Removal Rates Of Sulfamethoxazole Research Articles

Hydroxyl radical dominated degradation of aquatic sulfamethoxazole by Fe0/bisulfite/O2: Kinetics, mechanisms, and pathways

In this study, batch experiments were carried out to investigate the key factors on sulfamethoxazole (SMX) removal kinetics in a new AOPs based on the combination of zero valent iron (Fe0) and bisulfite (S(IV)). With the increase of Fe0 from 0.25 mM to 5 mM, the removal rate of SMX was linearly increased in the Fe0/S(IV)/O2 system by accelerating the activation of S(IV) and Fe0 corrosion to accelerate. In the first 10 min of reaction, the increasing concentration of S(IV) inhibited SMX removal after since the high S(IV) concentration quenched reactive oxidative species (ROS). Then SMX removal rate was accelerated with the increase of S(IV) concentration after S(IV) were consumed up. The optimal ratio of S(IV) concentrations to Fe0 concentration for SMX removal in the Fe0/S(IV)/O2 system was 1:1. With SMX concentrations increasing from 1 to 50 μM, SMX removal rate was inhibited for the limitation of ROS yields. Although the presence of SO4− and OH was confirmed by electron paramagnetic resonance (EPR) spectrum, OH was identified as the dominant ROS in the Fe0/S(IV)/O2 system by chemical quenching experiments. Besides, strong inhibitive effects of 1,10-phenanthroline on SMX degradation kinetics by Fe0/S(IV)/O2 proved that the generation of ROS was rely on the release of Fe(II) and Fe(III). The generation of SO4− was ascribed to the activation of S(IV) by Fe(II)/Fe(III) recycling and the activation of HSO5− by Fe(II). And OH was simultaneously transformed from SO4− and generated by Fe0/O2. Density functional theory (DFT) calculation was conducted to reveal special reactive sites on SMX for radicals attacking and predicted intermediates. Finally, four possible SMX degradation pathways were accordingly proposed in the Fe0/S(IV)/O2 system based on experimental methods and DFT calculation.

Removal of antibiotic sulfamethoxazole by anoxic/anaerobic/oxic granular and suspended activated sludge processes

This study investigates the removal of the antibiotic sulfamethoxazole (SMX) in two sets of anoxic/anaerobic/oxic sequencing batch reactors inoculated with either suspended or granular activated sludge. Continuously, for three months, 2 μg/L SMX was spiked into the reactor feeds in a synthetic municipal wastewater with COD, total nitrogen (TN) and total phosphorous (TP) of 400, 43 and 7 mg/L, respectively. The presence of SMX had no significant impact on treatment performance of the suspended and granular biomass. After 12 h of hydraulic retention time, SMX removal efficiencies of 84 and 73% were obtained for the granular and suspended biomass, respectively. Mixing without aeration did not remove SMX, confirming the insignificance of SMX removal via sorption. The pseudo-first order SMX removal rate constants in the granular and suspended biomass were 2.25 ± 0.30 and 1.34 ± 0.39 L/gVSS·d, respectively. The results suggest that granules with advantages such as elevated biomass retention and greater biomass concentration could be effective for the removal of this class of antibiotics.

Degradation of sulfamethoxazole by a heterogeneous Fenton-like system with microscale zero-valent iron: Kinetics, effect factors, and pathways

Abstract Five commercial microscale zero-valent iron (mZVI) samples showed different reactivity in sulfamethoxazole (SMX) removal in the presence of H2O2, which was independent of respective iron surface area but was consistent with the dissolved iron releasing rate. Of five mZVI samples, mZVIYF2 possessed the highest reactivity in H2O2 and the mZVIYF2/H2O2 system could remove 97.9% SMX at room temperature within 10 min. The degradation curve of SMX by mZVI/H2O2 at pHini 3.0 could be divided into three phases: a lag phase, a rapid degradation phase, and a final stationary phase. Effects of pHini, mZVI loading, SMX concentration, and H2O2 concentration on SMX degradation by mZVI/H2O2 were analyzed. Removal rates of SMX by mZVI/H2O2 dropped sharply upon increasing pHini. Increasing dosages of Fe0 ranged from 25 to 75 mg/L and H2O2 at low concentrations (below 0.5 mM) both enhanced SMX degradation, but a higher concentration of Fe0 and H2O2 also quickly decreased oxidative efficiency of SMX. Increasing dosages of SMX within the range of 5–100 µM progressively decreased the oxidation rates of SMX by mZVI/H2O2. Furthermore, three degradation pathways of SMX by mZVI/H2O2 process were proposed based on the combination of theoretical calculations and intermediates identification.

