膨润土研究现状及其作为PRB反应介质的探讨

在阐述膨润土的矿物学特性、类型及其改性方法（包括酸活化、焙烧、无机盐,有机铵盐）的基础上,探讨了其在废水处理、垃圾填埋场和土壤改良中的应用现状,并以膨润土作为反应介质,COD（化学需氧量）、Cr⁶⁺和NH₄⁺为靶污染物,进行垃圾渗滤液对地下水污染的渗透反应格栅（PRB）实验研究,结果表明：pH值和DO（垃圾渗滤液中的溶解氧）对靶污染物的去除效果有一定的影响,且反应介质对COD、Cr⁶⁺和NH₄⁺的去除率分别为53%、51%和53%,此结果说明了以膨润土作为PRB的反应介质是可行的.     

无机改性膨润土防渗层性能研究

通过实验室实验确定2mol/L氯化镁、0.5mol/L硫酸和450℃高温为天然钠基膨润土盐改性、酸改性和高温改性的最佳条件。采用上述3种无机改性方式填装防渗层,就其对垃圾渗滤液中主要污染物去除的有效性和控制垃圾渗滤液渗透的可行性进行研究。实验结果显示:3种无机改性膨润土的吸附能力和容量有所提高;渗透系数可达到1×10-7cm/s以下,可以作为"反应型"防渗层材料;在相同渗透量下,高温改性膨润土对垃圾渗滤液中主要污染物的去除效果最好,其次是酸改性膨润土,盐改性膨润土最差。     

混合PRB介质处理渗滤液污染地下水的可行性研究

反应介质的选择是可渗透反应墙(PRB)系统原位处理污染地下水的一个关键问题。本实验采用两种混合介质A(陶粒与活性炭的混合物)和B(沸石与活性炭的混合物),对修复被渗滤液污染的地下水的可行性进行了研究。结果表明,混合介质A和B对CODCr的平均去除率分别达到了71.8%和63.4%;对NH4 的平均去除率分别为13.5%和58.7%;对重金属的去除,反应介质B则优于A。因此,PRB反应介质的选择要根据污染物的性质而定。     

天然与改性膨润土组合处理难生物降解垃圾渗滤液的实验研究

以北京市阿苏卫垃圾填埋场中晚期渗滤液为研究对象,通过正交实验的方法分析了改性土、原土、明矾、改性土加明矾等的用量及搅拌速度、搅拌时间、静置时间等因素对垃圾渗滤液CODcr去除率的影响。通过对改性土、原土、明矾处理垃圾渗滤液的机理进行分析后,将改性土、原土分别用来处理垃圾渗滤液中可溶性物质中的疏水性物质和亲水性物质,并结合明矾的絮凝作用组合处理垃圾渗滤液。处理后垃圾渗滤液CODcr值从4700mg/L明显下降到839mg/L,CODcr去除率为82.15%,BOD5从700mg/L下降到263mg/L,BOD5去除率为62.43%。有机改性膨润土、明矾、原土组合处理是一种有效的处理垃圾渗滤液方法。     

片沸石、钙基膨润土去除垃圾渗滤液中有害物质的实验研究

以位于北京昌平小汤山的阿苏卫垃圾卫生填埋场渗滤液为研究对象,在不同的环境条件下:酸度(pH=5~9),温度(4℃~30℃),利用片沸石、钙基膨润土去除垃圾渗滤液中有害物质的实验,以化学耗氧量(COD)、氨氮为评价指标,分别探讨片沸石、钙基膨润土的COD、氨氮去除效果与其用量、渗滤液pH、温度、振荡时间的关系。研究表明,在实验条件下,片沸石对COD的最大去除量约为31×10-3,对氨氮的最大去除量约为27×10-3;去除COD、氨氮的最佳条件分别为:片沸石用量20 g/L、pH为5、温度4℃、振荡时间100 min。在实验条件下,钙基膨润土对COD的最大去除量约为63×10-3,对氨氮的最大去除量约为14×10-3;去除COD、氨氮的最佳条件分别为:钙基膨润土用量30 g/L、pH为5、温度4℃、振荡时间100 min。根据实验结果,对片沸石、钙基膨润土去除COD、氨氮的机理主要是氢键、静电作用及离子交换作用。     

可渗透反应墙对重金属离子Pb~(2+)、Cd~(2+)吸附效果的试验研究

以受尾矿库渗滤液重金属离子Pb2+、Cd2+污染的地下水为研究对象,用天然矿物材料红辉沸石与膨润土作为反应渗透墙(PRB)的活性介质填充材料,试验结果表明,膨润土∶红辉沸石=1∶7,PRB渗透系数处于10-4cm/s数量级且随时间下降最为缓慢;PRB对单一组分Pb2+和单一组分Cd2+去除率分别达99.95%和99.995%;但在双组分PRB体系中,重金属离子Pb2+的存在显著地抑制了PRB对Cd2+的吸附作用,优先选择性吸附顺序是Pb2+Cd2+。     

沸石、膨润土去除垃圾渗滤液中有害物质的实验研究

以位于北京昌平小汤山的阿苏卫垃圾卫生填埋场渗滤液为研究对象,在不同的环境条件下,酸度(pH=5～9)、温度(4～30 ℃),进行了沸石、膨润土去除垃圾渗滤液中有害物质的实验[1].     

