A review of bismuth-based photocatalysts for antibiotic degradation: Insight into the photocatalytic degradation performance, pathways and relevant mechanisms.

The intensive production and utilization of antibiotics worldwide has inevitably led to releases of very large amounts of these medicines into the environment, and numerous strategies have recently been developed to eliminate antibiotic pollution. Therefore, bismuth-based photocatalysts have attracted much attention due to their high adsorption of visible light and low production cost. This review summarizes the performance, degradation pathways and relevant mechanisms of typical antibiotics during bismuth-based photocatalytic degradation. First, the band gap and redox ability of the bismuth-based catalysts and modified materials (such as morphology, structure mediation, heterojunction construction and element doping) were compared and evaluated. Second, the performance and potential mechanisms of bismuth oxides, bismuth sulfides, bismuth oxyhalides and bismuth-based metal oxides for antibiotic removal were investigated. Third, we analysed the effect of co-existing interfering substances in a real water matrix on the photocatalytic ability, as well as the coupling processes for degradation enhancement. In the last section, current difficulties and future perspectives on photocatalytic degradation for antibiotic elimination by bismuth-based catalysts are summarized. Generally, modified bismuth-based compounds showed better performance than single-component photocatalysts during photocatalytic degradation for most antibiotics, in which h+ played a predominant role among all the related reactive oxygen species. Moreover, the crystal structures and morphologies of bismuth-based catalysts seriously affected their practical efficiencies.

Transformation of erythromycin during secondary effluent soil aquifer recharging: Removal contribution and degradation path.

Erythromycin (ERY), a widely used antibiotic, has recently been detected in municipal secondary effluents and poses serious threats to human health during wastewater reusing. In this study, the removal, fate, and degradation pathway of ERY in secondary effluent during soil aquifer treatment was evaluated via laboratory-scale SAT tests. Up to a 92.9% reduction of ERY in synthetic secondary effluent was observed in 1.0m depth column system, which decreased to 64.7% when recharged with wastewater treatment plant secondary effluent. XRD-fractionation results demonstrated that the transphilic acid and hydrophobic acid fractions in secondary effluent compete for the adsorption sites of the packed soil and lead to a declined ERY removal. Moreover, aerobic biodegradation was the predominant role for ERY removal, contributing more than 60% reduction of ERY when recharged with synthetic secondary effluent. Destruction of 14-member macrocyclic lactone ring and breakdown of two cyclic sugars (l-cladinose and d-desosamine) were main removal pathways for ERY degradation, and produced six new intermediates.

Utilization of artificial recharged effluent as makeup water for industrial cooling system: corrosion and scaling.

The secondary effluent from wastewater treatment plants was reused for industrial cooling water after pre-treatment with a laboratory-scale soil aquifer treatment (SAT) system. Up to a 95.3% removal efficiency for suspended solids (SS), 51.4% for chemical oxygen demand (COD), 32.1% for Cl(-) and 30.0% SO4(2-) were observed for the recharged secondary effluent after the SAT operation, which is essential for controlling scaling and corrosion during the cooling process. As compared to the secondary effluent, the reuse of the 1.5 m depth SAT effluent decreased the corrosion by 75.0%, in addition to a 55.1% decline of the scales/biofouling formation (with a compacted structure). The experimental results can satisfy the Chinese criterion of Design Criterion of the Industrial Circulating Cooling Water Treatment (GB 50050-95), and was more efficient than tertiary effluent which coagulated with ferric chloride. In addition, chemical structure of the scales/biofouling obtained from the cooling system was analyzed.

Dissolved organic matter removal during coal slag additive soil aquifer treatment for secondary effluent recharging: Contribution of aerobic biodegradation.

