[Efficacy and Mechanism of Tetracycline Adsorption by Boron-doped Mesoporous Carbon].

Using coconut shell and boric acid as raw materials， a new boron-doped coconut shell mesoporous carbon material （B-CSC） was prepared using a simple one-step pyrolysis method for efficient adsorption and removal of tetracycline pollutants in water. The effects of pyrolysis temperature and boron-carbon mass ratio on the adsorption performance under key preparation conditions were systematically studied， and their microstructure and physicochemical properties were characterized using a specific surface area and pore size analyzer （BET）， field emission scanning electron microscopy （SEM）， X-ray photon spectroscopy （XPS）， Raman spectrometer （Raman）， and Zeta potentiometer （Zeta）. The effects of initial pH， different metal cations， and different background water quality conditions on the adsorption effect were systematically investigated. Combined with material characterization and correlation analysis， the enhanced adsorption mechanism was discussed and analyzed in depth. The results showed that one-step pyrolysis could incorporate boron into the surface and crystal lattice of coconut shell charcoal， resulting in a larger specific surface area and pore volume， and the main forms of boron introduced were H3BO3， B2O3， B， and B4C. The adsorption capacity of B-CSC to tetracycline reached 297.65 mg·g-1， which was 8.9 times that of the original coconut shell mesoporous carbon （CSC）. At the same time， the adsorption capacity of B-CSC for rhodamine B （RhB）， bisphenol A（BPA）， and methylene blue （MB）， common pollutants in aquatic environments， was as high as 372.65， 255.24， and 147.82 mg·g-1， respectively. The adsorption process of B-CSC to tetracycline was dominated by physicochemical interaction， mainly involving liquid film diffusion， surface adsorption， mesoporous and microporous diffusion， and active site adsorption， and H3BO3 was the main adsorption site. The adsorption strengthening mechanism mainly reduced the chemical inertness of the carbon network and enhanced its π-π interaction and hydrogen bonding with tetracycline molecules.

[Effectivity of Multiphase Fenton-like System of Iron Reduction Induced by Bisphenol A Authigenic Photoelectron].

In recent years, the Fenton-like (Fe2+-PMS/PS) advanced oxidation technology of persulfate activated by ferrous ions has been increasingly developed, but the difficulty of Fe3+ reduction, which stops the reaction, still restricts its large-scale application. In this study, it was found that when some organic compounds represented by bisphenol A (BPA) were mixed with Fe3+ and pristine TiO2, some surface structures could broaden the light response range of TiO2, capture visible light, and transfer the photoelectrons to Fe3+ through TiO2 for reduction, so as to achieve an infinite cycle of Fe3+/Fe2+. According to the above principle, a BPA-TiO2-Fe3+-PS composite system under visible light was constructed to degrade BPA, and its catalytic performance, catalytic mechanism, and influencing factors were discussed. The results showed that the system had outstanding catalytic performance, the degradation efficiency of BPA (50 mg·L-1) reached 93.1%, and the mineralization efficiency reached 70% within 60 min. At the same time, it verified that the system could reduce Fe3+ by the authigenic photoelectron of bisphenol A, and the steady-state concentration of Fe2+ obtained by 60 min reduction was 3.5 µmol·L-1. The main active oxidizing species in the system were sulfate radicals (SO4-[KG-*2/3]·) and hydroxyl radicals (·OH), of which the contribution rate of·OH was more than 60%. An appropriate increase in TiO2, Fe3+, and PS dosage and light intensity could improve the degradation effect. The system had the best treatment efficiency under weak acid conditions, and the degradation efficiency reached 96.5%. It also had a good effect under neutral conditions. CO32-, H2PO4-, and SO42- had a certain inhibitory effect on the system.

[Adsorption Characteristics and Long-term Effectiveness Evaluation of Iron-nitrogen Co-doped Biochar for Secondary Water-Soluble Organic Matter].

