Factors affecting the performance of horizontal flow constructed treatment wetland vegetated with Cyperus papyrus for municipal wastewater treatment

The effect of hydraulic loading rate (HLR) and hydraulic retention time (HRT) on the bioremediation of municipal wastewater using a pilot scale subsurface horizontal flow constructed treatment wetland (HFCTW) vegetated with Cyprus papyrus was investigated. Different HLRs were applied to the treatment system namely 0.18, 0.10, and 0.07 m³/m². d with corresponding HRTs of 1.8, 3.2, and 4.7 days, respectively. The flow rate was 8 m³/d, and the average organic loading rate (OLR) was 0.037 kg BOD/m³/d. Results showed that the performance of the HFCTW was linearly affected by decreasing the HLR and increasing the HRT. The highest treatment efficiency was achieved at HRT (4.7 days) and HLR (0.07 m³/m². d). The percentage reductions of chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS) were 86%, 87%, and 80%, respectively. Satisfactory nutrient removal was obtained. Also, removal of 2–3 logs of bacterial indicators of pollution was achieved. The dry biomass of Cyperus was 7.7 kg/m² and proved to be very efficient in nitrification processes due to high diversity of the roots that increase the treatment surface area.     

人工湿地不同季节与单元之间根际微生物多样性

采用选择性平板培养基法和PCR-DGGE法比较研究了三级垂直潜流人工湿地污水处理系统中不同季节与单元之间根际微生物数量与多样性,结果表明,随着“秋-冬-春-夏”的季节的变化,2种方法测定的微生物数量都呈现“高-低-高”季节性变化现象,但选择性平板培养基法显示秋季数量最多,PCR-DGGE法显示夏季数量最多.从三级处理单元的1-3级,两种方法测定的微生物数量都呈现“低-高-低”的规律.除土样11外,其余相同季节的土样均出现聚集在同一个分支下.得到的4个差异序列(YP1-YP 4),经BLAST比较,分别找到同源性最近的已知类群,分别为肠杆菌属、弧菌、欧文氏菌、产酸克雷伯菌.BLASTX比较发现YP1与细菌代谢分解有机物有关;YP2蜡样芽胞杆菌生命活动相关,具有解磷的作用;YP3与APOE载脂蛋白e功能相似,参与细菌的分解代谢;YP4功能可能与细菌去氮有关.     

Coastal wetland management in Florida: environmental concerns and human health

High mosquito populations have always been a part of Florida??s environment. While mosquito-transmitted diseases have played a major role in Florida??s history, saltmarsh mosquitoes have not been implicated in these disease outbreaks. However, the impact of high saltmarsh mosquito numbers on the well-being of residents and visitors cannot be underestimated. Coastal wetland management efforts in Florida, which date back to the 1920s, have included ditching, dredging and filling, and impounding, all having mosquito control and environmental benefits and liabilities. In the early 1980s, efforts to encourage coastal wetlands management for both mosquito control and environmental interests came to the forefront. This resulted in the Florida Legislature creating the Florida Coordinating Council on Mosquito Control and its Subcommittee on Managed Marshes. Through the efforts of these committees, a heavy investment in research, interagency cooperation, and public acquisition of coastal wetlands property, tremendous progress has been made in management of coastal wetlands. This has occurred largely by implementing management and restoration techniques that minimize environmental impacts, allow for mosquito control, and minimize the need for pesticide use. Continued efforts are needed to place into public ownership remaining privately owned coastal wetland property to allow implementation of best management practices on these important habitats.     

Flux of organic carbon in a riverine mangrove wetland in the Florida Coastal Everglades

