Adsorption of benzene, cyclohexane and hexane on ordered mesoporous carbon

Ordered mesoporous carbon(OMC) with high specific surface area and large pore volume was synthesized and tested for use as an adsorbent for volatile organic compound(VOC)disposal. Benzene, cyclohexane and hexane were selected as typical adsorbates due to their different molecular sizes and extensive utilization in industrial processes. In spite of their structural differences, high adsorption amounts were achieved for all three adsorbates, as the pore size of OMC is large enough for the access of these VOCs. In addition, the unusual bimodal-like pore size distribution gives the adsorbates a higher diffusion rate compared with conventional adsorbents such as activated carbon and carbon molecular sieve. Kinetic analysis suggests that the adsorption barriers mainly originated from the difficulty of VOC vapor molecules entering the pore channels of adsorbents. Therefore, its superior adsorption ability toward VOCs, together with a high diffusion rate, makes the ordered mesoporous carbon a promising potential adsorbent for VOC disposal.     

Investigation on the eco-toxicity of lake sediments with the addition of drinking water treatment residuals

Drinking water treatment residuals(WTRs) have a potential to realize eutrophication control objectives by reducing the internal phosphorus(P) load of lake sediments. Information regarding the ecological risk of dewatered WTR reuse in aquatic environments is generally lacking, however. In this study, we analyzed the eco-toxicity of leachates from sediments with or without dewatered WTRs toward algae Chlorella vulgaris via algal growth inhibition testing with algal cell density, chlorophyll content, malondialdehyde content, antioxidant enzyme superoxide dismutase activity, and subcellular structure indices. The results suggested that leachates from sediments unanimously inhibited algal growth, with or without the addition of different WTR doses(10% or 50% of the sediment in dry weight) at different p H values(8–9), as well as from sediments treated for different durations(10 or 180 days). The inhibition was primarily the result of P deficiency in the leachates owing to WTR P adsorption, however, our results suggest that the dewatered WTRs were considered as a favorable potential material for internal P loading control in lake restoration projects, as it shows acceptably low risk toward aquatic plants.     

Absorption of phosphorus from wastewater by aged refuse excavated from municipal solid waste landfill

Municipal solid waste(refuse) landfill stabilizes as the refuse degrades. After years of biodegradation, the refuse in the landfill ecomes stabilized and aged, which may vary with the local climate, humidity, and composition of refuse placed. In this work, it is found hat the refuse with an age of over 8 years at Shanghai Refuse Landfill has been significantly stabilized and sufficiently aged and is thus uitable for excavation. The 8-year old aged refuse is mechanically screened, and the fine fractions of refuse(aged refuse) with a diameter ess than 2 cm are then used as a biological absorbent for removal of both inorganic and organic phosphorus in livestock wastewater and repared aqueous solution. It is proved that the aged refuse is very effective for the quantitative removal of both types of phosphorus. The bsorption mechanism is proposed. It is considered that phosphorus is firstly absorbed onto the surface of the aged refuse and then used s a substrate for the growth of microorganisms which ultimately leave the aged refuse as sludge.     

A model to determine the lake nutrient standards for drinking water sources in Yunnan-Guizhou Plateau Ecoregion, China

Lake eutrophication (LE) has become an increasingly severe environmental problem recently. However, there has been no nutrient standard established for LE control in many developing countries such as China. This study proposes a structural equation model to assist in the establishment of a lake nutrient standard for drinking water sources in Yunnan-Guizhou Plateau Ecoregion (Yungui Ecoregion), China. The modeling results indicate that the most predictive indicator for designated use-attainment is total phosphorus (TP) (total effect =-0.43), and chlorophyll a (Chl-a) is recommended as the second important indicator (total effect =-0.41). The model is further used for estimating the probability of use-attainment associated with lake water as a drinking water source and various levels of candidate criteria (based on the reference conditions and the current environmental quality standards for surface water). It is found that these candidate criteria cannot satisfy the designated 100% use-attainment. To achieve the short-term target (85% attainment of the designated use), TP and Chl-a values ought to be less than 0.02 mg/L and 1.4 μg/L, respectively. When used as a long-term target (90% or greater attainment of the designated use), the TP and Chl-a values are suggested to be less than 0.018 mg/L and 1 μg/L, respectively.     