Recycling wastewater treatment plant (WWTP) effluent at low cost via the soil aquifer treatment (SAT), which has been considered as a renewable approach in regenerating potable and non-potable water, is welcome in arid and semi-arid regions throughout the world. In this study, the effect of a coal slag additive on the bulk removal of the dissolved organic matter (DOM) in WWTP effluent during SAT operation was explored via the matrix configurations of both coal slag layer and natural soil layer. Azide inhibition and XAD-resins fractionation experiments indicated that the appropriate configuration designing of an upper soil layer (25 cm) and a mixture of soil/coal slag underneath would enhance the removal efficiency of adsorption and anaerobic biodegradation to the same level as that of aerobic biodegradation (31.7% vs 32.2%), while it was only 29.4% compared with the aerobic biodegradation during traditional 50 cm soil column operation. The added coal slag would preferentially adsorb the hydrophobic DOM, and those adsorbed organics could be partially biodegraded by the biomass within the SAT systems. Compared with the relatively lower dissolved organic carbon (DOC), ultraviolet light adsorption at 254 nm (UV-254) and trihalomethane formation potential (THMFP) removal rate of the original soil column (42.0%, 32.9%, and 28.0%, respectively), SSL2 and SSL4 columns would enhance the bulk removal efficiency to more than 60%. Moreover, a coal slag additive in the SAT columns could decline the aromatic components (fulvic-like organics and tryptophan-like proteins) significantly.

Effect of pig manure-derived sulfadiazine on species distribution and bioactivities of soil ammonia-oxidizing microorganisms after fertilization.

To evaluate the effect of pig manure-derived sulfadiazine (SDZ) on the species distribution and bioactivities of ammonia-oxidizing microorganisms (AOMs), ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA) and complete ammonia oxidizer (comammox) within the soil were investigated pre- and post-fertilization. Kinetic modeling and linear regression results demonstrated that the DT50 value of different SDZ fractions under initial SDZ concentrations of 50 and 100 mg·kg-1 exhibited the following trend: total SDZ>CaCl2-extractable SDZ>MeOH-extractable SDZ, whereas their inhibiting effect on AOMs showed an opposite trend. qPCR analysis suggested that comammox was the predominant ammonia oxidizer in soils regardless of SDZ addition, accounting for as much as 77.2-94.7% of the total amoA, followed by AOA (5.3-22.5%), whereas AOB (<0.5%) was the lowest. The SDZ exhibited a significant effect on the AOM abundance. Specifically, SDZ exerted the highest inhibitory effect on comammox growth, followed by AOA, whereas negligible for AOB. The community diversity of AOMs within the pig manure-fertilized soils was affected by SDZ, and AOA Nitrososphaera cluster 3 played a key role in potential ammonia oxidation capacity (PAO) maintenance. This study provides new insights into the inhibition mechanisms of pig manure-derived antibiotics on AOMs within the fertilized soil.

Removal trend of amoxicillin and tetracycline during groundwater recharging reusing: Redox sensitivity and microbial community response.

The abundant existence of antibiotics within the effluent of wastewater treatment plant seriously threatened their safety recharging. To investigate the fate and biodegradation of those toxic antibiotics within the soil aquifer system, typical antibiotics of amoxicillin (AMX) and tetracycline (TC) were selected and their removal mechanisms were investigated. Experimental results revealed that totally 93.4% and 87.2% of the AMX and TC recharged (10 µg/L) were, respectively, removed within 1 m depth column operation. Specifically, the aerobic biodegradation, abiotic processes and anoxic/anaerobic microorganism contributed as higher as 37.5%, 33.7% and 28.8% of the AMX reduction, via the controlling tests of NaN3 inhibition and soil sterilisations. By contrast, the percentage contribution of the TC was aerobic (54.3%) ˃abiotic processes (32.7%) ˃anoxic/anaerobic (13.0%), a higher aerobic degradation whereas weaker anoxic/anaerobic microorganism. Column systems (CSs) were constructed to study the effect of redox conditions (methanogenic, sulfate-reducing, nitrate-reducing, aerobic) on antibiotics degradation, and microbial community results revealed that Verrucomicrobia, Actinobacteria, Deinococcus-Thermus and Armatimonadetes contributed to the aerobic biodegradation of TC. For comparison, AMX could be efficiently degraded under nitrate reduction (19.95%) > sulfate reduction (16.64%) > methanogenic (9.53%), and Actinobacteria, Bacteroidetes and Verrucomicrobia were the dominant bacteria for AMX degradation. This study provided optimal directions for antibiotics removal within the groundwater recharging systems and is conducive to obtain highly value-added reclaimed water.

