Sulfamethoxazole Concentration Research Articles

Oxidation of Sulfamethoxazole by Rice Husk Biochar-Activated Persulfate

In the present study, biochars from rice husk were synthesized via pyrolysis at 400, 550, 700 and 850 °C for 1 h under a limited O2 atmosphere, characterized with a various techniques of and used as catalysts to activate persulfate and to degrade sulfamethoxazole (SMX). After physicochemical characterization of biochars. SMX degradation tests were performed using different water matrices, persulfate biochar and SMX concentrations and different initial pH solutions. Also, spiked solutions with bicarbonate, chloride, calcium nitrate, humic acid or alcohols were tested. It was found that catalytic reactivity rises with the pyrolysis temperature. Biochar is crucial for the oxidation of SMX and it can be described with a pseudo first–order kinetic model. Real matrices hinder the oxidation process, in waste water the SMX removal is 41% in 90 min, comparable with the inhibition obtained with spiked with bicarbonates solution (52% removal within 90 min) while complete removal can be achieved in ultrapure water matrices. The presence of alcohol slightly inhibits degradation contrary to the addition of sodium azide which causes significant inhibition, this is an evidence that degradation either under electron transfer/singlet oxygen control or dominated by surface-bound radicals.

Transport and dilution of fluvial antibiotic in the Upper Gulf of Thailand

A three-dimensional hydrodynamic-antibiotic model is developed to investigate the transport and dilution of sulfamethoxazole (SMX) in the Upper Gulf of Thailand (UGoT). The simulation produced a spatially averaged annual mean SMX concentration of 0.58 μgm−3, which varied slightly between seasons assuming a temporally constant river SMX loading observed in August. In contrast, the horizontal distribution of SMX concentrations strongly varied with season because of the changing residual currents. In addition, SMX is diluted to concentrations lower than 10% of those in river waters a short distance offshore of the estuaries. To better understand this behavior, we examined the relationship between salinity and SMX concentrations in the UGoT. The annual budget demonstrates that 98% of SMX in the UGoT is removed by natural decomposition. As the concentrations of fluvial pollutants in the UGoT depend on their river loading and decomposition rates, functions were derived to predict pollutant concentrations and flushing times based on the river input flux and half-life.

Occurrence of antibiotics and antibiotic resistance genes in WWTP effluent-receiving water bodies and reclaimed wastewater treatment plants

There is a growing concern on the fate and the consequent ecological or health risks of antibiotics and antibiotic resistance genes (ARGs) in natural or artificial water environment. The effluent of wastewater treatment plants (WWTPs) has been reported to be an important source of antibiotics and ARGs in the environment. WWTP effluent could be discharged into surface water bodies or recycled, either of which could lead to different exposure risks. The impact of WWTP effluents on the levels of antibiotics and ARGs in effluent-receiving water bodies and the removal efficiency of antibiotics and ARGs in reclaimed wastewater treatment plants (RWTPs) were seldom simultaneously investigated. Thus, in this study, we investigated the occurrence of antibiotics and ARGs in four WWTP effluents, and their downstream effluent-receiving water bodies and RWTPs in seasons of low-water-level. The total concentrations of ofloxacin, norfloxacin, ciprofloxacin, roxithromycin, azithromycin, erythromycin, tetracycline, oxytetracycline, chlortetracycline, and sulfamethoxazole in the secondary effluents were 1441.6–4917.6 ng L−1. Ofloxacin had the highest concentration. The absolute and relative abundances of total ARGs (qnrD, qnrS, ermA, ermB, tetA, tetQ, sul1, and sul2) in the secondary effluents were 103–104 copies mL−1 and 10−4–10−2 ARG/16S rRNA. Sul1 and sul2 were the major species with the highest detection frequencies and levels. In most cases, WWTP effluents were not the major contributors to the levels and species of antibiotics and ARGs in the surface water bodies. Four RWTPs removed 43.5–98.9% of antibiotics and − 0.19–2.91 log of ARGs. Antibiotics and ARGs increased in chlorination, ozonation and filtration units. Antibiotics had significantly positive correlations with ARGs, biological oxygen demands, total phosphorus, total nitrogen, and ammonia nitrogen in the four effluent-receiving water bodies. In RWTPs, the total concentrations of antibiotics showed a significant positive correlation with the total abundance of ARGs.