Effect of two biogas residues’ application on copper and zinc fractionation and release in different soils

Biogas residue (BR) is widely used as a new green fertilizer in agriculture in China. However, it often contains a high concentration of heavy metals so its application should cause our concern. An incubation experiment was conducted to study the risk of pig biogas residue (PBR) and chicken biogas residue (CBR) application on Liuminying soil (LS) and Yixing soil (YS). The soils were incubated for one, three and six months with 0, 2%, 4% and 6% addition of BRs. According to BCR extraction results, the PBR and CBR applications induced an increase in the concentration of exchangeable fraction of Zn. As for the concentration of exchangeable fraction of Cu, an increase was only observed in the treatments with PBR application. The heavy metal binding intensity also showed a similar trend. With the PBR application, for the LS and YS, the highest concentrations of exchangeable Zn increased 3.6 and 9.5 times, respectively, while the exchangeable Cu was increased by 52.6% and 187.1%. Dissolved organic carbon was the limiting factor for the exchangeable Cu while the exchangeable Zn was controlled by soil pH. PBR presented more agricultural risk than CBR when used as fertilizer. Meanwhile, BRs were more adaptable to LS than YS according to the heavy metal release results.     

Anaerobic ammonium oxidation for advanced municipal wastewater treatment: is it feasible?

Anaerobic ammonium oxidation（ANAMMOX） is a recently developed process to treat ammonia-rich wastewater. There were numerous articles about the new technology with focus on the ammonium-rich wastewater treatment, but few on advanced municipal wastewater treatment. The paper studied the anaerobic ammonium oxidation （ANAMMOX） process with a down flow anoxic biofilter for nitrogen removal from secondary clarifier effluent of municipal wastewater with low COD/N ratio. The results showed that ANAMMOX process is applicable to advanced wastewater treatment with normal temperature as well as ammonia-rich high temperature wastewater treatment. The results indicated that ammonia removal rate was improved by raising the nitrite concentration, and the reaction rate reached a climax at 118.4 mgN/L of the nitrite nitrogen concentration. If the concentration exceeds 118.4 mgN/L, the ANAMMOX process was significantly inhibited although the ANAMMOX bacteria still showed a relatively high reactivity. The data also indicated that the ratio of NO2^- -N：NH4 ＊ -N = 1.3：1 in the influent was appropriate for excellent nitrogen removal. The pH increased gradually along the ANAMMOX biofilter reactor. When the ANAMMOX reaction was ended, the pH was tend to calm. The data suggested that the pH could be used as an indicator to describe the course of ANAMMOX reaction.     

Direct numerical simulation of the motion of circular pollutant particles in Newtonian fluid

An improved implementation of distributed multiplier/fictitious domain method is presented for the direct numerical simulation of particulate flow. The key improvement is to replace a finite-element triangulation for the velocity and a “twice-coarser“ triangulation for the pressure with a rectangular discretization for the velocity and pressure. For code validation, the sedimentation of a single particle in a twodimensional channel was simulated. The results showed that the simulation is independent of the mesh size as well as the time step. The comparison between experimental data and this simulation showed that our code can give a more accurate simulation on the motion of particlesthan previous DLM code. The code was then applied to simulate the sedimentation of 600 particles in a rectangular box. The falling course ispresented and discussed. At the same time, this simulation also demonstrates that the method presented in this paper can be used for solving the initial problems involving a lager number of particles exaclly with computing durations kept at acceptable levels.     

Influential factors of formation kinetics of flocs produced by water treatment coagulants

The growth rate and size of floc formation is of great importance in water treatment especially in coagulation process.The floc formation kinetics and the coagulation efficiency of synthetic water were investigated by using an on-line continuous optical photometric dispersion analyze and the analysis of water quality.Experimental conditions such as alum dosage,pH value for coagulation,stirring intensity and initial turbidity were extensively examined.The photometric dispersion analyze results showed that coagulation of kaolin suspensions with two coagulants(alum and polyaluminium chloride) could be taken as a two-phase process:slow and rapid growth periods.Operating conditions with higher coagulant doses,appropriate pH and average shear rate might be particularly advantageous.The rate of overall floc growth was mainly determined by a combination of hydraulic and water quality conditions such as pH and turbidity.The measurement of zeta potential indicates that polyaluminium chloride exhibited higher charge-neutralizing ability than alum and achieved lower turbidities than alum for equivalent Al dosages.Under the same operating conditions,the alum showed a higher grow rate,but with smaller floc size.     

