Removal performance and inhibitory effects of combined tetracycline, oxytetracycline, sulfadiazine, and norfloxacin on anaerobic digestion process treating swine manure

Effects of Hydrothermal Pretreatment and Anaerobic Digestion of Pig Manure on the Antibiotic Removal and Methane Production

Whether advanced biological waste treatment technologies, such as hydrothermal pretreatment (HTP) integrated anaerobic digestion (AD), could enhance the removal of different antibiotics remains unclear. This study investigated the outcome of antibiotics and methane productivity during pig manure treatment via HTP, AD, and HTP + AD. Results showed improved removal efficiency of sulfadiazine (SDZ), oxytetracycline (OTC), and enrofloxacin (ENR) with increased HTP temperatures (70, 90, 120, 150, and 170 °C). OTC achieved the highest removal efficiency of 86.8% at 170 °C because of its high sensitivity to heat treatment. For AD, SDZ exhibited resistance with a removal efficiency of 52.8%. However, OTC and ENR could be removed completely within 30 days. When HTP was used prior to AD, OTC and ENR could achieve complete removal. However, residual SDZ levels reduced to 20% and 16% at 150 and 170 °C, respectively. The methanogenic potential showed an overall upward trend as the HTP temperature increased. Microbial analysis revealed the antibiotics-induced enrichment of specific microorganisms during AD. Firmicutes were the dominant bacterial phylum, with their abundance positively correlated with the addition of antibiotics. Methanobacterium and Methanosarcina emerged as the dominant archaea that drove methane production during AD. Thus, HTP can be a potential pretreatment before AD to reduce antibiotic-related risks in manure waste handling.

Magnetization and ZIF-67 modification of Aspergillus flavus biomass for tetracycline removal from aqueous solutions: A stable and efficient composite

In the present work, the biomass of Aspergillus flavus (AF) was modified using magnetic nanoparticles MnFe2O4 and metal-organic framework of ZIF-67, and its ability to remove tetracycline antibiotic (TCH) was investigated. With the help of physicochemical tests, AF biomass modification with ZIF-67 and MnFe2O4 magnetic nanoparticles was confirmed. Based on the BET value, AF-MnFe2O4-ZIF-67 (139.83 m2/g) has a higher surface value than AF (0.786 m2/g) and AF/MnFe2O4 (17.504 m2/g). Also, the magnetic saturation value revealed that the modified biomass can be isolated from the treated solution using a simple magnetic field. Maximum TCH elimination (99.04%) using AF-MnFe2O4-ZIF-67 was obtained at pH 7, adsorber mass of 1 g/L, adsorption time of 40 min, and TCH content of 10 mg/L. The thermodynamic study indicated that the TCH abatement using the desired composite is spontaneous and exothermic. The experimental results showed that the adsorption process is compatible with the pseudo-second-order kinetic and Freundlich model. The maximum adsorption capacity for AF, AF-MnFe2O4, and AF-MnFe2O4-ZIF-67 was quantified to be 9.75 mg/g, 25.59 mg/g, and 43.87 mg/g, respectively. The reusability of the desired adsorbers was examined in up to 8 steps. The outcomes showed that the adsorbers can be used several times in TCH elimination. The provided composite can remove TCH from hospital wastewater, so it can be suggested for use in water and wastewater treatment works.

Generic role of zeolite in enhancing anaerobic digestion and mitigating diverse inhibitions: Insights from degradation performance and microbial characteristics

