Calcite Precipitation in Hard Water Lakes in Calculation and Experiment

Calcite precipitation in model solutions and natural waters depends on the magnitude of saturation (saturation index ≫ 1). Continuous lye addition should simulate the CO₂ decrease through assimilation by algae and the experiments can be applied to the autochthonic calcite precipitation in lakes. It seems possible to restore lakes with artificial calcite precipitation. Basic data for this experiment are given in this paper.     

Microbially Induced Calcite Precipitation for Seepage Control in Sandy Soil

Microbially induced calcite precipitation (MICP) can reduce the permeability of soil by reducing the pore volumes. A MICP-based soil improvement method to control water leakage in irrigation channels and reservoirs built on sandy soil grounds is presented in this article. Using this method, a low-permeable hard crust can be formed at the soil surfaces. An experimental study was carried out to evaluate the effect of this method. Sandy soil samples were treated using four different schemes, namely, (1) surface spray, (2) surface spray with the addition of fibers, (3) surface spray and bulk stabilization, and (4) immersion stabilization. By applying around 2.6?L treatment liquid (consisting of ureolytic bacteria, 0.5?mol/L calcium chloride and 0.5?mol/L urea) to the top 2-cm thick soil, the seepage rates of the samples treated by the four different schemes could be reduced by up to 379 times. The conversion rates of calcium source in the tests were up to 89.7%. The results showed that a method of treating the soil in bulk before the formation of a crust on top of the soil layer was effective in reducing the seepage rates. After the bio-treatment, the formed low-permeable hard crust layer was 10 to 20?mm thick with a calcite content higher than 5%. Below the hard crusts, the calcite content was less than 5% and the soil was not properly cemented. Using the mercury intrusion test, it was found that both pore volumes and pore sizes of the bio-treated soil reduced significantly as compared with the untreated soil. Penetration tests using a flat-bottom penetrometer were used to assess the mechanical behavior of the bio-treated soil. The results indicated that the penetration resistance of the bio-treated soil layer was much higher than that of the untreated soil.     

The Role of a Green Alga in the Precipitation of Calcite and the Coprecipitation of Phosphate in Freshwater

The precipitation of calcite from a calcium bicarbonate solution, similar in ionic strength to natural hardwaters, was observed in a series of experiments utilizing an automated culture apparatus. Seeded growth experiments, using calcite seed crystals, were performed at a range of phosphate concentrations to observe inhibitory effects. These experiments demonstrated a linear relationship of increasing inhibition with increasing initial phosphate concentration. A further series of experiments was performed in which an actively photosynthesizing culture of a unicellular green alga (Chlorococcum sp.) was added to the culture vessel in order to initiate precipitation. Experiments to observe spontaneous precipitation, occurring in the absence of both seed and alga additions, were carried out to compare with precipitation rates in the algal experiments. A control experiment was also performed to investigate whether precipitation occurrred in algal cultures maintained in darkness. The carbonate site mechanistic model, developed for calcite precipitation in abiotic conditions, was used to analyse the results of the algal experiments and found to be applicable.     

The role of cyanobacteria in crystallization of magnesium calcites

Laboratory experiments showed the effect of the cyanobacterium Microcoleus chthonoplastes on the formation of magnesium calcites, using model solutions (2.14M MgCl₂-0.05M CaCl₂-0.6M NaCl-0.18M NaHCO₃). The conditions of existence of cyanobacteria in such solutions in light or darkness significantly alter the structure of the sediment and the shape and size of the carbonate crystals. Cyanobacteria slow down crystallization due to the formation of exometabolites with a chelating effect, which leads to the precipitation of high-magnesium calcites. In the photosynthetic environment the presence of huntite (CaMg₃(CO₃)₄), possible forerunner of dolomite, is prominent.     

