Overview of non-hazardous solid waste in the small island state of Mauritius

In Mauritius, solid waste disposal has been a cause for concern since the 1980s. Currently, there is no segregation of waste and some 1200 tonnes of solid waste are generated daily by the 1.24 million inhabitants of the island. As processes such as recycling and composting are still in their infancy stage, most of the waste generated have to be disposed of at the sole landfill. The solid waste management practices of 1980s and early 1990s are no longer compatible with the changing composition and quantity of wastes now generated. As a result, there is an urgency to review the whole waste management system and come forward with sustainable solutions.This paper presents an overview of the disposal of non-hazardous solid waste in Mauritius and provides recommendations for improving the current disposal system.     

水中3种微囊藻毒素的高效液相色谱测定方法优化

对天然水体中3种痕量微囊藻毒素（MC-RR、MC-YR、MC-LR）的淋洗、洗脱、液相色谱测定等环节进行单因素不同水平考察,结果表明：以体积分数为45%的甲醇水溶液（含0.1%的TFA）为固相萃取淋洗剂、10 mL甲醇（含01%TFA）为固相萃取洗脱剂,体积分数为70%的甲醇水溶液（含0.1%TFA）为液相色谱流动相,可在6 min内有效分离MC-RR、MC-YR、MC-LR。将优化后的方法用于实际加标水样的测定,MC-RR、MC-YR、MC-LR的方法检出限分别为0.064 μg/L、0.098 μg/L、0.095 μg/L,加标回收率为87.0%~116%,RSD为10.2%~18.8%。     

高温蒸汽灭菌处理技术处置医疗废物工艺设计

高温蒸汽灭菌处理技术是近几年开发的新型医疗废物处置技术,并在全国部分地区得到了应用和推广。以西北某市医疗废物处置工程中高温蒸汽灭菌处理技术的应用为例,通过对其工程原理、系统组成、工艺流程等的分析论证共同探讨其工程原理和性能特点,为今后在工程实际中的运用提供参考。     

Use of thermal analysis techniques (TG-DSC) for the characterization of diverse organic municipal waste streams to predict biological stability prior to land application

The use of organic municipal wastes as soil amendments is an increasing practice that can divert significant amounts of waste from landfill, and provides a potential source of nutrients and organic matter to ameliorate degraded soils. Due to the high heterogeneity of organic municipal waste streams, it is difficult to rapidly and cost-effectively establish their suitability as soil amendments using a single method. Thermal analysis has been proposed as an evolving technique to assess the stability and composition of the organic matter present in these wastes. In this study, three different organic municipal waste streams (i.e., a municipal waste compost (MC), a composted sewage sludge (CS) and a thermally dried sewage sludge (TS)) were characterized using conventional and thermal methods. The conventional methods used to test organic matter stability included laboratory incubation with measurement of respired C, and spectroscopic methods to characterize chemical composition. Carbon mineralization was measured during a 90-day incubation, and samples before and after incubation were analyzed by chemical (elemental analysis) and spectroscopic (infrared and nuclear magnetic resonance) methods. Results were compared with those obtained by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. Total amounts of CO₂ respired indicated that the organic matter in the TS was the least stable, while that in the CS was the most stable. This was confirmed by changes detected with the spectroscopic methods in the composition of the organic wastes due to C mineralization. Differences were especially pronounced for TS, which showed a remarkable loss of aliphatic and proteinaceous compounds during the incubation process. TG, and especially DSC analysis, clearly reflected these differences between the three organic wastes before and after the incubation. Furthermore, the calculated energy density, which represents the energy available per unit of organic matter, showed a strong correlation with cumulative respiration. Results obtained support the hypothesis of a potential link between the thermal and biological stability of the studied organic materials, and consequently the ability of thermal analysis to characterize the maturity of municipal organic wastes and composts.     

