一体式膜生物反应器回用处理生活污水

将循环活性污泥系统(Cyclic Activated Sludge System,CASS)与膜过滤技术组合为一体式膜生物反应器(Submerged Membrane Bioreactor,SMBR),研究其用于生活污水回用处理的可行性,对该工艺的适宜运行条件进行了研究.结果表明,水力停留时间(HRT)为4 h、DO在2.0～3.5 mg/L、温度控制在常温、pH在6.5～8.0的运行条件是比较经济高效的.并考察了装置对实际生活污水的处理效果,结果表明出水水质优异,优于中水回用标准(CJ 25.1-89).     

臭氧化对垃圾填埋场后期渗滤液的预处理研究

应用自制微孔扩散式接触反应器,考察了不同pH条件下垃圾填埋场后期渗滤液的臭氧化预处理效果.结果表明,渗滤液初始pH值升高,臭氧利用率增大,垃圾渗滤液中COD、腐殖酸的去除速率加快;当初始pH为10时,经臭氧化处理120 min后,模拟废水的BOD5/COD可从初始的0.17提高到0.36,改善了废水的可生化性,同时渗滤液的色度、浊度、腐殖酸和SS也有较高的去除率.     

危险废物的处理处置措施研究

危险废物因具有毒性、易燃性、腐蚀性、反应性和感染性等多种危害特性,如果暴露于环境中将会对生态环境和人类健康造成很大威胁;所以及时而有效地处理处置危险废物意义极为重大.文章简要地介绍了危险废物的定义及其来源,并指出其对环境和人类造成的危害,总结了我国目前的危险废物处理处置技术的现状,根据我国危险废物污染防治的技术路线和技术政策,分析了危险废物的处置措施,系统地论述了常规危险废物的常用处置方法,从而揭示了我国在危险废物处理处置方面及管理方面的问题,并提出针对危险废物处理处置的对策与建议.     

Mn2NiO4 spinel catalyst for high-efficiency selective catalytic reduction of nitrogen oxides with good resistance to H2O and SO2 at low temperature

Mn-Ni oxides with different compositions were prepared using standard co-precipitation(CP) and urea hydrolysis-precipitation(UH) methods and optimized for the selective catalytic reduction of nitrogen oxides(NO_x) by NH_3 at low temperature.Mn((2))Ni_((1))O_x-CP and Mn_((2))Ni_((1))O_x-UH(with Mn:Ni molar ratio of 2:1) catalysts showed almost identical selective catalytic reduction(SCR) catalytic activity,with about 96% NO_x conversion at 750 C and-99%in the temperature range from 100 to 250℃.X-ray diffraction(XRD) results showed that Mn_((2))Ni_((1))O_x-CP and Mn_((2))Ni_((1))O_x-UH catalysts crystallized in the form of Mn_2NiO_4 and MnO_2-Mn_2NiO_4 spinel,respectively.The latter gave relatively good selectivity to N_2,which might be due to the presence of the MnO_2 phase and high metal-O binding energy,resulting in low dehydrogenation ability.According to the results of various characterization methods,it was found that a high density of surface chemisorbed oxygen species and efficient electron transfer between Mn and Ni in the crystal structure of Mn_2NiO_4 spinel played important roles in the high-efficiency SCR activity of these catalysts.Mn_((2))Ni_((1))O_x catalysts presented good resistance to H_2O or/and SO_2 with stable activity,which benefited from the Mn_2NiO_4 spinel structure and Eley-Rideal mechanism,with only slight effects from SO_2.     

Investigation and assessment of micropollutants and associated biological effects in wastewater treatment processes

Currently, the wastewater treatment plants (WWTPs) attempt to achieve the shifting from general pollution parameters control to reduction of organic micropollutants discharge. However, they have not been able to satisfy the increasing ecological safety needs. In this study, the removal of micropollutants was investigated, and the ecological safety was assessed for a local WWTP. Although the total concentration of 31 micropollutants detected was reduced by 83% using the traditional biological treatment processes, the results did not reflect chemicals that had poor removal efficiencies and low concentrations. Of the five categories of micropollutants, herbicides, insecticides, and bactericides were difficult to remove, pharmaceuticals and UV filters were effectively eliminated. The specific photosynthesis inhibition effect and non-specific bioluminescence inhibition effect from wastewater were detected and evaluated using hazardous concentration where 5% of aquatic organisms are affected. The photosynthesis inhibition effect from wastewater in the WWTP was negligible, even the untreated raw wastewater. However, the bioluminescence inhibition effect from wastewater which was defined as the priority biological effect, posed potential ecological risk. To decrease non-specific biological effects, especially of macromolecular dissolved organic matter, overall pollutant reduction strategy is necessary. Meanwhile, the ozonation process was used to further decrease the bioluminescence inhibition effects from the secondary effluent; ≥ 0.34 g O₃/g DOC of ozone dose was recommended for micropollutants elimination control and ecological safety.     