Screening ecological risk of pesticides and emerging contaminants under data limited conditions – Case study modeling urban and agricultural watersheds with OrganoFate

The increasing number of chemicals used by society requires accessible, easy to implement tools to perform screening-level ecological risk assessments. However, field data to calibrate and validate screening tools is challenging to obtain for many watersheds. Thus, the evaluation must be done under data limited conditions. Here we employ a fate and transport model, OrganoFate, to predict environmental concentrations of contaminants of emerging concern (CECs) as well as a number of pesticides. CECs evaluated include antibacterial compounds sulfamethoxazole and triclocarban and a flame-retardant tris(1,3-dichloro-2-propyl)phosphate (TDCPP). We also evaluated widely used pesticides chlorpyrifos, bifenthrin and esfenvalerate. We predict concentrations of the contaminants in high-risk watersheds which were dominated by either urban or agricultural development and have small aquatic compartments. Screening-level predictions were in good agreement with observed concentrations in surface water and sediment. Maximum predicted concentrations were close to the highest observed concentrations for CECs, only ~0.1 μg/L greater for sulfamethoxazole and triclocarban concentrations, and for TDCPP <5 μg/L higher. ChemFate was also employed to screen possible aquatic health impacts. Results demonstrated possible CEC aquatic health risk for TDCPP and triclocarban (risk quotients of 0.9 and 1.1 respectively). For pesticides, exceedance of effect (EC50) and lethal (LC50) endpoints was predicted for various taxonomic groups which include aquatic invertebrates, fish, amphibians, and benthic organisms.

Solar light induced photocatalytic removal of sulfamethoxazole from water and wastewater using BiOCl photocatalyst

The photocatalytic activity of bismuth oxychloride (BiOCl) toward sulfamethoxazole (SMX) elimination was investigated. BiOCl was synthesized according to a simple method using thiourea. Its physicochemical characteristics were determined by nitrogen physisorption, X-Ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy and transmission electron microscopy. Simulated solar irradiation and 1 g/L BiOCl, could effectively remove 0.5 mg/L SMX in less than 90 min. An increase in SMX concentration from 0.25 mg/L to 4 mg/L decreased the observed kinetic constant. Concerning the pH effect, it was found that under alkaline conditions SMX removal was slightly hindered. The water matrix's influence on SMX removal was explored, carrying out experiments in real water matrices, (bottled water (BW) and secondary effluent (WW)). Interestingly SMX removal was not practically altered in WW secondary effluent, but it was slightly hindered in BW bottled water. Experiments, performed in synthetic matrices, revealed that the presence of bicarbonates and chlorides slightly slowed down degradation kinetics, while humic acid enhanced SMX removal at concentrations up to 10 mg/L. Finally, an enhancement on SMX degradation was observed in the presence of persulfate. Quenching experiments of potential reactive species revealed that SMX degradation takes place mainly through reaction with hydroxyl radicals and photogenerated electrons.

Impact of sulfamethoxazole on a riverine microbiome

The continued emergence of bacterial pathogens presenting antimicrobial resistance is widely recognised as a global health threat and recent attention focused on potential environmental reservoirs of antibiotic resistance genes (ARGs). Freshwater environments such as rivers represent a potential hotspot for ARGs and antibiotic resistant bacteria as they are receiving systems for effluent discharges from wastewater treatment plants (WWTPs). Effluent also contains low levels of different antimicrobials including antibiotics and biocides. Sulfonamides are antibacterial chemicals widely used in clinical, veterinary and agricultural settings and are frequently detected in sewage sludge and manure in addition to riverine ecosystems. The impact of such exposure on ARG prevalence and diversity is unknown, so the aim of this study was to investigate the release of a sub-lethal concentration of the sulfonamide compound sulfamethoxazole (SMX) on the river bacterial microbiome using a flume system. This system was a semi-natural in vitro flume using river water (30 L) and sediment (6 kg) with circulation to mimic river flow. A combination of ‘omics’ approaches were conducted to study the impact of SMX exposure on the microbiomes within the flumes. Metagenomic analysis showed that the addition of low concentrations of SMX (<4 μg L−1) had a limited effect on the bacterial resistome in the water fraction only, with no impact observed in the sediment. Metaproteomics did not show differences in ARGs expression with SMX exposure in water. Overall, the river bacterial community was resilient to short term exposure to sub-lethal concentrations of SMX which mimics the exposure such communities experience downstream of WWTPs throughout the year.

