Pesticide retention in an experimental wetland treating non-point source pollution from agriculture runoff.

Pesticide losses to the environment are unwanted due to possible environmental and health hazards. An experimental wetland is established to study the efficiency with respect to retention of sediments, nutrients and pesticides. Pesticides were applied on an arable soil plot in the watershed. Statistical analyses were carried out on three selected pesticides: propachlor, metalaxyl and chlorfenvinfoss. All pesticides were found in the experimental wetland, with peak concenttrations shortly after spraying. In 2003 pesticide retention varied from 11% to 42% and in 2004 retention varied from 19% to 56%. Comparing eight different wetland filters, we found that L6 and L8, with flagstones and straw, respectively, had a higher total pesticide retention than a standard Norwegian wetland (L4). When the compounds were treated separately, however, the picture was different. Statistical analyses showed that the treatments were signficantly different from zero in six of the wetlands for remowal of propachlor, for removal of metalaxyl none were significantly different, and for removal of chlorfenvinphos four treatments were significantly different. For the three compounds none of the relative treatments were significantly different from L4. Chemical properties of the pesticides could explain some of the behaviour in the watershed and in the wetland.     

The effect of the redox-potential on the retention of phosphorus in a small constructed wetland.

Building wetlands in small arable streams is a popular supplement to best management practice on arable fields. Particle bound phosphorus settles in the small constructed wetlands (CWs), receiving agricultural diffuse pollution. The sorption behavior of phosphorus is, however, redox-sensitive, and bound phosphorus may be remobilized in periods with low redox potential. This paper investigates changes in the redox potential in the free water of wetland Berg (Norway) during a three-year period, and how these redox changes affect the total phosphorus (TP) and total reactive phosphorus (TRP) retention. Despite eutrophic conditions in the wetland, the redox potential was never negative, and usually higher than 400 mV, indicating aerobic conditions. The relative retention was 440% and 43% for TP and TRP, respectively. The specific retention was 100 g TP and 43 g TRPm(-2) yr(-1). Loss of phosphorus was only observed during less than 19% of the total period of time. The net loss was less than 5% of the specific retention. The high positive redox potential probably conserves the redox-sensitive phosphorus in the wetland sediment as long as water fows through the CW.     

Biodegradation of chlorobenzene in a constructed wetland treating contaminated groundwater.

Monochlorobenzene (MCB) is an important groundwater contaminant world-wide. In this study, a horizontal subsurface flow constructed wetland with an integrated water compartment was fed with MCB contaminated groundwater originating from the local aquifer. Analysis of spatial concentration dynamics of MCB and oxygen was combined with isotope composition analysis of MCB for assessing in situ biodegradation. Removal of MCB was most effective in the upper layer of the soil filter, reaching up to 77.1%. Trace oxygen concentrations below 0.16 mg L(-1) were observed throughout the wetland transect, suggesting a considerable limitation of aerobic microbial MCB degradation. Enrichment of 13C in the residual MCB fraction at increasing distance from the inflow point indicated microbial MCB degradation in the wetland. The observed isotope shift was higher than expected for aerobic MCB degradation and thus pointed out a significant contribution of an anaerobic degradation pathway to the overall biodegradation.     

Nitrogen dynamics in a constructed wetland system treating landfill leachate.

A pilot scale treatment system was established in 2002 at the Laflèche Landfill in Eastern Ontario, Canada. The system consists of a series of treatment steps: a stabilisation basin (10,000 m3), a woodland peat trickling filter (5,200 m2), a subsurface flow constructed wetland planted in Phragmites sp. (2,600 m2), a surface flow constructed wetland planted in Typha sp. (3,600 m2) and a polishing pond (3,600 m2). The system operates from May to December with leachate being recycled within the landfill during the winter months. Hydraulic loading was increased three-fold over four operating seasons with nitrogen and organic mass loading increasing six-fold. Excellent removal efficiencies were observed with 93% BOD5, 90% TKN and 97% NH4-N removed under the highest loading conditions. Almost complete denitrification was observed throughout the treatment system with NO3-N concentrations never exceeding 5mg L(-1). The peat filter reached treatment capacity at a hydraulic loading of 4cm d(-1) and organic loading rate of 42 kg BOD ha(-1) d(-1), which is consistent with design criteria for vertical flow wetland systems and intermittent sand filters, The first order plug flow kinetic model was effective at describing TKN and ammonium removal in the SSF and FWS wetlands when background concentrations were taken into account. Ammonium removal k-values were consistent with the literature at 52.6 and 57.7 yr(-1) for the SSF and FWS wetlands, respectively, while TKN k-values at 6.9 and 7.7 yr(-1) were almost an order of magnitude lower than literature values, suggesting that leachate TKN could contain refractory organics not found in domestic wastewater.     

