[Metagenomic Analysis of Resistance Genes in Membrane Cleaning Sludge].

Wastewater treatment plants (WWTPs) are considered important reservoirs of antibiotic resistance genes (ARGs) and function as the main sources of ARGs in the environment. Membrane bioreactors (MBRs) have been recognized as effective tools for removing ARGs in WWTPs.There are a large number of pathogens and resistance genes in colloids, particulate matter, suspended matter, and microbial metabolites in intercepted wastewater by MBR. However, the distribution characteristics of resistance genes in membrane cleaning sludge remains unclear. In this study, resistance genes of membrane cleaning sludge were analyzed using a metagenomic technique. The results showed that there were 39 phyla in the membrane cleaning sludge. Proteobacteria, Nitrospirae, and Actinobacteria were the dominant phyla. The dominant genera were Nitrospira, Pseudomonas, and Bradyrhizobium. The pathogens accounted for 10.54% of all bacteria in the sample, among which Pseudomonas had the highest abundance, accounting for 3.94%. A total of 17 types of antibiotic resistance genes and 16 types of metal resistance genes (MRGs) (15 types of single metal resistance genes and 1 types of multi-heavy metal resistance gene) were identified. Multidrug resistance genes had the highest abundance, accounting for 49.08%. Multi-heavy metal resistance genes were the most abundant, accounting for 34.58%. The copper resistance genes were the most abundant of the single metal resistance genes, accounting for 19.99%. The most important functional pathway of microbial community in the membrane cleaning sludge was metabolic related, and many genes identified were related to human diseases. The numbers of genes related to bacterial resistance and bacterial infectious diseases were the largest, accounting for 34.50% and 16.62%, respectively. These results indicate that there were abundant ARGs, MRGs, and pathogens in the membrane cleaning sludge, which has potential environmental health risks. It is necessary to strengthen the control of ARGs, MRGs, and pathogens in membrane cleaning sludge to provide guidance for selecting appropriate technologies for effectively removing ARGs, MRGs, and pathogens.

Spectroscopic characterization of DOM and the nitrogen removal mechanism during wastewater reclamation plant.

The performance of the Sha-he wastewater reclamation plant was evaluated in this study. To remove residual nitrogen after Anaerobic-Anoxic-Oxic (A2O) treatment, three multistage Anoxic-Oxic (A/O) were added to investigate the nitrogen removal efficiency and its mechanism. In addition, the constituents and evolution of dissolved organic matter (DOM) during wastewater reclamation was also investigated using a method combining fluorescence spectroscopy with fluorescence regional integration (FRI). The results suggested that multistage A/O treatment can effectively improve the nitrogen removal ability under low concentrations of carbon sources. The total nitrogen (TN) exhibits significantly positive correlation with fulvic acid-like materials and humic acid-like materials. The correlation coefficient for TN and fulvic acid-like substances (R2 = 0.810, P < 0.01) removal was greater than that of humic acid-like substances (R2 = 0.636, P < 0.05). The results indicate that nitrogen removal may be achieved with the fulvic-like and humic-like substances, and the removal effects were higher by fulvic acid-like substances than humic-like substances, mostly due to that the latter were relatively more difficult to be utilized as carbon source during the nitrogen removal process. The effluent water quality of biological treatment reached the first grade A standard of "Cities sewage treatment plant pollutant discharge standard" (GB18918-2002). In addition, the effluent from the membrane bioreactor reached the "Standards of reclaimed water quality" (SL368-2006).

[GIS Spatial Distribution and Ecological Risk Assessment of Heavy Metals in Surface Sediments of Shallow Lakes in Jiangsu Province].

To understand pollution of heavy metals in surface sediments of shallow lakes, surface sediments samples of 11 lakes in Jiangsu province were collected to determine the content of six heavy metals including As, Cr, Cu, Pb, Zn and Ni. GIS was used to analyze the spatial distribution of heavy metals, and geological accumulation index (Igeo), modified contamination index (mCd) pollution load index (PLI) and potential ecological risk index (RI) were used to evaluate heavy metal contamination in the sediments. The results showed that: in the lakes' surface sediments, the average content of As, Cu, Zn, Cr, Pb, Ni in multiples of soil background of Jiangsu province were 1.74-3.85, 0.65-2.66, 0.48-3.56, 0.43-1.52, 0.02-1.49 and 0.12-1.42. According to the evaluation results of Igeo and RI, As, which had high degree of enrichment and great potential ecological risk, was the main pollutant, followed by Cu, and pollution of the rest of heavy metals was relatively light. Combining the results of several evaluation methods, in surface sediments of Sanjiu Lake, Gaoyou Lake and Shaobo Lake, these heavy metals had the most serious pollution, the maximum pollution loading and moderate potential ecological risk; in surface sediments of Gehu Lake, Baima Lake and Hongze Lake, some regions were polluted by certain metals, the overall trend of pollution was aggravating, the pollution loading was large, and the potential ecological risk reached moderate; in the other 5 lakes, the risk of sediments polluted by heavy metals, as well as the pollution loading, was small, and the overall was not polluted.

[Excitation-Emission Matrix Fluorescence Spectra Characteristics of DOM in a Combined Constructed Wetland].

Using three-dimensional fluorescence technology, we studied fluorescent characteristics of two polluted rivers by a surface flow+vertical flow combined constructed wetlands of dissolving organic matter. The results showed that (1) the main sources of water-soluble humic organic matter in constructed wetland was biological metabolic input instead of terrigenous input; (2) in the later section of the surface flow constructed wetland, part of proteinoid substance changed into fulvic acid-like substance, which showed that the composition of dissolved organic matter and material structure tended to be stable after surface flow combined constructed wetland treatment; (3) it was of great significance that surface flow constructed wetland in structure transformation of water soluble organic matter, which could significantly improve the stability of water soluble organic matter. Surface flow+vertical flow combined constructed wetland process of dissolved organic matter had a good removal effect.

[Characterizing composition and transformation of dissolved organic matter in subsurface wastewater infiltration system].

In the present study, the soil column with radius of 30 cm and height of 200 cm was used to simulate a subsurface wastewater infiltration system. Under the hydraulic loading of 4 cm x d(-1), composition and transformation of dissolved organic matter (DOM) from different depths were analyzed in a subsurface wastewater infiltration system for treatment of septic tank effluent using three-dimensional excitation emission matrix fluorescence spectroscopy (3D-EEM) with regional integration analysis (FRI). The results indicate that: (1) from different depth, the composition of DOM was also different; influent with the depth of 0.5 m was mainly composed of protein-like substances, and that at other depths was mainly composed of humic- and fulvic-like substances. (2) DOM stability gradually increased and part of the nonbiodegradable organic matter can be removed during organic pollutants degradation process. (3) Not only the organic pollutants concentration was reduced effectively, but also the stability of the DOM improved in subsurface wastewater infiltration system.