地下水高氯酸盐和硝酸盐复合污染的低碳源异养与硫自养协同净化机制

Perchlorate and nitrate is a kind of common contaminants in groundwater, however, perchlorate is usually present at low concentration (in ppb range), while nitrate is often found in much higher concentration (in ppm range). It is difficult to develop a remediation technology to remove both perchlorate and nitrate efficiently from contaminated water resources. Biological technology is the most favorable way to remove them, but each biological method has disadvantages . The heterotrophic process uses organic compounds as carbon source, it has advantages of high reaction rate and easily acclimation of microorganisms. But when excessive organic compound added, the residual organic compound will pollute the treated water. Sulfur autotrophic process could utilize inorganic carbon substrates and rely on sulfur for energy, its advantages are: avoiding secondary pollution of residual carbon source and low biomass yield, but sulfate is generated as a by-product during the reaction. In order to take full advantage of heterotrophic and sulfur autotrophic method, a new system combined heterotrophic and sulfur autotrophic process is proposed in this research. In such combined system, both perchlorate and nitrate are firstly reduced in heterotrophic process, since insufficient carbon source is added in this step, secondary pollution of residual carbon source could be avoided. Furthermore, the residual contaminants would be reduced in sulfur autotrophic process. Sulfate generated by sulfur autotrophic reaction could be controlled by the reaction load of sulfur autotrophic part. The main purpose for combination is to avoid secondary pollution of residual carbon source, realize sulfate control and achieve pH balance during the two steps. This proposed research will (1) develop the combined heterotrophic of insufficient carbon source with sulfur autotrophic reaction system; (2) elucidate the collaborative reaction mechanism of heterotrophic and sulfur autotrophic process; (3) provided theoretical foundation and scientific basis for biological technology application in the pollution control of groundwater.

高氯酸盐与硝酸盐是一类地下水中常见无机污染物，二者浓度水平相差较大，实现二者的高效去除，已成为研究热点和难点。生物法是最具应用前景的方法，但异养生物还原过程中，有机碳源添加量不易控制，过少会影响去除效果，过多则残余在水中形成二次污染；硫自养生物还原过程较为清洁，但易出现副产物硫酸盐超标等问题。本研究将异养与硫自养方法相结合，以克服异养有机物二次污染及硫自养副产物硫酸盐超标等不足，同时实现对两种污染物的高效去除。基本原理是：在异养段施加不足量的有机碳源，硫自养段在其基础上强化降解残余污染物，在保证去除效率的前提下有效避免了二次污染；两段负荷及操作参数可灵活调配，有效控制硫自养副产物硫酸盐的产生量，进一步稳定出水的pH值。通过本项目的研究，可望建立低碳源异养协同硫自养生物还原系统，阐明复合污染的异养自养协同降解机制，为新型生物技术在降解地下水复合污染中的应用提供理论基础和科学依据。

高氯酸盐与硝酸盐是地下水中常见共存无机污染物，实现二者的高效去除，已成为研究热点和难点。本研究将异养与硫自养方法相结合，考察协同降解条件下，复合污染的降解机制，并通过高通量测序技术测定不同营养、不同操作条件下协同体系中微生物群落组成及结构变化。.(1) 分别以乙酸钠和丙酮酸钠为有机碳源，考察异养还原去除高氯酸盐的动力学过程及相关影响因素，研究发现Monod方程能较好的描述异养降解高氯酸盐的动力学过程；反应适宜的pH值为7-8，3倍碳源投加可实现高氯酸盐的完全去除；硝酸盐与高氯酸盐竞争利用碳源，对高氯酸盐的降解产生抑制作用；两种碳源驯化的高氯酸盐降解优势菌属均为Dechloromonas属。.(2) 建立升流式硫自养固定床反应器，针对复合污染和单独高氯酸盐污染，考察硫自养降解的动力学过程、副产物产生机制及菌群群落结构变化，结果表明，当两种污染物负荷分别为672.6g-NO3--N/m3.d和627.2g-ClO4-/m3.d时，反应器可以实现对二者的高效去除；硝酸盐与高氯酸盐的降解过程均符合1/2动力学模型；硫歧化反应伴随着高氯酸盐的降解，导致碱度的过量消耗和硫酸根的过量产生；当共存硝酸盐未彻底去除时，硫歧化反应受到抑制；Chlorobaculum属为主要的歧化菌属，菌属Sulfurimonas、Thiobacillus、Thiobacter为主要的NB / PRB (硝酸盐/高氯酸盐还原菌)，菌属Ferritrophicum为主要的NB(硝酸盐还原菌)；随着污染物的降解，菌群α多样性呈下降趋势。.(3)考察异养-硫自养协同系统对复合污染降解效能及相关规律，结果表明，当异养段施加碳源不足时，硝酸盐与高氯酸盐竞争利用碳源，硝酸盐去除率高于高氯酸盐，共存的硝酸盐是影响高氯酸盐去除的重要因素；硫自养段能在异养段的基础上继续降解残余污染物，出水高氯酸盐和硝酸盐均低于检出限；在高浓度碳源施加条件下，残余的有机碳源在自养段被进一步消耗，协同系统出水TOC浓度降低，在低碳源施加条件下，协同系统出水TOC浓度均<5.0mg/L，证实协同降解系统可以有效避免有机碳源二次污染问题。. 通过本项目研究，进一步阐明了地下水高氯酸盐和硝酸盐复合污染的异养与硫自养协同净化机制，明确了相关产物、副产物的产生规律，运用高通量测序技术，丰富了对该系统内部微生物群落构成及动态变化的认识。