SFBR中好氧颗粒污泥的培养及特性研究

接种自行培养的活性污泥,以模拟废水为基质,采用连续进水、间歇出水及厌氧/好氧交替的运行模式,尝试了在SFBR中进行好氧颗粒污泥的培养,并研究了好氧颗粒污泥的特性及反应器对污染物的去除效果.结果表明,通过逐步缩短沉降时间,28 d时成功培养出好氧颗粒污泥,所形成的好氧颗粒污泥呈黄色、形状不规则,且粒径较小(平均粒径0.56 mm),正常情况下的SVI保持在70 mL·g-1以下,EPS在59 d时达到最大值(以MLVSS计)373.24 mg·g-1,较培养初期增加了约2.5倍,运行后期由于颗粒出现解体,导致EPS急剧下降;反应器在运行过程中未能保持较高的污泥量,中后期MLSS始终在3 000mg·L-1以下;在63 d的运行时间里,除异常波动外,反应器对COD的去除率基本维持在90%左右,正常情况下出水COD小于100 mg·L-1,反应器对NH+4-N、TIN的去除效果波动较大,去除率分别为44.45%~94.72%及43.87%~93.13%,反应器对TP的去除率在44.50%~97.40%之间,正常情况下TP去除率可维持在60%以上;限于自动控制水平,夜间长时间的好氧饥饿期容易造成丝状菌过度生长,使得AGS在生长竞争中处于劣势,最终导致了AGS的解体.     

不同培养方式下兽疫链球菌发酵生产透明质酸的研究

对摇瓶的分批和补料、小罐的分批和流加发酵生产透明质酸（ＨＡ） 进行了比较研究,并对发酵机制进行了初步的探讨．在耗糖量相同的情况下,分批发酵比多次加料或流加发酵具有更高的ＨＡ产量和转化率;分批发酵初糖７％ ,发酵２４ ｈ 左右,产ＨＡ３．６ ｇ／Ｌ,转化率５．３ ％ ,流加发酵初糖３％ ,１５ ｈ 耗糖７％ ,此时,ＨＡ 为３ ．０ ｇ／Ｌ,转化率Ｙｐ／ｓ４．２％ ,继续发酵至２０ ｈ ,产ＨＡ４ ．０％ ,此时转化率Ｙｐ／ｓ３ ．６％ ,两种发酵所产ＨＡ 的Ｍｒ 均为２ ．０×１０６ ． 分批发酵中ＨＡ、副产物乳酸都和菌体生长相偶联,流加发酵中乳酸和菌体生长是偶联的,其含量均不断增加,ＨＡ含量表现为在菌体生长前期与之偶联,而后下降．流加发酵的菌体比生长速率远高于分批发酵．     

有机废水厌氧酸化和聚羟基烷酸生产组合系统的研究

以３０ｇ／Ｌ葡萄糖合成废水为原料,研究了厌氧酸化的操作温度（θ）对酸化率的影响,确定了达到最佳酸化产物分布时的ｐＨ值,并以酸化反应器的出水为碳源,在５Ｌ发酵罐上进行了分批和流加发酵实验．结果表明,θ＝４０℃时,废水的酸化率接近１００％;控制ｐＨ５．７,停留时间１０ｈ可使丁酸占ＵＡＳＢ反应器出水中总酸质量的６８％;与分批发酵相比,流加发酵法可大幅度地提高ＰＨＡ的产量,发酵５４ｈ后,ＤＣＷ和ＰＨＡ的质量浓度可分别达到１５．８ｇ／Ｌ和１０ｇ／Ｌ．     

长江中游盆地地质环境系统演变与防治对策

在构造沉降,泥沙淤积及人工围的相互的相互作用下,长江中游盆地质环境系统分割为演变化方向不同的两部分,堤外水域成为人工过饱盆地,堤内垸地成人为人工饥饿盆地。,长江某些区段及洞庭湖 水位抬升,垸地高程不断降低,洪涝渍害不断加剧。     

基质初始浓度对SFBR工艺去除营养物的影响

采用序半连续反应器就新鲜废水中COD/N比对COD、氮化合物去除效率和微生物生长的影响进行了研究。结果表明,新鲜废水中的COD/N比对COD和总氮去除率有明显的影响。当COD/N比由2.5增至12.5时,COD去除率由44.0%增至75.8%,总氮去除率从63.4%增至99.8%,然而,加料废水中COD/N比对微生物生长没有明显的影响。用一组涉及多个微生物反应的动力学模型,分析了COD/N比对同时去除碳、氮化合物效率和微生物生长的影响。     

