[Adsorption Characteristics of Fluoride in Low-Concentration Water by Aluminum and Zirconium-Modified Biochar].

To deal with problems such as the difficult treatment of low-concentration fluoride-containing water and water pollution caused by excessive fluoride (F-) discharge, aluminum and zirconium-modified biochar (AZBC) was prepared and its adsorption characteristics and adsorption mechanism for low-concentration fluoride in water were studied. The results showed that AZBC was a mesoporous biochar with uniform pore structure. It could rapidly adsorb F- from water and reach adsorption equilibrium within 20 min. When the initial ρ(F-) was 10 mg·L-1and the AZBC dosage was 30 g·L-1, the removal rate was 90.7%, and the effluent concentration was lower than 1 mg·L-1. The pHpzc of AZBC was 8.9, and the recommended pH in practical application was 3.2-8.9. The adsorption kinetics accorded with pseudo-second order kinetics, and the adsorption process accorded with the Langmuir model. The maximum adsorption capacities at 25, 35, and 45℃ were 8.91, 11.40, and 13.76 mg·g-1, respectively. Fluoride could be desorbed by 1 mol·L-1 NaOH. The adsorption capacity of AZBC decreased by approximately 15.9% after 5 cycles. The adsorption mechanisms of AZBC were the combination of electrostatic adsorption and ion exchange.Taking actual sewage as theexperimental object, when the AZBC dosage was 10 g·L-1, the ρ(F-) was reduced to below 1 mg·L-1.

[Analysis of Water Quality and Exchange Flux of Interstitial Water-Overlying Water in Sediments of Baiyangdian Entrance Area in Summer].

In order to reveal the interaction of overlying water-interstitial water nitrogen and phosphorus nutrient salt in summer at the entrance region of Baiyangdian Lake, this study sampled six main rivers in the region during July 2019. An analysis of the overlying water and interstitial water quality characteristics and the diffusion flux of applied nutrients at the sediment-water interface revealed the effects of nutrient diffusion on sediments and overlying water. The overlying water analysis showed that the water quality was slightly alkaline in the Baiyangdian Lake. The content of dissolved oxygen (DO) was lower, which provided an anaerobic environment for the release of endogenous pollutants from sediments. The ammonia nitrogen (NH4+-N) ranged from 0.35 to 1.76 mg·L-1, and the content of ammonia nitrogen was the highest in the Zhulong River, which was the main source of water supply. The nitrate nitrogen (NO3--N) content ranged from 0.75 to 1.97 mg·L-1. The total dissolved nitrogen (TDN) ranged from 0.99 to 2.70 mg·L-1, and the content of TDN was the highest in Puhe River. The content of total dissolved phosphorus (TDP) was 0.03 to 0.15 mg·L-1, and the content of TDP was the highest was Baigouyin River, which is near the residential area. The results indicated that the content of ammonia nitrogen in the interstitial water was between 5.24 and 10.64 mg·L-1, which was 10 times that of the overlying water, and endogenous pollution in the former was severe. The nitrate nitrogen content ranged from 0.36 to 0.79 mg·L-1. The total dissolved nitrogen content was between 5.36 and 12.02 mg·L-1, which was 5 times higher than that of the overlying water. The total dissolved phosphorus was between 0.03 and 0.3 mg·L-1. According to integrated pollution index, the degree of interstitial water pollution was much higher than that of overlying water, and the sampling points are seriously polluted. The exchange flux analysis of NH4+-N, TDN, and TDP demonstrated that the diffusion flux of NH4+-N was between 1.71 and 7.43 mg·(m2·d)-1, and the diffusion rate of endogenous ammonia nitrogen to the overlying water was fastest in Fu River, the absorbing river in Baoding. The diffusion flux of total dissolved nitrogen was lower in the Baigouyin River, and the other five sample points averaged 9.11 mg·(m2·d)-1. In summer, the dissolved oxygen was lower and the water-sediment had a larger concentration difference, which led to massive nitrogen nutrient of sediment in anaerobic conditions released to the overlying water in great quantities that caused the serious pollution. The diffusion flux of dissolved total phosphorus showed that the sediment of Pinghe River acted as a "sink" of phosphorus nutrients, and the other sampling points ranged from 0.03 to 0.16 mg·(m2·d)-1, showing the state of phosphorus nutrient released upward to the overlying water. Finally, diffusion flux indicated that endogenous pollutants are crucial sources of overlying water pollutants. In order to effectively control the water quality in the entrance area, desilting the nitrogen and phosphorus nutrient salt of sediment is urgently required.

