地下渗滤系统在污水处理中的应用研究进展

地下渗滤系统是一种基于自然生态原理的污水净化技术 ,在我国有着良好的可行性和发展前景。本文总结介绍了地下渗滤系统的类型 ,概括分析了地下渗滤系统中的关键性问题———土壤的选择与配制、水力负荷的选取、氮磷去除问题和土壤堵塞问题     

人工快速渗滤系统对污染物的去除机制

人工快速渗滤系统(CRI)是在传统的污水快速渗滤处理系统(RI)的基础上发展起来的一种新型的污水土地处理技术.通过对CRI的模拟,揭示了非生物机制与生物机制对有机物、营养元素的降解机制.结果表明,CRI对污水中污染物的去除是在非生物机制与生物机制协同作用下完成的.对污水中的有机物和氮的降解以生物机制为主、非生物机制为辅;对磷的降解则以非生物机制为主、生物机制为辅.生物机制对有机物、氮的去除占70%以上,非生物机制对磷的去除占61.9%.系统中氮转化以硝化效果为主,反硝化效果较弱.     

阴离子洗涤剂在慢速渗滤系统中的去除研究

慢速渗滤系统的土壤－植物系统对ＭＡＢＳ有较强的净化功能；土壤－牧草系统和土壤－小麦系统对ＭＡＢＳ的去除率与停留时间呈高度正相关；城市污水中ＭＡＢＳ含量低于５．３７８ｍｌ／ｌ时，两个系统对ＭＡＢＳ的去除率可维持在９５％的平均水平上。     

降雨条件下黄土斜坡的入渗特征分析

为研究黄土斜坡的降雨入渗规律和降雨诱发黄土滑坡的机理,在宁夏西吉县一黄土斜坡建立了监测站,在斜坡上部开挖探井并安装了土壤水分计观测土壤含水率,在探井附近安装了小型气象站,观测气温、降雨量、蒸发量。通过现场观测数据分析了气象条件对土壤含水率的影响,以及雨水在黄土斜坡中的入渗规律。使用SEEP/W软件分析了完整黄土斜坡和有裂隙黄土斜坡在临界降雨条件下的孔隙水压力分布,以及斜坡孔隙水压力随深度的变化规律。结果表明,深度1 m以内的土壤含水率变化受蒸发量与降雨量的影响显著,深度越大,土壤含水率的变化曲线越平缓。强度大于19 mm/d的降雨才会引起土壤含水率的骤增,且土壤含水率变化比降雨延迟48 h左右。斜坡表面发育的裂隙是雨水进入斜坡体内部的主要通道。降雨会在有裂隙的斜坡内部形成饱和区,使土体抗剪强度降低,饱和渗流会增加斜坡下滑力,这些作用使黄土斜坡发生滑动。现场监测研究得出了研究区滑坡临界降雨量的参考值,提出斜坡裂隙是降雨诱发黄土滑坡的重要因素。     

间歇梯度曝气的生活污水好氧颗粒污泥脱氮除磷

本研究设置了3个SBR反应器R1、R2和R3,分别采用(A/O)_3-SBR梯度曝气、(A/O)_3-SBR恒定曝气和传统(A/O)-SBR方式运行,以实际城市生活污水为进水基质,探讨了不同曝气方式下的营养物去除性能和好氧颗粒污泥特性,为低强度城市污水的碳源合理利用提供合理的方式.由实验结果可知,R1、R2和R3中颗粒在稳定时期对COD的平均去除率分别为88.68%、 89.05%和88.96%,对TN的平均去除率分别为76.97%、 71.99%和64.92%,对TP的平均去除率分别为96.28%、 85.05%和78.97%,且反硝化聚磷菌占聚磷菌的比例分别为25.52%、 19.60%和12.77%.结果表明,厌氧、好氧和缺氧交替的运行方式更有利于反硝化聚磷菌(DPAOs)的富集,且梯度曝气较恒定曝气方式富集更多,这对碳源不足的低强度城市生活污水处理有重要意义;同时R1中曝气段溶解氧逐级降低,提高了颗粒同步硝化反硝化率和降低了能耗,有利于总氮(TN)的高效去除. 3组反应器在运行后期颗粒粒径分别为727.368、 815.072和895.041μm,且通过对颗粒进行显微观察可以看出, R2和R3中颗粒不如R1中密实.此外,R1、R2和R3运行后期PN/PS值分别为6.31、 5.63和4.83,颗粒稳定时期EPS含量(以VSS计)分别为103.97、 92.22和76.98 mg·g~(-1),表明间歇梯度曝气的方式有利于刺激EPS的分泌,尤其是PN的分泌,使PN/PS值较高,细胞疏水性增强,颗粒密实稳定.     