Toxicity detection of sodium nitrite, borax and aluminum potassium sulfate using electrochemical method

Based on the inhibition effect on the respiratory chain activity of microorganisms by toxicants,an electrochemical method has been developed to measure the current variation of a mediator in the presence of microorganisms contacted with a toxicant.Microelectrode arrays were adopted in this study,which can accelerate the mass transfer rate of an analyte to the electrode and also increase the total current signal,resulting in an improvement in detection sensitivity.We selected Escherichia coli as the testee and the standard glucoseglutamic acid as an exogenous material.Under oxygen restriction,the experiments in the presence of toxicant were performed at optimum conditions(solution pH 7.0,37°C and reaction for 3 hr).The resulting solution was then separated from the suspended microorganisms and was measured by an electrochemical method,using ferricyanide as a mediator.The current signal obtained represents the reoxidation of ferrocyanide,which was transformed to inhibiting efficiency,IC 50,as a quantitative measure of toxicity.The IC 50 values measured were 410,570 and 830mg/L for sodium nitrite,borax and aluminum potassium sulfate,respectively.The results show that the toxicity sequence for these three food additives is consistent with the value reported by other methods.Furthermore,the order of damage degree to the microorganism was also observed to be:sodium nitrite > borax > aluminum potassium sulfate > blank,according to the atomic force microscopy images of E.coli after being incubated for 3 hr with the toxic compound in buffer solutions.The electrochemical method is expected to be a sensitive and simple alternative to toxicity screening for chemical food additives.     

Coagulation efficiency and flocs characteristics of recycling sludge during treatment of low temperature and micro-polluted water

Drinking water treatment sludge, characterized as accumulated suspended solids and organic and inorganic matter, is produced in large quantities during the coagulation process. The proper disposal, regeneration or reuse of sludge is, therefore, a significant environmental issue. Reused sludge at low temperatures is an alternative method to enhance traditional coagulation efficiency. In the present study, the recycling mass of mixed sludge and properties of raw water (such as pH and turbidity) were systematically investigated to optimize coagulation efficiency. We determined that the appropriate dosage of mixed sludge was 60 mL/L, effective initial turbidity ranges were below 45.0 NTU, and optimal pH for DOMs and turbidity removal was 6.5--7.0 and 8.0, respectively. Furthermore, by comparing the flocs characteristics with and without recycling sludge, we found that floc structures with sludge were more irregular with average size growth to 64.7 μupm from 48.1 μupm. Recycling sludge was a feasible and successful method for enhancing pollutants removal, and the more irregular flocs structure after recycling might be caused by breakage of reused flocs and incorporation of powdered activated carbon into larger flocs structure. Applied during the coagulation process, recycling sludge could be significant for the treatment of low temperature and micro-polluted source water.     

老化作用对生物炭钝化白云鄂博矿区碱性土壤中Cd2+的影响

生物炭虽然已经广泛用于酸性和中性土壤重金属污染修复,然而当生物炭应用于碱性土壤中经历不同程度的老化后是否会改变其结构和固定重金属的能力却关注较少.因此,以玉米秸秆为原料制备生物炭,采用冻融和干湿这两种人工加速老化培养和一种短期自然老化方法对生物炭进行老化实验.老化后测定土壤的pH和Cd²⁺的有效态含量、总量和形态,并从土壤中分离生物炭进行表征,探讨老化作用对生物炭钝化矿区碱性土壤中Cd²⁺的影响.结果表明,白云鄂博矿区碱性土壤中添加生物炭处理不具有显著的石灰化效应,冻融和干湿加速老化处理中pH整体呈下降趋势.与对照相比,添加生物炭后Cd²⁺有效态含量降低了19.32%~30.67%,总Cd²⁺含量下降了5.02%~7.18%.老化作用未能显著改变Cd²⁺的形态,但降低了酸可提取态与可还原态的比例,说明生物炭即使经历老化,依然能够长期固定Cd²⁺,这与生物炭老化后含氧官能团和孔隙结构的增加有关.研究可为生物炭在矿区环境中的长期应用提供理论依据.     

