人工湿地系统微生物去除污染物的研究进展

人工湿地污水处理系统具有净化效果显著、建设和运行费用低廉、管理简便等优点,近年来越来越受到人们的重视。人工湿地是利用介质、植物和微生物构成的复合系统来处理污水。微生物在人工湿地系统净化污水过程中发挥着重要作用。介绍了人工湿地系统中微生物去除污染物的研究进展,重点讨论了人工湿地对污染物和特殊有机污染物的去除以及系统基质中微生物的种群和活性等内容,并结合我国研究现状展望了该领域的研究前景。人工湿地系统微生物对污染物去除将成为人工湿地生态系统服务功能评价、人工湿地生态系统健康与稳定的诊断的重要组成部分。     

粉煤灰合成沸石去除城市暴雨径流中氨氮

采用粉煤灰为原料,通过耦合碱熔-两步合成法制得3种合成沸石产品,并以合成沸石制备大粒径的功能填料。通过氨氮吸附速率实验和等温吸附实验探讨了合成沸石及功能填料的氨氮吸附速率和最大吸附容量(Qm),以功能填料构建模拟人工快速渗滤系统,研究其对城市暴雨径流中氨氮的去除效果。结果表明,合成沸石对氨氮的吸附速率极快,5min去除率约达到75%,氨氮最大吸附容量为11.36～16.13 mg/g;功能填料对氨氮的最大吸附容量有所下降,但氨氮吸附速率仍较快,应用于模拟人工快速渗滤系统时能在较高的水力负荷下快速去除城市暴雨径流中的氨氮。碱处理再生法更适于进行合成沸石功能填料原位再生,氨氮吸附容量一次再生率达到67%～87%。     

Physiological parameters of plants as indicators of water quality in a constructed wetland

Introduction  

Increasing demand for water has stimulated efforts to treat wastewater for reuse in agriculture. Decentralized facilities for wastewater treatment became popular as a solution to remote and small communities. These systems mimic natural wetlands, cleaning wastewater as they flow through a complex of filter media, microbial fauna, and vegetation. The function of plants in constructed wetlands (CWs) has not been fully elucidated yet.     

Characterizing the passage of personal care products through wastewater treatment processes.

Wastewater treatment facilities use secondary treatment to stabilize the effect of discharged effluent on receiving waters by oxidizing biodegradable organic matter and reducing suspended solids and nutrients. The process was never specifically intended to remove trace quantities of xenobiotics, such as endocrine-disrupting compounds (EDCs) and pharmaceuticals and personal care products (PPCPs). Nevertheless, European studies performed at bench-scale or at small facilities have demonstrated that a critical minimum solids retention time (SRT) can achieve good reduction of many EDCs and pharmaceuticals. The objective of this study was to expand these findings to the removal performance for 20 PPCPs commonly found in the influent to full-scale facilities operating in the United States. The participating plants use SRT conditions ranging from 0.5 to 30 days and include facility capacities ranging from 19 000 m3/d (5 mgd) to greater than 1 136 000 m3/d (300 mgd). Two pilot membrane bioreactors were also included in the study. The 20 PPCPs were categorized into nine bin combinations of occurrence frequency and treatment reduction performance. While most compounds were well removed, galaxolide (a musk fragrance) occurred frequently and was resistant to removal. A minimum critical SRT, defined as the minimum SRT, needed to consistently demonstrate greater than 80% removal (SRT80), was compound-dependent, with most compounds removed at 5 to 15 days and a small group requiring longer SRTs. From limited data, no additional removal could be attributed to the use of membrane bioreactors, media filters, or longer hydraulic retention times. Reverse osmosis was effective in removing any remaining compounds.     

Wastewater treatment using bamboos in constructed wetlands: experiences and future perspectives

Environmental Science and Pollution Research - Wastewater treatment using constructed wetlands (CWs) based on natural wetlands constitute a viable alternative with excellent cost and benefit,...     

