SWIS基质层ORP动态分区特征及其对生物脱氮的影响

The subsurface wastewater infiltration system (SWIS) has been considered as a multi-medium coupled "black box" with congenerous nitrification and denitrification environment. The oxidation reduction potential (ORP) in substrate can be affected dynamically by solid phase properties, biological processes, water flowing status, and porous medium permeability jointly. According to the existing theory, the nitrification and denitrification environment division in SWIS substrate has a regular geometrical morphology. This thoery neglectes the effects of local substrate clogging, micro-structure anti-homogenization and electrochemical behaviors of Fe and Mn on the ORP abnormal volatilities in some substrate micro-zones. Furthermore, because the existing characterization method of substrate ORP has some defects, the classical theory of substrate ORP division may be not perfect and credible. So what is the true division of the substrate ORP, regular geometrical morphology or flurried cross mosaic structure? And what are the key factors causing the OPR abnormal volatilities in some substrate micro-zones? To reveal this mechanism, more researches must be conducted. This study will reveal the types and mechanisms of the key factors, which result the abnormal fluctuations of ORP, through simulation and in situ experiments, along with scanning electron microscope technology, molecular biology analysis, interfacial electrochemistry and permeation fluid mechanics calculations. Then, quantitative analysis methods of ORP changes will be presented under both saturated and unsaturated conditions. Furthermore, ORP division characterization and dynamic model of denitrification in SWIS will be clarified to improve the theory development of SWIS.

污水地下渗滤系统（SWIS）是多介质耦合、硝化与反硝化共存的过程黑箱，基质层氧化还原电位（ORP）受固相性质、生物过程、水流态特征和介质渗透性等因素共同作用，导致发生动态变化。已有理论认为基质层硝化和反硝化环境分区具有规则几何形态，未考虑基质局部堵塞、微观结构逆均匀化、Fe/Mn组份电化学行为等对微区ORP异常波动的影响，且ORP表征方法也存在缺陷，因此，基质层ORP分区究竟是规则几何形态还是混杂互镶嵌形态，以及导致微区ORP异常的关键因子是什么，尚需被进一步揭示。本项目针对这一科学问题，拟通过模拟和原位实验手段，采用微观形貌观察、分子生物学分析、界面电化学和耦合渗流力学计算等方法，辨识诱导微区ORP异常的关键因素及其作用机理，探索饱和与不饱和条件下基质层ORP定量表征方法，绘制基质层ORP变化全景图谱，解译各图景演变特征，建立基于基质层ORP变化的脱氮动力学模型，完善SWIS理论。

污水地下渗滤系统（SWIS）是多介质耦合、硝化与反硝化共存的过程黑箱，其基质层氧化还原电位（ORP）受多因素共同作用发生非线性动态变化，从而导致脱氮微环境分区具有不规则形态，按照传统土壤学原理调控SWIS将影响脱氮过程。基于基质理化性质、进水负荷波动、温度、微生物结构演变等多个角度，揭示基质层ORP分区变化规律，对于精确刻画SWIS微环境、精准调控脱氮过程，具有重要科学意义。本项目以可实时监测基质层ORP的多参数模拟SWIS系统为研究平台，系统研究了基质物相组成、骨架渗透性、进水负荷、间歇运行、床层温度等复杂因素波动对基质层ORP分区形态与演变规律的影响，并在此基础上，探索了因ORP改变诱导的脱氮微生物群落结构演替特征，从而建立了基质层ORP与生物脱氮过程的定量关联。研究表明：基质层中Fe(II)与Mn(II)含量的比值是表征ORP的重要指标，基于Nernst方程可知ORP与-lg[c(Fe2+)]、-lg[c(Mn2+)]显著正相关，然而这种正相关并不绝对，ORP分区在基质层结构各向异质特征明显的场景出现异常。基质层TOC及TOC氧化活度指数（OI）与ORP呈显著正相关。干-湿交替运行条件下基质层ORP分区明显，40cm剖面以上ORP呈降-升变化，40-95cm剖面ORP呈升-降变化，145cm剖面ORP保持稳定（-（200-350）mv），ORP分区存在不同程度的重合、过渡或穿透，表明分区不是规则形态，而是非线性形态。高水力负荷波动对ORP的影响明显，分区的非线性变化规律显著。温度对ORP的影响仅在小水力负荷及上层床体明显。基于神经网络的ORP拟合模型可以描述ORP分区长期动态变化。基质层非饱和渗透系数（UPC）计算结果显示，50cm处UPC与ORP相关性弱，70-115cm处UPC与ORP正相关，70和100cm处ORP波动剧烈。基质层NH4+可发生晶层蓄闭，其归宿是伊利石晶格，NH4+蓄闭可导致固铵矿物层间脱水收缩。微生物代谢组学与16SrDNA分析表明，基质垂直深度、有机氮-NH4+-NO3-浓度均可在门、属两个水平上影响脱氮微生物群落结构。