生物净化废气技术的进展

生物技术以其能在常温常压下将污染物降解为无毒无害的简单物质、无二次污染、运行费用低等优点,目前已应用于许多废气处理,并已经形成了一套关于可生化气体的净化原理和工业应用经验的重要体系。文中介绍了生物技术处理污水处理厂、养殖场排放的恶臭气体、工厂排放的硫化物的发展,并分析了解决生物膜堵塞的途径,以及分子生物学在废气生物处理中的应用研究,提出生物净化废气技术的发展方向,期待该技术在国内能得到更广泛的应用。     

生物净化废气技术的进展

生物技术以其能在常温常压下将污染物降解为无毒无害的简单物质、无二次污染、运行费用低等优点,目前已应用于许多废气处理,并已经形成了一套关于可生化气体的净化原理和工业应用经验的重要体系。文中介绍了生物技术处理污水处理厂、养殖场排放的恶臭气体、工厂排放的硫化物的发展,并分析了解决生物膜堵塞的途径,以及分子生物学在废气生物处理中的应用研究,提出生物净化废气技术的发展方向,期待该技术在国内能得到更广泛的应用。     

Biodegradation of solvents in varnish waste water of an airscrubber from an automobile varnish shop

The scrubber liquid of an automobile varnish shop, where varnish particle, pigments and resins are washed out, contains microorganisms, that are able to degrade the main compounds of the solvents in the waste gases, i.e. n-butanol, ethylbenzene and structural isomers of xylene, ethyltoluene and trimethylbenzene. The concentration of the compounds in the varnish waste water to be purified oscillated between 1000 and 1 ppm. The specific degradation efficiency could be increased 4 to 12 times by improvement in oxygen supply.A further enhancement was achieved by continuous addition of organic solvents in the gas phase. During the cultivation the number of different microorganisms of the mixed culture in the scrubber liquid was reduced. The biological system was also very stable and not sensitive to fluctuation in the solvent supply. Differences in the degradation capacity of structural isomers take place at the same concentration of aromatic hydrocarbons. The elimination of 2- or 4-ethyltoluene and 1,3,5- or 1,2,3-trimethylbenzene were 10 to 25% lower than 3-ethyltoluene or 1,2,4-trimethylbenzene.     

Pollution of the Amur River with anthropogenic and natural organic substances

The pollution of the Amur water with organic compounds at the Khabarovsk water-supply point has been analyzed by means of gas chromatography-mass spectrometry (GC-MS). Among environmental pollutants, petroleum hydrocarbons and alkylphtalates predominate. A number of potentially dangerous compounds present in the waste water of the rubber industry works and some other dangerous compounds including a herbicide of TsP 32179 type were detected. Pollution with these compounds has a stable character. The concentrations of a number of critical substances did not exceed the MPCs; however, many compounds are toxic micro-impurities. A great part of the identified compounds are of microbiological origin.     

Design,Construction, and Operation of a Fast Pyrolysis Plant for Biomass

A continuous fluidized‐bed plant (PDU‐scale) for fast pyrolysis of lingnocellulosic biomass gives rise to bio‐oil yields of 65 wt.‐%. The average reactor gas residence time was 1.2 s only. The gas and charcoal yields were 15–20 wt.‐%, respectively. The bio oils were chemically characterized. The main monomeric products of the thermal degradation of carbohydrates are acetic acid, hydroxyacetaldehyde, hydroxypropanone, and levoglucosan. The process described in this paper can also be used for disposal of inorganic‐, metal‐organic‐, and chlorine‐organic contaminated waste‐wood. Inorganic compounds of wood preservatives are concentrated in the charcoal fraction and can be separated easily. Chlorine‐organic wood preservatives are mostly degraded. The process has been positively tested as a technique for disposal, recycling, and exploitation of industrial biomass waste (wood waste, grinding grit, fibre sludge, cocoa shell and modern composites like HPL). Bio oil from fast pyrolysis can be used for the production of energy and chemical feedstock. Research for these purposes is ongoing.     

