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Denitrification kinetics and stoichiometry of a moving bed biofilm reactor using methanol as an external carbon source.

机译：使用甲醇作为外部碳源的移动床生物膜反应器的反硝化动力学和化学计量。

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摘要

Wastewater treatment facilities discharging into Chesapeake Bay are facing Limit of Technology (LOT) standards to reduce their nitrogen discharge to more stringent levels (3-4 mg/L as Total Nitrogen (TN)). The Moving Bed Biofilm Reactor (MBBR) technology was determined to be a viable option for denitrification to achieve total nitrogen of between 3-4 mg N/L and nitrate concentration below 1 mg N/L. In an attempt to explore an effective, affordable and applicable technological alternative that can help meet the criteria, DC Water and Sewer Authority (DC WASA) operated a pilot scale post-denitrifying MBBR process from January 2008 through June 2008 as a dentirifcation polishing step downstream of the existing nitrification and denitrification activated sludge system.;Ex-situ Bench scale kinetic evaluation of MBBR system using methanol as an external carbon was conducted on the media grown in the pilot reactor throughout the pilot period. The primary objective was to better understand the denitrification kinetics and to determine kinetic and stoichiometric parameters for nitrogen removal of such system. Mainly, four parameters: specific denitrification rate (SDNR), half saturation constants (Ks) of limited NOx-N and Chemical Oxygen Demand (COD) and biomass density were measured over a range of temperatures of four individual reactors namely T1R1, T1R2, T2R1 and T2R2 that resembled the small scale pilot reactors. Stoichiometric Carbon to Nitrogen (C/N) ratio was also estimated for this system using COD and NO3-N values of SDNR test.;Average SDN rate of reactors T1R1, T1R2, T2R1 and T2R2 was estimated as 1.67 g NOx-N/m2/d, 1.47 g NOx-N/m2/d, 1.50 g NOx-N/m2/d and 1.28 g NOx-N/m2/d respectively expressed in terms of total biofilm carrier area. The SDNR expressed as g/m 2/d exhibited very little relationship with temperature suggesting a resilience of the overall process to temperature changes. SDN rate expressed in terms of g NOx-N/g biomass/d were estimated as 0.07-0.18 for T1R1 at a temperature range of 12°C-20°C; 0.10-0.20 for T1R2 and 0.07-0.13 for T2R2 at a temperature range of 13°C-18o°C, and 0.07-0.12 for T2R1 at a temperature range of 12.5°C-20°C. The SDNR expressed as g NOx-N/g biomass-d was observed to decrease with decreasing temperature suggesting an Arrhenius relationship and the Arrhenius constant (theta) was calculated as 1.08 for a temperature range of 12°C - 20°C.;Similarly, stoichiometric COD/N ratio was estimated in the range of 4.6 mg/mg to 5.3 mg/mg, 4.4 mg/mg to 6.1 mg/mg, 4.3mg/mg to 6.3 mg/mg and 4.3 mg/mg to 5.9 mg/mg for T1R1, T1R2, T2R1 and T2R2 respectively. This range is similar to the range observed for denitrification in