A fouling suppression system in submerged membrane bioreactors using dielectrophoretic forces

A novel method was developed to suppress membrane fouling in submerged membrane bioreactors. The method is based on the dielectrophoretic (DEP) motion of particles in an inhomogeneous electrical field. Using a real sample of biomass as feed, the fouling-suppression performance using DEP with different electrical field intensities (60–160 V) and different frequencies (50–1000 Hz) was investigated. The fouling-suppression performance was found to relate closely with the intensity and frequency of the electrical field. A stronger electrical field was found to better recover the filtrate flux. This is because of a stronger DEP force acting on the biomass particles close to the membrane's surface. Above an intensity and frequency value of 130 V and 1 kHz, respectively the permeate flux was reduced due to an electrothermal effect.     

Changes in nitrogen budget and potential risk to the environment over 20 years (1990–2010) in the agroecosystems of the Haihe Basin,China

The nitrogen balance can serve as an indicator of the risk to the environment of nitrogen loss from agricultural land. To investigate the temporal and spatial changes in agricultural nitrogen application and its potential threat to the environment of the Haihe Basin in China, we used a database of county-level agricultural statistics to calculate agricultural nitrogen input, output, surplus intensity, and use efficiency. Chemical fertilizer nitrogen input increased by 51.7% from 1990 to 2000 and by 37.2% from 2000 to 2010, concomitant with increasing crop yields. Simultaneously, the nitrogen surplus intensity increased by 53.5% from 1990 to 2000 and by 16.5% from 2000 to 2010, presenting a continuously increased environmental risk. Nitrogen use efficiency decreased from 0.46 in 1990 to 0.42 in 2000 and remained constant at 0.42 in 2010, partly due to fertilizer composition and type improvement. This level indicates that more than half of nitrogen inputs are lost in agroecosystems. Our results suggest that although the improvement in fertilizer composition and types has partially offset the decrease in nitrogen use efficiency, the environmental risk has still increased gradually over the past 20 years, along with the increase in crop yields and nitrogen application. It is important to achieve a better nitrogen balance through more effective management to significantly reduce the environmental risk, decrease nitrogen surplus intensity, and increase nitrogen use efficiency without sacrificing crop yields.     

Enhanced U(VI) bioreduction by alginate-immobilized uranium-reducing bacteria in the presence of carbon nanotubes and anthraquinone-2,6-disulfonate

Uranium-reducing bacteria were immobilized with sodium alginate, anthraquinone-2, 6-disulfonate (AQDS), and carbon nanotubes (CNTs). The effects of different AQDS-CNTs contents, U(IV) concentrations, and metal ions on U(IV) reduction by immobilized beads were examined. Over 97.5% U(VI) (20 mg/L) was removed in 8 hr when the beads were added to 0.7% AQDS-CNTs, which was higher than that without AQDS-CNTs. This result may be attributed to the enhanced electron transfer by AQDS and CNTs. The reduction of U(VI) occurred at initial U(VI) concentrations of 10 to 100 mg/L and increased with increasing AQDS-CNT content from 0.1% to 1%. The presence of Fe(III), Cu(II) and Mn(II) slightly increased U(VI) reduction, whereas Cr(VI), Ni(II), Pb(II), and Zn(II) significantly inhibited U(VI) reduction. After eight successive incubation-washing cycles or 8 hr of retention time (HRT) for 48 hr of continuous operation, the removal efficiency of uranium was above 90% and 92%, respectively. The results indicate that the AQDS-CNT/AL/cell beads are suitable for the treatment of uranium-containing wastewaters.     

Predicted no-effect concentrations for mercury species and ecological risk assessment for mercury pollution in aquatic environment

Mercury(Hg) exists in different chemical forms presenting varied toxic potentials. It is necessary to explore an ecological risk assessment method for different mercury species in aquatic environment. The predicted no-effect concentrations(PNECs) for Hg(Ⅱ) and methyl mercury(Me Hg) in the aqueous phase, calculated using the species sensitivity distribution method and the assessment factor method, were 0.39 and 6.5 × 10-3μg/L, respectively. The partition theory of Hg between sediment and aqueous phases was considered, along with PNECs for the aqueous phase to conduct an ecological risk assessment for Hg in the sediment phase. Two case studies, one in China and one in the Western Black Sea, were conducted using these PNECs. The toxicity of mercury is heavily dependent on their forms,and their potential ecological risk should be respectively evaluated on the basis of mercury species.     

膨润土负载纳米铁的改性及对水中As(Ⅴ)的吸附

用十六烷基三甲基溴化铵(CTMAB)对膨润土负载纳米零价铁(Bent-n ZVI)进行表面改性,得到表面改性膨润土负载纳米铁(Bent-n ZVI)/CTMAB。通过SEM、Zeta电位和中位径d(50)分析,与膨润土(Bent)、改性膨润土(CTMAB-Bent)、Bent-n ZVI进行了对比,结果表明:相比Bent-n ZVI,(Bent-n ZVI)/CTMAB中的纳米铁颗粒更为分散且呈链状分布,d(50)仅为5.21μm,并且Zeta电位为+0.65 m V,更易静电吸引和吸附阴离子As O43-。4种材料的除砷结果亦表明其中(Bent-n ZVI)/CTMAB去除率最高,达到了93.9%。光电子能谱(XPS)分析表明(Bent-n ZVI)/CTMAB的除砷产物中只有As(Ⅴ),并不存在其还原态As(Ⅲ),说明(Bent-n ZVI)/CTMAB是通过吸附作用去除As(Ⅴ)。     