Degradation of organic contaminants found in organic waste

In recent years, great interest has arisen in recycling of the waste created by modern society. A common way of recycling the organic fraction is amendment on farmland. However, these wastes may contain possible hazardous components in small amounts, which may prevent their use in farming. The objective of our study has been to develop biological methods by which selected organic xenobiotic compounds can be biotransformed by anaerobic or aerobic treatment. Screening tests assessed the capability of various inocula to degrade two phthalates di-n-butylphthalate, and di(2-ethylhexyl)phthalate, five polycyclic aromatic hydrocarbons, linear alkylbenzene sulfonates and three nonylphenol ethoxylates under aerobic and anaerobic conditions. Under aerobic conditions, by selecting the appropriate inoculum most of the selected xenobiotics could be degraded. Aerobic degradation of di(2-ethylhexyl)phthalate was only possible with leachate from a landfill as inoculum. Anaerobic degradation of some of the compounds was also detected. Leachate showed capability of degrading phthalates, and anaerobic sludge showed potential for degrading, polycyclic aromatic hydrocarbons, linear alkylbenzene sulfonates and nonyl phenol ethoxylates. The results are promising as they indicate that a great potential for biological degradation is present, though the inoculum containing the microorganisms capable of transforming the recalcitrant xenobiotics has to be chosen carefully.     

Product specific emissions from municipal solid waste landfills

For the inventory analysis of environmental impacts associated with products in Life Cycle Assessment (LCA) there is a great need for estimates of emissions from waste products disposed at municipal solid waste landfills (product specific emissions). Since product specific emissions can not be calculated or measured directly at the landfills, they must be estimated by modeling of landfill processes. This paper presents a landfill model based on a large number of assumptions and approximations concerning landfill properties, waste product properties and characteristics of various kinds of environmental protection systems (e.g. landfill gas combustion units and leachate treatment units). The model is useful for estimation of emissions from waste products disposed in landfills and it has been made operational in the computer tool LCA-LAND presented in a following paper. In the model, waste products are subdivided into five groups of components: general organic matter (e.g. paper), specific organic compounds (e.g. organic solvents), inert components (e.g. PVC), metals (e.g. cadmium), and inorganic non-metals (e.g. chlorine,) which are considered individually. The assumptions and approximations used in the model are to the extent possible scientifically based, but where scientific information has been missing, qualified estimates have been made to fulfill the aim of a complete tool for estimation of emissions. Due to several rough simplifications and missing links in our present understanding of landfills, the uncertainty associated with the model is relatively high.     

Developments in odour control and waste gas treatment biotechnology: a review

Waste and wastewater treatment processes produce odours, which can cause a nuisance to adjacent populations and contribute significantly to atmospheric pollution. Sulphurous compounds are responsible for acid rain and mist; many organic compounds of industrial origin contribute to airborne public health concerns, as well as environmental problems. Waste gases from industry have traditionally been treated using physicochemical processes, such as scrubbing, adsorption, condensation, and oxidation, however, biological treatment of waste gases has gained support as an effective and economical option in the past few decades. One emergent technique for biological waste gas treatment is the use of existing activated sludge plants as bioscrubbers, thus treating the foul air generated by other process units of the wastewater treatment system on site, with no requirement for additional units or for interruption of wastewater treatment. Limited data are available regarding the performance of activated sludge diffusion of odorous air in spite of numerous positive reports from full-scale applications in North America. This review argues that the information available is insufficient for precise process design and optimization, and simultaneous activated sludge treatment of wastewater and airborne odours could be adopted worldwide.     

The natural chlorine cycle – fitting the scattered pieces

Chlorine is one of the most abundant elements on the surface of the earth. Until recently, it was widely believed that all chlorinated organic compounds were xenobiotic, that chlorine does not participate in biological processes and that it is present in the environment only as chloride. However, over the years, research has revealed that chlorine takes part in a complex biogeochemical cycle, that it is one of the major elements of soil organic matter and that the amount of naturally formed organic chlorine present in the environment can be counted in tons per km(2). Interestingly enough, some of the pieces of the chlorine puzzle have actually been known for decades, but the information has been scattered among a number of different disciplines with little or no exchange of information. The lack of communication appears to be due to the fact that the points of departure in the various fields have not corresponded; a number of paradoxes are actually revealed when the known pieces of the chlorine puzzle are fit together. It appears as if a number of generally agreed statements or tacit understandings have guided perceptions, and that these have obstructed the understanding of the chlorine-cycle as a whole. The present review enlightens four paradoxes that spring up when some persistent tacit understandings are viewed in the light of recent work as well as earlier findings in other areas. The paradoxes illuminated in this paper are that it is generally agreed that: (1) chlorinated organic compounds are xenobiotic even though more than 1,000 naturally produced chlorinated compounds have been identified; (2) only a few, rather specialised, organisms are able to convert chloride to organic chlorine even though it appears as if the ability among organisms to transform chloride to organic chlorine is more the rule than the exception; (3) all chlorinated organic compounds are persistent and toxic even though the vast majority of naturally produced organic chlorine is neither persistent nor toxic; (4) chlorine is mainly found in its ionic form in the environment even though organic chlorine is as abundant or even more abundant than chloride in soil. Furthermore, the contours of the terrestrial chlorine cycle are outlined and put in a concrete form by constructing a rough chlorine budget over a small forested catchment. Finally, possible ecological roles of the turnover of chlorine are discussed.     