Experimental analysis and modeling of a stormwater perlite filter

This paper presents the study of a mixed porous media composed of expanded perlite and a nonwoven needle-punched geotextile used to reduce the suspended solids load and concentration in urban runoff. Laboratory procedures were designed to quantify the suspended solids removal efficiency and variation in time of filtration rate. Different grain-size distributions of expanded perlite, diverse suspended solids concentrations, and different hydraulic and geometric conditions were tested to determine the most effective filter media. A dimensionless parameter, termed Global Performance Index (GPI), was developed to reach this objective. Measured data were also used to build a dimensional and a regression model to represent the performance of the filter media mathematically. The theory, derivation, and performance of both models are presented and compared with an existent empirical model. The dimensional model better reproduces the observations, becoming a useful tool for the design, operation, and evaluation of commercial porous media filters.     

Urban stormwater quality control analysis with detention ponds.

This paper presents methodologies for the development of stormwater quality control measures based on the derived probability distribution approach. These stormwater control measures, such as the fraction of pollutant removed from storage facilities, are closed-form analytical models and can be effectively used to evaluate pollutant loads to receiving waters. In this study, a simple form of rainfall-runoff transformation with lumped parameters is first extended to take into account the spatial variations in model parameters. Second, the infiltration process is further incorporated to the rainfall-runoff transformation. This study demonstrates that analytical models can be developed with various levels of complexity based on different hydrologic considerations. The performance of the analytical models is evaluated in a case study, and the results indicate that, with an appropriately formulated rainfall-runoff transformation, analytical stormwater runoff models are capable of providing comparable results to continuous simulation models in the evaluation of the long-term performance of storage facilities.     

复合人工湿地对城市受污染河水的净化效果

采用2种复合人工湿地系统处理昆明市城市河流污水,为期1年的运行结果表明:2种复合人工湿地系统对城市河流污水具有良好的污染物去除性能,TN、TP、COD和SS的月平均去除率分别达到50%、85%、85%和80%以上;2种复合人工湿地系统具有良好的耐冲击性,季节变化对出水水质不存在显著影响。其中,垂直上行流复合人工湿地系统性能更优于垂直上行流与水平流复合人工湿地系统;强降雨会对复合人工湿地出水水质造成一定的影响。     

Constructed wetlands as a component of the agricultural landscape: mitigation of herbicides in simulated runoff from upland drainage areas

Constructed wetlands are a recommended practice for buffering pollutant source areas and receiving waters. A wetland consisting of a sediment trap and two treatment cells was constructed in a Mississippi Delta lake watershed. A 3-h simulated runoff event was initiated (2003) to evaluate fate and transport of atrazine and fluometuron through the wetland. Water samples were collected during a runoff simulation and then afterward at selected intervals for 21 d, and analyzed for the herbicides. Breakthrough patterns for herbicide concentrations in water samples during the first 20 h after simulated runoff showed peak concentrations in the first 6 h, with gradual tailing as the herbicide pulse was diluted in the second, excavated (deeper) cell. Atrazine and fluometuron concentrations in the first (shallower, non-excavated) cell averaged 12- and 20-fold greater, respectively, than those in the second cell following simulated runoff, indicating entrapment in the first cell. Atrazine and fluometuron concentrations in the shallower cell decreased 32% and 22%, respectively, 9 d following simulated runoff, indicating either degradation or sorption to soil or wetland flora. In the excavated cell, concentrations were even lower, and atrazine declined more rapidly than fluometuron. Results indicate constructed wetlands can improve downstream water quality though sequestration or processing of pollutants.     