Zeolite was shown to mitigate anaerobic digestion (AD) inhibition caused by several inhibitors such as long-chain fatty acids, ammonia, and phenolic compounds. In this paper, we verified the genericity of zeolite's mitigating effect against other types of inhibitors found in AD such as salts, antibiotics, and pesticides. The impacts of inhibitors and zeolite were assessed on AD performance and microbial dynamics. While sodium chloride and erythromycin reduced methane production rates by 34% and 32%, zeolite mitigated the inhibition and increased methane production rates by 72% and 75%, respectively, compared to conditions without zeolite in the presence of these two inhibitors. Noticeably, zeolite also enhanced methane production rate by 51% in the uninhibited control condition. Microbial community structure was analyzed at two representative dates corresponding to the hydrolysis/fermentation and methanogenesis stages through 16S rRNA gene sequencing. The microbial characteristics were further evidenced with common components analysis. Results revealed that sodium chloride and erythromycin inhibited AD by targeting distinct microbial populations, with more pronounced inhibitory effects during hydrolysis and VFAs degradation phases, respectively. Zeolite exhibited a generic effect on microbial populations in different degradation stages across all experimental conditions, ultimately contributing to the enhanced AD performance and mitigation of different inhibitions. Typically, hydrolytic and fermentative bacteria such as Cellulosilyticum, Sedimentibacter, and Clostridium sensu stricto 17, VFAs degraders such as Mesotoga, Syntrophomonas, and Syntrophobacter, and methanogens including Methanobacterium, Methanoculleus, and Methanosarcina were strongly favored by the presence of zeolite. These findings highlighted the promising use of zeolite in AD processes for inhibition mitigation in general.

Three-dimensional porous La(OH)3/g-C3N4 adsorption-photocatalytic synergistic removal of tetracycline

La(OH)3/g-C3N4 composites were successfully synthesized via one-step calcination using urea, melamine, and La(NO3)3·nH2O as raw materials, and applied to UV-induced photocatalytic tetracycline (TC) removal. Comprehensive characterization by an X-ray diffraction (XRD), Fourier transform infrared reflection (FT-IR), high-resolution transmission electron microscope (HRTEM), and other techniques analyzed effects of La3+ doping, especially N vacancies and cyano groups as active sites. Compared to pure g-C3N4 and La(OH)3, synthesized La(OH)3/g-C3N4 composites exhibited a three-dimensional porous nanosheet structure with specific surface area of 83.62 m2/g and equilibrium TC adsorption capacity up to 285.59 mg/g; La(OH)3 doping significantly improved composite structure. After dispersing 10 mg La-CN-0.5 photocatalyst in 60 mL 40 mg/L TC solution, TC removal reached 91.08% in 30 min under UV irradiation, exhibiting excellent performance. Additionally, La-CN-0.5 showed significant adsorption-photocatalytic synergism, with the quasi-primary kinetic constant increased by 1.83-fold. The efficiency of high tetracycline (TC) concentration treatment through adsorption photocatalytic degradation by La-CN-0.5 was confirmed by the utilization of free radical trapping and electron spin resonance (ESR) tests. The significant involvement of ∙O2-, ∙OH, and h+ in this process was observed. These findings propose that the prepared La-CN-0.5 material exhibits a unique capability for adsorption photocatalysis, providing a promising approach for the efficient removal of high TC concentrations.

Effects of environmentally relevant concentrations of oxytetracycline and sulfadiazine on the bacterial communities, antibiotic resistance genes, and functional genes are different between maize rhizosphere and bulk soil

Antibiotic contamination in soil has become a major concern worldwide. At present, it is not clear how two co-existed antibiotics with environmentally relevant concentrations would affect soil bacterial community structure, the abundances of antibiotic resistance genes (ARGs) and functional genes, and whether the effects of antibiotics would differ between rhizosphere and bulk soil. We conducted a greenhouse pot experiment to grow maize in a loess soil treated with oxytetracycline (OTC) or sulfadiazine (SDZ) or both at an environmentally relevant concentration (1 mg kg-1) to investigate the effects of OTC and SDZ on the rhizosphere and bulk soil bacterial communities, abundances of ARGs and carbon (C)-, nitrogen (N)-, and phosphorus (P)-cycling functional genes, and on plant growth and plant N and P nutrition. The results show that the effects of environmentally relevant concentrations of OTC and SDZ on bacterial communities and abundances of ARGs and functional genes differ between maize rhizosphere and bulk soil. The effects of two antibiotics resulted in a higher absolute abundances of accA, tet(34), tnpA-04, and sul2 in the rhizosphere soil than in the bulk soil and different bacterial community compositions and biomarkers in the rhizosphere soil and the bulk soil. However, OTC had a stronger inhibitory effect on the abundances of a few functional genes in the bulk soil than SDZ did, and their combination had no synergistic effect on plant growth, ARGs, and functional genes. The role of co-existed OTC and SDZ decreased shoot height and increased root N concentration. The results demonstrate that environmentally relevant concentrations of antibiotics shift soil microbial community structure, increase the abundances of ARGs, and reduce the abundances of functional genes. Furthermore, soil contamination with antibiotics can diminish agricultural production via phytotoxic effects on crops, and combined effects of antibiotics on plant growth and nutrient uptake should be considered.

