Estimating rate constants of contaminant removal in constructed wetlands treating winery effluent: A comparison of three different methods

In this paper we investigated the use of three different methods for determining the rate constants for degradation of winery effluent within a sub-surface flow constructed wetland (CW). These methods comprised of using a dispersed plug flow (the Peclet) equation; a tanks-in-series (TIS) equation; and analysing the residence time distribution (RTD) directly. The last of these is described by the convolution integral (CI). We demonstrated self-similarity of the RTDs, which meant that the system's hydraulics were similar throughout the CW. We therefore extrapolated the RTD data to develop a more complete understanding of the hydraulic properties of the CW and examine how they affected the kinetics of degradation. We found that whilst both the Peclet and the TIS equation were able to predict concentration within the CW, this required the optimisation of more than one variable at the same time rendering a result that was more of a modelling exercise than a useful design tool. The CI method could be applied to predict system parameters effectively. We used it to measure rate constants of removal for both ethanol and potassium (key species for tracking the degradation/treatment of the effluent). Acetic acid, however, did not degrade implying that the CW operated aerobically. The concentration of sodium increased very slightly, indicating that it is not bioremediated/removed and that there are some minor evapotranspirative effects. The rate constant found for the biodegradation of COD was found to have significantly more uncertainty associated with it than the measurement of the rate of degradation individual components and we therefore posit that it is better to describe the processes of degradation by tracking individual components rather than lumped parameters.     

海滨湿地景观过程模型与模拟研究——以江苏盐城保护区核心区为例

景观过程模型已经成为深化景观变化研究的重要手段并日益受到重视。海滨湿地是一种高度复杂和动态变化的景观系统,构建景观过程模型能够从机理上解释湿地景观时空动态演变过程。研究中,将盐城国家级自然保护区核心区划分为人工管理区和自然湿地区两种模式,根据2000、2006、2011 年3 个时相的景观资料以及野外生态监测数据,构建海滨湿地景观过程模型,结果如下：①利用空间代替时间并结合灰色关联分析,确定了海滨湿地景观演变的关键影响因素为土壤盐度和水分;②运用人工神经网络的方法,分析了土壤盐度和水分的空间分异,并通过图层叠加和分级统计,得出了土壤盐度和水分的阈值范围以及变化规律;③运用GIS-Matlab-CA技术构建了基于关键生态过程的海滨湿地景观过程模型,模型总体精度都在80%以上,Kappa 系数都在0.7 以上,一致性检验结果表明空间位置一致率决定了整个景观模拟的精度;④运用已构建好的模型对研究区2012-2020、2025 年的结果进行了模拟预测,预测结果表明,盐城海滨湿地芦苇沼泽和米草沼泽扩张、碱蓬沼泽面积减少的趋势将愈加明显。     

SEMIPERMEABLE MEMBRANE DEVICES USED TO ESTIMATE BIOCONCENTRATION OF POLYCHLORINATED BIPHENYLS1

ABSTRACT: Aquatic organisms passively accumulate hydrophobic organic compounds, such as polychlorinated biphenyls, even when ambient water concentrations of the contaminant are below analytical detection limits. However, contaminant concentrations in tissue samples are subject to an inherently high level of variability due to differences in species, life stage, and gender bioconcentration potentials. Semipermeable membrane devices (SPMDs) were used to sample Aroclor 1254, a mixture of readily bioconcentrated polychlorinated biphenyls (PCBs), in a contaminated wetland near Flat Top, WV. The devices consisted of triolein, a lipid found in fish, enclosed in a polyethylene membrane. SPMDs were deployed in the water column and in direct contact with wetland sediments along a previously identified concentration gradient of PCBs. The devices were retrieved after a 25-day exposure period. Analytes were recovered by dialyzing the devices in nanograde hexane. Hexane dialysates were condensed and analyzed by gas chromatography. All deployed devices sequestered quantifiable amounts of Aroclor 1254. Water-column SPMDs accumulated PCBs far in excess of ambient water concentrations. The devices contacting sediments accumulated PCBs at all sites, though accumulated concentrations did not exceed concentrations in sediment. Patterns of PCB concentration in the devices corresponded to the identified gradient at the site. Results from the water-column SPMDs were used to estimate the concentration of the dissolved, bioavailable fraction of PCBs present in the water column. These concentrations ranged from 0.01 to 0.09 μg/L of bioavailable Aroclor 1254.     

CHANNEL MORPHOLOGY EVOLUTION AND OVERBANK FLOW IN THE GEORGIA PIEDMONT1

ABSTRACT: Historic changes in stream channel morphology were investigated in the Georgia Piedmont to better understand the hydrologic processes and functioning of the region's riverine systems. USGS gaging station data and channel geomorphology data were collected from thirty study sites in the Upper Oconee River Basin for flood frequency analysis. Historic and modern (i.e., present-day) channel capacity discharge (i.e., overbank flow) was calculated using Manning's equation and historic channel cross-section records. The recurrence interval for overbank flow was estimated for each site from flood frequency data. Results indicate that channel expansion has occurred throughout the basin, especially in upper reaches. Recurrence intervals for modern overbank events were variable and generally high ranging from < 2 to > 500 years for first to third order streams. They were less variable and lower for fourth and fifth order streams, ranging from < 2 to 3 years. Potential depositional thresholds were identified that exemplify the complex response of sediment distribution patterns throughout the basin. Results indicate overbank flows occur less frequently now than they once did due to historic accelerated sedimentation and subsequent channel expansion. One application of these findings is that these basin processes are likely applicable across the region and may impact the hydrologic functioning of associated Piedmont riverine wetlands that depend on flooding regimes.     

