Enhanced Solubility and Biodegradation of Naphthalene with Biosurfactant

Biosurfactant was produced by fermenting kerosene and used vegetable oil using a Pseudomonas sp. under nonsterile conditions. The biosurfactant at a concentration of 0.5 g∕L and pH of 10.5 lowered the surface tension of water to 25 mN∕m. The biosurfactant was used to enhance the solubility of naphthalene, and the results are compared to an anionic (sodium dedecyl sulfate) and a nonionic (Triton X-100) surfactant. The biosurfactant (5 g∕L at pH of 7) enhanced the solubility of naphthalene to more than 30 times its aqueous solubility. Solubilized naphthalene in Triton X-100 and biosurfactant solutions was biodegraded by the same microorganism that produced the biosurfactant. Naphthalene solubilized in biosurfactant and Triton X-100 (400–600 mg∕L) was biodegraded in 40 days and 100 h, respectively. Naphthalene in the amount of 30 mg∕L was degraded by the Pseudomonas sp. in 2 days. The biosurfactant was also biodegraded during the biodegradation of naphthalene, but this was not the case with Triton X-100. The biodegradation of the biosurfactant appeared to compete with the biodegradation of naphthalene. Sodium dedecyl sulfate inhibited the biodegradation of naphthalene at the conditions studied.     

Comparison of Potassium Permanganate and Hydrogen Peroxide as Chemical Oxidants for Organically Contaminated Soils

Laboratory experiments were completed to compare the treatment efficiency of KMnO4 with H2O2 (alone or with amendments) for sand and silty clay soil contaminated with either a mixture of volatile organic compounds (VOCs) [trichloroethylene (TCE), tetrachloroethene (PCE), and 1,1,1-trichloroethane (TCA)] or semivolatile organic compounds (SVOCs) (naphthalene, phenanthrene, and pyrene). The relatively treatment effects of soil type, oxidant loading rate and dosing, and reaction period, as well as the use of surfactant or iron amendments and pH adjustment were examined using batch experiments with contaminated soil slurries. When KMnO4 was applied to low organic carbon, acidic, or alkaline soils, at loading rates of 15–20 g∕kg it was found to degrade consistently 90% or more of the alkene VOCs (TCE and PCE) and 99% of the polyaromatic SVOCs (naphthalene, pyrene, and phenanthrene). H2O2 was more sensitive to contaminant and soil type and VOC treatment efficiencies were somewhat lower as compared with KMnO4 under comparable conditions, particularly with the sandy soil and even when supplemental iron was added. In clay soil, H2O2 with iron addition degraded over 90% of the SVOCs present compared with near zero in sandy soil, unless the pH was depressed to pH 3 and iron amendments were increased, whereby the treatment efficiency in the sandy soil was increased slightly. With both H2O2 and KMnO4, treatment efficiency increased to varying degrees as the oxidant loading rate (g∕kg) and reaction time (h) were increased. Multiple oxidant additions or surfactant addition were not found to have any significant effect on VOC treatment efficiency. Also, very limited TCA treatment was observed with either H2O2 or KMnO4.     

Treatment of Arsenic-Contaminated Soils. ?I: Soil Characterization

Industrial sites frequently have arsenic-contaminated soils as a result of repeated applications of arsenic herbicides. Four such sites were investigated to determine the suitability of cement-based solidification∕stabilization (S∕S) for in situ soil treatment. Arsenic concentrations ranged up to about 2,000 ppm in the soil, although leachability was relatively low. No toxicity characteristic leaching procedure leachates showed As concentrations as high as 5 mg∕L. The low leachability appears to be due, at least in part, to iron present in the soil. Although soils with higher As concentrations generally showed greater leachability, a somewhat stronger relationship existed between the percentage of As in the soil that was leached and the iron concentration in the soil. Another factor working in favor of the success of S∕S in the present cases is the sandy character of the soils with little clay or organic content. Thus, the quartz sand will serve as an aggregate and should not offer any interferences to cement hydration. A third favorable circumstance is afforded by the oxidizing character of the soils. The weathered arsenic present in the soils should be in the form of As(V), and arsenate salts present a wider range of possibilities for precipitation of insoluble arsenic species than arsenite salts. A significant variable with the potential to affect S∕S is the soil moisture content, which varied greatly among the four sites due to differing water table depth.     

