Optimization of plant-wide ammonia removal: bioaugmentation versus nitritation of centrate

美国第一个从消化污泥脱水液（浓缩液）中去除总氮的大型设备刚刚在温尼伯-北工厂投入使用。平行顺序间歇反应器（SBR）通过硝化（氨转化为硝酸盐）和反硝化（硝酸盐去除为氮气）实现1600公斤的氮去除。这笔拨款将全面解决利用SBR生产的生物质的潜力，利用在浓缩物硝化过程中产生的硝化细菌来增加主流高纯度氧活性污泥（HPOAS）反应器，以诱导HPOAS反应器中的硝化作用，并“免费”为整个工厂的氨负荷的额外减少做出贡献。在荷兰和捷克的植物中，生物增强试验取得了不同程度的成功，但仍有许多未知因素需要确定，例如：RAS返回的数量；SBR中WAS的产量；集中式SBR和HPOAS反应器的温差；反硝化在还原碱度中的作用有稀释、旁温控制的作用；HPOAS在澄清剂失效前提高自身SRT的能力。另一方面，总体氮的去除可以通过不完全氨氧化为亚硝酸盐（硝化）来完成，这只需要三分之二的氧气，通过反硝化可以节省三分之一的反硝化甲醇，从而也改善了碳足迹。后者需要改变SBR的拟议操作，以便使用更高的温度。随着温差的增大，生物增强效应会减弱。随着Winnipeg-North进一步升级到完全去除营养物质，CRD项目将在整个工厂的目标环境影响和相关能源和甲醇节约的背景下，研究这两种选择。计划的磷共沉淀应有助于保留HPOAS生物反应器中的硝化菌。结果可能会节省数百万美元的新建筑成本。全尺寸的结果和模拟将适用于加拿大的所有处理厂，以及任何需要消化污泥并要求工厂去除氮和磷的地方。

America's first large facility for total nitrogen removal from digested sludge dewatering liquor (centrate) has just been commissioned at the Winnipeg-North plant. Parallel sequencing batch reactors (SBR) achieve removal of 1600 kg of nitrogen through nitrification (ammonia conversion to nitrate) and denitrification (nitrate removal to nitrogen gas). The grant will address in full scale the potential of using the biomass produced in the SBR to augment the main stream high-purity oxygen activated sludge (HPOAS) reactors with nitrifying bacteria generated during nitrification of centrate in order to induce nitrification in the HPOAS reactors and contribute 'for free' to additional reduction of ammonia load in the whole plant. Bioaugmentation has been tried with mixed success in the Netherlands and Czech plants but there are a number of unknowns that need to be defined, e.g.: the amount of RAS returned; amounts of WAS produced in SBR; temperature differential between centrate SBR and HPOAS reactors; role of denitrification in restoring the alkalinity; role of dilution, beside temperature control; capacity of HPOAS to increase their own SRT before clarifiers fail. On the other hand the overall nitrogen removal can alternatively be accomplished using an incomplete ammonia oxidation to nitrite (nitritation) which uses only two-thirds of oxygen and by denitritation which saves a third of methanol used in denitrification, thus also improving the carbon footprint. The latter requires a change in the proposed operation of the SBR such that a higher temperature is used. Bioaugmentation effect will be reduced as the temperature differential is increased. The CRD project will examine both options in the whole plant, in the context of the target environmental effect of ammonia removal and associated energy and methanol saved, as Winnipeg-North is further upgraded to full nutrient removal. Planned phosphorus co-precipitation should help retain the nitrifiers in the HPOAS bioreactors. The results may save millions in new construction costs. The full scale results and simulation would be applicable to all treatment plants in Canada and wherever sludge is digested and the plant is required to remove nitrogen as well as phosphorus.