Microemulsion‐mediated removal of residual gasoline from soil columns

In situ pumping of micellular solutions of surfactant (S) and cosurfactant (CoS) in water (W) through contaminated soils or aquifers offers potential for enhanced remediation of residual nonaqueous‐phase liquids (NAPLs). Extremely low interfacial tension generated between a W/S/CoS mixture and residual NAPL in soil pores may initially mobilize the NAPL, which is then transported temporarily as a separate phase by immiscible displacement. The NAPL is then solubilized by micro‐emulsification as the W/S/CoS mixture forms a stable W/S/CoS/NAPL micro‐emulsion that undergoes miscible displacement through the pore space. This remediation technique was tested under laboratory conditions by sequentially flushing a saline solution and a W/S/CoS mixture through columns of a sandy soil recently contaminated with residual leaded gasoline (LG). Prior to the flushings, the soil was initially contaminated by applying a W/S/CoS/LG microemulsion. A simple conceptual transport model with kinetic clogging of soil pores adequately described breakthrough curves for gasoline and organolead in the soil columns.     

Biodegradation of Residual Dense Nonaqueous-Phase Liquid Tetrachloroethene: Effects on Mass Transfer

The mass emissions rate of contaminants from nonaqueous-phase liquids (NAPLs) is a driving factor in remediation efforts, whether those efforts are designed to remove, transform, or stabilize the entrapped NAPL or down-gradient aqueous concentrations. Enhancement of mass flux from NAPL source zones has been previously reported in the presence of microbial reductive dechlorination activity in systems containing NAPL with a low proportion of tetrachloroethene (PCE) or a low residual saturation (e.g., 2%). The results reported here demonstrate reductive dechlorination of PCE at residual saturations of 35%, obtained under two different column flow velocities and NAPL configurations. Mass flux in biotic columns was approximately 45% greater than that in uninoculated columns, due to both the presence of daughter products and higher concentrations of PCE in the effluent from biotic columns. Daughter product concentrations were greater in columns with NAPL emplaced only in the lower quarter compared to those with NAPL throughout, and in columns run at the slower velocity. The elevated PCE concentrations in biotic column effluents suggest the influence of microbially generated surfactants, which was supported by surface tension measurements. These results demonstrate the potential significance of bioactivity within NAPL source zones on NAPL longevity and down-gradient aqueous concentrations.     

NAPL mobility of OPA-containing sediments

ABSTRACT

In situ deposited non-aqueous phase liquid (IDN) sediments have unique characteristics that inherently mitigate the movement of separate phase liquids. IDN sediments are composed of oil-particle aggregates (OPAs). OPAs consist of an oil bead or globule with attached solid particles, such as clay platelets, silt and sand granules, and/or organic materials. IDN sediments develop at locations where a continual or near continual discharge of non-aqueous phase liquids (NAPLs) have occurred over a period of time. IDN sediments consist of an open network of small pores where fluids are retained. Although the pore structure is very open, the pore openings are relatively small, which appears to inhibit fluid movement. In particular, capillary pressure analyses indicate that NAPL was not generally released until pressures of at least 15 pounds per square inch (psi) were induced. In addition, centrifuge testing at 1,000 G shows that NAPL immobility is observed in samples at NAPL saturations as high a 12%. These data suggest that NAPL is retained within the smallest pores and is encapsulated within a network of larger pores filled with water. Although the sediment contains NAPL, this original OPA structure appears to inhibit the oil beads from coalescing, preventing NAPL flow.     