Biodegradation of Aqueous Organic Matter over Seasonal Changes: Bioreactor Experiments with Indigenous Lake Water Bacteria

Artificial groundwater recharge for drinking water production involves infiltration of surface water through sandy soil and its capture into a groundwater aquifer. The transformation of aqueous organic matter is one of the central issues in this process. The purpose of this work was to assess the potential of indigenous microorganisms in the source water to contribute in the aqueous organic matter biodegradation. For this purpose, microorganisms were enriched from the source water in a fluidized-bed reactor (FBR) and used for kinetic studies on biodegradation of organic matter at ambient temperature range. Lake water (total organic carbon 5.8?mg?L?1) was continuously fed to the FBR containing porous carrier material to support biomass retention. In the inlet and outlet water there were on average 21±6 and 13±5×105?cells?mL?1, respectively. Biofilm accumulation (as volatile solids) reached 13.1?mg?g?1 dw carrier. In the continuous-flow mode and the batch tests, the highest oxygen consumption rate appeared in the summer, followed by the fall, spring, and winter. At low temperatures, the biodegradation of aqueous organic matter was relatively rapid initially for labile fractions followed by a slower phase for refractory fractions. The average temperature coefficient (Q10) in the system was 2.3 illustrating a strong temperature dependency of oxygen consumption. The isotopic analysis of dissolved inorganic carbon δ13CDIC analysis revealed 27 and 69% mineralizations of dissolved organic carbon at 23 and 6°C over 65 and 630 min, respectively. These results can be used to construct additional input parameters in modeling applications of artificial groundwater recharge process. The biological component especially, i.e., the biodegradation, is difficult to predict for on-site applications without experimental proof and thus the interpretation in this study will help formulate design predictions for the process.     

Bioleaching of Metal-Contaminated Soil in Semicontinuous Reactor

Recently, microbial leaching of heavy metals from contaminated soils with indigenous iron-oxidizing microflora has been successfully applied in flask experiments. However, the long hydraulic residence time (HRT) required and the batch mode are not well suited for an industrial scale process. Therefore, this research focused on bioleaching of Zn, Cu, and Mn from a contaminated soil in the semicontinuous mode. Metal leaching experiments were carried out in an 8 L semicontinuous stirred tank reactor (SCSTR) with a soil concentration of 100 g∕L, as well as in 500 mL shake flasks. It was found that bioleaching in the SCSTR entails a reduction of treatment duration (from 10 to 2 days) and an increase in the solubilization efficiency. Metal solubilization efficiency in the SCSTR was 40% for Zn, 47% for Cu, and 34% for Mn. When the volume of the soil suspension remaining in the SCSTR between transfers was small (20% instead of 50%), corresponding to a shorter HRT (2.5 days instead of 4 days), the solubilization efficiencies were reduced. The volumetric oxygen transfer coefficient and the oxygen uptake rate were calculated in the SCSTR for both HRTs tested. The dissolved oxygen concentration below which the microflora does not grow was found to be 0.2 to 0.3 mg∕L, and the concentration below which oxygen is limiting was 0.8 mg∕L.     

Removal of Lead from Contaminated Water and Clay Soil Using a Biosurfactant

Lead removal from water and contaminated soils was investigated using biosurfactant, anionic, and nonionic surfactants in continuously stirred batch reactors. Lead-contaminated water up to 100?mg/L and clay soil up to 3,000?mg/kg were used in this investigation. The surfactant concentration up to 10 critical micelle concentration was used. The speciation of lead into the micelles was quantified and the lead removal efficiency depended on the level of contamination, surfactant type, and concentration. Of the surfactants used, biosurfactant (produced from used vegetable oil) had the best removal efficiency (75%) at a lead contamination of 100?mg/L in water at pH of over 12. The Fourier-transformed infrared spectroscopy study showed that the carboxyl group in the biosurfactant was effective in removing the lead from the solution. Langmuir and Freundlich relationships were used to represent the micelle partitioning of lead in the surfactant solutions. Desorption of lead from contaminated kaolinite clay was represented using linear isotherms. The biosurfactant solution had a higher micelle partitioning for the lead from contaminated water and desorbing the lead from the contaminated soil compared to the other chemical surfactants.     

