Pulsed pumping process optimization using a potential flow model

A computational model is applied to the optimization of pulsed pumping systems for efficient in situ remediation of groundwater contaminants. In the pulsed pumping mode of operation, periodic rather than continuous pumping is used. During the pump-off or trapping phase, natural gradient flow transports contaminated groundwater into a treatment zone surrounding a line of injection and extraction wells that transect the contaminant plume. Prior to breakthrough of the contaminated water from the treatment zone, the wells are activated and the pump-on or treatment phase ensues, wherein extracted water is augmented to stimulate pollutant degradation and recirculated for a sufficient period of time to achieve mandated levels of contaminant removal. An important design consideration in pulsed pumping groundwater remediation systems is the pumping schedule adopted to best minimize operational costs for the well grid while still satisfying treatment requirements. Using an analytic two-dimensional potential flow model, optimal pumping frequencies and pumping event durations have been investigated for a set of model aquifer-well systems with different well spacings and well-line lengths, and varying aquifer physical properties. The results for homogeneous systems with greater than five wells and moderate to high pumping rates are reduced to a single, dimensionless correlation. Results for heterogeneous systems are presented graphically in terms of dimensionless parameters to serve as an efficient tool for initial design and selection of the pumping regimen best suited for pulsed pumping operation for a particular well configuration and extraction rate. In the absence of significant retardation or degradation during the pump-off phase, average pumping rates for pulsed operation were found to be greater than the continuous pumping rate required to prevent contaminant breakthrough.     

Phytoextraction of cadmium and zinc from arable soils amended with sewage sludge using Thlaspi caerulescens: development of a predictive model

The objectives of this study were to assess the potential for using Thlaspi caerulescens as a phytoextraction plant and develop a user-advice model, which can predict the frequency of phytoextraction operation required under prescribed conditions. Pot and field trials were conducted using soil collected from a dedicated sewage sludge disposal facility. Soil amendments (sulphuric acid, potassium chloride and EDTA) intended to increase Cd solubility were also tested. Predictive models of Cd and Zn uptake were developed which were able to reproduce the observed pH-dependence of Cd uptake with an apparent maximum around pH 6. Chemical treatments did not significantly increase the uptake of Cd. The periodic use of phytoextraction with T. caerulescens to maintain soils below statutory metal concentration limits, when modern sewage sludges are repeatedly applied, seems very attractive given the non-intrusive and cost-effective nature of the process. The major limitations lie with the large-scale husbandry of T. caerulescens.     

微生物强化修复盐渍化石油污染土壤研究＊

采集东营地区石油污染土壤,进行微生物修复实验研究。考察投加复合菌株CM-13是否能够加速生物修复进程以及土壤中石油污染物质降解的影响因素。石油污染土壤经过90 d的处理,在含水量一定的前提下,复合菌株CM-13对于石油污染物质的加速降解作用显著,当复合菌株CM-13接种量为土壤质量的10%时修复效果较好。微生物的生长与营养盐的量存在最佳匹配值,土壤中氮的最佳含量为0.20%,磷的最佳含量为0.05%。实验中随着麦糠投加量的增大,石油类的降解率逐渐增大,当麦糠量为土壤体积分数的25%时,对土壤的修复效果最好。     

两种铁改性生物炭对微碱性砷镉污染土壤的修复效果

改性生物炭作为良好的重金属钝化剂,已被广泛应用于环境修复.为探究不同改性方法对生物炭钝化土壤砷-镉(As-Cd)的影响,采用共沉淀法和浸渍热解法制备铁改性生物炭,通过吸附试验和土壤培养试验,对生物炭性质、吸附As-Cd以及钝化土壤As-Cd的能力进行分析.结果表明,两种改性方法均可提高生物炭铁含量和零电荷点,且共沉淀法制备的铁改性生物炭(FeBC-1)负载的铁矿物主要为Fe₃O₄、 FeO(OH)和γ-Fe₂O₃等,而浸渍热解法制备的铁改性生物炭(FeBC-2)主要为α-Fe₂O₃和γ-Fe₂O₃等铁氧化物.FeBC-1对As和Cd均展现出很强的吸附去除能力,去除率达21.40%～34.14%,可显著促进土壤中非专性吸附态As向残渣态As转化,而FeBC-2仅对As具有较好的吸附效果.BC、 FeBC-1和FeBC-2对Cd的吸附能力与自身的阳离子交换量(CEC)呈正比,其中,BC对Cd的吸附去除效果优于FeBC...     

