A comparative study on the alternating mesophilic and thermophilic two-stage anaerobic digestion of food waste

An alternating mesophilic and thermophilic two stage anaerobic digestion(AD) process was conducted. The temperature of the acidogenic(A) and methanogenic(M) reactors was controlled as follows: System 1(S1) mesophilic A-mesophilic M;(S2) mesophilic A-thermophilic M; and(S3)thermophilic A-mesophilic M. Initially, the AD reactor was acclimatized and inoculated with digester sludge. Food waste was added with the soluble chemical oxygen demand(SCOD) concentrations of41.4–47.0 g/L and volatile fatty acids of 2.0–3.2 g/L. Based on the results, the highest total chemical oxygen demand removal(86.6%) was recorded in S2 while S3 exhibited the highest SCOD removal(96.6%). Comparing S1 with S2, total solids removal increased by 0.5%; S3 on the other hand decreased by 0.1 % as compared to S1. However, volatile solids(VS) removal in S1, S2, and S3was 78.5%, 81.7%, and 79.2%, respectively. S2 also exhibited the highest CH4 content, yield, and production rate of 70.7%, 0.44 L CH4/g VSadded, and 1.23 L CH4/(L·day), respectively. Bacterial community structure revealed that the richness, diversity, evenness, and dominance of S2 were high except for the archaeal community. The terminal restriction fragments dendrogram also revealed that the microbial community of the acidogenic and methanogenic reactors in S2 was distinct. Therefore,S2 was the best among the systems for the operation of two-stage AD of food waste in terms of CH4production, nutrient removal, and microbial community structure.     

Removal of organic matter and nitrogen from distillery wastewater by a combination of methane fermentation and denitrification/nitrification processes

Introduction D istillery w astew ater m ainly includes spent w ash, w hich is one of the m ost com plex, troublesom e industrial organic effluents. This kind of w astew ater has previously been treated aerobically after dilution w ith other w ash w aters.…     

甲烷煤尘耦合爆炸传播特性及伤害研究

为探究煤尘质量浓度对甲烷煤尘耦合爆炸传播特性及伤害距离的影响,自制长15 m的爆炸管道系统,用体积分数为7％甲烷分别与质量浓度为0、50、100和200 g/m3的煤尘进行耦合爆炸试验,并根据质量、动量和能量守恒理论推导出最大压力计算公式.结果 表明:不同质量浓度煤尘与甲烷耦合爆炸时,最大压力均随与爆源距离的增加呈现出...     

利用主成分分析法简化甲烷/空气层流预混火焰的反应机理

利用主成分分析(Principal Component Analysis)的方法对甲烷/空气氧化的详细化学反应机理进行了简化，在低压层流预混火焰条件下进行了计算，计算结果与详细机理的计算结果及实验值进行了比较。结果表明简化机理与详细机理吻合较好，简化机理的规模和计算时间有所减少。     

WASTE MANAGEMENT AND SUSTAINABLE DEVELOPMENT IN SOUTH AFRICA

Waste management is emerging as a key sector for sustainable development in South Africa with opportunities for enhancing investments in carbon credits that target reduction of methane from landfills and moveable assets in relation to environmentally sound equipment required for effective waste management. In the past, the waste management sector was dominated by private sector with selective operations in what makes business sense through recycling of saleable products. Materials mostly recycled included paper and hard board, plastics, glass, tinplate and aluminum. The rest of the waste materials estimated at 10.2 million tons of both general and hazardous end up in landfills. This trend is now getting reversed as development agencies such as Deutsche Gesellschaft für Technische Zusammenarbeit Gmbh (GTZ), Danish International Development Agency (DANIDA), Danish Co-operation for Environment and Development (DANCED) and Development Bank of Southern Africa (DBSA) are identifying opportunities in the sector for sustainable development purposes. Two key areas for investments include capturing methane emissions from landfills for trading in carbon markets and financing both physical and moveable assets to enhance sustainable development. However, the challenges for cost-effectiveness, efficiency and sustainability in the sector prevail in relation to lack of sound knowledge to design and implement integrated programmes that incorporate environment, development and sustainability. Also, inadequate capacity at municipal levels to administer waste management programmes and inability to collect rates and taxes for effective management of landfills constraint effectiveness and efficiency of the sector. Overall, financial resources are imperative to waste management and sustainable development as the sector requires capital investments for necessary infrastructure.     