Removal of Heavy Metals and COD by SRB in UAFF Reactor

Sulfate-reducing bacteria, under anaerobic conditions, reduce sulfate, SO4?2, to sulfide, S?2, which in turn can effectively precipitate heavy metals. In this research project, sulfate-reducing bacteria were grown in an upflow anaerobic fixed-film (UAFF) reactor using optimum growth conditions obtained in previous studies. These reactors were then fed with different heavy metals at increasing loading rates until complete failure occurred as metal removal reached zero and residual sulfide dropped to zero. The metal concentrations were measured as total, dissolved, and free ions both in the influent and in the effluent streams. The results of this research showed that 100% removal efficiencies could be obtained with individual concentrations up to 200 mg∕L for Cu, 150 mg∕L for Ni and Zn, 75 mg∕L for Cr, 50 mg∕L for Cd, and 40 mg∕L for Pb. Also, the corresponding organic matter removal as total organic carbon was found to be about 50% of the influent total organic carbon. A set of mathematical equations were derived to express the mass balance inside the UAFF reactor, with respect to metal influent concentrations and sulfide production. These equations were corrected by incorporating a correction product, α?β, to represent the toxicity effect of the increasing metal concentrations.     

Nitrification at Low Oxygen Concentration in Biofilm Reactor

A nitrification process under low dissolved oxygen (DO) concentration is proposed in a completely stirred biofilm reactor. The reactor was fed with a synthetic wastewater containing 250 mg NH4–N∕L. A stable nitrite accumulation in the effluent was obtained during >110 days' operation; NO2–N:(NO2–N + NO3–N) in the effluent reached >90% under 0.5 mg DO∕L. Ammonium was completely converted and NH4–N in the outlet was as low as 5 mg∕L. A transient increase of the DO concentration in the reactor induced a complete conversion of ammonia and nitrite to nitrate after only 2 days. A return to a low DO concentration again induced nitrite accumulation. These results show that the nitrite oxidizers were always present in the reactor but were outcompeted at low DO concentration, due to their lower affinity for oxygen, compared with ammonia oxidizers. Nitrite accumulation could also be favored by free nitrous acid accumulation inside the biofilm.     

Biodegradation Kinetics of MTBE in Laboratory Batch and Continuous Flow Reactors

Methyl tert-butyl ether (MTBE) biodegradation was investigated using a continuously stirred tank reactor with biomass retention (porous pot reactor) operated under aerobic conditions. MTBE was fed to the reactor at an influent concentration of 150 mg/L (1.70 mM). An identical reactor was operated as a killed control under the same conditions. Operation of these reactors demonstrated that removal of MTBE was biological and suggests that biomass retention is critical for effective degradation. MTBE removal exceeded 99.99% when the volatile suspended solids concentration in the reactor was above 600 mg/L. Batch experiments conducted using mixed liquor from the porous pot reactor indicated that the individual rates of biodegradation of MTBE and tert-butyl alcohol (TBA) increase with increasing initial concentration. When batch tests were later repeated, the MTBE degradation rates were found to have increased while the TBA degradation rates remained constant. All batch tests confirmed that the degradation rate of TBA governed the overall degradation rate (degradation rate of both MTBE and TBA). The presence of TBA at lower concentrations did not affect the rate of MTBE degradation; however, higher concentrations of TBA did reduce the rate of MTBE biodegradation.     

