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Nitrogen plays a central role in the sewer ecosystem, and the bioconversion of nitrogen can significantly affect bioreactions in sewers. However, the mechanisms underlying the involvement of nitrogen-associated pollutants in sewer ecosystems remain unknown. In this study, the effects of two typical nitrogen ratios (organic/inorganic nitrogen: 7/3 (Group A) and 3/7 (Group B)) on carbon, nitrogen, and sulfur bioconversions were investigated in a pilot sewer. The distribution of amino acids, such as proline, glycine and methionine, was significantly different between Groups A and B, and carbon-associated communities (based on 16S rRNA gene copies) were more prevalent in Group A, while sulfur and nitrogen-associated communities were more prevalent in Group B. To explore the effect of nitrogen on microbial response mechanisms, metagenomics-based methods were used to investigate the roles of amino acids involved in carbon, nitrogen, and sulfur bioconversion in sewers. Proline, glycine, and tyrosine in Group A promoted the expression of genes associated with cell membrane transport and increased the rate of protein synthesis, which stimulated the enrichment of carbon-associated communities. The transmembrane transport of higher concentrations of alanine and methionine in Group B was essential for cell metabolism and nutrient transport, thereby enriching nitrogen and sulfur-associated communities. In this investigation, insights into carbon, nitrogen and sulfur bioconversions in sewer ecosystems were revealed, significantly improving the understanding of the sewer ecosystem within a community context., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In this study, a novel TiO 2-x /rGO-PS-Vis process was developed, which utilizes the TiO 2-x /rGO (Ti 3+ and oxygen vacancies self-doped TiO 2 coupled with reduced graphene oxide) nanocomposite as a promising and efficient activator of persulfate (PS) for the enhanced oxidation of micropollutants under visible -light irradiation. TiO 2-x /rGO exhibited a significantly high activity for PS activation to produce more sulfate radicals (SO 4 - ) and hydroxyl radicals (OH). Therefore, almost 100% BPA (10 mg/L) and 80% TOC can be removed just within 12 min with 1.0 g/L TiO 2-x /rGO and 2 mM PS under visible light. Moreover, it was found that many other typical micropollutants, such as phenol, acetaminophen and sulfamethoxazole can also be effectively degraded by this process. Electron paramagnetic resonance (EPR) and radical quenching experiments indicated that both SO 4 - and OH contribute to the degradation of organics, and the radical process was the main degradation pathway. In addition, the effects of PS concentration, catalyst dosage, initial solution pH and inorganic anions were investigated systematically. Experiments carried out in the real background of water matrix with low-concentration of BPA indicated that the proposed TiO 2-x /rGO-PS-Vis process has strong non-selective photo-oxidative ability for the removal of micropollutants in water., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Using a microscopic technique, the dynamic properties of Al-humic flocs were studied and the regularity of the variation of floc structure, i.e. fractal dimension, was discussed. The results show that during coagulation floc size increased with agitation time and finally reached an equilibrium state. As flocs grow their structure gradually become looser with an increase of void ratio, and results in a substantial decrease of their fractal dimension from the initial value of 1.8 to about 1.4. There exist an exponential relation between the fractal dimension Df and the floc size df as Df = Adf-n. It was explained by theoretical analysis that the decrease of Df with increase of df as was the result of random collision and agglomeration of primary particles. The alum dosage directly affected the rate of floc growth and its equilibrium size. Overdosing may bring about an apparent decrease of the fractal dimension of the flocs.