基于DEA的水泥脱硝清洁生产方案可行性评价

水泥工业是典型的高能耗、高污染过程工业,近年来水泥行业的快速发展带来了严重的资源、能源问题,并排放大量NOx,水泥行业已成为我国NOx重点减排领域之一。水泥行业进行清洁生产审计,实施相应清洁生产案(cleaner production programs,CPPs),是节能减排的有效途径。然而,我国目前所使用CPPs评价方法存在一定的缺陷,对技术可行方案的评价割裂为环境与经济两部分,不能做出有效选择,无法满足清洁生产审核工作的需求。引入数据包络分析模型(data envelopment analysis,DEA)用于CPPs评价,建立了扩展超效率模型S-E’,以水泥行业脱硝技术为例,将方案产生二次污染物NH3作为非期望输出、减少的NOx排放量作为输出,建立清洁生产方案超效率DEA评价指标体系,将方案输入、输出数据引入S-E’模型分析各脱硝方案环境与经济的相对综合效率,根据评价结果排序,能够选取最优清洁生产方案,为CPPs评价及筛选提供了一定技术支持。     

钢铁工业氮氧化物污染防治途径研究

针对钢铁工业氮氧化物减排的紧迫形势,首先介绍了钢铁工业氮氧化物主要排放源,提出了烧结工序和自备电厂是氮氧化物排放的主要污染源,其烟气中氮氧化物控制是钢铁企业氮氧化物减排的重点;其次对钢铁工业氮氧化物生成机理,热力型、燃料型、快速型进行了分析;在此基础上,总结了钢铁工业烧结、自备电厂、焦化、炼铁、轧钢工序氮氧化物污染防治技术途径,为钢铁工业进一步开展氮氧化物减排工作提供了技术支撑.     

微波在废树脂中的穿透厚度研究

通过对不同功率微波在不同规格钢桶中对不同含水率的树脂中的穿透厚度的研究可知,微波在树脂中的穿透厚度主要与树脂自身含水率有关,与钢桶的规格尺寸也有一定的关系,而微波功率的影响则可基本忽略不计;对于含水率50％左右的树脂,微波在12L钢桶中的穿透厚度是130 mm;在200L钢桶中的穿透厚度是70mm.该研究成果对微波干燥工艺的具体参数的选取和扩大规模台架装置的设计研究等有重要意义.     

An in-depth view of climate change:addressing climate change while making a transition on the development mode

While fossil fuels greatly contribute to human society,they pose great challenges to natural resources,the environment,and climate change.Developed countries,like the United States,formulated strategic measures to ensure their sustainable development and leading positions in the world.These measures include new green policies,development of shale gas,revitalization of nuclear power,energy independence,reindustrialization,and new low-carbon development based on a combination of Internet technology and renewable energy.Developing countries are also trying to introduce balanced strategies of poverty alleviation and sustainable development.Globally,industrial civilization is being transformed to ecological civilization and green,low-carbon development is a global trend.Addressing climate change provides new strategic factors to further this development.China should take substantial actions to realize sustainable development in a new road:China is in the critical stage of changing its development mode,so it is vital to choose an appropriate development path.This extensive development comes at the high price of consuming too much resources and scarring the environment.Mitigation and adaptation strategies for addressing climate change can help the transition of development.Based on the analysis of the development data of developed countries,the author introduces the concept of"two-type developed countries"with an understanding that not all developed countries must take the same development mode.He also holds the view that China should achieve modernization in a more energy-saving and more carbon-efficient manner compared with that of two-type developed countries.An analysis of"two competitions"that China is facing shows that changing the developing mode is urgent and China should grasp this opportunity in the next five to ten years,which is a key period for this transition.This paper discusses the low-carbon development goals and the three-step process.Low-carbon development does not necessarily restrict economic development.It,however,can expedite the transition of the development mode and this is a low-carbon and green development path.Transition of the development mode includes implementation of China’s green and low-carbon energy strategies,low-carbon society construction,development of agriculture and forestry,garbage sorting and utilization,innovation of urbanization,etc.Improvement of national infrastructure construction includes water safety,environment and climate monitoring system,intelligent energy web,basic database,etc.Addressing climate change can significantly improve the nation’s basic research level.In summary,it mitigates backward production capability,extensive development,and environmental damage while promoting technological advancement,scientific development,and ecological civilization.     

运动对急性暴露于2,3,7,8-四氯二苯并二恶英大鼠肝组织酶活性的影响

为了研究运动对2,3,7,8-四氯二苯并二恶英(2,3,7,8-TCDD)急性暴露大鼠肝组织酶活性的影响,将40只雄性Wistar大鼠随机分为正常对照组(NC)、染毒组(NT)、运动对照组(EC)、运动染毒组(ET)。染毒组(NT组与ET组)腹腔注射10μg·kg-1(以单位体重计)的TCDD,对照组(NC组与EC组)腹腔注射等量的玉米油;NT、NC组静养4周,ET、EC组运动(尾部负重5%游泳30分钟)4周。4周后,称重并宰杀大鼠,分离肝组织,称重后-80℃保存待测7-乙氧基异吩恶唑酮脱乙基酶(EROD)、7-乙氧基香豆素-O-脱乙基酶(ECOD)及芳香烃羟化酶(AHH)的活性。将数据进行多因素方差分析(MAVONA)处理,结果表明,染毒可降低大鼠体重,增加肝湿重和肝相对重量、增加EROD、ECOD活性;运动可增加大鼠肝相对重量、增加AHH的活性;染毒后运动可降低EROD、ECOD的活性。结论:急性10μg·kg-1(以单位体重计)TCDD染毒后4周可增加大鼠肝相对重量;4周的运动能有效降低TCDD对EROD、ECOD活性的激活作用。