Microbial Fe(III) Reduction in Acidic Mining Lake Sediments after Addition of an Organic Substrate and Lime

To elucidate the role of Fe(III) reduction in mining lake sediments amended with organic substrates, we performed a large (10 m diameter) enclosure experiment in which sediments were amended with Carbokalk, a waste product from sugar industry containing organic carbon and lime. Fe(III) reduction rates were determined monthly by measuring the accumulation of Fe(II) in the sediments in the field. Fe(III) reduction rates were also determined by incubating sediment samples with synthetic Fe(III) oxyhydroxide under in situ temperature in the laboratory. Sulfate reduction was selectively inhibited in the Fe(III) reduction experiments by addition of sodium molybdate. Sulfate reduction was measured by accumulation of reduced inorganic sulfides in the field and by ³⁵S radiotracer using a core injection technique. Sediment incubation and determination of sulfate reduction rates with radiotracer showed that sulfate reduction and direct microbial Fe(III) reduction occured simultaneously in the upper centimeters of the sediments and that both processes contributed to alkalinity generation. However, Fe(III) reduction was the initial process and rates were at least 3.5 fold higher than sulfate reduction rates. The results indicate that the presence of suitable anions for Fe(II) precipitation as carbonate or sulfide is needed in order to prevent loss of potential alkalinity by Fe(II) diffusion and reoxidation in the water column.     

铁屑微电解法深度处理油田钻井污水

采用化学混凝-铁屑微电解法深度处理钻井污水。确定了最佳工艺条件：铁屑与活性炭的质量比为0．5，反应时间为2h，污水pH为1．0，温度为常温，反应后用石灰乳调节污水pH至12。处理后钻井污水COD可由原水的8065mg／L降至430mg／L，COD去除率大于94％，色度去除率达100％，达到国家综合污水三级排放标准。     

Bacterioplankton Community Structure and Dynamics in Enclosures During Bioremediation Experiments in an Acid Mining Lake

In an acid mining lake (pH 2.6) enclosure experiments wereperformed with the addition of different concentrations oforganic carbon, nitrogen and phosphorus. SSCP-communityfingerprints, based on 16S rRNA gene amplicons, were performed tomonitor changes in the structure of the total bacterialcommunity and the sulfate reducing bacteria (SRB) in themesocosms. Total bacterial cell counts, as assessed byepifluorescence microscopy, were increased in the mesocosmsamended with organic carbon. The addition of carbon alsoincreased the number of abundant bacterial taxa substantiallyalong depth. Sulfate reducing bacteria (SRB) could be detected inall enclosures and all parts of the water column. These SRBbelonged to genus Desulfobacter as indicated bycoroborating molecular data.     

Effects of Acidification and its Mitigation with Lime and Wood Ash on Forest Soil Processes in Southern Sweden. A Joint Multidisciplinary Study