Use of soft hydrothermal processing to improve and recycle bedding for laboratory animals

Cage bedding for laboratory rodents can influence animal wellbeing and thus the experimental data. In addition, a large amount of used bedding containing excrement is discharged as medical waste from life science institutes and breeding companies. We developed a ground-breaking system to improve fresh bedding and recycle used bedding by applying a soft hydrothermal process with high-temperature and high-pressure dry steam. The system removes both harmful organic components and aromatic hydrocarbons that can affect animals' metabolism. The purpose of the present study was to evaluate the chemical and physical properties of the improved fresh bedding and the recycled used bedding treated by the system. The results showed that 68-99% of the predominant aromatic hydrocarbons were removed from fresh bedding treated at 0.35 MPa and 140 degrees C for 120 min ('improved bedding'). In addition, 59.4-99.0% of predominant harmful organic compounds derived from excrement were removed from used bedding treated at 0.45 MPa and 150 degrees C for 60 min ('recycled bedding'). The soft hydrothermal treatment increased the number of acidic functional groups on the bedding surface and gave it the high adsorptive efficiency of ammonia gas. Harmful substances such as microorganisms, heavy metals and pesticides decreased below the detection limit. The results clearly showed that the improved and recycled bedding is safer for laboratory rodents and has the potential to ameliorate conditions in primary and secondary enclosures (e.g. cages and animal rooms) used for maintaining laboratory animals. This process may be one of the most advanced techniques in providing an alternative to softwood and other bedding, economizing through the recycling of used bedding and reducing bedding waste from animal facilities.     

Sequential anaerobic/aerobic biodegradation of chloroethenes--aspects of field application

Because of a range of different industrial activities, sites contaminated with chloroethenes are a world-wide problem. Chloroethenes can be biodegraded by reductive dechlorination under anaerobic conditions as well as by oxidation under aerobic conditions. The tendency of chloroethenes to undergo reductive dechlorination decreases with a decreasing number of chlorine substituents, whereas with less chlorine substituents chloroethenes more easily undergo oxidative degradation. There is currently a growing interest in aerobic metabolic degradation of chloroethenes, which demonstrates advantages compared to cometabolic degradation pathways. Sequential anaerobic/aerobic biodegradation can overcome the disadvantages of reductive dechlorination and leads to complete mineralization of the chlorinated pollutants. This approach shows promise for site remediation in natural settings and in engineered systems.     

Effect of substituents on photochemical and biological properties of 13,15-N-cycloimide derivatives of chlorin p6

The effect of electron-accepting substituents in position 3 of the chlorine p6 macrocycle in neutral and carboxyl-containing negatively charged cycloimide derivatives of chlorin p6 (CIC) on the photochemical and biological properties of these photosensitizers was studied. A relationship between the structure and properties of CICs was analyzed on the basis of information on their photoinduced cytotoxicity, efficiency of the generation of reactive oxygen species, photostability, intracellular localization, quantitative parameters of accumulation in cells, and cellular pharmacokinetics. It was shown that these compounds can be used for the development of photosensitizers with intense light absorption at 740 nm, controlled intracellular localization, and a high photodynamic activity toward tumor cells.     