褐铁矿和白云石对垃圾渗滤液厌氧消化增强作用的初步研究

垃圾渗滤液治理一直是城市生活垃圾卫生填埋场的难题。能否利用矿物-微生物交互作用提高垃圾渗滤液有机污染物厌氧转化的效率是值得研究的问题。本文设置4组厌氧生物反应器(分别为只添加褐铁矿或者白云石、同时添加褐铁矿和白云石以及不添加矿物的空白组),考察添加褐铁矿、白云石对垃圾渗滤液厌氧消化的影响。实验结果表明,厌氧生化反应12 d时,添加了褐铁矿和白云石的反应器中COD去除率均达到80%以上,而空白对照组COD去除率仅为50%;4组反应器中溶液pH值变化表明,矿物的存在提高了溶液的pH值0.5左右;4组反应器中氨氮含量变化不大,也没有表现出明显差异。研究认为褐铁矿或白云石矿物在垃圾渗滤液中有机物的厌氧消化过程中起到了重要促进作用。研究结果为提高垃圾渗滤液厌氧处理效率提供了一个可供参考的方法。     

两种废物材料在地下水环境治理中的应用

实验利用粉煤灰和矿化垃圾两种废物材料作为反应屏障的反应介质用于修复受渗滤液污染的地下水环境。所设计的两个反应器A、B分别填充矿化垃圾和粉煤灰,利用它们的吸附能力、阳离子交换能力以及微生物的作用去除污染质。试验结果表明:A、B两柱COD的去除率最高可达66%和59%,对铵氮的去除率柱A明显优于柱B,最高可达92.7%,并在81%左右保持稳定。另外柱A对硝酸盐氮和亚硝酸盐氮的去除效果也优于柱B。说明矿化垃圾作为反应屏障介质更加经济可行,可以达到以废治废的目的。     

修复石油类污染地下水的PRB反应介质研究

以石油类污染地下水为研究对象,选用颗粒活性炭、草炭土、粒径为1 mm和3 mm的页岩陶粒、泥岩陶粒、高岭土、聚乙烯醇、细砂和白砂等9种材料进行PRB反应介质筛选及其性能研究。筛选实验结果表明,草炭土去除地下水中总石油烃的效果最好;动态吸附实验结果表明,在吸附1 h时,草炭土去除总石油烃已经达到动态平衡;通过热处理改性,草炭土去除石油烃效果得到提高,在130℃、热处理2 h去除石油烃效果最好;颗分后吸附实验结果表明,在粒径2 mm范围内,草炭土吸附效果均十分显著。在此基础上进行吸附石油烃前后草炭土的微观结构观察及理化性质分析。以上研究表明,草炭土作为PRB反应介质处理石油类污染地下水具有良好的应用前景。     

Treatability of landfill leachate by combined upflow anaerobic sludge blanket reactor and aerated lagoon

Continuous upflow anaerobic sludge blanket reactor performs more favorably at the higher organic loading rate than other anaerobic treatment. The treatment of municipal landfill leachate of Shiraz??s city investigated using continuous flow anaerobic reactor and subsequently aerated lagoon. Landfill leachate has chemical oxygen demand of 45,000?C90,000?mg/L and ammonia nitrogen at 1,000?C2,500 and heavy metals that can impact biological treatments. Capacity of anaerobic and aerobic reactors is 10 and 20?L that operated at detention time of 2 and 4?days, respectively. Organic loading rate of upflow anaerobic sludge blanket is between 0.5?C20?g chemical oxygen demand/L/day. Chemical oxygen demand removal efficiencies are between 57?C87, 35?C70 and 66?C94% in the anaerobic, aerobic and whole system, respectively. As the entry, leachate organic loading rate increased from 1 to 20?g/L/day, the chemical oxygen demand removal efficiency reached a maximum of 71% and 84% in the anaerobic reactor and whole system, respectively, at high organic loading rate. Ammonium removal efficiency was about 54% after the aerobic stage.     

Tunisian landfill leachate treatment using <Emphasis Type="Italic">Chlorella</Emphasis> sp.: effective factors and microalgae strain performance

The potential of the autoclaved Tunisian landfill leachate treatment using microalgae (Chlorella sp.) cultivation was investigated in this study. Landfill leachate was collected from Borj Chakir landfill, Tunisia. A full factorial experimental design 2² was proposed to study the effects of the incubation time and leachate ratio factors on the organic matter removal expressed in chemical oxygen demand (COD) and ammoniacal nitrogen (NH₄─N) and on the biological response of Chlorella sp. expressed by the cell density and chlorophyll content. All experiments were batch runs at ambient temperature (25 ± 2 °C). The Chlorella sp. biomass and chlorophyll a concentrations of 1.2 and 5.32 mg L^?1, respectively, were obtained with 10% leachate spike ratio. The obtained results showed that up to 90% of the ammoniacal nitrogen in landfill leachate was removed in 10% leachate ratio spiked medium with a residual concentration of 40 mg L^?1. The maximum COD removal rate reached 60% within 13 days of incubation time indicating that microalgae consortium was quite effective for treating landfill leachate organic contaminants. Furthermore, with the 10% leachate ratio spiked medium, the maximum lipid productivity was 4.74 mg L^?1 d^?1. The present study provides valuable information for potential adaptation of microalgae culture and its contribution for the treatment of Tunisian landfill leachate.     