Short-term (daily) and seasonal variations in concentration and flux of dissolved organic carbon (DOC) were examined over 15 tidal cycles in a riverine mangrove wetland along Shark River, Florida in 2003. Due to the influence of seasonal rainfall and wind patterns on Shark River’s hydrology, samplings were made to include wet, dry and transitional (Norte) seasons. We used a flume extending from a tidal creek to a basin forest to measure vertical (vegetated soil/water column) and horizontal (mangrove forest/tidal creek) flux of DOC. We found significant (p < 0.05) variations in surface water temperature, salinity, conductivity, pH and mean concentration of DOC with season. Water temperature and salinity followed seasonal patterns of air temperature and rainfall, while mean DOC concentration was highest during the dry season (May), followed by the wet (October) and ‘Norte’ (December) seasons. This pattern of DOC concentration may be due to a combination of litter production and inundation pattern of the wetland. In contrast to daily (between tides) variation in DOC flux between the mangrove forest and tidal creek, daily variations of mean water quality were not significant. However, within-tide variation of DOC flux, dissolved oxygen content and salinity was observed. This indicated that the length of inundation and water source (freshwater vs. saltwater) variation across tidal cycles influenced water quality and DOC flux in the water column. Net DOC export was measured in October and December, suggesting the mangrove forest was a source of DOC to the adjacent tidal creek during these periods. Net annual export of DOC from the fringe mangrove to both the tidal creek and basin mangrove forest was 56 g C m⁻² year⁻¹. The seasonal pattern in our flux results indicates that DOC flux from this mangrove forest may be governed by both freshwater discharge and tidal range.     

Diatoms as indicators of isolated herbaceous wetland condition in Florida,USA

Benthic, epiphytic, and phytoplanktonic diatoms, as well as soil and water physical–chemical parameters, were sampled from 70 small (average 0.86 ha) isolated depressional herbaceous wetlands located along a gradient of human disturbance in peninsular Florida to (1) compare diatom assemblage structure between algal types; (2) develop biological indicators of wetland condition; (3) examine synecological relationships between diatom structure and environmental variables, with the ultimate goal of developing an index of biological integrity using a single assemblage. Collected diatom samples were enumerated to 250 valves and identified to species or subspecies. An assessment of wetland condition was made using a landscape-scale human disturbance score (Landscape Development Intensity index, LDI), calculated for each site using land use maps and GIS.Assemblages from both impaired and reference sites were compared using blocked multi-response permutation procedures, the percent similarity index, and visually examined using non-metric multidimensional scaling (NMDS). No ecologically significant compositional differences were found within sites. Mantel's test (Mantel's r = 0.29, p < 0.0001) and NMDS (stress: 14.52, variance: 78.5%) identified epiphytic diatoms as the most responsive to human disturbance. Strong significant correlations (|r_s| > 0.50, p < 0.05) were found between epiphytic NMDS site scores and soil pH, specific conductivity, water total phosphorous, and LDI, while soil pH, water color, soil TP, and turbidity were also significantly correlated (p < 0.05).Metrics to assess wetland condition were developed using epiphytic abundance data. Epiphytic taxa sensitive or tolerant to human landscape modification were identified using Indicator Species Analysis, and autecological indices relating diatom sensitivity to nutrients, pH, dissolved oxygen levels, saprobity, salinity, and trophic status were calculated. Fourteen final metrics were identified, scored on an ordinal scale, and combined into the Diatom Index of Wetland Condition (DIWC). The DIWC was highly correlated with the disturbance score (Spearman's r_s = −0.71, p < 0.0001), although the results need to be validated.     

Effects of shrub encroachment on the anuran community in periodically flooded grasslands of the largest Neotropical wetland

In many parts of the world, replacement of natural grasslands by woody plants has resulted in a decrease of pasture areas and in habitat loss for a variety of animal species, including amphibians. Wetlands are especially susceptible to invasive plants, both native and exotic, but the effects of such invasions on animal assemblages remain poorly understood. Here, we present information on the impact of selected environmental variables, especially coverage by the native shrub Combretum laxum Jacq., on the structure of an anuran assemblage in the Pantanal, a huge flood‐pulsed South American wetland. Anurans were surveyed during the rainy season in 17 plots, which differed in extent of C. laxum coverage, leaf litter volume, soil moisture and distance to permanently wet areas. Effects of these environmental variables on the species number, relative abundance and composition of the anuran assemblage were evaluated using multivariate statistical analyses. We captured 1203 anurans, of 21 species from four families. Both the number of species and the relative abundance of anurans were lower in plots with greater C. laxum coverage, which also influenced anuran species composition. Number of species was highest in plots located closest to permanently wet areas, which provide protection from desiccation and other resources during the Pantanal dry season, and so could be considered source areas of anurans. While many anuran species were negatively affected by the homogenization of the landscape caused by shrub encroachment, some seemed to be favoured in such circumstances. For these, dense shrub encroachment into natural grasslands may provide safer migratory routes to permanently wet habitats. Thus, at the mesoscale, a mosaic of areas with different levels of coverage by C. laxum (shrub islands) may aid anuran assemblages in the Pantanal wetlands, facilitating the maintenance of higher beta and gamma diversity.     