In order to economically and efficiently remove dissolved organic matter (DOM) in the secondary water of wastewater treatment plants, this study adopted iron-nitrogen co-doped biochar material (Fe-N-C) as a new adsorbent and systematically analyzed the effect of this new carbon material on the secondary water DOM, as well as the adsorption performance, kinetic process, selectivity, and mechanism of action. In addition, the long-term performance and reusability of the adsorption material were thoroughly investigated through a fixed-bed adsorption device. The results show that Fe-N-C had outstanding adsorption performance for secondary water DOM. When the dosage was only 1.0 g·L-1, the removal rates of TOC, UV254, and UV280 were as high as 40.18%, 76.92%, and 78.26%, respectively, which are far higher. Regarding the adsorption effect of pure biochar and conventional activated carbon, the adsorption process conformed to the pseudo-second-order kinetics and Freundlich adsorption isotherm model, indicating that the adsorption process is a multilayer chemical adsorption involving valence electrons and the exchange of electrons. The three-dimensional fluorescence spectroscopy, molecular weight distribution, and resin analysis results, such as classification and characterization, showed that Fe-N-C had selective adsorption for different components in the secondary water DOM. The fixed bed adsorption column with Fe-N-C as the core had the maximum removal rate of secondary water TOC, UV254, and UV280 as high as 94.09%, 95.65%, and 97.18%, respectively, and had good stability. It was close to adsorption saturation when the processing capacity reached 620 times the bed volume. However, after the regeneration heat treatment, the adsorption performance was remarkably restored. These results are expected to provide reference for the further development of high-efficiency adsorption water treatment technology.

[Degradation Characteristics and Mechanism of Ibuprofen by Ozone Catalyzed by Nitrogen-Doped Biochar].

This study used a novel nitrogen-doped biochar (N-C) to catalyze the oxidative degradation of IBP in water by ozone and studied the catalytic ozone oxidation degradation of ibuprofen (IBP) efficiency and mechanism. Furthermore, it explored the influence of pH, ozone dosing quantity, catalyst dosing quantity, different anions, and background of water quality conditions on the IBP degradation efficiency. The results showed that, compared with that of some common carbon-based catalysts (g-C3N4, biochar, and granular-activated carbon) and metal catalysts (MnO2 and Fe3O4), the N-C catalytic ozone system had a very outstanding oxidation degradation performance of organic pollutants; the removal rate of IBP reached 100% in 5 min, and the utilization rate of ozone was increased from 10% to 46%. The treatment efficiency of the system was enhanced with the increase in pH. Compared with that by increasing the ozone dosage, the treatment capacity of the system was significantly improved by increasing the concentration of catalyst. The quenching experiment and EPR further confirmed that N-C could effectively catalyze ozone to produce more reactive oxygen species, such as superoxide radicals (·O2-) and H2O2. It was also found that·O2- was the main active substance in the reaction system and played a leading role in the degradation of IBP.

[Effects of Dissolved Oxygen on Nutrient Removal Performance and Microbial Community in Low Carbon/Nitrogen Municipal Wastewater Treatment Process].

To explore the effects of dissolved oxygen (DO) on the treatment of low carbon/nitrogen municipal wastewater, this study examined the characteristics of the microbial community in a low carbon source environment. The treatment process was conducted with the aeration area having DO concentrations of 2-3, 1-2, and lower than 1 mg·L-1. The results demonstrated that reduced DO concentration in the aeration area increased the efficiency of the nitrogen removal process by 20.23% and 80.54%, for external and internal carbon sources, respectively. Similarly, the efficiency of internal carbon source utilization in the phosphorus removal process increased by 13.89%, thus enhancing the nutrient removal efficiency of the low carbon/nitrogen wastewater treatment system. High-throughput sequencing and RDA analysis showed that reduced oxygen concentration motivated an adjustment in microbial community structure, causing functional microorganisms (i.e., Dechloromonas) to become dominant. In addition, the upregulation of genes associated with energy production and conversion, signal transduction, substrate transport, and metabolism provided favourable nutritional conditions for the proliferation of functional microorganisms in low carbon source conditions. This study provides a theoretical basis for improving the growth of microorganisms involved in the nutrient removal process when treating low carbon/nitrogen municipal wastewater.

