Sorption and transport of acetaminophen, 17alpha-ethynyl estradiol, nalidixic acid with low organic content aquifer sand

The sorption and transport of three pharmaceutical compounds (acetaminophen, an analgesic; nalidixic acid, an antibiotic; and 17α-ethynyl estradiol, a synthetic hormone) were examined by batch sorption experiments and solute displacement in columns of silica, alumina, and low organic carbon aquifer sand at neutral pH. Silica and alumina were used to represent negatively-charged and positively-charged fractions of subsurface media. Column transport experiments were also conducted at pH values of 4.3, 6.2, and 8.2 for the ionizable nalidixic acid. The computer program UFBTC was used to fit the breakthrough data under equilibrium and nonequilibrium conditions with linear/nonlinear sorption. Good agreement was observed between the retardation factors derived from column model studies and estimated from equilibrium batch sorption studies. The sorption and transport of nalidixic acid was observed to be highly pH dependent, especially when the pH was near the pK_a of nalidixic acid (5.95). Thus, near a compound's pK_a it is especially important that the batch studies be performed at the same pH as the column experiment. While for ionic pharmaceuticals, ion exchange to oppositely-charged surfaces, appears to be the dominant adsorption mechanism, for neutral pharmaceuticals (i.e., acetaminophen, 17α-ethynyl estradiol) the sorption correlated well with the K_ow of the pharmaceuticals, suggesting hydrophobically motivated sorption as the dominant mechanism.     

Simultaneous removal of As, Cd, Cr, Cu, Ni and Zn from stormwater: experimental comparison of 11 different sorbents

The potential of using alumina, activated bauxsol-coated sand (ABCS), bark, bauxsol-coated sand (BCS), fly ash (FA), granulated activated carbon (GAC), granulated ferric hydroxide (GFH), iron oxide-coated sand (IOCS), natural zeolite (NZ), sand, and spinel (MgAl(2)O(4)) as sorbents for removing heavy metals from stormwater are investigated in the present study. The ability of the sorbents to remove a mixture of As, Cd, Cr, Cu, Ni and Zn from synthetic stormwater samples were evaluated in batch tests at a starting pH of 6.5. The metal speciation and saturation data is obtained using the PHREEQ-C geochemical model and used to elucidate the sorption data. It is found that BCS, FA, and spinel have significantly higher affinity towards heavy metals mainly present as cationic or non-charged species (i.e. Cd, Cu, Ni and Zn) compared to those present as anionic species (i.e. As and Cr). However, IOCS, NZ and sand have higher affinity towards As and Cr, while alumina has equally high affinity to all tested heavy metals. The Freundlich isotherm model is found to fit the data in many cases, but ill fitted results are also observed, especially for FA, BCS and GAC, possibly due to leaching of some metals from the sorbents (i.e. for FA) and oversaturated conditions making precipitation the dominant removal mechanism over sorption in batches with high heavy metal concentrations and pH. Calculated sorption constants (i.e. K(d)) are used to compare the overall heavy metal removal efficiency of the sorbents, which in a decreasing order are found to be: alumina, BCS, GFH, FA, GAC, spinel, ABCS, IOCS, NZ, bark, and sand. These findings are significant for future development of secondary filters for removal of dissolved heavy metals from stormwater runoff under realistic competitive conditions in terms of initial heavy metal concentrations, pH and ionic strength.     

Arsenic removal from water using natural iron mineral-quartz sand columns

The study has investigated the feasibility of using siderite-coated quartz sand and/or hematite-coated quartz sand columns for removing As from water. Arsenic-spiked tap water and synthetic As solution with As concentrations from 200 to 500 mug/L were used for the experiments. Since three coating methods employed to prepare siderite-coated quartz sand and hematite-coated quartz sand had no significant impact on As adsorption in batch tests, the column fillings were produced by means of the simplest one involving mechanically mixing the Fe mineral with quartz sand. Fixed bed tests show that the combination of siderite-coated quartz sand and hematite-coated quartz sand greatly promoted the column performance in removing As and the presence of As(III) in the influent improved the removal efficiency of the column. The relatively low capacity in treating As-spiked tap water arose from the suppression of FeCO(3) dissolution in the presence of high HCO(3)(-) concentration (333 mg/L), which consequently limited the formation of fresh Fe(III) oxides. However, the H(2)O(2)-conditioning greatly increased As adsorption capacity of the column for remediating As-spiked tap water. The Toxicity Characteristic Leaching Procedure (TCLP) test shows that the spent adsorbents were not hazardous and could be safely disposed of to landfill.     