Use of surfactants and slurrying to enhance the biodegradation in soil of compounds initially dissolved in nonaqueous-phase liquids

A study was conducted to find means of enhancing the biodegradation of hydrophobic organic compounds in nonaqueous-phase liquids (NAPLs). The effects of surfactants, identity of the NAPL and agitation was investigated. When present in NAPLs, phenanthrene, di-(2-ethylhexyl) phthalate (DEHP) and biphenyl were mineralized slowly in soil. Addition of Triton X-100 or Alfonic 810-60 did not enhance the degradation of phenanthrene initially in hexadecane or dibutyl phthalate. Slurrying the soil increased the rate and extent of mineralization of phenanthrene initially in hexadecane but not in dibutyl phthalate. Addition of either of the two surfactants to the slurries did not promote the transformation. Triton X-100, Alfonic 810-60 and Tergitol 15-S-9 below their critical micelle concentrations increased the rate and sometimes the extent of mineralization in soil slurries of phenanthrene initially in 2,2,4,4,6,8,8-heptamethylnonane, but other surfactants were not stimulatory. Slurrying the soil promoted the initial mineralization of DEHP initially in dibutyl phthalate, and Alfonic 810-60 and Triton X-100 further stimulated the rate and extent of degradation in the slurries. Alfonic 810-60 increased the extent of mineralization in slurries of biphenyl in hexadecane but not in dibutyl phthalate, cyclohexane, kerosene or two oils. Little mineralization of biphenyl or DEHP initially in dibutyl phthalate occurred in soil slurries, but Tween 80, Tergitol 15-S-40 and Tergitol 15-S-9 increased the extent of mineralization. However, vigorous agitation of the slurries of soil acclimated to DEHP or the use of small volumes of the NAPL resulted in marked enhancement of the degradation. Thus, biodegradation of constituents of NAPLs in soil can be increased by the use of some surfactants, slurrying or intense agitation, but the effect will vary with the NAPL and the constituents.     

Feasibility of in situ implementation of vibrations to mobilize NAPL ganglia

A growing number of incidents of nonaqueous phase liquid (NAPL) spills in the recent past have warranted development of innovative and cost‐effective remediation technologies. Of particular concern is the entrapment of LNAPL (NAPL lighter than water) in the form of ganglia or blobs near the water table by virtue of strong capillary forces. The residual ganglia are the leftover component after pumping of free product and typically occupy 20 to 60% of the pore space. Mobilization of these ganglia would require unrealistically high hydraulic gradients and is often beyond the scope of pump‐and‐treat processes. This paper deals with the feasibility of in situ implementation of localized vibrations for controlled mobilization and collection of LNAPL ganglia. Specifically, the paper covers three components. First, the principles involved in soil‐water‐NAPL interactions under the influence of vibrations are discussed. The effects of vibrations on a soil‐NAPL‐water medium are postulated in terms of pore structure and relative density changes, changes in the permeability of the medium as a result of the changes in pore structure, and development of cyclic pore pressures. Second, results from bench‐scale experiments are presented that involved vibrating contaminated soils under the simultaneous influence of hydraulic gradients. A bench‐scale model consisting of a vibrator integrated with an injection and pumping system was found to be successful in these experiments. The results from the tests showed that up to 85% removal of ganglia can be achieved using this process. Third, the principles involved in the vibratory mobilization were applied to in situ conditions to develop a methodology to estimate the zone of influence of the process. The analogy between this process and an existing geotechnical process known as vibroflotation is exploited to demonstrate the methodology.     

Bacterial Adhesion to Soil Contaminants in the Presence of Surfactants

It has been proposed that addition of surfactants to contaminated soil enhances the solubility of target compounds; however, surfactants may simultaneously reduce the adhesion of bacteria to hydrophobic surfaces. If the latter mechanism is important for the biodegradation of virtually insoluble contaminants, then the use of surfactants may not be beneficial. The adhesion of a Mycobacterium strain and a Pseudomonas strain, isolated from a creosote-contaminated soil, to the surfaces of highly viscous non-aqueous-phase liquids (NAPLs) was measured. The NAPLs were organic material extracted from soils from two creosote-contaminated sites and two petroleum-contaminated sites. Cells suspended in media with and without surfactant were placed in test tubes coated with an NAPL, and the percentages of cells that adhered to the surface of the NAPL in the presence and absence of surfactant were compared by measuring optical density. Test tubes without NAPLs were used as controls. The presence of either Triton X-100 or Dowfax 8390 at a concentration that was one-half the critical micelle concentration (CMC) inhibited adhesion of both species of bacteria to the NAPLs. Both surfactants, when added at concentrations that were one-half the CMCs to test tubes containing previously adhered bacteria, also promoted the removal of the cells from the surfaces of the NAPL-coated test tubes. Neither surfactant was toxic to the bacteria. Further investigation showed that a low concentration of surfactant also inhibited the growth of both species on anthracene, indicating that the presence of a surfactant resulted in a reduction in the uptake of the solid carbon source.     