[Abundance Change of Antibiotic Resistance Genes During PDWW Recycling and Correlations with Environmental Factors].

Research on the distribution of antibiotic resistance genes (ARGs) in urban sewage treatment systems is extensive, but there is still insufficient research on their abundance in industrial wastewater recycling systems. In this study, a printing and dyeing wastewater (PDWW) recycling system was constructed, and 16S rDNA and high-throughput sequencing technology was used to analyze the microbial communities and ARG abundance during the treatment process. A total of 52 ARGs in nine categories were detected, of which the relative abundance of ß-lactam resistance genes was the highest. During the treatment cycle, the concentration of aromatic pollutants increased with an increase in the number of cycles, while the abundance of ß-lactam resistance genes increased first, decreased, and then increased (reaching 61.85% on the 100th day). At the same time, the abundance of Firmicutes, Actinobacteria, and Cyanobacteria related ARGs decreased significantly (by 84.66%, 64.38%, and 85.15%, respectively). More than 21 kinds of ARGs were significantly affected by the enrichment by the aromatic pollutants. Among them, 6 kinds of ARGs were significantly positively correlated with changes in the concentrations of the aromatic pollutants (P<0.01), while 6 were significantly negatively correlate (P<0.01). These results show that the abundance of ARGs was affected by the microbial communities and the aromatic pollutants, which increased at first, decreased, and then increased during the PPDW recycling process. This study reveals the effects of the enrichment of aromatic contaminants and changes in microbial communities on ARGs during PPDW recycling, and provides theoretical guidance for the recycling of PDWW to reduce environmental pollution associated with ARGs.

[Activation of Permonosulfate by Rhodamine B for BPA Degradation Under Visible Light Irradiation].

Although the activation method of permonosulfate has been gradually developed, its practical application is severely restricted by the high cost and difficult recovery of the catalyst, thereby resulting in secondary pollution. In this study, the application potential of self-decolorization of dyes and degradation of other pollutants through persulfate(PS) activation was examined by building a self-decolorization system. The results showed that the dyes could activate PS under visible light irradiation, which could realize not only the self-decolorization of dyes, but also the degradation of other pollutants. The degradation rates of rhodamine B and bisphenol A could reach 80% and 90%, respectively. This process included both free radical reaction pathways and nonradical reaction pathways. The active oxidants produced in the system included superoxide radicals, sulfate radicals, hydroxyl radicals, and singlet oxygen. The self-decolorization efficiency of dyes was related to the type of dyes, initial concentration of the dyes, dosage of PS, and initial pH of the solution. Meanwhile, the initial concentrations of the dyes and other pollutants had a great influence on the degradation of other pollutants. This study provides a new idea for economic and environmental protection in the PS activation method, and has broad application prospects in the treatment of printing and dyeing wastewater.

[Characteristics and Removal Mechanism of an Electro-Hybrid Ozonation-Coagulation System in the Treatment of Organic Matters].

To improve the removal efficiency of dissolved organic matter in wastewater treatment plant (WWTP) effluent, electro-hybrid ozonation-coagulation (E-HOC) is proposed and the treatment characteristics and removal mechanism for WWTP effluent and ibuprofen (IBP) are investigated. The E-HOC process has a better removal effect on dissolved organic matter in WWTP effluent, achieving 46.4%, 20.0%, 19.4%, 36.1%, and 49.7% higher removal than EC, ozonation, pre-ozonation-EC, electrocoagulation-ozonation, and chemical coagulation, respectively. To determine the mechanism of the E-HOC process, quenching experiments and electron paramagnetic resonance (EPR) were conducted, which confirmed that metal coagulants can be used as a catalyst to effectively increase the generation of the hydroxyl radical (·OH). Synergistic effects between ozone and the coagulants (SOC) were also found to be involved. Fourier-transform infrared spectroscopy (FT-IR) illustrated that the surface hydroxyl groups of the coagulant (hydrolyzed species produced by Al anode electrolysis) were the active sites for the generation of·OH in the SOC reaction. Based on a kinetics analysis of organic matter removal in the E-HOC system, SOC effects and ozonation played dominant roles in the E-HOC process. Additionally, the SOC created a new pathway for·OH formation.

