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Effects of Carbon-to-Nitrogen Ratio on Nitrogen and Phosphate Removal in A/O-MBR Wastewater Treatment Process

TAO Huchun, TONG Hao, WANG Jian, HUANG Yilong, ZHANG Lijuan, YANG Kai, DING Lingyun, QIAO Xuejiao, DOU Min, XU Nan

Acta Scientiarum Naturalium Universitatis Pekinensis 2022, 58 (4): 680-686. DOI: 10.13209/j.0479-8023.2022.037

Abstract （659）

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The changing profiles of NH4+-N, total nitrogen (TN) and total phosphate (TP) were investigated in the A/O-MBR process at high and low carbon-to-nitrogen ratios. By elevating the carbon-to-nitrogen ratio, there was an increase in the removal efficiency of TN from 44.1%±8.9% to 78.5%±7.9%, while the removal efficiency remained unchanged for TP. Metabolite analyses revealed that enhanced metabolism of amino acids contributed significantly to efficient nitrogen removal from wastewater and the up-regulation of riboflavin biosynthesis, further improving the water quality.

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A Study on the Electro-and-bioelectro-deposition of Heavy Metals in Municipal Solid Waste Incinerator Fly Ash

FENG Zhendong, LEI Tao, ZHANG Shanfa, ZHANG Lijuan, DING Lingyun, TAO Huchun

Acta Scientiarum Naturalium Universitatis Pekinensis 2022, 58 (4): 673-679. DOI: 10.13209/j.0479-8023.2022.034

Abstract （406）

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The contents and leaching concentrations of heavy metals from municipal solid waste incinerator (MSWI) fly ash were investigated in Shenzhen. Targeting at Cu, Pb and Zn as the key heavy metals, aqueous solutions containing Cu(II), Pb(II) and Zn(II) of 100 mg/L, 200 mg/L and 300 mg/L were synthesized to test the feasibility and efficiency of electro-and-bioelectro-deposition of heavy metals. In a bio-electrochemical system (BES), the removal and recovery efficiency of Cu(II) was >98%. In the subsequent electro-deposition reactor (ER), the concentrations of Pb(II) and Zn(II) were decreased from 200 and 300 mg/L to 23.5±1.1 and 4.3±0.2 mg/L with external voltage of 1.5 and 2.5 V, respectively. Energy consumption analysis revealed that extra electricity of 16.55 kWh was generated by 1 kg Cu(II) reduction in BES, while electricity of 60.91 kWh and 114.27 kWh were consumed by 1 kg Pb(II) and Zn(II) treatment in ER, and the heavy metal ions were reducted to free elements, oxides and salts. These results suggest that a combined BES and ER technology has advantages in metal recovery and energy saving.

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Metabolic Influence of Mercury Contamination on Bacterial Mercury Methylation by Geobacter sulfurreducens PCA

TAO Huchun, QIAN Lu, ZHANG Lijuan, DING Lingyun, FANG Fang, DAI Maifan, WEI Ruqian

Acta Scientiarum Naturalium Universitatis Pekinensis 2022, 58 (3): 526-536. DOI: 10.13209/j.0479-8023.2022.036

Abstract （465）

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Metabolomics, a rising omics approach, was employed to screen out cellular significantly differential metabolites and analyze related metabolic pathways in bacterial Hg-methylating process. Under the stress of Hg(II) at environmentally relevant concentrations (0?100 μg/L), the adsorbed/assimilated Hg(II) was utilized by Hg-methylator of Geobacter sulfurreducens PCA to reduce and methylate Hg(II). The highest efficiency of 3.09%± 0.16% was achieved for bacterial Hg-methylation upon exposure to 10 μg/L Hg(II). Metabolomics data showed that carbohydrate metabolism, amino acid metabolism and nucleotide metabolism were disturbed by Hg(II) stress in the PCA cells. To withstand the stress of Hg(II), G. sulfurreducens PCA increased energy demand for Hg methylation and DNA repair.