Effects of emulsion viscosity during surfactant‐enhanced soil flushing in porous media

Surfactants can potentially improve the efficiency of pump‐and‐treat technology for remediation of aquifers contaminated by nonaqueous phase liquids (NAPLs). However, the formation of emulsions during the removal process can Increase the viscosity in the system. This can result in pore clogging and reduction of flow, which inhibits the contaminant removal process. Formation of viscous emulsions has been identified in previous research as one of the probable causes for in situ field test failures using surfactant‐enhanced soil‐flushing technology. However, the effects of in situ emulsification and viscosity increases have not been quantified previously. The purpose of this article is to investigate effects of in situ emulsification on the remediation process. Laboratory column studies examined the mobilization of m‐xylene from porous media using a 1% alcohol ethoxylate surfactant solution (Witconol® SN90). Effects of in situ emulsification were determined. Glass columns (1.1 cm i.d. × 30 cm) were packed with 0.2‐mm glass beads to model soil media. Viscosities of emulsion solutions prepared with 1 % SN90 and various concentrations of m‐xylene were measured and compared with effluent collected during column‐flushing experiments. It was determined that as m‐xylene concentration in the emulsion solution Increases, viscosity increases. Viscosity increases caused a decrease in relative permeability within the soil column. As a result, the hydraulic gradient required to maintain a constant flowrate of 1.1 ml/min (using a syringe pump) through the soil column increased. Results show that a relatively small increase in viscosity could have a noticeable effect on the mobilization process. It is suggested that the surfactant/contaminant systems be screened to determine emulsion theology and the potential effects on the remediation process. The use of low‐concentration alcohol cosurfactants to reduce system viscosity was evaluated and was shown to be ineffective.     

Physical properties of oil-particle aggregate (OPA)-containing sediments

ABSTRACT

Sediments composed of oil-particle aggregates (OPAs) have unique physical characteristics. These in situ deposited sediments develop at locations where a continual or nearly continual discharge of non-aqueous phase liquids (NAPLs) have occurred, or are occurring through time. The NAPL discharged into the surface water body interacts with suspended particles in the water column. The particles adhere to the suspended NAPL, which generally is in the form of a bead, and produce a discrete aggregate. As the aggregate grows in response to additional particle adherence, the density of the unit increases and deposition occurs. The resulting sediment consists of a collection of discrete OPAs that form a network with small pores, where oil is tightly bound and/or contained. Porosity, water content, and dry bulk density measurements indicate the sediment formed by OPA deposition is physically unique. Although the sediment consists of a very open pore structure, the pore openings are relatively small, typically being less than 5 microns in diameter. These small pores inhibit fluid movement. Results of physical property testing suggest the OPA structure is retained upon deposition. Although the sediment contains NAPL, this original OPA structure inhibits the oil beads from coalescing, which would enable NAPL flow.     