3种氧化剂对焦化场地多环芳烃的修复效果与土著微生物的响应关系

为了探究化学氧化对污染土壤修复过程土著微生物生理生态功能的影响,以焦化场地多环芳烃（PAHs）污染土壤为实验对象,研究了高锰酸钾、过硫酸钠和臭氧这3种氧化剂在不同液固比条件下对PAHs的修复效果和土著微生物的响应关系.结果表明,该焦化场地土壤ΣPAHs含量为679.1 mg·kg^-1,高锰酸钾和过硫酸钠投加量为1%时,液固比为6：1条件下ΣPAHs（16种PAHs）的去除率最高,分别为96.9%和95.7%,而臭氧剂量为72 mg·min^-1、液固比为8：1时ΣPAHs的去除率（82.3%）最高;不同液固比条件下低环PAHs （3~4环）的去除率高于高环PAHs （5~6环）,去除率最高的是菲和二氢苊;而对于高环的苯并[a]芘,仅高锰酸钾对其去除效果较优,去除率达到97.4%;微生物数量分析表明,土壤微生物数量经高锰酸钾处理后骤降,由10⁸ copies·g^-1降至10⁵ copies·g^-1,而过硫酸钠和臭氧处理变化不明显,数量级未发生显著变化;微生物群落结构分析表明,污染原土中Proteobacteria占绝对优势,相对丰度为99.5%,高锰酸钾和过硫酸钠处理后微生物多样性显著增加,多种能够降解PAHs的微生物（如Ralstonia和Acinetobacter等）相对丰度大幅提高;微生物代谢功能路径分析表明,化学氧化处理增加了PAHs降解菌的相对丰度,提高了有机物代谢能力.总体而言,液固比为6：1时高锰酸钾处理会显著改变土著微生物数量,微生物群落结构和PAHs降解微生物相对丰度.     

傍河型水源井氨氮阻断与去除工程设计案例分析

针对沈阳市傍河型水源地的氨氮(NH+4-N)污染问题,通过野外研究区的水文地质调查,在查明研究区NH+4-N污染特征的基础上,结合室内批试验、柱实验和数值模拟,筛选出最佳的NH+4-N去除方案,提出了研究区渗透反应格栅(PRB)构建方案,并成功构建了示范工程尺度的PRB,用以去除地下水中的NH+4-N污染.室内批实验和柱实验表明,利用微生物硝化作用结合沸石的吸附作用去除地下水中NH+4-N是可行的.通过对研究区水质数值模拟,发现构建有一定弧度的PRB能最大限度的保护水源井.在PRB的构建过程中,利用高压旋喷技术和旋挖技术解决了大深度(30 m)PRB的构建问题,且PRB建成运行监测表明,示范工程尺度的PRB能有效阻断和去除地下水中NH+4-N.     

农村环境连片整治的模式和技术研究——以新疆为例

文章以农村生活污染-生活垃圾、生活污水、畜禽粪便为分析对象,在传统的村庄划分的基础上（划分为远郊村和近郊村）,根据新疆独特的自然环境、村庄分布和经济状况,又将远郊村划分为远郊村中近邻村、远郊村中的散落村两种形式,并针对不同类型的村庄特点,提出了农村生活污染连片整治的模式及技术,为新疆各地农村环境保护工作提供了依据,也为农村环境连片整治工作的进一步推进奠定了基础。     

自然生物膜对水体中磷浓度的影响研究

以BG11营养液为水源,弹性填料为人工基质培养自然生物膜,设计对比实验,研究生物膜对沉积物磷释放的影响及生物膜作用于该过程的主要机制。随着培养时间的延长,水体中各形态磷浓度均有不同程度的上升,并呈现明显的垂直分布特征;生物膜干重呈对数上升（R2=0．9544）,且与水体中的总磷浓度呈负指数相关（R2=0．7192）;生物膜中磷的解析实验中,溶液中正磷酸盐浓度随时间变化呈对数上升（R2=0．8769）。自然生物膜对水体中的磷有较强的吸附能力和去除效果,且主要作用机制是吸附,磷的迁移转化及最终归宿都要受到生物膜的影响。     

Evaluation of remediation process with soapberry derived saponin for removal of heavy metals from contaminated soils in Hai-Pu, Taiwan

The use of a biodegradable natural plant-based surfactant extracted from soapberry is proposed for the remediation of Ni, Cr and Mn from industrial soil site in Hai-Pu, Taiwan. Batch experiments were performed under variation of fundamental factors (saponin concentration, pH, and incubation time) for metal remediation. Removal of Ni and Mn were increased with increasing saponin concentration (0.015-0.150 g/L), whereas the removal of Cr was increased upto 0.075 g/L saponin. The Ni, Cr and Mn were removed significantly (p ≤q 0.05) at near to the neutral and slightly acidic (pH 5 to 8) conditions. Removal efficiency of Ni (99%) from the soil was found to be greater than that of Cr (73%) or Mn (25%) in the presence of saponin at a concentration of 0.150 g/L at pH 5. The removal percentage increased with incubation time where the removal of Ni was faster than that of Cr and Mn. The result indicates the feasibility of eco-friendly removal of heavy metal (Ni, Cr and Mn) from industrial soil by soil washing process in presence of plant derived saponin.     

环境修复中锰氧化物与变价重金属交互作用的研究进展

氧化-还原过程是影响重金属环境行为的重要过程.锰氧化物作为重要的天然氧化剂,通过对变价重金属的氧化还原和吸附作用,影响着其在环境中的形态、生物有效性乃至归趋,具有很高的环境修复潜力和应用价值.近年来对锰氧化物和变价重金属元素的研究主要集中在以下几个方面:生物氧化锰的形成与多铜氧化酶体系的关系;锰氧化物与变价重金属的交互作用的机制及其影响因素,尤其锰氧化物的空间结构和作用位点的影响.目前,锰氧化物在环境修复中的应用主要集中在水环境修复方面,土壤体系及土壤微界面还很鲜见.同时土壤体系中影响锰氧化物与重金属交互作用的因素更多,其过程也更为复杂.本文通过总结锰氧化物与变价重金属交互作用的研究进展,对比不同重金属种类之间反应机制的差别,为更好的理解锰氧化物的环境作用提供基础,也期望能够进一步拓展其在污染环境的修复中的应用范围.