生态沟渠净化稻田排水动力学分析和生物相特征

Dynamics analysis and biofacies characteristics of drainage from paddy fields purified by ecological ditches

本研究以太湖流域常见的菱角、水葫芦、梭鱼草、圆币草等水生植物和人工水草、塑料立体弹性填料为生态强化载体,构建"水生植物-载体生物膜-菌藻"复合型生态系统,研究了稻田排水中的氮、磷等营养元素的去除特性,构建氮、磷污染物的降解动力学模型,并调查了沟渠内"微生物-藻类"生物相特征.结果表明,生态沟渠运行期间,随着水稻进入不同的生长阶段,系统内氮、磷等营养元素的去除率都呈普遍下降趋势,总磷、氨氮、总氮、硝态氮平均去除率分别达到87.1%、92.3%、77.5%、88.6%,其中氨氮的去除率最高,化学需氧量(CODMn)的去除效果并不显著,各实验周期的污染物降解趋势均符合一级动力学降解模型.经生物相分析揭示:随着复合生态系统运行延续,系统内微生物、藻类的种类及Shannon-Weiner index等多样性指数呈不断增长趋势,表明复合生态系统水质改善后更适于多种类细菌与藻类生存与繁殖;复合生态系统中的菌、藻、水生植物及其表面附着的生物膜对污染物的去除具有协同作用,强化了生态沟渠的自净能力.

In this study,artificial aquatic weeds,plastic stereoelastic fillers and aquatic plants native to Taihu Lake,such as water hyacinth,water chestnut,pickerelweed,and pennisetum,were used as ecological reinforcement carriers to construct an aquatic plant-carrier biofilm-bacteria and algae complex ecosystem.Ecological ditches were utilized as research environments to reveal the removal characteristics of nitrogen(N),phosphorus(P)and other nutrients in paddy field drainage,to construct the degradation kinetic models of nitrogen(N)and phosphorus(P)pollutants,to clarify the biofacies characteristics of"microorganism-algae"interactions in ditches.The results showed that during the operation of ecological ditches,the removal rates of nitrogen(N),phosphorus(P)and other nutrients decreased as the rice enters different growth stages.The mean concentration removal efficiencies in the ecological ditches for total phosphorus(TP),ammonia nitrogen(NH3-N),total nitrogen(TN)and nitrate nitrogen(NO3-N)were 87.1%,92.3%,77.5%and 88.6%,respectively.Among them,the ammonia nitrogen(NH3-N)removal rate was the highest,while the chemical oxygen demand(CODMn)removal efficiency was not significant.The degradation trends of the pollutants in each experimental period conform to first-order kinetic degradation models.Biofacies analysis revealed that the species of microorganisms and algae,the Shannon-Weiner index and other diversity indices increased with the continuous operation of the complex ecosystem.This showed that the improved water quality of the complex ecosystem was more suitable for the survival and reproduction of many kinds of bacteria and algae.Additionally,bacteria,algae,aquatic plants and biofilms attached on the surfaces of the complex ecosystem had synergistic effects on pollutant removal,and strengthen the self purification capacity of the ecological ditch.