Role of soil-derived dissolved substances in arsenic transport and transformation in laboratory experiments

Dissolved substances derived from soil may interact with both soil surfaces and with arsenic and subsequently influence arsenic mobility and species transformation. The purpose of this study was to investigate arsenic transport and transformation in porous media with a specific focus on the impact of soil-derived dissolved substances, mainly consisting of inorganic colloids and dissolved organic matter (DOM), on these processes. Arsenic transport and transformation through columns, which were packed with uncoated sand (UC) or naturally coated sand (NC) and fed with arsenate (AsV) or monomethylarsonic acid (MMA) spiked influents, were investigated in the presence or absence of soil-derived dissolved substances. The presence of soil-derived inorganic colloids and/or DOM clearly enhanced As transport through the column, with the fraction of As leached out of column (referring to the total amount added) being increased from 23 to 46% (UC) and 21 to 50% (NC) in AsV experiments while 46 to 64% (UC) and 28 to 63% (NC) in MMA experiments. The association of arsenic with DOM and the competitive adsorption between arsenic and DOM could account for, at least partly, the enhanced As movement. Distinct species transformation of As during transport through soil columns was observed. When AsV was the initial species spiked in the influent solutions, only arsenite (AsIII) was detected in the effluents for UC columns; while both AsIII (dominant) and AsV were present for NC columns, with AsIII being the dominant species. When MMA was initially spiked in the influent solutions, all method detectable As species, AsIII, AsV, MMA, and dimethylarsenic acid (DMA) were present in the effluents for both soil columns. These results indicate that risk assessment associated with As contamination, particularly due to previous organoarsenical pesticide applications, should take into account the role of soil-derived dissolved substances in promoting As transport and As species transformation.     

Sorption materials for arsenic removal from water: a comparative study

Five different sorption materials were tested in parallel for the removal of arsenic from water: activated carbon (AC), zirconium-loaded activated carbon (Zr-AC), a sorption medium with the trade name 'Absorptionsmittel 3' (AM3), zero-valent iron (Fe(0)), and iron hydroxide granulates (GIH). Batch and column tests were carried out and the behavior of the two inorganic species (arsenite and arsenate) was investigated separately. The sorption kinetics of arsenate onto the materials followed the sequence Zr-AC > GIH = AM3 > Fe(0) > AC. A different sequence was obtained for arsenite (AC > Zr-AC = AM3 = GIH = Fe(0)). AC was found to enhance the oxidation reaction of arsenite in anaerobic batch experiments. The linear constants of the sorption isotherms were determined to be 377, 89 and 87 for Zr-AC, AM3 and GIH, respectively. The uptake capacities yielded from the batch experiment were about 7gl(-1) for Zr-Ac and 5gl(-1) for AM3. Column tests indicated that arsenite was completely removed. The best results were obtained with GIH, with the arsenate not eluting before 13100 pore volumes (inflow concentration 1 mg l(-1) As) which corresponds to a uptake capacity of 2.3 mg g(-1) or 3.7 g l(-1).     

Transport of two naphthoic acids and salicylic acid in soil: experimental study and empirical modeling

In contrast to the parent compounds, the mechanisms responsible for the transport of natural metabolites of polycyclic aromatic hydrocarbons (PAH) in contaminated soils have been scarcely investigated. In this study, the sorption of three aromatic acids (1-naphthoic acid (NA), 1-hydroxy-2-naphthoic acid (HNA) and salicylic acid (SA)) was examined on soil, in a batch equilibrium single-system, with varying pH and acid concentrations. Continuous flow experiments were also carried out under steady-state water flow. The adsorption behavior of naphthoic and benzoic acids was affected by ligand functionality and molecular structure. All modeling options (equilibrium, chemical nonequilibrium, i.e. chemical kinetics, physical nonequilibrium, i.e. surface sites in the immobile water fraction, and both chemical and physical nonequilibrium) were tested in order to describe the breakthrough behavior of organic compounds in homogeneously packed soil columns. Tracer experiments showed a small fractionation of flow into mobile and immobile compartments, and the related hydrodynamic parameters were used for the modeling of reactive transport. In all cases, the isotherm parameters obtained from column tests differed from those derived from the batch experiments. The best accurate modeling was obtained considering nonequilibrium for the three organic compounds. Both chemical and physical nonequilibrium led to appropriate modeling for HNA and NA, while chemical nonequilibrium was the sole option for SA. SA sorption occurs mainly in mobile water and results from the concomitancy of instantaneous and kinetically limited sites. For all organic compounds, retention is contact condition dependent and differs between batch and column experiments. Such results show that preponderant mechanisms are solute dependent and kinetically limited, which has important implications for the fate and transport of carboxylated aromatic compounds in contaminated soils.     