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Removal of Two Quinolone Antibiotics from Aqueous Solution by the Municipal Sewage Sludge-Based Adsorbent

TAO Huchun, GONG Yiwei, ZHANG Lijuan, DING Lingyun, ZHANG Shanfa

Acta Scientiarum Naturalium Universitatis Pekinensis 2021, 57 (4): 765-772. DOI: 10.13209/j.0479-8023.2021.060

Abstract （831）

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The municipal sewage sludge was used as an raw material to prepare the sewage sludge-based adsorbent (SSA) by HNO₃ activation, NaOH activation and H₂O₂ oxidation modification. The removal of ciprofloxacin (CIP) and lomefloxacin (LOM) from aqueous solution and the influencing factors were studied. Scanning electron microscopy and Fourier transform infrared spectroscopy were used to characterize the microstructure and functional groups on the surface of SSA. The effects of adsorbent dosage, temperature, the initial pH of solution, the ionic strength and other factors on the removal of CIP and LOM by SSA were investigated. The results showed that the modified SSA activated by 0.1 M HNO₃ was most effective for removal of CIP and LOM. The rough structure of the modified adsorbent could provide more sites for antibiotic adsorption, and the oxygen-containing functional groups were able to form hydrogen bonds to enhance the adsorption of organic matters in solution. When the antibiotic concentration was 10 mg/L, the adsorption capacity of CIP and LOM was 8.95 and 7.28 mg/g, and removal rates were 90% and 73%, respectively. The adsorption process of CIP and LOM on the modified SSA was in accordance with the pseudo-second-order model, and Langmuir isotherm equation could well describe the adsorption behavior of CIP and LON on the modified SSA, which proved that adsorption process was monolayer chemisorption. The adsorbent removed 84% CIP and 67% LOM after 5 cycles, thus providing an efficient and sustainable way of antibiotic removal.

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Growth Conditions of a Hydrogen-Oxidizing Bacterium and Its Utilization of Different Nitrogen Sources

TAO Huchun, XIE Yong, ZHANG Lijuan, DING Lingyun, CHEN Yizhen

Acta Scientiarum Naturalium Universitatis Pekinensis 2021, 57 (4): 756-764. DOI: 10.13209/j.0479-8023.2021.059

Abstract （726）

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An autotrophic hydrogen-oxidizing bacterium, named Rhodoblastus sp. TH20, was successfully enriched and isolated from municipal activated sludge in a domestic wastewater treatment plant. With simulated ammonium-containing wastewater as culture medium, the strain could utilize H₂ and CO₂ as energy and carbon sources respectively and the growth conditions were optimized at 25℃, 160 rpm and pH=7.0. At initial concentration of 100 mg/L, efficient ammonium removal (>99%) was achieved within 72 hours. Up to 77.8% of ammonium was assimilated to organic nitrogen and stored intracellularly, while the rest ammonium was transformed to gaseous N₂. These results indicated that Rhodoblastus sp. TH20 was able to efficiently convert ammonium into microbial protein, thereby providing a sustainable pathway of wastewater treatment.

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Photocatalytic Degradation of Ciprofloxacin by Magnetic CoFe₂O₄/g-C₃N₄ Nanocomposites

TAO Huchun, DENG Liping, ZHANG Lijuan, DING Lingyun

Acta Scientiarum Naturalium Universitatis Pekinensis 2021, 57 (3): 587-594. DOI: 10.13209/j.0479-8023.2021.037

Abstract （707）

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Magnetic CoFe₂O₄/g-C₃N₄ nanocomposites were synthesized and its surface morphology, element and chemical composition, specific surface area, functional group characteristics and crystal structure were characterized. Targeting at quinolone antibiotics of ciprofloxacin (CIP), the photo-catalytic degradation of CIP by CoFe₂O₄/g-C₃N₄ nanocomposites was investigated at different calcination temperature (300^oC, 400^oC and 500^oC) and composite ratio (CoFe₂O₄:g-C₃N₄=10%, 20% and 40%, w/w). Under optimal synthesis and operating conditions, a maximum degradation efficiency of 75.1 ± 0.1% was achieved for 0.9 g/L CoFe₂O₄/g-C₃N₄ with 10 mg/L CIP (pH=6.6) within 120 min. With an external magnetic field, the CoFe₂O₄/g-C₃N₄ nanocomposites were easily and rapidly recycled, remaining >90% of the initial efficacy after 5 cycles and showing a considerable stability. Fluorescence spectra revealed a significant decrease in electron-hole recombination rates under light radiation, which contributed greatly to the increase of photo-degradation efficacy of CIP by CoFe₂O₄/g-C₃N₄nanocomposites.