喀斯特坡地土壤稳渗率空间分布变化特征研究

为查明高异质性背景条件下喀斯特坡地土壤稳渗率空间分布变化特征,在6类典型人为活动方式石灰岩坡地针对4类主要生境类型(土面、土石面、石沟、石缝)开展生境空间分布调查和土壤理化性质分析,并利用Guelph入渗仪进行稳渗率实验。通过对比分析各生境土壤性质和土壤稳渗率关系,结合人为作用方式探讨各生境土壤性质和稳渗率空间变化特征及其演化规律。结果表明:1)喀斯特坡地土壤稳渗率普遍高于非喀斯特地区,喀斯特坡地土壤稳渗率受土壤孔隙和岩石裂隙耦合作用影响。2)各生境条件下土壤稳渗率具有高度的空间异质性,呈现"斑块状"空间分布特征。3)坡地人为作用方式变化将改变原有生境的土壤性质,进而导致各生境土壤稳渗率随人为活动进程发生相应变化。人为踩踏作用影响较小的原生林、次生林和乔灌林坡地土面和土石面生境土壤稳渗率普遍高于石沟和石缝生境,但转变为人为踩踏作用强烈的放牧灌草地或火烧人为干扰地后,土面和土石面生境土壤退化严重,土壤容重和粘粒含量增大,稳渗率显著降低。而石沟和石缝生境土壤性质和稳渗率受影响程度明显小于土面和土石面生境,土壤稳渗率仍可维持较高水平。     

NONLINEAR DUPUIT EQUATIONS FOR THE PHREATIC SURFACE OF A SEMI-INFINITE AQUIFER1

ABSTRACT. We present a new approach to the nonlinear equations for the phreatic surface of groundwater flow from or into a reservoir. The differential equation is converted into an equivalent integral equation, which is then solved by a method of iteration. We obtain exact results for both drawdown and infiltration, including the special case of groundwater penetration into dry soil.     

EVALUATION OF THE MAXEY-EAKIN METHOD FOR ESTIMATING RECHARGE TO GROUND-WATER BASINS IN NEVADA1

AESTRACT An evaluation of the Maxey-Eakin method for calculating recharge to ground-water basins in Nevada was performed. The evaluation consisted of comparing Maxey-Eakin estimates with independent estimates of recharge, and analyzing the nature of the differences between the groups of estimates. In the comparison with the Maxey-Eakin estimates, two different groups of independent estimates were used: (1) 40 recharge estimates that were identified from water budgets contained in reports by the Nevada Department of Conservation and Natural Resources and (2) 27 recharge estimates that were identified from previous studies that used models. The results of the comparisons indicate generally good agreement between the Maxey-Eakin estimates and both groups of independent estimates. To quantify this agreement, an analysis was conducted to estimate the uncertainty in the Maxey-Eakin method. The analysis produced an upper bound on the standard deviation of the Maxey-Eakin estimate for a given basin. For the group of 40 water-budget estimates, the upper bound on the standard deviation for an individual basin is 4,800 acre-ft/yr, and the corresponding coefficient of variation of the Maxey-Eakin estimate is no greater than 44 percent. For the group of 27 model estimates, the upper bound on the standard deviation is 4,100 acre-ft/yr, and the corresponding coefficient of variation is no greater than 24 percent.     

A VOLUME BALANCE SOLUTION FOR WATER FLOW OVER FLAT SOIL SURFACES1

ABSTRACT: This paper presents the development of a mathematical model to compute the advance of water flowing over flat soil surfaces. The solution is of interest to the design and management of irrigation systems, and the model can also be applied to overland flow problems. The hydraulics of water flow during the advance phase is simulated by the Lewis-Milne integral equation. The general solution to this equation is obtained by using the Laplace transform theory. A particular solution was developed, based on series expansions, that uses the modified Kostiakov equation to predict infiltration. The solution is given by a double infinite series that has terms of alternate sign. Results from this model show satisfactory agreement when compared with field data collected by the author.