[Degradation of Dye Rhodamine B by Solar Thermally Activated Persulfate].

In advanced oxidation technology based on sulfate radicals, thermal activation is one of the most effective methods for persulfate (PS) activation, with broad application potential for the use of solar energy to activate PS to degrade pollutants. In this study, the efficiency and mechanism of degradation of rhodamine B by solar thermally activated PS were investigated using a solar collector reactor. The effects of solar irradiation intensity, PS concentration, substrate concentration, initial pH of the solution, and background water quality on the degradation efficiency of rhodamine B were examined. The results show that the solar thermally activated PS system has outstanding oxidation degradation performance with respect to organic pollutants. The removal rate and mineralization rate of rhodamine B reached 94% and 60%, respectively, after a 120 min reaction time. The treatment efficiency of the system was notably affected by the solar radiation intensity, with performance ranked in the order sunny days > cloudy days > rainy days. The treatment efficiency of the system could be significantly improved by increasing the concentration of PS or reducing the initial concentration of the substrate, and by adjusting the initial pH of the solution to neutral. SO4-·and·OH are the main active oxidants in the reaction system, and·OH plays a major role in the degradation process.

[Metagenomic Insights into Salinity Build-up in Microbial Communities and Metabolism of Hydrolytic Bioreactor Treating High-color PDWW].

In this study, to solve the problem of salinity enrichment in industrial wastewater recycling, a hydrolytic bioreactor was continuously operated to treat high-color printing and dyeing wastewater (PDWW) with salinity build-up. Nearly complete color removal was achieved even with salinity build-ups from 0.5 to 4 g·L-1 in the influent. Pyrosequencing of 16S rRNA genes showed that the salinity build-up results in the decrease of microbial species from 882 to 631; however, the biodiversity of the bacterial community remains stable. Metagenomic analysis indicated that salinity build-up caused no obvious effect on the overall function of the bacterial community, but altered the abundance of specific decoloring genes. Proteobacteria dominated in the bioreactor, and Methanothrix and Geobacter were the dominant genera under low salinity conditions. Proteobacteria increased in abundance with salinity build-up. Desulfovibrio and Desulfococcus were the two predominant genera in the bioreactor fed with sodium sulphate salinity build-up, demonstrating opposite responses to the sodium stress. PICRUSt functional analysis showed that the relative abundance of the decolorizing enzymes SOD1 and SOD2 decreased significantly, but the relative abundance of CAT and TYR increased, ensuring the stability of the decolorizing function of the hydrolysis biological system. From the perspective of the functional genes of hydrolysis decolorization, this study explored the effect of salinity build-up on the microbial community and function of hydrolysis, providing a theoretical basis for the study of decolorization and organic matter removal mechanism of PDWW under the condition of salinity build-up.

[Characteristics of Nutrient Removal in a Pilot-scale A2/O with Mixture of Sludge Fermentation Liquor and Tail Water as External Carbon Source].

To resolve the issue of sewage fluctuation and discontinuity in a rural district of China, a new operation mode of replenishing the mixture of fermentation liquor and tail water during the off-flow period was proposed, and the nutrient removal performance of a pilot-scale A2/O system with this operation mode was investigated. The results of beaker experiments found that the mixture of tail water and fermentation liquor at a ratio of 12:1 had better denitrification and phosphorus release/absorption characteristics than the raw water, and theoretically had the function of enhancing denitrification and phosphorus removal performances. The results of a 97 d pilot test showed that the removal efficiency of TN and TP was improved after the system was adjusted from the constant flow mode to this new operation mode, and the average removal rate of TN and TP increased from 69.27% and 86.94% to 73.34% and 89.94%, respectively. The corresponding average effluent concentration decreased from 15.77 mg·L-1 and 0.80 mg·L-1 to 13.76 mg·L-1 and 0.64 mg·L-1. The sequencing results of the 16S rRNA gene showed that this new operation mode was beneficial to the enrichment of five common hydrolytic acidizing bacteria genera, six phosphorus-accumulating organisms genera, and four denitrifying bacteria genera. This was also the main reason for the improved nutrient removal performance. According to the long-term monitoring of the characteristics of activated sludge, this new operating mode will degrade the sedimentation performance of activated sludge in the system, and the average SVI increased from 106 mL·g-1 to 131 mL·g-1. However, this degree of deterioration did not adversely affect the sludge activity and nutrients removal performance of the system, and there was no sludge bulking in the entire experiment. The results of this study have shown that the A2/O system can maintain and improve the performance of nutrients removal by replenishing the mixture of tail water and sludge fermentation liquor when the flow is cut off. This will provide new ideas for the design and operation of sewage treatment plants in rural areas in the future.

