工业固体废弃物的急性生物毒性研究

工业固体废弃物的急性生物毒性研究谢思琴,顾宗濂,周德智（中国科学院南京土壤研究所,南京２１０００８）Ａｃｕｔｅｂｉｏｔｏｘｉｃｉｔｙｏｆｉｎｄｕｓｔｒｉａｌｓｏｌｉｄｗａｓｔｅｓ￥．ＸｉｅＳｉｑｉｎ;ＧｕＺｏｎｇｌｉａｎａｎｄＺｈｏｕＤｅｚｈｉ（Ｉｎ...     

Modelling of pyrolysis of coal-biomass blends using thermogravimetric analysis

The primary objective of this work was to develop an appropriate model to explain the co-pyrolysis behaviour of lignite coal-biomass blends with different proportions using a thermogravimetric analyzer. A new parallel-series kinetic model was proposed to predict the pyrolysis behaviour of biomass over the entire pyrolysis regime, while a kinetic model similar to that of Anthony and Howard [Anthony, D.B., Howard, J.B., 1976. Coal devolatilization and hydrogasification. AIChE Journal 22(4), 625-656] was used for pyrolysis of coal. Analysis of mass loss history of blends showed an absence of synergistic effect between coal and biomass. Co-pyrolysis mass-loss profiles of the blends were predicted using the estimated kinetic parameters of coal and biomass. Excellent agreement was found between the predicted and the experimental results.     

Anaerobic digestion of municipal solid wastes: dry thermophilic performance

The purpose of this study was to analyze the performance of two laboratory-scale reactors (5.0L) treating organic fraction of municipal solid waste (OFMSW): source sorted OFMSW (SS_OFMSW) obtained from a university restaurant and mechanically selected municipal fraction (MS_OFMSW) obtained from a Municipal Treatment Plant placed in Cadiz-Spain. Discontinuous reactors operated at thermophilic (55 degrees C) and dry (20% total solid) conditions. Different decomposition patterns were observed: (1) the SS_OFMSW exhibited the classical waste decomposition pattern with a fast start up phase beginning within 0-5 days and 20-30 and a subsequent stabilization phase. The VS removal was 45% with a cumulative biogas of 120L in approx. 60 days; (2) the MS_OFMSW showed a methanogenic pattern throughout the whole experimental period (60 days) and this gave higher levels of organic biodegradation (56%VSr) and biogas production (82L). Both processes were completed and a high level of cumulative methane production was achieved in less than 60 days, proximally 25-30L.     

The assimilation of organic hazardous wastes by municipal solid waste landfills

Summary Co-disposal of 12 compounds representing major organic classes (aromatic hydrocarbons, halogenated hydrocarbons, pesticides, phenols, and phthalate esters) with shredded municipal solid waste was tested using a laboratory-scale column and pilot-scale lysimeter to characterize transport and transformation phenomena including sorption, volatilization and bioassimilation. Leachate and gases emitted from the lysimeters were examined for identifiable products of biotransformation. The results of this investigation provided a mechanistic evaluation of the attenuating and assimilative capacity of municipal solid waste landfills for specific organic compounds. Physical/chemical organic compound characteristics were related to refuse characteristics and composition to predict compound fate. Such knowledge is useful in developíng landfill management and operational strategies consistent with the need for control of pollutant releases.     

Production of lipases by solid state fermentation using vegetable oil-refining wastes

Lipases were produced by a microbial consortium derived from a mixture of wastewater sludges in a medium containing solid industrial wastes rich in fats, under thermophilic conditions (temperature higher than 45 °C for 20 days) in 4.5-L reactors. The lipases were extracted from the solid medium using 100 mM Tris–HCl, pH 8.0 and a cationic surfactant agent (cetyltrimethylammonium chloride). Different doses of surfactant and buffer were tested according to a full factorial experimental design. The extracted lipases were most active at 61–65 °C and at pH 7.7–9. For the solid samples, the lipolytic activity reached up to 120,000 UA/g of dry matter. These values are considerably higher than those previously reported in literature for solid-state fermentation and highlight the possibility to work with the solid wastes as effective biocatalysts.     

Manufacture and prebiotic potential of oligosaccharides derived from industrial solid wastes

The solid waste obtained in malting industries when dehulling barley grains, which was mainly made up of barley husks, spent grains and grain fragments, was subjected to a double hydrothermal processing under selected conditions. The liquor from the second stage (containing xylooligosaccharides, XOS) was refined by membrane and ion exchange processing (with or without a previous endoxylanase treatment to reduce the XOS molecular weight). Three XOS concentrates with different purity and/or molecular weight distribution were fermented in vitro with faecal inocula to assess their prebiotic potential. Succinate, lactate, formiate, acetate, propionate and butyrate were generated in fermentations, confirming the prebiotic potential of the various products assayed. The purity of XOS concentrates did not play a significant role in fermentation, whereas the sample with shorter average degree of polymerization presented a faster fermentation kinetics and led to the highest concentration of lactic acid.     