人工湿地污染物去除效率稳定性分析——以沈阳市满堂河污水处理中心为例

利用沈阳市满堂河污水处理中心人工湿地8年来运行数据,对人工湿地整体系统和不同功能区的水质净化效果进行了对比分析,结果表明,潜流人工湿地对CODCr的去除效率,在50%～70%;表面流人工湿地对CODCr的去除效率,稳定在20%左右;人工湿地系统整体对悬浮物和氨氮的去除效率保持在50%以上;人工湿地系统对污染物质的去除效率,随着运行时间增加而日趋稳定。     

不同植物的表面流人工湿地系统对污染物的去除效果

通过对4种不同植物的表面流人工湿地系统处理新沂河河水的中试研究表明,在CODMn和NH 4-N进水浓度相同条件下,香蒲湿地系统出水CODMn平均浓度最低,仅为13.44 mg/L;美人蕉湿地系统出水NH 4-N平均浓度最低,仅为1.75 mg/L;香蒲和美人蕉湿地系统对CODMn的平均去除率都达到40%以上,而千屈菜和水葱湿地系统都低于30%;美人蕉、香蒲和千屈菜湿地系统对NH 4-N的平均去除率都达到65%以上,而水葱系统则低于60%.综合比较,香蒲和美人蕉湿地系统的净化能力较强.4种植物中水葱耐淹能力最强,完全淹水22 d以上依然生长良好;千屈菜耐淹能力最弱,完全淹水7 d后就开始枯萎,17 d后地上、地下部分全部死亡.     

两种典型PPCPs在潜流人工湿地中的季节性去除效果及降解产物

药物及个人护理品(PPCPs)在地表水中的污染问题已引起了广泛关注,人工湿地(constructed wetlands,CWs)在PPCPs去除中具有突出优势,然而关于不同类型PPCPs 在CWs 去除中的相互作用研究得还较少.本研究选取两种常用且相对分子质量接近的典型PPCPs——广谱抗菌剂三氯生(TCS)和非甾体抗...     

潜流人工湿地基质结构与微生物群落特征的相关性

为查明造成不同基质结构人工湿地净化性能差异的微生物因素,利用高通量测序技术,研究水平潜流人工湿地基质结构与微生物群落结构的相关性.结果表明,3个对比人工湿地系统中,从床体表层到底层渗透系数逐渐升高的六层结构人工湿地(CW6)净化性能最高,其出水中COD、TN、NO-3-N及NH_4~+-N平均浓度分别为39、11、0.35及4 mg·L~(-1),其后为三层结构人工湿地(CW3),而单层结构人工湿地(CW1)的净化效果最差,平均出水浓度分别为95、21、0.60及12 mg·L~(-1).高通量测序结果显示,多层结构人工湿地中微生物OTUs略低于单层结构湿地,但其优势菌门变形菌门(Proteobacteria)和其属水平上的硝化与反硝化细菌的相对丰度却显著高于单层湿地.PCA和丰度热图分析结果显示,CW3和CW6床体中变形菌门(Proteobacteria)属水平上的微生物存在显著的空间分布差异,从而有利于污染物的分区降解,而CW1各样点间的微生物群落结构无显著性差异.     

人工快速渗滤系统的运行方式对复氧效果的影响

本文通过在CRI系统现场系统中湿干比,水力负荷周期和增加通气管对复氧效果的研究,发现在湿干比1∶6时,CRI系统对与复氧有关的指标CODCr、NH3-N的去除率较高,系统复氧效果较好;通过缩短系统水力负荷周期,加大系统淹水、落干频率,可以加大系统的复氧量,提高系统的复氧效率,CODCr和NH3-N的去除效果均有所提高;增加通气管对CRI系统复氧效果不明显。     

植物床-沟壕系统的藻类捕获功能

采用原位实验验证植物床．沟壕系统的藻类捕获功能。结果表明：该系统能够有效拦截和捕获源水藻类。在水力梯度驱动下,约35％源水进入高位小沟流经植物床内部根孔结构而汇至低位小沟。低位小沟内叶绿素a（Chl-a）浓度显著低于高位小沟（P=0．0239）,其降低比例为11．1％。以植物床．沟壕系统为结构形式的根孔净化区其出水Chl-a浓度较源水整体下降了27．0％。估算该片根孔净化区捕获藻类鲜生物量约122kg／d。石臼漾湿地共含根孔净化区11片,按供水25万t／d计,估算捕获藻类鲜生物量约1100kg／d。