Arsenic and cadmium removal from water by a calcium-modified and starch-stabilized ferromanganese binary oxide

A new calcium-modified and starch-stabilized ferromanganese binary oxide (Ca-SFMBO) sorbent was fabricated with different Ca concentrations for the adsorption of arsenic (As) and cadmium (Cd) in water. The maximum As(III) and Cd(II) adsorption capacities of 1% Ca-SFMBO were 156.25 mg/g and 107.53 mg/g respectively in single-adsorption systems. The adsorption of As and Cd by the Ca-SFMBO sorbent was pH-dependent at values from 1 to 7, with an optimal adsorption pH of 6. In the dual-adsorbate system, the presence of Cd(II) at low concentrations enhanced As(III) adsorption by 33.3%, while the adsorption of As(III) was inhibited with the increase of Cd(II) concentration. Moreover, the addition of As(III) increased the adsorption capacity for Cd(II) up to two-fold. Through analysis by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR), it was inferred that the mechanism for the co-adsorption of Cd(II) and As(III) included both competitive and synergistic effects, which resulted from the formation of ternary complexes. The results indicate that the Ca-SFMBO material developed here could be used for the simultaneous removal of As(III) and Cd(II) from contaminated water.     

Water regime-nitrogen fertilizer incorporation interaction: Field study on methane and nitrous oxide emissions from a rice agroecosystem in Harbin, China

Water regime and nitrogen (N) fertilizer are two important factors impacting greenhouse gases (GHG) emission from paddy field, whereas their effects have not been well studied in cold region. In this study, we conducted a two-year field experiment to study the impacts of water regime and N fertilizer on rice yields and GHG emissions in Harbin, China, a cold region located in high latitudes. Our results showed that intermittent irrigation significantly decreased methane (CH₄) emission compared with continuous flooding, however, the decrement was far lower than the global average level. The N₂O emissions were very small when flooded but peaked at the beginning of the disappearance of floodwater. The N fertilizer treatments increased CH₄ emissions at low level (75kgN/ha). But both CH₄ and N₂O emissions were uninfluenced at the levels of 150kgN/ha and 225kgN/ha. Rice yields increased under intermittent irrigation and were highest at the level of 150kgN/ha. From our results, we recommended that the intermittent irrigation and 150kgN/ha as the ideal water regime-nitrogen fertilizer incorporation for this area to achieve low GHG emissions without impacting rice yields.     

Adsorption-oxidation of hydrogen sulfide on Fe/walnut-shell activated carbon surface modified by NH3-plasma

Walnut-shell activated carbon(WSAC) supported ferric oxide was modified by non-thermal plasma(NTP), and the removal efficiency for hydrogen sulfide over Fe/WSAC modified by dielectric barrier discharge(DBD) was significantly promoted. The sample modified for10 min and 6.8 k V output(30 V input voltage) maintained 100% H2 S conversion over a long reaction time of 390 min. The surface properties of adsorbents modified by NTP under different conditions were evaluated by the methods of X-ray photoelectron spectroscopy(XPS), Brunauer–Emmett–Teller(BET) analysis and in-situ Fourier transform infrared spectroscopy(FTIR), to help understand the effect of the NTP treatment. NTP treatment enhanced the adsorption capacity of Fe/WSAC, which could due to the formation of micro-pores with sizes of0.4, 0.5 and 0.75 nm. XPS revealed that chemisorbed oxygen changed into lattice oxygen after NTP treatment, and lattice oxygen is beneficial for H2 S oxidation. From the in-situ FTIR result,transformation of the reaction path on Fe/WSAC was observed after NTP modification. The research results indicate that NTP is an effective method to improve the surface properties of the Fe/WSAC catalyst for H2 S adsorption-oxidation.     

Measurement of hydrogen peroxide and organic hydroperoxide concentrations during autumn in Beijing, China

Gaseous peroxides play important roles in atmospheric chemistry. To understand the pathways of the formation and removal of peroxides, atmospheric peroxide concentrations and their controlling factors were measured from 7:00 to 20:00 in September, October, and November 2013 at a heavily trafficked residential site in Beijing, China, with average concentrations of hydrogen peroxide (H₂O₂) and methyl hydroperoxide (MHP) at 0.55 ppb and 0.063 ppb, respectively. H₂O₂ concentrations were higher in the afternoon and lower in the morning and evening, while MHP concentrations did not exhibit a regular diurnal pattern. Both H₂O₂ and MHP concentrations increased at dusk in most cases. Both peroxides displayed monthly variations with higher concentrations in September. These results suggested that photochemical activity was the main controlling factor on variations of H₂O₂ concentrations during the measurement period. Increasing concentrations of volatile organic compounds emitted by motor vehicles were important contributors to H₂O₂ and MHP enrichment. High levels of H₂O₂ and MHP concentrations which occurred during the measurement period probably resulted from the transport of a polluted air mass with high water vapor content passing over the Bohai Bay, China.     

Preparation and properties of chitosan–metal complex: Some factors influencing the adsorption capacity for dyes in aqueous solution

Chitosan–metal complexes have been widely studied in wastewater treatment, but there are still various factors in complex preparation which are collectively responsible for improving the adsorption capacity need to be further studied. Thus, this study investigates the factors affecting the adsorption ability of chitosan–metal complex adsorbents, including various kinds of metal centers, different metal salts and crosslinking degree. The results show that the chitosan–Fe( Ⅲ) complex prepared by sulfate salts exhibited the best adsorption efficiency(100%) for various dyes in very short time duration(10 min), and its maximum adsorption capacity achieved 349.22 mg/g. The anion of the metal salt which was used in preparation played an important role to enhance the adsorption ability of chitosan–metal complex. SO_4~(2-) ions not only had the effect of crosslinking through electrostatic interaction with amine group of chitosan polymer, but also could facilitate the chelation of metal ions with chitosan polymer during the synthesis process.Additionally, the p H sensitivity and the sensitivity of ionic environment for chitosan–metal complex were analyzed. We hope that these factors affecting the adsorption of the chitosan–metal complex can help not only in optimizing its use but also in designing new chitosan–metal based complexes.