Effects of hot water extraction pretreatment on physicochemical changes of Douglas fir

Hot water extraction (HWE) is an autocatalytic pretreatment that can be effectively integrated into most of the conversion technologies for extracting hemicelluloses from woody biomass. The objective of this study was to understand the influence of pretreatment factors on removal of hemicelluloses from Douglas fir chips. Compositional change in biomass was analyzed with ion chromatography and further confirmed with Fourier transform infrared spectroscopy (FT-IR). Highest hemicellulose extraction yield (HEY) was estimated to be 67.44% at the optimum reaction time (79 min) and temperature (180 °C) by using response surface methodology (RSM). Experimental results show that the HEY increased from 19.29 to 70.81% depending on the reaction time (30–120 min) and the temperature (140–180 °C). Effects of the severity factor (SF) on the mass removal and compositional changes were also evaluated. Hygroscopicity and thermal stability of wood were improved after HWE pretreatment. Colorimetric analysis showed that temperature has a greater influence on color of the wood chips during HWE pretreatment than dwell time. HWE pretreatment shows great potential for extracting hemicelluloses and altering physicochemical properties of wood in an integrated biorefinery for diversification of product portfolio.     

Evolutionary learning of fuzzy models

This paper presents an evolutionary algorithm for generating knowledge bases for fuzzy logic systems. The algorithm dynamically adjusts the focus of the genetic search by dividing the population into three sub-groups, each concerned with a different level of knowledge base optimisation. The algorithm was tested on the identification of two highly non-linear simulated plants. Such a task represents a challenging test for any learning technique and involves two opposite requirements, the exploration of a large high-dimensional search space and the achievement of the best modelling accuracy. The algorithm achieved learning results that compared favourably with those for alternative knowledge base generation methods.     

Improved biogas yield from organic fraction of municipal solid waste as preliminary step for fuel cell technology and hydrogen generation

Biogas utilization in fuel cell technology and hydrogen generation is a modern and economically viable approach. A pretreatment step prior to anaerobic digestion (AD) is obligatory to increase the hydrolysis, solubilize the complex matter present in organic fraction of municipal solid waste (OFMSW) and to achieve higher yield of biogas. This study was intended to find out the effects of thermal, chemical and thermochemical pretreatments on the properties and structure of OFMSW and also on biogas production. There was an increase in chemical oxygen demand of 6.87, 1.61 and 11.60% for thermal, chemical and thermochemical pretreatments, respectively. Also, the content of volatile solids was reduced by 2.36% by thermochemical pretreatment. FTIR, XRD and SEM analysis revealed that these pretreatments also caused chemical and morphological changes on the substrate, as a result reduced its crystallinity and enhanced the rate of hydrolysis. A significant increase of 54% in biogas yield was achieved after thermochemical pretreatment in comparison to untreated OFMSW sample.     

采用层次分析法(AHP)优选生活垃圾综合处理物流模式

以北京市南城地区生活垃圾收集和处理处置为研究对象,以原生垃圾直接填埋作为对照,运用层次分析法对混合收集(原筛分工艺、筛分工艺改进和筛分工艺优化)和分类收集共5种生活垃圾处理处置物流模式进行综合比较,从经济和技术两方面探讨符合南城地区垃圾综合处理的物流模式。结果表明,完全垃圾填埋的物流模式最差,分类条件下的物流模式最优,40mm和80mm筛分的物流模式可以作为南城地区生活垃圾处理处置的过渡方案。     

Acute toxicities of five nitromusk compounds in Daphnia,algae and photoluminescent bacteria

Acute toxicities of five nitromusk compounds in Daphnia, algae and photoluminescent bacteria were investigated. In order to obtain some basic data for ecotoxicological tests, physicochemical parameters were determined. The water solubility and log K_ow values were: nitromusk xylene 0.15 mg l⁻¹ and 4.4, nitromusk ketone 0.46 mg l⁻¹ and 3.8, nitromusk ambrette 0.79 mg l⁻¹ and 4.0, nitromusk moskene 0.046 mg l⁻¹ and 4.4 and nitromusk tibetene 0.052 mg l⁻¹ and 4.3. None of these compounds exhibited a toxic effect in any of the toxicity tests even at the highest concentrations achievable except for nitromusk ambrette which was toxic to Daphnia.     

餐厨垃圾高效好氧堆肥过程参数的影响因素研究

为了考察环境温度、初始含水率、通风量和填料量等因素对餐厨垃圾堆肥进程的影响,分别选用3组卧式反应器进行了4因素3水平完全试验和正交试验,对堆料温度、水溶性COD和pH值等餐厨垃圾好氧堆肥过程参数在不同条件下的变化规律进行了研究.结果表明：环境温度、通风量、初始含水率和填料量等不同影响因素对餐厨垃圾好氧堆肥过程均具有显著影响.环境温度、通风量、含水率和填料量等4因素对堆肥减量化率的影响显著性顺序为含水率〉环境温度〉填料量〉通风量.     

Membrane bioreactor technology for wastewater treatment and reuse

Treatment technology for water recycling encompasses a vast number of options. Membrane processes are regarded as key elements of advanced wastewater reclamation and reuse schemes and are included in a number of prominent schemes world-wide, e.g. for artificial groundwater recharge, indirect potable reuse as well as for industrial process water production. Membrane bioreactors (MBRs) are a promising process combination of activated sludge treatment and membrane filtration for biomass retention. This paper will provide an overview of the status of membrane bioreactor applications in municipal wastewater reclamation and reuse in Europe and will depict their potential role in promoting more sustainable water use patterns. Particular attention will be paid to the impact of MBR technology on emerging pollutants. A case study will be presented on a full-scale MBR plant for municipal wastewater which is operated by Aquafin in Belgium.     

高喷注浆技术在地下水污染防渗中的应用

为了隔断垃圾填埋场与外部地层的水力联系并消除渗滤液对地下水的污染,采用高喷注浆技术建造人工隔水帷幕和隔水层,并对这种技术进行室内与现场试验,结果表明将注浆技术应用在垃圾填埋场可以达到防渗目的,消除了垃圾填埋对地下水的影响,其封水效果可以满足填埋场的防渗要求.     

Co-pyrolysis characteristics and product distributions of municipal solid waste and corn stalk

To investigate synergetic effects on pyrolysis of municipal solid waste and corn stalk, pyrolysis characteristics and product distributions of their mixtures were examined by thermal gravimetric and fixed-bed. Results indicated that co-pyrolysis process can be divided into four steps: losing water, main pyrolysis, carbonization and catalytic gasification of char. Under different blending ratio conditions, char and liquid yields were lower than the theoretical values calculated on pyrolysis of each individual sample, and consequently, gas yields were higher. Linear relationship can be applied to char and liquid products, however, hardly applied to gas yields.     

低负荷下厌氧氨氧化处理养殖废水的启动研究

厌氧氨氧化作为新型生物脱氮技术其关键在于如何实现厌氧氨氧化反应的启动,现有研究多以模拟废水为研究对象,本文以猪场废水为对象的研究,利用ASBR为反应器,接种反硝化污泥培养厌氧氨氧化细菌,在NH+4-N与NO-2-N浓度均为100 mg/L的条件下,运行125 d,经历启动初期、过渡期、系统稳定运行期三个阶段,厌氧氨氧化反应器中NH+4-N的去除率达91.70%,NO-2-N去除率92.0%;NH+4-N的容积负荷为36.90 mg/L.d,NO-2-N的容积负荷为37.55 mg/(L.d),成功实现了厌氧氨氧化反应器的启动。该研究成果对厌氧氨氧化技术在工程实践的应用具有重要的指导意义。