Arsenic Removal from Contaminated Groundwater by Zero Valent Iron: a Mechanistic and Long-Term Performance Study

The present study investigated the application of zero valent iron to remediate the arsenic in naturally contaminated groundwater. A performance evaluation was conducted in the laboratory on groundwater contaminated with artificial arsenic using sodium arsenate (Na₂HAsO₄.7H₂O) to simulate the arsenic concentration in the groundwater. Batch and column experiments were performed to evaluate the arsenic removal capacity by zero valent iron and the removal mechanism. The flow rate (up-flow mode) was maintained for 180 days in each column. The results from both the batch and the column experiments showed that more than 99% of the arsenic was removed successfully. In the column experiments, the arsenic was efficiently removed and the arsenic concentration in the treated water decreased to below the limit of 10 μg /L (WHO's standard) even when the columns were packed with only 25% ZVI by volume. We used SEM and XRD to characterize the surface morphology and the corrosion layer which formed on pristine ZVI and arsenic-treated ZVI to elucidate the arsenic removal mechanism. XRD and SEM results revealed that ZVI gradually converted to a magnetite/maghemite corrosion product mixed with lepidocrocite. Adsorption followed by co-precipitation was an important pathway to removing the arsenic by ZVI. Our results suggest that ZVI, combined with sand, is a suitable candidate for the ex-situ treatment of groundwater in the neutral pH range and in the presence of dissolved oxygen.     

生物固定化锰砂/石英砂滤柱的除铁除锰效能比较

通过在锰砂及石英砂上固定自行分离的纤发茵属细菌,研究了生物固定化锰砂及石英砂滤柱的除铁除锰能力.从水厂成熟滤砂上分离出的纤发菌属细菌,经16S rDNA鉴定为却Lepto-thrix cholodnii(98%)、Leptothrix discophora(99%)、Leptothrix mobilis(99%).纤发菌属固定化锰砂及石英砂滤柱对铁的去除率均可达90%以上,但锰砂滤柱的处理能力高于石英砂滤柱.当DO为5 mg/L时,锰砂及石英砂滤柱对锰的平均去除量分别为0.9 ms/L和0.6 mg/L;当DO提高到9mg/L时,两滤柱对锰的平均去除量分别增加到1.45 ms/L和1.1 mg/L,相应的去除率分别从45%、34.5%提高到74.29%、59.32%.对生物膜形态的观察结果表明,纤发菌分泌的胞外聚合物与铁、锰氧化物形成了聚合体,同时还能观察到由嘉氏铁杆菌(Gallionella ferruginea)形成的麻花状沉淀物.     

海砂钢管混凝土柱耐腐蚀性能的试验和理论研究

目的是研究将海砂直接应用到钢管混凝土柱中的可行性。首先通过试验,测量了钢管海砂混凝土的腐蚀电流密度,结果表明海砂对钢管混凝土的腐蚀不大。然后运用有限元模型对海砂钢管混凝土的腐蚀做了模拟,模拟结果也表明海砂钢管混凝土的腐蚀量很低。试验和有限元模拟证明,海砂应用到实心钢管混凝土中是可行的。     

Manganese-oxide-coated alumina: a promising sorbent for defluoridation of water

In this study, adsorption potential of a new sorbent manganese-oxide-coated alumina (MOCA) was investigated for defluoridation of drinking water using batch and continuous mode experiments. The effects of different parameters such as pH, initial fluoride concentration and co-existing ions (usually present in groundwater sample) were studied to understand the adsorption behavior of the sorbent under various conditions. Optimum removal of fluoride ions occurred in a pH range of 4-7. Results of the present study indicate that fluoride adsorption rate and adsorption capacity of MOCA are far superior to that of activated alumina (AA), which was used as the base material for MOCA preparation. The MOCA can be effectively regenerated using 2.5% NaOH as eluent. The Langmuir equilibrium model was found to be suitable for describing the fluoride sorption on AA and MOCA. The maximum fluoride uptake capacity for MOCA and AA was found to be 2.85 and 1.08 mg g(-1), respectively. The kinetic results showed that the fluoride sorption to MOCA followed pseudo--second-order kinetics with a correlation coefficient greater than 0.98. The fluoride sorption capacity at breakthrough point for both the adsorbents was greatly influenced by bed depth. A bed depth service time (BDST) approach was adopted to describe the continuous flow system. The batch and column studies demonstrated the superiority of MOCA over AA in removing fluoride from the drinking water system.     

Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH)

Porous iron oxides are being evaluated and selected for arsenic removal in potable water systems. Granular ferric hydroxide, a typical porous iron adsorbent, is commercially available and frequently considered in evaluation of arsenic removal methods. GFH is a highly porous (micropore volume approximately 0.0394+/-0.0056 cm(3)g(-1), mesopore volume approximately 0.0995+/-0.0096 cm(3)g(-1)) adsorbent with a BET surface area of 235+/-8 m(2)g(-1). The purpose of this paper is to quantify arsenate adsorption kinetics on GFH and to determine if intraparticle diffusion is a rate-limiting step for arsenic removal in packed-bed treatment systems. Data from bottle-point isotherm and differential column batch reactor (DCBR) experiments were used to estimate Freundlich isotherm parameters (K and 1/n) as well as kinetic parameters describing mass transfer resistances due to film diffusion (k(f)) and intraparticle surface diffusion (D(s)). The pseudo-equilibrium (18 days of contact time) arsenate adsorption density at pH 7 was 8 microg As/mg dry GFH at a liquid phase arsenate concentration of 10 microg As/L. The homogeneous surface diffusion model (HSDM) was used to describe the DCBR data. A non-linear relationship (D(S)=3.0(-9) x R(p)(1.4)) was observed between D(s) and GFH particle radius (R(P)) with D(s) values ranging from 2.98 x 10(-12) cm(2)s(-1) for the smallest GFH mesh size (100 x 140) to 64 x 10(-11) cm(2)s(-1) for the largest GFH mesh size (10 x 30). The rate-limiting process of intraparticle surface diffusion for arsenate adsorption by porous iron oxides appears analogous to organic compound adsorption by activated carbon despite differences in adsorption mechanisms (inner-sphere complexes for As versus hydrophobic interactions for organic contaminants). The findings are discussed in the context of intraparticle surface diffusion affecting packed-bed treatment system design and application of rapid small-scale column tests (RSSCTs) to simulate the performance of pilot- or full-scale systems at the bench-scale.     

Treatment of atrazine in nursery irrigation runoff by a constructed wetland

To investigate the treatment capability of a surface flow wetland at a container nursery near Portland, Oregon, atrazine was introduced during simulated runoff events. Treatment efficiency was evaluated as the percent atrazine recovered (as percent of applied) in the water column at the wetland's outlet. Atrazine treatment efficiency at the outlet of the constructed wetland during a 7-d period ranged from 18-24% in 1998 (experiments 1-3) and 16-17% in 1999 (experiments 4 and 5). Changes in total flow, or frequency and intensity of runoff events did not affect treatment. For experiment 6 in 1999, where the amount, frequency, and duration of runoff events exceeded all other experiments, treatment was compromised. For all experiments, deethylatrazine (DEA) and deisopropylatrazine (DIA) accounted for 13-21% of the initial application. Hydroxyatrazine (HA) was rarely detected in the water. Organic carbon adsorption coefficients (Koc) were determined from batch equilibrium sorption isotherms with wetland sediment, and they decreased in the order of HA > DIA > atrazine > DEA. Static water-sediment column experiments indicated that sorption is an important mechanism for atrazine loss from water passing through the constructed wetland. The results of the MPN assay indicated the existence in the wetland of a low-density population of microorganisms with the potential to mineralize atrazine's ethyl side chain.     

Behaviour of heavy metals in soil beneath a landfill; Results of model experiments

Column experiments were set up in order to study the behaviour of heavy metals from landfill leachate in the soil. Special attention was given to the influence of fatty acids in the leachate on the mobility of lead, copper, nickel and zinc. In addition the influence of the kind of soil material was investigated. Of the six columns used in the experiments, three were percolated with synthetic landfill leachate and three with the same leachate without fatty acids. In both cases the three columns contained sand, sand mixed with fine clay particles and sand mixed with large clay aggregates. All experiments were carried out under anaerobic conditions. The soil solution of each column was periodically analysed. At the end of the experiments, after 7 months, the soil was analysed for precipitates and adsorption of metals. In the presence of fatty acids, breakthrough of respectively nickel, zinc and lead took place, whereas copper accumulated in the soil. In the absence of fatty acids precipitation and adsorption of the metals took place.     