Biodegradation kinetics of naphthalene in nonaqueous phase liquid-water mixed batch systems: comparison of model predictions and experimental results

A model is formulated to describe dissolution of naphthalene from an insoluble nonaqueous phase liquid (NAPL) and its subsequent biodegradation in the aqueous phase in completely mixed batch reactors. The physicochemical processes of equilibrium partitioning and mass transfer of naphthalene between the NAPL and aqueous phases were incorporated into the model. Biodegradation kinetics were described by Monod's microbial growth kinetic model, modified to account for the inhibitory effects of 1,2-naphthoquinone formed during naphthalene degradation under certain conditions. System parameters and biokinetic coefficients pertinent to the NAPL-water systems were determined either by direct measurement or from nonlinear regression of the naphthalene mineralization profiles obtained from batch reactor tests with two-component NAPLs comprised of naphthalene and heptamethylnonane. The NAPLs contained substantial mass of naphthalene, and naphthalene biodegradation kinetics were evaluated over the time required for near complete depletion of naphthalene from the NAPL. Model predictions of naphthalene mineralization time profiles compared favorably to the general trends observed in the data obtained from laboratory experiments with the two-component NAPL, as well as with two coal tars obtained from the subsurface at contaminated sites and composed of many different PAHs (polycyclic aromatic hydrocarbon compounds). The effects of varying the NAPL mass and the naphthalene mole fractions in the NAPL are discussed. It was observed that the time to achieve a given percent removal of naphthalene does not change significantly with the initial mass of naphthalene in a fixed volume of the NAPL. Significant changes in the mineralization profiles are observed when the volume (and mass) of NAPL in the system is changed.     

Complex NAPL Site Characterization Using Fluorescence Part 1: Selection of Excitation Wavelength Based on NAPL Composition

Fluorescence has been demonstrated to be a viable method for detecting non-aqueous phase liquid (NAPL) contaminants comprised of polycyclic aromatic hydrocarbons (PAHs). Commercially available cone penetrometer (CPT)induced fluorescence based sensor platforms can be used to detect NAPLs such as petroleum oils and lubricants in-situ. In addition, these approaches can be used to detect dense non-aqueous phase liquid (DNAPL) source zones by detecting commingled oils, fuels, and naturally oc curring organic materials entrained by or in solution with DNAPLs and carried to depths below the water table. The currently available CPT-based fluorescence systems are typically restricted to a single wavelength excitation source, each demonstrating specific advantages and disadvantages with respect to detection capabilities for partic ular fluorophores. Several neat NAPLs and mixtures were analyzedfor specificfluores-cence characteristics to determine the optimal excitation source for site characterization efforts. Commercially available cone penetrometer based fluorescence detection systems were ranked according to the potential for likelihood of detection. Our work demon strates that an optimal range of excitation wavelength can be determined for specific fluorophores within NAPL mixtures, and that available systems can be ranked based on the specific contaminant and site characteristics. We have identified optimal excitation sourcesfor a number of common NAPL mixtures, including petroleum-basedfuels and a lubricant mixed with a chlorinated solvent.     

Optimizing biodegradation of phenanthrene dissolved in nonaqueous-phase liquids

 A study was conducted to optimize the biodegradation in soil slurries of phenanthrene initially dissolved in nonaqueous-phase liquids (NAPLs). The slow rate of degradation of phenanthrene in dibutyl phthalate was increased by addition of phenanthrene-degrading microorganisms to soil slurries containing the NAPL. The rate was further increased and the acclimation phase was shortened if the inoculum was grown in a medium containing the hydrocarbon and the phthalate before addition to the slurries. Composition of the growth medium only shortened the acclimation but had no effect on the rate. Vigorous agitation increased the rate and extent of mineralization of phenanthrene in dibutyl phthalate. The effect of temperature was affected by the presence and identity of the inoculum. Rapid and extensive mineralization of phenanthrene initially present in hexadecane and diesel oil were attained by use of intense agitation of the NAPL/soil slurry and inoculation with microorganisms grown in the presence of the NAPLs, but the influence of these variables was less with other NAPLs. Vigorous agitation and addition of an inoculum 24 h after introduction of a nonionic surfactant enhanced biodegradation of phenanthrene initially in 150 Bright stock oil and dibutyl phthalate. The results suggest improved means for the bioremediation of sites contaminated with NAPLs. Received: 17 May 1995/Received revision: 1 August 1995/Accepted: 22 August 1995     