Degradation of sulfamethoxazole in bioelectrochemical system with power supplied by constructed wetland-coupled microbial fuel cells

The removal rate and degradation pathway of Sulfamethoxazole (SMX) in bioelectrochemical system (BES) and the elimination dynamics of SMX in a BES driven by stacked constructed wetland-coupled microbial fuel cells (CW-MFCs) were investigated. The results found that SMX (30mgL−1) was rapidly degraded in the BES, and the SMX removal kinetics was simulated well by a first-order kinetic model (R2>0.93). Low current had no effect on the degradation products but enhanced the SMX removal rate. Biotransformation was the main pathway for the SMX elimination in the BES. The CW-MFCs supplied adequate and stable electricity (0.84–1.01V) to support the BES for rapid SMX degradation without additional energy inputs. The relative abundance of Methanosarcina (18.7%) and VadinCA11 (3.1%) increased with an increase in voltage up to 1.2V. However, the opposite was observed for Methanosaeta and Methanomassiliicoccus. The current in the BES influenced the methanogenic communities.

Removal of antibiotic sulfamethoxazole by zero-valent iron under oxic and anoxic conditions: Removal mechanisms in acidic, neutral and alkaline solutions

Removal of antibiotic sulfamethoxazole (SMX) by zero-valent iron (ZVI) was examined in the range of pH from 3.0 to 11.0 under oxic and anoxic conditions to clarify mechanisms of SMX removal in acidic, neutral and alkaline solutions. SMX removal was affected by solution pH and related to the speciation of SMX. Under the oxic condition, the maximums of SMX removal efficiency and rate were obtained at pH 3.0. The SMX removal efficiency decreased from 100 to 32% with increasing pH in the acidic solutions (3 ≦ pH ≦ 5) and increased to 88% in neutral and moderately alkaline solutions (6 ≦ pH ≦ 10). In highly alkaline solution (pH = 11), the SMX removal was significantly suppressed due to the formation of passive layer on ZVI surface. The removal rate of SMX under the oxic condition significantly declined with increasing pH. Under the anoxic condition, SMX removal was completed within 300 min in the acidic solutions and remained to less than 70% after 300 min in neutral and moderately alkaline solutions. For pH ≧ 10, no SMX removal practically occurred. The removal rate of SMX under the anoxic condition approximately remained constant in the acidic solution and largely decreased in neutral and moderately alkaline solutions. SMX removal by ZVI was found to be dominated by the reductive degradation and adsorption under both the oxic and anoxic conditions. It was concluded that ZVI has the potential for effective removal of antibiotic SMX under the oxic and anoxic conditions. A kinetic model could reasonably simulate the dynamic profiles of SMX removal.

Decomposition of sulfamethoxazole and trimethoprim by continuous UVA/LED/TiO2 photocatalysis: Decomposition pathways, residual antibacterial activity and toxicity

In this study, continuous LED/UVA/TiO2 photocatalytic decomposition of sulfamethoxazole (SMX) and trimethoprim (TMP) was investigated. More than 90% of SMX and TMP were removed within 20min by the continuous photoreactor (with the initial concentration of 400ppb for each). The removal rates of SMX and TMP decreased with higher initial antibiotics loadings. SMX was much easier decomposed in acidic condition, while pH affected little on TMP’s decomposition. 0.003% was found to be the optimum H2O2 dosage to enhance SMX photocatalytic decomposition. Decomposition pathways of SMX and TMP were proposed based on the intermediates identified by using LC–MS–MS and GC–MS. Aniline was identified as a new intermediate generated during SMX photocatalytic decomposition. Antibacterial activity study with a reference Escherichia coli strain was also conducted during the photocatalytic process. Results indicated that with every portion of TMP removed, the residual antibacterial activity decreased by one portion. However, the synergistic effect between SMX and TMP tended to slow down the antibacterial activity removal of SMX and TMP mixture. Chronic toxicity studies conducted with Vibrio fischeri exhibited 13–20% bioluminescence inhibition during the decomposition of 1ppm SMX and 1ppm TMP, no acute toxicity to V. fischeri was observed during the photocatalytic process.