Competitive Substrate Biodegradation during Surfactant-Enhanced Remediation

The impact of synthetic surfactants on the aqueous phase biodegradation of benzene, toluene, and p-xylene (BTpX) was studied using two anionic surfactants, sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS), and two nonionic surfactants, POE(20) sorbitan monooleate (T-maz-80) and octylphenolpoly(ethyleneoxy) ethanol (CA-620). Batch biodegradation experiments were performed to evaluate surfactant biodegradability using two different microbial cultures. Of the four surfactants used in this study, SDS and T-maz-80 were readily degraded by a microbial consortium obtained from an activated sludge treatment system, whereas only SDS was degraded by a microbial culture that was acclimated to BTpX. Biodegradation kinetic parameters associated with SDS and T-maz-80 degradation by the activated sludge consortium were estimated using respirometric data in conjunction with a nonlinear parameter estimation technique as μmax = 0.93 h?1, Ks = 96.18 mg∕L and μmax = 0.41 h?1, Ks = 31.92 mg∕L, respectively. When both BTpX and surfactant were present in the reactor along with BTpX-acclimated microorganisms, two distinct biodegradation patterns were seen. SDS was preferentially utilized inhibiting hydrocarbon biodegradation, whereas the other three surfactants had no impact on BTpX biodegradation. None of the four surfactants were toxic to the microbial cultures used in this study. Readily biodegradable surfactants are not very effective for subsurface remediation applications as they are rapidly consumed, and also because of their potential inhibitory effects on intrinsic hydrocarbon biodegradation. This greatly increases treatment costs as surfactant recovery and reuse are adversely affected.     

Anoxic∕Oxic Biodegradation of Aminobenzene

Biodegradation of aminobenzene, which is used as the only source of carbon and nitrogen, is evaluated in a single fluidized bed reactor operated in a temporal, anoxic∕oxic mode. The experimental evidence indicates that total organic carbon (TOC) is removed with >91% efficiency at a feed concentration of 100 mg∕L and a dilution rate of 2.4 day?1. Moreover, about 53–63% of feed total Kjeldahl nitrogen (TKN) is also removed, confirming that effective removal of nitrogenous matter in aminobenzene (i.e., the ?NH2 group) is achievable in a temporal, anoxic∕oxic environment. The kinetic analysis shows that TOC removal in oxic cycles is rapid and substantial, which enables nitrification to proceed at a discernible rate. In addition, the data on TOC and NO3?-N removal in anoxic cycles reveal that carbonaceous matter in aminobenzene and∕or its intermediate metabolites is effectively utilized for denitrification. The best treatment performance, in terms of carbon and nitrogen removal and potential savings in aeration costs, is obtained by coupling a 6 h oxic cycle with a 6 h anoxic cycle. All reaction rates estimated in anoxic∕oxic experiments remain relatively constant over the range of conditions tested.     

Pyrolysis-GC∕FID Test for Biogenic Interference in Contaminated Soil

“Biogenic interference” is that portion of natural organic matter in soil that cannot be distinguished from petroleum in a standard test for contamination. Biogenic interference is normally a small fraction of total natural organic matter. In organic soils, however, biogenic interference alone can exceed “petroleum” limits set by regulatory agencies. A test using a pyrolysis-gas chromatograph∕flame ionization detector (GC∕FID) was developed to quantify biogenic interference in soil samples from northern Alaska. The samples had no known history of contamination, so all measured “petroleum” was derived from biogenic interference. The pyrolysis test was found to predict biogenic interference in soil samples more accurately than any combination of standard soil tests, including C:N ratio, pH, percent organic carbon, extractable carbon, humic acids, fulvic acids, low molecular weight acids, hydrophobic neutrals, and hydrophilic neutrals. Analysis of samples contaminated in the laboratory confirmed that the pyrolysis test could quantify biogenic interference in soils recently contaminated by petroleum.     

UASB Treatment of Tapioca Starch Wastewater

Feasibility of the upflow anaerobic sludge blanket (UASB) process was investigated for the treatment of tapioca starch industry wastewater. After removal of suspended solids by simple gravity settling, starch wastewater was used as a feed. Start-up of a 21.5-L reactor with diluted feed of approximately 3,000 mg∕L chemical oxygen demand (COD) was accomplished in about 6 weeks using seed sludge from an anaerobic pond treating tapioca starch wastewater. By the end of the start-up period, gas productivity of 4–5 m3/m3r?day was obtained. Undiluted supernatant wastewater with a COD concentration of 12,000–24,000 mg∕L was fed during steady-state reactor operation at an organic loading rate of 10–16 kg COD/m3r?day. The upflow velocity was maintained at 0.5 m∕h with a recirculation ratio of 4:1. COD conversion efficiencies >95% and gas productivity of 5–8 m3/m3r?day were obtained. These results indicated that removal of starch solids from wastewater by simple gravity settling was sufficient to obtain satisfactory performance of the UASB process.     