A joint multidisciplinary investigation was undertaken to studythe effects of lime and wood ash applications on two Norway spruce forest Spodosolic soils. The two sites, typical for southern Sweden, were treated in 1994 with either 3.25 t ha^-1 dolomite or 4.28 t ha^-1 wood ash (Horröd site) or in 1984 with either 3.45 or 8.75 t ha^-1 dolomite (Hasslöv site). Both sites show signs of acidification by atmospheric anthropogenic deposition and possessed low soil pH(4.3) and high concentrations of inorganic Al (35 M) in theupper illuvial soil solution. The prevailing soil conditions indicated perturbed soil processes. Following treatment with lime or wood ash, the soil conditions were dramatically altered. Cation exchange capacity (CEC) and base saturation (BS) was considerable increased after addition. Four years after application most of the added Ca and Mg was still present in the mor layer. Fifteen years after application,Mg in particular, became integrated deeper in the soil profile with a greater proportion lost by leaching incomparison to Ca. The concentrations of these ions were greatestin the mor layer soil solutions and Mg had higher mobility givinghigher concentrations also deeper in the profile. Four years after treatment, the application of wood ash and limeresulted in lower pH values and higher inorganic Al in mineral subsoil solutions compared to the untreated soil. We hypothesize that this was probably due to an increased flow of hydrogen ionsfrom the upper soil as a result of displacement by Ca and Mg ionsin the enlarged exchangeable pool. In contrast, fifteen years after lime and wood ash application, the mineral subsoil horizonspossessed a higher pH and lower soil solution Al content than theuntreated plots.Liming promoted soil microbial activity increasing soil respiration 10 to 36%. This is in the same range as net carbon exchange for forests in northern Sweden and could potentially have a climatological impact. The turnover of low molecularweight organic acids (LMWOA) by the soil microbial biomass werecalculated to contribute 6 to 20% to this CO₂ evolution.At Horröd, citrate and fumarate were the predominant LMWOAs with lowest concentrations found in the treated areas. In contrast, at the Hasslöv site, propionate and malonate were the most abundant LMWOAs. Higher microbial activity in the upper soil horizons was also theprobable cause of the considerably higher DOC concentrations observed in the soil solution of ash and lime treated areas. Thelime-induced increase in DOC levels at Hasslöv could be attributed to increases in the 3–10 kDa hydrophobic size fraction. Liming also promoted nitrification with high liming doses leading to extreme concentrations of NO₃ ^- (1 mM) in soil solution.At Hasslöv the community of mycorrhizal fungi was dramatically changed by the addition of lime, with only four of 24 species recorded being common to both control and treated areas.Many of the observed effects of lime and ash treatment can be viewed as negative in terms of forest sustainability. After fouryears of treatment, there was a decrease in the pH of the soil solution and higher concentrations of inorganic Al and DOC. Increased organic matter turnover, nitrification and NO₃ ^-leakage were found at Hasslöv. Considering that the weathering rate and the mineral nutrient uptake by trees is mostprobably governed by mycorrhizal hyphae etchingmineral grains in the soil, it is important to maintain this ability of the mycorrhizal fungi. The lime and ash-induced changed mycorrhizal community structure may significantly affect this capability. In light of this investigation and others, as reviewed by Lundström et al. (2003), the implications ofliming on forest health are multifaceted with complex relationships occurring over both space and time.     

Changes in mineralogical and leaching properties of converter steel slag resulting from accelerated carbonation at low CO2 pressure

Steel slag can be applied as substitute for natural aggregates in construction applications. The material imposes a high pH (typically 12.5) and low redox potential (Eh), which may lead to environmental problems in specific application scenarios. The aim of this study is to investigate the potential of accelerated steel slag carbonation, at relatively low pCO₂ pressure (0.2 bar), to improve the environmental pH and the leaching properties of steel slag, with specific focus on the leaching of vanadium. Carbonation experiments are performed in laboratory columns with steel slag under water-saturated and -unsaturated conditions and temperatures between 5 and 90 °C. Two types of steel slag are tested; free lime containing (K3) slag and K1 slag with a very low free lime content. The fresh and carbonated slag samples are investigated using a combination of leaching experiments, geochemical modelling of leaching mechanisms and microscopic/mineralogical analysis, in order to identify the major processes that control the slag pH and resulting V leaching. The major changes in the amount of sequestered CO₂ and the resulting pH reduction occurred within 24 h, the free lime containing slag (K3-slag) being more prone to carbonation than the slag with lower free lime content (K1-slag). While carbonation at these conditions was found to occur predominantly at the surface of the slag grains, the formation of cracks was observed in carbonated K3 slag, suggesting that free lime in the interior of slag grains had also reacted. The pH of the K3 slag (originally pH ± 12.5) was reduced by about 1.5 units, while the K1 slag showed a smaller decrease in pH from about 11.7 to 11.1. However, the pH reduction after carbonation of the K3 slag was observed to lead to an increased V-leaching. Vanadium leaching from the K1 slag resulted in levels above the limit values of the Dutch Soil Quality Decree, for both the untreated and carbonated slag. V-leaching from the carbonated K3 slag remained below these limit values at the relatively high pH that remained after carbonation. The V-bearing di-Ca silicate (C2S) phase has been identified as the major source of the V-leaching. It is shown that the dissolution of this mineral is limited in fresh steel slag, but strongly enhanced by carbonation, which causes the observed enhanced release of V from the K3 slag. The obtained insights in the mineral transformation reactions and their effect on pH and V-leaching provide guidance for further improvement of an accelerated carbonation technology.     

