A study of the dental solid waste produced in a school of dentistry in Turkey

Dental wastes are regulated under medical waste control regulations in most countries. Even though the quantity of hazardous wastes in dental solid wastes is a small proportion, there is still cross infection risk and potential danger for environment associated with mismanaged wastes. For this reason, knowledge of waste composition and development of proper management alternatives are necessary. In this study, the composition of solid wastes coming from eight clinics of the dental school of a University hospital in Turkey is examined. Although the waste has some variations between the two samplings, the general picture is such that the major components remain pretty much the same (in terms of %) for a fixed clinic. The composition of waste changes from one clinic to the other as expected. However, one can deduce from the data obtained that at about 35%, rubber gloves constitute close to the half of the total solid waste in almost all the clinics. Other major component is paper forming approximately 30% of the solid waste. In general, total waste coming from the clinics is related with the number of procedures conducted on patients at the clinics. Only a small fraction of the waste is hazardous indicating that at Hacettepe University School of Dentistry, hazardous waste collection rules are obeyed in most of the times.     

Door-to-door measurement of household waste arisings in selected towns in Malaysia

To establish the per capita household waste arisings, door-to-door measurement of discharged waste was carried out. Survey was done in four 2-week phases over a period of 13 months. A questionnaire survey was also carried out to obtain data on household size and other household characteristics as well as the extent of reduce and recycle activities. The results showed that there is a big variance among households on waste arisings, and that household size is an important socio-economic factor in determining per capita waste generation.     

Management of hazardous medical waste in Croatia

This article provides a review of hazardous medical waste production and its management in Croatia. Even though Croatian regulations define all steps in the waste management chain, implementation of those steps is one of the country's greatest issues. Improper practice is evident from the point of waste production to final disposal. The biggest producers of hazardous medical waste are hospitals that do not implement existing legislation, due to the lack of education and funds. Information on quantities, type and flow of medical waste are inadequate, as is sanitary control. We propose an integrated approach to medical waste management based on a hierarchical structure from the point of generation to its disposal. Priority is given to the reduction of the amounts and potential for harm. Where this is not possible, management includes reduction by sorting and separating, pretreatment on site, safe transportation, final treatment and sanitary disposal. Preferred methods should be the least harmful for human health and the environment. Integrated medical waste management could greatly reduce quantities and consequently financial strains. Landfilling is the predominant route of disposal in Croatia, although the authors believe that incineration is the most appropriate method. In a country such as Croatia, a number of small incinerators would be the most economical solution.     

Use of fluff in a coking coal blend in a pilot scale

Journal of Material Cycles and Waste Management - Fluff is a shredder waste made up mostly of polymeric material generated in semi-integrated steel manufacturing plants, which is usually disposed...     

Uncertainty in Estimation of Wet Deposition of Sulphur

A model is described for predicting wet deposition ofsulphur in Britain from rainfall and site measurementsof ion concentration in precipitation. This modelincludes orographic enhancement of both rainfall andion concentration. The model output is comparedagainst available measurement data. Sensitivity anduncertainty analyses are used to predict the outputuncertainty. If the stated assumptions can be shown tobe correct, the wet deposition for Britain at the 5 kmscale is accurate to ±35% across the country. Theanalyses show a larger uncertainty in central Englandand a possible bias towards underestimation of wetdeposition, the latter being of importance incalculating critical load exceedances in remote areas.     

Thermal degradation of PMMA in fluidised beds

In recent years, the production and consumption of plastics have increased significantly and wastes are commonly incinerated or dumped in a landfill. Plastics pyrolysis, on the other hand, may provide an alternative means for disposal of plastic wastes with recovery of valuable gasoline-range hydrocarbons or the monomer. Pyrolysis of polymethyl methacrylate (PMMA) may result in very high recycling rates (90-98%) of the monomer methylmethacrylate (MMA) since the cracking of MMA to lighter molecules (CO2, CO and light hydrocarbons) is limited. The MMA-yield is mainly dependent on the residence time of the gas in the reactor and to a lesser extent on the operating temperature. The paper presents experimental work performed in a lead bath and in a fluidised bed. At low temperatures, the reaction is kinetically controlled, whereas at high temperatures, heat transfer restricts the overall reaction rate. It was demonstrated that the heat transfer in the fluid bed could be estimated by the equation of Kothari. A design procedure for a fluid bed PMMA-depolymerisation reactor is outlined and illustrated for a process of 1 tpd PMMA.     