Reduced-Runoff Irrigation of Alfalfa in Imperial Valley, California

This paper assesses the potential of the “reduced-runoff” surface irrigation method for clay soils to limit tailwater runoff and evaluate its impacts on crop production and soil salinity throughout a 3-year alfalfa hay production cycle in the Imperial Valley. Despite moderately saline field conditions, tailwater runoff was reduced to <2%, thereby reducing the annual water application by approximately 28% with no loss in hay yield or quality in comparison to countywide averages. The valley average applied-water yield efficiency (yield∕applied water) was increased from 8.9 to 15.2 kg∕ha-mm. When corrected for yield reduction due to salinity conditions (i.e., ～21 kg∕ha-mm), this latter value is comparable to reported maximum alfalfa water-use efficiency (～20 kg∕ha-mm). Soil salinity accumulated (from 6 to 14 dS∕m) at the 0.9–1.5 m depth interval of the soil profile, particularly in the lower 15% of the border checks by the end of the study. However, disking, a single leaching irrigation, and sweet corn production after termination of the alfalfa were adequate to reclaim the soil.     

Volatile Organic Compound (VOC) Transport through Compacted Clay

Movement of volatile organic compounds (VOCs) through compacted clay liners was investigated using laboratory-scale column and tank tests. Hydraulic conductivity of the compacted clay was not significantly impacted by the introduction of VOCs in concentrations up to 20 mg∕L. Soil-water partition coefficients of the seven VOCs tested had a strong logarithmic relationship with the octanol-water partition coefficient. Partition coefficients from batch tests were in good agreement with those measured directly on soil samples at the termination of the column∕tank tests. The VOCs were degraded in the clay, with estimated half-lives ranging from 2 to 116 days. Mechanical dispersion was not significant in the range of the hydraulic conductivities of the test specimens (i.e., <10?7 cm∕s). Effective molecular diffusion coefficients were mostly in 10?6 cm2∕s and generally decreased with increasing aqueous solubility. Mass transport parameters of VOCs in clay liners can be estimated from laboratory batch tests and properly prepared small-scale column tests. However, accounting for degradation of VOCs and minimizing the number of transport parameters that are simultaneously estimated from a single response-time record are important considerations for accurate determination of transport parameters.     

Treatment and Decolorization of Dyes in an Anaerobic Baffled Reactor

Synthetic organic colorants, the majority of which are recalcitrant in nature, are used universally in many different manufacturing processes. The dyes are released into the environment in industrial effluents and are highly visible even at low concentrations (<1 mg∕L). Added to this, certain dyes, dye precursors, and aromatic amines have been shown to be carcinogenic. Thus, appropriate treatment of dye wastewaters to remove color and the dye compounds is clearly an important issue. Methanogenic toxicity tests on several food dyes provided a range of toxicity results, from noninhibitory (IC50 >20 g∕L) to inhibitory (IC50 0.2 mg∕L). Batch biodegradability assays indicated that the dyes were not readily utilized by the anaerobic microorganisms as a sole substrate. Decolorization of the dye tartrazine was investigated in a laboratory-scale anaerobic baffled reactor at a concentration of 250 mg∕L. Reduction in COD of 50–60% and color reduction of about 95% was achieved. Initially the tartrazine was not readily decolorized; however, decolorization improved with acclimation of the biomass. An industrial wastewater from a food dye manufacturer was fed to a second laboratory-scale anaerobic baffled reactor at a concentration of 5% (volume-to-volume ratio) and then increased to 10% (volume-to-volume ratio). Anaerobic degradation of the wastewater was efficient. Methanogenic activity was high; the organic content of the influent was reduced by about 70%, and color was reduced by almost 90%     

Enhancement of Electrokinetic Extraction from Lead-Spiked Soils

An innovative system was developed to enhance electrokinetic extraction of heavy metals from contaminated soils. The system consists of a layer that was continuously flushed with nitric acid at pH 3 near the cathodic region and two reservoirs with 0.4 M NaOAc at pH 3.8 and acetic acid at pH 4 flushing the anode and cathode, respectively. Both pure kaolinite and carbonate-rich illitic soils were tested. With traditional electrokinetic systems, approximately 60% of lead was transported to the cathode for kaolinite, whereas there was little removal for carbonate-rich illitic soil. This result indicates that clay minerals have an important effect on the desorption process. The integrated electrokinetic system maximized contaminant extraction and minimized precipitation in the cathodic region. Over 80% of the lead was removed from carbonate-rich illitic soil, with 5,000-mg∕kg initial lead contaminated concentration, and leached out through the flushing layer. The system operated successfully in laboratory bench tests with carbonate-rich illitic soil.     