综合印染废水混凝试验研究

考察了几种常用混凝剂对印染废水的处理效果。研究表明，在最佳pH值9～11时，硫酸亚铁具有较好的处理效果；复配试验表明，当硫酸亚铁投加量为400mg／l，熟石灰400mg／1，PAM为2mg／l时，COD去除率76．3％，色度去除率94．5％．处理成本为0．16元／t。     

Effects of Acidification and its Mitigation with Lime and Wood Ash on Forest Soil Processes: A Review

Anthropogenic acid deposition causes forest soil acidification and perturbation of the soil forming processes. The impact of soil acidification on tree growth is discussed in view of the role of mycorrhizal fungi in weathering and nutrient uptake. A review has been carried out of experiments involving treatments of forest soil by lime and wood ash, where soil properties and soil solution composition have been investigated. Results from these experiments in Europe and North America are summarized. In general, the content of C in the mor layer decreased as a result of treatment due to higher microbial activity and soil respiration as well as increased leakage of DOC. In addition, the content of N in the mor layer, in general, decreased after treatment and there are occasional peaks of high NO₃concentrations in soil solution. In nearly all reviewed investigations the pH of the deep mineral soil solution decreased and Al, SO₄and NO₃concentrations increased after treatment. These effects are probably due to the high ionic strength and increased microbial activity as a consequence of the treatments. In the soil, pH, CEC and base saturation increased in the upper horizons, but decreases in the upper mineral soil are also reported. In general, there was no increase in tree growth as a result of these treatments. The positive effects of the treatments on soil processes and tree growth are therefore questionable. In view of these conclusions, an investigation was carried out on the soil and soil solution chemistry and the role of mycorrhizal fungi in a spruce stand treated with two doses of lime and another treated with lime/ash in southern Sweden. The results of this investigation is reported in this volume.     

铁盐沉淀-絮凝法处理矿山低浓度含砷废水

采用铁盐沉淀-絮凝法处理某矿山低浓度含砷废水,研究了沉淀剂种类、铁与砷的摩尔比(铁砷比)、砷的价态、反应pH以及添加高分子絮凝剂对除砷效果的影响。与其他铁盐沉淀剂(聚合硫酸铁、氯化铁)相比,高铁酸钾具有优异的除砷性能。铁盐对砷(Ⅲ)的去除率明显低于砷(Ⅴ)。砷去除率随铁砷比的增大而提高。反应pH对除砷效果影响显著。以高铁酸钾为砷沉淀剂,在铁砷比为12∶1、反应pH为5~7、聚丙烯酰胺投加量为0.5~1.0 mg/L的最适条件下,废水的砷去除率达98%以上。处理后出水中砷质量浓度低于0.05 mg/L,达到GB3838—2002《地表水环境质量标准》中Ⅲ类水质标准。     

Long-term Performance of a Permeable Reactive Barrier in Acid Sulphate Soil Terrain

