负载型Mn/RE催化剂制备条件对其电催化功效的影响

采用Mn/RE多相催化电解氧化方法深度处理垃圾渗滤液,制备了负载型Mn/RE氧化物双活性组分催化剂,研究了Mn/RE负载型催化剂的制备条件(不同组分的浓度配比,焙烧温度,催化剂载体材料)对电多相催化氧化降解垃圾渗滤液中有机物的影响,确定催化剂的适宜制备条件研究结果表明:催化剂中Mn 与稀土组分复合其催化活性好于单一组分,其中以Ce+ Mn制备的催化剂效果最好;浸渍液金属离子质量分数Mn为3％、Ce为1％,焙烧温度为550℃.以γ-Al2O3为载体时所制得的催化剂活性较高并且该催化剂的性能稳定,经6次使用后仍具有一定的催化活性.对于COD为533mg/L的渗滤液生物处理出水的电解氧化降解,采用催化剂后,COD去除率由26.9％提高到71 76％,可有效降低COD.     

累托石/聚丙烯酸(钠)-丙稀酰胺吸水保水复合材料的制备及性能

采用焙烧-磁选法、酸洗提纯法、煅烧法均能有效减少湖北钟祥累托石粘土中的黄铁矿.实验用累托石粘土中黄铁矿含量为4.37%, 硫含量为2.32%.采用焙烧磁选法, 温度300℃、时间2.0h、二次磁选后, 累托石粘土中硫含量降为0.52%;酸洗法, 酸液浓度60%、时间1.0h、温度60℃时, 硫含量为0.57%;煅烧法, 当温度550℃、时间为0.5h时, 硫含量为0.78%.研究发现所得粘土矿物对聚合复合法制备累托石/聚丙稀酰胺-丙烯酸(钠) 吸水保水复合材料的阻聚作用不明显, 且不影响后续聚合反应最高硫含量约为0.78%.在65~70℃反应条件下, 含煅烧累托石粘土20%、丙烯酰胺15%、引发剂0.25%、交联剂0.08%, 丙烯酸中和度为80%的吸水保水复合材料的吸去离子水倍率为870, 吸自来水倍率为250, 吸生理盐水倍率为68.累托石粘土添加量在0%~30%之间时, 吸水保水复合材料的吸液倍率比不含累托石的吸水树脂高.吸水保水复合材料吸液倍率从870g/g降到84g/g时, 凝胶强度从49g/cm2上升到235g/cm2.      

苯、甲苯对粒状铁去除四氯乙烯影响的柱实验研究

挥发性氯代烃和石油烃类污染是地下水中最常见的混合污染类型,而且这两类污染物毒性极强,对人类危害非常严重。文中选取具有代表性的四氯乙烯、苯和甲苯为研究对象,采用柱实验的方法研究苯和甲苯在粒状铁反应系统中吸附平衡后,对粒状铁去除四氯乙烯的机理及反应动力学的影响。在实验装置运行的过程中,苯、甲苯和四氯乙烯的浓度始终控制在2mg/L左右的水平。实验结果表明:苯或甲苯的存在对被还原的产物组成没有影响,主要氯代中间产物均为TCE、1,1-DCE、cis-1,2-DCE和VC,但组成比例略有不同。苯和甲苯的存在对去除速率有影响,即苯对四氯乙烯的去除有促进作用,去除速率平均提高13.5%;而甲苯则抑制四氯乙烯的去除,去除速率平均降低13.8%。对比控制柱,苯和甲苯存在时对出水水化学变化的影响没有明显差异。     

鄂西高磷鲕状赤铁矿磁化还原矿物组成及分布规律

鄂西高磷鲕状赤铁矿原矿全铁品位47.56%,含P 0.93%,主要脉石矿物为绿泥石、磷灰石、石英、方解石、铁白云石,属难选铁矿石。通过磁化焙烧-磨矿-磁选优化工艺,最佳磁化焙烧条件为:焙烧温度800℃、焙烧时间90min、还原剂用量12%,焙烧矿磨矿细度-0.074mm占85.15%,经弱磁选可得到全铁品位为58.13%、磷含量0.70%,铁回收率为90.41%的粗精矿。对磁化焙烧-磁选过程的各产物组成分析表明,焙烧矿和粗精矿中主要矿物为磁铁矿,占比分别为65%和85%;主要脉石矿物为绿泥石、磷灰石、石英、铁白云石等。粗精矿矿物的嵌布粒度较细,-0.074mm粒级占85.15%,但部分矿物仍以相互浸染、包裹、鲕状碎屑、连晶等形式存在,矿物仍未完全单体解离,从而导致粗精矿中杂质磷、铝等含量较高。粗精矿细磨后粒度-0.022mm含量为80%时,磁铁矿的解离度为84.63%,可实现磁铁矿充分单体解离,经过深选可提高铁精矿质量。     

