新型铁盐脱氮除磷技术的基础研究

The pollution from nitrogenous and phosphorous compounds is the chief factor responsible for eutrophication of water body, and so its control has aroused great attention to the public. The nitrate-dependent anaerobic ferrous oxidation (NAFO) is an important discovery in the field of environmental science and microbiology, and several papers have been published in the top journals of Nature and Science. NAFO is a valuable bioreaction since it can convert nitrate into nitrogen gas and oxidize ferrous compounds into ferric compounds, leading to removal of nitrogen and phosphorus from wastewater. So far, however, little information is available about the conditions, characteristics, microorganisms and mechanisms of NAFO. The information is also deficient about phosphate removal with ferrous or ferric compounds. It is necessary to set up a project to get all the above-mentioned information. Such a project can offer an opportunity to look for the new microorganisms of NAFO and to make a contribution to microbiology. Such a project can offer an opportunity to create a novel biotechnology for simultaneous removal of nitrogen and phosphorus. Such a project can also offer an opportunity to reveal some new metabolic pathways for conversion of nitrogenous and phosphorous compounds, promoting the study of biogeochemical cycles.

氮磷污染是水体富营养化的主要诱因，氮磷污染控制已引起环境界的高度重视。以二价铁为电子供体、以硝酸盐（或亚硝酸盐）为电子受体的硝酸盐型厌氧铁氧化（NAFO）是环境领域和微生物领域的重大发现，已有多篇论文发表于世界顶级期刊《Nature》和《Science》上。NAFO蕴藏着巨大的开发价值，它不仅能将硝酸盐（或亚硝酸盐）转化成氮气，实现废水脱氮，而且能将二价铁转化成三价铁，强化废水除磷。但迄今为止，人们对NAFO的条件、特性、菌种和机理知之甚少，对传统铁盐除磷的认识也存在盲点。探明NAFO的适宜条件、转化特性、功能菌群和微生物学机理，搞清铁盐除磷的过程特性，将有助于耦合NAFO和铁盐除磷反应，研发新的废水生物脱氮除磷技术；有助于发现新的NAFO菌种，丰富微生物学内容；有助于揭示新的氮素循环和铁素循环环节，推进生物地球化学循环研究。

低C:N:P 废水治理是重要的环境问题，亟需开发自养脱氮除磷技术。硝酸盐型厌氧铁氧化（NAFO），能将硝酸盐转化成氮气，提供一种废水生物自养生物脱氮技术，且能将二价铁转化成三价铁，提供更经济高效的除磷沉淀剂。有鉴于此，本项目研发了新型铁盐脱氮技术和除磷技术，并以NAFO为纽带，开发新型铁盐脱氮除磷复合技术。主要结论如下：比选了NAFO菌的接种源，确定厌氧颗粒污泥和反硝化污泥为优质接种源；优化了富集NAFO菌的营养条件和环境条件，适宜Fe/N比为2.0、硝酸盐浓度为100-120 mg/L、温度为30℃、初始pH为8.0。检测了NAFO富集培养物的功能，最大比脱氮速率为4.68 mg-N/(L∙g-VSS∙h)、半饱和浓度为91.18 mg-N/L，半抑制浓度为1210.52 mg-N/L；具有良好的沉降性能和独特的形貌，含有较高的铁素；含有Rhodanobacter和Gallionella等典型NAFO菌属。分离了一株NAFO功能菌NF-1，该菌株属于Shewanella属，检测了其生理生化性能。采用上流式厌氧污泥床反应器成功运行NAFO生物脱氮工艺，装置容积负荷和容积去除率分别为0.161kg-N/(m3•d)和0.076kg-N/(m3•d)。研发了一种通过投加外源菌种强化NAFO生物脱氮过程的技术，硝氮去除速率可提高2.24倍，强化持续时间为43±2d。优化了铁盐除磷的主要工艺参数，并提出了“优先/联合”操作模式用于铁盐除磷工艺。揭示了传统铁盐除磷为偏衡反应的过程特征，解析了传统除磷工艺药剂投加量大的原因。自主研发了以分区强化混凝（PEC）除磷反应器为依托的强化铁盐除磷工艺，工艺可用于低、中、高浓度含磷废水处理，容积除磷速率达2.86kg-P/(m3•d)，磷去除率达97%以上，沉淀剂有效利用率高，单位处理成本低至$ 0.632-0.673/kg-P，优于同类研究。PEC反应器主要通过加速混凝过程和强化絮凝沉淀分离过程实现高效除磷。研发了新型铁钙盐复合除磷剂，Fe/Ca复合的优化比例为7:3-4:1，沉淀剂投加量可减少35.53%。NAFO污泥和工艺出水均具除磷效果，效能为18.46 mg-P/g-VS和3.42 kg-Fe/kg-P。研发了化学除磷耦合生物脱氮装置用于新型铁盐脱氮除磷复合工艺，NAFO生物脱氮是复合工艺的瓶颈环节，需进一步强化。