Deep drainage technique utilised for flood mitigation in low-land coastal areas of Australia during the late 1960s has resulted in the generation of sulphuric acid in soil by the oxidation of pyritic materials. Further degradation of the subsurface environment with widespread contamination of the underlying soil and groundwater presents a major and challenging environmental issue in acid sulphate soil (ASS) terrains. Although several ASS remediation techniques recently implemented in the floodplain of Southeast Australia including operation of gates, tidal buffering and lime injections could significantly control the pyrite oxidation, they could not improve the long-term water quality. More recently, permeable reactive barriers (PRBs) filled with waste concrete aggregates have received considerable attention as an innovative, cost-effective technology for passive in situ clean up of groundwater contamination. However, long-term efficiency of these PRBs for treating acidic groundwater has not been established. This study analyses and evaluates the performance of a field PRB for treating the acidic water over 2.5 years. The pilot-scale alkaline PRB consisting of recycled concrete was installed in October 2006 at a farm of southeast New South Wales for treating ASS-impacted groundwater. Monitoring data of groundwater quality over a 30 month period were assessed to evaluate the long-term performance of the PRB. Higher pH value (~pH 7) of the groundwater immediately downstream of the PRB and higher rates of iron (Fe) and aluminium (Al) removal efficiency (>95%) over this study period indicates that recycled concrete could successfully treat acidic groundwater. However, the overall pH neutralising capacity of the materials within the barrier declined with time from an initial pH 10.2 to pH 7.3. The decline in the performance with time was possibly due to the armouring of the reactive material surface by the mineral precipitates in the form of iron and aluminium hydroxides and oxyhydroxides as indicated by geochemical modelling.     

回收萘法苯酐生产废水中的富马酸

采用催化异构化、碱溶、脱色、酸析、过滤等工艺处理萘法苯酐生产废水,回收其中的富马酸。考察了碱的品种、碱溶pH、活性炭加入量、酸析pH等对富马酸产品外观质量和收率的影响。实验得到最佳工艺条件:采用氢氧化钠作为碱溶用碱,碱溶pH为6,活性炭加入量为0.5%(w),酸析pH为2。在此最佳工艺条件下制备的富马酸产品外观为白色,纯度达到99.1%,产品收率为72.8%。按30 kt/a苯酐生产装置计,每年可回收富马酸660 t,年利润429万元。     

Terrestrial physical and chemical processes for liquid waste treatment

Experiences gained from full-scale evaluation of advanced treatment processes used for reclaiming wastewaters should help in the evaluation of potential treatment systems for treatment and reuse of water in space. Water Factory 21 is a 0.66 m³s⁻¹ (15 million gallons per day) water reclamation plant in California that has been in operation since 1976. The plant receives biologically treated wastewater. Lime treatment is effective for removal of heavy metals. Volatile organic constitutes are efficiently removed by air stripping. Non-volatile organic constituents are removed by activated carbon adsorption and reverse osmosis (RO). RO is a highly effective polishing step, and removes most of the remaining materials including inorganic salts, heavy metals, and organics. RO removed 85% of the total organic carbon, down to about 1 mg 1⁻¹, which is lower than in many treated drinking waters. The series of treatment processes used insured virus and pathogen removal, with lime treatment and chlorination together proving highly effective. Sufficient data has been collected to provide statistically reliable confidence limits to be set on the performance of each unit process.     

Chemistry,Mineralogy and Morphology of Spodosols at Two Swedish Sites Used to Assess Methods of Counteracting Acidification

The chemistry, mineralogy and morphology of two soil profiles developed on till material of granitic and gneissic composition in south-western Sweden were studied in relation to podzolization processes. These soils were used for treatments with lime and wood ash. The profiles do not show characteristic Podzol morphology but qualify as Spodosols under Soil Taxonomy criteria and are probably typical for the coniferous forest soils of south-western Sweden. Podzolization features are clear but less well expressed than in classic Podzols. The distribution of major elements shows podzolization features with accumulation of sesquioxides in the B horizons and depletion in the eluvial horizons. Quartz and feldspars dominate the bulk soils reflecting the clear relationship between the composition of the soil and the underlying bedrock. Low amounts of clay contain an interlayered vermiculitic phase as the main phyllosilicate in which the degree of interlayering, known to be pH dependent, varies with depth and is at a maximum in the Bhs horizon. In the B horizons there are small but significant amounts of imogolite-type material which affect the adsorption of sulphate.     