Comparing the greenhouse gas emissions from three alternative waste combustion concepts

Three alternative condensing mode power and combined heat and power (CHP) waste-to-energy concepts were compared in terms of their impacts on the greenhouse gas (GHG) emissions from a heat and power generation system. The concepts included (i) grate, (ii) bubbling fluidised bed (BFB) and (iii) circulating fluidised bed (CFB) combustion of waste. The BFB and CFB take advantage of advanced combustion technology which enabled them to reach electric efficiency up to 35% and 41% in condensing mode, respectively, whereas 28% (based on the lower heating value) was applied for the grate fired unit. A simple energy system model was applied in calculating the GHG emissions in different scenarios where coal or natural gas was substituted in power generation and mix of fuel oil and natural gas in heat generation by waste combustion. Landfilling and waste transportation were not considered in the model. GHG emissions were reduced significantly in all of the considered scenarios where the waste combustion concepts substituted coal based power generation. With the exception of condensing mode grate incinerator the different waste combustion scenarios resulted approximately in 1 Mton of fossil CO₂-eq. emission reduction per 1 Mton of municipal solid waste (MSW) incinerated. When natural gas based power generation was substituted by electricity from the waste combustion significant GHG emission reductions were not achieved.     

Building partnerships — the Ohio Materials Exchange

This paper discusses a method by which individuals working in government, private business, not-for-profit and educational organizations developed a collaborative statewide program involving the exchange of materials from manufacturers, commercial business and not-for-profit organizations in Ohio.     

固体废物相关概念的基本特点

固体废物法对废物的一些概念进行了定义,在固体废物环境管理当中,对这些概念缺乏深入认识,导致在实际管理中对固体废物和危险废物的调查、认定、统计、管理、预测、设施建设等一系列与废物相关的行动出现偏差甚至不准确。对固体废物、危险废物以及废物利用、处置、贮存、排放等概念包含的内容进行了研究,提出了一些新的认识观点。     

垃圾填埋场细菌种群空间分布及组成多样性研究

采用PCR-DGGE技术对垃圾填埋场细菌种群垂直分布及组成多样性进行了研究．结果表明：垃圾填埋场细菌种群组成波动较大,某些种群对环境因子的变化十分敏感．在填埋年龄已达3a的取样点,细菌种群的多样性随着垃圾填埋深度的增加而呈现“多—少—多”的变化趋势。各种群间相对密度也呈现由不均一到均一的变化规律,部分层次优势种和非优势种发生较大变化．填埋深度4．0m至6．25m左右的区域是填埋场微生物区系组成发生变化的过渡区,该区域细菌种群的多样性较小,亲缘关系相差比较大的种交叉在一起,具有明显的过渡特征．从时间因素来看,填埋场同层次微生物群落组成随时间延长,种群构成趋于稳定．表层垃圾1～2a内,细菌种群处于交替更叠的阶段,日趋发育成熟．8．25m以下层次的细菌种群主要受填埋深度影响,与填埋时间关系较小。     

Effect of steam hydration on performance of lime sorbent for CO2 capture

Lime is considered a feasible sorbent for the capture of CO₂ from large stationary sources. The positive attributes of a natural source material, low cost and lack of harmful by-products are offset by rapid deterioration in performance and high regeneration temperature. Performance can be improved by hydrating the lime using steam. We investigate a steam hydration process wherein lime is hydrated for 5 min at 300 °C and atmospheric pressure in a mixture of steam and CO₂. The experiments consisted of 10 capture cycles with 60% of the lime active at the end. Extrapolation using a decay model suggests a residual carbonation level of 48%, significantly higher than the 8% achieved by dry lime cycles. The cost of replacement sorbent under these conditions is less than $1/t of CO₂ captured. The hydrated lime process also reduces the thermal load, for heating and cooling, by half as well as the inventory, and therefore solids handling, by a factor 5 over dry lime. The introduction of the hydration reaction provides another exothermic reaction for heat management.     

Decomposition of paper wastes in presence of ceramics and cement raw material

Paper recycling is an environmental important activity that is carried out in all the countries, but during the recycling process a paper waste is produced. Generally these wastes are placed in landfill sites but it is possible to profit it as secondary fuel and raw material in manufacture furnaces.

In this work the combustion of the waste papers with cement and ceramic raw material has been studied with the objective to analyse the interaction of these substances with the emitted pollutants like PAHs and PCDD/Fs.

The results of the study show that the presence of inorganic material produces an increment in the lighter PAH emission but chlorinated compounds are not affected. The PCDD/F emission level found in the combustion of this waste is quite low compared with other wastes subjected to similar conditions.