Photoinactivation of virus on iron-oxide coated sand: enhancing inactivation in sunlit waters

Adsorption onto iron oxides can enhance the removal of waterborne viruses in constructed wetlands and soils. If reversible adsorption is not coupled with inactivation, however, infective viruses may be released when changes in solution conditions cause desorption. The goals of this study were to investigate the release of infective bacteriophages MS2 and ΦX174 (two human viral indicators) after adsorption onto an iron oxide coated sand (IOCS), and to promote viral inactivation by exploiting the photoreactive properties of the IOCS. The iron oxide coating greatly enhanced viral adsorption (adsorption densities up to ∼10⁹ infective viruses/g IOCS) onto the sand, but had no affect on infectivity. Viruses that were adsorbed onto IOCS under control conditions (pH 7.5, 10 mM Tris, 1250 μS/cm) were released into solution in an infective state with increases in pH and humic acid concentrations. The exposure of IOCS-adsorbed MS2 to sunlight irradiation caused significant inactivation via a photocatalytic mechanism in both buffered solutions and in wastewater samples (4.9 log₁₀ and 3.3 log₁₀ inactivation after 24-h exposure, respectively). Unlike MS2, ΦX174 inactivation was not enhanced by photocatalysis. In summary, IOCS enhanced the separation of viruses from the water column, and additionally provided a photocatalytic mechanism to promote inactivation of one of the surrogates studied. These qualities make it an attractive option for improving viral control strategies in constructed wetlands.     

Organic carbon removal and nitrification of high strength wastewaters using stratified sand filters

The current practice of spray irrigation of dairy parlour wastewaters is laborious and time consuming. Intermittent sand filtration systems may offer an alternative to spray irrigation when designed to remove organic carbon, nitrogen, phosphorus, coliforms and viruses from such wastewaters to allow discharge of the final effluent directly into receiving waters without damage to the environment. In this study two instrumented stratified sand filter columns (0.425 and 0.9 m deep, and both 0.3 m in diameter) were intermittently loaded for 439 days with synthetic dairy parlour washings at a number of hydraulic and organic loading rates. At a biochemical oxygen demand (BOD) loading of 22 g m(-2) d(-1), over 92% of the BOD and suspended solids in the wastewater was removed in the two filters and nitrification was complete. The 0.9 m column had a sustained ability to adsorb the influent phosphorus during the study period; however, the phosphorus adsorption capacity of the 0.425 m column began to decrease after approximately 30 days. Biomass, comprising hydrated extracellular polymers (exopolymers) and living and dead cells, accumulated in the 0.9 m column; it was assessed by sodium bromide tracer studies and by variations in the sand volumetric water contents using time domain reflectometry (TDR). The biomass growth increased the retention time of the wastewater in the filter media, and occurred mainly at the top of the first sand layer. Intermittent stratified sand filters appear to offer an effective and sustainable treatment process for the removal of BOD from high-strength wastewaters, and for the complete nitrification of ammonium.     

Fate and transport of 1278-TCDD, 1378-TCDD, and 1478-TCDD in soil-water systems

The most toxic dioxin is 2,3,7,8-tetrachlorodibenzo-p-dioxin (2378-TCDD), and obtaining comprehensive experimental data for this compound is challenging. However, several nontoxic isomers of 2378-TCDD exist, and can provide significant experimental evidence about this highly toxic dioxin. The goal of this study was to obtain experimental evidence for the fate and transport of 2378-TCDD in natural soils using its nontoxic isomers, 1,2,7,8-tetrachlorodibenzo-p-dioxin (1278-TCDD), 1,3,7,8-tetrachlorodibenzo-p-dioxin (1378-TCDD), and 1,4,7,8-tetrachlorodibenzo-p-dioxin (1478-TCDD). Batch sorption and miscible-displacement experiments, in various soils, were done using [4-(14)C]-radiolabeled TCDDs, while metabolism of these compounds was monitored. The results from the batch experiments indicated a high sorption affinity of all the TCDD isomers to soils and a strong correlation to organic matter (OM) content. 1278-TCDD, 1378-TCDD and 1478-TCDD (TCDDs) were more tightly bound to the soil with high OM than to the soil with low OM; however, it took a longer contact time to approach sorption equilibrium of TCDDs in the soil with high OM. Miscible-displacement breakthrough curves indicated chemical nonequilibrium transport, where there was a rate-limited or kinetic sorption that was likely caused by OM. Combustion analyses of extracted soil from the soil columns showed that most TCDDs were adsorbed in the top 1-5 cm of the column. These column combustion results also showed that sorption was correlated to specific surface and soil depth, which suggested the possibility of colloidal transport.     

