Investigation of basic properties of fly ash from urban waste incinerators in China

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.

Solid Waste Generation and Composition in Mexico： A Comparison between Rural and Urban Communities

This paper reports a generation and composition analysis of household solid waste in Mexico, using as a reference the characterization study performed in two communities, one urban and one rural. Data obtained are fundamental parameters for the planning of urban solid waste management systems in Mexico, complying this way with the established policy in the National Program for Waste Management and Prevention 2009-2012. The study was carried out during five days and two main parameters were assessed： （1） the daily generation rate per person and （2） the waste composition. The per capita waste generation was 0.958 kg for the urban community and 0.631 kg for the rural. The results showed that the mean composition of waste from both locations was statistically similar （a = 0.05）. In both locations the most important contribution was the fraction of food waste. In both locations more than 60% of the waste is potentially recyclable. The results of this study will be used by the municipal waste authorities in order to establish an integrated waste management plan.

Controlled low-strength material incorporating recycled fine aggregate from urban red brick based construction waste

Sixteen controlled low-strength material( CLSM)mixtures with various cement-to-sand( C/Sa) ratios and water-to-solid( W/So) ratios were prepared using recycled fine aggregate from urban red brick based construction waste.The fluidity and bleeding of the fresh CLSM mixtures were measured via the modified test methods, and the hardened CLSM mixtures were then molded to evaluate their compressive strength and durability. The results showthat the fluidity of the fresh CLSM mixtures is 105 to 227 mm with the corresponding bleeding rate of 3. 7% to 15. 5%, which increases with the increase in fluidity. After aging for 28 d,the compressive strength of the hardened CLSM mixtures reaches 1. 15 to 13. 96 M Pa, and their strength can be further enhanced with longer curing ages. Additionally, the strength increases with the increase of the C/Sa ratio, and decreases with the increase of the W/So ratio under the same curing age. Based on the obtained compressive strength, a fitting model for accurately predicting the compressive strength of the CLSM mixtures was established, which takes into account the above two independent variables( C/Sa and W/So ratios).M oreover, the durability of the hardened CLSM mixtures is enhanced for samples with higher C/Sa ratios.

Multi-Actor Geo-Collaborative Device for Collecting Household Waste in Urban Areas: A Case Study of Lamkansa District, Casablanca, Morocco

The aim of this paper is to develop a Multi-Actor Geo-Collaborative Device to improve the processes of household waste collect (HWC) in urban areas. The proposed device will be tested in the Lamkansa district, in the southwestern part of Casablanca city, Morocco. The approach used is a systemic analysis of communication in order to act on a territory. We have been inspired by several methodological developments concerning multi-actor processes of land use planning. We focused our work on the involvement of the inhabitants in the process of household waste collect. The results show that the urban population can help and contribute to the development of complementary solutions to improve the urban environment and their living environment. Moreover, by integrating citizens in HWC processes, as well as decision communication, we can reduce household waste management costs and make it faster and more efficient, through a geo-collaborative, participatory and incentive logic. The approach described in this article is original, not only considering the technologies used to present and share the collected information, but also regarding the concept of integrating several actors in a collaborative/incentive mode. It arouses great interest by combining geomatics with communication and information sciences. It contributes to improve the participation of the inhabitants in the life of their urban environment in order to establish a reinforced dialogue on the future of their city and public health. Also, it involves the development and testing of new devices and tools for multi-actor collaboration.

Corrosion of Disposing Urban Domestic Wastes on Refractories for Cement Rotary Kilns

Corrosion of burning urban domestic wastes to alkali-resistant bricks and spalling-resistant high alumina bricks was researched by static crucible method and SEM in order to choose refractories for cement rotary kilns for collaboratively disposing wastes. The result indicates that the main corrosion mechanism is slag permeation and corrosion ; the emitted high temperature gases containing alkali, sulfur and chlorine during burning the wastes re- act with refractories forming low melting point sulfate, chloride and compound salts, which metamorphose the refractories, and the loose metamorphic layer is easy to spall under thermal stress. So, corrosion resistance and spaUing resistance shall be taken into account when choosing refractories for cement rotary kilns for collaboratively disposing wastes. It is suggested that decomposition furnaces should adopt spaUing resistant high alumina bricks and anti-coating SiC castables, and preheating equipment should adopt high strength alkali-resistant bricks and castables.

Evaluation of the efficiency of urban solid waste management in Brazil by data envelopment analysis and possible variables of influence

This article has the general objective of estimating the efficiency of urban solid waste management in 940 Brazilian munici-palities through Data Envelopment Analysis(DEA)technique and has specific objectives:(i)to estimate efficiency scores;(ii)to compare the performance between different groups of municipalities;and(ii)to analyze the profile of efficient munici-palities from the perspective of the guidelines of Law 12,305/2010 and socio-economic and environmental indicators.The technique used was DEA with output-oriented and variable scale to return modeling.The results showed higher efficiency scores in the municipalities with populations above 500,000 inhabitants.The score variation ranged from 0.5(municipalities with populations<10,000 inhabitants)to 0.9(municipalities with more than 500,000 inhabitants).Of the sample set,only 12.34%of the municipalities were considered efficient,and when analyzing the efficient group,it was found that adherence to legislation was not a major factor in achieving efficiency.

Landfill Sites Identification Using GIS and Multi-Criteria Method: A Case Study of Intermediate City of Punjab, Pakistan

Escalation in population over time triggered the abrupt exploitation of natural resources for human survival trough industrialization that ultimately caused splendid increase in the waste generation. This industrial development resulted in the migration of rural community toward urban areas. Management of urban waste is a great challenge for the urban administration. However, technologies have been developed to manage the waste in environmental friendly and sustainable manner. Sanitary landfill sites are one of the latest methods of disposing the municipal solid waste in an environment friendly and sustainable manner. Government and administrative authorities are adopting this technology for the management of urban solid waste. Present study is about identifying landfill sites for the Sahiwal city with an area of 1160 square kilometer and projected population of 1.57 million persons in 2016. Geographical Information System (GIS) is used for the identification of appropriate landfill site (LFS) that can fulfill the need of city in future and is selected based on the sustainable and eco-friendly criteria. The criteria are developed keeping in view the proximity from several land-use features i.e. water bodies, roads, settlements, agricultural land, bare land and existing disposal sites. The weights of the criteria are quantified using pair-wise comparison method in Analytic Hierarchy Process (AHP). The weights are incorporated in GIS spatial data environment and are assigned to proximity threshold of each criterion. Ultimately a map for each criterion is developed highlighting suitable, least suitable, less suitable and un-suitable areas with respect to each specific criterion. These maps are spatially overlaid which result in a final map that identifies most suitable landfill sites for solid waste disposal. The five identified sites are then prioritized based on their distances from the city center and area available. All identified sites are on the bare land and contain considerable buffer from environmentally sensitive receptors.