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Study on the Catalytic Oxidation of Rhodamine B by Nanoporous Carbon Materials Loaded with Zero Valence Copper

WANG Aide, FENG Zhendong, QIN Dayu, ZHANG Lijuan, ZHU Lili, ZHANG Shanfa, TAO Huchun

Acta Scientiarum Naturalium Universitatis Pekinensis 2020, 56 (4): 703-709. DOI: 10.13209/j.0479-8023.2020.033

Abstract （1140）

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Nanoporous carbon material loaded with zero-valent copper NPC@Cu was synthesized by one-step carbonization method using copper-based MOF (HKUST-1, [Cu₃(BTC)₂], BTC as 1,3,5-benzenetricarboxylic acid) as template. With NPC@Cu as catalyst, peroxymonosulfatesulfate (PMS) was activated as oxidant to treat simulated azo dye wastewater by heterogeneous catalytic oxidation at ambient pressure and room temperature. The catalysts were characterized by electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), etc. The effect of degradation efficiency of the catalyst dosage, oxidant dosage and initial pH during the reaction were studied. The experimental results showed that the degradation rate of 0.10 mmol/L RhB can reach 100% after 45 minutes of reaction at a catalyst dosage of 0.1 g/L, a PMS concentration of 2.00 mmol/L and a initial pH of 7. Through the free radical trapping experiment, it proved that there are two free radicals in the system—SO₄^–·and ·OH, and NPC@Cu is a catalytic material with good catalytic performance.

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Preparation of Magnetic g-C₃N₄-Fe₃O₄ Nanocomposites and the Photocatalytic Degradation of Three Quinolones in Aqueous Solution

TAO Huchun, LIANG Hongfei, ZHANG Lijuan, DING Lingyun, ZHANG Shanfa, ZHU Lili, DENG Liping

Acta Scientiarum Naturalium Universitatis Pekinensis 2020, 56 (3): 546-552. DOI: 10.13209/j.0479-8023.2020.026

Abstract （632）

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Magnetic g-C₃N₄-Fe₃O₄ nanomaterials were prepared by using melamine and iron salts as raw materials, and the effects of different operating factors on the photocatalytic degradation of three quinolone antibiotics were investigated. The optimal conditions for the photocatalytic reactions were: initial antibiotic concentration of 3.0 mg/L, initial g-C₃N₄-Fe₃O₄ dose of 0.60 g/L, at 25℃, and pH=7. Under optimized conditions, the degradation efficiencies of Lomefloxacin, Ofloxacin and Ciprofloxacin were 83.6%, 60.9% and 99.0% after 100 min light irradiation, respectively. XRD and UV-vis analyses show that the graphite-phase g-C₃N₄ has strong interaction with magnetic Fe₃O₄, resulting in the formation of more photogenerated electron-hole pairs and enhancing the photocatalytic activity of the composite nanomaterials. After repeated recycling for 5 times, there are more than 90% of magnetic g-C₃N₄-Fe₃O₄ nanomaterials recovered, and the photocatalytic efficiency is maintained at higher than 60%.

