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PubMed2005

Ammonia emissions from the composting of different organic wastes. Dependency on process temperature.

Ammonia emissions were quantified for the laboratory-scale composting of three typical organic wastes with medium nitrogen content: organic fraction of municipal solid wastes, raw sludge and anaerobically digested sludge; and the composting of two wastes with high nitrogen content: animal by-products from slaughterhouses and partially hydrolysed hair from the leather industry. All the wastes were mixed with the proper amount of bulking agent. Ammonia emitted in the composting of the five wastes investigated revealed a strong dependence on temperature, with a distinct pattern found in ammonia emissions for each waste in the thermophilic first stage of composting (exponential increase of ammonia emitted when increasing temperature) than that of the mesophilic final stage (linear increase of ammonia emissions when increasing temperature). As composting needs high temperatures to ensure the sanitisation of compost and ammonia emissions are one of the main environmental impacts associated to composting and responsible for obtaining compost with a low agronomical quality, it is proposed that sanitisation is conducted after the first stage in large-scale composting facilities by a proper temperature control. CAPSULE: Ammonia emission pattern and correlation with process temperature are presented for the composting process of different organic wastes.

Air Pollutants↗

PubMed2005

The use of ozone in the remediation of polycyclic aromatic hydrocarbon contaminated soil.

The potential of using ozone for the removal of phenanthrene from several different soils, both alone and in combination with biodegradation using a microbial inoculant (Pseudomonas alcaligenes PA-10), was examined. The greater the water content of the soil the less effective the ozone treatment, with air-dried soils showing the greatest removal of phenanthrene; while soils with higher levels of clay also reduced the effectiveness of the ozone treatments. However, at least a 50% reduction in phenanthrene levels was achieved in air-dried soil after an ozone treatment of 6 h at 20 ppm, with up to 85% removal of phenanthrene achieved in sandy soils. The biodegradation results indicate that P. alcaligenes PA-10 may be useful as an inoculant for the removal of PAHs from contaminated soils. Under the conditions used in our experiments, however, pre-ozonation did not enhance subsequent biodegradation of phenanthrene in the soils. Similar levels of phenanthrene removal occurred in both non-ozonated and ozonated Cruden Bay soil inoculated with P. alcaligenes PA-10. However, the biodegradation of phenanthrene in ozonated Boyndie soil was much slower. This may be due to the release of toxic products in this soil during ozonation.

Biodegradation, Environmental↗

PubMed2005

Sequential UV-biological degradation of chlorophenols.

The sequential UV-biological degradation of a mixture of 4-chlorophenol (CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP) was first tested with each pollutant supplied at an initial concentration of 50 mg l(-1). Under these conditions, the chlorophenols were photodegraded in the following order of removal rate: PCP>TCP>DCP>CP with only CP and DCP remaining after 40 h of irradiation. The remaining CP (41 mg l(-1)) and DCP (13 mg l(-1)) were then completely removed by biological treatment with an activated sludge mixed culture. Biodegradation did not occur in similar tests conducted with a non-irradiated mixture due to the high microbial toxicity of the solution. UV treatment lead to a significant reduction of the phytotoxicity to Lipedium sativum but no further reduction of phytotoxicity was observed after biological treatment. Evidence was found that the pollutants were partially photodegraded into toxic and non-biodegradable products. When the pollutants were tested individually (initial concentration of 50 mg l(-1)), PCP, TCP, DCP, 4-CP were photodegraded according to first order kinetic model (r2>99) with half-lives of 2.2, 3.3, 5.7, and 54 h, respectively. The photoproducts were subsequently biodegraded. This study illustrates the potential of UV as pre-treatment for biological treatment in order to remove toxicity and enhance the biodegradability of organic contaminants. However, it also shows that UV treatment must be carefully optimized to avoid the formation of toxic and/or recalcitrant photoproducts and results from studies conducted on single contaminants cannot be extrapolated to mixtures.

Biodegradation, Environmental↗

PubMed2005

Modeling lead bioavailability and bioaccumulation by Lumbriculus variegatus using artificial particles. Potential use in chemical remediation processes.

Artificial particles, specifically a diverse selection of chromatographical resins, have been recommended and used as a useful experimental model to predict the bioavailability and bioaccumulation of sediment-bound organic chemicals. In this work the same experimental model was adopted to investigate the bioavailability and bioaccumulation of lead by the freshwater oligochaete Lumbriculus variegatus. Particle-water partition coefficients were also determined. Sand particles and the anionic exchange resin promoted a similar uptake and bioaccumulation of lead. Instead, in the presence of the cationic exchanger the metal was not detected in the animals. For neutral particles, the uptake and accumulation depended on the chemistry of the functional groups at the active sites. In addition, a significant negative correlation was found between bioaccumulation and the particle-water partition coefficients. These studies may help to develop alternative methods for chemical remediation of lead-contaminated aquatic systems.