Bioremoval and tolerance study of sulfamethoxazole using whole cell Trichoderma harzianum isolated from rotten tree bark

Antibiotic contamination raises concerns over antibiotic resistance genes (ARGs), which can severely impact the human health and environment. Sulfamethoxazole (SMX) is a widely used antibiotic that is incompletely metabolized in the body. In this study, the research objectives were (1) to isolate the native strain of Trichoderma sp. from the environment and analyze the tolerance toward SMX concentration by evaluating fungal growth, and (2) to investigate the potential of SMX removal by fungi. The potential fungi isolated from rotten tree bark showed 97% similarity to Trichoderma harzianum (Accession no. MH707098.1). The whole cell of fungi was examined in vitro; the strain Trichoderma harzianum BGP115 eliminated 71% of SMX after 7 days, while the white rot fungi Trametes versicolor, demonstrated 90% removal after 10 days. Furthermore, the tolerance of fungal growth toward SMX concentration at 10 mg L−1 was analyzed, which indicated that Trichoderma harzianum BGP115 (the screened strain) exhibited more tolerance toward SMX than Trametes versicolor (the reference strain). The screened fungi isolated from rotted tree bark demonstrated the ability of SMX bioremoval and the potential to be tolerant to high concentrations of SMX.

Efficient removal of emerging contaminant sulfamethoxazole in water by ozone coupled with calcium peroxide: Mechanism and toxicity assessment

Sulfamethoxazole (SMX) is a widely distributed emerging contaminant, which will bring serious harm to ecology and human health. Herein, evaluation of ozone (O3) coupled with calcium peroxide (CaO2) for SMX elimination was carried out. The results showed that CaO2 could promote SMX elimination in O3 system. The removal efficiency was improved from 65.6% to 73.9% when the CaO2 dosage was 0.06 g L−1. O3 dosage of 0.55 g h−1 was beneficial to SMX degradation. With decrease of initial SMX concentration, the removal of SMX firstly enhanced and then declined. Compared with alkaline, acidic and neutral conditions were favorable for SMX degradation. ROS including ·OH, ·O2− and 1O2 play critical role for SMX degradation. Synergetic effect could be established between O3 and CaO2, which encouraged formation of ·OH and accelerated SXM decomposition. The total organic carbon (TOC) and chemical oxygen demand (COD) were all declined after O3/CaO2 treatment. According to results of liquid chromatography-mass spectrometry (LC-MS) and references, four major pathways were proposed. The O3/CaO2 technology was also suitable for practical wastewater treatment. QSAR calculation and seed germination experiment showed that toxicity of the treatment solution was alleviated after O3/CaO2 treatment.

Differential effects of sulfamethoxazole concentrations on the enzymatic dynamics of aerobic composting

Enzymatic activities play an important role in the biological composting processing of agricultural wastes. This paper explores the effect of sulfamethoxazole (SMX) (Control, 25 mg/kg, 50 mg/kg, and 100 mg/kg) on the enzymatic activities of cellulase, protease, urease, and arylsulfatase. Compost samples were taken at three different intervals for analysis (day 0, day 25, and day 45). The findings revealed that at the start of the composting process, a strongly negative effect on enzymatic behavior was observed, and this response was significantly dependent on SMX concentrations (p < 0.05). The inhibition was consistent across all treatments. According to the results, the negative impact of SMX on community structure can result in selection pressure. Furthermore, all of the treatments had drastically improved enzymatic activity by the end of the composting process (day 45). This effect was presumably caused by the deterioration of SMX and a substantial stress reduction.

Environmental Concentrations of Sulfonamides Can Alter Bacterial Structure and Induce Diatom Deformities in Freshwater Biofilm Communities.