[Construction and Denitrification Performance of A2/O Based on Partial Nitrification Coupled with an ANAMMOX System].

To resolve the issue of existing municipal wastewater treatment plants (WWTPs) in China with an insufficient influent carbon source, a bench-scale A2/O process based on partial nitrification coupled with ANAMMOX was constructed by controlling aeration partition ratio, dissolved oxygen (DO) concentration, and sludge retention time (SRT). In this study, the nitrogen removal performance, nitrogen removal pathway, and microbial community structure of the system under different conditions were investigated. The results showed that the system had excellent nitrogen removal efficiency at low-C/N influent (C/N=5). The A2/O reactor had experienced the co-culture stage (Phase 1), screening stage (Phase 2-3), and enrichment stage (Phase 4) successively during the 140-day experiment, and the nitrogen removal pathway changed from nitrification and denitrification to partial nitrification coupled ANAMMOX in the end. The optimal removal efficiencies of 97.69% for NH4+-N and 87.83% for TN were obtained in the enrichment stage (Phase 4), and the effluent concentration of NH4+-N and TN were 1.20 mg·L-1 and 7.03 mg·L-1, respectively. Illumina MiSeq sequencing results showed that the enrichment of AOB including Nitrosomonas and Nitrosospira and the elimination of NOB including Nitrospira, Nitrococcus, and Nitrobacter were the main causes of achieving partial nitrification in the system. The enrichment of AnAOB including Candidatus Kuenenia and Candidatus Jettenia was the key point for the occurrence of ANAMMOX in the system, and thus, played an important role in the achievement of advanced nitrogen removal.

[Effects of Aeration Strategy on Denitrifying Performance of Activated Sludge Processes in Treating Low-Carbon-Source Municipal Wastewater].

In this study, the effects of aeration strategy on nitrogen removal performance of activated sludge processes in treating low-carbon-source municipal wastewater were investigated. Two aeration strategies (continuous aeration (CA) and intermittent aeration (IA)) were evaluated, and the long-term performance of activated sludge processes employing these strategies in treating wastewater with C/N=3 were analyzed. The results demonstrated that the total nitrogen removal efficiency in CA was 17.92% higher than that in the IA process. Meanwhile, the carbon source utilized in nitrogen removal in CA was 44.29% higher compared with the IA process. Furthermore, the results of 16S rRNA sequencing showed that relative abundances of denitrifying bacteria in CA and IA were 5.86% and 2.06%, respectively, suggesting that the CA process has better denitrification ability when treating low-carbon-source wastewater. In addition, 16S rRNA sequencing gene prediction was utilized to analyze the in-depth mechanisms. The results demonstrated that genes involved in membrane transport, carbohydrate metabolism, and cell composition were more highly expressed in CA. The enhancement of metabolic activity under continuous aeration strengthened microbial carbon source utilization. Therefore, the activated sludge process under continuous aeration was more efficient in treating low-carbon-source municipal wastewater. This study provides ideas for low-carbon-source municipal wastewater treatment.

[Enhanced Nutrient Removal and Microbial Community Structure in a Step-feed A2/O Process Treating Low-C/N Municipal Wastewater].

