Evaluation of stem injection for managing giant reed (Arundo donax)

Giant reed is an emergent aquatic plant that may be weedy in riparian habitats. Two herbicides approved for controlling giant reed in the US are glyphosate (N-(phosphonomethyl) glycine) and imazapyr (2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid). Foliar applications of these herbicides may be restricted in some areas, such as those, which are within the range of threatened or endangered species. We conducted two field experiments at sites in northern and central California. The first experiment evaluated the effects of three aquatic herbicides (glyphosate, imazapyr, and triclopyr [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid) injected into all of the stems within a giant reed (5 mL stem^?1). In this experiment, leaf chlorophyll content, the proportion of living stems, and the number of new stems produced during the year after treatment declined (>80%) following injection of either full strength glyphosate or imazapyr. The effects of injecting full strength triclopyr were considerably less. In a second experiment, different proportions (0, 10%, 25%, or 100%) of the stems within a plant were injected with full strength glyphosate. Results indicated that it was necessary to inject all of the stems within a clump to achieve the greatest reduction in the plant growth characteristics measured. These results imply that giant reed may be successfully controlled by injecting full strength glyphosate (5 mL stem^?1) into all of the stems within a clump. While labor intensive and thus potentially more costly this method, offers a new method for managing giant reed in sensitive sites where foliar spray applications may be restricted.     

Evaluation of the giant reed (<Emphasis Type="Italic">Arundo donax</Emphasis>) in horizontal subsurface flow wetlands for the treatment of recirculating aquaculture system effluent

Introduction

Two emergent macrophytes, Arundo donax and Phragmites australis, were established in experimental subsurface flow, gravel-based constructed wetlands (CWs) receiving untreated recirculating aquaculture system wastewater.

Materials and methods

The hydraulic loading rate was 3.75 cm day^?1. Many of the monitored water quality parameters (biological oxygen demand [BOD], total suspended solids [TSS], total phosphorus [TP], total nitrogen [TN], total ammoniacal nitrogen [TAN], nitrate nitrogen [NO₃], and Escherichia coli) were removed efficiently by the CWs, to the extent that the CW effluent was suitable for use on human food crops grown for raw produce consumption under Victorian state regulations and also suitable for reuse within aquaculture systems.

Results and discussion

The BOD, TSS, TP, TN, TAN, and E. coli removal in the A. donax and P. australis beds was 94%, 67%, 96%, 97%, 99.6%, and effectively 100% and 95%, 87%, 95%, 98%, 99.7%, and effectively 100%, respectively, with no significant difference (p?>?0.007) in performance between the A. donax and P. australis CWs. In this study, as expected, the aboveground yield of A. donax top growth (stems + leaves) (15.0?±?3.4 kg wet weight) was considerably more than the P. australis beds (7.4?±?2.8 kg wet weight). The standing crop produced in this short (14-week) trial equates to an estimated 125 and 77 t ?ha^?1 year^?1 biomass (dry weight) for A. donax and P. australis, respectively (assuming that plant growth is similar across a 250-day (September–April) growing season and a single-cut, annual harvest).

Conclusion

The similarity of the performance of the A. donax- and P. australis-planted beds indicates that either may be used in horizontal subsurface flow wetlands treating aquaculture wastewater, although the planting of A. donax provides additional opportunities for secondary income streams through utilization of the energy-rich biomass produced.

     

水平潜流人工湿地处理太原市城市再生水的运行效能

以山西省太原市某污水厂的高氮低碳尾水为研究对象,开展基于3床并联的水平潜流人工湿地处理尾水的中试研究。研究结果表明,该人工湿地系统启动2个月进入稳定运行期;稳定运行期3个床体的出水水质除TN外其余指标均满足《地表水环境质量标准》（GB3838—2002）中Ⅳ类水体标准,TN指标满足《城镇污水处理厂污染物排放标准》（GB18918．2002）中一级A标准,该湿地系统出水可直接用于补充景观用水;稳定运行期3床的植物与基质的配置更适合处理同类尾水,3个床体对各污染物的去除效果均为3床〉2床〉1床;本系统中填料对污染物处理效果的影响大于植物对污染物处理效果的影响,最优填料顺序依次为沸石、砾石和钢渣,最适植物栽种顺序为芦苇、香蒲、美人蕉、黄菖蒲和芦苇。     