Migration of radionuclides in porous rock in the presence of colloids: effects of kinetic interactions

This work investigates the colloid-facilitated migration of radionuclides with radioactive decay in porous media. The sorption processes for radionuclides with both the solid matrix and colloids are treated as equilibrium or nonequilibrium. An analytical solution is obtained from a simplified linear equilibrium interaction mechanism. In addition, the adsorption processes for radionuclides with colloids and porous rock can be assumed as nonequilibrium and modeled by the linear kinetic adsorption. The numerical method is employed to solve the coupled colloid and radionuclide transport equations under nonequilibrium sorption assumption. Moreover, the reaction rates of the adsorption processes for radionuclides with the solid matrix and colloids affect the transport characteristics of radionuclides. The fast reaction rate of radionuclides with colloids causes a higher concentration of radionuclides adsorbed on colloids in a dispersed phase and enlarges acceleration caused by colloids. However, the fast reaction rate for radionuclides with solid matrix increases the retardation effect caused by the solid matrix. This work developed a predictive model for the transport of colloid-facilitated radionuclides in porous medium and to assess the importance of various phenomenological coefficients, particularly parameters for the adsorption interactions.     

Use of Performance Models in Restoration Projects

Environmental restoration projects can benefit from using performance models tied to monitoring plans and closure/exit strategies. Theoretical aspects are discussed and a case study is provided to illustrate how models can be developed and applied. Recognizing that site characterization cannot remove all uncertainty, most performance models cannot be narrowly developed (e.g., specific concentrations expected over time). Instead they must define threshold values at which performance data indicate the remedy is failing, or at least is not operating at the required level to achieve objectives within a reasonable timeframe. Ultimately, the performance model should be transformed to a closure model. The closure model is intended to document how closure was achieved and what measures remain in place to ensure protection of human health and the environment. In this context, the performance model is an intermediate step in the sequence starting from a conceptual site model and ending as the closure model. © 2014 Wiley Periodicals, Inc.     

撞击流技术在环保领域的应用研究进展

撞击流作为一种过程强化技术,其优势在于能够显著强化相间传递和微观混合,可应用于环保工艺、设备中,以达到提高污染物去除效率的目的。本文在简述撞击流基本原理和特性的基础上,详细阐述了国内外撞击流技术在细颗粒物(PM2.5)脱除、烟气脱硫脱硝、废水处理、废气吸收等方面的应用现状,分析了该技术的应用效果和优势,同时介绍了一种可用于废水处理的新型双组分层式撞击流反应器。最后指出,深入探究撞击流复杂体系的机理以及耦合其他新型技术是未来研究的主要方向。     

Policy trends of e-waste management in Asia

This paper examines the policy trends of electronic waste (e-waste) management in Asia. E-waste is a rapidly growing waste stream in the world today and is estimated to be growing at 3–5 % per annum. Fast paced obsolescence in the electronic sector has resulted in the generation of e-waste. There are concerns that e-waste generated in developed countries is ending up in developing countries especially in Asia resulting in adverse environmental and health impacts. Consequently, a number of countries in Asia are developing policy instruments to ensure the proper management of e-waste. These include e-waste regulatory frameworks, data and inventories, and infrastructure and capacity building. These trends indicate a positive development path towards sustainable e-waste management in Asia. Nevertheless, potential limiting obstacles for e-waste management in Asia may also include an over-reliance on legislation to drive e-waste management or the simplistic adoption of policies from developed countries without taking into context the local political, cultural and socio-economic waste management issues. Consequently, this paper suggest that e-waste policy development may require a more customized approach where, instead of addressing e-waste in isolation, it should be addressed as part of the national development agenda that integrates green economy assessment and strategic environmental assessment as part of national policy planning. In conclusion, policy trends of e-waste management in Asia appear promising provided there is a paradigm shift from an e-waste perception of an environment problem to a e-waste perception of a potential opportunity as sustainable national green growth strategy in Asia.     

The presence of zinc in Swedish waste fuels

Zinc (Zn) is a chemical element that has gained more attention lately owing to its possibility to form corrosive deposits in large boilers, such as Waste-to-Energy plants. Zn enters the boilers in many different forms and particularly in waste, the amount of Zn is hard to determine due to both the heterogeneity of waste in general but also due to the fact that little is yet published specifically about the Zn levels in waste. This study aimed to determine the Zn in Swedish waste fuels by taking regular samples from seven different and geographically separate waste combustion plants over a 12-month period. The analysis shows that there is a relation between the municipal solid waste (MSW) content and the Zn-content; high MSW-content gives lower Zn-content. This means that waste combustion plants with a higher share of industrial and commercial waste and/or building and demolition waste would have a higher share of Zn in the fuel. The study also shows that in Sweden, the geographic location of the plant does not have any effect on the Zn-content. Furthermore, it is concluded that different seasons appear not to affect the Zn concentrations significantly. In some plants there was a clear correlation between the Zn-content and the content of other trace metals.     

