Analysis of ingredient and heating value of municipal solid waste

Great differences between municipal solid wastes(MSW)produced at different places and different times in terms of such parameters as physical ingredient and heating value lead to difficulty in effective handling of MSW. In this paper, ingredient, heating value and their temporal varying trends of typical MSW in Beijing were continuously measured and analyzed. With consideration of the process in pyrolysis and incineration, correlation between physical ingredients and heating values was induced, favorable for evaluation of heating value needed in handling of MSW from simple analysis of physical ingredients of it.

Hydrogen production characteristics of the organic fraction of municipal solid wastes by anaerobic mixed culture fermentation

The hydrogen production from the organic fraction of municipal solid waste (OFMSW) by anaerobic mixed culture fermentation was investigated using batch experiments at 37 degrees C. Seven varieties of typical individual components of OFMSW including rice, potato, lettuce, lean meat, oil, fat and banyan leaves were selected to estimate the hydrogen production potential. Experimental results showed that the boiling treated anaerobic sludge was effective mixed inoculum for fermentative hydrogen production from OFMSW. Mechanism of fermentative hydrogen production indicates that, among the OFMSW, carbohydrates is the most optimal substrate for fermentative hydrogen production compared with proteins, lipids and lignocelluloses. This conclusion was also substantiated by experimental results of this study. The hydrogen production potentials of rice, potato and lettuce were 134 mL/g-VS, 106 mL/g-VS, and 50 mL/g-VS respectively. The hydrogen percentages of the total gas produced from rice, potato and lettuce were 57-70%, 41-55% and 37-67%. 2008 International Association for Hydrogen Energy.

城市生活垃圾中微量金属元素含量的特性分析

城市生活垃圾中含有多种微量金属元素,可能会对环境和人们的健康造成危害.分析这些元素随着产地及时间的差别,了解它们在垃圾中的富集量,对于垃圾的处理和综合利用是非常重要的.在此通过连续监测1年内某沿海城市若干地区生活垃圾的组成成分,得到了垃圾中微量金属元素的原始数据,探讨了微量金属元素随来源和季节的分布规律,并进行了较为详尽的讨论.

城市生活有机垃圾厌氧降解的过程机理与工程应用研究

首先进行城市生活有机垃圾典型组分的厌氧发酵产甲烷和产氢特性研究，在此基础上，设计厌氧发酵联产氢气和甲烷的组合工艺提高能源回收效率，并采用厨余垃圾和废纸联合厌氧消化的方式避免厨余垃圾单独厌氧消化的挥发性脂肪酸抑制。其次，结合国内近年出现的城市生活垃圾分选技术，分别以机械干分选有机垃圾和水分选有机垃圾为原料进行厌氧发酵产甲烷实验，并根据实验结果设计日处理500吨城市生活垃圾厌氧沼气工程及进行经济性评价。主要结论如下：（1）糖和淀粉类的生化产甲烷能力为260 mL/gVS，纤维素，粗纤维、蛋白类和脂类分别为244、145、258 、757 mL/gVS；蛋白质类原料在厌氧消化过程中容易形成“抑制型稳态”；脂类原料容易导致长链脂肪酸抑制。（2）碳水化合物（糖、淀粉和纤维素）是最佳的厌氧发酵制氢原料，蛋白类、脂类和木质纤维类均不适宜作为厌氧发酵制氢原料。采用厌氧发酵联产氢气和甲烷的组合工艺可以显著提高能源回收率。（3）厨余垃圾单独厌氧发酵容易受到VFAs的强烈抑制，采用厨余垃圾与废纸联合厌氧发酵，能够避免VFAs抑制。（4）水分选有机垃圾的生物可降解性优于机械干分选有机垃圾，在原料TS浓度为11%~16%时的甲烷产率为273~314 L/kgVS。（5）国家财政补贴，税收优惠和CDM额外收益决定了城市生活垃圾的厌氧消化与热电肥联产工程的经济可行性。

Species transformation of trace elements and their distribution prediction in dyestuff residue incineration

The release of heavy metals from the combustion of hazardous wastes is an environmental issue of increasing concern. The species transformation characteristics of toxic heavy metals and their distribution are considered to be a complex problem of mechanism. The behavior of hazardous dyestuff residue is investigated in a tubular furnace under the general condition of hazardous waste pyrolysis and gasfication. Data interpretation has been aided by parallel theoretical study based on a thermodynamic equilibrium model based on the principle of Gibbs free energy minimization. The results show that Ni, Zn, Mn, and Cr are more enriched in dyestuff residue incineration than other heavy metals (Hg, As, and Se) subjected to volatilization. The thermodynamic model calculation is used for explaining the experiment data at 800 degrees C and analyzing species transformation of heavy metals. These results of species transformation are used to predict the distribution and emission characteristics of trace elements. Although most trace element predictions are validated by the measurements, cautions are in order due to the complexity of incineration systems.