水平潜流人工湿地脱氮功效中植物的作用

为了研究芦苇(Phragmites australis)在收割期前/后、湿地床体内部各个区域内、一年四季中在水平潜流人工湿地脱氮效用所起的作用,实验设置了有/无植物2组平行反应器。结果表明,芦苇在收割前/后对于水平潜流人工湿地脱氮效果均有促进作用,植物地上部分氮吸收量占湿地脱氮量的10.2%。在芦苇收割前/后(5月~9月、10月~次年5月),芦苇湿地日均脱氮量分别是无植物湿地的1.55倍与1.11倍。高、矮芦苇不同组织中总氮浓度分布趋势一致,2种芦苇各组织含量分别为:穗(28.69 g/kg)>叶(13.69 g/kg)>茎(5.31 g/kg)、穗(28.06 g/kg)>叶(14.61 g/kg)>茎(8.46 g/kg)。在湿地的各个沿程区域,总氮、氨氮累加去除率变化趋势一致,并且从反应器前部到尾部呈上升趋势,从上部到下部呈下降趋势。有芦苇湿地的脱氮效用优于无植物湿地,且底部氮积累含量也较少。一年四季中有芦苇湿地在各个季节脱氮量是无植物湿地的1.06~1.47倍。     

水平潜流人工湿地在不同水力负荷下的水力效率及可视化分析

构建水平潜流人工湿地装置,通过NaCl示踪脉冲实验,得到不同水力负荷条件下的水力停留时间分布密度曲线,根据不同停留时间的关系计算相对水力效率,并利用染料,进行不同水力负荷下的可视化示踪实验,通过MATLAB处理得到高对比度的流态图像。观察“死区”分布,计算“死区”相对面积用以表征其水力效率。结果表明,湿地装置进水水力负荷较高或较低时,水力效率均较低,且水力负荷较大时更明显;水力分布散度（σ2θ）的大小会对水平潜流人工湿地水力效率造成较大影响;在不同水力负荷下,采用水力学效能（λ）所得到的排序结果相比短路值（s）和有效体积比（e）更能代表实际水平潜流人工湿地的水力效率。     

Optimal conditions for chlorothalonil and dissolved organic carbon in horizontal subsurface flow constructed wetlands

The most efficient system of horizontal subsurface flow constructed wetlands (HSSFCW) for removing dissolved organic carbon (DOC) in the presence of chlorothalonil pesticide (CLT) present in synthetic domestic wastewater was determined using the macrophyte Phragmites australis. Two concentrations of CLT (85 and 385 μg L^?1) and one concentration of glucose (20 mg L^?1) were evaluated in four pilot scale horizontal surface flow constructed wetlands coupled with two sizes of silica gravel, igneous gravel, fine chalky gravel (3.18–6.35 mm), coarse gravel (12.70–25.40 mm) and two water surface heights (20 and 40 cm). For a month, wetlands were acclimated with domestic wastewater. Some groups of bacteria were also identified in the biofilm attached to the gravel. In each treatment periodic samplings were conducted in the influent and effluent. Chlorothalonil was quantified by gas chromatography (GC-ECD m), DOC by an organic carbon analyzer and bacterial groups using conventional microbiology in accordance with Standard Methods. The largest removals of DOC (85.82%–85.31%) were found when using fine gravel (3.18–6.35 mm) and the lower layer of water (20 cm). The bacterial groups quantified in the biofilm were total heterotrophic, revivable heterotrophic, Pseudomonas and total coliforms. The results of this study indicate that fine grain gravel (3.18–6.35 mm) and both water levels (20 to 40 cm) can be used in the removal of organic matter and for the treatment of agricultural effluents contaminated with organo-chloride pesticides like CLT in HSSFCW.     