Sulfamethoxazole in poultry wastewater: Identification, treatability and degradation pathway determination in a membrane-photocatalytic slurry reactor

The presence of sulfamethoxazole (SMX) in a real-time poultry wastewater was identified via HPLC analysis. Subsequently, SMX removal from the poultry wastewater was investigated using a continuous-mode membrane-photocatalytic slurry reactor (MPSR). The real-time poultry wastewater was found to have an SMX concentration of 0–2.3 mg L−1. A granular activated carbon supported TiO2 (GAC-TiO2) was synthesized, characterized and used in MPSR experiments. The optimal MPSR condition, i.e., HRT ∼125 min and catalyst dosage 529.3 mg L−1, for complete SMX removal was found out using unconstrained optimization technique. Under the optimized condition, the effect of SMX concentration on MPSR performance was investigated by synthetic addition of SMX (i.e., 1, 25, 50, 75 and 100 mg L−1) into the wastewater. Interestingly, complete removals of total volatile solids (TVS), biochemical oxygen demand (BOD) and SMX were observed under all SMX concentrations investigated. However, a decline in SMX removal rate and proportionate increase in transmembrane-pressure (TMP) were observed when the SMX concentration was increased to higher levels. In the MPSR, the SMX mineralization was through one of the following degradation pathways: (i) fragmentation of the isoxazole ring and (ii) the elimination of methyl and amide moieties followed by the formation of phenyl sulfinate ion. These results show that the continuous-mode MPSR has great potential in the removal for SMX contaminated real-time poultry wastewater and similar organic micropollutants from wastewater.

Microbial community structure and pharmaceuticals and personal care products removal in a membrane bioreactor seeded with aerobic granular sludge

A process involving the use of membrane bioreactor seeded with aerobic granular sludge (GMBR) was applied to the treatment of sewage containing pharmaceuticals and personal care products (PPCPs). The removal effects of five kinds of medicines in the reactor were investigated, and the microbial communities were constructed by polymerase chain reaction and denaturing gradient gel electrophoresis. We also determined the effects of different sludge retention and hydraulic retention times (SRT and HRT, respectively) and influent organic loading on GMBR's efficiency in processing sewage containing PPCPs. The removal effects of the GMBR on five PPCPs varied. Using the GMBR, the removal rates of prednisolone, naproxen and norfloxacin were 98.56, 84.02 and 87.85%, respectively. The removal rates of sulfamethoxazole and ibuprofen were 77.83 and 63.32%, respectively. In the system, PPCP drugs had relatively less effect on microbial diversity. A certain succession was observed in the structural variation of microbial species in the GMBR. Microorganisms that can degrade PPCPs gradually accumulated, and antibiotic-resistant microorganisms, such as Firmicutes sp., Aeromonas sp. and Nitrospira sp., served a key function in the treatment of sewage containing antibiotics. Long SRT and HRT during the GMBR process can facilitate the removal of most PPCPs. The system efficiently removed PPCPs at high influent organic loading.

Sulfamethoxazole degradation by ultrasound/ozone oxidation process in water: Kinetics, mechanisms, and pathways

In this research, sulfamethoxazole (SMX) degradation was investigated using ultrasound (US), ozone (O3) and ultrasound/ozone oxidation process (UOOP). It was proved that ultrasound significantly enhanced SMX ozonation by assisting ozone in producing more hydroxyl radicals in UOOP. Ultrasound also made the rate constants improve by kinetics analysis. When ultrasound was added to the ozonation process, the reaction rate increased by 6–26% under different pH conditions. Moreover, main intermediates oxidized by US, O3 and UOOP system were identified. Although the main intermediates in ozonation and UOOP were similar, the introduction of ultrasound in UOOP had well improved the cleavage of S–N bond. In this condition SMX become much easier to be attacked, which led to enhanced SMX removal rate in UOOP compared to the other two examined processes. Finally, the SMX degradation pathways were proposed.