Comparison of microbially induced calcium carbonate precipitation eligibility using sporosarcina pasteurii and bacillus licheniformis on two different sands

The use of biological means for ground improvement have become popular, which generally works through the process called microbially-induced calcium carbonate precipitation (MICP). Many studies indicate successful application of MICP based improvement with multiple bacteria and on several soils. Given the proven performance of MICP, this study aims to examine the MICP process by comparing the calcium carbonate precipitation ability of widely studied bacteria, i.e., Sporosarcina pasteurii and relatively under-recognized bacteria, i.e., Bacillus licheniformis to outline the formation success. For this purpose, two different sands were tested for observing precipitation behavior using a series of syringe tests. Furthermore, the effect of concentration and inclusion of calcium chloride for nutrition of bacteria, saturation with water, and hybrid use of two bacteria were investigated in some tests for diversification. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDS) were used for the interpretation of results. Results indicated that Sporosarcina pasteurii had performed superior over Bacillus licheniformis when achieving calcium carbonate precipitation in tests for both sands. In addition, many intriguing SEM images contributed to the literature of MICP monitoring, highlighting the effects of the variables investigated.     

Interactions between calcite precipitation (natural and artificial) and phosphorus cycle in the hardwater lake

The influence of calcite precipitation on the phosphorus cycle in stratified hardwater lake was studied before and during experiments with a new restoration technique. Surveys of the chemical composition of water column and monitoring of settling particles of Lake Luzin (North–East) showed that calcite precipitation occurs each year over 2–3 periods during spring and summer. The change of the phosphorus content influenced the calcite precipitation intensity. The sedimentation fluxes of phorphorus and the calcite precipitation were closely associated. Based on the hypothesis that calcite precipitation acts as an improvement to the trophic state by enhancing the internal phosphorus sink, this new technology for lake restoration was developed. The hypolimnetic Ca(OH)₂ addition during summer stratification in 1996–1997 induced the calcite precipitation in the deep water layer of Basin Carwitz of Lake Schmaler Luzin. The treatment also supported the natural calcite precipitation in the epilimnion. The annual total phosphorus content decreased from 0.46 tons in 1995 to 0.35 tons in 1997. The annual SRP content decreased from 0.02 tons in 1996 to 0.01 tons in 1997 after beginning the artificial calcite precipitation in 1996. The decrease of the annual Chl-a concentration in 1998 on 38% compared with that in 1996 pointed out the lake recovering. According to the one box model, the artificial calcite precipitation affected the P cycle in the lake by suppressing the P release from the sediments.     

球形赖氨酸芽孢杆菌(Lysinibacillus sphaericus)和嗜冷芽孢八叠球菌(Sporosarcina psychrophila)介导形成白云石晶体

【目的】白云石(Dolomite)是一种含有钙镁的碳酸盐矿物[CaMg(CO3)2],广泛存在于陆地和海洋等环境并常与油气埋藏共存。尽管白云石(或岩)的发现已经有三百多年的历史,但是对白云石的成因仍然没有定论,地质学上称之为\"白云石之谜\"。20世纪90年代Vasconcelos C.提出了\"微生物白云石模型\",为白云石成因的研究带来了新的思路。但是这一模型并不完善,白云石的形成与所介导的微生物生理状态以及环境参数之间的关系不明确。另外,所有报道的实验都是在地表压强条件下进行,无法表征自然界中白云石所处的高压环境。本研究中引入压力这一环境参数,结合菌株本身生理特性参数,综合考察多重因子对微生物介导形成白云岩的影响。【方法】利用球形赖氨酸芽孢杆菌(Lysinibacillus sphaericus)和嗜冷芽孢八叠球菌(Sporosarcina psychrophila)两株具有尿素水解活性的细菌作为生物材料,在不同的温度(15°C和30°C)压强(常压和20 MPa)氧气浓度(常压好氧条件和常压微氧条件)不同的尿素水解活性下进行生物矿化实验。通过SEM(扫描电子显微镜)和EDS(X射线能谱分析)相结合的方法观察沉淀物形貌和矿物成分构成。通过XRD(X射线衍射分析)定性测定碳酸盐矿物沉淀物的种类。【结果】球形赖氨酸芽孢杆菌和嗜冷芽孢八叠球菌在实验中所设计的所有矿化条件下都能够介导形成碳酸盐矿物沉淀。XRD和SEM检测均证实球形赖氨酸芽孢杆菌在30°C的20 MPa微氧条件下能够介导形成不规则菱面型和椭球型白云石。高压条件更有助于白云石的形成。除了白云石晶体,实验中还观察到有其他矿物(如方解石,碳氢镁石,钙镁碳酸石等)。【结论】实验证实球形赖氨酸芽孢杆菌和嗜冷芽孢八叠球菌具有矿化能力,特别是球形赖氨酸芽孢杆菌具有介导形成白云石的能力。微生物介导形成的碳酸盐矿物组分受到微生物的代谢活性以及温度、压力等生物矿化实验条件控制。这一研究结果帮助完善\"微生物白云石模型\",为解释白云石的深部成因提供数据支持。     