麦草浆黑液固形物热解特性及动力学研究

通过热重分析实验和固定床热解实验研究了麦草碱性亚硫酸钠-蒽醌法制纸桨黑液固形物的热解特性和热解产物分布。结果表明:黑液固形物热解过程分为干燥脱水、有机物热解和无机物转化三个阶段,主要失重发生在200～550℃间;在热重分析基础上按一级反应动力学模型得到了黑液固形物热解各阶段的动力学参数;实验条件下,麦草浆黑液固形物固定床热解后约三分之一转化为挥发分,余下为固体残渣。     

Removal of Cu(II) from acidic electroplating effluent by biochars generated from crop straws

The removal efficiency of copper(Cu(Ⅱ)) from an actual acidic electroplating effluent by biochars generated from canola,rice,soybean and peanut straws was investigated.The biochars simultaneously removed Cu(Ⅱ) from the effluent,mainly through the mechanisms of adsorption and precipitation,and neutralized its acidity.The removal efficiency of Cu(Ⅱ) by the biochars followed the order:peanut straw char > soybean straw char > canola straw char > rice straw char a commercial activated carbonaceous material,which is consistent with the alkalinity of the biochars.The pH of the effluent was a key factor determining the removal efficiency of Cu(Ⅱ) by biochars.Raising the initial pH of the effluent enhanced the removal of Cu(Ⅱ) from it.The optimum pyrolysis temperature was 400°C for producing biochar from crop straws for acidic wastewater treatment,and the optimum reaction time was 8 hr.     

以稻草和污泥为碳源硫酸盐还原菌处理酸性矿山排水

以污泥为硫酸盐还原菌(SRB)接种菌群,分别添加等量稻草和乙醇,研究了SRB以不同碳源处理酸性矿山排水(pH=2.5)的过程及不同碳源对硫酸盐还原和重金属去除的影响.结果表明,在无外加中和剂的情况下,污泥中的碱性物质可在反应开始的1 d内迅速中和酸性矿山排水的部分酸度,使反应体系pH值从2.5升至5.4～6.3,利于SRB的生长.污泥中含少量易被微生物分解的有机物,体系中仅含污泥时,SO24-还原率最低(65.9%).添加稻草可促进SO24-还原(79.2%),因为污泥中的水解菌加速稻草分解,为SRB提供相对充足的碳源.添加乙醇为对照试验的体系中SO24-还原率最高(97.9%).含污泥的反应体系Cu2+去除率均高于99%,SRB驯化前Cu2+的去除主要归因于污泥的吸附作用.以稻草和污泥为碳源可实现低成本酸性矿山排水处理,对矿山环境的原位修复有实际意义.     

酸碱性调节对初沉污泥氮磷和有机质释放的影响

在调节pH值分别为3.0和10.0的条件下,与pH值保持原状相对比,研究了15～20℃下初沉污泥水解酸化过程中氨氮、磷酸盐和溶解性COD(SCOD)、碳水化合物、蛋白质和挥发性脂肪酸(VFAs)等有机质组分的释放。结果表明,强酸条件,特别是强碱会抑制氨氮的释放,试验周期结束时,碱性条件氨氮的释放量为1.28 mg/g TS,远小于对比试验(6.97 mg/g TS);磷酸盐的释放量表现为酸性>碱性>对比试验,反应至第4天时各条件下的释放量即趋于稳定,分别为2.47 mg/g TS、1.23 mg/g TS和1.18 mg/g TS;碱性条件下,各有机质组分的释放量大于其他条件,其中总VFAs波动较大,在第8天左右的产生量接近最大值,为201.59 mg COD/g VS,且以乙酸为主,其余组分在较短的时间里接近或达到最大值后保持相对稳定。     