[Temporal and Spatial Evolution Characteristics of DOM Spectra in Sediment Interstitial Water in Typical Zones of Baiyangdian Lake].

The sources and distribution of dissolved organic matter (DOM) in the interstitial water of Baiyangdian Lake sediments were analyzed using the ultraviolet-visible absorption spectrum (UV-vis) method and three-dimensional excitation emission matrix fluorescence spectroscopy-parallel factor analysis (EEM-PARAFAC). Results showed that the DOM concentrations and molecular weight were significantly higher in summer than in spring and autumn, based on a254 and E2/E3 values. Three protein-like substance (C1, C2, and C3) and two humic-like substances (C4, C5) were identified with the PARAFAC model. Moreover, protein-like substances accounted for the majority of DOM, reaching (63.56±16.07)%. Total DOM fluorescence intensity, the fluorescence intensity of each component, and the relative abundance exhibited significant spatial variation among the different functional zones in Baiyangdian Lake. Protein-like substances were mainly found in the breeding area, whereas humic-like substances mainly occurred in the natural area. The high BIX, FI, ß:α, and low HIX indicated that DOM in sediment interstitial water exhibited low humification and highly autochthonous characteristics. Moreover, the perfect regression equations between water quality and the fluorescent components could provide a useful reference for managers aiming to protect the ecosystem of Baiyangdian Lake.

[Evolution Characteristics and Driving Factors of Denitrification Community Based on Network Analysis in the Process of Spring Thermal Layer Formation in Zhoucun Reservoir].

Combined with on-site water quality investigation and nirS gene high-throughput sequencing technology, the evolution characteristics and influencing factors of the denitrification community during the formation of spring thermal stratification in Zhoucun Reservoir were analyzed. The results show that the water body stratification gradually formed during this period, and the environmental factors (NO3-, NH4+, TN, TOC, BOD5, permanganate index, TP, Fe, and Mn) showed significant differences (P<0.01); nitrogen showed a significant decline process. High-throughput sequencing provided 8703 OTU, which were divided into three phyla and eight major genera, proteobacteria accounted for the largest proportion with 45.27%-78.90%. The α-diversity except for the Simpson index showed that the ACE index, Chao index, Shannon index, and coverage index showed significant differences (P<0.05). The principal coordinate analysis showed the denitrification community exhibited significant differences in the spring, which was consistent with adonis result (P<0.001); network analysis (OTU-OTU) showed that there were seven main modules in this period, including 316 edges of 131 nodes, and the proportion of positive correlation edges was 95.25%. Network analysis (OTU-environmental factors) showed that there were five modules in this period, including 329 edges of 140 nodes, and the proportion of positive correlation edges was 51.98%. Sixty-two indicator OTU and 28 keystone OTU were obtained based on the indicator OTU analysis and network analysis. RDA and mantel test analysis indicated that T, DO, NO3-, TN, TOC, BOD5, and TP were the main environmental factors driving the denitrifying bacterial community structure and the key denitrifying OTU evolution in spring. Our results will provide technical support for the migration and transformation of nitrogen in reservoir water and pollution control.

[Temporal and Spatial Distribution Characteristics and Difference Analysis of Chromophoric Dissolved Organic Matter in Sediment Interstitial Water from Gangnan Reservoir].