Limnological characteristics of a subtropical constructed wetland in south Florida (USA)

The Everglades Nutrient Removal Project (ENRP) was a 1544 ha constructed wetland built by the South Florida Water Management District as part of Everglades restoration efforts. The limnology of this wetland is characterized over its 60-month operational history. The ENRP received agricultural runoff containing high levels of C, N, P and other dissolved constituents; had moderately high alkalinity with a circumneutral pH; and had low to moderate DO. The ENRP provided substantial treatment (concentration reduction from inflow to outflow) for Al, Fe, NH₄, NO_x, SRP, TP, TSS and turbidity (high-treatment variables), while Secchi depth increased markedly. These changes were judged biologically significant. Dissolved oxygen, and water temperature had well defined annual cycles, while some level of seasonality was noted for Al, alkalinity, Ca, conductivity, DOC, Fe, hardness, K, Mg, Mn, Na, NH₄, pH, Secchi depth, SiO₂, TOC, TN, turbidity, and TSS. The ENRP was P limited based on TN:TP molar ratios. Dissolved ions were dominated by Ca, Cl, Na, and HCO₃; the stoichiometric balance of both major and minor ions was similar throughout the wetland. The downstream settling of TSS was associated with increased light penetration, but did not appear important in sediment accretion. The adsorption of P to Ca, and perhaps Al and Fe, precipitates is thought to have been an important nutrient removal mechanism. Although there was little net reduction in DOC, we speculate that some incoming material was degraded and replaced by new DOC produced within the wetland.     

Large fire initially reduces bird diversity in Poland’s largest wetland biodiversity hotspot

Biodiversity and Conservation - Freshwater wetlands are widely recognized as biodiversity hotspots for many organisms, including birds. Climate change and the projected increased risk of wetland...     

Estrogen removal from treated municipal effluent in small-scale constructed wetland with different depth

The presence of estrone (E1), 17 beta-estradiol (E2) and 17 alpha-ethynylestradiol (EE2) in sewage treatment work (STW) effluent pose a potential risk to aquatic ecosystem. The objectives of this study were to evaluate the effectiveness of vertical-flow wetland as polishing step of conventional wastewater treatment in the removal of estrogens and to examine the effect of sand depth. The highest removal efficiency of 67.8 ± 28.0%, 84.0 ± 15.4% and 75.3 ± 17.6% for E1, E2 and EE2, respectively, was achieved by the shallowest wetland among three constructed wetlands with different filter layer depth (i.e. 7.5, 30 and 60 cm). Together with the result that the performance of wetlands when operating in unsaturated condition was superior to that when operating in water-saturated condition, it is suggested that maintaining sufficient aerobic circumstance in constructed wetlands was important for estrogens removal. Core sampling indicated that the highest efficiency achieved in extremely shallow wetland might be due partly to the highest root density, besides the superior condition for penetration of oxygen. The adsorbed estrogens in sand accounted for less than 12% of the removed estrogens irrespective of the depth, indicating biotic processes play a major role in the estrogens removal.     

Effects of increased phosphorus loading on dissolved oxygen in a subtropical wetland, the Florida Everglades