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Study on the Effect of Two Red-Tide Algae on Mercury Biocondensation and Methylation

TAO Huchun, YANG Sai, DING Lingyun, ZHANG Lijuan, HE Ningning, ZHANG Yaoyu

Acta Scientiarum Naturalium Universitatis Pekinensis 2019, 55 (4): 709-716. DOI: 10.13209/j.0479-8023.2019.047

Abstract （746）

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The effect of two red-tide algae of Alexandrium tamarens and Scrippsiella trochoidea on mercury (Hg) adsorption and methylation were investigated. The inhibitory effect of two algae on biomethylation of Geobacter Sulfurreducens (G. sulfurreducens) PCA were demonstrated. The growth of Scrippsiella trochoidea was inhibited under exposure to high concentration of HgCl₂ (≥25 μg/L), but less affecting Alexandrium tamarens. Significant adsorption of Hg²⁺ was observed onto algal cells, whilst negligible amount of methylmercury (MeHg) was produced by two algae directly. FTIR spectra revealed that hydroxyl, carboxyl and amino groups were major binding sites for Hg²⁺ adsorption. In Hg-algae-bacteria tests, at initial HgCl₂ concentration of 10 μg/L, a maximum mercury methylation efficiency of (6.38±0.4)% was obtained by pure G. sulfurreducens PCA culture as a control, but the efficiency reduced to (1.04±0.44)% with G. sulfurreducens PCA and Alexandrium tamarens coexisting, and a much lower efficiency of (0.76±0.05)% was detected with G. sulfurreducens PCA and Scrippsiella trochoidea coexisting. These results suggested that two red-tide algae inhibited mercury biomethylation of G. sulfurreducens PCA.

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Thio-Aminopropyltriethoxysilane-Modified Porous Glass-Ceramics as New Sorbents for Palladium (II) Separation from Wastewater

TAO Huchun, HUANG Shuaibin, GU Yihan, ZHANG Lijuan, ZHU Lili

Acta Scientiarum Naturalium Universitatis Pekinensis 2019, 55 (2): 360-366. DOI: 10.13209/j.0479-8023.2018.100

Abstract （673）

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Thio-aminopropyltriethoxysilane-modified porous glass-ceramics (TAMPG) were prepared through reuse of waste glass for efficient palladium (II) separation from wastewater. Novel TAMPG-1, TAMPG-2, TAMPG-3 were obtained by immobilizing organic ligands 2-thiophene formaldehyde, 2-mercaptobenzimidazoles and 2-mercaptobenzothiazole onto the surface of porous glass-ceramics made from waste glass. Optimal conditions for effective palladium (II) adsorption were investigated with respect to pH, temperature, initial concentration and contact time. Owing to cheap raw materials, good adsorption properties, great recycling potential, excellent selectivity and stability, an economically viable method was proposed for efficient palladium (II) separation from wastewater.

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Preparation and Optimization of a Novel Magnetic Chitosan/Sodium Alginate Composite Gel Bead

TAO Huchun, LI Shuo, ZHANG Lijuan, LI Jinbo, YANG Sai

Acta Scientiarum Naturalium Universitatis Pekinensis 2018, 54 (4): 899-906. DOI: 10.13209/j.0479-8023.2017.186

Abstract （795）

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Using sodium alginate hydrogel as skeleton, in combination with chitosan and magnetic Fe₃O₄, a new type of magnetic chitosan/sodium alginate gel bead was prepared. On this basis, through the orthogonal experiment and single-factor experiment, the authors optimized the preparation conditions for composite gel bead, and determined the optimum one. The influences of many preparation impact factors on adsorption performance were examined. Results show that the optimal preparation conditions for the composite gel bead is as follows. Concentration of calcium chloride is 2.5 g/L, concentration of sodium alginate is 24 g/L, the amount of chitosan addition is 5 g/L, and the amount of magnetic liquid addition is 4.64 g/L. The optimal gel bead is a smooth, uniform, black ball with about 2 mm in diameter. By Fourier transform infrared spectroscopy (FTIR), synchronous thermal analysis (TGA) and other means of characterization, the adsorption mechanism is analyzed. Thermogravimetric analysis results show that the gel bead has good thermal stability. FTIR results prove that many active functional groups (amino group, hydroxyl group and carboxyl group) exist on the surface of gel bead. The adsorption performance test shows that adsorption ratio of 20mg MCSB on 40mL 25mg/L Cu²⁺ solution is 78.13%. The magnetic chitosan/sodium alginate gel bead is a novel simple-prepared and effective composite adsorbent.

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