水平潜流人工湿地流场数值模拟与结构优化分析

为了解决传统水平潜流人工湿地在床体结构设计方面的随意性与经验化问题,以流场均匀分布为目标,利用数值模拟方法对人工湿地床体结构参数进行优化,包括人工湿地基质填充厚度、床体长宽比例、构建尺度、主体填料区的分层填充方式,解析基质结构的配置规律,实现各参数的定量化。模拟结果表明,填料的分层配置对流场分布的影响很大。在基质厚度为0.6 m,长宽比为5∶3,且填料按照渗透系数指数规律分层填充的情况下,流场分布较均匀。在此基础上,根据模拟结果所确定的结构参数构建潜流人工湿地小试装置,并与传统结构人工湿地进行对照,对模拟结果进行验证。实验结果表明,当水力停留时间(HRT)为36 h时,分层填充与单层填充方式的人工湿地对COD、TP和TN的平均去除率分别为64.89%、82.72%、69.69%和29.84%、39.15%、31.83%,结构优化后的人工湿地净化效果得以显著提升。     

Heterotrophic community-level physiological profiles of domestic wastewater following treatment by small constructed subsurface flow wetlands.

Seasonal treatment performance of small-surface flow wetlands was evaluated during their second operational year and compared with community-level physiological profiles (CLPP) of the heterotrophic bacterial community obtained from sole-carbon source utilization patterns in BIOLOG GN (Haywood, California) microplates. The CLPP patterns varied significantly by season, indicating reduced functional diversity in the heterotrophic community during warmer months of active plant growth (April through October). Principal component analysis (PCA) suggested that the functional community differed in planted versus unplanted wetlands during the growing season. Wetlands generally improved wastewater quality; however, treatment performance was reduced in the second year. Despite differences in the heterotrophic community suggested by CLPP, treatment efficiency with respect to removal of five-day biochemical oxygen demand or reduction in fecal indicator organisms generally was not significantly changed as a function of growing season or plant treatment.     

Behavior of selected priority organic pollutants in horizontal subsurface flow constructed wetlands: a preliminary screening

A discrete injection experiment was carried out in a constructed wetland to evaluate the behavior of selected priority pollutants. A horizontal subsurface flow pilot plant located in the NE of Spain was selected for this study. A total of eight European Priority Pollutants listed in the Water Framework Directive were considered, including a commonly used herbicide (mecoprop). The pollutants encompassed a variety of chemical classes and physicochemical properties. They included organochlorine, organophosphorus, phenols, chloroacetanilides, triazine, phenoxycarboxylic acid and phenylurea pesticides. A time series of composite effluent samples and discrete gravel bed samples from the wetland were analyzed. Response curves for all the pollutants injected from effluent concentrations were obtained and compared with the tracer (clofibric acid). On the basis of an analysis of the samples taken 21 days after the injection, priority pollutants were classified into four groups according to their removal efficiency. These groups were (i) the highly efficiently removed (>90%), namely lindane, pentachlorophenol, endosulfan and pentachlorobenzene; (ii) the efficiently removed (80-90%), namely alachlor and chlorpyriphos; (iii) poorly removed (20%), namely mecoprop and simazine; and (iv) recalcitrant to elimination, namely clofibric acid and diuron. Taking into account the poor accumulation of the injected contaminants in the gravel bed (0-20%), biodegradation and plant uptake are postulated as the most likely elimination pathways for the pollutants.     

Performance of hybrid vertical up- and downflow subsurface flow constructed wetlands in treating synthetic high-strength wastewater

The performance and temporal variation of hybrid vertical-subsurface flow constructed wetlands (VFCWs) in response to two-stage combinations of vertical upflow (VUF) and vertical downflow (VDF) were analyzed in this research. The results of high carbon (C) treatment and high nitrogen (N) treatment were similar. The Lythrum salicaria treatment showed higher removal efficiency than CWs planted with Acorus calamus. Under high C- and N-loading treatments, the optimum two-stage combination was VDF-VUF VFCWs planted with A. calamus. Furthermore, the highest nutrient removal efficiencies were achieved in late summer (July and August) and early autumn (September). The chemical oxygen demand and total nitrogen removal efficiencies were significantly affected (P?<?0.05) by season, system, and wetland plant.     