某钒矿石提钒工艺试验的比较研究

对某地钒矿石进行了成份分析、赋存状态的分析,证实了该矿石含20%以上的钒云母。为了提高该矿钒的浸出率,研究了盐酸浸取、硫酸浸取、未经焙烧样品的浸取、焙烧后样品的浸取、添加剂的用量对浸出的影响、焙烧温度及浸取时间等对浸出率的影响。建立了无盐焙烧、稀硫酸浸取,使浸出率达90%以上,为后续工业设计和生产提供了可靠的数据和依据。     

安徽合肥地区浅层地下水质量评价

对合肥地区浅层地下水取样分析,采用单因子评价法、分类指标评价法和综合评价法对浅层地下水质量进行评价。结果显示:可以直接饮用的地下水资源(Ⅰ类水、Ⅱ类水和Ⅲ类水)占59.3%,经过适当处理可以饮用的地下水资源(Ⅳ类水)占30.5%,不能直接饮用的地下水资源(Ⅴ类水)占10.2%。在地下水评价指标中,挥发性有机指标较好,毒性重金属指标和半挥发性有机指标次之,无机毒理指标和一般化学指标较差。影响地下水质量的化学组分主要为铁、锰、总硬度、溶解性总固体、氟、硫酸盐和钠+钾等无机组分,与人类活动相关的化学组分主要为氨氮、硝酸盐、亚硝酸盐、六价铬、砷、铝、碘、氯化物等无机组分和苯并(a)芘等有机组分。影响地下水质量的原因主要为城市和乡镇工业污水、生活污水排放,农村农药、化肥使用及生活垃圾污染。     

利用坡缕石酸活化废液制备聚合氯化铝铁

坡缕石粘土生产活性白土的过程中产生的酸化废液会对环境造成严重污染,利用此废液,通过加入浓碱在一定条件下聚合制备了聚合氯化铝铁,最佳聚合pH值为4.0,所得产品基本符合GB15892-2003水处理剂国家标准.混凝实验结果显示,在480 mg/L的投药量下聚合氯化铝铁对自配水的浊度去除率最高可达98.3%,且适应的pH值范围较宽,处理效果优于其他常用絮凝剂.     

某石油化工污染场地地下水中挥发性有机物污染特征及成因分析

为了解典型污染场地浅层地下水微量有机污染特征,对西北某省会城市石油化工场地地下水中的挥发性有机污染物（VOCs）污染情况进行了调查。结果表明,污染场地地下水样品中挥发性有机污染物检出率为100%;检出率较高的是氯代烃和苯系物,检出率分别为60%和40%。超标组分为苯和1,2-二氯丙烷,苯超标率为30%,1,2-二氯丙烷超标率10%,苯最大检出浓度达1515μg/L。场地内的原油储存罐、污水隔油池的渗漏以及石油冶炼、机械加工过程工业废水不合理排放均为该场地地下水VOCs的重要来源;VOCs的理化性质以及污染场地地下水防污性能差是影响该场地地下水环境中VOCs归宿的主要因素。     

生物曝气技术对石油类污染地下水的修复效果及去除机制

针对东北某石油污染场地水文地质条件进行模拟,按照试验场地地层现状进行实验室缩放,研究微生物在含水层介质为砾砂、粗砂和中砂中的迁移速度以及含水层介质吸附的微生物量。选取苯和二甲苯作为目标石油污染物,研究生物曝气技术对被污染地下水的修复效果及其去除污染物的机制。实验结果表明:微生物在介质中的迁移速度从大到小为砾砂、粗砂、中砂;介质吸附微生物量的顺序从大到小为中砂、粗砂、砾砂;生物曝气4个月后,苯和二甲苯去除率分别为86.4%和81.7%,BS对中砂层中的苯和二甲苯去除效果好于砾砂层和粗砂层,苯的去除效果好于二甲苯。由挥发机制去除的污染物为46.24%,生物降解去除的污染物为36.98%,BS技术可以有效去除地下水中石油类污染物。     

