Nutrient removal effect and characteristics of integrated floating beds at low temperature.

To investigate the effect of combined floating beds on nutrient removal under low temperature, an integrated floating bed with corn flakes (IFB-CF) and an integrated floating bed with light ceramsite (IFB-LC) were constructed in parallel. IFB-LC was used as control group under water temperatures of 9.3-14 °C and a water exchange time of 168 h. Nitrogen and phosphorus removal efficiency, the nutrient level of a hydrophyte (Oenanthe javanica), and the microbial population characteristics of the combined floating bed were investigated. For IFB-CF removal efficiencies, the degradation quantities of total nitrogen (TN), NO3--N, and NH4+-N for IFB-CF were 13.58 ± 0.67 mg/L, 4.40 ± 0.61 mg/L, and 9.21 ± 0.38 mg/L, respectively; in contrast, degradation quantities for IFB-LC were lower (6.41 ± 1.47 mg/L, 2.15 ± 0.40 mg/L, and 5.95 ± 0.46 mg/L, respectively). The reductions in COD (Chemical Oxygen Demand, using K2Cr2O7 as oxidizer) for IFB-LC and IFB-CF were 86.89% and 66.06%, respectively. Using the MiSeq high throughput sequencing method, we analysed microbial community structure and diversity on the base material surface of the IFB-CF and IFB-LC. The results showed 15 phyla, 165 genera, and 78 families on the surface of the IFB-CF. The phylum, genus, and family with the highest abundances were Proteobacteria (48.29%), Trichococcus (10.39%), and Comamonadaceae (12.45%), respectively. We identified 15 phyla, 144 genera, and 93 families on the surface of the IFB-LC. The phylum, genus, and family with the highest abundances were Proteobacteria (46.10%), Dyadobacter (22.67%), and Cytophagaceae (28.75%), respectively. The Chao, ACE, and Shannon & Simpson indices for the IFB-LC were 4081, 6295, and 5.10, and 0.05, respectively; for the IFB-CF they were 4938, 7461, 5.77, and 0.02, respectively. Catalase (CAT) and Peroxidase (POD) concentrations in Oenanthe javanica for IFB-LC were 35.48 u/gFW/min and 1.03 u/gFW/min, respectively; for IFB-CF they were 32.33 u/gFW/min and 1.25 u/gFW/min, respectively. The nutritional energies of IFB-CF and IFB-LC were 107 kJ/100g and 84 kJ/100g. Using the Mondal model of TN removal, k (half-saturation constant) values for IFB-LC and IFB-CF were 35.67 mg/L and 39.23 mg/L, respectively, with a correlation coefficient (R2) of 0.97.

The first metagenome of activated sludge from full-scale anaerobic/anoxic/oxic (A2O) nitrogen and phosphorus removal reactor using Illumina sequencing.

The anaerobic/anoxic/oxic (A2O) process is globally one of the widely used biological sewage treatment processes. This is the first report of a metagenomic analysis using Illumina sequencing of full-scale A2O sludge from a municipal sewage treatment plant. With more than 530,000 clean reads from different taxa and metabolic categories, the metagenome results allow us to gain insight into the functioning of the biological community of the A2O sludge. There are 51 phyla and nearly 900 genera identified from the A2O activated sludge ecosystem. Proteobacteria, Bacteroidetes, Nitrospirae and Chloroflexi are predominant phyla in the activated sludge, suggesting that these organisms play key roles in the biodegradation processes in the A2O sewage treatment system. Nitrospira, Thauera, Dechloromonas and Ignavibacterium, which have abilities to metabolize nitrogen and aromatic compounds, are most prevalent genera. The percent of nitrogen and phosphorus metabolism in the A2O sludge is 2.72% and 1.48%, respectively. In the current A2O sludge, the proportion of Candidatus Accumulibacter is 1.37%, which is several times more than that reported in a recent study of A2O sludge. Among the four processes of nitrogen metabolism, denitrification related genes had the highest number of sequences (76.74%), followed by ammonification (15.77%), nitrogen fixation (3.88%) and nitrification (3.61%). In phylum Planctomycetes, four genera (Planctomyces, Pirellula, Gemmata and Singulisphaera) are included in the top 30 abundant genera, suggesting the key role of ANAMMOX in nitrogen metabolism in the A2O sludge.

A cooperative construction strategy for multi-parameter spatial variant random fields and its application in groundwater pollution risk assessment.