To resolve the issue of insufficient influent carbon sources in existing municipal wastewater treatment plants (WWTPs) in China, a pilot-scale step-feed A2/O process was used to treat low-C/N (C/N<5) municipal sewage with five different inflow distribution ratios. In this study, the effects of influent flow distribution on the removal efficiencies of chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) were investigated. The results showed that optimal removal efficiencies of 89.41% for COD, 95.30% for NH4+-N, 83.00% for TN, and 90.09% for TP were obtained at an inflow QPA:QAN:QA distribution ratio of 0.1:0.2:0.3. The activated sludge exhibited excellent settleability characteristics, showing a sludge volume index (SVI)<120 mL·g-1 with an average volatile suspended solids (VSS) total suspended solids (TSS) ratio of 0.84 (Phase 5), and no filamentous bacteria bulking occurred during the 120-day experiment. Moreover, the microbial community structure in the oxic zone was detected by high-throughput sequencing. The results demonstrated that excellent nutrient removal and sludge settling performance of the system were closely related to the enrichment of six types of heterotrophic bacteria, four types of denitrifying bacteria, five types of polyphosphate-accumulating organisms (PAOs), and two types of zoogloea and the elimination of three types of filamentous bacteria.

[Partial Nitrification and Denitrification of Low C/N Ratio Sewage Based on Zoning Oxygen and Dissolved Oxygen Control].

Poor nitrogen removal from municipal sewage is mainly due to insufficient carbon source and low C/N ratio. The A2/O pilot plant was established to investigate the accumulation rate of nitrous nitrogen and the removal of nitrogen pollutants by adjusting the ratio of anoxic/aerobic zoning and dissolved oxygen levels in the aerobic zone. The results showed that when DO is 2.0-2.5 mg·L-1, changing the ratio of anoxic to aerobic zoning had little effect on the reaction system, and it was difficult to realize partial nitrification. When DO is 0.5-0.8 mg·L-1, VAnoxic:VAerobic=1:1, this is the best working condition of the system. The accumulation rate of nitrous nitrogen at the end of aerobic zone is stable at more than 62%, and the total nitrogen of effluent is reduced to 9.0 mg·L-1, which can achieve the goal of deep denitrification. Analyzing the apparent activity of nitrifying bacteria, it was found that the SAOR and SNOR (according to N/VSS calculation) were 0.14 g·(g·d)-1 and 0.04 g·(g·d)-1, respectively, under the optimum conditions. The difference between them was more obvious than that in other stages of the experiment, that is, the higher inhibition of NOB activity was the direct reason for the increase of nitrite accumulation rate. Illumina MiSeq sequencing showed that the number of NOB in this stage was significantly lower than that in other stages. Intermittent OUR method was used to analyze the composition of carbon sources at the inlet and outlet of the anoxic zone. The results showed that short-cut nitrification and denitrification could save 27.3% of the carbon sources under the optimal operating conditions. The biodegradable COD consumption in the anoxic zone was 63.6%, which was much higher than that in other stages.

[Substrate Flow by Different Biochemical Activities in the Urban Sewage Network].

In order to investigate the consumption mechanism of organic contaminants in different biological metabolism pathways within an urban sewage network, a pilot-scale system using two kinds of sediments (urban sewage sediment and artificial sediment) was constructed. The pilot system was operated to study the migration and transformation characteristics of COD, methane, nitrate, and sulfate between sediment and sewage. Results showed that the variation of COD in sewage was 170.58 mg·L-1, with change of COD by deposition and bioreaction of 101.53 mg·L-1 and 69.05 mg·L-1, respectively. Due to biological metabolism, the generation of methane in sewers was of 7.39 mg·L-1; the decrease of nitrate and sulfate in sewage was 0.33 mg·L-1 and 21.35 mg·L-1, respectively. Based on our calculations, the consuming concentration of COD was 32.51 mg·L-1for methane generation, 8.04 mg·L-1 for denitrification, and 6.41 mg·L-1for sulfate degradation by sulfate reducing bacteria. The decrease in COD by deposition was responsible for 65.38% of total variation of COD in sewage. The decrease in COD by bioreaction was responsible for 34.62% of total variation in COD. Meanwhile, total variation values of COD for methane generation, denitrification, and sulfate degradation were responsible for 68.01% of COD variation by bioreaction. Deposition was therefore the main pathway for removal of organic contaminants from the sewer system; biochemical activities of methane generation, denitrification, and sulfate degradation also played important roles.