Enhancing anaerobic digestion performance of oxytetracycline-laden wastewater through micro-nano bubble ozonation pretreatment

This study investigated the potential of micro-nano bubble (MNB) ozonation pretreatment to eliminate oxytetracycline (OTC) from wastewater and improve subsequent anaerobic digestion (AD) performance. The findings revealed that MNB ozonation achieved efficient OTC oxidation (>99 % in 60 min), and significantly enhanced methane production by 51 % compared to conventional ozonation (under 30 min of pretreatment). Additionally, MNB ozonation resulted in a decrease in the soluble chemical oxygen demand and reduced volatile fatty acid accumulation compared to conventional ozonation. Furthermore, the study sheds light on the profound impact of OTC and its oxidation by-products on the sludge microbiome. Exposure to OTC and its oxidation by-products resulted in alterations in extracellular polymeric substances composition and led to significant shifts in microbial community structure. This study highlights the promise of MNB ozonation as an effective approach for pharmaceutical pollutant removal and the optimization of AD performance in wastewater treatment, with implications for improved environmental sustainability.

Effect of antibiotics on the performance of moving bed biofilm reactor for simultaneous removal of nitrogen, phosphorus and copper(II) from aquaculture wastewater

Co-existence of NO3--N, antibiotics, phosphorus (P), and Cu2+ in aquaculture wastewater has been frequently detected, but simultaneous removal and relationship between enzyme and pollutants removal are far from satisfactory. In this study, simultaneous removal of NO3--N, P, antibiotics, and Cu2+ by moving bed biofilm reactor (MBBR) was established. About 95.51 ± 3.40% of NO3--N, 61.24 ± 3.51% of COD, 18.74 ± 1.05% of TP, 88% of Cu2+ were removed synchronously in stage I, and antibiotics removal in stages I-IV was 73.00 ± 1.32%, 79.53 ± 0.88%, 51.07 ± 3.99%, and 33.59 ± 2.73% for tetracycline (TEC), oxytetracycline (OTC), chlortetracycline hydrochloride (CTC), sulfamethoxazole (SMX), respectively. The removal kinetics and toxicity of MBBR effluent were examined, indicating that the first order kinetic model could better reflect the removal of NO3--N, TN, and antibiotics. Co-existence of multiple antibiotics and Cu2+ was the most toxicity to E. coli growth. Key enzyme activity, reactive oxygen species (ROS) level, and its relationship with TN removal were investigated. The results showed that enzymes activities were significantly different under the co-existence of antibiotics and Cu2+. Meanwhile, different components of biofilm were extracted and separated, and enzymatic and non-enzymatic effects of biofilm were evaluated. The results showed that 70.00%- 94.73% of Cu2+ was removed by extracellular enzyme in stages I-V, and Cu2+ removal was mainly due to the action of extracellular enzyme. Additionally, microbial community of biofilm was assessed, showing that Proteobacteria, Bacteroidetes, and Gemmatimonadetes played an important role in the removal of NO3--N, Cu2+, and antibiotics at the phylum level. Finally, chemical bonds of attached and detached biofilm were characterized by X-ray photoelectron spectroscopy (XPS), and effect of nitrogen (N) and P was proposed under the co-existence of antibiotics and Cu2+. This study provides a theoretical basis for further exploring the bioremediation of NO3--N, Cu2+, and antibiotics in aquaculture wastewater.