Performance of constructed wetland treating wastewater from seafood industry.

Wastewater from seafood industry contains high concentrations of organic matter, nitrogen compounds, and solid matter. Constructed wetland can be used as tertiary treatment and for nutrient recycling. This research studied the performance of nitrogen and suspended solids removal efficiency of a constructed wetland treating wastewater from a seafood-processing factory located at Songkhla, southern Thailand. The existing constructed wetland has dimensions of 85 m, 352 m and 1.5 m in width, length and depth respectively, with an area of about 29,920 m2. The water depth of 0.30 m is maintained in operation with plantation of cattails (Typha augustifolia). Flow rate of influent ranged between 500-4,660 m3/d. Average hydraulic retention time in the constructed wetland was about 4.8 days. Influent and effluent from the constructed wetland were collected once a week and analyzed for pH, temperature, dissolved oxygen (DO), biochemical oxygen demand (BOD5), Suspended solid (SS), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3-N), organic nitrogen (Org-N), nitrate (NO3-N), and nitrite (NO2-N). The average removal efficiencies of BOD5, SS, TKN, NH3-N, and Org-N were 84%, 94%, 49%, 52% and 82%, respectively. It was found that the constructed wetland acting as a tertiary treatment process provided additional removal of BOD5, SS and TKN from wastewater from the seafood industry.     

Performance of a constructed wetland for treating farm-yard dirty water

Constructed wetlands (CWs) have been used to treat agricultural effluents with varying success especially with respect to their operational efficiency in winter and ability to retain phosphorus. Dirty water (DW) from dairy farms is a mixture of manure contaminated runoff and milk parlour washings with a highly polluting biochemical oxygen demand (BOD) < or =3000 mg/L. The initial performance a CW of a 1.2 ha horizontal flow CW consisting of five ponds in series designed to treat DW from a dairy unit was assessed over four years. Ponds were earth-lined and shallow (0.3 m) with a water residence time of 100 days and planted with five species of emergent macrophytes. In comparison to CW inflow, annual reductions were as follows: BOD 99%, P 95% and N 92.8%. Coliforms were reduced by a 10(-5) factor to natural levels. From May to October there was little CW discharge due to evaporative losses. Final effluent quality was poorest in February but remained within a regulatory effluent standard for BOD of 40 mg/L. If the CW had only four ponds (25% less surface area) effluent would have failed the BOD standard in three years.     

The next step--incorporating diffuse pollution abatement into watershed management.

The majority of adverse changes in watersheds impairing water quality occurred over a period of thirty to more than one hundred years. In many areas over a period of about 80 years more than 90% of the wetlands were drained, cultivated and converted to agricultural and urban uses. This conversion changed the redox status of the soils and soil cover with a concurrent large increase of suspended solids, dissolved organic matter, nitrogen, and phosphate loads from the watersheds located in the affected regions. The question whether these adverse changes are reversible by reduction or discontinuation of excessive inputs of pollutants came to light and has been analyzed recently after the political changes in Eastern Europe. Reliable dynamic long term models that would describe interactions between nutrient inputs, outputs, storage etc., have not been developed yet. It is becoming apparent that it may take longer for the watersheds to recover after nutrient loads to surface and groundwater are reduced if remedial measures are gradually implemented.     

Applicability of modelling tools in watershed management for controlling diffuse pollution.