水分条件对生物炭钝化水稻土铅镉复合污染的影响

采用培养试验,探究30% WHC、淹水和干湿交替等3种水分条件下,向Pb和Cd污染水稻土以1%添加量施入水稻秸秆生物炭后重金属的形态变化,为生物炭修复重金属复合污染稻田的水分管理提供科学依据.结果表明,添加生物炭后,淹水和干湿交替可显著提高土壤pH值、可溶性有机碳（DOC）和无定形氧化铁含量（Fe_o）.培养结束后,在添加生物炭的处理中,相较于30% WHC,淹水和干湿交替条件下TCLP提取态Pb含量分别下降31.87%和20.33%,TCLP提取态Cd含量分别下降25.29%和16.07%.淹水条件下弱酸提取态Pb和Cd下降幅度分别为24.78%和20.14%,且弱酸提取态Cd含量随时间逐渐降低.在3种水分条件下,Pb和Cd有效性降低顺序为：淹水 > 干湿交替 > 30% WHC.相关分析结果显示,土壤pH和无定形氧化铁含量均与有效态Pb和Cd呈显著负相关,表明淹水条件下添加生物炭可通过提高土壤pH和无定型氧化铁含量来有效钝化Pb和Cd,具有促进复合重金属污染酸性水稻土中重金属向稳定态转化的协同机制.     

酸碱调节对混合污泥中氮、磷溶出的影响

为了研究不同酸碱调节下混合污泥(初沉池污泥与剩余污泥按约4∶6的比例混合)中氮磷溶出的变化规律,考察了天津市某污水厂的混合污泥在酸性(pH=3.0),碱性(pH=10.0)以及pH值不调节的情况下,在15～20℃水解酸化过程中氨氮(NH4+-N)和磷酸盐(PO43--P)的释放规律。结果表明:对混合污泥进行pH调节可以提高氨氮和磷酸盐的释放量,且混合污泥中氨氮的释放量表现为碱性>对比试验>酸性;磷酸盐的释放量表现为酸性>对比试验>碱性。     

臭氧/活性炭/紫外光联用处理几种高浓度有机废水影响因素

以对硝基苯甲酸废水、鸟嘌呤废水、乙醛废水和乙醇胺废水为例,对臭氧/活性炭氧化去除废水中有机物的效果进行了初步研究,考察了臭氧投加量、pH值和紫外光等因素对臭氧/活性炭催化氧化高浓度有机废水的影响,并在最优条件下,验证了该工艺作为高浓度有机废水预处理手段,在去除废水中COD和提高可生化性(BOD5/COD)等方面的综合效果.结果表明,活性炭作为催化剂与臭氧共同作用,对对硝基苯甲酸废水COD的去除率明显高于单独臭氧氧化和活性炭吸附;臭氧/活性炭氧化对乙醛废水和乙醇胺废水这类短链类有机物降解作用不大,但对硝基苯甲酸废水、鸟嘌呤废水这些含有苯环类、长链类的有机物,去除效率较高;在中性偏碱时,pH的提高有利于COD的去除,但过高pH对COD的降解效果反而有所减弱,pH=9.0是比较合适的;在紫外光催化的条件下,采用臭氧/活性炭氧化工艺处理对硝基苯甲酸废水,COD去除率可达到52%,废水的生化性(BOD5/COD)由原来的0.10提高到0.32,大大提高了废水的可生化性.     

乙酸型顶极群落的内平衡与反馈调节机制研究

通过产酸脱硫反应器处理高浓度硫酸盐有机废水的连续流试验，从“动态”角度考察COD／SO4^2-比改变引起的pH值、氧化还原电位（ORP）、碱度（ALK）和末端产物（VFAs）等的变动及生态因子的叠加效应引发的优势种群变迁，分析了乙酸型顶极群落的稳定性及其发生定向性生态演替的规律，进而阐明了乙酸型顶极群落抵抗环境压力的内平衡与反馈调节机制，并指出乙酸型代谢和乙酸型顶极群落是产酸脱硫生态系统的典型特征。     

碳黑改性TiO_2薄膜光催化剂的稳定性研究

固定化光催化剂的稳定性一直是限制光催化氧化技术实用化的关键因素之一。通过环管型连续流反应器对所研制的碳黑改性TiO2薄膜光催化剂在长期使用中的稳定性进行了研究,探讨了光源、有机物负荷、阴离子对光催化剂稳定性的影响,并对不同负荷下光催化剂表现出的稳定性进行了动力学描述。试验结果表明,该催化剂在254 nm光源和低负荷条件下具有很好的稳定性,在活性艳红X-3B水溶液的光催化降解试验中,4个月内活性保持不变,并且不受水中的SO42-、NO3-以及硬度、碱度的影响。