The Florida Everglades is an oligotrophic, phosphorus (P)-limited wetland that is experiencing eutrophication as a result of P-enriched agricultural runoff. Effects of P enrichment on diel water-column dissolved oxygen concentration (DO) profiles were measured along nutrient gradients downstream of agricultural discharges in two northern Everglades marshes and in field enclosures (mesocosms) exposed to different P loading rates. Reference (i.e., water-column TP < 10 g/L) areas in the marsh interior were characterized by strong diel fluctuations in DO, and aerobic conditions generally were maintained throughout the diel cycle. Enriched stations (water-column TP elevated to between 12 and 131 g/L) were characterized by dampened diel fluctuations and reduced DO, and the extent of these changes was correlated strongly with marsh P concentrations. Mean DO declined from between 1.81 and 7.52 mg/L at reference stations to between 0.04 and 3.18 mg/L in highly enriched areas. Similarly, minimum DO declined from between 0.33 and 5.86 mg/L to between 0 and 0.84 mg/L with increasing enrichment, and the frequency of extremely low DO (< 1 mg/L) increased from between 0 and 20% to as high as 100% in the most enriched areas. Diel oxygen profiles in P-enriched mesocosms declined progressively with time; all loading treatments exhibited similar DO during the 1^st year of P loading, but concentrations declined significantly at higher loads by year 3. Reductions in water-column DO with increased P enrichment were associated with reduced oxygen production by submersed periphyton and macrophytes and increased sediment oxygen demand. Increased emergent macrophyte cover in enriched areas likely contributed to these changes by shading the water-column, which inhibited submerged productivity, and by providing inputs of nutrient-rich detritus, which increased oxygen demand. Declines in marsh DO are associated with other ecological changes such as increased anaerobic metabolism and an increase in invertebrate taxa that tolerate low DO. While background oxygen concentrations in wetlands can be lower than those in lakes and rivers, declines in water-column DO caused by eutrophication can result in biological impacts similar to those in other aquatic ecosystems.     

Decomposition of macrophyte litter in a subtropical constructed wetland in south Florida (USA)

The South Florida Water Management District has constructed large treatment wetlands (stormwater treatment areas (STAs)) to reduce total phosphorus concentrations in agricultural runoff before this water enters the Everglades. An important component of nutrient removal and storage in these systems is incorporation of nutrients into aquatic macrophytes and burial of this biomass in the sediments. However, decomposition of plant biomass before burial returns nutrients to the water column and may reduce STA treatment efficiency. As part of research on biogeochemical control of STA performance, we conducted a summer (July–September) and a long-term (12-month) experiment (February–February) that measured decomposition rates and release of chemical constituents from dominant aquatic macrophytes in a constructed wetland located in south Florida. The rank order of mean decomposition rates was Najas/Ceratophyllum (0.0568 d⁻¹) > Pistia (0.0508 d⁻¹) > Eichhornia (0.0191 d⁻¹) > submerged Typha (0.0059 d⁻¹) > aerial Typha (0.0008 d⁻¹). Summer decomposition rates were generally higher than rates from the long-term experiment, which suggested a temperature effect. Decomposition rates were negatively correlated with litter C:N and C:P molar ratios and cellulose and lignin content and positively correlated with N and P content. There was no significant difference in decomposition rates among sampling stations despite the fact that there was a decreasing gradient in water column inorganic phosphorus and nitrogen concentrations at these sites. Relatively little of the initial P mass remained in the litter of all species, except Typha, by the end of both experiments. First-order decomposition models derived using nonlinear regression generally had explanatory power, i.e. accounted for variance, comparable to more complex decreasing-coefficient models. Decomposition rates for the species examined in this study were within the range of published values when comparisons were made either by species or by plant group.     

Patterns of vertical stratification in a subtropical constructed wetland in south Florida (USA)