污染土壤淋洗修复技术研究进展

土壤淋洗修复技术是一种行之有效的污染土壤治理技术,适合于快速修复受高浓度重金属和有机物污染土壤与沉积物。本文综述了土壤淋洗修复技术的特点、技术流程、土壤淋洗剂的研究与应用进展,指出异位土壤淋洗修复技术因修复效果稳定,易于实现系统控制和废弃物减量化等优点而具有更广阔的应用前景,天然螯合剂和生物表面活性剂等环境友好型淋洗剂正逐渐取代人工螯合剂和化学表面活性剂成为土壤淋洗剂研究的主流方向,而现代超分子化学的引入和发展有可能对复合污染土壤的高效淋洗修复研究产生新的影响。     

Complex NAPL Site Characterization Using Fluorescence Part 2: Analysis of Soil Matrix Effects on the Excitation/Emission Matrix

Commercially available cone penetrometer (CPT)fluorescence based sensor platforms have been used to detect non-aqueous phase liquids (NAPLs), such as petroleum oils and lubricants, in situf or more than a decade. These approaches have also been used to detect dense non-aqueous phase liquid (DNAPL) source zones by detecting commingled oilsfuels, and naturally occurring organic materials entrained by DNAPLs and carried to depths below the water table. Several neat NAPLs and mixtureswere added to various soil types and analyzedfor specific fluorescence characteristics to determine the optimal excitation source for site characterization efforts. Using excitationlemission matrices (EEMs), we demonstrate that an optimized excitation wavelength can be determinedfor specific fiuowphores within the NAPL mixtures, and that available systems can be ranked based on the specific contaminant and site soil types. An optimal excitation wavelength yields the maximum fluorescence within an EEM spectrum. We ranked commercially available cone penetrometer fluorescence detection systems according to the potential for ease of detection based on maximum fluorescence response. When soils were added tocomplexNAPLmixtures,analytefluorescence emissionwasattenuatedinpreferential portions of the EEM, leading to differences in the optimal excitation source wavelength. Furthermore, impure silica-containing minerals impact the emission signal, potentially leading to incorrect conclusionsf or several commercially available systems. Our find ings suggest that afrequency-agile (e.g., tunable excitation source) probe system would be superior to any other system commercially available, provided the system would be relatively easy to operate and would have rapid in-situ EEM generating capabilitiesfo r optimization in the field.     

The Effectiveness of Surfactants for Remediation of Organic Pollutants in the Unsaturated Zone

In laboratory experiments performed to evaluate the efficiency of surfactant flushing for remediation of non-aqueous phase liquid (NAPL) in the unsaturated zone, less than 0.001% of the original mass of tetra-chloroethylene (PCE) remained in the column after 15 pore volumes of a 1% sorbitan monooleate solution or after 7 pore volumes of a 1% Ethomid O/17 solution were passed through the columns. Mass removed as dissolved phase in the effluent accounted for more than 90% of PCE removed; the remainder was lost by volatilization. To determine the influence of parameters that may affect the remediation process, column tests were repeated with different values of parameters, including grain size, application rate, surfactant type, surfactant concentration, and solution viscosity. The results from the column experiments were simulated with the two-dimensional finite element computer code for multiphase flow and transport, MOTRANS. Results of the simulation were similar to those from the experiments. Both experimental and modeling results suggest that surfactant flushing has a great potential to remove mass from NAPL in the unsaturated zone.     