Optimization of the co-digestion of sewage sludge, maize straw and cow manure: microbial responses and effect of fractional organic characteristics.

The aim of this study was to evaluate the efficiency and optimization of co-digestion using sewage sludge (SS), maize straw (MS) and cow manure (CM) as feeds, and the effects of the mixing ratio and C/N ratio of the substrates were analyzed in detail. Among the three substrates tested, CM/MS exhibited better digestion than CM/SS and SS/MS in terms of all measures, including total daily biogas and net methane volume production, due to the hydrophilic characteristics and high level of biodegradability of CM, as well as its higher C/N ratio. The average biogas production was 613.8 mL/g VS for the co-digestion of CM/MS at a feed concentration of 15 g VS/L and using a 1:1 mixing ratio (C/N ratio of 28.3). The co-digestion of SS/CM/MS performed better than the individual digestion of the components because of the balanced C/N ratios and supply of carbon. The optimum conditions for maximizing methane potential were an SS:CM:MS ratio of 30:35:35 and a bulk VS concentration of 15.0 g VS/L, which led to a maximum methane production of 8047.31 mL (C/N ratio of 12.7). The high-throughput sequencing analysis showed clear differences in microbial communities during the entire co-digestion process.

Adsorption behaviors of Cu2+, Zn2+ and Cd2+ onto proteins, humic acid, and polysaccharides extracted from sludge EPS: Sorption properties and mechanisms.

To clarify the adsorption behaviors of typical heavy metals onto sludge extracellular polymeric substances (EPS), the adsorption capacities and mechanisms, as well as the contributions of the different EPS components (proteins, humic acids and polysaccharides), to the adsorption of Zn2+, Cu2+ and Cd2+ were separately explored. Overall, proteins exhibited a relatively high adsorption capacity for the three metals ions, followed by humic acid, whereas least for polysaccharides. The adsorption of Cu2+ and Cd2+ onto proteins, humic acid and polysaccharides fit well to the Freundlich isotherm, whereas Langmuir model was the best fit for Zn2+ bindings onto polysaccharides/humic acid. The binding of Cu2+, Zn2+ and Cd2+ onto the three EPS components was exothermically favorable, and significant electrostatic interactions were observed for the heavy metals sorption onto humic acid and proteins. In addition, the effect of metal ions sorption on the spectrum of the proteins, polysaccharides and humic acid was also explored.

Adsorption mechanism of ZnO and CuO nanoparticles on two typical sludge EPS: Effect of nanoparticle diameter and fractional EPS polarity on binding.

Worldwide application of nanotechnology has led to an increasingly release of nanoparticles in wastewater treatment systems, and thus into sewage sludge, which potentially impairs the disposal of sewage sludge. Here, the binding process, adsorption characteristics, and the contribution of fractional polarity of extracellular polymeric substances (EPS) of anaerobic granular sludge (AGS) and activated sludge (AS) to the nano-ZnO and nano-CuO adsorption were investigated. Briefly, CuO-NPs can be more efficiently adsorbed by the EPS-AGS than that of ZnO-NPs (1.31 ±â€¯0.08 g/g VS vs 0.53 ±â€¯0.04 g/g VS), and a smaller diameter of nanoparticles benefited the adsorption processes. Hydrophobic EPS (HPO-A and HPO-N) within these two sludge were more effective in removing nano-CuO and ZnO than were the hydrophilic fraction. For example, HPO-A and HPO-N obtained from AGS showed a relatively higher adsorption abilities (in g/g VS) of 2.09 ±â€¯0.12 and 2.27 ±â€¯0.14, respectively, for nano-CuO, much higher than HPI (0.76 ±â€¯0.04 g/g VS). Structural variations of the EPS before and after nanoparticles sorption were evaluated via the analysis of infrared spectroscopy, which showed that the functional structures of hydroxyl, amino, carboxyl, amide groups and C-O-C groups played a major role in nanoparticles binding/removal. Sorption process of nano-CuO and nano-ZnO on unfractionated EPS well fitted by Langmuir isotherm, as well as a pseudo second-order kinetic model. However, adsorption process of HPO-A can be better simulated by Freundlich equation.