Adsorption↗

PubMed2005

Estimation and projection of nitrous oxide (N2O) emissions from anthropogenic sources in Taiwan.

Taiwan is a densely populated and developed country with more than 97% of energy consumption supplied by imported fuels. Greenhouse gas emissions are thus becoming significant environmental issues in the country. Using the Intergovernmental Panel on Climate Change (IPCC) recommended methodologies, anthropogenic emissions of nitrous oxide (N2O) in Taiwan during 2000-2003 were estimated to be around 41 thousand metric tons annually. About 87% of N2O emissions come from agriculture, 7% from the energy sector, 3% from industrial processes sector, 3% from waste sector. On the basis of N2O emissions in 2000, projections for the year 2010 show that emissions were estimated to decline by about 6% mainly due to agricultural changes in response to the entry of WTO in 2002. In contrast to projections for the year 2020, N2O emissions were projected to grow by about 17%. This is based on the reasonable scenario that a new adipic acid/nitric acid plant will be probably started after 2010.

Agriculture↗

PubMed2005

Effects of combustion and operating conditions on PCDD/PCDF emissions from power boilers burning salt-laden wood waste.

This paper discusses the effects of combustion conditions on PCDD/PCDF emissions from pulp and paper power boilers burning salt-laden wood waste. We found no correlation between PCDD/PCDF emissions and carbon monoxide emissions. A good correlation was, however, observed between PCDD/PCDF emissions and the concentration of stack polynuclear aromatic hydrocarbons (PAHs) in the absence of TDF addition. Thus, poor combustion conditions responsible for the formation of products of incomplete combustion (PICs), such as PAHs and PCDD/PCDF precursors, increase PCDD/PCDF emissions. PAH concentrations increased with higher boiler load and/or low oxygen concentrations at the boiler exit, probably because of lower available residence times and insufficient excess air. Our findings are consistent with the current understanding that high ash carbon content generally favours heterogeneous reactions leading to either de novo synthesis of PCDD/PCDFs or their direct formation from precursors. We also found that, in grate-fired boilers, a linear increase in the grate/lower furnace temperature produces an exponential decrease in PCDD/PCDF emissions. Although the extent of this effect appears to be mill-specific, particularly at low temperatures, the results indicate that increasing the combustion temperature may decrease PCDD/PCDF emissions. It must be noted, however, that there are other variables, such as elevated ESP and stack temperatures, a high hog salt content, the presence of large amounts of PICs and a high Cl/S ratio, which contribute to higher PCDD/PCDFs emissions. Therefore, higher combustion temperatures, by themselves, will not necessarily result in low PCDD/PCDFs emissions.

Air Pollutants↗

PubMed2005

Combined effect of microwave and activated carbon on the remediation of polychlorinated biphenyl-contaminated soil.

The application of microwave and activated carbon for the treatment of polychlorinated biphenyl (PCB) contaminated soil was explored in this study with a model compound of 2,4,5-trichlorobiphenyl (PCB29). PCB-contaminated soil was treated in a quartz reactor by microwave irradiation at 2450MHz with the addition of granular activated carbon (GAC). In this procedure, GAC acted as microwave absorbent for reaching high temperature and reductant for dechlorination. A sheltered type-K thermocouple was applied to record the temperature rising courses. It was shown that the addition of GAC could effectively promote the temperature rising courses. The determination of PCB residues in soil by gas chromatography (GC) revealed that rates of PCB removal were highly dependent on microwave power, soil moisture content, and the amount of GAC added. GC with mass spectrum (MS) detector and ion chromatography were employed for the analysis of degradation intermediates and chlorine ions, respectively. It was suggested that microwave irradiation with the assistance of activated carbon might be a potential technology for the remediation of PCB-contaminated soil.

Carbon↗

PubMed2005

Heap leaching of Pb and Zn contaminated soil using ozone/UV treatment of EDTA extractants.