Pulp and paper mill solid wastes as substrates for single-cell protein production

We have investigated the upgrading of some typical pulp and paper mill solid wastes into protein-enriched animal feed using the cellulolytic fungus Chaetomium cellulolyticum. The waste residues used were six different primary clarifier sludges and a sample of tertiary centricleaner rejects. These were obtained from mills whose modes of operation spanned the range typically in present-day usage: groundwood, sulfite, semichemical, Kraft, and thermomechanical pulping, with and without bleaching. Crude protein production from the solid waste residues is compared to that obtainable from fermentation of untreated or caustic-pretreated sawdusts. Some of these waste residues, especially the Kraft pulp mill rejects, appear to be promising sources of substrate for single-cell protein production. In these preliminary findings, up to 28% dry weight crude protein content of the product has been obtained at specific growth rates of up to 0.12hr^?1 on direct utilization of the wastes.     

An integrated mathematical model for co-composting of agricultural solid wastes with industrial wastewater

An integrated model for the composting process was developed. The structure of the model is such that it can be implemented in any mixture of different substrates, even in the case of co-composting of a solid waste with industrial wastewater. This paper presents a mathematical formulation of the physicochemical and biological principles that govern the composting process. The model of the co-composting ecosystem included mass transfer, heat transfer and biological processes. The biological processes included in the model were hydrolysis of particulate substrates, microbial growth and death. Two microbial populations (bacteria and fungi) were selected using Monod kinetics. Growth limiting functions of inhibitory factors, moisture and dissolved oxygen were added in the Monod kinetics. The bacteria were considered to utilise the easy biodegradable carbon hydrolysis product, fungi the difficult one, while both could degrade the carbon of wastewater. The mass balances of the most important nutrients, nitrogen and phosphorous, were also included in this approach. Model computer simulations provided results that fitted satisfactory the experimental data. Conclusively, the model could be a useful tool for the prediction of the co-composting process performance in the future and could be used to assist in the operation of co-composting plants.     

The fuel properties of pyrolysis liquid derived from urban solid wastes in Bangladesh

Urban solid wastes in the form of scrap tyre, waste plastic and waste paper, were pyrolyzed in an externally heated fixed bed reactor. The condensed liquids were analyzed for their properties as fuels and compared with petroleum-derived products. The properties were physical properties, higher heating value, elemental (CHNOS) analysis and chemical composition using Fourier transform infra-red (FTIR) spectroscopy. The results showed that the pyrolysis of urban solid wastes may be a potential source of liquid hydrocarbon fuel.     

Production of biogas from solid organic wastes through anaerobic digestion: a review

Anaerobic digestion treatments have often been used for biological stabilization of solid wastes. These treatment processes generate biogas which can be used as a renewable energy sources. Recently, anaerobic digestion of solid wastes has attracted more interest because of current environmental problems, most especially those concerned with global warming. Thus, laboratory-scale research on this area has increased significantly. In this review paper, the summary of the most recent research activities covering production of biogas from solid wastes according to its origin via various anaerobic technologies was presented.     

Effect of pulping variables on the characteristics of oil-palm frond-fiber

Caustic pulping of oil-palm frond-fiber strands was conducted following a central composite design using a two-level factorial plan involving three pulping variables (temperature: 160-180 degrees C, time: 1-2 h, alkali charge: 20-30% NaOH). Responses of pulp properties to the process variables were analyzed using a statistical software (DESIGN-EXPERT). The results indicated that frond-fiber strands could be pulped with ease to about 35-45% yield. Statistically, the reaction time was not a significant factor while the influences of the treatment temperature and caustic charge were in general significantly relative to the properties of the resultant pulps.     

Pyrolysis characteristics and kinetics of Arundo donax using thermogravimetric analysis

The increase of the price of fossil means, as well as their programmed disappearing, contributed to increase among appliances based on biomass and energy crops. The thermal behavior of Arundo donax by thermogravimetric analysis was studied under inert atmosphere at heating rates ranging from 5 to 20 °C min⁻¹ from room temperature to 750 °C. Gaseous emissions as CO₂, CO and volatile organic compounds (VOC) were measured and global kinetic parameters were determined during pyrolysis with the study of the influence of the heating rate. The thermal process describes two main phases. The first phase named active zone, characterizes the degradation of hemicellulose and cellulose polymers. It started at low temperature (200 °C) comparatively to wood samples and was finished at 350 °C. The pyrolysis of the lignin polymer occurred during the second phase from 350 to 750 °C, named passive zone. Carbon oxides are emitted during the active zone whereas VOC are mainly formed during the passive zone. Mass losses, mass loss rates and emission factors were strongly affected by the variation of the heating rate in the active zone. It was found that the global pyrolysis of A. donax can be satisfactorily described using global independent reactions model for hemicellulose and cellulose in the active zone. The activation energy for hemicellulose was not affected by a variation of the heating rate with a value close to 110 kJ mol⁻¹ and presented a reaction order close to 0.5. An increase of the heating rate decreased the activation energy of the cellulose. However, a first reaction order was observed for cellulose decomposition. The experimental results and kinetic parameters may provide useful data for the design of pyrolytic processing system using A. donax as feedstock.     