铁碳微电解法处理高盐度有机废水

用铁碳微电解法处理高盐度有机废水,考察了反应初始pH、铁碳质量比、反应时间、曝气及过氧化氢加入量等对该废水处理效果的影响。实验结果表明：在反应初始pH为4.0、铁碳质量比为1、反应时间为60m in、过氧化氢加入量为0.10%（体积分数）、曝气条件下,COD去除率为57.6%,盐去除率为47.0%;处理后废水的可生化性有明显的改善,BOD5/COD可达0.65;对COD的去除基本符合一级动力学规律。     

Stimulating the Biodegradation of Crude Oil with Biodiesel Preliminary Results

Experiments using biodiesel derived from vegetable oils have demonstrated the considerable potential for removing crude oil from contaminated beaches. During laboratory studies in small boxes, contaminated sand treated with biodiesel also demonstrated the rapid biodegradation of the crude oil. Water soluble components were washed through the sand columns and these components subsequently precipitated with cold storage. This solid fraction was not soluble in organic solvents but could be re-dissolved in dilute acid. The sediments after four weeks were black in colour due to the precipitation of metal sulphides although no H₂S was generated because the pH of the seawater kept the sulphides in solution. Further work is investigating which components of the oil were degraded and what products were formed.     

Monitoring operational and leachate characteristics of an aerobic simulated landfill bioreactor

Long-term biodegradation of MSW in an aerobic landfill bioreactor was monitored as a function of time during 510 days of operation. Operational characteristics such as air importation, temperature and leachate recirculation were monitored. The oxygen utilization rates and biodegradation of organic matter rates showed that aerobic biodegradation was feasible and appropriate to proceed in aerobic landfill bioreactor. Leachate analyses showed that the aerobic bioreactor could remove above 90% of chemical oxygen demand (COD) and close to 100% of biochemical oxygen demand (BOD5) from leachate. Ammonium (NH4+), nitrate (NO3-) and sulphate (SO4(2-)) concentrations of leachate samples were regularly measured. Results suggest that nitrification and denitrification occurred simultaneously, and the increase in nitrate did not reach the levels predicted stoichiometrically, suggesting that other processes were occurring. Leachate recirculation reduced the concentrations of heavy metals because of the effect of the high pH of the leachate, causing heavy metals to be retained by processes such as sorption on MSW, carbonate precipitation, and hydroxide precipitation. Furthermore, the compost derived from the aerobic biodegradation of the organic matter of MSW may be considered as soil improvement in the agricultural plant production. Bio-essays indicated that the ecotoxicity of leachate from the aerobic bioreactor was not toxic at the end of the experiment. Finally, after 510 days of degradation, waste settlement reached 26% mainly due to the compost of the organic matter.     

Chemical immobilisation of arsenic in contaminated soils using iron(II)sulphate—advantages and pitfalls

Chemical immobilisation of inorganic contaminants by increasing the sorption capacity of soils and/or promoting the formation of sparingly soluble precipitates may be a cost-effective approach to counteract groundwater pollution. This study focuses on the enhanced retention of arsenic in two contaminated soils by addition of solid iron(II)sulphate. Four lab-scale column experiments were performed under unsaturated conditions with subsoil material sampled at a former timber preservation site and a pigment production plant. Arsenic effluent concentrations indicated 89.9 to 99.8% immobilisation in the treated columns. Sequential extractions showed a shift in contaminant binding forms towards the iron(hydr)oxide and residual fractions. Possible immobilisation mechanisms are the precipitation of FeAs phases, the formation of inner sphere complexes, and/or the occlusion of arsenic in newly formed amorphous/crystalline iron oxides. Bromide breakthrough curves point to the fact that the addition of iron(II)sulphate only moderately affects soil hydraulic properties. In contrast to reduced emissions of arsenic, increased seepage water concentrations were observed for other trace elements (e.g., cobalt, nickel, zinc). Mass balances indicate that this effect is primarily related to the temporary pH-drop caused by the oxidation of ferrous iron. The results show that chemical immobilisation using iron(II)sulphate is a promising way to protect groundwater quality at sites contaminated with timber preservation and pigment production remnants. As a prerequisite, optimum amendment levels need to be established and practical/field tests should be accompanied by a monitoring for a broad range of relevant trace elements.     

