碳源梯级利用模式下深度反硝化低温强化脱氮及功能菌群构建策略研究

The problems of low carbon resource and low temperature existing in city wastewater treatment are key problems waiting to be resolved. The new process of enhanced nitrogen removal with the pattern of grade use of carbon resource to deep denitrification under low temprature is designed by our group. First, the carbon resource is absorbed by phosphorus accumulating bacteria in anaerobic tank. Second, carbon resource is used by denitrifying bacteria in the first denitrification phase. After these phases, readily biodegradable substances is used up. However, hydrolytic acidification phase will then transform the residual carbon resource to readily biodegradable before flowing into the second denitrification phase which will make enhanced denitrification reliable. At the same time, denitrification and phosphorus removal bacteria in these phase will uptake phosphorus and denitrify using carbon resource existing in the cells.In this case, denitrification and phosphorus removal happen simultaneously. This new process not only can resolve the problem of lack of carbon resource, but also resolve the problem of competition between heterotrophic bacteria and autotrophic bacteria in the aerobic phase. At last, the microbial transformation path of carbon resource in wastewater will be illustrated, and functional microbial community structure of nitrifying bacteria, denitrifying bacteria, denitrifying and phosphorus removal bacteria and hydrolytic acidification bacteria will all be investigated. And the strategy of strenthening functional microbial community at low temperature and microbial community evolutionary changes under changing temperature will also be definited. All the results will offer theoretical guide for resolving the problems of low carbon resource and low nitrogen removal at low temperature.

城镇污水脱氮除磷过程中碳源不足问题及冬季脱氮效果差的问题一直是水处理行业中亟待解决的关键问题。本课题组针对这两个问题提出基于碳源梯级利用模式的深度反硝化低温脱氮除磷新工艺。即污水中的碳源先在厌氧阶段被聚磷菌利用释磷后，进入初级缺氧阶段被反硝化菌利用反硝化。这时污水中易被生物利用的碳源几乎消耗殆尽，再进入水解酸化阶段，剩余的不容易被生物利用的碳源将转化成易生物利用碳源，随后进入二级缺氧反应阶段深度反硝化。同时由于反硝化聚磷菌的存在，利用生物体内碳源在反硝化的同时进行过量吸磷，既保证了碳源的供给，又完成了磷的过量摄取。可以解决碳源不足问题，及由于碳源过多进入好养阶段造成异养菌与自养菌的竞争问题。最终将揭示碳源梯级利用微生物转化途径，低温条件下硝化菌、反硝化菌、反硝化聚磷菌、水解酸化菌等功能菌群结构组成，提出低温功能菌群强化策略、变温条件下群落演替规律，为解决碳源不足和低温脱氮问题提供理论指导。

我国东北地区由于冬季气温低且持续时间较长，污水的生物脱氮除磷处理工艺面临很大挑战，同时更由于生物脱氮除磷的需求，污水中有机碳源相对不足，造成脱氮除磷效果低。因此，研究低温、低碳氮比污水强化处理技术具有重要意义。针对低温问题，通过好氧段投加填料、增加水力停留时间、增加污泥龄等强化措施，考察低温条件下复合系统的处理效能，并通过高通量测序技术揭示系统内微生物群落组成随温度变化的演替规律。针对低碳氮比实际生活污水中碳源不足问题，采用厌氧/缺氧/沉淀/接触氧化/沉淀池的双污泥回流工艺，通过延长厌氧、缺氧段水力停留时间，保证碳源在系统中的梯级高效利用，强化低碳氮比污水的脱氮除磷效能。.研究结果表明，通过采取强化措施，增加污泥龄至24d、延长水力停留时间至7.5h，在5℃下，可以实现氨氮、总氮排放满足国家一级A的要求，但是氨氮已接近标准（8mg/L）的临界值，出水总氮在10mg/L左右。菌群分析表明，硝化菌在生物膜上的相对丰度远远高于其在活性污泥中的相对丰度，10℃条件下生物膜上硝化菌的相对丰度高于5℃。.同时研究还表明，系统厌氧水力停留时间由2.5h増至4.5h，系统对COD的降解率增加了2.35%，总氮的去除率增加了1.5%左右，正磷酸盐的去除率提高了约2.5%。实验数据也证明了通过延长厌氧水力停留时间，可以使原水中更多的碳源参与了反硝化吸磷。延长缺氧水力停留时间，总氮去除率逐渐增加，水力停留时间为7.7h时，总氮的去除率为69.85%，即通过延长缺氧水力停留时间可以较大提高总氮去除率；同时可以提高系统对正磷酸盐的去除率。缺氧水力停留时间从4.3h延长到7.7h，系统对正磷酸盐的去除率可以从87.25%提高到89.95%。研究还表明，延长缺氧段水力停留时间，可以提高系统对难降解有机物的去除效果。