不同碳源下的间歇曝气反硝化实验研究

本实验研究在序批式模式下高浓度硝酸盐的反硝化,比较用甲醇、醋酸钠和消化污泥上清液作碳源。实验发现,间歇曝气有助于提高反硝化污泥的沉降性能,而厌氧条件下,污泥的沉降性能差。污泥浓度4~5gVSS/L下,3种碳源都能有效地进行反硝化。最大硝酸盐去除率为0486gNO3N/gVSS·d。开始阶段,亚硝酸盐浓度增加,但用醋酸盐和硝化污泥上清液作碳源,其浓度最终下降为零。     

Effect of high-voltage direct current link on small signal stability of a power system with different penetration level of doubly fed induction generator and direct drive synchronous generator based wind farms

High penetration level of wind power has significant impact on the dynamic performance of power system. Power system with existing high-voltage direct current (HVDC) link may influence the stability of power system at high penetration level of wind power. This article investigates the stability issues of power system with existing HVDC link for different penetration level of doubly fed induction generator (DFIG) and direct drive synchronous generator (DDSG) based wind farms. The small signal stability analysis shows that power system with HVDC link has improved the stability of the power system for increased penetration of DFIG- and DDSG-based wind farms.     

Alternative low-cost process for large-scale production of Bacillus thuringiensis in a simple and novel culture system

Abstract

An industrial-scale, profitable method for production of the most widely used bioinsecticide, Bacillus thuringiensis (Bt), is challenging because of its widespread application. The aim of this study is to present a strategy to develop a low-cost, large-scale bioprocess to produce Bt H14.

This study was first focused on the design of a culture medium composed of economical and available components, such as glycerol and lysed Saccharomyces cerevisiae. The production goal of 1200 ITU was achieved using a medium composed of 20:20 g L^?1of glycerol:lysed yeast in batch cultures. Efforts were subsequently focused on the design of an appropriate culture system, and an original two-stage culture system was proposed. First, yeast (the primary component of the culture medium) are cultivated using a minimal mineral medium and lysed, and in the second stage, Bt is cultivated in the same bioreactor using the lysed yeasts as culture medium (supplemented with a feeding pulse of 10 g L^?1 glycerol). This system was called fed batch one pot (FOP). A new inoculation strategy is also presented in this study, since these Bt cultures were inoculated directly with heat pre-treated spores instead of vegetative bacteria to facilitate the bioprocess. This study was developed from the laboratory to production-scale bioreactors (measuring from 500 mL to 2500 L), and the efficiency of the proposed strategy was evident in LD₅₀ tests results, achieving 1796 ITU in large-scale processes. Both the use of non-conventional sources and the process development for biomass production are important for cost-effective production of Bt-based insecticides in mosquito control projects.     

A review on transient stability of DFIG integrated power system

With the increasing penetration of doubly fed induction generators (DFIGs), the impact of the DFIG on transient stability attracts great attention. Transient stability is largely dominated by generator types in the power system, and the dynamic characteristics of DFIG wind turbines are different from that of the synchronous generators in the conventional power plants. The analysis of the transient stability on DFIG integrated power systems has become a very important issue. This paper reviews the current research on the issue from two aspects. One is to describe the methods to improve the fault ride through capability of DFIG wind turbines and the other is to analyse the impact of the DFIG wind farm on transient stability of power systems.     

Design and analysis of artificial bee-colony-based MPPT algorithm for DFIG-based wind energy conversion systems

In this article, the proposed maximum power point tracking (MPPT) method is designed by taking rotor speed as an optimization problem, which is solved by artificial bee colony (ABC) algorithm to generate the maximum power output. The main advantage of this algorithm is that its optimal solution is independent of the initial positions and requirement of lesser number of control parameters, which leads to simple and robust MPPT algorithm than other algorithm. Furthermore, the hill climb search and particle swarm optimization-based MPPT algorithm are also discussed and the results obtained by these are compared to verify the effectiveness of proposed algorithm. Simulations for MPPT control along with doubly fed induction-generator-based wind energy conversion system is carried out in MATLAB/Simulink environment. Three statistical methods are used to evaluate the accuracy of each MPPT algorithm. All results are analyzed and compared under randomly selected wind as well as real wind speed configuration. Comparison of both numerical and simulation results under two different varying wind speed conditions strongly suggest that the proposed ABC-based MPPT algorithm is superior than other two MPPT algorithms.