Since the early 1920s, the intensive use of antibiotics has led to the contamination of the aquatic environment through diffuse sources and wastewater effluents. The antibiotics commonly found in surface waters include sulfamethoxazole (SMX) and sulfamethazine (SMZ), which belong to the class of sulfonamides, the oldest antibiotic class still in use. These antibiotics have been detected in all European surface waters with median concentrations of around 50 ng L–1 and peak concentrations of up to 4–6 μg L–1. Sulfonamides are known to inhibit bacterial growth by altering microbial production of folic acid, but sub-lethal doses may trigger antimicrobial resistance, with unknown consequences for exposed microbial communities. We investigated the effects of two environmentally relevant concentrations (500 and 5,000 ng L–1) of SMZ and SMX on microbial activity and structure of periphytic biofilms in stream mesocosms for 28 days. Measurement of sulfonamides in the mesocosms revealed contamination levels of about half the nominal concentrations. Exposure to sulfonamides led to slight, transitory effects on heterotrophic functions, but persistent effects were observed on the bacterial structure. After 4 weeks of exposure, sulfonamides also altered the autotrophs in periphyton and particularly the diversity, viability and cell integrity of the diatom community. The higher concentration of SMX tested decreased both diversity (Shannon index) and evenness of the diatom community. Exposure to SMZ reduced diatom species richness and diversity. The mortality of diatoms in biofilms exposed to sulfonamides was twice that in non-exposed biofilms. SMZ also induced an increase in diatom teratologies from 1.1% in non-exposed biofilms up to 3% in biofilms exposed to SMZ. To our knowledge, this is the first report on the teratological effects of sulfonamides on diatoms within periphyton. The increase of both diatom growth rate and mortality suggests a high renewal of diatoms under sulfonamide exposure. In conclusion, our study shows that sulfonamides can alter microbial community structures and diversity at concentrations currently present in the environment, with unknown consequences for the ecosystem. The experimental set-up presented here emphasizes the interest of using natural communities to increase the ecological realism of ecotoxicological studies and to detect potential toxic effects on non-target species.

Aminated chitosan/cellulose nanocomposite microspheres designed for efficient removal of low-concentration sulfamethoxazole from water

The ppt to ppb sulfamethoxazole (SMX) entering natural water bodies and possibly present in drinking water is not significantly removed and remain persistent and toxic by conventional adsorbents. Aminated chitosan/cellulose nanocomposite microspheres (ACNM) were prepared by in-situ solid phase grafting methods for low concentration of SMX removal. The physical and chemical properties of ACNM were characterized by SEM, FTIR and XRD etc. 10 mg L−1 SMX was used to simulate the low concentration of SMX in the aqueous phase, SMX adsorption on ACNM could reached the equilibrium within 30 min. The adsorption process was better kinetically fitted with the pseudo-second-order kinetic model and Langmuir isothermal model, suggesting that monolayer chemical adsorption was the dominant adsorption process. The removal efficiency of SMX reached 99.18%, and the adsorption capacity was 13.59 mg g−1. The adsorption mechanism was also studied. ACNM retained 96.8% of the initial adsorption capacity after 3 cycles. Column adsorption experiments were studied to determine the best adsorption conditions.

Seasonal occurrence and risk assessment of pharmaceutical and personal care products in Bengaluru rivers and lakes, India