活性污泥焚烧过程中镍的迁移分布特性

采用管式炉对污水厂活性污泥焚烧过程中Ni的迁移分布特性进行研究。实验结果表明：当污泥掺烧量（污泥质量与煤和污泥总质量的比）为25%时，Ni的挥发率（飞灰与气体中Ni质量的总和与污泥中Ni质量的比）几乎为零，且污泥与煤混合试样的综合燃烧效果最好；当污泥焚烧加入硫化物时，各种硫化物对Ni的残留率（炉渣中Ni的质量与污泥中Ni质量的比）提高能力大小顺序为Na₂S>S>Na₂SO₃>Na₂SO₄；当污泥焚烧加入氯化物时，促使Ni向烟气中迁移，且加入无机氯更易使Ni向烟气中迁移。     

Quantifying the waste reduction potential of using prefabrication in building construction in Hong Kong

As Hong Kong is a compact city with limited available land and high land prices, the construction of high-rise buildings is prevalent. The construction industry produces a significant amount of building waste. In 2005, about 21.5 million tonnes of construction waste were generated, of which 11% was disposed of in landfills and 89% in public filling areas. At the present rate, Hong Kong will run out of both public filling areas and landfill space within the next decade. The government is taking action to tackle the problem, such as by introducing a construction waste landfill charge, and promoting prefabrication to reduce on-site waste generation. This paper reports an ongoing study on the use of prefabrication in buildings and its impact on waste reduction in Hong Kong. A questionnaire survey was administered to experienced professionals, and case studies of recently completed building projects were conducted. The results revealed that construction waste reduction is one of the major benefits when using prefabrication compared with conventional construction. The average wastage reduction level was about 52%. This implies that a wider use of prefabrication could considerably reduce construction waste generation in Hong Kong and alleviate the burdens associated with its management.     

The ecological relevance of transport in waste disposal systems in Western Europe

With the development of modern waste management systems in Western Europe, a remarkable increase in the distances for waste transportation has been observed. The question thus arises whether recycling with longer transport distances is ecologically advantageous or whether disposal without recycling is to be preferred. This situation was analysed using selected product and waste streams. This included refrigerators, paper, polyethylene films and expanded polystyrene. For each of these streams, a life cycle analysis was conducted with an emphasis on waste transport. The system boundaries were set in terms of the generation of waste to recycling or landfilling. The comparison included several scenarios with recycling and different transport distances. Landfilling was used as the reference scenario. The results obtained demonstrated how transport distances influence the ecological benefit of recycling. In the case of expanded polystyrene, the ecological boundaries are reached in practical situations, while with other materials these boundaries are far from being attained. In these cases, more complex and elaborate collection schemes, such as kerbside collection, which is economically convenient and shows the highest collection rates, can also be recommended.     

Clogging of finger drain systems in MSW landfills

A numerical model ‘BioClog’ is used to examine clogging of granular drainage material within finger drains at the base of landfills. The reduction in porosity of drainage material is evaluated as the accumulation of clog mass reduces the pore spaces of granular media. The leachate mounding within the landfills caused by the reduction in hydraulic conductivity of finger drain is modeled. The effect of overburden pressure on the engineering properties of waste material and consequent leachate mounding is considered. The calculated rates of leachate mound development for two landfills with finger drain leachate collection are shown to be in encouraging agreement with the observed data at the times when data were available. It is demonstrated that a significant leachate mound can be expected to develop over time when the leachate collection system is comprised of finger drains; however the rate of increase and the magnitude at a given time will depend on a number of factors including the grainsize, thickness and spacing of the finger drains, and the thickness of waste as well as the leachate generation rate.     