activated sludge suspended growth process.;A kinetic model was developed based on the non-linear Monod model and operated on a Microsoft Excel Platform to estimate Ks. The model predicted Ks values for limited NOx-N between 0.61-2.55 mg N/L and 0.64-2.60 mg N/L, and for limited COD between 6.3-12.7 mg/L and 4.4-12.3 mg/L for T1R1 and T1R2 reactors respectively. These values seemed insensitive to change in temperature with a weak relationship with biomass density. Biomass Density values ranged widely from 6-21.6 g/m2, 4.37-16.52 g/m2, 7.46-20.48 g/m2 and 5.39-17.65 g/m2 for T1R1, T1R2, T2R1 and T2R2 reactors respectively for a temperature range of 11°C-23.5°C. The test indicated increase in biomass density with decrease in temperature.;The findings of this study are useful for the treatment plants that are considering to upgrade their facility to meet the stringent nutrient discharge limit. However, the testing in this research was limited to methanol only. Study of MBBR system on carbon sources other than methanol could complement the application of this technology in other existing as well as new treatment plants that use different carbon source.
机译：排放到切萨皮克湾的废水处理设施正面临技术极限（LOT）标准，以将其氮排放降低到更严格的水平（以总氮（TN）计为3-4 mg / L）。经确定，移动床生物膜反应器（MBBR）技术可用于反硝化，以实现总氮含量在3-4 mg N / L和硝酸盐浓度低于1 mg N / L之间的可行选择。为了探索一种有效，负担得起且适用的技术替代方案，以帮助满足标准，DC水和污水处理局（DC WASA）从2008年1月至2008年6月进行了中试MBBR脱硝工艺，作为下游的脱硝抛光步骤。在整个试验期间，对在中试反应器中生长的介质进行了以甲醇为外来碳的MBBR系统的异位实验规模动力学评估。主要目的是更好地了解反硝化动力学，并确定用于脱氮的动力学和化学计量参数。主要在四个单独的反应器（即T1R1，T1R2，T2R1）的温度范围内测量了四个参数：特定反硝化率（SDNR），有限NOx-N的半饱和常数（Ks）以及化学需氧量（COD）和生物量密度。和T2R2类似小型中试反应堆。还使用SDNR测试的COD和NO3-N值估算了该系统的化学计量碳氮比（C / N）;;反应器T1R1，T1R2，T2R1和T2R2的平均SDN速率估计为1.67 g NOx-N / m2 / d，分别以总生物膜载体面积表示的1.47 g NOx-N / m2 / d，1.50 g NOx-N / m2 / d和1.28 g NOx-N / m2 / d。表示为g / m 2 / d的SDNR与温度的关系很小，表明整个过程对温度变化具有弹性。在12°C-20°C的温度范围内，T1R1的以g NOx-N / g生物量/ d表示的SDN速率估计为0.07-0.18；在13°C-18oC的温度范围内，T1R2为0.10-0.20，T2R2为0.07-0.13，在12.5°C-20°C范围内对于T2R1为0.07-0.12。观察到以g NOx-N / g生物量-d表示的SDNR随着温度的降低而降低，表明存在阿累尼乌斯关系，在12°C-20°C的温度范围内，阿累尼乌斯常数（θ）计算为1.08。化学计量的COD / N比估计为4.6 mg / mg至5.3 mg / mg，4.4 mg / mg至6.1 mg / mg，4.3 mg / mg至6.3 mg / mg和4.3 mg / mg至5.9 mg / mg分别用于T1R1，T1R2，T2R1和T2R2。该范围类似于活性污泥悬浮生长过程中反硝化作用的范围。基于非线性Monod模型开发了动力学模型，并在Microsoft Excel平台上运行以估算K​​s。该模型针对T1R1和T1R2反应堆的有限NOx-N在0.61-2.55 mg N / L和0.64-2.60 mg N / L之间以及有限COD在6.3-12.7 mg / L和4.4-12.3 mg / L之间的Ks值进行了预测分别。这些值似乎对温度变化不敏感，与生物量密度的关系很弱。 T1R1，T1R2，T2R1和T2R2反应器的生物质密度值分别在6-21.6 g / m2、4.37-16.52 g / m2、7.46-20.48 g / m2和5.39-17.65 g / m2之间变化，温度范围为11° C-23.5℃。该测试表明生物质密度随温度降低而增加。这项研究的结果对于正在考虑升级其设施以满足严格的养分排放极限的处理厂很有用。但是，这项研究中的测试仅限于甲醇。对除甲醇以外的碳源进行MBBR系统的研究可以补充该技术在其他现有的以及使用不同碳源的新处理厂中的应用。

著录项

  • 作者

    Shrestha, Arbina.;

  • 作者单位

    The George Washington University.;

  • 授予单位 The George Washington University.;
  • 学科 Engineering Environmental.
  • 学位 M.S.
  • 年度 2010
  • 页码 138 p.
  • 总页数 138
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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