The spatial variability of hydrogeological parameters is a significant source of uncertainty in groundwater numerical modeling and has a certain risk impact on the prediction of pollutant migration and transformation. Current research has focused on the effects of single-parameter spatial variant random fields or utilizing random sampling methods to randomly combine multiple-parameter spatial variant random fields while ignoring the correlation between parameters. This paper proposes an innovative concept of associated random variables to construct multi-parameter synergistic spatial variant random fields, ensuring both the spatial variability and inherent correlation of the parameters. A hypothetical case was constructed, and the Monte Carlo sampling experiment based on computer simulation was used to assess groundwater pollution risks with multiple associated parameters. The results show that hydraulic conductivity and porosity are the main sensitive parameters. The associated random variable allows for the representation of positive correlation, negative correlation, and no correlation between the hydraulic conductivity and porosity. The pollutant mass concentrations in each observation well conform to the generalized extreme value distribution, and the pollution risks of each water well as well as the concentration distribution intervals of pollutants with different probabilities can be obtained. The influence of associated parameters on the cumulative risk of contaminants in observation wells and pollution degree range is only related to their mathematical distribution and is independent of correlations between parameters. This study addresses the issues of spatial variability and inherent correlation of hydrogeological parameters, which are of great significance for groundwater pollution risk assessment and the promotion of sustainable water quality management of groundwater resources.

Subnano-Fe (Co, Ni) clusters anchored on halloysite nanotubes: an efficient Fenton-like catalyst for the degradation of tetracycline.

Iron-based catalysts are environmentally friendly, and iron minerals are abundant in the earth's crust, with great potential advantages for PMS-based advanced oxidation process applications. However, homogeneous Fe2+/PMS systems suffer from side reactions and are challenging to reuse. Therefore, developing catalysts with improved stability and activity is a long-term goal for practical Fe-based catalyst applications. In this study, we prepared Fe-HNTs nanoreactors by encapsulating a nitrogen-doped carbon layer with one-dimensional halloysite nanotubes (HNTs) using the molten salt-assisted method. Subsequently, Fe (Co, Ni) nanoclusters were anchored onto the nitrogen-doped carbon layer at a relatively low temperature (550℃), resulting in stable and uniform distribution of metal nanoclusters on the surface of HNTs carriers in the form of Fe-Nx coordination. The results showed that the dissolution of the molten salt and leaching of post-treated metal oxides generated numerous mesopores within the Fe-HNTs nanoreactor, leading to a specific surface area more than 10 times that of HNTs. This enhanced mass transfer capability facilitates rapid pollutant removal while exposing more active sites. Remarkably, Fe-HNTs adsorbed up to 97% of tetracycline within 60 min. In the Fe-HNTs/PMS system, the predominant reactive oxygen species has been shown to be 1O2, and the added tetracycline was degraded by more than 98% within 5 min. The removal of tetracycline was maintained above 96% in the presence of interfering factors such as wide pH (3-11) and inorganic anions (5 mM Cl-, HCO3-, NO3-, and SO42-). The investigated mechanism suggests that efficient degradation and interference resistance of the Fe-HNTs/PMS system is attributed to the synergistic effect between the rapid adsorption of porous structure and the non-radical (1O2)-dominated degradation pathway.

A construction strategy for conservative adaptive Kriging surrogate model with application in the optimal design of contaminated groundwater extraction-treatment.

When the simulation-optimization model to optimize the groundwater extraction-treatment schemes is used, the construction of a surrogate model for the numerical simulation model has become an effective means to overcome the large calculation load of repeatedly calling the numerical model. However, there are still some problems in using the surrogate model, such as large training sample size, low accuracy, and poor optimization results. In this paper, a conservative adaptive Kriging surrogate model (CAKSM) was proposed by coupling the Kriging surrogate model, optimal solution adaptive sampling method (OSAS), and conservative prediction idea. Firstly, an initial Kriging surrogate model (IKSM) was built for the numerical simulation model of groundwater flow and solute transport. Then, the IKSM was coupled with the optimization model to construct the adaptive Kriging surrogate model (AKSM) by using OSAS. A safety margin was added to the AKSM to build the CAKSM. Finally, the simulation-optimization models based on IKSM, AKSM, and CAKSM were solved by the genetic algorithm, respectively. The results showed that the IKSM could well substitute for the simulation model. The AKSM significantly improved the approximation degree between the surrogate model and the simulation model at the optimal solution by supplementing a small number of new samples. CAKSM could effectively constrain the pollutant mass concentrations within the controlled value, improving the reliability of the optimization scheme. The optimal extraction wells based on different surrogate models were all well 5, well 6, and well 9. They were concentrated in the middle and lower reaches of the contaminated plume's central axis. The sequence for the remediation effects by different surrogate models from high to low was as follows: CAKSM, AKSM, and IKSM. The risk rate of the optimal remediation scheme from the hydraulic conductivity random fields was as high as 12.12%, and the risks were mainly located upstream of the pollution plume's central axis.

Use of the Normalized Difference Road Landside Index (NDRLI)-based method for the quick delineation of road-induced landslides.

Recognition and classification of road-related landslides are a critical requirement in pre- and post-disaster hazard analysis. They are primarily done through field mapping or manual image interpretation from commercial satellites images. This paper developed a Normalized Difference Road Landside Index (NDRLI)-based method to delineate road-induced landslides and enhance their presence in remotely sensed digital imagery based on free Landsat Operational Land Imager (OLI) sources. The NDRLI-based method includes NDRLI, Shape Index of Spectral Curve (SISC), and other optimizing steps such as deleting shadow and slope <20° area to recognise landslides. The test results show that the NDRLI-based method is effective in extracting road-induced landslide information, although the Kappa coefficient should be further improved.