Pyrolytic characteristics of microalgae as renewable energy source determined by thermogravimetric analysis

This paper describes the fibre morphology of switchgrass (Panicum virgatum L.) and its pulping characteristics using sodium hydroxide and a combination of sodium hydroxide and sodium sulphite as the cooking agents. It was found that the fibre length of switchgrass is similar to that of poplar despite its high population of short fibre elements (< 0.2 mm). The switchgrass used in this study had a lignin content comparable to that of poplar, but a particularly high content of extractable materials. The soda pulp from switchgrass showed excellent mechanical properties and showed a great potential as a reinforcement component in newsprint making.     

Influence of transitional states on the microbial ecology of anaerobic digesters treating solid wastes

A better understanding of the microbial ecology of anaerobic processes during transitional states is important to achieve a long-term efficient reactor operation. Five wastes (pig manure, biodiesel residues, ethanol stillage, molasses residues, and fish canning waste) were treated in five anaerobic reactors under the same operational conditions. The influence of the type of substrate and the effect of modifying feeding composition on the microbial community structure was evaluated. The highest biomethanation efficiency was observed in reactors fed with fish canning waste, which also presented the highest active archaeal population and the most diverse microbial communities. Only two Bacteria populations could be directly related to a particular substrate: Ilyobacter with biodiesel residues and Trichococcus with molasses residues. Results showed that the time to achieve steady-state performance after these transitional states was not dependent on the substrate treated. But reactors needed more time to handle the stress conditions derived from the start-up compared to the adaptation to a new feeding. Cluster analyses showed that the type of substrate had a clear influence on the microbiology of the reactors, and that segregation was related to the reactors performance. Finally, we conclude that the previous inoculum history treating solid waste and higher values of active Archaea population are important factors to face a successful change in substrate not entailing stability failure.     

Codigestion of solid wastes: a review of its uses and perspectives including modeling

The last two years have witnessed a dramatic increase in the number of papers published on the subject of codigestion, highlighting the relevance of this topic within anaerobic digestion research. Consequently, it seems appropriate to undertake a review of codigestion practices starting from the late 1970s, when the first papers related to this concept were published, and continuing to the present day, demonstrating the exponential growth in the interest shown in this approach in recent years. Following a general analysis of the situation, state-of-the-art codigestion is described, focusing on the two most important areas as regards publication: codigestion involving sewage sludge and the organic fraction of municipal solid waste (including a review of the secondary advantages for wastewater treatment plant related to biological nutrient removal), and codigestion in the agricultural sector, that is, including agricultural - farm wastes, and energy crops. Within these areas, a large number of oversized digesters appear which can be used to codigest other substrates, resulting in economic and environmental advantages. Although the situation may be changing, there is still a need for good examples on an industrial scale, particularly with regard to wastewater treatment plants, in order to extend this beneficial practice. In the last section, a detailed analysis of papers addressing the important aspect of modelisation is included. This analysis includes the first codigestion models to be developed as well as recent applications of the standardised anaerobic digestion model ADM1 to codigestion. (This review includes studies ranging from laboratory to industrial scale.).     

Production of hydrogen and methane from organic solid wastes by phase-separation of anaerobic process

Phase-separated two-stage anaerobic process was examined and evaluated using artificial organic solid waste in laboratory scale. Acidogenic process, which was combined with subsequent methanogenic process using packed-bed reactor, was operated emphasizing on either hydrogen production, or solublizing efficiency of solid materials. In either effluent from hydrogenogenic, or solublizing operation, maximum allowable OLR achieved at methanogenesis was higher than the single methanogenic process. Hydrogenogenic operation was more suitable to combine methanogenic process than solublizing operation, since retention time of hydrogenogenic operation was much shorter than the solublizing operation, obtaining almost the same levels of overall removal efficiency in both COD and VSS. The combination of hydrogenogenic operation in acidogenic process and methanogenic process produced approximately 442mmoll-reactor(1)days(-1) of methane and 199mmoll-reactor(1)days(-1) of hydrogen at 25h of total retention time indicating 82% of COD removal with 96% of VSS decomposition.     

Evaluation of kinetic parameters of thermal decomposition of native collagen by thermogravimetric analysis

The kinetic parameters associated with the thermal decomposition of native collagen have been obtained by thermogravimetric techniques. In order to achieve this a thermogravimetric analysis was carried out in the temperature range of 25°C to about 1000°C. In this temperature range, it had been found that the differential primary weight loss curve had yielded three distinct peaks for the tendon collagen. The thermal decomposition corresponding to each peak was analyzed to retrieve its kinetic parameters. The peak temperature associated with the first peak decreased as the water content in a sample increased, while that of the second peak was independent of its hydration condition. It is believed that the first and the second peaks are, respectively, results of: (1) dissociation of water from collagen, and (2) of breaking of the collagen molecule itself. The third peak has not been easily identified so far. The activation energy and the order of water decomposition are obtained by various known methods. The results obtained by these different approaches agree reasonably well. The kinetic parameters of second and third peak are also obtained and reported here.