Utilization of pulverized fuel ash in Malta

In Malta all of the waste produced is mixed and deposited at various sites around the island. None of these sites were purpose built, and all of the waste is above groundwater level. The landfills are not engineered and do not contain any measures to collect leachate and gases emanating from the disposal sites. Another waste, which is disposed of in landfills, is pulverized fuel ash (PFA), which is a by-product of coal combustion by the power station. This has been disposed of in landfill, because its use has been precluded due to the radioactivity of the ashes. The aim of this study was to analyze the chemical composition of the pulverized fuel ash and to attempt to utilize it as a cement replacement in normal concrete mixes in the construction industry. The levels of radiation emitted from the ashes were measured by gamma spectrometry. The results of this study revealed that although at early ages cement replacement by PFA resulted in a reduction in compressive strength (P=0), when compared to the reference concrete at later ages the strengths measured on concrete cores were comparable to the reference concrete (P>0.05). The utilization of PFA up to 20% cement replacement in concrete did not raise the radioactivity of the concrete. In conclusion, utilization of PFA in the construction industry would be a better way of disposing of the ashes rather than controlling the leachate and any radioactivity emitted by the landfilled ashes.     

Use of lignin degrading fungi in bioremediation

The use of lignin degrading fungi for decomposition of a wide variety of xenobiotics has become an area of intensive research. One distinct advantage of lignin degrading fungi over bacteria is that they do not require preconditioning to a particular pollutant prior to transformation. This degradative ability has been attributed to a nonspecific and nonstereoselective extracellular lignin-degrading enzymatic system (ligninase) which is induced by the fungi under nitrogen or carbon-limiting conditions (Reid, 1979). Ligninases (lignin-peroxidases) are responsible for the initial oxidative attack on lignin and other complex molecules via formation of a free radical thereby leading to depolymerization of complex molecular structures. Potential degradative ability of peroxidases may extend to include (1) sorbed contaminants, (2) high molecular-weight, hydrophobic contaminants, and (3) complex mixtures of chemicals typical of a contaminated site.     

Treatment of creosote-contaminated groundwater in vegetated sorption/bio-barriers in cold climates

Permeable barriers are structures installed in situ to treat contaminated groundwater. Pollutants are removed as contaminated groundwater flows through a barrier material. A compost/sand barrier and a plant covered permeable barrier with soil/sand and peat/sand were tested in pilot-scale to treat creosote-contaminated groundwater by sorption and biological removal in situ. Outlet concentrations of the barriers were consistently low during the 29 months of operation. Although sorption sites were filled up with polycyclic aromatic hydrocarbons, they seemed to be regenerated because of biodegradation under aerobic conditions. The vegetated section was least efficient, probably because of lack of oxygen, hence it could not be determined if the plants had a positive effect. As long as biodegradation is efficient the barrier is expected to function for several more years.     

Management of MSW in Spain and recovery of packaging steel scrap

Packaging steel is more advantageously recovered and recycled than other packaging material due to its magnetic properties. The steel used for packaging is of high quality, and post-consumer waste therefore produces high-grade ferrous scrap. Recycling is thus an important issue for reducing raw material consumption, including iron ore, coal and energy. Household refuse management consists of collection/disposal, transport, and processing and treatment - incineration and composting being the most widely used methods in Spain. Total Spanish MSW production exceeds 21 million tons per year, of which 28.1% and 6.2% are treated in compost and incineration plants, respectively. This paper presents a comprehensive study of incineration and compost plants in Spain, including a review of the different processes and technologies employed and the characteristics and quality of the recovered ferrous scrap. Of the total amount of packaging steel scrap recovered from MSW, 38% comes from compost plants and 14% from incineration plants. Ferrous scrap from incineration plants presents a high degree of chemical alteration as a consequence of the thermal process to which the MSW is subjected, particularly the conditions in which the slag is cooled, and accordingly its quality diminishes. Fragmentation and magnetic separation processes produce an enhancement of the scrap quality. Ferrous scrap from compost plants has a high tin content, which negatively affects its recycling. Cleaning and detinning processes are required prior to recycling.     

含腈废水处理过程中污染物的转化规律

对某石化企业含腈废水的处理工艺进行了评估,从污染物的来源、组成、处理效果等方面研究了污染物的转化规律,揭示了现有工艺在含腈废水处理过程中的问题。实验结果表明:该企业污水处理场的废水来源较多,丙烯腈生产废水经四效蒸发系统处理后的出水是其污染物的主要来源,含有相对较多的含氮共轭体系;与其他废水混合后,经氨化作用,有机腈转变为有机胺和铵盐;A/O工段矿化度较高,COD的去除率高达73.0%,但有机胺含量仍较高;在缺氧池—生物流化池—硝化池工段,COD进一步被去除,胺类物质浓度大幅降低,但总氮脱除效果并不理想。