Phosphorfällung über Calciumcarbonat im eutrophen Wallersee (Salzburger Alpenvorland, Österreich). Coprecipitation of Phosphorus with Calcite in the Eutrophic Wallersee (Alpine Foreland of Salzburg,Austria)

By chemical analyses at the eutrophic Wallersee (Austria) a considerable precipitation of calcite during autumn overturn was found. It is a pure anorganic calcite precipitation, caused by the loss of free carbonic acid to the atmosphere during the mixing of epilimnic and hypolimnic water. An essential coprecipitation of phosphorus with the anorganic calcite precipitation could be shown by calcium and phosphorus balances and by SEM investigations. During the epilimnic biogenic calcite precipitation (in summer) phosphorus coprecipitation makes 0.19% of the calcium fallout. Phosphorus coprecipitation increases up to 0.42 % during the anorganic calcite precipitation when autumn overturn takes place. With respect to the total phosphorus sedimentation in the lake 25 % are coprecipitated with calcite.     

Increasing of Soil Urease Activity by Stimulation of Indigenous Bacteria and Investigation of Their Role on Shear Strength

Abstract

Recent studies have shown that the use of biostimulation is an effective technique to eliminate the environmental side effects of traditional soil improvement methods. The use of indigenous bacteria of soil is a new method through which indigenous bacteria produce carbonate calcium by their urease activity. Stimulation of soil indigenous bacteria with the aim of calcite precipitation can considerably increase the soil shear strength. In this study, indigenous ureolytic bacteria are stimulated by adding nutrients to the soil. Subsequently urease activity of these bacteria in the presence of calcium chloride and nickel chloride causes calcium carbonate to precipitate between the sand particles. The analysis showed that the stimulated soil compared to the control soil was significantly different in terms of the soil engineering properties and the amount of precipitated calcite. Further, the treated and untreated samples were examined using direct shear test, scanning electron microscope (SEM), and energy dispersive X-ray (EDX) analysis. The results showed an increase of 30–67% in ultimate shear strength, 4–18.8% in residual shear strength, 190% in the cohesion intercept, and 16.8% in the angle of internal friction. In addition, imaging and analysis of SEM-EDX indicated the production of large amounts of calcite precipitates on surfaces of soil particles and between them.     