Water samples were collected from 35 locations in the Arkavathi river, its tributaries and lakes spread across the Bengaluru metropolitan area in Southern India during monsoon (October 2018) and post-monsoon (February 2019) seasons. Eleven pharmaceutical and personal care products (PPCPs) (sulfamethoxazole, chloramphenicol, ethyl paraben, diclofenac, propylparaben, ibuprofen, BP-1, oxybenzone, bisphenol A, triclosan, triclocarban) were investigated for their occurrence, seasonal variation, and toxicological effects on the biota. The PPCPs belong to different classes like non-steroidal anti-inflammatory drugs, antibiotics, antibacterials, UV-filters, plasticizer, and preservatives. Ibuprofen was present in high concentrations (1834 ng/L) followed by triclosan (1761 ng/L) and diclofenac (1130 ng/L) in the river. Samples collected during monsoon season had lower concentrations of sulfamethoxazole, chloramphenicol and diclofenac whereas rest of the target analytes had lower concentrations during post-monsoon season. Dilution in monsoon season and adsorption to the sediments in the post-monsoon season can be the possible reasons for the seasonal variability. The highest detection frequencies of PPCPs at the Arkavathi river indicates the continuous discharge of wastewater from highly populated metropolitan and industrial areas. The ecotoxicity data for diclofenac and triclosan suggest high risk (Hazard Quotient >1) for various species of fish and algae observed from the Kumbalagodu (S20) and Shanumangala (S19) stations respectively from the mid-stream of Arkavathi river. It was followed by bisphenol A with a hazard quotient of 0.88 in Banashankari (S25) that can affect specific species of fish. No human health risk assessment was estimated from the identified sampling stations. This is the first report on seasonal occurrence of PPCPs with their associated toxicological studies from the Arkavathi river, its tributaries, and lakes across the Bengaluru metropolis.

Effects of Sulfamethoxazole on Growth and Antibiotic Resistance of A Natural Microbial Community

Diffuse environmental antibiotic and antibiotic resistance gene contamination is increasing human and animal exposure to these emerging compounds with a consequent risk of reduction in antibiotic effectiveness. The present work investigated the effect of the antibiotic sulfamethoxazole (SMX) on growth and antibiotic resistance genes of a microbial community collected from an anaerobic digestion plant fed with cattle manure. Digestate samples were used as inoculum for concentration-dependent experiments using SMX at various concentrations. The antibiotic concentrations affecting the mixed microbial community in terms of growth and spread of resistant genes (sul1, sul2) were investigated through OD (Optical Density) measures and qPCR assays. Moreover, SMX biodegradation was assessed by LC-MS/MS analysis. The overall results showed that SMX concentrations in the range of those found in the environment did not affect the microbial community growth and did not select for antibiotic-resistant gene (ARG) maintenance or spread. Furthermore, the microorganisms tested were able to degrade SMX in only 24 h. This study confirms the complexity of antibiotic resistance spread in real matrices where different microorganisms coexist and suggests that antibiotic biodegradation needs to be included for fully understanding the resistance phenomena among bacteria.

Degradation of sulfamethoxazole in water by a combined system of ultrasound/PW12/KI/H2O2

Sulfamethoxazole, one of the most frequently used sulfonamide antibiotics, has been frequently detected in the aquatic environment. The long-term presence of sulfamethoxazole in natural water bodies can easily lead to the development of resistant bacteria, posing a serious threat to the health and safety of aquatic organisms and humans. In this paper, the degradation of sulfamethoxazole by a combined system of ultrasound/PW12/KI/H2O2 was investigated based on advanced oxidation techniques. The effects of different factors, such as ultrasonic power, initial pH, KI concentration, H2O2 concentration, PW12 concentration and initial concentration of sulfamethoxazole, on the degradation effect were discussed. The reactive radicals in the system, the degradation products of sulfamethoxazole and the main degradation pathways were analyzed. The results indicate that the US/PW12/KI/H2O2 system is of great potential application value in removal of organic pollution and environmental purification.

Fourier transform‐infrared assessment of cholesterol effect on antibiotic resistance of Salmonella Typhimurium

In this study, the effect of cholesterol on antibiotic resistance of Salmonella Typhimurium was investigated. Antibiotic resistance patterns revealed that the bacterium was susceptible to ampicillin, streptomycin, sulfamethoxazole/trimethoprim, ciprofloxacin, tetracycline, chloramphenicol, and gentamicin and resistant to penicillin, erythromycin, and vancomycin. The minimum inhibitory concentrations (MICs) of ampicillin, streptomycin, ciprofloxacin, and sulfamethoxazole/ trimethoprim antibiotics were found as 16, 128, 0.25, and 16 mg/L, respectively. When the effect of cholesterol on antibiotic resistivity was examined, it was found that MICs increased in cholesterol medium than in non-cholesterol medium. The increase in MICs and decrement in inhibition zones was considered as the decreasing effect of cholesterol on the sensitivity of Salmonella Typhimurium. The effect of cholesterol on the antibiotic sensitivity of Salmonella Typhimurium was also assessed by Fourier transformed infrared (FT-IR) spectroscopy, and the results indicated that new functional groups were observed at different wavelengths in the presence of cholesterol. Practical applications Antibiotic resistance is a global phenomenon resulting in the emergence of pathogens with resistance to clinically important antibiotics. Antibiotic resistance in foodborne pathogens such as Salmonella is a major concern for public health safety. Significant increase in bacterial resistance makes it increasingly necessary to develop new drugs and antibiotic activity modifiers and effective techniques for treatment. Fourier transformed infrared (FT-IR) can be used as a rapid and precise method for the assessment of cholesterol effect on antibiotic resistance pattern of Salmonella Typhimurium.