The feasibility of a novel EDTA-based soil heap leaching method with treatment and reuse of extractants in a closed process loop was evaluated on a laboratory scale. Ozone and UV irradiation were used for oxidative decomposition of EDTA-metal complexes in extractants from Pb (1243 mg kg(-1)) and Zn (1190 mg kg(-1)) contaminated soil. Released metals were absorbed in a commercial metal absorbent Slovakite. Six-consecutive additions of 2.5 mmol kg(-1) EDTA (total 15 mmol kg(-1) EDTA) removed 49.6 +/- 0.6% and 19.7 +/- 1.7% of initial total Pb and Zn from soil (4.6 kg) packed in 22 cm high columns. The efficiency of extraction was similar to small-scale simulations of heap leaching (15 0 g of soil), where EDTA used in the same manner removed 49.7 +/- 1.0% and 13.7 +/- 0.4% of Pb and Zn. The new heap leaching method produced discharge extractant with fairly low final concentrations of Pb, Zn and EDTA (1.98 +/- 2.17 mg l(-1), 4.55 +/- 2.36 mg l(-1), and 0.05 +/- 0.04 mM, respectively), which could presumably be reduced even further with continuation of treatment. The results of our study indicate that for soils contaminated primarily with Pb, treating the EDTA extractants with ozone/UV and reuse of extractants enables efficient soil heap leaching with very little or no wastewater generation, easy control over emissions, and lowers the requirements for process water.

Calcium↗

PubMed2005

Combined chemical and biological treatment of oil contaminated soil.

Combined chemical (Fenton-like and ozonation) and biological treatment for the remediation of shale oil and transformer oil contaminated soil has been under study. Chemical treatment of shale oil and transformer oil adsorbed in peat resulted in lower contaminants' removal and required higher addition of chemicals than chemical treatment of contaminants in sand matrix. The acidic pH (3.0) conditions favoured Fenton-like oxidation of oil in soil. Nevertheless, it was concluded that remediation of contaminated soil using in situ Fenton-like treatment will be more feasible at natural soil pH. Both investigated chemical processes (Fenton-like and ozonation) allowed improving the subsequent biodegradability of oil. Moderate doses of chemical oxidants (hydrogen peroxide, ozone) should be applied in combination of chemical treatment (both, Fenton-like or ozonation) and biotreatment. For remediation of transformer oil and shale oil contaminated soil Fenton-like pre-treatment followed by biodegradation was found to be the most efficient.

Biodegradation, Environmental↗

PubMed2005

Enhanced phytoextraction of Pb and other metals from artificially contaminated soils through the combined application of EDTA and EDDS.

Chemically enhanced phytoextraction is achieved by the application of chelates to soils. Using pot experiments, the effect of the combined application of EDTA and EDDS on the uptake of Cu, Pb, Zn and Cd by Zea mays L. was studied. Among the tested application ratios of 1:1, 1:2, and 2:1 (EDTA/EDDS), 2:1 of EDTA:EDDS was the most efficient ratio for increasing the concentrations of Cu, Pb, Zn and Cd in the shoots. The combined application of 3.33 mmol kg(-1) soil of EDTA+1.67 mmol kg(-1) soil of EDDS produced 650 mg kg(-1) of Pb in the shoots, which was 2.4 and 5.9 times the concentration of Pb in the shoots treated with 5 mmol kg(-1) of EDTA and EDDS alone, respectively. The total phytoextraction of Pb reached 1710 microg kg(-1) soil, which was 2.1 and 6.1 times the total Pb from 5 mmol kg(-1) EDTA and EDDS alone, respectively. The combined application of EDTA and EDDS also significantly increased the translocation of Pb from the roots to the shoots. The mechanism of enhancing the phytoextraction of Pb by the combined application of EDTA+EDDS did not involve a change in the pH of the soil. The increase in the phytoextraction of Pb by the shoots of Z. mays L. was more pronounced than the increase of Pb in the soil solution with the combined application of EDTA and EDDS. It was thought that the major role of EDDS might be to increase the uptake and translocation of Pb from the roots to the shoots of plants.

Biodegradation, Environmental↗

PubMed2005

Effect of soil chemical properties on the remediation of phenanthrene-contaminated soil by electrokinetic-Fenton process.

The electrokinetic-Fenton (EK-Fenton) remediation of soil contaminated with phenanthrene was studied. Two different soils were chosen to investigate the effects of chemical properties, such as Fe oxide contents and acid soil buffer capacity. The H(2)O(2) concentrations in pore water, the electrical potential distributions and the electrical currents were monitored to assess the electrochemical effect in relation to the soil properties. Hadong caly had high acid buffer capacity, and thus the amount of electroosmotic flow was lager in the experiment with Hadong clay than with EPK kaolin. The major mechanism of phenanthrene removal was a degradation in the experiment with EPK Kaolin, while it was a simple transport away from the system in experiment with Hadong clay. It was mainly because of the lower acid buffering capacity and better H(2)O(2) stability in case with EPK Kaolin than with Hadong clay.