[Ozonation Characteristics of Low Coagulability Organic Matter from the Secondary Effluent of WWTPs].

The aim of this study was to investigate the effectiveness of ozonation on the removal of organic matter with low coagulability from municipal secondary effluent. The results revealed that the removal efficiency of coagulation generally remained quite low. The residual organic matter belonged to low coagulability organic matter. The presence of the ozone increased the removal efficiency of color and UV254 gradually for low coagulability organic matter, whereas DOC had no noticeable change; the efficiencies were 45%, 34%, and 20%, respectively, at a dosage (denoted as O3/DOC) of 1.5 mg·mg-1. It could be concluded that ozone easily reacted with unsaturated organic matter, and the mineralization of organic matter was less effective. In order to further define the variation in organic matter of the secondary effluent, the differences between the relative molecular weight distribution and fluorescence characteristics of coagulation and ozonation with different zone dosages were monitored in this study. The findings showed that coagulation had little effect on organic content. Nonetheless, ozone might have preferentially reacted with high-molecular-weight substances of organic matter with low coagulability and reduced the fluorescence intensity in the humic-like regions significantly. The shift of fluorescence peak was not changed by ozonation. In addition, via X-ray photoelectron spectroscopy (XPS) analysis, it was identified that coagulation could remove carboxylic organic matter. On the other hand, with the increasing ozone dosage (from 0 to 1.5 mg·mg-1), ozone could preferentially react with low coagulability organic matter with aromatic structure, thus the amount of aliphatics increased gradually.

[Characteristics and Mechanism of Hybrid Ozonation-Coagulation Process in Wastewater Reclamation].

Because of the limited dissolved organic matter removal efficiency in conventional pre-ozonation-coagulation process, the hybrid ozonation-coagulation (HOC) process was developed for wastewater reclamation in this study. In this process, coagulation and ozonation could synchronize within a single unit. Compared with the pre-ozonation-coagulation process and traditional coagulation process at the same coagulants dosage, the HOC process exhibited higher treatment efficiency, especially better organic matter removal performance at each pH value, which were 37.96% and 39.66%, respectively. In order to obtain the removal mechanism of dissolved organic matters by HOC process,ozone decomposition at two pH values either with or without AlCl3·6H2O was monitored in this study. The results showed that higher pH and the addition of coagulant could accelerate ozone decay. In addition, para-chlorobenzoic acid (p-CBA) was chosen as the hydroxyl radical (·OH) probe compound to indirectly calculate the ·OH exposure. The results revealed that the HOC process was involved in ·OH reaction and coagulant could promote ozone decomposition due to its enhancing effect on ·OH production during the ozonation process. Furthermore, the ozone depletion occurred more quickly at high pH due to its reaction with hydroxide ions (OH-), leading to the formation of ·OH through a series of chain reactions. Moreover, the effects of tert-butanol, a well-known ·OH inhibitor on ozone decay and p-CBA decomposition were also investigated. The results indicated that ozone depletion and p-CBA decomposition were significantly inhibited by tert-butanol, which further proved that ozone was decomposed into ·OH radicals through chain reactions. In the HOC process, Al-based coagulants and hydrolyzed products could act as catalysts to enhance ozone decomposition into ·OH which is a powerful oxidant to improve the organics removal efficiency.

[Law of Pollutant Erosion and Deposition in Urban Sewage Network].