Effect of Substituents on Photochemical and Biological Properties of 13,15-<Emphasis Type="Italic">N</Emphasis>-Cycloimide Derivatives of Chlorin p6

The effect of electron-accepting substituents in position 3 of the chlorine p6 macrocycle in neutral and carboxyl-containing negatively charged cycloimide derivatives of chlorin p6 (CIC) on the photochemical and biological properties of these photosensitizers was studied. The relationship between the structure and properties of CICs was analyzed on the basis of information on their photoinduced cytotoxicity, efficiency of generation of reactive oxygen species, photostability, intracellular localization, quantitative parameters of accumulation in cells, and cellular pharmakinetics. It was shown that these compounds can be used for the development of photosensitizers with intense light absorption at 740 nm, controlled intracellular localization, and a high photodynamic activity toward tumor cells.     

The Life Cycle of Chlorine, Part III

In the two previous articles in this series we reviewed the major processes of chlorine production (Part I) and its intermediate uses and waste products in the production of other chemicals (Part 11). In this article I consider some of the final applications of chlorine (e.g., for water treatment and pulp bleaching) and the uses of the most important chlorinated compounds such as solvents, chlorofluorocarbons, and the plastic polyvinyl chloride in the industrial economy. I summarize known evidence regarding their environmental fates. The special case of persistent long-lived toxic compounds (e.g., pesticides) will be discussed in a subsequent article.     

Determination of aromatic hydrocarbons and their metabolites in human blood and urine

Methods for the biological monitoring of aromatic hydrocarbons and their metabolites in the human blood and urine are reviewed. For the determination of the unchanged aromatic hydrocarbon in blood, gas chromatographic head-space analysis is recommended. The metabolites can be monitored by photometric, thin-layer chromatographic, high-performance liquid chromatographic and gas chromatographic methods. For the assessment of health risks caused by aromatic hydrocarbons, reference values and occupational limit values, expressed as biological tolerance values and biological exposure indices, have to be considered.     

Biodegradation of chlorinated phenolic compounds

Chlorophenolic compounds are generated from a number of industrial manufacturing processes including pulp and paper manufacture. These compounds are found to be toxic and recalcitrant and hence their discharge into the environment must be regulated. Slow and partial degradation of chlorophenols under aerobic and anaerobic natural environment has been observed. Aerobic biodegradation of chlorophenols proceeds through the formation of catechols while under anaerobic conditions, reductive dehalogenation is the preferred metabolic pathway. Number and position of chlorine substituents on the phenolic ring has influence on the rate and extent of biodegradation of chlorophenols. In engineered systems, acclimatization of biomass to chlorophenols markedly enhances the biodegradation ability by reducing the initial lag phase and by countering inhibition. Partial removal of chlorophenols between 40-60% is usually observed in aerobic and anaerobic processes. Removal can be enhanced by a combination of aerobic and anaerobic operations.     

Chlorine in the Netherlands, Part II: Risk Management in Uncertainty for Chlorine

The debate over chlorine in industrialized economies has become extremely polarized in the last decade. Environmental pressure groups are striving for a virtual phaseout of chlorine and chlorinated hydrocarbons (CHCs), because they are convinced that the risks cannot be managed. Industry argues this is not necessary because environmental risks can be controlled, nor is it feasible, because at least 60% of all firms use CHCs, produds made with CHCs, or elemental chlorine. In an attempt to give this discussion a more factual basis, the Dutch minister of environment launched a strategic study on chlorine (see Kleijn et al. I997;Tukker et al. 1995). Using all available knowledge about emissions and contemporary evaluation methods, the study found only a limited number of environmental issues outstanding related to the chlorine chain: however, it also found important uncertainties. This article describes the outstanding uncertainties in more detail. It defines which uncertainties have to be regarded as chlorine-specific and the extent to which additional research can resolve them. For the remaining uncertainties the potential benefts of uncertainty reduction strategies are evaluted, relying mainly on the precautionary principle     

Microbial cleaning of waste gas containing volatile organic compounds in a bioreactor system with a closed gas circuit