Diffuse pollution is hard to analyze, control and manage by its nature. Watershed models and Geographical Information Systems (GIS) are recently developed tools that aid analysis of diffuse sources of pollution. However, their applications are not always easy and straightforward. Turkey is a typical example of a mountainous country rich in rivers and streams. Due to the complex geomorphology, land-use and agricultural practices in most of the watersheds in Turkey, modelling, analyzing and managing diffuse pollution has been a challenge. The complex watershed structure forces the modellers to work with spatially high resolution data. Apart from the data, the models themselves may also cause operational problems. These issues and their probable solutions form the basis of the discussions in this paper. It acts as a guideline for modelling and analyzing diffuse pollution by emphasizing the referred problems and difficulties. Design of an Information Technology-based system tool for watershed and/or water quality modelling, which would be suitable for countries having watersheds with similar structure and problems to those of Turkey, is also outlined.     

Comparison of nutrient cycling in a surface-flow constructed wetland and in a facultative pond treating secondary effluent.

There is a growing interest in the possibilities offered by combinations of waste stabilisation ponds (WSP) and constructed wetlands (CW). The purpose of our study was to compare treatment performances and nutrient cycling in a surface-flow wetland (SFW) and in a WSP treating secondary effluent. In the period between 2000 and 2003, a pilot SFW and a pilot WSP were constructed at the outlet of the wastewater treatment plant and their performance monitored while both were active under the same conditions. The SFW was planted with Phragmites australis and Eichhornia crassipes, while in the WSP development of algae was spontaneous. Performance efficiency was monitored by means of evaluation of physical and chemical parameters in water, by measurement of plant productivity and by analysis of N and P contents in biomass. The SFW with macrophytes proved more efficient in decreasing the suspended solids (64.6%), settleable solids (91.8%), organic N (59.3%), total N (38%), COD (67.2%) and BOD5 (72.1%) than the WSP. The WSP with algae was more efficient in treatment of ammonia nitrogen (48.9%) and ortho-phosphate (43.9%). The results of this study provide data that are of help in optimising combinations of SFW and WSP.     

Nitrogen removal and ammonia-oxidising bacteria in a vertical flow constructed wetland treating inorganic wastewater

Nitrogen removal performance and the ammonia-oxidising bacterial (AOB) community were assessed in the batch loaded 1.3 ha saturated surface vertical flow wetland at CSBP Ltd, a fertiliser and chemical manufacturer located in Kwinana, Western Australia. From September 2008 to October 2009 water quality was monitored and sediment samples collected for bacterial analyses. During the period of study the wetland received an average inflow of 1,109 m3/day with NH3-N = 40 mg/L and NO3-N = 23 mg/L. Effluent NH3-N and NO3-N were on average 31 and 25 mg/L, respectively. The overall NH3-N removal rate for the period was 1.2 g/m2/day indicating the nitrifying capacity of the wetland. The structure of the AOB community was analysed using group specific primers for the ammonia monooxygenase gene (amoA) by terminal restriction fragment length polymorphism and by clone libraries to identify key members. The majority of sequences obtained were most similar to Nitrosomonas sp. while Nitrosospira sp. was less frequent. Another two vertical flow wetlands, 0.8 ha each, were commissioned at CSBP in July 2009, since then the wetland in this study has received nitrified effluent from these two new cells.     

Potential nitrification and denitrification and the corresponding composition of the bacterial communities in a compact constructed wetland treating landfill leachates.

Constructed wetlands can be used to decrease the high ammonium concentrations in landfill leachates. We investigated nitrification/denitrification activity and the corresponding bacterial communities in landfill leachate that was treated in a compact constructed wetland, Tveta Recycling Facility, Sweden. Samples were collected at three depths in a filter bed and the sediment from a connected open pond in July, September and November 2004. Potential ammonia oxidation was measured by short-term incubation method and potential denitrification by the acetylene inhibition technique. The ammonia-oxidising and the denitrifying bacterial communities were investigated using group-specific PCR primers targeting 16S rRNA genes and the functional gene nosZ, respectively. PCR products were analysed by denaturing gradient gel electrophoresis and nucleotide sequencing. The same degree of nitrification activity was observed in the pond sediment and at all levels in the filter bed, whereas the denitrification activity decreased with filter bed depth. Denitrification rates were higher in the open pond, even though the denitrifying bacterial community was more diverse in the filter bed. The ammonia-oxidising community was also more varied in the filter bed. In the filter bed and the open pond, there was no obvious relationship between the nitrification/denitrification activities and the composition of the corresponding bacterial communities.     