The effects of biofilms on chemical processes in surficial sediments

1. The objectives of the present work were: (a) to evaluate the effects of the development and the presence of a photosynthetically active algal biofilm on chemical fluxes and processes at the sediment–water interface; (b) to measure the effects of the biofilm on chemical concentration gradients in the bulk sediment; and (c) to monitor pH and dissolved oxygen concentration in the biofilm, and through the sediment–water interface using microelectrodes. 2. Two experiments were performed over a period of 8 weeks using a recirculating fluvarium channel containing river sediments with an exposed surface of 0.2 m² and 20 dm³ of overlying solution. The first experiment was in darkness with minimal effects of a photosynthetically active biofilm. The second experiment in natural light produced a complex photosynthetic biofilm involving a succession of diatoms, green algae and cyanobacteria. 3. The solution overlying the biofilm was monitored continuously for dissolved calcium, silicon, phosphorus, alkalinity and oxygen, as well as conductivity, temperature and pH. The surface of the sediment was also monitored for biological and physical changes as the biofilm developed. The overlying solution was analysed over a period of 48 h at 2-h intervals to examine the effects of a well-developed algal biofilm. At the end of the 48 h, pH and oxygen microelectrodes were used to measure gradients above and through the biofilm, and porewaters were analysed from sediments which had been longitudinally sectioned at a maximum depth resolution of 0.5 mm. 4. Biofilm development had a large influence on the composition of the overlying solution and the development of vertical concentration gradients of solutes in the porewater. Once a diatom community was established, the concentration of dissolved silicon was low (< 40 μm ), with all the silicon diffusing from the underlying sediment being consumed in the biofilm (≈ 0.026 μmol m^?2 s^?1 at the end of the experiment). 5. The concentrations of calcium, alkalinity and phosphorus in digested sediment increased near the sediment–water interface. X-ray diffraction analysis showed that calcite was formed at the surface. Estimation of the fluxes of alkalinity and calcium in the overlying solution were consistent with calcite formation during daylight and possible dissolution in darkness. The maximum precipitation flux of calcium was 0.87 μmol m^?2 s^?1 and the maximum net release flux was 0.89 μmol m^?2 s^?1. 6. The net loss of soluble reactive phosphorus from the overlying solution measured over the intensive sampling period of 48 h is consistent with a coprecipitation mechanism and a surface density of phosphorus included in the lattice of calcite of 0.097 μmol m^?2. Processes in the biofilm rather than diffusion from the sediment porewater control chemical fluxes of calcium, alkalinity and phosphorus from the sediment to the overlying water.     

Effects of environmental factors on microbial induced calcium carbonate precipitation

Aims: To gain an understanding of the environmental factors that affect the growth of the bacterium Sporosarcina pasteurii, the metabolism of the bacterium and the calcium carbonate precipitation induced by this bacterium to optimally implement the biological treatment process, microbial induced calcium carbonate precipitation (MICP), in situ. Methods and Results: Soil column and batch tests were used to assess the effect of likely subsurface environmental factors on the MICP treatment process. Microbial growth and mineral precipitation were evaluated in freshwater and seawater. Environmental conditions that may influence the ureolytic activity of the bacteria, such as ammonium concentration and oxygen availability, as well as the ureolytic activities of viable and lysed cells were assessed. Treatment formulation and injection rate, as well as soil particle characteristics are other factors that were evaluated for impact on uniform induction of cementation within the soils. Conclusions: The results of the study presented herein indicate that the biological treatment process is equally robust over a wide range of soil types, concentrations of ammonium chloride and salinities ranging from distilled water to full seawater; on the time scale of an hour, it is not diminished by the absence of oxygen or lysis of cells containing the urease enzyme. Significance and Impact of Study: This study advances the biological treatment process MICP towards field implementation by addressing key environmental hurdles faced with during the upscaling process.     

巴氏芽孢八叠球菌及相关微生物的生物矿化的分子机理与应用

巴氏芽孢八叠球菌是迄今为止所知的利用尿素降解进行生物矿化的最为高效的微生物系统之一,基于其碳酸钙生物矿化形成的\"超强能力\",巴氏芽孢八叠球菌已经被成功地应用于沙石、土壤等生物固化中,成为一种全新的、具有极大潜力的生物建筑辅助技术,被称为\"生物水泥\"。由于巴氏芽孢八叠球菌分离自土壤,没有病原性并具有极好的环境友好性。近年来,其应用领域被拓展到环境治理乃至健康医疗领域,成为全新的研究热点。然而,与应用研究相比,人们对巴氏芽孢八叠球菌生物矿化背后的分子机理还知之甚少。因此,这里针对迄今为止国内外对于巴氏芽孢八叠球菌生物矿化相关的分子机理的研究进行分析介绍,在此基础上综述了包括建工、环境、及医疗健康领域在内的巴氏芽孢八叠球菌的应用,希望能够促进对于该球菌矿化的研究。