Effects of sulfamethoxazole on aerobic sludge granulation process.

AIMS: Our purpose was to clarify the effect of sulfamethoxazole (SMX) on the start-up period, particle formation, and treatment efficiency of an aerobic granular sludge system. METHODS AND RESULTS: We compared an R1 granular sequencing batch reactor (GSBR) started with 5 µg L-1 SMX and an R2 GSBR started without SMX, as a control, to investigate the impact of a trace amount of SMX (5 µg L-1 ) on aerobic granular sludge (AGS) characteristics and the removal of conventional contaminants. AGS granulation in the R1 system was not inhibited by SMX, but the granule particle size was smaller than that in the R2 system. Both systems had good performance removing conventional pollutants. Extracellular polymeric substance secretion in the R1 system was lower than that in the R2 system. After stabilizing reactor operations, the SMX removal efficiency in the R1 system (~73.93%) was higher than that in the R2 system (~70.66%). The start-up modes also determined the differences in the microbial community structure of the AGS systems. CONCLUSIONS: SMX-activated AGS performed better than AGS without SMX. SIGNIFICANCE AND IMPACT OF STUDY: The study can help engineers determine start-up modes with varieties of antibiotics in AGS processes and provide references for the optimization of water treatment processes.

Efficiency of sulfamethoxazole removal from wastewater using aerobic granular sludge: influence of environmental factors.

The effects of adsorption, sulfamethoxazole (SMX) content, chemical oxygen demand (COD), and dissolved oxygen (DO) are recognized to be crucial for SMX removal in the aerobic granular sludge (AGS) system. Therefore, we investigated the impact of adsorption and these three different environmental factors on the SMX removal loading rate and removal efficiency of an AGS system, and determined the differences in microbial community composition under different environmental conditions. Adsorption was not the main SMX removal mechanism, as it only accounted for 5% of the total removal. The optimal SMX removal conditions were obtained for AGS when the COD, DO, and SMX concentrations were 600 mg/L, 8 mg/L, and 2,000 µg/L, respectively. The highest SMX removal efficiency was 93.53%. Variations in the three environmental factors promoted the diversity and changes of microbial communities in the AGS system. Flavobacterium, Thauera, and norank_f_Microscillaceae are key microorganisms in the AGS system. Thauera, and norank_f_Microscillaceae were sensitive to increases in SMX concentrations and beneficial for degrading high SMX concentrations. In particular, Flavobacterium abundances gradually decreased with increasing SMX concentrations.

Biosorption Mechanism of Aqueous Pb2+, Cd2+, and Ni2+ Ions on Extracellular Polymeric Substances (EPS).

Heavy metal pollution has been a focus with increasing attention, especially Pb2+, Cd2+, and Ni2+ in an aqueous environment. The adsorption capacity and mechanism of extracellular polymeric substances (EPS) from Agrobacterium tumefaciens F2 for three heavy metals were investigated in this study. The adsorption efficiency of 94.67%, 94.41%, and 77.95% were achieved for Pb2+, Cd2+, and Ni2+ adsorption on EPS, respectively. The experimental data of adsorption could be well fitted by Langmuir, Freundlich, Dubinin-Radushkevich isotherm models, and pseudo-second-order kinetic model. Model parameters analysis demonstrated the great adsorption efficiency of EPS, especially for Pb2+, and chemisorption was the rate-limiting step during the adsorption process. The functional groups of C=O of carboxyl and C-O-C from sugar derivatives in EPS played the major role in the adsorption process judged by FTIR. In addition, 3D-EEM spectra indicated that tyrosine also assisted EPS adsorption for three heavy metals. But EPS from strain F2 used the almost identical adsorption mechanism for three kinds of divalent ions of heavy metals, so the adsorption efficiency difference of Pb2+, Cd2+, and Ni2+ on EPS could be correlated to the inherent characteristics of each heavy metal. This study gave the evidence that EPS has a great application potential as a bioadsorbent in the treatment of heavy metals pollution.