Aluminum Silicates↗

PubMed2005

Washing as a remediation technology applicable in soils heavily polluted by mining-metallurgical activities.

A permanent solution in order to remediate a heavily contaminated soil is washing it utilizing the appropriate reagents. The study presented in this paper deals with the washing of a soil highly polluted by mining and metallurgical activities. Pollution consists of slags, sulphur compound waste and various low grade lead condensates, all rich in heavy metals and metalloids (Pb, As, Cu, Zn, Mn and Fe). Soil was washed with deionized water, 6, 3, 2 and 1 M HCl, 6 M H(2)SO(4), 6 M HNO(3) and 0.1 M Na(2)EDTA. High extraction efficiency was achieved with respect to hydrochloric acid even at the lowest concentration; the solubility of pollutants in nitric acid was low, while sulphuric acid was proven to be problematic with respect to lead. Mobilization of metals and metalloids under DI water effect was minimal indicating that the elements fraction that is weakly bound to soil particles is insignificant. Furthermore, a kinetic study was undertaken, utilizing 1 M HCl and 0.1 M Na(2)EDTA. Results illustrated that 1 M HCl was more effective for intermediate mixing times (up to 4 h) while 0.1 M Na(2)EDTA was better applicable to short mixing times (<1 h) and low pH values (pH < 7.1). 1 M HCl was proven to be very effective for the removal of pollutants from contaminated soil but the high metal content of the resulting solution necessitates further treatment for the retention of metals.

Chelating Agents↗

PubMed2006

Effect of calcite on Pb-doped solidified waste forms in leaching.

The alkalinity of cementitious materials rectifies a low pH of leachant to be over 12 in leaching. The rapid change of leachant pH produces the remarked variation of solubility of heavy metals in the toxicity characteristic leaching procedure. The release of lead on cementitious solid waste forms in leaching was observed in the pH range of particularly 12. The release of lead is significant dependant on the changed values of leachant pH. The pH static leaching procedure (PSLP) was implemented for assessing a quantitative measurement of total potential leachability with the continuing addition of acidic leachant up to the point of no change of leachant pH. The release of lead on Pb-doped solidified waste forms (SWF), in the PSLP, was 27.0% of initial concentration at the maximum meq CH3COOH (about 24.0) added to g dry solidified wastes. In this study, the immobilization effect of calcite on SWF was investigated in the acidic condition by the PSLP. Calcite additions to SWF make a good fixation efficiency of about 92%. Calcite addition abundantly provides the acid neutralization capacity to protect SWF from the attack of acid, with the marked development of hydrated minerals (mainly portlandite and C-S-H) in accordance with the accelerating effect of cement hydration.

Calcium↗

PubMed2005

Removal of a cationic dye from aqueous solutions by adsorption onto bentonite clay.

The ability of bentonite to remove malachite green from aqueous solutions has been studied for different adsorbate concentrations by varying the amount of adsorbent, temperature, pH and shaking time. Maximum adsorption of the dye, i.e. >90% has been achieved in aqueous solutions using 0.05 g of bentonite at a pH of 9. Thermodynamic parameters such as DeltaH degrees, DeltaS degrees and DeltaG degrees were calculated from the slope and intercept of the linear plots of lnK(D) against 1/T. Analysis of adsorption results obtained at 298, 308, 318 and 328 K showed that the adsorption pattern on bentonite seems to follow the Langmuir, Freundlih and D-R isotherms. The temperature increase reduces adsorption capacity by bentonite, due to the enhancement of the desorption step in the mechanism. The numerical values of sorption free energy (E(a)) of 1.00-1.12 kJ mol(-1) indicated physical adsorption. The kinetic data indicated an intraparticle diffusion process with sorption being first order. The rate constant k was 0.526 min(-1). The concentration of malachite green oxalate was measured before and after adsorption by using UV-Vis spectrophotometer.

Adsorption↗

PubMed2006

Photocatalytic degradation of mixed gaseous carbonyl compounds at low level on adsorptive TiO2/SiO2 photocatalyst using a fluidized bed reactor.