间歇曝气潜流人工湿地的污水脱氮效果

采用间歇曝气运行方式,提升潜流人工湿地生活污水处理系统中的溶解氧浓度,强化脱氮效果。结果表明,间歇曝气运行方式有效提高了湿地内部溶解氧水平,曝气时溶解氧浓度可达6~9 mg/L,停止曝气后,溶解氧浓度迅速下降至0.5 mg/L以下,在湿地内部营造了一种交替的好氧和缺氧环境,分别促进好氧硝化和缺氧反硝化作用。在水力停留时间为3 d的情况下,间歇曝气潜流人工湿地系统对氨氮、总氮和COD的去除率分别可达到98.0%、87.6%和96.3%,较常规潜流人工湿地系统分别提高了74.1%、56.4%和18.1%,实现了氨氮、总氮和COD的同步高效去除。     

曝气条件下进水C/N对水平潜流型人工湿地脱氮效果和氮转化功能微生物丰度的影响

为提高潜流型人工湿地在低C/N条件下的污水处理效果,考察了在植物生长旺盛期曝气条件下不同C/N(0.9∶1、2∶1、4∶1)对污水的脱氮效率、微生物群落结构和功能微生物丰度的影响.结果表明:NO3-去除率为57.48％～83.19％且随C/N的增加而增加;当C/N为2和4时,可提高COD和TN的去除率,COD和TN去除...     

Performance of an integrated system combining microalgae and vertical flow constructed wetlands for urban wastewater treatment

Environmental Science and Pollution Research - The present study investigated the performance of an integrated system, combining the sequential use of microalgae (MA) and vertical flow constructed...     

Effect of vegetation in pilot-scale horizontal subsurface flow constructed wetlands treating sulphate rich groundwater contaminated with a low and high chlorinated hydrocarbon

In order to characterize the effect of vegetation on performance of constructed wetlands (CWs) treating low and high chlorinated hydrocarbon, two pilot-scale horizontal subsurface flow (HSSF) CWs (planted with Phragmites australis and unplanted) treating sulphate rich groundwater contaminated with MCB (monochlorobenzene, as a low chlorinated hydrocarbon), (about 10 mg L⁻¹), and PCE (perchloroethylene, as a high chlorinated hydrocarbon), (about 2 mg L⁻¹), were examined. With mean MCB inflow load of 299 mg m⁻² d⁻¹, the removal rate was 58 and 208 mg m⁻² d⁻¹ in the unplanted and planted wetland, respectively, after 4 m from the inlet. PCE was almost completely removed in both wetlands with mean inflow load of 49 mg m⁻² d⁻¹. However, toxic metabolites cis-1,2-DCE (dichloroethene) and VC (vinyl chloride) accumulated in the unplanted wetland; up to 70% and 25% of PCE was dechlorinated to cis-1,2-DCE and VC after 4 m from the inlet, respectively. Because of high sulphate concentration (around 850 mg L⁻¹) in the groundwater, the plant derived organic carbon caused sulphide formation (up to 15 mg L⁻¹) in the planted wetland, which impaired the MCB removal but not statistically significant. The results showed significant enhancement of vegetation on the removal of the low chlorinated hydrocarbon MCB, which is probably due to the fact that aerobic MCB degraders are benefited from the oxygen released by plant roots. Vegetation also stimulated completely dechlorination of PCE due to plant derived organic carbon, which is potentially to provide electron donor for dechlorination process. The plant derived organic carbon also stimulated dissimilatory sulphate reduction, which subsequently have negative effect on MCB removal.     