Removal of emerging pollutants by Ru/TiO2-catalyzed permanganate oxidation

TiO2 supported ruthenium nanoparticles, Ru/TiO2 (0.94‰ as Ru), was synthesized to catalyze permanganate oxidation for degrading emerging pollutants (EPs) with diverse organic moieties. The presence of 1.0 g L−1 Ru/TiO2 increased the second order reaction rate constants of bisphenol A, diclofenac, acetaminophen, sulfamethoxazole, benzotriazole, carbamazepine, butylparaben, diclofenac, ciprofloxacin and aniline at mg L−1 level (5.0 μM) by permanganate oxidation at pH 7.0 by 0.3–119 times. The second order reaction rate constants of EPs with permanganate or Ru/TiO2-catalyzed permanganate oxidation obtained at EPs concentration of mg L−1 level (5.0 μM) underestimated those obtained at EPs concentration of μg L−1 level (0.050 μM). Ru/TiO2-catalyzed permanganate could decompose a mixture of nine EPs at μg L−1 level efficiently and the second order rate constant for each EP was not decreased due to the competition of other EPs. The toxicity tests revealed that Ru/TiO2-catalyzed permanganate oxidation was effective not only for elimination of EPs but also for detoxification. The removal rates of sulfamethoxazole by Ru/TiO2-catalyzed permanganate oxidation in ten successive cycles remained almost constant in ultrapure water and slightly decreased in Songhua river water since the sixth run, indicating the satisfactory stability of Ru/TiO2. Ru/TiO2-catalyzed permanganate oxidation was selective and could remove selected EPs spiked in real waters more efficiently than chlorination. Therefore, Ru/TiO2-catalyzed permanganate oxidation is promising for removing EPs with electron-rich moieties.

Internal loop photobiodegradation reactor (ILPBR) for accelerated degradation of sulfamethoxazole (SMX)

The internal loop photobiodegradation reactor (ILPBR) was evaluated for the degradation of the pharmaceutical sulfamethoxazole (SMX) using batch experiments following three protocols: photolysis alone (P), biodegradation alone (B), and intimately coupled photolysis and biodegradation (P&B). SMX was removed more rapidly by P&B than by either P or B alone, and the corresponding dissolved organic carbon (DOC) removals by P&B also were higher. The faster SMX removal probably was due to a synergy between photolysis and the rapid biodegradation of SMX by the biofilm. The greater DOC removal was brought about by the presence of biofilm bacteria able to biodegrade photolysis products. Ammonium N released during photolysis of SMX gave more evidence for the formation of intermediates and was enough in P&B experiments to support bioactivity when no other N was supplied. Clone libraries performed on the biofilms before and after the P&B experiments showed profound changes in the microbial community. Whereas Rhodopirellula baltica and Methylibium petroleiphilum PM1 dominated the biofilm after the B experiments, they were replaced by Micrococcus luteus, Delftia acidovorans, and Oligotropha carboxidovorans after the P&B experiments. The changes in microbial community structure mirrored the change in function in the P&B experiments: SMX biodegradation (presumably the roles of R. baltica and M. petroleiphilum) was out-competed by SMX photolysis, but biodegradation of photolysis products (most likely by M. luteus and D. acidovorans) became important. The higher removal rates of SMX and DOC, as well as the changes in microbial community structure, confirm the value of intimately coupling photolysis with biodegradation in the ILPBR.

Ozone and photocatalytic processes to remove the antibiotic sulfamethoxazole from water

In this study, water containing the pharmaceutical compound sulfamethoxazole (SMT) was subjected to the various treatments of different oxidation processes involving ozonation, and photolysis and catalysis under different experimental conditions. Removal rates of SMT and total organic carbon (TOC), from experiments of simple UVA radiation, ozonation (O 3), catalytic ozonation (O 3/TiO 2), ozone photolysis (O 3/UVA), photocatalytic oxidation (O 2/TiO 2/UVA) and photocatalytic ozonation (O 3/UVA/TiO 2), have been compared. Photocatalytic ozonation leads to the highest SMT removal rate (pH 7 in buffered systems, complete removal is achieved in less than 5 min) and total organic carbon (in unbuffered systems, with initial pH = 4, 93% TOC removal is reached). Also, lowest ozone consumption per TOC removed and toxicity was achieved with the O 3/UVA/TiO 2 process. Direct ozone and free radical reactions were found to be the principal mechanisms for SMT and TOC removal, respectively. In photocatalytic ozonation, with buffered (pH 7) aqueous solutions phosphates (buffering salts) and accumulation of bicarbonate scavengers inhibit the reactions completely on the TiO 2 surface. As a consequence, TOC removal diminishes. In all cases, hydrogen peroxide plays a key role in TOC mineralization. According to the results obtained in this work the use of photocatalytic ozonation is recommended to achieve a high mineralization degree of water containing SMT type compounds.