添加剂对放射性废物处置场中U及~(90)Sr的分配系数研究

通过滞留实验评价放射性废物处置场盖层不同基础物料与添加剂对放射性U与^90Sr的屏障效果,以确定不同基础物料及添加荆配合条件下U与^90Sr的分配系数Ka。滞留实验成果表明天然深褐色含腐殖质含角砾砂质亚粘土对U与^90Sr的Kd分别为1838．13和36．16,为良好的基础物料,添加Na2S和Na2CO3后可增大对^90Sr的滞留,添加碳质砂岩粉可增加对U的滞留。在还原条件下,洪积物及泥石流堆积物以及残积成因含角砾粉砂土基础物料在添加Na2S后,^90Sr的Kd为3069．30～3494．28;添加Na2CO3后,^90Sr的Kd为81．22～22203．6。洪积物及泥石流堆积物的泥、砂和砾石混合物、变质碳质粉砂岩风化物、残积成因砂质亚粘土和坡积物砂质亚粘土等4类基础物料添加FeS2、腐殖土后对U和^90Sr的滞留效果总体较差;净水剂、磷灰岩和粉煤灰3类添加剂对U和Sr的屏障效果以负面影响为主,不宜用作屏障添加剂。实验结果表明U与Sr的迁移-固定性能相反,在放射性元素迁移途径上宜分别建造U,Sr屏障,且优先处置U放射性元素。     

电化学循环井驱动模拟含水层化学氧化降解三氯乙烯

传统原位化学氧化地下水修复技术存在氧化剂迁移距离短和利用率低等问题。本研究在双井循环模式促进传质的基础上,通过注水井中的地下水电解原位提供O₂和H₂,配合乙二胺四乙酸(ethylenediamine tetraacetic acid,EDTA)络合溶解出含水层Fe(Ⅱ),活化O₂产生羟基自由基(•OH),实现地下水三氯乙烯(TCE)的氧化降解。在填充了砂土和黏土互层的二维砂槽中,设置电流为0.2 A、流速为72 cm/d、初始TCE浓度为3 mg/L,经过9 d的连续通电处理后,TCE浓度降低到1 mg/L,降解率达到67%。通电前投加0.5 mmol/L EDTA,经过1 d水流循环后含水层中溶解态Fe(Ⅱ)浓度从02 mg/L增加到414 mg/L,黏土区域较高。通电过程中,循环井促进O₂、Fe(Ⅱ)-EDTA和TCE的有效接触与反应,使TCE氧化降解。通电初期,黏土区域Fe(Ⅱ)氧化速率、TCE降解速率较周围慢,后期差异逐渐减小。未通电时加入醋酸钠可促进Fe(Ⅲ)还原,使含水层中铁循环利用。该修复过程通过循环井提升了氧化剂迁移距离,使用源于含水层的Fe(Ⅱ)-EDTA和稳定性较好的O₂提高了氧化剂利用率,有望应用于有机污染地下水修复。     

Impact Factors on Removal of Perchloroethylene with Nano-Ni/Fe Methodology

Chlorinated hydrocarbons are widely detected in groundwater, but conventional removal methodologies are not time-and-cost effective. With the development of iron reducing technology in recent years, research on nano-iron and nano-bimetal has become a hot spot. The paper presents the results of impact factors on perchloroethylene （PCE） removal by nano-Ni/Fe method. The data show that the reaction rate of unexposed nano-Ni/Fe is 4 times higher than exposed one; and temperature is one of the important controlling factors. Reaction rate constant KSA increases by 2-3 times with every 10℃ increment of temperature. Within a specific range, higher Ni/Fe ratio favors dechlorination process. When the Ni/Fe is 8%, the dechlorination process reaches the highest rate. Dissoved oxygen in the solution does not favor the degradation of chlorinated hydrocarbons.     