内电解法处理偶氮染料废水

采用内电解法处理偶氮染料废水。正交实验结果表明，铸铁铁屑加入量对废水脱色率的影响最大，其次是酸性反应pH，再次是碱性反应pH，最后是碱性反应时间。最佳处理工艺条件为：铸铁铁屑加入量10g，酸性反应pH2．0，碱性反应pH7．0，碱性反应时间10min。此条件下脱色率达98．89％。铸铁铁屑使用6次后对废水的脱色率明显下降，将使用6次后的铸铁铁屑活化，活化后废水脱色率由86．80％提高至93．83％。     

利用农药含钾废渣制备氯化钾

利用热解及钙盐沉淀法对农药含钾废渣进行处理,制得高纯度的KCl.通过管式炉反应器对农药含钾废渣中有机物的去除进行了研究,探讨了升温速率、热解终温、终温保持时间及空气流量对热解过程的影响,并对钙盐沉淀法除氟过程的溶液pH及m(Ca2+)∶m(F-)进行了确定.实验结果表明:当升温速率为20℃/min、热解终温为600℃、终温保持时间为90 min、空气流量为3.0m3/min时,废渣中的有机物完全分解;钙盐沉淀法除氟的最佳条件为溶液pH 8,m(Ca2+)∶m(F-)=3.0,氟离子的去除率达到98％;最终得到KCl的产率为70.6％,产品纯度为98.2％,符合国家Ⅰ级优等品标准.     

PHYSICO-CHEMICAL CHARACTERIZATION AND LEACHING OF DESULPHURIZATION COAL FLY ASH

Fly ash produced by coal combustion using two types of desulphurization process were studied: a conventional pulverized coal boiler equipped with lime injection (PCL ash), and a circulating fluidized bed combustion boiler with limestone injection (CFBC ash). The ashes were characterized completely: granulometry, morphology, mineralogy, chemical composition and behaviour to water contact. Both PCL ash and CFBC ash present similar features: fine granulometry, presence of anhydrite phase and sulphate content. However, PCL ash also shows lots of spherical particles, unlike CFBC ash, and a much higher lime content, due to the lower desulphurization rate in PC boilers. Unlike CFBC ash, most of the trace elements in PCL ash show an inverse concentration–particle size dependence. Leachates obtained from both samples are rich in soluble salts [CaSO₄and Ca(OH)₂] and arsenic and selenium are prevented from solubilizing by high lime content. In wetted PCL ash, the formation of ettringite crystals stabilizes calcium and sulphate ions. Simultaneously, arsenate, selenate and chromate anions are trapped in the crystal. CFBC ash does not really harden because the lime content is too low. However, the leached selenium concentration is cut down in wetted CFBC ash samples.     

Phosphate fertilizer from sewage sludge ash (SSA)

Ashes from sewage sludge incineration are rich in phosphorus content, ranging between 4% and 9%. Due to the current methods of disposal used for these ashes, phosphorus, which is a valuable plant nutrient, is removed from biological cycling. This article proposes the possible three-stage processing of SSA, whereby more than 90% of phosphorus can be extracted to make an adequate phosphate fertilizer. SSA from two Swiss sewage sludge incinerators was used for laboratory investigations. In an initial step, SSA was leached with sulfuric acid using a liquid-to-solid ratio of 2. The leaching time and pH required for high phosphorus dissolution were determined. Inevitably, dissolution of heavy metals takes place that would contaminate the fertilizer. Thus in a second step, leach solution has to be purified by having the heavy metals removed. Both ion exchange using chelating resins and sulfide precipitation turned out to be suitable for removing critical Cu, Ni and Cd. Thirdly, phosphates were precipitated as calcium phosphates with lime water. The resulting phosphate sludge was dewatered, dried and ground to get a powdery fertilizer whose efficacy was demonstrated by plant tests in a greenhouse. By measuring the weight of plants after 6 weeks of growth, fertilized in part with conventional phosphate fertilizer, fertilizer made from SSA was proven to be equal in its plant uptake efficiency.