垂直潜流人工湿地污水处理特性

垂直潜流人工湿地是一种新型的污水处理技术,在城镇污水资源化中有良好的实用价值和应用前景。通过对特征污染物即有机物、氮和磷的去除研究,阐述了污染物去除的基本特征和作用机理。湿地负荷8.1￣27 g[COD]/(m2.d)范围内,COD去除率为71%￣87%。垂直潜流人工湿地不利于大气复氧,并因而造成NH3-N去除率较低,平均去除率小于10%。TP去除率受温度和季节等因素影响较小,去除率为52%￣77%,但土壤pH值和溶解氧含量却制约着磷的吸附和沉淀作用。并介绍了各运行参数对COD、NH3-N和TP的去除效果的影响规律。     

用CFD研究潜流人工湿地集水区对其水力学性能的影响

采用计算流体力学（CFD）软件Fluent（Fluent Inc. ,Version 6. 2. 16）中的多孔介质模型对潜流人工湿地进行了模拟,并引入颗粒轨道模型讨论了潜流人工湿地层式和护管式两种集水区结构对其水力学性能的影响。模拟结果表明,在考察条件下,平均停留时间相差不大,散度成为人工湿地水力学效能的主要影响因素。集水区为层式结构时,净化区与集水区阻力比越小,其变化对湿地水力学效能影响越大;集水区高度增加,水流散度增大,湿地水力学效能减小。集水区为护管式结构时,减小集水区宽度有利于提高湿地水力学效能和明显减小阻力比对湿地水力学效能的影响;集水区高度的增加对湿地水力学效能影响不大。与层式集水区结构相比,护管式集水区结构的潜流人工湿地水力学效能更高,而且可以通过减小集水区宽度显著提高湿地水力学效能和逐步减小阻力比对其水力学效能的影响,因此护管式集水区结构优于层式结构。     

不同进水碳氮比对水平潜流人工湿地脱氮效果的影响

在不同条件下对3种湿地植物枯落物进行水解,以获得相应的植物碳源。利用提取的植物碳源,研究了进水碳氮比对水平潜流人工湿地脱氮效果的影响。结果表明,对以硝态氮为氮源的反硝化过程,补充碳源对硝态氮和总氮的去除有明显的促进作用;对以氨氮和硝态氮为氮源的脱氮过程,随碳氮比的升高,硝态氮和总氮去除率增大,而氨氮由于受到溶解氧的制约,其去除率下降,并最终制约了总氮去除率的增大程度。     

水平潜流和组合人工湿地水处理研究进展

应用广泛的水平潜流人工湿地系统对有机物和悬浮物有较高的去除率,但是对营养盐的去除率是较低的,因此各种类型的湿地被组合起来以提高去除效果。文章总结了近年来国内外水平潜流湿地及组合人工湿地系统的研究现状和问题,探讨了污水在人工湿地系统中的净化机理及影响因素,并预测其研究与应用发展的趋势,为人工湿地污水净化技术的应用研究提供了有益的参考。     

水平潜流人工湿地的脱氮机理及其影响因素研究

水平潜流人工湿地中氮的去除方式主要包括植物吸收、基质吸附和硝化-反硝化作用等,其中硝化-反硝化作用是其最主要的脱氮机理。水平潜流人工湿地的构造决定了其内部整体厌氧的环境,使其具有较好的反硝化脱氮效果。影响水平潜流人工湿地脱氮的主要因素包括溶解氧、基质、植物、碳源及运行条件等。探讨了影响湿地脱氮的主要因素,同时论述了提高湿地脱氮效果的措施,并对今后的相关研究方向进行了展望。     

景观型与蔬菜型水平潜流湿地除磷动力学模型

利用景观型和蔬菜型水平潜流湿地净化经生化处理后的生活污水尾水,进行湿地除磷动力学模型研究。对比分析不同湿地单元的除磷效率。为优化湿地除磷设计,采用一级动力学模型和Monod模型模拟除磷效果,对比模拟准确性,讨论水温、水力负荷与模型反应速率常数间关系,并建立湿地除磷模型构建式。结果表明,景观型湿地除磷能力顺序:美人蕉单元>再力花单元>鸢尾单元,蔬菜型湿地:空心菜单元>茭白单元>番茄单元,除磷效果差异归因于不同类植物的生物量区别。Monod模型(模型效率值ME:0.76～0.86)对湿地除磷的预测较一级动力学模型(ME:0.53～0.72)具有更高准确性。总磷面积去除率随水温的降低而减小,Arrhenius拟合结果表明,美人蕉(θ=1.006)、再力花(θ=1.008)和空心菜(θ=1.006)单元K_max对水温变化不敏感,水温对鸢尾(θ=1.015)和茭白(θ=1.014)单元除磷效率有较大影响。K_max20与水力负荷间存在显著正相关性,两者符合乘幂方程(R²:0.657;0.805)关系。考虑了水温和水力负荷因素的Monod模型构建式,对试验湿地除磷预测具备准确性。     

