Biochar enhanced the stability and microbial metabolic activity of aerobic denitrification system under long-term oxytetracycline stress

Response of aerobic denitrification system to long-term stress of sulfamethoxazole, erythromycin and ofloxacin in oligotrophic water

The responses of aerobic denitrification system to long-term stress of sulfamethoxazole (SMX), erythromycin (ERY) and ofloxacin (OFL) were investigated under low, middle, and high antibiotics stress. Findings showed that the aerobic denitrification performance was enhanced by antibiotics, and was higher than control system. Meanwhile, nitrate removal efficiency reached 43.01 ∼ 53.82 %, 29.48 ∼ 47.83 %, and 19.53 ∼ 34.08 % from low to high antibiotics stress in low carbon/nitrogen (C/N) ratio water. The α-diversity (ACE, Chao, and Shannon index) tended to increase for middle and high antibiotic stress. The PCoA and NMDS indicated that communities exhibited significantly difference (P < 0.001) under different antibiotics stress, which were agreement with the results of Adonis and ANOSIM. Acidovorax, Zoogloea, Bdellovibrio, Paracoccus, Piscinibacter, Pseudomonas, and Rhizobacter dominated the aerobic denitrification bacteria. Moreover, stochastic processes decreased gradually with increasing antibiotics. Furthermore, the results of network demonstrated that increase of antibiotics concentration could obviously reduce the microbial stability.

Metagenomics deciphers the function of biochar in alleviating zinc ion stress during sulfur autotrophic denitrification process

Sulfur autotrophic denitrification (SAD) process has significant potential in treating low carbon/nitrogen ratio wastewater. However, the presence of zinc ions (Zn2+) adversely affects the denitrification performance. This study investigated the effect of biochar prepared at 300 °C (BC300) and 600 °C (BC600), as well as dosing strategy, on denitrification performance in the SAD process under Zn2+ inhibition. Firstly, BC600 had a higher maximum adsorption capacity for Zn2+ than BC300 in nitrogen-containing wastewater. Surface complexation was mainly adsorption mechanism. BC300 exhibited a greater ability in enhancing denitrification ability than BC600. The strategy of synchronous addition is more effective than pre-adsorption. Firstly, BC300 enhancing humic-like component secretion. BC300 enriched higher abundance of sulfur-oxidizing bacteria. More importantly, BC300 counteracted the negative effect of Zn2+ by enhancing glycan biosynthesis and metabolism, enriching functional genes, and increased the level of quorum sensing. The study presents a sustainable approach for maintaining denitrification performance under environmental stress.

Response and self-regulation of PD/A granular sludge to oxytetracycline stress

This paper investigated the operational characteristics and self-regulation mechanism of the partial denitrification/anammox (PD/A) granular system under the stress of oxytetracycline (OTC), an emerging pollutant that accumulates in municipal wastewater treatment plants through various pathways, posing significant challenges for its future promotion in engineering applications. The results indicated that OTC concentrations below 100 mg/L intensified its short-term inhibition on the PD/A granular sludge system, decreasing functional bacterial activity, while between 150 and 300 mg/L, PD's NO3--N to NO2--N conversion ability diminished, and Anammox activity was significantly suppressed. Under long-term high OTC stress (20-30 mg/L), nitrogen removal suffered, and batch tests revealed significant inhibition of PD's NO3--N to NO2--N conversion, dropping from 73.77 % to 50.17 %. Anammox bacteria activity sharply declined from 1.81 to 0.39 mg N/gVSS/h under OTC stress. Extracellular polymeric substances (EPS) content rose from 185.39 to 210.86 mg/gVSS, indicating PD/A sludge's self-protection mechanism. However, EPS content fell due to cell lysis at high OTC (30 mg/L). The decreasing relative abundance of Candidatus_Brocadia (2.32 % to 0.93 %) and Thaure (12.63 % to 7.82 %) was a key factor in the gradual deterioration of denitrification performance. This study was expected to provide guidance for the PD/A process to cope with the interference of antibiotics and other emerging pollutants (short-term shock and long-term stress).

Simultaneous removal of nitrate, oxytetracycline and copper by ferrous-manganese co-driven immobilized bioreactor

The treatment of polluted water contaminated by nitrate, antibiotics, and heavy metals is a difficult problem in the current water treatment process. In this study, MnFe2O4 modified illite was mixed with sodium alginate (SA) to prepare a biological carrier illite@MnFe2O4@SA (IMFSA), which was used to immobilize strain Zoogloea sp. MFQ7 and construct a bioreactor. The bioreactor can use sodium acetate as a carbon source as well as ferrous and manganese ions as additional electron donors to achieve efficient nitrate removal. The denitrification capability of bioreactor was considerably enhanced by the addition of illite@MnFe2O4 (IMF) in comparison to SA biological carrier. The bioreactor was able to achieve a nitrate removal efficiency of 97.2% when hydraulic retention time is 5.0 h, C/N ratio is 2.0, and the concentration of Fe2+ and Mn2+ were 5.0 mg L-1. Furthermore, the bioreactor can achieve efficient removal of oxytetracycline (91.8%) and copper (85.6%) through the adsorption by IMF and biological iron-manganese precipitates. High-throughput sequencing results indicated that Zoogloea was successfully immobilized into the biocarrier. According to the KEGG database, it is suggested that the addition of modified IMF enhances denitrification and stimulates the expression of genes associated with the iron-manganese redox cycle.

Enhanced nitrate removal efficiency and microbial response of immobilized mixed aerobic denitrifying bacteria through biochar coupled with inorganic electron donors in oligotrophic water

The nitrogen removal characteristics and microbial response of biochar-immobilized mixed aerobic denitrifying bacteria (BIADB) were investigated at 25 °C and 10 °C. BIADB removed 53.51 ± 1.72 % (25 °C) and 39.90 ± 4.28 % (10 °C) nitrate in synthetic oligotrophic water. Even with practical oligotrophic water, BIADB still effectively removed 47.66-53.21 % (25 °C), and 39.26-45.63 % (10 °C) nitrate. The addition of inorganic electron donors increased nitrate removal by approximately 20 % for synthetic and practical water. Bacterial and functional communities exhibited significant temperature and stage differences (P < 0.05), with temperature and total dissolved nitrogen being the main environmental factors. The dominant genera and keystone taxa exhibited significant differences at the two temperatures. Structural equation model analysis showed that dissolved organic matter had the highest direct and indirect effects on diversity and function, respectively. This study provides an innovative pathway for utilizing biochar and inorganic electron donors for nitrate removal from oligotrophic waters.

Comprehensive review on recent production trends and applications of biochar for greener environment

The suitability of biochar as a supplement for environmental restoration varies significantly based on the type of feedstocks used and the parameters of the pyrolysis process. This study comprehensively examines several aspects of biochar's potential benefits, its capacity to enhance crop yields, improve nutrient availability, support the co-composting, water restoration and enhance overall usage efficiency. The supporting mechanistic evidence for these claims is also evaluated. Additionally, the analysis identifies various gaps in research and proposes potential directions for further exploration to enhance the understanding of biochar application. As a mutually advantageous approach, the integration of biochar into agricultural contexts not only contributes to environmental restoration but also advances ecological sustainability. The in-depth review underscores the diverse suitability of biochar as a supplement for environmental restoration, contingent upon the specific feedstock sources and pyrolysis conditions used. However, concerns have been raised regarding potential impacts on human health within agricultural sectors.