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ABSTRACT: Ultrasonic generating trough was applied to study the impact of ultrasonic on conditioning of sewage sludge. There are few ultrasonic generators for sludge treatment specifically, so we designed a double-frequency ultrasonic generating trough which could adjust frequency, energy density and treating time flexibly. In the research characteristics of sewage sludge treated by single-frequency and double-frequency ultrasonic were compared. According to the results, the digestion biogas of the sewage sludge treated by ultrasonic increase obviously, and the digestion biogas increment of the sewage sludge treated by single-frequency is 40.93%, higher than that treated by double-frequency. But the SCOD of the sewage sludge treated by double-frequency is 23.5%, more than that treated by single-frequency.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 11/2008; 29(10):2815-9.
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ABSTRACT: The sequestration of CO2 and carbonation process for the stabilization of fresh fly ash from municipal solid waste (MSW) incinerator were investigated. The purpose of this paper is to evaluate the influence of fundamental parameters affecting the stabilization of heavy metal of Pb and diffusivity and reactivity of CO2 (i. e. the water content and concentration of CO2). In addition, the major physical and chemical changes in fly ash after carbonation were investigated using XRD and SEM. It shows that 10% or more water content added to fly ash could remarkably accelerate the sequestration of CO2, compared with control samples without water. The sequestration of CO2 is not remarkable within 1 day in the air atmosphere for low content of CO2 (0.03%). The XRD analysis indicates that CO2 could combine Ca(OH)2 to form CaCO3 and CO2 could also combine heavy metal oxides to form heavy metal carbonate (i.e. from PbO4 to PbCO3). Aggregates of crystals of sheet and cylinder can be observed by SEM.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 08/2007; 28(7):1644-8.
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ABSTRACT: Basic properties of fly ash samples from different urban waste combustion facilities in China were analyzed using as X-ray fluorescence (XRF), scanning electron microscopy (SEM), X-ray diffraction (XRD). The leaching toxicity procedure and some factors influencing heavy metals distribution in fly ash were further investigated. Experimental results indicate that the fly ash structures are complex and its properties are variable. The results of XRF and SEM revealed that the major elements (>10000 mg/kg, listed in decreasing order of abundance) in fly ash are O, Ca, Cl, Si, S, K, Na, Al, Fe and Zn. These elements account for 93% to 97%, and the content of Cl ranges from 6.93% to 29.18 %, while that of SiO2 does from 4.48% to 24.84%. The minor elements (1000 to 10000 mg/kg) include Cr, Cu and Pb. Primary heavy metals in fly ash include Zn, Pb, Cr, Cu etc. According to standard leaching test, heavy metal leaching levels vary from 0 to 163.10 mg/L (Pb) and from 0.049 to 164.90 mg/L (Zn), mostly exceeding the Chinese Identification Standard for hazardous wastes. Morphology of fly ash is irregular, with both amorphous structures and polycrystalline aggregates. Further research showed that heavy metals were volatilized at a high furnace temperature, condensed when cooling down during the post-furnace system and captured at air pollution control systems. Generally, heavy metals are mainly present in the forms of aerosol particulates or tiny particulates enriched on surfaces of fly ash particles. The properties of fly ash are greatly influenced by the treatment capacities of incinerators or the variation of waste retention time in chamber. Fly ash from combustors of larger capacities generally has higher contents of volatile component and higher leaching toxicity, while those of smaller capacities often produce fly ash containing higher levels of nonvolatile components and has lower toxicity. The content of heavy metals and leaching toxicity maybe have no convincing correlation, and high alkali content of CaO greatly contribute to leaching toxicity of heavy metal and acid neutralization capacity against acid rain.
Journal of Environmental Sciences 01/2007; 19(4):458-63. · 1.66 Impact Factor
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ABSTRACT: Leaching characteristics of heavy metals during cement stabilization of fly ash from municipal solid waste incinerator was investigated. We investigated stabilization of heavy metal, such as Cd, Pb, Cu and Zn in fly ash from municipal solid waste incinerator, through the national standard method, with the factors as follows: addition quantity of cement and Na2S, curing time, and pH of leaching liquor. The results show that the more addition the less of heavy metal leached, except Pb which is sensitive to pH of the leachate, and the worse effect of Cd. Cement/fly ash= 10 % is the most appropriate parameter according to national standard method. The hydratation of cement finished basically and stabilization of heavy metal doesn' t vary after curing for 1 day. The mixtures of cement and fly ash have excellent adaptability to environmental pH; the pH of leachate maintain at 7 steadily when pH of leaching liquor varied from 3 to 11.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 01/2007; 27(12):2564-9.
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ABSTRACT: Fundamental properties and the factors that influence the distribution of heavy metals of several fly ashes are analyzed. Experiments indicate that the structures are complex and the properties are changeable. The study results show that the chemical composition is Cl, Ca, K, Na, Si, Al, O, etc, and heavy metals are Zn, Pb, Cr, Cu etc. The main structures of fly ash are irregularly amorphous forms and polycrystalline aggregates. Generally, the ieaching toxicity exceeds the identification standard for hazardous wastes. Heavy metals are chiefly in the forms of tiny aerosol particles and aggregates on the surface of fly ash. The properties of fly ash are greatly influenced by the change of incinerators or the variation of incinerating time. The content of Cl ranges from 6.93% to 29.18%, while that of SiO2 does from 4.48% to 24.84%. The leaching toxicity varies between 0 and 163.10 mg x L(-1) (Pb) and between 0.049 and 164.90 mg x L(-1) (Zn).
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 12/2006; 27(11):2283-7.
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ABSTRACT: Toxicity leaching characteristics and chemical compositions of sample flyash collected from municipal solid waste incinerator was analyzed, it was clear that different heavy metals were contained in flyash and the heavy metal leaching concentration for Pb, Zn, Cd was 11.8, 164.9 and 31.2 mg/L respectively which was much higher than that in Hazardous Waste Toxicity Leaching Standards. A new kind of inorganic chemical agent apatite was chosen to treat with this kind of incineration flyash, the results indicate that the heavy metals (not including Cd in some samples) in the treated flyash using apatite at dosage 7% can reach the landfilling standards for hazardous waste, and the treated flyash can have better stabilization when the size of apatite was 74 microm, and the heavy metal leaching concentration of the treated flyash keep stable at a curing time of 1 day, and it can keep stabilization with a broader pH value of 3 to 11. Thus the risk of secondary pollution for the treated flyash was reduced dramatically when the environment conditions change.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 02/2006; 27(1):189-92.
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ABSTRACT: The physico-chemical characteristics of municipal solid waste incineration fly ashes was analyzed. It indicated that the main elements of fly ashes are Ca, Cl, K, S and Si, and many heavy metals such as Pb, Zn, Cu, Mn and Cr can be found in fly ashes, and the heavy metal leaching toxicity such as Pb, Cu, Zn and Cd is much higher than the standards. A new kind of stabilization agent-soluble phosphate is chosen to treat with fly ash, different influence factors including agent dosage, curing time and pH are taken into consideration to test its stabilization for the stabilized fly ash. The experimental results indicate that fly ash treated with soluble phosphate can have excellent stabilization effect, and the leaching toxicity for Pb, Cd and Zn can be reduced by 97.5%, 91.6% and 95.5% at a phosphate dosage of 3%; curing time can not influence its stabilization; and, stabilized fly ash using soluble phosphate can keep long-term stabilization at a broad pH value.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 08/2005; 26(4):191-4.