The cleaning of the exhaust gases of a bioreactor containing volatile hydrocarbons in a bioreactor system with a closed gas circuit is described. The bioreactor system consisted of three different reactor types: a stirred tank which was filled with hydrocarbon-containing waste water to simulate the exhaust gases of a remediation process; a trickle-bed reactor for aerobic treatment of the exhaust gas from the stirred tank; and a photoreactor containing an algae culture which assimilated CO₂ from the trickle-bed reactor and also produced O₂. With this bioreactor system, it was possible to efficiently remove volatile organic compounds (VOC) from the waste gases. Depending on the type of waste water investigated, elimination rates of 41% to 93% of BTEX (benzene, ethylbenzene, toluene, xylene) and 29% to 53% of VCH (volatile chlorinated hydrocarbons) were obtained. Due to the photosynthesis of the algae in the system's photoreactor, oxygen concentrations between 12% and 18% [v/v], equivalent to about 57% to 83% DOT, were obtained. This concentration permitted the aerobic degradation to be carried out without having to add fresh air. The trickle-bed reactor and the photoreactor worked continuously, whereas the waste water in the stirred bioreactor was replaced in different batches. The accumulation of toxic compounds in the nutrient solutions of the trickle-bed (EC-50 > 30 g/l) and of the photoreactor (EC-50 > 35 g/l) was low. Carbon dioxide concentrations in the gas flow were higher than in fresh air (1% to 3% [vol/vol]), but no long-term accumulation of CO₂ occurred. This means that the algae in the photoreactor were active enough to assimilate the CO₂ which had been produced. They were also able to produce sufficient oxygen for aerobic hydrocarbon degradation. The system described is a first step towards treating waste gases which results from the bioremediation of hydrocarbon-contaminated media in a closed gas circuit without any emission (e.g. VOC, CO₂, germs).     

Biodegradation of a dilute waste oil emulsion applied to soil

Summary The use of land treatment for disposal of a dilute waste oil emulsion generated by an aluminum rolling industry was investigated. Major components of the waste, identified by gas chromatography and mass spectrometry, were linear and branched (C₁₂–C₂₅) and fatty acid emulsifiers (primarily, isomers of oleic acid). Hexadecane and pristane were readily biodegraded in vitro when added to soil collected from the waste disposal site. Hydrocarbons and fatty acids extracted from the waste were similarly, biodegraded, however, the rate of decomposition may have depended on the history of waste applications to soil collected from the land treatment site. The apparent half-life of resolvable waste hydrocarbons and fatty acids was 9.5 days in soil which had received waste applications averaging 25.4l m^–2 wk^–1. In contrast, soil receiving either 50.8l m^–2 wk^–1 or no waste application during summer 1987 apparent exhibited half-lives of 28.1 and 60.3 days, respectively. Waste components were restricted to the upper 48 cm of the soil cores collected from the disposal site. Core samples also provided evidence for biodegradation of hydrocarbons and fatty acids as well as an accumulation of other compounds not readily resolvable by gas chromatographyPublished with the approval of the Director of the West Virginia University Agriculture and Forestry Experiment Station as Scientific Article # 2122.     

Biodegradation of halogenated organic compounds.

In this review we discuss the degradation of chlorinated hydrocarbons by microorganisms, emphasizing the physiological, biochemical, and genetic basis of the biodegradation of aliphatic, aromatic, and polycyclic compounds. Many environmentally important xenobiotics are halogenated, especially chlorinated. These compounds are manufactured and used as pesticides, plasticizers, paint and printing-ink components, adhesives, flame retardants, hydraulic and heat transfer fluids, refrigerants, solvents, additives for cutting oils, and textile auxiliaries. The hazardous chemicals enter the environment through production, commercial application, and waste. As a result of bioaccumulation in the food chain and groundwater contamination, they pose public health problems because many of them are toxic, mutagenic, or carcinogenic. Although synthetic chemicals are usually recalcitrant to biodegradation, microorganisms have evolved an extensive range of enzymes, pathways, and control mechanisms that are responsible for catabolism of a wide variety of such compounds. Thus, such biological degradation can be exploited to alleviate environmental pollution problems. The pathways by which a given compound is degraded are determined by the physical, chemical, and microbiological aspects of a particular environment. By understanding the genetic basis of catabolism of xenobiotics, it is possible to improve the efficacy of naturally occurring microorganisms or construct new microorganisms capable of degrading pollutants in soil and aquatic environments more efficiently. Recently a number of genes whose enzyme products have a broader substrate specificity for the degradation of aromatic compounds have been cloned and attempts have been made to construct gene cassettes or synthetic operons comprising these degradative genes. Such gene cassettes or operons can be transferred into suitable microbial hosts for extending and custom designing the pathways for rapid degradation of recalcitrant compounds. Recent developments in designing recombinant microorganisms and hybrid metabolic pathways are discussed.