Pharmaceuticals are ubiquitous in aquatic systems affected by waste water treatment plants (WWTPs), where they can undergo further degradation. This process is determined not only by the compound’s physicochemical properties, but also environmental factors. For instance, the attenuation rate of acetaminophen differed by a factor of 40 between rivers Gründlach (Germany) and Fyris (Sweden). Although data is limited, previous studies indicate that biodiversity may be linked to the potential for degradation of micropollutans. However, the recommended biodegradation tests (i.e. OECD TG308) include no information on the microbial community. We designed an experiment based on OECD TG308 to assess the influence of bacterial diversity on pharmaceutical degradation.
Water and sediment were collected from rivers Fyris and Gründlach, before and after the discharge of the local WWTP. These rivers have divergent hydraulic boundary conditions, wastewater proportions and hence anticipated differences in biodiversity. The four sediments were acclimated with synthetic river water for 10 days, then spiked with a mixture of 11 pharmaceuticals at two concentration levels (200 µg/L and 2 mg/L) to test the response of the microbial community in the sediment. The selected compounds represent a wide range of biodegradation rates: acetaminophen, acesulfame K, caffeine, carbamazepine, diclofenac, furosemide, ibuprofen, metformin, oxazepam, tramadol and venlafaxine. During the 40-day incubation, the bottles were kept in the dark at 16°C and aerated daily to maintain an aerobic water column with an oxygen gradient in the sediment. The water phase was sampled at 10 time points while sediment samples were taken after acclimation and at the end of the test. We will measure the pharmaceutical concentrations in all samples, and use Illumina sequencing of bacterial 16S rRNA to analyze the active bacterial community composition. Rényi’s entropy profiles will be calculated to test whether differences in richness, eveness and community composition can be associated with the degradation potential.
Our results will show whether microbial communities up- and downstream of a WWTP differ in their potential to degrade pharmaceuticals and whether differences in the composition and diversity can explain the variation in the degradation rates of micropollutants between sample sites and rivers.