Quantitative Assessment of LNAPL Retention in Soil Porous Media

The presence of hydrocarbon contaminants in the vadose zone is a serious hazard for environment quality. Moreover, there is an urgent need for accurate and reliable knowledge of the hydraulics of hydrocarbon contaminants in porous media to enhance efficiency of NAPLs remediation methods. The objective of this study was to quantitatively assess the hydraulic properties of different porous media with petroleum, kerosene, diesel fuel, and gasoline. The related retention curves were then experimentally obtained. Parameters of the soils retention curves were obtained based on van Genuchten (1980), Brooks-Corey (1964), and Campbell (1974) retention models. The accuracy of models was then assessed by some statistics. The results indicated that, in most cases, air entry value was significantly increased in a petroleum retention curve despite the fact that it was decreased for other NAPLs. The pore size distribution parameters (i.e., n, m, λ, and 1/b) of diesel fuel, kerosene, and gasoline did not change considerably compared to water retention curve. The Leverett (1941) scaling function was adopted to scale soil-fluid retention curves data in two-phase systems. The results indicated that, except for a silty clay medium and petroleum, the Leverett (1941) J-function could scale the LNAPL retention curves based on the water retention curve data.     

Basis for formulating biosurfactant mixtures to achieve ultra low interfacial tension values against hydrocarbons

Biosurfactants could potentially replace or be used in conjunction with synthetic surfactants to provide for more cost-effective subsurface remediation. The design of surfactant formulations that are effective in lowering interfacial tension (IFT), which is necessary to mobilize entrapped hydrocarbons, requires information about the surface-active agent (surfactant) and the targeted non-aqueous phase liquids (NAPL). We hypothesized that biosurfactant and synthetic surfactant mixtures can be formulated to provide the appropriate hydrophobic/hydrophilic conditions necessary to produce low IFT against NAPLs, and that such mixtures will produce synergism that make them more effective than individual biosurfactants or synthetic surfactants. Our work tested the interfacial activity of biosurfactants from individual strains and mixtures of biosurfactants from different strains with and without a synthetic surfactant. Multiple regression analysis showed that, for lipopeptide biosurfactants produced by various Bacillus species, the interfacial activity against toluene depended on the relative proportions of 3-OH-C₁₄, C₁₅, C₁₆, and C₁₈ in the fatty acid tail. As the fatty acid composition became more heterogeneous the system produced lower IFT against toluene. In mixtures of lipopeptide biosurfactants with the more hydrophilic, rhamnolipid biosurfactant, the IFT against toluene decreased as the percentage of the 3-OH C₁₄ fatty acid increased in the lipopeptide. Mixtures of lipopeptide biosurfactants with the more hydrophobic synthetic surfactant, C12, C13-8PO SO₄Na, were able to produce low IFT against hexane and decane. In general, we found that lipopeptide biosurfactants with a heterogeneous fatty acid composition or mixtures of lipopeptide and rhamnolipid biosurfactants lowered the IFT against hydrophilic NAPLs. Conversely, mixtures of lipopeptide biosurfactants with a more hydrophobic synthetic surfactant lowered the IFT against hydrophobic NAPLs.     

Alteration in cell surface properties of <Emphasis Type="Italic">Burkholderia</Emphasis> spp. during surfactant-aided biodegradation of petroleum hydrocarbons

Chemical surfactants may impact microbial cell surface properties, i.e., cell surface hydrophobicity (CSH) and cell surface charge, and may thus affect the uptake of components from non-aqueous phase liquids (NAPLs). This work explored the impact of Triton X-100, Igepal CA 630, and Tween 80 (at twice the critical micelle concentration, CMC) on the cell surface characteristics of Burkholderia cultures, Burkholderia cepacia (ES1, aliphatic degrader) and Burkholderia multivorans (NG1, aromatic degrader), when grown on a six-component model NAPL. In the presence of Triton X-100, NAPL biodegradation was enhanced from 21% to 60% in B. cepacia and from 18% to 53% in B. multivorans. CSH based on water contact angle (50–52°) was in the same range for both strains while zeta potential at neutral pH was −38 and −31 mV for B. cepacia and B. multivorans, respectively. In the presence of Triton X-100, their CSH increased to greater than 75° and the zeta potential decreased. This induced a change in the mode of uptake and initiated aliphatic hydrocarbon degradation by B. multivorans and increased the rate of aliphatic hydrocarbon degradation in B. cepacia. Igepal CA 630 and Tween 80 also altered the cell surface properties. For B. cepacia grown in the presence of Triton X-100 at two and five times its CMC, CSH increased significantly in the log growth phase. Growth in the presence of the chemical surfactants also affected the abundance of chemical functional groups on the cell surface. Cell surface changes had maximum impact on NAPL degradation in the presence of emulsifying surfactants, Triton X-100 and Igepal CA630.     

