Removal of pharmaceutical compounds commonly-found in wastewater through a hybrid biological and adsorption process.

Nowadays, alternative options to conventional wastewater treatment should be studied due to rising concerns emerged by the presence of pharmaceuticals compounds (PhCs) in the aquatic environment. In this work, a combined system including biological treatment by activated sludge plus adsorption with activated carbon is proposed to remove three selected drugs (acetaminophen (ACT), caffeine (CAF) and ibuprofen (IBU)) in a concentration of 2 mg L-1 of each one. For it three sequencing batch reactors (SBR) were operated. SBR-B treated a synthetic wastewater (SWW) without target drugs and SBR-PhC and SBR-PhC + AC operated with SWW doped with the three drugs, adding into SBR-PhC + AC 1.5 g L-1 of a mesoporous granular activated carbon. Results showed that the hybrid system SBR-activated carbon produced an effluent free of PhCs, which in addition had higher quality than that achieved in a conventional activated sludge treatment in terms of lower COD, turbidity and SMP concentrations. On the other hand, five possible routes of removal for target drugs during the biological treatment were studied. Hydrolysis, oxidation and volatilization pathways were negligible after 6 h of reaction time. Adsorption route only was significant for ACT, which was adsorbed completely after 5 h of reaction, while only 1.9% of CAF and 5.6% of IBU were adsorbed. IBU was the least biodegradable compound.

Changes in the process performance and microbial community by addition of the metabolic uncoupler 3,3',4',5-tetrachlorosalicylanilide in sequencing batch reactors.

A complete study about the effects of 3,3',4',5-tetrachlorosalicylanilide (TCS) on organic matter elimination performance, sludge production and on the microbial community of a biological wastewater treatment process has been performed. For this purpose two sequencing batch reactors (SBR) worked in parallel for 43 days with 0.8 mg·L-1 of TCS (SBR-1) and without this metabolic uncoupler (SBR-2). Results indicated that 63.3% of sludge reduction was achieved in SBR-1. However, COD removal efficiency was maintained in similar values in both reactors (89.1% and 92.1% in SBR-1 and SBR-2, respectively). The exhaustive mixed liquor characterization led to know deeply the action mechanism of TCS. In this way, a 69% of adenosine triphosphate (ATP) reduction was observed in SBR-1 in comparison with values measured in SBR-2. On the contrary, an increase in soluble microbial products (SMP) and DNA concentrations occurred as a consequence of TCS addition. Thus, it could be concluded that sludge reduction due to TCS addition was due to both uncoupling effect and cellular lysis. Also, increase in all microbial hydrolytic enzymatic activities measured was observed, which explained the stable performance achieved in SBR-1 despite to the results explained above. It should be highlighted that this uncoupler should not be used in biological treatments that require nitrogen elimination because nitrifying bacteria were affected by its addition (Nitrosomonas and Nitrospira). Finally, the 16S rRNA gene amplicon sequencing informed that an important reduction of bacterial diversity resulted in SBR-1 due to TCS addition.