Effect of interferences on the breakthrough of arsenic: rapid small scale column tests

The influences of three important interferences (silica, phosphate, and vanadate) and the effect of different pH levels and initial arsenate concentrations on the breakthrough of arsenic in adsorptive media columns were examined by using the Rapid Small Scale Column Test with a 3⁵⁻² fractional factorial design. Three commercially available adsorbents used for arsenic removal (E33, GFH and Metsorb) were tested. Results indicated that GFH was more susceptible to water quality changes than Metsorb and E33 under conditions tested. GFH also adsorbed more anions than the other two media. The pH was the factor that had the most impact on the performance of the columns, followed by arsenic concentration and silica concentration. Lowering pH from 8.3 to 7.0 resulted in an increase of the mean bed volume treated until 10 μg/L arsenic breakthrough by 40, 12 and 18 thousands BV treated by GFH, E33 and Metsorb columns, respectively. However, at high silica concentration, lowering pH did not increase the performance of the media. GFH and Metsorb were more sensitive to changes in arsenic concentration at low pH than at high pH. Although vanadium and phosphate were previously reported to reduce arsenic adsorption in batch tests, in column mode with the presence of competitors, their effect was insignificant compared to that of pH, arsenic or silica under the conditions used in this study.     

Removal of arsenic using hardened paste of Portland cement: batch adsorption and column study

Hardened paste of Portland cement (HPPC) has been used as a low-cost adsorbent for the removal of arsenic from water environment. Results from the batch experiments, conducted at an initial concentration of 0.2 ppm of arsenate, suggest arsenate removal up to 95%. Kinetic profiles were developed for various conditions. Effects of adsorbent dose, common ions such as Ca(2+), Mg(2+), Fe(3+), Fe(2+), Cl(-), SO(4)(2-), NO(3)(-), PO(4)(3-) and of pH were studied in detail. Adsorption isotherm studies revealed that the Freundlich isotherm was followed with a better correlation than the Langmuir isotherm. Arsenite could also be removed up to approximately 88% using the same material, HPPC. Finally, column studies were undertaken involving the new HPPC to check the suitability of the material for the removal of total arsenic content from water body. Kinetic experiments for the removal of arsenic by column studies revealed a film diffusion mechanism.     

Study of pyrene biodegradation capacity in two types of solid media

Removal of pyrene, a representative PAH, was studied using laboratory tests in two different types of solid media: an organic matter collected on the surface of a vertical flow constructed wetland (VFCW) and a formulated clay silicate sand (inorganic matter). The aim of this study was to evaluate the capacity of pyrene biodegradation in these media in order to use them for treating run-off water. The sorption process, the kinetics of pyrene biodegradation and the influence of selected bacteria were also investigated. The sorption process was evaluated by adsorption isotherms and desorption kinetics using a batch equilibration method. The adsorption coefficient values of 28.8 and 2.1 for the organic and the inorganic matter respectively, confirmed the relationship of adsorption with organic carbon content. A small proportion of the sorbed pyrene was available for desorption (8% and 15% for the organic and the inorganic matter, respectively), indicating that sorption was partially irreversible, with the presence of hysteresis. For the formulated clay silicate sand inoculated with a specific bacteria (Mycobacterium sp.6PY1), selected for its ability to degrade PAHs, pyrene removal was complete in 32 days. With the organic matter, these values ranged from 40% to 95% for the different experiments, following a lag time of 3 weeks before observation of a significant degradation. Indigenous bacterial species in the organic medium had the metabolic capacity to degrade pyrene, and microbial populations pre-exposed to the PAH degraded pyrene faster than similar unexposed populations. Three metabolites of pyrene degradation by Mycobacterium were found. They accumulated in both organic and inorganic matter, indicating that the enzymes catalyzing them have slow kinetics.     

微生物固化砂柱效果电阻率评价研究

目前尚没有简便可行的方法对现场微生物固化效果进行评价,因此,提出采用便捷无损的电阻率法评价砂土的固化效果.首先对微生物固化砂柱的电阻率与孔隙率、含水率和碳酸钙含量的关系进行研究,然后研究了电阻率和无侧限抗压强度的关系,并提出综合参数N表示固化砂柱的孔隙率、含水率和碳酸钙含量,研究综合参数与固化砂柱电阻率和无侧限抗压强度...