强化混凝—人工湿地处理小城镇污水

介绍了强化混凝与人工湿地的处理机理;采用强化混凝—人工湿地相结合解决了小城镇污水处理率低的问题．为小城镇污水处理提供了技术要求和保证。最后指出强化混凝—人工湿地具有的各种优缺点并进行展望。     

强化混凝-人工湿地处理小城镇污水

介绍了强化混凝与人工湿地的处理机理;采用强化混凝—人工湿地相结合解决了小城镇污水处理率低的问题．为小城镇污水处理提供了技术要求和保证。最后指出强化混凝—人工湿地具有的各种优缺点并进行展望。     

含镉废水人工湿地处理系统中基质微生物数量和酶活性研究

构建了美人蕉-红蛋(MH)和彩叶草-风车草(CF)两种不同植物组合的复合垂直流人工湿地系统,以不种植物的垂直流人工湿地系统(CK)为对照,研究不同湿地系统基质微生物数量和酶活性及其与无机废水中镉的去除效果的相关性。结果表明,在不同的植物系统中,微生物数量和酶活性为:MHCFCK;在同一个湿地系统中为下行池大于上行池;在有植物的系统中其微生物数量和酶活性的垂直分布为0~5 cm5~15cm15~20 cm;基质中真菌、放线菌数量和蔗糖酶活性与镉去除率呈显著正相关,而细菌数量和脲酶活性与镉去除率相关性不显著。     

Diversity of ammonia oxidising bacteria in a vertical flow constructed wetland.

Vertical flow constructed wetlands (VFCWs) with intermittent loading are very suitable for nitrification. Ammonia oxidising bacteria (AOB) are the limiting step of nitration. Therefore the AOB community of a full-scale VFCW, receiving municipal wastewater, was investigated within this study. The diversity of the functional gene encoding the alpha-subunit of the ammonia monooxygenase (amoA), present only in AOB, was assessed by denaturing gradient gel electrophoresis (DGGE). Only very few amoA sequence types dominated the wetland filter substrate; nevertheless a stable nitrification performance could be observed. During the cold season the nitrification was slightly reduced, but it has been shown that the same AOB could be identified. No spatial AOB pattern could be observed within the filter body of the VFCW. The most prominent bands were excised from DGGE gels and sequenced. Sequence analyses revealed two dominant AOB lineages: Nitrosomonas europaea/"Nitrosococcus mobilis" and Nitrosospira. Species of the Nitrosomonas lineage are commonly found in conventional wastewater treatment plants (WWTPs). In contrast, members of the Nitrosospira lineage are rarely present in WWTPs. Our observations indicate that the AOB community in this VFCW is similar to that found in horizontal flow constructed wetlands, but differs from common WWTPs regarding the presence of Nitrosospira.     

Exploring fecal indicator bacteria in a constructed stormwater wetland

Microbial pollution in surface waters is a concern throughout the world, with both public health and economic implications. One contributing source to such pollution is stormwater runoff, often treated using various types of stormwater control measures. However, relatively little is known regarding microbe sequestration in constructed stormwater wetlands (CSWs), one type of commonly installed stormwater control measure. In this study, indicator bacteria concentrations in both the water and sediment of a CSW were evaluated at multiple locations. Results suggested that fecal coliform concentrations in stormwater runoff decrease through the system, with relatively consistent concentrations noted throughout the second half of the wetland. This potentially indicates a baseline concentration of fecal coliform is present due to internal processes such as animal activity and microbial persistence. However, wetland sediments showed little E. coli present during most sampling events, with minimal patterns existing with respect to sediment sampling location. CSW designs should promote optimization of hydraulic retention time and minimization of stormwater velocities to promote sedimentation and degradation of microbes by way of wetland treatment functions.     