The Potential Use of Synthetic Aperture Radar for Estimating Methane Ebullition From Arctic Lakes1

Abstract: Arctic lakes are significant emitters of methane (CH₄), a potent greenhouse gas, to the atmosphere; yet no rigorous quantification of the magnitude and variability of pan‐Arctic lake emissions exists. In this study, we demonstrate the potential for a new method using synthetic aperture radar (SAR) imagery to detect methane bubbles in lake ice to scale up whole‐lake measurements of CH₄ ebullition (bubbling) to regional scales. We estimated ebullition from lakes, which is often the dominant mode of lake emissions, by mapping the distribution of bubble clusters frozen in early winter ice across surfaces of seven tundra lakes and one boreal forest lake in Alaska. Applying previously measured ebullition rates associated with four distinct classes of bubble clusters found in lake ice, we estimated whole‐lake emissions from individual lakes. The percent surface area of lake ice covered with bubbles (R² = 0.68) and CH₄ ebullition rates from lakes (R² = 0.59) and were correlated with radar return values from RADARSAT‐1 Standard Beam mode 3 for the tundra lakes, suggesting that with appropriate scaling and consideration for variability in lake‐ice conditions, this technique has the potential to be used for estimating broader‐scale regional and pan‐Arctic lake methane emissions.     

Water Quality Changes as a Result of Coalbed Methane Development in a Rocky mountain Watershed1

Abstract: Coalbed methane (CBM) development raises serious environmental concerns. In response, concerted efforts have been made to collect chemistry, salinity, and sodicity data on CBM produced water. However, little information on changes of stream water quality resulting from directly and/or indirectly received CBM produced water is available in the literature. The objective of this study was to examine changes instream water quality, particularly sodicity and salinity, due to CBM development in the Powder River watershed, which is located in the Rocky Mountain Region and traverses the states of Wyoming and Montana. To this end, a retrospective analysis of water quality trends and patterns was conducted using data collected from as early as 1946 up to and including 2002 at four U.S. Geological Survey gauging stations along the Powder River. Trend analysis was conducted using linear regression and Seasonal Kendall tests, whereas, Tukey’s test for multiple comparisons was used to detect changes in the spatial pattern. The results indicated that the CBM development adversely affected the water quality in the Powder River. First, the development elevated the stream sodicity, as indicated by a significant increase trend of the sodium adsorption ratio. Second, the development tended to shrink the water quality differences among the three downstream stations but to widen the differences between these stations and the farthest upstream station. In contrast, the development had only a minor influence on stream salinity, as indicated by that the stream electrical conductivity exhibited either no trend or a marginally significant positive trend. Hence, the CBM development is likely an important factor that can be managed to lower the stream sodicity. The management may need to take into account that the effects of the CBM development were different from one location to another along the Powder River.     

Dissolved Oxygen and Nutrient Fluxes Across the Sediment–Water Interface of the Neckar River,Germany: In Situ Measurements and Simulations

A benthic in situ flume and a 1D biogeochemical sediment model to evaluate solute fluxes across the sediment–water interface have been developed. The flume was successfully used to determine oxygen and nutrient fluxes at various locations of the Neckar River in Germany. The experimental results were linked with vertical pore water concentration profiles and independently verified with the model. By combining experimental and model results we assessed the influence of dissolved oxygen concentrations in the water column and the availability of degradable organic matter on sediment oxygen demand. The results and the derived relations can be used to parameterize the sediment module of large scale water quality models, allowing one to assess the influence of sediment–water interactions on various aspects of river water quality. Moreover, the biogeochemical sediment model can help to improve the general understanding of the processes governing solute concentrations and fluxes in sediments and across their interfaces.     

防渗墙与帷幕墙防渗效果评价

为阻断某垃圾填埋场的甲烷气体向附近住宅区迁移的通道,防止甲烷气体给住宅区造成火灾爆炸灾害,在垃圾填埋场与住宅区之间修建了防渗墙和帷幕墙,并对其进行了跟踪监测.结果表明,防渗墙有效地阻隔了填埋场内甲烷气体向外迁移.     

污水处理厂消化沼气脱硫(H_2S)实验

污泥消化池每天产生大量的沼气,主要成分为甲烷。消化沼气是一种热值很高的可燃性气体,可用于驱动发电机发电。沼气中的H2S对设备的腐蚀性严重影响了有效的能源利用。除去沼气中含有的H2S可使发电机免遭腐蚀,还可以控制SO2的排放。本论文通过对PDS法应用于某污水处理厂消化沼气脱硫的研究与试验,证明了该方法的有效性及可行性。脱硫效率高达90%以上,平均脱硫效率为95%。脱硫后消化沼气中H2S的浓度均远远低于发动机对燃气中要求的H2S的浓度不得高于1150mgm3的标准,对下一步的工程设计及工艺改进具有指导性的意义。