The chromophoric dissolved organic matter (CDOM), the main component of dissolved organic matter, affects the morphological characteristics, migration, and conversion of pollutants in water. Based on UV-vis spectra and excitation emission matrix spectroscopy (EEMs) combined with the parallel factor analysis (PARAFAC), the spatial distribution and spectral characteristics were investigated and source analysis of CDOM was performed. Thus, the spatiotemporal differences in the CDOM in Gangnan Reservoir were analyzed. Results showed that a254, a260, a280, and a355 exhibited significant seasonal differences in Gangnan Reservoir, and the order of CDOM concentrations was summer > spring > autumn > winter. There are significant seasonal differences in the E2/E3, E3/E4, E4/E6, and SR of interstitial water CDOM. The concentrations of E2/E3, E3/E4, E4/E6, and SR were high in winter and low in summer. E2/E3 and E3/E4 in autumn and winter were significantly higher than those in spring and summer, and the E3/E4 in autumn and winter was greater than 3.5, which indicates that the CDOM of the autumn and winter sediments has a smaller molecular weight and a lower degree of humification. Protein-like substances (C1), short-wave fulvic acid (C2), and degraded humic substances (C3) were identified by the PARAFAC model, and there was a significant positive correlation among the three fluorescent components (P<0.001). The total fluorescence intensity of CDOM and the fluorescence intensity of each fluorescent component show significant seasonal differences. The total fluorescence intensity and the fluorescence intensity of each component show the highest levels in spring, followed by autumn and winter, and the lowest levels in summer. The proportion of each fluorescent component in autumn and winter and that of each fluorescent component in spring and summer showed no significant difference. There was a significant difference in the proportion of each fluorescent component between autumn/winter and spring/summer. The BIX and FI of CDOM for autumn and winter were higher than those for spring and summer, indicating that the autogenous source of CDOM in autumn and winter is stronger than that in spring and summer, which was consistent with the result of HIX. PCA and Adonis analysis showed that the spectral characteristics of CDOM exhibited obvious seasonal differences (P<0.001). Moreover, the C1, C2, and C3 and water quality parameters (NH4+, NO3-, NO2-, TDN, and TDP) exhibited significant correlation based on linear regression. The results could provide technical support for the control of organic carbon pollution sources and water quality management in Gangnan Reservoir.

[Spatial Distribution Characteristics and Driving Factors of Aerobic Denitrification Bacterial Community Structure from Baiyangdian Lake in Xiong'an New Area During the Winter Freezing Period].

To isolate the aerobic denitrification bacteria suitable for water quality in the low-temperature period of Baiyangdian Lake, a water quality investigation and bioinformatics analysis of the aerobic denitrification bacterial community were carried out using a MiSeq high-throughput sequencing technique based on napA. Moreover, α-diversity, ß-diversity, and network analyses were also carried out. The results showed significant differences in the water quality of different sampling sites in Baiyangdian Lake, and the estuary area exhibited the highest nitrogen concentration. α-diversity exhibited significant differences (P<0.05), and the abundance and diversity of ZZD and BH were the lowest. The operational taxonomic units of the water body mainly belonged to Proteobacteria (α-Proteobacteria, ß-Proteobacteria, and γ-Proteobacteria). Meanwhile, Venn diagram analysis indicated the community of aerobic denitrification bacteria exhibited significant differences, and variance inflation factor and redundancy analysis showed that temperature, dissolved oxygen, ammonia, nitrate, dissolved total phosphorus, and redox potential were the main environmental factors. Network analysis showed that symbiotic relationships accounted for a major proportion of the microbial network. Mantel test analysis shows that temperature, redox potential, nitrate, ammonia, dissolved total phosphorus, and iron and manganese are the key factors affecting the evolution of modular community structure. From all the results, the MiSeq high-throughput sequencing technique based on the napA gene was an effective tool to explore the changes of aerobic denitrification bacterial community structure, which could supply a reference to isolate the "directional-accurate-efficient" aerobic denitrification bacterial agent in the future.

