Development and simulation studies of an unsteady state biofilter model for the treatment of cyclic air emissions of an α‐pinene gas stream

This paper describes the development and simulation of an unsteady state biofilter model used to predict dynamic behaviour of cyclically‐operated biofilters and compares it with experimental results obtained from three, parallel, bench‐scale biofilters treating both periodically fluctuating concentrations and constant concentrations of an α‐pinene‐laden gas stream. The dynamic model, using kinetic parameters estimated from the constant concentration biofilter, was able to predict the performance of cyclic biofilters operating at short cycle periods (ie, in the order of minutes and hours). Steady state kinetic data from a constant concentration biofilter can be used to predict unsteady state biofilter operation. At a 24 h cycle period, the dynamic model compared well with experimental results. For long cycle periods (ie, hours and days), removal efficiency decreased after periods of non‐loading: the longer the period of non‐loading, the poorer the biofilter's performance at the re‐commencement of pollutant loading. At longer time scales the model did not effectively predict transient behaviour, as adsorption and changes in kinetic parameters were not accounted for. Modelling results showed that similar biofiltration performance for the cyclic and constant concentration biofiltration of α‐pinene is expected for biofilters operating solely in the first order kinetics regime. Poorer performance for cyclic biofilters following Monod kinetics spanning the entire kinetics range is expected as the cycle amplitude increases. The most important parameters affecting the performance of a cyclically‐operated biofilter with short cycle periods are: amplitude of cyclic fluctuations, C_{g, max}/C_g, relative value of the half‐saturation constant in the Monod expression, K_s, and effective diffusivity of α‐pinene in the biofilm, D_e. Copyright © 2005 Society of Chemical Industry     

卷烟企业异味对大气环境的影响分析

云南某卷烟厂制丝、卷接包及香料厨房生产过程中产生非常浓烈的异味,异味主要为有机高分子碳氢化合物,还含有少量低分子有机碳氢化合物和微量的氨气.通过公众参与调查和模式预测,判定其影响范围在下风向650 m以内.项目处于某城市建成区,由于项目周围学校、居民区等敏感点众多,因此,为减轻该厂生产过程中排放的异味对周围环境的影响,该厂要么尽快搬迁,要么根据项目异味气体的特征,采取生物滤池或化学洗池等对异味进行治理,并针对有挡雨帽和无挡雨帽排气筒两种情况分别提出了异味的最低去除效率.     

生物滤料滤池处理姚江微污染水源水

通过中试试验,考察了不同滤料介质的生物滤池对于姚江微污染水源水的处理效果。结果表明,双层生物滤料滤池能够有效地去除有机物、氨氮等污染物质,可以延长滤池反冲洗周期,并能在短时间内恢复到正常处理能力,适合于传统滤池的改造。采用颗粒活性炭-石英砂滤料滤池的综合处理效果优于同类型的颗粒活性炭-沸石滤料滤池,通过加入少量臭氧(0.8～1.0mg/L)可以提高生物滤池的去除效果。     

有氧条件下生物过滤法脱氮研究

采用生物过滤法,以醋酸钠为外加碳源,探讨了有氧条件下反硝化脱氮的可行性。研究表明,通过向配制水中通入由N2 O2组成的合成气体,能方便地控制水体中溶解氧的浓度。在向配制水中通入含有少量O2的合成气后,系统中的溶解氧浓度下降比不通任何气体时下降还快。随着溶解氧含量逐渐提升,系统反硝化脱氮效果并未受到明显影响。当溶解氧达到6.4mg/L时,系统仍然具有反硝化作用,只是硝酸盐浓度下降速度比低溶解氧条件下缓慢,但是脱氮效率仍然可达85%左右。结果显示,采用生物过滤系统以及实验室培养得到的两种微生物,在一定溶解氧条件下,溶解氧对系统反硝化脱氮能力影响有限。     

污泥臭氧减量对淹没式生物膜工艺运行效能的影响

针对淹没生物膜法(SBF)和污泥臭氧化各自在污泥减量方面的优点,提出了化学臭氧化和复合生物膜法相结合的污泥减量工艺,并对臭氧化对SBF运行效能的影响进行了实验研究。通过2个并行的SBF系统污泥臭氧化结果进行对比,结果显示臭氧化能够显著降低系统的污泥产率(0.043 kg/kg,较不加臭氧化的SBF系统下降了76%),同时不对硝化和有机物的去除作用产生明显的影响,系统出水水质良好。     

常温低氨氮污水生物滤池部分亚硝化的实现

采用火山岩活性生物陶粒滤料反应器,在常温(8～25℃)、低ρ(NH4+-N)(60～90 mg/L)条件下,通过控制曝气,实现了NO2--N的积累,系统启动后NO2--N的累积率大于80%.结果表明:DO控制是实现亚硝化的主要途径,而游离氨(FA)抑制可作为优选氨氧化细菌(AOB)的辅助途径,水力停留时间(HRT)的调整是控制亚硝化比例的主要手段;间歇运行条件下,ρ(NH4+-N)、ρ(NO2--N)和ρ(NO3--N)的变化均具有零级反应动力学特征,且NH4+-N的转化速率为4.32 mg/(L.h),NO2--N与NO3--N的积累速率分别为3.05、0.40 mg/(L.h),根据此规律,将实现部分亚硝化的HRT确定为9～14 h.     

生物滤池去除污水处理厂臭气的应用研究

研制了一套生物过滤系统,用于处理污水处理厂生化水解池所排放的臭气。以某污水处理厂的生物滤池为研究对象,经过调试使用后,在进口段气体中H2S、NH3的质量浓度分别小于7.0、90.0 mg/m3时,其去除率分别达到90%和99%左右。并通过试验分析了运行时间、进气浓度、填料含水率、温度对除臭效率的影响。     

Comparison of biological reactors (biofilter,biotrickling filter and modified RBC) for treating dichloromethane vapors

BACKGROUND: Bioreactors used for waste gas and odor treatment have gained acceptance in recent years to treat volatile organic compounds (VOCs). Different types of bioreactors (biofilter, biotrickling filter and rotating biological reactor) have been used for waste gas treatment. Most studies reported in the literature have used one of these systems to treat several types of inorganic and organic gases either individually or in mixtures. Each of these reactors has some advantages and some limitations. Though biodegradation is the main process for the removal of pollutants, the mechanisms of removal and the microbial communities may differ among these bioreactors. Consequently their performance or removal efficiency may also be different. RESULTS: At low loading rate (<35 g m^?3 h^?1), all three bioreactors showed comparable removal efficiencies and elimination capacity, but at higher loading rates, rotating biological contactors (RBC) showed a better performance with higher removal efficiency (40–50%) than both the biofilter and biotrickling filter (20–40%). The biofilter showed a sharp drop in removal efficiency and elimination capacity at high loading rates. CONCLUSIONS: The modified RBC had no clogging problems and no increase in pressure drop when compared with the other bioreactors. It can thus handle pollutant load for a longer period of time. This is the first study attempting to compare the performance of three different bioreactors for removal of the same VOC under different conditions. Copyright © 2010 Society of Chemical Industry     

Effect of packed structure on flow behaviour in a trickle bed biofilter

The effects of operation conditions on the flow behaviour in gas–liquid countercurrent trickle bed biofilter were experimentally examined. In order to prevent gas channelling in the biofilter, packings with a relatively large void fraction, which have a role to maintain a high void fraction in the bed, were added. The gas and liquid velocities of the packed structure and the packings were changed, and the residence time distributions (RTDs) of the gas and liquid were measured. It was found that the addition of void supporters was very effective in the suppression of gas channelling.