垃圾渗滤液场外硝化－原位反硝化脱氮协同填埋场温室气体减排

垃圾卫生填埋是国内外城市垃圾的主要处置方法。垃圾渗滤液是渗入填埋场垃圾的降水混合垃圾降解过程中产生的物质而形成的混合物，是垃圾填埋场向环境排放的主要污染物。渗滤液由于其所含高浓度有机和无机污染物，且其中很多物质有生物毒性或难生物降解，难于治理。特别是到填埋晚期，渗滤液中高浓度的氨氮更是增加了治理的难度。渗滤液场外硝化－原位反硝化是填埋场氮管理的新途径。本文利用从环境中筛选出优势硝化功能菌对渗滤液中的高浓度氨氮进行生物硝化，经硝化后的渗滤液回灌至以垃圾柱模拟的生物反应器填埋场，在填埋场内实现原位反硝化。 上述目标通过以下两部分来实现： 第一部分：渗滤液场外硝化。首先从污水厂的硝化污泥中富集并筛选出硝化功能菌，在模拟氨氮废水中优化。将驯化的硝化功能菌接种于连续式完全混合反应器（CSTR）进行高氨氮渗滤液硝化研究。在200余天的连续运行中，反应器硝化和有机物去除效果良好。在最大氨氮负荷和有机物负荷分别为0.65 g N l-1 d-1 和3.84 g COD l-1 d-1时，氨氮和COD去除率分别高于99%和57%。实验过程中发现，游离氨（FA）和溶解氧（DO）浓度对反应器中亚硝酸盐的积累影响很大。 第二部分：渗滤液原位反硝化。本文利用一个垃圾填充柱模拟生物反应器填埋场，研究了硝化渗滤液回灌对垃圾降解的影响，和回灌的硝化渗滤液中TON（总氧化态氮）对填埋场生物反应器产甲烷作用的影响。最后利用变性梯度凝胶电泳（DGGE）分析了硝化渗滤液回灌对垃圾填埋场菌群结构的影响。结果表明：回灌的TON被完全还原，反硝化为主要反应，最大TON负荷为28.6 mg N kg-1 TS d-1。当垃圾柱TON负荷大于11.4 mg N kg-1 TS d-1时，出现了产甲烷抑制，抑制作用随TON负荷的增加而加强。在此过程中，反硝化逐渐代替产甲烷作用成为填埋场内垃圾降解的主要反应，且更多产生的是清洁的氮气，而非温室气体甲烷。直到实验结束时，回灌硝化渗滤液的垃圾柱的甲烷产量仅相当于对照的2.5%，并且回灌的硝化渗滤液还加速了填埋场垃圾的降解与稳定。通过DGGE进行菌群结构分析发现，由于TON对填埋场的长期作用，反硝化菌增多而产甲烷菌减少。 Landfill still remains the chief method for MSW management around the world. Leachate is a mixture of rainfall permeating through landfill and organic and inorganic matters generated during decomposition of the wastes in the landfills, characterized as highly complicated and refractory wastewater. Ex-situ nitrification and sequential in-situ denitrification represents a novel approach to nitrogen management at landfills. In the present paper, nitrification was carried out in a continuous stirred tank reactor (CSTR) inoculated with nitrifying bacteria which were isolated from municipal WWTP of Chengdu city. The nitrified leachate from CSTR was recirculated to a lab-scale municipal solid waste (MSW) column where in-situ denitrification took place. The above object was achived through two parts as following: First, ex-situ nitification of leachate. After acclimated in simulated wastewater for 3 month, nitrifying bacteria isolated from WWTP nitrifying sludge were added to the CSTR for nitrification. The results over 200 days showed that the maximum nitrogen loading rate (NLR) and the maximum organic loading rate (OLR) was 0.65 g N l-1 d-1 and 3.84 g COD l-1 d-1, respectively. The ammonia and COD removal was over 99% and 57%, respectively. Moreover, the effects of free ammonia (FA) and dissolved oxygen (DO) on nitrification were investigated. Second, in-situ denitrification was studied in a municipal solid waste (MSW) column. Variation of nitrified leachate and its effects on the decomposition of municipal solid waste (MSW) were studied in a lab-scale MSW column to which nitrified leachate was recirculated. Additionally, DGGE was employed to investigate the microbial community of both MSW columns. The results suggested: complete reduction of total oxidized nitrogen (TON) was obtained with maximum TON load of 28.6 mg N kg-1 TS d-1 and denitrification was the main reaction responsible. Methanogenesis inhibition was observed while TON load was over 11.4 mg N kg-1 TS d-1 and the inhibition was enhanced with the increase of TON load. Denitrification gradually took over methanogenesis to become the main reaction responsible for decomposition of MSW while nitrogen gas, a clean byproduct, was generated instead. Till the end of the experiment, the average weekly methane production in the denitrification column was as low as 2.5% of that of the control, and the rate of decompition and stability of MSW was accelerated by the recirculation of the nitrified leachate.Owing to long term exposure of nitrified leachate to landfill, denitrifying bacteria increased and methanogen decreased.

