/l to 0.21 mg/l after 17 days. However, large differences in the reduction of the different compounds were found. Paroxetine and citalopram were found to be almost completely reduced at day 24 with reductions of 85% (citalopram) and 98% (paroxetine). Reductions of 32% (fluoxetine), 53% (fluvoxamine) and 38% (sertraline) indicate that these three compounds have a higher potential for accumulation. None metabolites of these compounds were found in the samples.

► No research has been done earlier on anaerobic degradation of SSRIs. ► Paroxetine and citalopram were found to be more or less completely reduced. ► Fluvoxamine, fluoxetine and sertraline were relatively stable from day 17 to 24. ► The results indicate that some SSRIs have a potential for accumulation under anaerobic treatment of sewage sludge.