Remediation of Gulf War Oil Spill Contaminated Soil by a Subcritical Water Extraction Process: Oil Removal,Recovery, and Degradation

Due to the unique properties of subcritical water (marked change in water's dielectric constant and viscosity), the extraction by subcritical water offers a great opportunity to remediate soil contaminated with organic pollutants as an alternative and green remediation method. In this study, subcritical water extraction is proposed as an efficient remediation technique for the Gulf War oil spill contaminated soil. The subcritical water extraction experiment was carried out in a lab-scale continuous flow apparatus. The three major operating factors, temperature, time and water flow rate, were evaluated in terms of optimum removal efficiency. The results show that crude oil removal depended largely on water temperature, whereas an extraction run time higher than 1 h and a water flow rate higher than 1.5 mL/min marginally or negatively affected removal efficiency. During subcritical water treatment at 300°C for 1 h at a flow rate of 1.5 mL/min, removal efficiency was almost 95%. Under these operating conditions, the subcritical water treatment demonstrated a similar removal efficiency to those of organic solvents like acetone. In contrast, the efficiency of oil recovery decreased with an increase in extraction temperature, due to degradation by a water self-oxidizing agent. Several degradation products identified in the treated soil and in the effluent sample (which initially were absent in the contaminated soil) were oxygen-containing aromatic compounds, confirming the oxidation-degradation.     

Temperature effect on acetate and propionate consumption by sulfate-reducing bacteria in saline wastewater

Seawater toilet flushing, seawater intrusion in the sewerage, and discharge of sulfate-rich industrial effluents elevates sulfate content in wastewater. The application of sulfate-reducing bacteria (SRB) in wastewater treatment is very beneficial; as for example, it improves the pathogen removal and reduces the volume of waste sludge, energy requirement and costs. This paper evaluates the potential to apply biological sulfate reduction using acetate and propionate to saline sewage treatment in moderate climates. Long-term biological sulfate reduction experiments at 10 and 20 °C were conducted in a sequencing batch reactor with synthetic saline domestic wastewater. Subsequently, acetate and propionate (soluble organic carbon) conversion rate were determined in both reactors, in the presence of either or both fatty acids. Both acetate and propionate consumption rates by SRB were 1.9 times lower at 10 °C than at 20 °C. At 10 °C, propionate was incompletely oxidized to acetate. At 10 °C, complete removal of soluble organic carbon requires a significantly increased hydraulic retention time as compared to 20 °C. The results of the study showed that biological sulfate reduction can be a feasible and promising process for saline wastewater treatment in moderate climate.     

水生植物-微生物联合去除水体有机污染物的研究进展

近年来,随着经济的快速发展,大量有机化合物随着工业废水和生活污水排放进入水体,严重破坏了水环境的生态平衡,威胁着水生生物及人类健康。植物-微生物联合修复技术因具有修复效率高、持续时间长、投入成本低,而且不会产生二次污染等特点,在水体有机污染治理中受到了人们的广泛关注。本文综述了近年来水生植物-微生物联合去除水体有机污染物的应用现状,详细阐述了水生植物-微生物联合修复过程中的研究方法、作用机制及影响因素。以期不断完善和优化水生植物-微生物联合修复技术,为实现水环境有机物污染的统筹高效治理提供参考。