流化床中废弃物颗粒的横向扩散特性

在试验基础上计算得到内循环流化床和鼓泡床中3种轻质废弃物颗粒和两种重质颗粒的横向扩散系数,发现废弃物颗粒的变形程度、密度、尺寸及布风板形状和布风方式均影响其扩散系数.轻质颗粒的运动符合扩散规律,重质粒子的运动则不符合该规律.文中从流化床中气体颗粒流和不同物性废弃物相互作用的角度简要分析了物料的扩散特性.

Heavy metal pollution in China: Origin, pattern and control

Goal, Scope and Background. Heavy metal is among one of the pollutants, which cause severe threats to humans and the environment in China. The aim of the present review is to make information on the source of heavy metal pollution, distribution of heavy metals in the environment, and measures of pollution control accessible internationally, which are mostly published in Chinese. Methods. Information from scientific journals, university journals and governmental releases are compiled focusing mainly on Cd, Cu, Pb and Zn. Partly Al, As, Cr, Fe, Hg, Mn and Ni are included also in part as well. Results and Discussion. In soil, the average contents of Cd, Cu, Pb and Zn are 0.097, 22.6, 26.0 and 74.2 mg/kg, respectively. In the water of. the Yangtze River Basin, the concentrations of Cd, Cu, Pb and Zn are 0.080, 7.91, 15.7 and 18.7 pg/L, respectively. In reference to human activities, the heavy metal pollution comes from three sources: industrial emission, wastewater and solid waste. The environment such as soil, water and air were polluted by heavy metals in some cases. The contents of Cd, Cu, Pb and Zn even reach 3.16, 99.3, 84.1 and 147 mg/kg, respectively, in the soils of a wastewater irrigation zone. These contaminants pollute drinking water and food, and threaten human health. Some diseases resulting from pollution of geological and environmental origin, were observed with long-term and non-reversible effects. Conclusions. In China, the geological background level of heavy metal is low, but with the activity of humans, soil, water, air, and plants are polluted by heavy metals in some cases and even affect human health through the food chain. Recommendations and Outlook. To remediate and improve environmental quality is a long strategy for the polluted area to keep humans and animals healthy. Phytoremediation would be an effective technique to remediate the heavy metal pollutions.

Organic carbon source and burial during the past one hundred years in Jiaozhou Bay, North China

Organic carbon (OC), total nitrogen (TN), and Pb-210 in core sediment were measured to quantify the burial of organic carbon and the relative importance of allochthonous and autochthonous contributions during the past one hundred years in Jiaozhou Bay, North China. The core sediment was dated using Pb-210 chronology, which is the most promising method for estimation of sedimentation rate on a time scale of 100-150 years. The variation of the burial flux of organic carbon in the past one hundred years can be divided into the following three stages: (1) relatively steady before 1980s; (2) increasing rapidly from the 1980s to a peak in the 1990s, and (3) decreasing from the 1990s to the present. The change is consistent with the amount of solid waste and sewage emptied into the bay. The OC:TN ratio was used to evaluate the source of organic carbon in the Jiaozhou Bay sediment. In the inner bay and bay mouth, the organic carbon was the main contributor from terrestrial sources, whereas only about half of organic carbon was contributed from terrestrial source in the outer bay. In the inner bay, the terrestrial source of organic carbon showed a steady change with an increase in the range of 69%-77% before 1990 to 93% in 2000, and then decreased from 2000 because of the decrease in the terrestrial input. In the bay mouth, the percentage of organic carbon from land reached the highest value with 94% in 1994. In the outer bay, the sediment source maintained steady for the past one hundred years.