Review of experimental biodegradation data on pharmaceuticals and comparison with predictive BIOWIN models

Abstract

In this study the experimental data on the biodegradation of 16 pharmaceuticals in activated sludge were reviewed and also the theoretical biodegradation of these pharmaceuticals was calculated using BIOWIN models. The main aim was to show the similarities or discrepancies between the two. Experimental data were critically reviewed considering biodegradation rates, biodegradation mechanisms and biosorption of pharmaceuticals. For some pharmaceuticals, theoretical BIOWIN estimations and experimental findings deviated from each other. For example, if only BIOWIN estimations are considered, clarithromycin, azithromycin and ofloxacin would be defined as refractory. However, in experimental studies, they appeared to be not completely refractory. One of the reasons is that in most cases pharmaceuticals could be used as secondary substrates in the presence of sufficient bulk organic matter. In addition, all experimental studies indicate that at long Solids Retention Times (SRTs), nitrification activity becomes enhanced and the enzyme AMO leads to the cometabolic elimination of many pharmaceuticals. BIOWIN models prove to be very helpful for having an initial idea about biodegradability of pharmaceuticals. However, in order to estimate the biodegradability under real conditions, the models can be extended to include the different removal mechanisms reported in this study.