Growth of Phragmites australis (Cav.) Trin ex. Steudel in mine water treatment wetlands: effects of metal and nutrient uptake

The abandoned mine of Shilbottle Colliery, Northumberland, UK is an example of acidic spoil heap discharge that contains elevated levels of many metals. Aerobic wetlands planted with the common reed, Phragmites australis, were constructed at the site to treat surface runoff from the spoil heap. The presence of a perched water table within the spoil heap resulted in the lower wetlands receiving acidic metal contaminated water from within the spoil heap while the upper wetland receives alkaline, uncontaminated surface runoff from the revegetated spoil. This unique situation enabled the comparison of metal uptake and growth of plants used in treatment schemes in two cognate wetlands. Results indicated a significant difference in plant growth between the two wetlands in terms of shoot height and seed production. Analyses of metal and nutrient concentrations within plant tissues provided the basis for three hypotheses to explain these differences: (i) the toxic effects of high levels of metals in shoot tissues, (ii) the inhibition of Ca (an essential nutrient) uptake by the presence of metals and H+ ions, and (iii) low concentrations of bioavailable nitrogen sources resulting in nitrogen deficiency. This has important implications for the engineering of constructed wetlands in terms of the potential success of plant establishment and vegetation development.     

Removal of PAHs from laboratory columns simulating the humus upper layer of vertical flow constructed wetlands

Removal of three polycyclic aromatic hydrocarbons or PAHs (fluoranthene, pyrene and benzo(k)fluoranthene) from two types of PAH-contaminated effluents was investigated using four laboratory columns filled with two different organic media: a green compost and a layer coming from the first stage of vertical flow constructed wetlands. Synthetic runoff polluted by polycyclic aromatic hydrocarbons were fed through the columns during a period of two months. After a period of hydrodynamic stabilisation, the results showed a great adsorption of PAHs (>95%) on the solid media due to their large adsorption capacities. Leaching of these compounds by water was monitored. The concentrations of PAHs in leaching samples indicated that PAHs were strongly adsorbed on organic substrates and that lixiviation was limited. Fluoranthene metabolites were also investigated. Accumulation of metabolites was transitory and located in the first few cm of the media, as was observed for PAH concentrations. A toxicity test of leachates based on the inhibition of the bioluminescence of luminescent bacteria Vibrio fischeri indicated a low inhibition which can be enhanced by metal traces.     

Feasibility of constructed wetlands for removing chlorothalonil and chlorpyrifos from aqueous mixtures

Chlorpyrifos (an insecticide) and chlorothalonil (a fungicide) are transported in stormwater runoff and can be lethal to receiving aquatic system biota. This study determined removal rates of chlorpyrifos and chlorothalonil in simulated stormwater runoff treated in constructed wetland mesocosms. Using sentinel species, Ceriodaphnia dubia and Pimephales promelas, observed declines in toxicity of the simulated runoff after treatment were 98 and 100%, respectively. First order removal rates were 0.039/h for chlorpyrifos and 0.295/h for chlorothalonil in these experiments. Constructed wetland mesocosms were effective for decreasing concentrations of chlorpyrifos and chlorothalonil in simulated stormwater runoff, and decreasing P. promelas and C. dubia mortality resulting from these exposures. The results from this study indicate that constructed wetlands could be part of an efficient mitigation strategy for stormwater runoff containing these pesticides.     

Design of a cost-effective weighing facility for PM2.5 quality assurance

The U.S. Environmental Protection Agency (EPA) Quality Assurance (QA) Guidance Document 2.12: Monitoring PM2.5 in Ambient Air Using Designated Reference or Class I Equivalent Methods (Document 2.12) requires conditioning of PM2.5 filters at 20-23 degrees C and 30-40% relative humidity (RH) for 24 hr prior to gravimetric analysis. Variability of temperature and humidity may not exceed +/-2 degrees C and +/-5% RH during the conditioning period. The quality assurance team at EPA Region 2's regional laboratory designed a PM2.5 weighing facility that operates well within these strict performance requirements. The traditional approach to meeting the performance requirements of Document 2.12 for PM2.5 filter analysis is to build a walk-in room, with costs typically exceeding $100,000. The initial one-time capital cost for the laboratory at EPA's Edison, NJ, facility was approximately $24,000. Annual costs [e.g., National Institute of Standards and Technology (NIST) recertifications and nitrogen replacement cylinders used for humidity control] are approximately $500. The average 24-hr variabilities in temperature and RH in the Region 2 weighing chamber are small, +/-0.2 degrees C and +/-0.8% RH, respectively. The mass detection limit for the PM2.5 weighing system of 47-mm stretched Teflon (lab blank) filters is 6.3 microg. This facility demonstrates an effective and economical example for states and other organizations planning PM2.5 weighing facilities.     