Temperature,redox, and amendments alter wetland soil inorganic phosphorus retention dynamics in a Laurentian Great Lakes priority watershed

Surface water phosphorus loading must be reduced to improve water quality and decrease harmful algal blooms. Many wetlands have a natural capacity to retain inorganic reactive PO₄^3? via soil sorption. However, soil PO₄^3? retention capacity is finite and may be limited by soil legacy phosphorus effects in agricultural and urban areas. This study evaluated soil PO₄^3? retention in soils from a wetland constructed on former agricultural land in the Lake Erie, Maumee River watershed targeted for nutrient load reduction. Soil PO₄^3? sorption isotherms were evaluated under cool (10 °C), warm (22°), aerobic, and anaerobic treatments to determine changes in PO₄^3? retention due to environmental conditions and estimate seasonal changes in PO₄^3? sorption. The soils displayed a strong capacity for PO₄^3? retention by sorption. However, results indicate that cooler temperatures and anaerobic conditions decreased PO₄^3? sorption and lowered retention rates at PO₄^3? concentrations observed in the region. Soil amendment experiments investigated opportunities to increase PO₄^3? retention because many soils display elevated phosphorus concentrations due to historic land use, limiting their ability to adsorb additional PO₄^3?. Amendments increased PO₄^3? retention capacity compared to unamended soils in the presence of high PO₄^3? concentrations, suggesting soil PO₄^3? retention can be improved in areas where natural storage capacity has been exhausted. Results from this study can inform natural resources managers in the Laurentian Great Lakes and elsewhere when identifying potential nutrient reduction wetland locations and assist with developing operational guidelines to optimize PO₄^3? retention and water quality improvements using wetlands.     

人工湿地基质细菌多样性研究

分别采用PCR-RFLP和高通量测序方法,分析自由表面流人工湿地基质细菌多样性。2种方法均显示人工湿地基质中细菌主要分布在变形菌门,其中γ-变形菌纲和β-变形菌纲属优势菌群,其次为δ-变形菌纲、α-变形菌纲、厚壁菌门中的芽孢杆菌纲及酸杆菌门中的酸杆菌纲。但在优势种属水平上,2种分析方法得到的结果差异较大。人工湿地基质中存在亚硝化螺菌属、硝化螺旋菌属、Thioalkalivibrio、不动杆菌属、假单胞菌属、放线菌属、海旋菌、海单胞菌属及鞘脂菌属等参与脱氮除磷和降解有机污染物的微生物种类;同时也存在绿脓杆菌、弧菌属及黄杆菌属等致病菌或条件致病菌。研究也说明,PCR-RFLP和高通量测序法对湿地基质微生物多样性分析显示出了方法的优越性。     

Nitrogen management in reservoir catchments through constructed wetland systems.

In this study, nitrogen removal was investigated in pilot-scale subsurface flow (SSF) and in free water surface flow (FWS) constructed wetlands installed in the campus of TUBITAK-Marmara Research Center, Gebze, near Istanbul, Turkey. The main purposes of this study are to apply constructed wetlands for the protection of water reservoirs and to reuse wastewater. Experiments were carried out at continuous flow reactors. The effects of the type of plants on the removal were investigated by using emergent (Canna, Cyperus, Typhia spp., Phragmites spp., Juncus, Poaceae, Paspalum and Iris.), submerged (Elodea, Egeria) and floating (Pistia, Salvina and Lemna) marsh plants at different conditions. During the study period HLRs were 30, 50, 70, 80 and 120 L m(2)d(-1) respectively. The average annual NH4-N, NO(3)-N, organic N and TN treatment efficiencies in SSF and FWS wetlands are 81% and 68%, 37% and 49%, 75% and 68%, 47% and 53%, respectively. Nitrification, denitrification and ammonification rate constant (k20) values in SSF and FNS systems have been found as 0.898 d(-1) and 0.541 d(-1), 0.488 d(-1) and 0.502 d(-1), 0.986 d(-1) and 0.908 respectively. Two types of the models (first-order plug flow and multiple regression) were tried to estimate the system performances.