[Spatial Distribution, Spectral Characteristics, and Sources Analysis of Dissolved Organic Matter from Baiyangdian Lake in Xiong'an New District During the Winter Freezing Period].

Based on excitation emission matrix spectroscopy (EEMs) technology combined with parallel factor analysis (PARAFAC) and ultraviolet-visible (UV-vis) spectra, we analyze the spatial distribution, spectral characteristics, and sources of dissolved organic matter (DOM) in Baiyangdian Lake, China, during a winter freezing period. Results showed that the UV-vis absorption spectrum of DOM had no obvious characteristic peak, and that the variation coefficient of absorption exhibited a significant difference (P<0.05) among different districts of Baiyangdian Lake, but that there was no significant difference between the surface and bottom waters. The changes of E3/E4, E2/E3, and SR showed that DOM had low humic and autochthonous characteristics. Two protein-like substances (C1 and C2) and one humic-like substance (C3) were identified by PARAFAC, with a significant correlation (P<0.001) being found between C1 and C3, and C2 and C3. The total DOM fluorescence intensity and the fluorescence intensity of each component exhibited significant differences (P<0.01) in the distribution among the different districts of Baiyangdian Lake, with the maximum value being associated with a sample from the Tanghe River and the minimum value being associated with a sample from Shaochedian. Moreover, the sum of C1+C2 accounted for the major proportion of DOM. DOM exhibited a strong autochthonous characteristic based on the values of BIX, FI, and HIX. Principle component analysis (PCA) and Adonis analysis showed that the spectral characteristics of DOM exhibited a significant difference (P<0.05) among the different districts. C1, C2, and C3 were significantly correlated (P<0.001) with DOM indices (HIX, BIX, Fn280, and Fn355) and water quality parameters[total nitrogen (TN), permanganate index, and total dissolved phosphorus (TDP)] based on multiple linear regression. Our results contribute to previous investigations and provide findings that can assist in the future management and control of organic carbon pollution sources to Baiyangdian Lake.

[Community Structure Characteristics of nirS Denitrifying Bacteria of Spring Typical Parkland Waterbodies in Shijiazhuang City].

Four typical park water bodies located in the main urban area of Shijiazhuang city were selected to study the relationships between water quality and the community structure and diversity of nirS denitrifying bacteria. The results showed that the nitrogen concentration ranged from 4.43 to 13.83 mg·L-1 in four park water bodies, which exhibited notable nitrogen pollution characteristics. Based on the characteristic index analysis of three-dimensional fluorescence spectra, the four park water bodies all exhibited strong autochthonous components and low humus characteristics. The results of Illumina high-throughput sequencing indicated that most of the nirS denitrifying bacteria showed significant differences in dominant genus. The unclassified_Bacteria (53.52%), Pseudomonas (60.48%), and Rhodobacter (46.94%) were the dominant bacteria in Yuxi park, Shuishang park, and Chang'an park, respectively. In comparison, unclassified_Bacteria (36.19%) and unclassified_Proteobacteria (23.44%) were the dominant bacteria in Shiji park. Redundancy analysis showed that denitrification bacteria in Yuxi park were mainly affected by nitrate, total nitrogen, and dissolved oxygen; denitrification bacteria in Shuishang park were greatly affected by total phosphorus; denitrification bacteria in Chang 'an park were mainly affected by ammonia and nitrous nitrogen; and denitrification in Shiji park were mainly affected by total phosphorus, nitrite, and ammonia. Overall, the water quality and the community structure of nirS denitrification bacteria exhibited significant differences in park water bodies. Further research could contribute to the understanding of water quality characteristics and the denitrifying community structure of urban water systems, and develop efficient denitrifying bacterial agents.