Sulphur transformation and deposition in the rhizosphere of Juncus effusus in a laboratory-scale constructed wetland

Sulphur cycling and its correlation to removal processes under dynamic redox conditions in the rhizosphere of helophytes in treatment wetlands are poorly understood. Therefore, long-term experiments were performed in laboratory-scale constructed wetlands treating artificial domestic wastewater in order to investigate the dynamics of sulphur compounds, the responses of plants and nitrifying microorganisms under carbon surplus conditions, and the generation of methane. For carbon surplus conditions (carbon:sulphate of 2.8:1) sulphate reduction happened but was repressed, in contrast to unplanted filters mentioned in literature. Doubling the carbon load caused stable and efficient sulphate reduction, rising of pH, increasing enrichment of S(2-) and S(0) in pore water, and finally plant death and inhibition of nitrification by sulphide toxicity. The data show a clear correlation of the occurrence of reduced S-species with decreasing C and N removal performance and plant viability in the experimental constructed wetlands.     

Hydraulic response and nitrogen retention in bioretention mesocosms with regulated outlets: part I--hydraulic response

In bioretention systems used for stormwater treatment, runoff interception improves with increased infiltration rates. However, nitrogen retention improves with increased retention time or decreasing infiltration rates. These contrasting responses were analyzed in 240-L experimental mesocosms using a variety of media treatments. The mesocosms were vegetated, except for one barren control. Dual-stage outlets were installed to extend retention time and equalize hydraulic responses. One unregulated treatment was free-draining. This part 1 paper presents the media properties and hydraulic responses. The highly aggregated media had saturated hydraulic conductivities ranging from 20.7 to 59.6 cm/h in August 2008 (austral winter), which increased to 42.8 to 110.6 cm/h in March 2009 (austral summer). The outlet regulated mesocosms provided retention over 8 times longer than the free-draining mesocosms, while still being able to capture large events. The outlets provide adaptive management for bioretention design to improve both runoff capture and nitrogen retention.     

人工湿地构筑根孔作用下土壤物质分布状况

嘉兴市石臼漾湿地应用人工构筑根孔技术,以玉米秸秆和油菜秸秆按比例混合埋植于土壤亚表层,作为湿地的基质/填料。在湿地运行一年半后,按照正交设计表,以埋植秸秆的种类(S)、填埋的土壤层次(L)、距离秸秆外环的远近(D)和秸秆周围土壤的表观颜色(C)作为实验因素,对秸秆周围养分物质浓度、土壤酶活性以及铁含量进行采样分析。实验结果显示:玉米秸秆和油菜秸秆腐烂较充分,分别形成较发达的粗根孔和细根孔;根孔周围土壤呈中度还原状态;粗根孔具有较强的优先流效应,其周围土壤具有较高的养分物质含量和较低的Fe2+/Fe3+比。粗根孔周围土壤具有较高的磷酸酶活性,而细根孔周围具有较高的β-葡糖苷酶活性和脲酶活性。综合比较,人工湿地构建初期,径级较大秸秆腐烂后形成的粗根孔发挥着更高的水分传导效率和更强的物质截留效应。     

Nitrogen transformations modeling in subsurface-flow constructed wetlands.

Subsurface-flow constructed wetlands (CWs) wastewater treatment typically results in satisfactory organics removal. However, the removal of nutrients, particularly nitrogen, is often unreliable, and typically less than desired, and nitrogen transformations in wetlands systems are not well-understood. The principal objective of this study was to establish a basis for quantification of nitrogen transformations through subsurface flow CW systems. Actual performance data from a full-scale facility located near Lincoln, Nebraska, were used to calibrate a proposed nitrogen transformations model, which, in turn, was used to replicate and predict the wetlands performance. To realize this objective, a compartmental analysis technique, which uses a set of differential equations and nonlinear optimization numerical methods, was used for solving nitrogen transformation rates and for predicting wetland performance. The model satisfactorily reproduced the mean effluent concentrations for organic nitrogen, ammonium-nitrogen, and nitrate-nitrogen, but with lesser accuracy with respect to peak high and low effluent concentrations. Nitrogen mass balance in the wetland was used to identify likely nitrogen transformation pathways. Generally, it was found that approximately one-third of the influent nitrogen mass was removed through nitrification and denitrification, one-third was removed through vegetative assimilation, and the remainder was discharged in the wetland effluent.     