In order to investigate the scouring and deposition law of pollutants in urban sewer systems, the investigation of sewer systems was carried out in Xi'an. The results showed that the thickness of sediment in the branch pipe and the main pipe varied obviously. At the peak of the drainage, the velocity increased gradually, and the thickness of the pipeline sediment decreased. At the bottom of the drainage trough, the changes of the velocity and the thickness of the pipeline sediment were opposite, with variations of 0-24 mm and 0-12 mm, respectively. And the probability of granular contaminants sedimentation and scouring in sewer systems was high, while the thickness of sediment in sewage main pipe was less than the above mentioned pipes, the variation of which was 0-7 mm. In addition, the sedimentation and scouring in the main pipeline kept relatively balanced and the thickness of sediment remained stable. In order to clarify the relationship between the concentration of pollutants and the flow velocity, a pilot sewer system was established. The effects of different flow rates, which were 0.1, 0.3, 0.6, 0.9, 1.2 m·s-1, respectively, on the contents of carbon (organic), nitrogen and phosphorus in the pipeline were studied. The results showed that with the increase of the flow velocity, the scour intensity increased and the concentration of pollutants in the pipeline also increased sharply. As shown by the monitoring results of the static light scattering particle size analyzer, the carbon organic pollutants in the pipeline were easily adsorbed on the larger particles, while nitrogen and phosphorus pollutants were easily adsorbed on the particles with smaller size. Analysis on the change of the urban sewage pipeline showed, when the flow rate was less than 0.6 m·s-1, the sedimentation of granular pollutants in the sewage was greater than the scouring effect. When the flow velocity was higher than 0.6 m·s-1, the water scouring intensity increased and the scouring action was greater than the sedimentation, meanwhile, the sediments were carried by the water and the thickness of the sediments was reduced. The increase of the organic pollutants in the sewage was bigger than the nitrogen and phosphorus pollutants, so that the existing sewage carbon source was improved.

[Characteristics of Denitrification Inhibiting Sulfate Reducing Process].

In this study, a set of two-stage UASB reactor was used to study the characteristics of denitrification inhibiting sulfate reduction in oil field gathering and transportation system and some high salt wastewater, and the characteristics of granular sludge and microbial characteristics were studied after the stable operation of the process. The results showed that the addition of NaNO2 increased the number of denitrifying bacteria (DNB) from 7.0×103 CFU·(100 mL)-1 to 7.3×105 CFU·(100 mL)-1 and remained stable in the process from start to mature. The competitive inhibition caused by DNB decreased the number of SRB from 8.0×105 CFU·(100 mL)-1 to 7.6×104 CFU·(100 mL)-1. Meanwhile, the sulfate reduction was inhibited, and the inhibition rate increased and finally stabilized to 82%. The study on mass ratio of microbial mass to nitrite effecting on denitrification efficiency showed that the inhibition rate of S2- was the highest, reaching 92%, when the mass ratio was 1200. The inhibition rate of the process could remain at about 92%, with good stability. The particle size and sedimentation rate of granular sludge were measured to determine whether the process conditions were favorable for the formation of granular sludge. The study showed that the denitrifying granular sludge formed was brown, basically ellipsoidal and spherical, with smooth surface and high density. Before the denitrification inhibition, the particle size of granular sludge was 1.0-1.4 mm and the average diameter was 1.17 mm, and after denitrification inhibition, the particle size distribution was 1.2-1.6 mm, the average particle size was 1.21 mm, which indicated that the denitrification inhibition increased the size of granular sludge. The average sedimentation velocity of denitrifying granular sludge was 47.6 m·h-1, which revealed the good settling performance of the granular sludge. The results of PCR-DGGE analysis showed that the denitrification inhibition reduced the number of microbial species from 18 to 14 and the number of dominant species decreased from 4 to 3, indicating the decreasing microbial diversity. The similarity of microbial population before and after nitrification was 62.6% and the population structure changed greatly from SRB to DNB. The number of dominant SRB species decreased from 4 to 2 after denitrification inhibition and the abundance of every species decreased obviously. The main functional bacterial species of the inhibition process was uncultured Sulfurimonas sp., which is a kind of autotrophic denitrifying bacteria. It dominated and competed with SRB for electrons, inhibiting the sulfate reduction and the production of sulfide.