垃圾焚烧沥滤液生物处理高效产氧化亚氮调控机制与优化运行研究

Nitrous oxide, a typical greenhouse gas, is frequently generated during wastewater biological treatment processes and then discharged into the atmosphere. Recent studies have shown that nitrous oxide can also serve as a clean energy source. Therefore, techniques that enhance nitrous oxide production during the water denitrification process should allow the recovery of more energy. Fresh leachate from municipal solid waste incineration plants has high chemical oxygen demand (COD) and high concentrations of nitrogen in the form of ammonia even after anaerobic methanogenic treatment. Further treatment for nitrogen removal is required. In order to improve the nitrous oxide conversion rate, attempts will be made to identify the impact factors for nitrous oxide emission and microbial community structure, as well as the expression of functional genes involved in formation of nitrous oxide during a short-cut nitrification and denitrification treatment process. Molecular characterization of dominant ammonia-oxidizing bacteria (AOB), nitrite oxidizing and denitrifying bacteria will be conducted and attempts will be made to obtain these microorganisms in pure culture. Genetic approaches will also be used to enhance the denitrification process. nosZ deletion mutant(s) of both isolated and typical denitrifying bacteria (e.g. Pseudomonas stutzeri) will be constructed by genetic engineering techniques. The isolated AOB strain(s) and nosZ deletion mutant(s) will then immobilized by supporting materials and added into the nitrification unit and denitrification unit, respectively. The purpose of this project is to more fully understand how to enhance formation of nitrous oxide and achieve high yields of nitrous oxide formed during the incineration treatment process, which will reveal an important scientific significance and potential application value of the resources from incineration leachate.

氧化亚氮（N2O）作为一种典型温室气体，往往在实际废水的生物脱氮处理过程中产生并排放到环境空气中。近年来研究发现，N2O同时也是一种高效能源气体，如果能在废水的生物脱氮工艺中高效产生并收集，可进一步提高废水的能源利用。本申请项目根据垃圾焚烧沥滤液经厌氧生物处理后仍含高COD和高氨氮的特点，拟采用短程硝化反硝化工艺进一步处理，研究确定短程硝化反硝化系统中影响N2O转化的因子、微生物群落及与氮素转化相关的功能基因。通过纯菌筛选获得高活性氨氧化菌，通过基因工程技术构建NosZ基因缺失的反硝化菌(反硝化终产物为N2O)，对它们进行固定后投回脱氮系统，进而优化系统的菌群结构，实现在处理垃圾焚烧沥滤液短程硝化反硝化系统中稳定运行和氨氮高效转化为N2O，对于实现垃圾焚烧沥滤液的能源化具有重要科学意义和潜在应用价值。

垃圾焚烧沥滤液具有高氨氮的特点，在其生物脱氮过程中将这些氮元素转化为N2O可以实现废水的能源化利用。首先研究了垃圾焚烧沥滤液生物处理短程硝化段的影响因子，确定实现短程硝化快速高效启动的条件是控制游离氨（FA）浓度在5.5~110 mg NH3/L之间。同时，研究在垃圾焚烧沥滤液短程硝化反硝化过程中的优势群落和相关功能基因，确定短程硝化段的优势菌属主要是脱氮副球菌（Paracoccus），实现其氨氧化功能基因高效表达地FA浓度范围为＜75 mg/L，确定短程反硝化段地优势菌属主要是假单胞菌(Pseudomonas)，参与反硝化过程地功能基因主要有nap、nar、nir、nor、nos。采用细胞接合与同源重组的方法对Pseudomonas aeruginosa PAO1的nosZ基因进行敲除，构建了反硝化产N2O功能菌。投入处理NO2--N浓度700 mg/L的模拟垃圾焚烧沥滤液短程硝化出水可达到73%的N2O转化率和9 mmol N2O日产量，实现了垃圾焚烧沥滤液短程反硝化过程的菌群优化。课题组在此基础上采用固定化nosZ基因敲除菌的方式投入垃圾焚烧沥滤液短程反硝化段长期运行，N2O产量可达 10.3 mmol/（L·d），N2O转化率可达90%，平均回收能量达到9206 kJ/m3。为进一步优化垃圾焚烧沥滤液生物处理产N2O的稳定性，采用nosZ基因敲除菌耦合MEC反应器的方式对垃圾焚烧沥滤液短程硝化出水处理，在最优电势0.8 v条件下，N2O产量8.32 mmol/（L·d），N2O转化率达73%。与固定化方式相比，nosZ基因敲除菌耦合MEC体系可以实现垃圾焚烧沥滤液短程硝化出水原水（NO2--N浓度达1000 mg/L）的处理， Pseudomonas菌属在体系的内的优势地位更明显，有利于N2O的稳定产出。本项目研究实现了在处理垃圾焚烧沥滤液短程硝化反硝化系统的稳定运行和氨氮高效转化为N2O，为垃圾焚烧沥滤液的能源化利用奠定了重要基础。