Bioreduction of Fe-bearing clay minerals and their reactivity toward pertechnetate (Tc-99)

⁹⁹Technetium (⁹⁹Tc) is a fission product of uranium-235 and plutonium-239 and poses a high environmental hazard due to its long half-life (t_1/2 = 2.13 × 10⁵ y), abundance in nuclear wastes, and environmental mobility under oxidizing conditions [i.e., Tc(VII)]. Under reducing conditions, Tc(VII) can be reduced to insoluble Tc(IV). Ferrous iron, either in aqueous form (Fe²⁺) or in mineral form [Fe(II)], has been used to reduce Tc(VII) to Tc(IV). However, the reactivity of Fe(II) from clay minerals, other than nontronite, toward immobilization of Tc(VII) and its role in retention of reduced Tc(IV) has not been investigated. In this study the reactivity of a suite of clay minerals toward Tc(VII) reduction and immobilization was evaluated. The clay minerals chosen for this study included five members in the smectite-illite (S-I) series, (montmorillonite, nontronite, rectorite, mixed layered I-S, and illite), chlorite, and palygorskite. Surface Fe-oxides were removed from these minerals with a modified dithionite-citrate-bicarbonate (DCB) procedure. The total structural Fe content of these clay minerals, after surface Fe-oxide removal, ranged from 0.7% to 30.4% by weight, and the structural Fe(III)/Fe(total) ratio ranged from 45% to 98%. X-ray diffraction (XRD) and Mössbauer spectroscopy results showed that after Fe oxide removal the clay minerals were free of Fe-oxides. Scanning electron microscopy (SEM) revealed that little dissolution occurred during the DCB treatment. Bioreduction experiments were performed in bicarbonate buffer (pH-7) with structural Fe(III) in the clay minerals as the sole electron acceptor, lactate as the sole electron donor, and Shewanella putrefaciens CN32 cells as a mediator. In select tubes, anthraquinone-2,6-disulfate (AQDS) was added as electron shuttle to facilitate electron transfer. In the S-I series, smectite (montmorillonite) was the most reducible (18% and 41% without and with AQDS, respectively) and illite the least (1% for both without and with AQDS). The extent and initial rate of bioreduction were positively correlated with the percent smectite in the S-I series (i.e., layer expandability). Fe(II) in the bioreduced clay minerals subsequently was used to reduce Tc(VII) to Tc(IV) in PIPES buffer. Similar to the trend of bioreduction, in the S-I series, reduced NAu-2 showed the highest reactivity toward Tc(VII), and reduced illite exhibited the least. The initial rate of Tc(VII) reduction, after normalization to clay and Fe(II) concentrations, was positively correlated with the percent smectite in the S-I series. Fe(II) in chlorite and palygorskite was also reactive toward Tc(VII) reduction. These data demonstrate that crystal chemical parameters (layer expandability, Fe and Fe(II) contents, and surface area, etc.) play important roles in controlling the extent and rate of bioreduction and the reactivity toward Tc(VII) reduction. Reduced Tc(IV) resides within clay mineral matrix, and this association could minimize any potential of reoxidation over long term.     

Predicting arsenic concentrations in the porewaters of buried uranium mill tailings

The proposed JEB Tailings Management Facility (TMF) to be emplaced below the groundwater table in northern Saskatchewan, Canada, will contain uranium mill tailings from McClean Lake, Midwest and Cigar Lake ore bodies, which are high in arsenic (up to 10%) and nickel (up to 5%). A serious concern is the possibility that high arsenic and nickel concentrations may be released from the buried tailings, contaminating adjacent groundwaters and a nearby lake. Laboratory tests and geochemical modeling were performed to examine ways to reduce the arsenic and nickel concentrations in TMF porewaters so as to minimize such contamination from tailings buried for 50 years and longer. The tests were designed to mimic conditions in the mill neutralization circuit (3 hr tests at 25°C), and in the TMF after burial (5–49 day aging tests). The aging tests were run at, 50, 25 and 4°C (the temperature in the TMF). In order to optimize the removal of arsenic by adsorption and precipitation, ferric sulfate was added to tailings raffinates¹ having Fe/As ratios of less that 3–5. The acid raffinates were then neutralized by addition of slaked lime to nominal pH values of 7, 8, or 9.Analysis and modeling of the test results showed that with slaked lime addition to acid tailings raffinates, relatively amorphous scorodite (ferric arsenate) precipitates near pH 1, and is the dominant form of arsenate in slake limed tailings solids except those high in Ni and As and low in Fe, in which cabrerite-annabergite (Ni, Mg, Fe(II) arsenate) may also precipitate near pH 5–6. In addition to the arsenate precipitates, smaller amounts of arsenate are also adsorbed onto tailings solids.The aging tests showed that after burial of the tailings, arsenic concentrations may increase with time from the breakdown of the arsenate phases (chiefly scorodite). However, the tests indicate that the rate of change decreases and approaches zero after 72 hrs at 25°C, and may equal zero at all times in the TMF at 4°C. Consistent with a kinetic model that describes the rate of breakdown of scorodite to form hydrous ferric oxide, the rate of release of dissolved arsenate to tailings porewaters from slake limed tailings: (1) is proportional to pH above pH 6–7; (2) decreases exponentially as the total molar Fe/As ratio of tailings raffinates is increased from 1/1 to greater than 5/1; and (3) is proportional to temperature with an average Arrhenius activation energy of 13.4 ± 4.2 kcal/mol.Study results suggest that if ferric sulfate and slaked lime are added in the tailings neutralization circuit to give a raffinate Fe/As molar ratio of at least 3–5 and a nominal (initial) pH of 8 (final pH of 7–8), arsenic and nickel concentrations of 2 mg/L or less, are probable in porewaters of individual tailings in the TMF for 50 to 10,000 yrs after tailings disposal. However, the tailings will be mixed in the TMF, which will contain about 35% tailings with Fe/As = 3.0, and 65% tailings with Fe/As = 5.0–7.7. Thus, it seems likely that average arsenic pore water concentrations in the TMF may not exceed 1 mg/L.     

Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite: Characterization and behaviors

Although natural siderite has been investigated to remove both As(III) and As(V), it has relatively low adsorption rate and capacity. It is crucial to enhance its adsorption characteristics for As removal prior to being used in practical application. Modified granular natural siderite (MGNS) was fabricated through addition of organic binder, extrusion granulation and calcination, and evaluated for adsorption characteristics by means of batch and column tests. Results showed that MGNS had higher adsorption rate and capacity for As(III) in comparison with natural siderite. Arsenic(III) adsorption achieved equilibrium at 24 h, with adsorption capacity of 9.43 mg/g estimated from Langmuir isotherm at 25 °C. Column tests showed that there was less difference in total As loads in MGNS-packed filters for As(III)-spiked deionized water, As(III)-spiked tap water, and real-world high-As groundwater. The coexistence of anions had no significant effect on As adsorption in both batch and column experiments. Results of XRD, SEM and BET analysis indicated that MGNS, as an Fe(II)/(III) hybrid system, had a much larger specific surface area relative to the pristine natural siderite due to massive spherical aggregates attaching to the siderite matrix. XANES spectra showed that As(V) was the major species in the adsorbent after As(III) adsorption. Its proportion in total As slightly increased with the increase in contact time. Adsorption and heterogeneous oxidation of As(III) were believed to be the main mechanisms of As(III) removal by MGNS. This study suggested that MGNS is a potential adsorbent for effectively removing As from As-contaminated groundwater in filter application.     

石家庄地面水回渗地下过程的氮行为影响试验研究

石家庄是我国北方地下水位下降较大的城市之一,利用其毗邻滹沱河宽阔河滩,地面水可直接入渗补给地下水的有利水文地质条件,实施地面水回渗地下工程,将具有现实意义.为探索地面水回渗后的水质变化,该文针对地面水在回渗过程中对水质起限制性影响的氮行为作用进行了模拟试验研究.结果显示,利用2 m厚的滹沱河细砂土及与粘土按一定比例的混合砂土层,可对间歇式实施地面水回渗中的铵氮组分形成一定容量的截留去除,并且该截留量又在随回渗次数的增加而缓慢下降,当采用人工增加环境碱度及湿度的办法后可消除这种下降.同时,还显示对回渗水中硝酸氮的去除率不高,但若采用人工添加乙醇碳源和接种优势脱氮微生物菌种方法,硝酸氮的去除率将会得到较大提高.     

Pump-and-treat method to remove nitrate from groundwater with liquor as the carbon source

As a common pollutant in groundwater, nitrate poses a significant threat to drinking water safety, especially in rural areas. A feasible solution to this problem must be established. In this study, a simple sand bucket was designed to investigate the capability of denitrification with liquor as the carbon source to remove nitrate from pumped groundwater, and the feasibility of the pump-and-treat method. Results showed that addition of a proper amount of liquor enhanced the growth and metabolism of denitrifying bacteria, efficiently reduced the nitrate content in pumped groundwater, and restricted the accumulation of intermediate products. The removal rate of nitrate exceeded 99% and reached about 16.0 mg/L/day when the carbon-to-nitrogen (C/N) ratio was higher than 0.8. The accumulated concentration of nitrite as an intermediate was less than 1.0 mg/L when the C/N ratio was higher than 1.5. However, acetate accumulation was significant. Considering the accumulation of intermediates, the appropriate range of the C/N ratio should be 1.5–1.8. In addition, onset and maintenance of denitrification were not significantly influenced by dissolved oxygen and pH. The pump-and-treat method can provide a convenient and practical channel for household or collective removal of nitrate from pumped groundwater in rural areas because liquor as a household drink is frequently accessible and inexpensive in many areas.     