The oncofetal J28 epitope involves fucosylated O-linked oligosaccharide structures of the fetoacinar pancreatic protein

The use of an indigenous microbial consortium, pollutant-acclimated and attached to soil particles (activated soil), was studied as a bioaugmentation method for the aerobic biodegradation of pentachlorophenol (PCP) in a contaminated soil. A 125-l completely mixed soil slurry (10% soil) bioreactor was used to produce the activated soil biomass. Results showed that the bioreactor was very effective in producing a PCP-acclimated biomass. Within 30 days, PCP-degrading bacteria increased from 10(5) cfu/g to 10(8) cfu/g soil. Mineralization of the PCP added to the reactor was demonstrated by chloride accumulation in solution. The soil-attached consortium produced in the reactor was inhibited by PCP concentrations exceeding 250 mg/l. This high level of tolerance was attributed to the beneficial effect of the soil particles. Once produced, the activated soil biomass remained active for 5 weeks at 20 degrees C and for up to 3 months when kept at 4 degrees C. The activated attached soil biomass produced in the completely mixed soil slurry bioreactor, as well as a PCP-acclimated flocculent biomass obtained from an air-lift immobilized-soil bioreactor, were used to stimulate the bioremediation of a PCP-impacted sandy soil, which had no indigenous PCP-degrading microorganisms. Bioaugmentation of this soil by the acclimated biomass resulted in a 99% reduction (from 400 mg/kg to 5 mg/kg in 130 days) in PCP concentration. The PCP degradation rates obtained with the activated soil biomass, produced either as a biomass attached to soil particles or as a flocculent biomass, were similar.     

Organic Removal of Anaerobically Treated Leachate by Fenton Coagulation

The leachate from a Hong Kong landfill, containing 15,700 mg∕L of chemical oxygen demand (COD) and 2,260 mg∕L of ammonia nitrogen (NH3–N), was first treated in a UASB (upflow anaerobic sludge blanket) reactor at 37°C. The process on average removed 90.4% of COD with 6.6 days of hydraulic retention at an organic loading rate of 2.37 g of COD∕L?day. The UASB effluent was further treated by the Fenton coagulation process using H2O2 and Fe2+. Under the optimal condition of 200 mg of H2O2∕L and 300 mg of Fe2+∕L and an initial pH of 6.0, 70% of residual COD in the UASB effluent was removed, of which 56% was removed by coagulation∕precipitation and only 14% by free radical oxidation. It is obvious that H2O2 and Fe2+ had a strong synergistic effect on coagulation. The average COD in the final effluent was 447 mg∕L. Removing each gram of COD required 0.28 g of Fe2+ and 0.18 g of H2O2.     

Magnitude and Variability of Biogenic Interference in Cold Regions Soils

In organic soils commonly found in cold regions, many compounds with similar characteristics are found in petroleum contamination and natural organic material (NOM). These similarities make it difficult to distinguish between natural compounds and true contamination using standard test methods. “Biogenic interference” is the term used to describe the NOM quantified as “petroleum” during a standard test for soil contamination. The inability to differentiate between biogenic interference and soil contamination is of concern because it can cause cleanup standards to be set at lower limits than the actual contamination warrants. This paper presents the results from over 200 uncontaminated soil samples that were analyzed to determine the magnitude and variability of biogenic interference in soils from cold regions. Studies were conducted to evaluate the correlation between fundamental physical∕chemical properties of soil and extractable NOM levels. Samples were also collected and analyzed to evaluate spatial (vertical and horizontal) variations in background extractable NOM at one site. A final set of samples was analyzed to determine the range of background extractable NOM levels at uncontaminated sites throughout Alaska. The results show that uncontaminated soil from across Alaska can contain several hundred to several thousand mg∕kg of extractable naturally occurring diesel and residual range organics. A high degree of variability was observed in the amount of extractable NOM at different sites across Alaska and within a single site.