Assessment of an aerobic granular sludge system in the presence of pharmaceutically active compounds by quantitative image analysis and chemometric techniques

In this study, a sequencing batch reactor (SBR) with aerobic granular sludge (AGS) was operated with synthetic wastewater containing environmental relevant concentrations of 17β-estradiol (E2), 17α-ethinylestradiol (EE2) and sulfamethoxazole (SMX). Despite the presence of the studied PhAC, the granular fraction clearly predominated (TSSgran/TSS ranging from 0.82 to 0.98) throughout the monitoring period, presenting aggregates with high organic fraction (VSS/TSS above 0.83) and good settling characteristics (SVI5 ranging from 15 to 39 mL/gTSS). A principal component analysis (PCA) with quantitative image analysis (QIA) based data allowed to distinguish the different operational periods, namely with mature granules (CONT), and the E2, EE2, and SMX feeding periods. It further revealed a positive relationship between the biomass density, sludge settling ability, overall and granular biomass contents, granulation properties, granular biomass fraction and large granules fraction and size. Moreover, a discriminant analysis (DA) allowed to successfully discriminate not only the different operational periods, mainly by using the floccular apparent density, granular stratification and contents data, but also the PhAC presence in samples. The filamentous bacteria contents, sludge settling properties, settling properties stability and granular stratification, structure and contents parameters were found to be crucial for that purpose.

Degradation of sulfamethoxazole by UV/sulfite in presence of oxygen: Efficiency, influence factors and mechanism

In this study, the degradation efficiency and mechanism of sulfamethoxazole (SMX) by UV/sulfite system in presence of oxygen were investigated systematically. The results indicated that SMX could be effectively removed by UV/sulfite following a pseudo first-order kinetic model. Compared to SMX photolysis under UV irradiation, its removal in UV/sulfite system was significantly enhanced, which was mainly ascribed to the formed reactive oxygen species. Sulfate radical (SO4−) was proved to be the major active radical for SMX degradation by scavenging experiments using methanol and tert-butanol as scavengers. UV photolysis and radical oxidation were two degradation pathways of SMX in UV/sulfite system, and their contribution to SMX removal at pH 6.9 was 38.8% and 61.2%, respectively. The degradation rate constant of SMX was decreased from 0.1415 to 0.0358 min−1 as the pH increased from 4.0 to 9.3, because pH is an important influence factor on species distribution of both SMX and S(Ⅳ), further influencing direct SMX photolysis and formation of active species. SMX degradation was increased with the increase of S(IV) concentration from 0 to 1000 μM, while it was decreased with the increase of initial SMX concentration. The presence of HCO3−, Ca2+ and fulvic acid inhibited the degradation of SMX in UV/sulfite system, while an insignificant effect on SMX removal was observed with the addition of Cl−, SO42− and Cu2+. NO3− could facilitate SMX degradation in UV/sulfite process as a precursor to form hydroxyl radical. Under the direct UV photolysis and radical oxidation, five degradation products of SMX were produced by hydroxylation, S–N bond cleavage of sulfonamide, and oxidation of amino group. Consequently, UV/sulfite could be an efficient approach for SMX removal from polluted water.