Remediation of TCE-contaminated groundwater using zero valent iron and direct current: experimental results and electron competition model

The objectives of this study are to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for the remediation of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC) and to investigate the mechanisms responsible for TCE degradation in different ZVI-DC configurations. A series of column experiments was conducted to evaluate the effect of different arrangements of electrodes and ZVI barriers in the column on the TCE removal capacity (RC). In twelve different combinations of ZVI and/or DC application in the test columns, the rate of reductive dechlorination of TCE was improved up to six times with simultaneous application of ZVI and DC compared to that using ZVI only. The most effective arrangement of electrode and ZVI for TCE removal was the column set with ZVI and a cathode installed at the down gradient. Based on the electrokinetic study for the column systems with only DC input, single acid front movement could explain different RCs. An enhanced dechlorination rate of TCE using E2PRB systems, compared to a conventional PRB system, was observed, and is considered to be attributed to more electron sources: (1) external DC, (2) electrolysis of water, (3) oxidation of ZVI, (4) oxidation of dissolved Fe²⁺, (5) oxidation of molecular hydrogen at the cathode, and (6) oxidation of Fe²⁺ in mineral precipitates. Each of these electron sources was evaluated for their potential influencing the TCE RC through the electron competition model and energy consumption. A strong correlation between the quantity of electrons generated, RC, and the energy-effectiveness was found.     

Swelling characteristics of compacted lateritic soil–bentonite mixtures subjected to municipal waste leachate contamination

Compacted soil–bentonite mixtures are finding wide application as buffer material for waste repositories for their favorable self-sealing qualities. The swelling properties of such materials which serve as a measure of their self-sealing capabilities and, thus, the efficiency of the repository in sealing off their contents from the environment are closely related to the chemistry of the leachate that emanate from the wastes. For this reason, the swelling parameters (namely swelling potential and pressure) of compacted lateritic soil–bentonite mixtures under consideration for use as barrier in municipal waste landfill were evaluated. Series of swelling potential and pressure tests were performed using variable content (0–10 %) of bentonite at predetermined optimum moisture content. Soil mixtures were compacted with British Standard Heavy compactive effort and saturated with processed tap water as well as three leachate solutions of varying ionic strength that were generated in active open dump landfills. Experimental results showed that swelling potential based on the free swell together with the maximum swell pressures of compacted soil mixtures measured at equilibrium increased approximately linearly with increase in the amount of bentonite when inundated with processed tap water and the three leachate solutions. On the other hand, these swelling parameters decreased as the ionic strength of the leachate solutions measured by their electrical conductivity increased for the various soil mixtures. These results provide an insight into the swelling behavior and the possible degradation in the efficiency of the proposed lateritic soil–bentonite mixtures in relation to their use as buffer material in waste landfills.     

生活垃圾填埋场防渗浆材配制与成墙工艺研究

为研制出一种低渗透系数并对污染物有一定吸附阻滞作用的浆材,用于城市生活垃圾填埋场渗滤液防渗工程,通过正交试验优选出了以膨润土为主的浆材配方：膨润土20％～30％,水泥15％～25％,粉煤灰20％～25％,纯碱1．0％～1．4％,稀释剂FCLS加量0．35％～0．75％,余之为水．该浆材结石率〉99．6％,固结体28d渗...     

Electro-coagulation treatment of raw and autoclaved landfill leachate with aluminum electrodes: case study of Djebel Chakir (Tunisia)

Landfilling is a common practice worldwide for solid waste management. The leachate generated at landfill sites contains various organic and inorganic pollutants while it should be treated properly. In this study, the electrocoagulation (EC) process was recognized for its simplicity and effectiveness which was used for the treatment of leachate from the Djebel Chakir landfill site in northern Tunisia. In addition, we investigated the effect of microorganisms (e.g., bacteria, fungi, spore) on sludge production by the application of autoclaving treatment on raw leachate. The application of low current density (15 mA/cm²) within 2 h of treatment and using Al-Al electrodes revealed significant improvement of performance when autoclaving was applied. The chemical oxygen demand (COD) and nitrogen removal increased from 39 to 64% and from 13 to 30%, respectively. The sludge volume was reduced from 40 to 10%, and thus, its handling and disposal costs would be significantly decreased. The energy consumption rate was stable after 40 min of treatment at about 0.8 kWh/kg COD removed. Our study shows that removal of microorganisms by autoclaving prior to the EC process is promising for landfill leachate treatment. However, since autoclaving is far from being practical and cost-effective at full-scale plant, research on coupling EC with an alternative disinfecting process might be of great interest.