Covingtonmills8004

In order to enhance the removal of NO3--N in the ANAMMOX process, an element sulfur-based autotrophic short-cut denitrification (short-cut S0-SADN) was introduced by adding elemental sulfur to an ANAMMOX continuous flow reactor. The effects of different influent NH4+-N/NO2--N ratios on the nitrogen conversion and NO2--N competitive characteristics in the coupled system were investigated at (33±2)℃ and a pH of 7.8-8.2. The results showed that under different influent NH4+-N/NO2--N ratios (11.3, 11.5, 11, and 11.1), the average total nitrogen (TN) removal efficiency of the coupled system reached 96.78%, 97.21%, 94.68%, and 97.72%, respectively, which were much higher than the highest TN removal efficiency of the ANAMMOX theory (89%). Among them, the stable operation of deep nitrogen removal of the short-cut S0-SADN coupled with ANAMMOX was successfully achieved with an influent NH4+-N/NO2--N ratio of 11 or 11.1. Under the optimal influent NH4+-N/NO2--N ratio of 11.1, the concentrations of influent NH4+-N and NO2--N were 240 mg·L-1 and 265 mg·L-1, respectively, the TN removal rate reached 1.50 kg·(m3·d)-1, and the TN removal efficiency of ANAMMOX and S0-SADN pathways were stable at (95.68±1.22)% and (2.04±0.77)%, respectively. During the entire operational process, ANAMMOX always occupied an absolute advantage in the competition of substrate NO2--N, and the activity of ANAMMOX bacteria (NH4+-N/VSS) was stable at (0.166±0.008)kg·(kg·d)-1.The long-term effects of a decreasing temperature on the nitrification performance, biofilm characteristics, and nitrifier community in a moving-bed biofilm reactor (MBBR) and integrated fixed-film activated sludge (IFAS) system were investigated at various temperatures (20, 15, and 10℃) to explore the adaptability of nitrifying biofilm systems to low temperatures. During the experiment, the extracellular polymeric substances (EPS) in the biofilms increased with decreasing temperature, which resulted in an increased biofilm mass and thickness. As there was only a biofilm phase in the MBBR to remove ammonia, the part of the carriers in the MBBR at 10℃ became plugged, which partially led to a deterioration in the effluent water quality. This indicated that the IFAS system was more adaptable to low temperatures than was the MBBR. Meanwhile, the results for the nitrifier activities showed that, although the nitrification contribution rate of the suspended phase in the IFAS system always dominated during the experiment, that of the fixed phase with regards to the ammonia uptake rate (AUR) gradually increased from 30.72% at 20℃ to 39.85% at 10℃. This indicated that the biofilm played an enhanced role in nitrification in the IFAS system. #link# Moreover, the qPCR results revealed that the nitrifier copies of the number of biofilms increased slightly with decreased temperature, and coincided with an increase in biomass, which partially compensated for the decreased nitrification activity. These findings provide a theoretical basis for the application of the biofilm systems to wastewater treatment.As an important part of biological aerated filters (BAFs), porous fillers are key to the effectiveness of BAF wastewater treatment. At present, there are many types of fillers, but the influence of the surface physical and chemical properties on biofilm formation is unclear, and how to compare and select the best biological filler remains a difficult problem in BAF engineering applications. In this study, the physical and chemical characteristics of several porous biological fillers that are commonly used in BAFs were studied, and the correlation between their physical/chemical properties and the biofilm attachment and enzyme activity of the biofilm on the filler was investigated. The results showed that the sponge filler could easily absorb sludge, but also clogged easily and the overall biofilm activity was not high. The three-dimensional hollow filler had a low surface-adsorbed biomass, but the specific surface area was large and the surface attachment growth biofilm activity was relatively strong. Ceramsite had a good hydrophilicity and high surface roughness, and the zeta potential was the most positive. Moreover, microorganisms easily attached and grew, it had the strongest sludge adhesion performance, and the best biofilm activity. link2 According to a redundancy analysis (RDA), the main factor affecting the biomass on the surface of the fillers was the zeta potential, whereas the main factors affecting the surface sludge activity of the fillers was the clearance rate. According to the removal load of NH4+-N by six groups of reactors, the removal load of NH4+-N by ceramsite was the largest [68 g·(m3·d)-1], and was followed by volcanic rocks [67 g·(m3·d)-1]. Combined with the above factors, ceramsite was determined to be the most suitable filler for BAF.The interaction between microplastics, heavy metals, and antibiotics can lead to combined pollution, which could result in greater environmental damage. The pathway and mechanism of the interaction between microplastics, heavy metals, and antibiotics are the preconditions for evaluating the associated environmental risk; however, these are not well understood. As probe sorbates, the sorption behaviors of copper ions (Cu2+) and tetracycline (TC) on two microplastics [high density polyethylene (HPDE) and general-purpose polystyrene (GPPS)] in aqueous solution were investigated and the welding theory with relevant experimental results were discussed. The adsorption capacity of HDPE was greater than that of GPPS in a single Cu solution, whereas the reverse situation occurred in a single TC solution. Moreover, the adsorption capacity of the microplastics in a Cu2+-TC binary solution was larger than that in the single solutions. The pseudo-second-order kinetic models to describe the adsorption process were reasonabincreasing the temperature was unfavorable