The electrodes of Ti/SnO_2-Sb_2O_3,Ti/PbO_2 and Ti/SnO_2-Sb_2O_3/PbO_2 are prepared,respectively,by thermal decomposition and electrodeposition,which are characterized by spectral methods.SEM images show that,unlike to the mud crack surface of Ti/SnO_2-Sb_2O_3 electrode made by thermal decomposition,the surface of Ti/PbO_2 electrode made by electrodeposition appears diamond cubic structure.Moreover,the crystal size of PbO_2 decreases markedly when an intermediate layer of Sn-Sb oxides exists between the layers of Ti substrate and PbO_2.The honeycombed corrosion pits appear in the surface of Ti/SnO_2-Sb_2O_3/PbO_2 electrode after electrolyzing 4-chlorophenol for a long period.EDAX and XRD analyses indicate that although the phase transformation of electrode surface does not occur,the contents of the main elements in the electrode surface change with the increase of electrolysis time.Experimental results show that the electrochemical activity of Ti/SnO_2-Sb_2O_3/PbO_2 electrode is higher than that of the electrodes of Ti/SnO_2-Sb_2O_3 and Ti/PbO_2.
Advanced treatment of biological effluent from coking wastewater treatment system (A/O process) was studied by coagulation with Fe2(SO4)3. The effect of pH and dosage was investigated and then the removal mechanism of organic compounds was studied. Organic compounds could be removed effectively at pH of 3~9. Furthermore, high removal efficiency could be achieved under weakly acid condition. The removal efficiency of DOC was 40.1% and the effluent COD was less than 150mg/L at dosage of 400mg/L and at pH of 5. Complexation-precipitation, complexation-adsorption, and adsorption were the main mechanisms for organic compounds removal in the coagulation process. Under different pH conditions, these three mechanisms had different contribution to the removal of organic compounds. Coagulation effectively removed the hydrophobic organic compounds and those compounds with medium molecular weight, whereas, the hydrophilic organic compounds was poorly removed.
According to the effective soil thickness data obtained by remote sensing,different scenarios of soil erosion potential under different soil erosion intensity in the area of upper and middle reaches of Yellow River are studied.The corresponding anti-erosion potential for difierent erosion scenarios is predicted and classified into five levels,including very low,low,medium,high and very high.The results indicate that the anti-erosion potential level in the area of upper and middle reaches of Yellow River is in the interval from very low to high under different soil erosion intensities.Under the condition of medium and strong soil erosion intensity,the anti-erosion potential is in high level.When the erosion is very strong the potential will be reduced to low level and the soil erosion will be serious.If the erosion reaches severe intensity,the situation becomes worse.The dual-index approach based on soil erosion intensity and potential hazard gives the appropriate assessment of anti-erosion potential,which is helpful to the decision-making in planning of water and soil conservation and sustainable development of the Yellow River basin.
The technology of immobilized microorganisms has found wide applications in wastewater treatment. This paper focuses on the major performances of immobilized microorganisms in the coking wastewater in gasworks. The influences of temperature, pH, ammonia-nitrogen and organic materials on performances of immobilized microorganisms were examined through the analysis of inflow and outflow of ammonia-nitrogen, phenol and COD. In addition, the patterns of the immobilized microorganisms were observed, and the immobilized biomass on the carrier was determined by the Kjeldahl-Gunning method. As results, the relevant parameters in the technology design for removal of the pollutants were obtained. It is shown that the immobilized microorganisms have very good performance as temperature ranged 10 -55℃ and pH of 4 - 11. The maximum volume loads are 9.06kg/m3 · d for COD and 1.11 kg/m3 · d for NH4+ -N as effluent COD and NH4+ -N are no more than 100mg/L and 15mg/L, respectively. The average immobilized biornass on the carrier is 32g/L. The comparison of the performances of the immobilized and the dissociated microorganisms shows that the former has significant advantages over the latter in treatment of high ammonia-nitrogen wastewater.
Aerobic granulation and characteristics of aerobic granular sludge were studied in Sequencing Batch Reactor.The reaction process and factors influencing removal rate were also investigated.For the cases with reducing settling time gradually,the activated sludge was cultivated successfully.Most of aerobic granular sludges were made up of cocci and extracellular polymeric substances.Removal rate of COD,Ammonium and TN in SBR is 96%,96% and 80%,respectively.Aerobic granular sludge could be used to treat water which contain COD in 600—1500mg/L and Ammonium under 100mg/L.Moreover the removal rate of TN was decreased with decreasing influent C/N.The suitable pH was 7.22—8.82 when temperature was 20—30℃. Aerobic granular sludge could remove all of Ammonium and Nitrite,some of Nitrate,and 30.30% of COD in advanced treatment of landfill leachate in 6 hours.When aerobic granular sludge was put in landfill leachate over 16 cycles,extracellular polymeric substances increased and some protonema appeard.
Vertical motion of particles was simulated by the Lagrangian method in one-dimensional solid-liquid two-phase flow. The conventional equation was modified by inserting a particle-particle interaction term, which was identified by Bagnold's experimental results. Effects of various forces have been examined under different particle concentrations. The results showed that the vertical sorting patterns are primarily determined by the joint action of inter-particle force and effective gravitational force, whereas the pace towards the steady sorting pattern was affected by Basset force and additional mass force.
Debris flow is noted for its complex material compositions, unusual flow patterns and potential ability to induce serious disasters. Among the different types of debris flows, the water-rock flow is typical and thus has been studied widely around the world. For this kind of specific flow, the total stress is composed of three parts, i.e., the frictional stress, the dispersive stress and the collisional stress. Since the last two parts can be reasonably modeled and the first part is still lack of satisfactory understandings, the determination of the frictional constitutive relation becomes the key to the insight into the mechnism of debris flow. In the present paper, a simple way is introduced by assuming that the frictional stress is part of the total stress for the particles, and the behaviours of debris flow are fully studied by use of varying proportional coefficients reflecting the frictional share in the total ranged between zero and one. In addition, the criterion and differences between the laminated flow and the water-rock flow are also discussed. As indicated in the paper, most of the special characteristics in water-rock debris flows are related to frictional stress. So far, the knowlege to the frictional constitutive relationis is far not enough for us to do quantitative study since each existing relation often include several empirical parameters to be determined and give quite differnt results with varying magnitude orders. In such cases, the present study is particularly useful for the deeper understanding of the effect of frictional stress on debris flows.
Viruses as the most abundant biological entities have drastic impacts on aquatic ecosystems, yet little was known about groundwater virome. To address this knowledge gap, we performed ultra-deep metagenomic sequencing on groundwater samples from 607 monitoring wells throughout China and established the first groundwater virome database (GWVD). The GWVD database substantially expanded known aquifer virosphere, and the vast majority of the vOTUs represented previously unknown viral populations. The GWVD provided comprehensive available resources for future studies on viruses in subsurface environments.
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