[Spectral Evolution Characteristics of DOM in Sediment Interstitial Water During the Formation Stage of Thermal Stratification in the Main Reservoir Area of the Zhoucun Reservoir].

Based on three-dimensional fluorescence spectra (EEMs) combined with parallel factor analysis (PARAFAC), and ultraviolet-visible (UV-Vis) spectra, we analyzed the vertical distribution and characteristics of dissolved organic matter in sediment interstitial water during the formation stage of thermal stratification in the Zhoucun Reservoir. The results show that the UV-Vis absorption coefficient varies between -400% and 400%, indicating the different properties of DOM(dissolved organic matter) at different depths. The changes of E2/E3 show that the proportion of fulvic acid in DOM increases with the stratification of the reservoir and fulvic acid accounts for the main proportion with autochthonous characteristics based on E3/E4>3.5 and SR>1. Two fulvic-like substances (C1, C3), two protein-like substance (C2, C5), and two humic-like substances (C4, C6) were identified with the PARAFAC model. Moreover, fulvic-like and protein-like substances account for most of substances. The total DOM fluorescence intensity and the fluorescence intensity of each component show a decreasing trend with the occurrence of stratification and exhibit significant vertical and temporal differences. Based on the analysis of FI, HIX, BIX, and ß:α in sediment interstitial water, the high BIX, FI, ß:α and low HIX indicate that the DOM of sediment interstitial water has strong autochthonous components and original characteristics of aquatic bacteria.

[Advanced nitrogen removal using innovative denitrification biofilter with sustained-release carbon source material].

An innovative denitrification biofilter was developed with polycaprolactone (PCL) as the carbon source and biofilm carrier. The performance of nitrogen removal was investigated with biologically treated effluent from secondary clarifier, and the results indicated that a maximum TN removal efficiency of 98.9% was achieved under the following conditions: influent total nitrogen (TN) concentration 30.0 mg x L(-1), denitrification load 54.0 mg (L x h)(-1), operating temperature 20. 1-22.0 degrees C, hydraulic retention time 0. 5 h; the total organic carbon (TOC) in effluent was 6.5-8.4 mg x L(-1), which was increased by 2.0-3.0 mg x L(-1) compared with that in the influent; the suspended solids (SS) concentration was less than 4.0 mg x L(-1) during operation; nearly 84.2% of the total released organic carbon which was used as electron donor in the denitrification process, was derived in the presence of microbes. The surface of the PCL pellets was observed by scanning electron microscope (SEM), it was shown that thick biofilm was formed on the surface of pellets, and the main microbial species were Bacillus and Trichobacteria.

[Analysis of methanogenic community of anaerobic granular sludge in a full-scale UASB treating avermectin wastewater].

Methanogens is considered to be important functional microbial population in anaerobic granular sludge. Fluorescence in situ hybridization was used to analyze methanogens of anaerobic granular sludge in a full-scale UASB treating avermectin wastewater. The results indicated that the distribution forms of methanogens, Methanobacteriales and Methanosarcinales were identical on the surface and inner face of granular sludge samples in different formation stages (with different diameters) , although the relative abundances of these methanogens were different. The relative abundances of methanogens on the inner face were larger than these on the surface of granular sludge samples. The relative abundances of Methanobacteriales were larger than these of Methanosarcinales. The relative abundances of methanogens in all granular sludge samples ranged from (25.50 +/- 8.63)% to (48.67 +/- 8.87)%. The maximum relative abundances of methanogens were obtained in mature granular sludge with diameter of 1.0-2.0 mm, (47.08 +/- 8.26)% on the surface and (48.67 +/- 8.87)% on the inner face, respectively. The avermectin residue in wastewater showed possible inhibition effect on methanogens. The maximum specific methanogenic activities of granular sludge samples ranged from 1.311 to 1.562 g/(g x d), varying as same as COD removal ratios and relative abundances of methanogens, implying the strong correlation of methanogens with bioactivity of granular sludge.