[Comparative Metagenomics of BIOLAK and A2O Activated Sludge Based on Next-generation Sequencing Technology].

This is the first report of comparative metagenomic analyses of BIOLAK sludge and anaerobic/anoxic/oxic (A2O) sludge. In the BIOLAK and A2O sludge metagenomes, 47 and 51 phyla were identified respectively, more than the numbers of phyla identified in Australia EBPR (enhanced biological phosphorus removal), USA EBPR and Bibby sludge. All phyla found in the BIOLAK sludge were detected in the A2O sludge, but four phyla were exclusively found in the A20 sludge. The proportion of the phylum Ignavibacteriae in the A2O sludge was 2.0440%, which was 3.2 times as much as that in the BIOLAK sludge (0.6376%). Meanwhile, the proportion of the bacterial phylum Gemmatimonadetes in the BIOLAK sludge was 2.4673%, which was >17 times as much as that in the A2O sludge (0.1404%). The proportion of the bacterial phylum Chlamydiae in the BIOLAK metagenome (0.2192%) was >6 times higher than that in the A2O (0.0360%). Furthermore, 167 genera found in the A20 sludge were not detected in the BIOLAK sludge. And 50 genera found in the BIOLAK sludge were not detected in the A20 sludge. From the analyses of both the phylum and genus levels, there were huge differences between the two biological communities of A2O and BIOLAK sludge. However, the proportions of each group of functional genes associated with metabolism of nitrogen, phosphor, sulfur and aromatic compounds in BIOLAK were very similar to those in A2O sludge. Moreover, the rankings of all six KEGG (Kyoto Encyclopedia for Genes and Genomes) categories were identical in the two sludges. In addition, the analyses of functional classification and pathway related nitrogen metabolism showed that the abundant enzymes had identical ranking in the BIOLAK and A2O metagenomes. Therefore, comparative metagenomics of BIOLAK and A2O activated sludge indicated similar function assignments from the two different biological communities.

[Biodiversity and Function Analyses of BIOLAK Activated Sludge Metagenome].

The BIOLAK is a multi-stage activated sludge process, which has been successfully promoted worldwide. However, the biological community and function of the BIOLAK activated sludge ( the core component in the process) have not been reported so far. In this study, taking Lianyungang Dapu Industrial Zone WWTP as an example, a large-scale metagenomic data (428 588 high-quality DNA sequences) of the BIOLAK activated sludge were obtained by means of a new generation of high-throughput sequencing technology. Amazing biodiversity was revealed in the BIOLAK activated sludge, which included 47 phyla, 872 genera and 1351 species. There were 33 phyla identified in the Bacteria domain (289 933 sequences). Proteohacteria was the most abundant phylum (62.54%), followed by Bacteroidetes (11.29%), Nitrospirae ( 5. 65%) and Planctomycetes (4.79%), suggesting that these groups played a key role in the BIOLAK wastewater treatment system. Among the 748 bacterial genera, Nitrospira (5.60%) was the most prevalent genus, which was a key group in the nitrogen cycle. Followed by Gemmatimonas (2.45%), which was an important genus in the biological phosphorus removal process. In Archaea domain (1019 sequences), three phyla and 39 genera were detected. In Eukaryota domain (1055 sequences), 60 genera and 10 phyla were identified, among which Ciliophora was the largest phylum (257 sequences). Meanwhile, 448 viral sequences were detected in the BIOLAK sludge metagenome, which were dominated by bacteriophages. The proportions of nitrogen, aromatic compounds and phosphorus metabolism in the BIOLAK sludge were 2.50%, 2.28% and 1.56%, respectively, which were higher than those in the sludge of United States and Australia. Among four processes of nitrogen metabolism, denitrification-related genes were most abundant (80.81%), followed by ammonification (12.78%), nitrification,(4.38%) and nitrogen fixation (2.04%). In conclusion, the BIOLAK activated sludge had amazing biodiversity, meanwhile, functional genes involved in nitrogen, aromatic compounds and phosphorus metabolism were very abundant.

Phosphorus removal from secondary effluents through integrated constructed treatment system.

The treatment capacity of an integrated constructed treatment system (CTS) was explored which was designed to reduce phosphorus (P) from secondary effluents. The integrated CTS was combined with vertical-flow constructed wetland, floating bed and sand filter. The vertical wetland was filled from the bottom to the top with gravels, steel slag and peat. Vetiverzizanioides (L.) Nash was selected to grow in the vertical constructed wetland while Coixlacrymajobi L. was grown in floating bed. The results suggested that integrated CTS displayed excellent removal efficiency for chemical oxygen demand (COD), dissolved phosphorus (DP), and total phosphorus (TP). The average COD removal efficiency of the integrated CTS was 90.45% after 40 days of operation, the average DP and TP removal efficiencies of the integrated CTS were 97.43% and 96.40%, respectively. The integrated CTS has good potential in removing COD as well as P from secondary effluents.