No abstract

Pure cultures have been found to degrade pharmaceutical compounds. However, these cultures are rarely characterized kinetically at environmentally relevant concentrations. This study investigated the kinetics of sulfamethoxazole (SMX) degradation by Achromobacter denitrificans strain PR1 at a wide range of concentrations, from ng/L to mg/L, to assess the feasibility of using it for bioaugmentation purposes. Complete removal of SMX occurred for all concentrations tested, i.e., 150 mg/L, 500 µg/L, 20 µg/L, and 600 ng/L. The reaction rate coefficients (k) for the strain at the ng/L SMX range were: 63.4 ± 8.6, 570.1 ± 15.1 and 414.9 ± 124.2 L/g[Formula: see text]·day), for tests fed without a supplemental carbon source, with acetate, and with succinate, respectively. These results were significantly higher than the value reported for non-augmented activated sludge (0.41 L/(g [Formula: see text]·day) with hundreds of ng/L of SMX. The simultaneous consumption of an additional carbon source and SMX suggested that the energetic efficiency of the cells, boosted by the presence of biogenic substrates, was important in increasing the SMX degradation rate. The accumulation of 3-amino-5-methylisoxazole was observed as the only metabolite, which was found to be non-toxic. SMX inhibited the Vibrio fischeri luminescence after 5 min of contact, with EC values of about 53 mg/L. However, this study suggested that the strain PR1 still can degrade SMX up to 150 mg/L. The results of this work demonstrated that SMX degradation kinetics by A. denitrificans PR1 compares favorably with activated sludge and the strain is a potentially interesting organism for bioaugmentation for SMX removal from polluted waters.

This study aimed to evaluate treatment performance and membrane fouling of a lab-scale Sponge-MBR under the added Ciprofloxacin (CIP) dosages (20; 50; 100 and 200 μg L-1) treating hospital wastewater. The results showed that Sponge-MBR exhibited effective removal of COD (94-98%) during the operation period despite increment of CIP concentrations from 20 to 200 μg L-1. The applied CIP dosage of 200 μg L-1 caused an inhibition of microorganisms in sponges, i.e. significant reduction of the attached biomass and a decrease in the size of suspended flocs. Moreover, this led to deteriorating the denitrification rate to 3-12% compared to 35% at the other lower CIP dosages. Importantly, Sponge-MBR reinforced the stability of CIP removal at various added CIP dosages (permeate of below 13 μg L-1). Additionally, the fouling rate at CIP dosage of 200 μg L-1 was 30.6 times lower compared to the control condition (no added CIP dosage).