An adsorptive silica-supported titania photocatalyst TiO(2)/SiO(2) was prepared by using nanosized titania (anatase) immobilized on silica gel by the sol-gel technique with the titanium tetra isopropoxide as the main raw material and acetic acid as the acid catalyst. Meanwhile the structure and properties of the TiO(2)/SiO(2) photocatalyst were studied by means of many modern analysis techniques such as TEM, XRD, and BET. Gas-solid heterogeneous photocatalytic decomposition of four carbonyl compounds mixture at low concentration levels over ultraviolet irradiated TiO(2)/SiO(2) photocatalyst were carried out with high degradation efficiencies in a coaxial triple-cylinder-type fluidized bed photocatalytic reactor, which provided efficient continuous contact of ultraviolet photons, silica-supported titania photocatalyst, and gaseous reactants. Experimental results showed that the photocatalyst had a high adsorption performance and a good photocatalytic activity for four carbonyl compounds mixture. Some factors influencing the photocatalytic decomposition of the mixed carbonyl compounds, i.e. the gas flowrate, relative humidity, concentration of oxygen, and illumination time, were discussed in detail. It is found that the photocatalytic reaction rate of four carbonyl compounds decreased in this order: propionaldehyde, acetone, acetaldehyde and formaldehyde.

Adsorption↗

PubMed2006

Sorption kinetics and leachability of heavy metal from the contaminated soil amended with immobilizing agent (humus soil and hydroxyapatite).

Release of heavy metals onto the soil as a result of agricultural and industrial activities may pose a serious threat to the environment. This study investigated the kinetics of sorption of heavy metals on the non-humus soil amended with (1:3) humus soil and 1% hydroxyapatite used for in situ immobilization and leachability of heavy metals from these soils. For this, a batch equilibrium experiment was performed to evaluate metal sorption in the presence of 0.05 M KNO(3) background electrolyte solutions. The Langmuir isotherms applied for sorption studies showed that the amount of metal sorbed on the amended soil decreased in the order of Pb(2+)>Zn(2+)>Cd(2+). The data suggested the possibility of immobilization of Pb due to sorption process and immobilization of Zn and Cd by other processes like co-precipitation and ion exchange. The sorption kinetics data showed the pseudo-second-order reaction kinetics rather than pseudo-first-order kinetics. Leachability study was performed at various pHs (ranging from 3 to 10). Leachability rate was slowest for the Pb(2+) followed by Zn(2+) and Cd(2+). Out of the metal adsorbed on the soil only 6.1-21.6% of Pb, 7.3-39% of Zn and 9.3-44.3% of Cd leached out from the amended soil.

Acetic Acid↗

PubMed2006

Oxidative and energetic efficiency of different electrochemical oxidation processes for chloroanilines abatement in aqueous medium.

The oxidative efficiency and energy consumption, in the degradation of chloroanilines by anodic oxidation, indirect oxidation with electrogenerated hydrogen peroxide and electro-Fenton have been compared, using a laboratory system driven by a LabVIEW virtual controller. Solutions were oxidized in an undivided cell, where H(2)O(2) was generated electrochemically by reduction of atmospheric oxygen bubbled at a carbon cloth cathode. The electro-Fenton process showed the best degradation power, in terms of efficiency of removal and energy consumption. This process was applied to the purification of a solution obtained by washing a polluted soil. Under laboratory conditions, electro-Fenton removed 75% COD of this wastewater with a specific energy consumption of 0.3kWh per gram of COD, corresponding to 41.8kWhm(-3).

Aniline Compounds↗

PubMed2006

Leaching behavior of Cr(III) in stabilized/solidified soil.

The leaching behavior of chromium was studied using batch leaching tests, surface complexation modeling and X-ray absorption near edge structure (XANES) spectroscopy. A contaminated soil sample containing 1330 mg-Cr kg(-1) and 25600 mg-Fe kg(-1) of dry soil was stabilized/solidified (S/S) with 10% cement, 25% cement, 10% lime and a mixture of 20% flyash and 5% lime. The XANES analysis showed that Cr(III) was the only Cr species in untreated soil and S/S-treated samples. The leachate Cr concentration determined using the toxicity characteristic leaching procedure (TCLP) was reduced from 5.18 mg l(-1) for untreated soil to 0.84 mg l(-1) for the sample treated with 25% cement. The Cr leachability in untreated and treated soil samples decreased dramatically as the pH increased from 3 to 5, remained at similar levels in the pH range between 5 and 10.5, and further decreased at pH>10.5. Modeling results indicated that the release of Cr(III) was controlled by adsorption on iron oxides at pH<10.5, and by precipitation of Ca(2)Cr(2)O(5).6H(2)O at pH>10.5.

Adsorption↗