舒兰粘土矿中铁的赋存形式

舒兰粘土矿系高岭石型粘土矿,其中Fe_2O_3的含量达1.5～2.7％。经穆斯堡尔谱研究,有二对四极双峰,IS分别为0.450～0.462、0.425～0.439mm/s,QS分别为0.938～0.958、0.397～0.476mm/s。表明其中的铁基本都是高自旋的Fe~(3+),主要赋存于蒙脱石—囊脱石晶格的配位八面体中,M_1与M_2中均分布有铁,其原子比约为1:3。     

土壤含水层处理系统对再生水入渗过程中"三氮"去除的柱试验模拟

土壤含水层处理系统(soil aquifer treatment,SAT)是一种重要的人工回灌地下水方式。以再生水为回灌水源时,水中含有的“三氮”可能会对回灌区地下水造成污染风险。研究各种因素对在SAT中去除再生水中“三氮”的影响具有重要意义。本研究中,通过高200 cm、内径50 cm土柱试验,研究了SAT系统中粒径、干湿比(落干期与淹水期的比值)、在系统表层增加生物炭及渗透流速对实际再生水“三氮”去除效果的影响。结果表明,在干湿比1∶1条件下,实际河道细砂和中细砂柱底部出水中NH₄-N平均去除率分别为73%和66%,去除机理主要为吸附和硝化作用,NO₂-N基本被去除。系统中硝化作用导致NO₃-N浓度升高,出水中NO₃-N浓度平均增长了3.0%4.1%。在深度115 cm以上, 中细砂柱内比细砂柱内的硝化作用更强,这导致了更高的NH₄-N去除率和更低的NO₃-N去除率。延长落干期后(干湿比3∶1),系统具有了更强的复氧能力,促进了硝化作用,使得NH₄-N的平均去除率提高了20%,而NO₃-N的降低了3%4%,增加了NO₃-N污染风险。在中细砂层添加5%重量生物炭后,吸附性能增强,使其对NH₄-N平均去除率增加了20%32%,但对NO₃-N影响不明显。渗透流速与NH₄-N的去除和NO₃-N的增加均呈负相关。综合分析可得出,影响SAT系统去除“三氮”的最主要因素是干湿比和渗透流速,在回补水源中NH₄-N浓度较高时,可考虑在SAT系统表层添加生物炭以增强其去除效果。     

Characterization of accumulated precipitates during subsurface iron removal

The principle of subsurface iron removal for drinking water supply is that aerated water is periodically injected into the aquifer through a tube well. On its way into the aquifer, the injected O₂-rich water oxidizes adsorbed Fe²⁺, creating a subsurface oxidation zone. When groundwater abstraction is resumed, the soluble Fe²⁺ is adsorbed and water with reduced Fe concentrations is abstracted for multiple volumes of the injection water. In this article, Fe accumulation deposits in the aquifer near subsurface treatment wells were identified and characterized to assess the sustainability of subsurface iron removal regarding clogging of the aquifer and the potential co-accumulation of other groundwater constituents, such as As. Chemical extraction of soil samples, with Acid-Oxalate and HNO₃, showed that Fe had accumulated at specific depths near subsurface iron removal wells after 12 years of operation. Whether it was due to preferred flow paths or geochemical mineralogy conditions; subsurface iron removal clearly favoured certain soil layers. The total Fe content increased between 11.5 and 390.8 mmol/kg ds in the affected soil layers, and the accumulated Fe was found to be 56-100% crystalline. These results suggest that precipitated amorphous Fe hydroxides have transformed to Fe hydroxides of higher crystallinity. These crystalline, compact Fe hydroxides have not noticeably clogged the investigated well and/or aquifer between 1996 and 2008. The subsurface iron removal wells even need less frequent rehabilitation, as drawdown increases more slowly than in normal production wells. Other groundwater constituents, such as Mn, As and Sr were found to co-accumulate with Fe. Acid extraction and ESEM-EDX showed that Ca occurred together with Fe and by X-ray Powder Diffraction it was identified as calcite.