Constructed wetlands for mitigation of atrazine-associated agricultural runoff

Atrazine was amended into constructed wetlands (59-73x14x0.3 m) for the purpose of monitoring transport and fate of the pesticide to obtain information necessary to provide future design parameters for constructed wetlands mitigation of agricultural runoff. Following pesticide amendment, a simulated storm and runoff event equal to three volume additions was imposed on each wetland. Targeted atrazine concentrations were 0 microg/l (unamended control), 73 microg/l, and 147 microg/l. Water, sediment, and plant samples were collected weekly for 35 days from transects longitudinally distributed throughout each wetland and were analyzed for atrazine using gas chromatography. Between 17 and 42% of measured atrazine mass was within the first 30-36 m of wetlands. Atrazine was below detection limits (0.05 microg/kg) in all sediment and plant samples collected throughout the duration of this study. Aqueous half lives ranged from 16 to 48 days. According to these data, conservative buffer travel distances of 100-280 m would be necessary for effective runoff mitigation.     

Hydroponic root mats for wastewater treatment—a review

Hydroponic root mats (HRMs) are ecotechnological wastewater treatment systems where aquatic vegetation forms buoyant filters by their dense interwoven roots and rhizomes, sometimes supported by rafts or other floating materials. A preferential hydraulic flow is created in the water zone between the plant root mat and the bottom of the treatment system. When the mat touches the bottom of the water body, such systems can also function as HRM filter; i.e. the hydraulic flow passes directly through the root zone. HRMs have been used for the treatment of various types of polluted water, including domestic wastewater; agricultural effluents; and polluted river, lake, stormwater and groundwater and even acid mine drainage. This article provides an overview on the concept of applying floating HRM and non-floating HRM filters for wastewater treatment. Exemplary performance data are presented, and the advantages and disadvantages of this technology are discussed in comparison to those of ponds, free-floating plant and soil-based constructed wetlands. Finally, suggestions are provided on the preferred scope of application of HRMs.     

Performance comparison of structural stormwater best management practices.

This paper describes a method for comparing the pollutant removal of a number of structural stormwater treatment devices, commonly referred to as best management practices (BMPs). Historically, the pollutant removal ability of a BMP has been expressed as a percent reduction in concentration or load. Unfortunately, the calculated percent reduction in pollutant concentration is strongly affected by the influent concentration, with the calculated reduction generally being much lower when the event mean concentrations (EMCs) in the untreated runoff from the test watershed are low. The objective of the proposed methodology is to eliminate this problem by predicting BMP performance for an arbitrary influent concentration, so that BMPs evaluated in different watersheds can be compared as if the influent quality at all sites were the same. This method allows BMPs to be compared based on the quality of effluent produced and the mass reduction. The proposed method uses linear regression as the primary tool to compute the expected effluent concentration from a BMP, given a specific influent concentration of interest and was developed using data collected in the California Department of Transportation BMP Retrofit Pilot Program. This technique reveals that for media filters, the concentration of sediment and other particle-associated pollutants in treated runoff is generally unrelated to influent quality and is relatively constant. Wet basins with large permanent pool volumes also have effluent concentrations that are constant for most constituents and unrelated to influent concentrations. In these situations, the "percent reduction" in a pollutant EMC is not an inherent characteristic of the BMP, but a function of the influent EMC, because the quality of effluent produced is constant. Predicting the effluent quality of several types of conventional BMPs based on a common influent concentration allows an objective comparison of their performance and the selection of a BMP that addresses specific constituents of concern.