水力停留时间对双循环厌氧反应器处理中药废水污泥特性的影响

研究了不同水力停留时间(HRT,24 h、18 h、15 h、12 h)对双循环(DC)厌氧反应器处理中药废水效能的影响,并对颗粒污泥的粒径分布(PSD)、胞外聚合物(EPS)、微生物群落等变化情况进行了分析。结果表明,HRT由24 h缩短为12 h后,DC厌氧反应器对COD的去除率仍在90%以上。虽然出水中乙酸含量升高到339.69 mg·L^-1,但未造成VFA的过度累积;出水中辅酶的荧光吸收峰有所降低,而类腐殖酸与类富里酸的吸收峰增强,不适宜再继续降低HRT。随着HRT的缩短,颗粒污泥的EPS总量、蛋白含量、多糖含量均降低,其中酪氨酸对于保持污泥的稳定性发挥着重要作用。而磷脂脂肪酸分析(PLFA)表明,HRT缩短对于DC厌氧反应器第2反应区内微生物群落分布影响显著,革兰阳性菌由原来占总脂肪酸生物量的44.24%下降到32.69%,而革兰阴性菌由32.69%增大到38.66%。     

水力停留时间对生物膜/颗粒污泥耦合工艺脱氮除磷的影响

采用自主设计的悬浮载体生物膜/颗粒污泥耦合装置,利用硝化菌载体生物膜和反硝化聚磷菌颗粒污泥,研究水力停留时间对生物膜/颗粒污泥耦合工艺脱氮除磷的影响,得出最佳工艺参数。试验考查水力停留时间分别为6 h、7 h、8.5 h和10.5 h,结果表明,当水力停留时间为8.5 h时,系统的COD去除率为91.26%,氨氮和总氮的去除率分别为80.68%和70.58%,厌氧释磷速率也较稳定,为0.47 mg P·（g SS）^-1·h^-1,厌氧释磷速率最高,其碳源利用率最大,反硝化除磷效率最稳定,PO₄^3--P去除率为76.50%,反硝化除磷效率为1.04 mg P·（mg NO₃^--N）^-1,所以当水力停留时间为8.5 h时,系统具有较高的脱氮除磷效率。当水力停留时间过短时,氮磷的去除不完全,过长时,系统不稳定,系统的最优水力停留时间为8.5 h。     

Monitoring milk fat fractionation: Effect of agitation, temperature, and residence time on physical properties

With the use of two central composite designs, the effects of agitation rate, fractionation temperature, and residence time on the thermal properties of the stearin and olein milk fat fractions were investigated. The main function of agitation during fat fractionation was suspending the crystal aggregates and enhancing the heat transfer. For the experimental conditions described here, crystal aggregation did not seem to be affected by agitation. The effect of fractionation temperature on the physical properties of the olein fraction was very significant. Triangle diagrams were shown to be a useful tool for monitoring and designing fractionation processes. They illustrate that oleins with similar melting properties can be produced over a range of yields of stearin, which is important from an industrial point of view. Crystallizer residence time, which influences production costs, clearly affects both stearin yield and olein melting properties. For any fractionation temperature, stearin fractions with virtually identical melting properties and yields can be obtained over a range of olein melting properties. Manipulation of both the fractionation temperature and residence time allows the fractionation process to be adapted to meet changing market demands for fractions with different melting properties.     

Hydroliquefaction of Victorian brown coal in a continuous reactor: 1. Effects of residence time,temperature and catalysts on conversion

Slurries of two, closely related, Victorian brown coal samples in tetralin (1:3) were reacted with hydrogen in a continuous reactor system both with and without the addition of iron and iron-tin-based catalysts. The conversion to liquid products was greater when the catalysts were ion-exchanged onto the coal rather than being added as powders and the previously observed trend of iron/tin giving greater conversion than iron was exhibited. Increased temperature and residence time increased the oil yield.     

Study of geometry and operational conditions on mixing time, gas hold up, mass transfer, flow regime and biomass production from natural gas in a horizontal tubular loop bioreactor

A horizontal tubular loop bioreactor (HTLB) was used for production of biomass from natural gas. Hydrodynamic characterizations (mixing time and gas hold up) and mass transfer coefficients were considered in the HTLB (L=2.2 m, H=0.4 m and D=0.03 m) as functions of design parameters, i.e., horizontal length to diameter ratio (L/D) and volume of gas-liquid separator (S) as well as operational parameters, i.e., superficial gas and liquid velocities (U_sG, U_sL). In addition, flow regime in different gas and liquid flow rates was investigated. It was observed from experimental results that U_sL has remarkable effects on gas hold up and k_La due to its influence on mixing time. The volumetric mass transfer coefficients for oxygen (k_La_O2) and methane (k_La_CH4) were determined at different geometrical and operational factors. In average, the amount of oxygen consumption for metabolism is approximately 1.4 times higher than that of methane. In bubble flow regime, the HTLB was used for biomass production, too. A gas mixture of 50% methane and 50% oxygen (based on results of dry cell weight, optical density and doubling time) was the best gas mixture inlet for biomass production. The empirical correlations for mixing time, gas hold up and k_La in terms of U_sG, U_sL, L/D and volume of gas-liquid separator were obtained and expressed separately.