菖蒲和空心菜在处理微污染河水潜流人工湿地中的应用

为了探讨修复微污染河水的潜流湿地中植物对污染物去除效果的影响及其生长变化,在野外条件下构建2座分别栽种菖蒲和空心菜的水平潜流人工湿地,并以未栽种植物的湿地作空白。分析了湿地中污染物的去除效果,考察了湿地中植物的生物量、根系活力和氮磷含量的变化。植物湿地中污染物净化效果优于空白湿地,菖蒲和空心菜湿地对氨氮(NH+4-N)、总氮(TN)、总磷(TP)和高锰酸盐指数(CODMn)的平均去除率分别为61.1%和57.5%,31.5%和39.7%,24.7%和25.5%,20.4%和20.7%。实验结果表明,湿地中菖蒲的根系鲜重是空心菜的4.2倍,但其根系活力低于空心菜。2种植物均可在湿地中正常生长,但受湿地中营养盐浓度的限制性影响,移栽后的植物组织氮磷含量与移栽前相比下降了11.8%~20.3%。植物在净化微污染河水的潜流人工湿地中对N、P的去除起重要作用。     

Removal of trace elements in three horizontal sub-surface flow constructed wetlands in the Czech Republic

Between March 2006 and June 2008 removal of 34 trace elements was measured on a monthly basis at three horizontal-flow constructed wetlands in the Czech Republic designed to treat municipal wastewater. In general, the results indicated a very wide range of removal efficiencies among studied elements. The highest degree of removal (average of 90%) was found for aluminum. High average removal was also recorded for zinc (78%). Elements removed in the range of 50-75% were uranium, antimony, copper, lead, molybdenum, chromium, barium, iron and gallium. Removal of cadmium, tin, mercury, silver, selenium and nickel varied between 25 and 50%. Low retention (0-25%) was observed for vanadium, lithium, boron, cobalt and strontium. There were two elements (manganese and arsenic) for which average outflow concentrations were higher compared to inflow concentrations. Reduced manganese compounds are very soluble and therefore they are washed out under anaerobic conditions.     

Potential for CSO treatment with horizontal flow constructed wetlands: influence of hydraulic load,plant presence and loading frequency

This study aimed at analysing the performance of horizontal subsurface flow constructed wetlands (CWs) to treat combined sewer overflow (CSO). Four horizontal subsurface flow CWs, organized in two groups (A and B) each with a planted (Phragmites australis) and a non-planted bed, were loaded with simulated CSO, with group B receiving twice the hydraulic load of group A. Beds were monitored for pH, dissolved oxygen, conductivity, redox potential, chemical oxygen demand (COD), total suspended solids (TSS) and enterococci. Porosity variations were also estimated. Monitoring was conducted during spring and wintertime, with regular and irregular loading frequencies. Results showed an average treatment efficiency of 90–100 % for TSS, 60–90 % for COD and 2–6 log for enterococci. Removal rates were especially relevant in the first 24 h for COD and TSS. TSS and enterococci removal did not exhibit the influence of macrophytes or the applied hydraulic load while COD’s removal efficiency was lower in the higher load group and in planted beds.

     

Intensified constructed wetlands for the treatment of municipal wastewater: experimental investigation and kinetic modelling

Environmental Science and Pollution Research - This study reports organics and nutrient removal performances of the intensified constructed wetlands, i.e., tidal flow-based microbial fuel cell...     

气浮-序批式活性污泥法在客车厂废水处理中的应用

客车厂废水来源广、成分复杂,采用气浮一序批式活性污泥法(SBR工艺)处理该废水.SBR工艺不仅流程简单、运转灵活、基建费用低、脱氮除磷效果较好、污泥沉降性能良好,而且对水质和水量的适应性强、易于维护管理.出水水质达到<污水综合排放标准>(GB 8978-1996)一级排放标准.     

曝气生物滤池去除污水中邻苯二甲酸二(2-乙基己基)酯的效能

当前国内很多地方都将曝气生物滤池用于污水深度处理和回用.从保障再生水安全的角度出发,采用小试装置,对曝气生物滤池去除典型环境激素--邻苯二甲酸二(2-乙基己基)酯的效能进行了研究.结果发现,采用厚度1 000 mm的石英砂做滤料,在滤速0.5 m/h的条件下,进水邻苯二甲酸二(2-乙基己基)酯在5～35μg/L范围内时...