The fate and impacts of pharmaceuticals and personal care products and microbes in agricultural soils with long term irrigation with reclaimed water

Reclaimed water is an important water resource to alleviate the agricultural water crisis around the world. Meanwhile, the environmental behavior of emerging contaminants and the impact on soil microorganisms during the reuse of recycled water have attracted wide attention. In this study, the content of trimethoprim and sulfamethoxazole in the 0–120 cm soil irrigated with reclaimed water increased by 42% and 61%, respectively, compared with the soil irrigated with groundwater water. Trimethoprim and sulfamethoxazole both showed a downward migration trend after 12 years of irrigation with reclaimed water. The reclaimed irrigation resulted in the peak concentration of trimethoprim and sulfamethoxazole at the depth of 0–120 cm soil increased to 2.3 and 1.8 times of the control, while no significant change on the concentration of triclosan in soil was found. The three types of pharmaceuticals and personal care products showed significant increase in the surface soil from 0 to 40 cm. The total bacterial abundance significantly increased by 16% after irrigation with reclaimed water, but there was no significant effect on the total archaea abundance (p > 0.05). The correlation results showed high negative associations between the rate of variation of soil pharmaceuticals and personal care products and the total number of bacteria (p < 0.05), in which the increase of soil pharmaceuticals and personal care products concentration under irrigation with reclaimed water would reduce the soil microbial abundance. This study will help us understand the fate of three chemical components in soil with long term irrigation with reclaimed water and their effects on soil microorganisms.

Modeling of photolytic degradation of sulfamethoxazole using boosted regression tree (BRT), artificial neural network (ANN) and response surface methodology (RSM); energy consumption and intermediates study

This study explores the boosted regression trees (BRT), artificial neural network (ANN) and response surface methodology (RSM) to model and optimize the operational variables for the simulation of the Photolytic degradation of Sulfamethoxazole (SMX) and concurrent total organic carbon (TOC) removal, based on the experimental data set. Four candidate variables involving initial pH (2–11), initial SMX concentration (50–200 mg L−1), temperature (15–45 °C) and time (6–120 min) were considered for simultaneous optimization of SMX and TOC degradation. The result revealed that all the three models are statistically considerable as the values of R, R2, adj-R2 are >0.85, thus be deemed to work well in data fitting, prediction, and optimization, nevertheless, the values of R, R2, adj-R2, RMSE, MAE and AAD are far better for ANN and BRT than RSM method. The ∼100% SMX degradation conditions were found to be as follows: treatment time: 25 min, pH: 2.0, temperature: 35 °C and SMX concentration: 50 mg L−1, while the maximum possible removal of TOC under the given conditions was ∼25%. The percentage contribution (PC) of each variable was deduced by ANOVA analysis of proposed quadratic models which indicated that time and pH are important factors than temperature and SMX concentration. The photolytic intermediates and inorganic ions of SMX, were identified and a potential route of transformation was also proposed.

Promoted elimination of antibiotic sulfamethoxazole in water using sodium percarbonate activated by ozone: Mechanism, degradation pathway and toxicity assessment

Herein, sodium percarbonate (SPC), an effective and environment-friendly oxidant, was activated by ozone (O3) for promoting elimination of sulfamethoxazole (SMX) in water. The effect of various parameters including SPC dosage, O3 dosage, SPC concentration, pH value and radical scavenger on SPC elimination was investigated firstly. Results showed that with increase of SMX dosage, the removal efficiency of SMX firstly improved and then declined. With optimal SPC dosage of 0.2 g/L, the removal efficiency of SMX rose by 16.4%, and corresponding kinetic constant multiplied by 1.7 times. Improving O3 dosage and reducing SMX concentration were beneficial to SMX elimination. Compared with acidic and neutral conditions, alkaline condition was favorable for SMX elimination. Radical trapping experiment showed that 1O played an important role during SMX decomposition. SPC addition could promote OH production in O3 system. The comparison of active species in different reaction system suggested that OH and O2− also play crucial role for SMX elimination. TOC and COD removal were all enhanced after 30 min treatment in O3/SPC system. Degradation process of SMX was inspected via UV–Vis spectra, pH variation, conductivity variation and ammonia nitrogen variation. The degradation pathway was predicted by discrete Fourier transform (DFT) coupled with literatures. Finally, the toxicity of degradation intermediates was evaluated by US Environmental Protection Agency Toxicity Estimation Software Tool (US-EPA-TEST).