for the adsorption process. Cu2+ and TC could produce a synergistic effect under the conditions of coexistence. The formation of complexes and bridging make Cu2+ and TC more easily adsorbed by microplastics.Based on the principle of self-assembly, graphene oxide, chitosan, and FeCl3·6H2O were mixed to prepare graphene oxide-chitosan coated iron-composite particles (Fe@ GOCS). Batch static experiments were carried out to investigate the kinetic and thermodynamic characteristics of As(Ⅲ) adsorption, and to identify the adsorption mechanism. Results showed that the iron on the GOCS was mainly in the form of α-FeO(OH). The As(Ⅲ) adsorption capacity increased with decreasing pH, and the highest adsorption capacity occurred at pH 3. After approximately 45 h, As(Ⅲ) adsorption reached equilibrium under the conditions of pH 3 and a temperature of 298.15, 308.15, and 318.15 K. link3 The maximum adsorption capacity was 289.4 mg·g-1 for an optimal dosage of adsorbents of 1.0 g·L-1. After five times of repeated adsorption-desorption, the adsorption capacity increased slightly. T0070907 showed that ΔGθ0, thus indicating that As(Ⅲ) adsorption on Fe@GOCS was a spontaneous, endothermic, and entropy-increasing reaction, and that a higher temperature was more favorable for As(Ⅲ) adsorption. The pseudo-second-order model provided a good fit of the As(Ⅲ) adsorption kinetics for Fe@GOCS. Compared to the Langmuir isotherm, As(Ⅲ) adsorption experimental data fitted better to the Freundlich and Sips models. In combination with the characterization results, it was found that ion exchange and surface complexation were the main mechanisms of As(Ⅲ) removal from aqueous solution using Fe@GOCS.The Taihu Lake plain is a highly urbanized region in China with many water-related environmental problems. Although point-source pollution has been effectively controlled by government legislation, urban surface runoff pollution is still a major issue. Different types of urban communities were selected for rainfall runoff experiments. According to the monitoring data of rainfall events, multiple methods were used to analyze the characteristics of surface runoff pollution and estimate the pollution load for different types of communities. The results indicated that surface runoff from urban communities reduced the river water quality. Certain degrees of the 'first flush' effect occurred in different types of urban communities. The surface runoff pollution in the commercial residential community was weaker than that in commercial and private residential communities; however, the first flush occurred more frequently in the commercial residential community. Holding back 30% of the surface runoff could effectively improve the runoff water quality in commercial and private residential communities as well as the commercial residential community with restaurants. In the commercial residential community, 25% of surface runoff should be held to improve runoff water quality effectively. The loads of pollutants, especially nitrogen and phosphorus, in urban communities in the Taihu Lake basin were higher than those in other regions in China. This research can assist with the reduction of surface runoff pollution in highly urbanized communities.To comprehend the runoff load of nitrogen (N) and phosphorus (P) and the impact on the receiving river in an agricultural area with an intensive orchard plantation and a longitudinal ridge and furrow morphology in the Three Gorges Reservoir Area, the runoff and N and P concentrations were dynamically monitored in a typical citrus orchard catchment in Wanzhou Country, Chongqing, China. The results showed that the nutrient concentration in runoff water from the intensive citrus planting catchment was very high. The average annual event mean concentrations (EMC) were 9.31 mg·L-1 for total nitrogen (TN), 8.11 mg·L-1 for dissolved nitrogen (DN), 5.66 mg·L-1 for nitrate nitrogen (NN), 0.51 mg·L-1 for ammonium nitrogen (AN), 0.87 mg·L-1 for total phosphorus, 0.56 mg·L-1 for solved phosphorus (DP), and 0.32 mg·L-1 for particulate phosphorus (DP). In addition, the annual loss loads were 13.43, 12.20, 8.77, 0.75, 1.26, 0.84, and 0.42 kg·(hm2·a)-1 for TN, DN, NN, AN, TP, DP, and PP, respectively. The annual average concannual TN and TP loss loads, respectively. The DN and DP were the main forms of nitrogen and phosphorus losses from the intensive citrus orchard with a longitudinal ridge and furrow morphology. Meanwhile, the catchment showed a significant first-flush phenomenon during a typical rainfall event, with a total of 58.0%, 57.0%, 58.5%, 79.0%, 62.0%, 63.5%, and 60.0% of the mass of TN, DN, NN, AN, TP, DP, and PP in the initial 20% of the runoff, respectively. Hence, controlling the surface runoff at the early runoff stage plays an important role in reducing nutrient losses.Due to the vulnerability of karst hydrological systems, nitrate pollution in karst groundwater has become a global common and serious environmental problem. In order to ensure drinking water safety, it is very important to accurately identify groundwater nitrate sources. The groundwater hydrochemistry and δ15N-NO3- and δ18O-NO3- isotopes were analyzed in samples taken from a suburb of Chongqingthe Longfeng karst trough-valley, which is mainly affected by agricultural activities, and the Longche karst trough-valley, which is primarily affected by urbanization. The IsoSource model was then used to quantify the groundwater nitrate sources. The results showed that① The NO3- concentration in groundwater ranged from 19.31 mg·L-1 to 37.01 mg·L-1(mean of 28.21 mg·L-1) in the Longfeng karst trough-valley, and from 2.15 mg·L-1 to 27.69 mg·L-1(mean of 10.31 mg·L-1) in the Longche karst trough-valley. The groundwater NO3- concentration exhibited an obvious seasonal variation in both valleys. ② The δ15N-NO3- and δ18O-NO3- isotopes in groundwater in the Longfeng karst trough-valley ranged from 3.