Active heterotrophic biomass and sludge retention time (SRT) as determining factors for biodegradation kinetics of pharmaceuticals in activated sludge

Abstract

a b s t r a c tThe present study investigates the biodegradation of pharmaceutically active compounds (PhACs) by active biomass in activated sludge. Active heterotrophs (X bh ) which are known to govern COD removal are suggested as a determining factor for biological PhAC removal as well. Biodegradation kinetics of five polar PhACs were determined in activated sludge of two wastewater treatment plants which differed in size, layout and sludge retention time (SRT).Results showed that active fractions of the total suspended solids (TSS) differed significantly between the two sludges, indicating that TSS does not reveal information about heterotrophic activity. Furthermore, PhAC removal was significantly faster in the presence of high numbers of heterotrophs and a low SRT. Pseudo first-order kinetics were modified to include X bh and used to describe decreasing PhAC elimination with increasing SRT.

Influence of nitrifying conditions on the biodegradation and sorption of emerging micropollutants

“…This is not the first time showing this correlation, since other authors observed a similar behavior in lab scale reactors or activated sludge units in STPs (Clara et al, 2005;Lishman et al, 2006), but the disparity on the reported removal efficiencies for this compound no matter if aerobic, anoxic or anaerobic conditions are present (Carballa et al, 2007b;Ternes et al, 2007;Suarez et al, 2010) makes difficult to outline clear conclusions. On the contrary, although no clear correlation was found, biodegradation rates and kinetic constants of most compounds decreased at higher SRTs, as previously observed by Majewsky et al (2011).…”

Biodegradation of sulfamethoxazole: current knowledge and perspectives

“…In order to avoid biased estimates and negative elimination efficiencies, the use of a sampling strategy that takes into consideration the hydraulic residence time distribution of WWTPs has been proposed (Majewsky et al 2011a). While the differences in the microbial communities of AS systems can lead to variable SMX removals, the active fraction of AS has also been shown to impact the biodegradation of SMX in full-scale systems and should be considered in future studies (Majewsky et al 2011b). The first batch test used samples of river sediment (3 g dry weight) and river water (60 mL) spiked with 20 μg/L SMX and resulted in 10 % SMX degradation after 30 days (~25 h half-life); this increased to 22 % removal in the presence of methanol, which served as an added carbon source (~10 h half-life) (Radke et al 2009).…”

Determination of Caffeine and Its Metabolites in Wastewater Treatment Plants Using Solid-Phase Extraction and Liquid Chromatography–Tandem Mass Spectrometry

“…[5][6][7] Furthermore, caffeine generates demethylated products because of biodegradation by human metabolism and microbial biodegradation. 8,9 Biodegradation has so far been the main process involved in the removal of caffeine during activated sludge treatment, 10 and demethylation is expected to be the main pathway. Firstly, theophylline, paraxanthine and theobromine are formed by oxidative demethylation of caffeine.…”