The South Florida Water Management District (District) has built large treatment wetlands, known as Stormwater Treatment Areas (STAs), to reduce excess phosphorus loading to the Everglades. The District conducted research in a prototype treatment wetland, the Everglades Nutrient Removal Project (ENRP), to study biogeochemical processes that are important to treatment performance. Vertical profile measurements of water temperature, dissolved oxygen, pH, conductivity and transmission of photosynthetically active radiation (PAR) were made in open-water areas and sites dominated by emergent, floating or submersed vegetation over an annual cycle. Relative thermal resistance to mixing was used to infer the strength of thermal stratification. Long-term diel variation in temperature at the surface and bottom of an open-water and a vegetated site also was measured. Open-water sites were nearly isothermal and had minimal thermal stratification, while vegetated sites were all thermally stratified to some degree. The highest surface water temperatures (>35 °C) occurred in submersed vegetation where much of the light absorbed by leaves and stems was reflected as heat. Oxygen was uniformly low (<4 mg L⁻¹) in emergent and floating vegetation and attributed to shading, high biological oxygen demand and limited reaeration at the surface. Depressed oxygen levels at open-water areas were attributed to high sediment oxygen demand. The highest oxygen concentrations occurred in submersed vegetation beds. Water column pH was unstratified and near circumneutral in the open water and at emergent and floating vegetation sites, while pH was markedly stratified in submersed vegetation, where surface values at times exceeded 9.0. High surface oxygen and pH levels in submersed vegetation were consistent with intense photosynthesis. Conductivity increased at the bottom of emergent and submersed vegetation but not at open-water or floating vegetation sites. PAR transmission was strongly reduced at all sites due to shading and/or absorption by dissolved organic carbon. Light extinction coefficients were markedly higher at vegetated sites compared to the open water. Peak irradiance shifted to longer wavelengths (538–643 nm) and both short (<400 nm) and long (>700 nm) wavelengths were largely attenuated at 60 cm relative to the surface. Long-term monitoring at a vegetated site revealed periods of inverse thermal stratification and dampened diel variation in temperatures at the bottom compared to open water.     

Feral swine damage to globally imperiled wetland plant communities in a significant biodiversity hotspot in Florida

We studied rooting damage during five-years of feral swine control at Avon Park Air Force Range, a significant botanical biodiversity hotspot in peninsular Florida with many globally imperiled plant species and communities. While control reduced swine abundance, remaining animals consistently rooted the 49 studied sites in both middle-dry season (MDS) and late-dry season (LDS) each year. At each study site, we measured rooting with sub-meter accuracy. Neither total nor proportional area rooted differed in either season, across study years, or among plant community types: herbaceous seepage slopes, wet pine savannas, wet grasslands. The proportion of sites with damage during MDS was at least 25 % less than pre-control baseline. During LDS, the proportion of sites with damage increased over years but remained below the initial 2 years’ MDS results. Fresh rooting frequency (rooting <1 week-old) across sites dropped precipitously from baseline and remained low for MDS. Fresh rooting frequency among sites during LDS was lower than MDS for all but year two of the study. Canopied habitat <50 m from a study site almost guaranteed rooting at the site each observation period. We propose actions for protecting wetlands, integrating swine control into other compatible land use practices, and improving swine control efficacy. While we measured damage amounts at each site very accurately, our approach of also considering frequency of rooting and frequency of fresh rooting across sites offers low-labor means to broadly assess swine damage and control efficacy at large geographic scales because in-field measurements of damage amounts are not needed.     

Rejuvenating views of the ageing process

Commonly held assumptions about the ageing process have guided and directed research in this important area over many years. Recent evidence, however, from disciplines as diverse as molecular genetics, clinical epidemiology and demography, provide a direct challenge to the validity of many of these assumptions. So, the time is ripe to re-examine these assumptions about the ageing process and to rethink the scientific foundations of the field.     

Nitrogen and phosphate mass balance in a sub-surface flow constructed wetland for treating municipal wastewater

This paper reports on the feasibility of using sub-surface horizontal flow constructed wetlands to treat municipal wastewater in Hong Kong. Two different hydraulic retention times (10-day and 5-day) and different types of treatments (with and without vegetation) were investigated. Better performance in the planted treatments was obtained in both hydraulic retention time treatments. Nutrients were better removed in treatments with plants (DOC 68% and 72%; NH₄-N 92% and 95%; TKN 65% and 62%; PO₄-P 79% and 72%; TP 67% and 52% for 10-day HRT; 5-day HRT treatments). In the unplanted treatments, negative values were achieved in the removal of phosphate in wastewater and the presence of plants could further polish the wastewater so phosphate concentrations decreased in the planted treatments. The effluent concentrations in the planted treatments meet the Inland Water A effluent standard, and they can be used in recreation park in Hong Kong (1 mg L⁻¹ of NO_x; 15 mg L⁻¹ of NH₃; 1 mg L⁻¹ of TP).     

污水渗滤湿地处理系统技术的研究进展

由于渗滤湿地污水处理系统具有很高的净化效率和相对较低的基建投资和处理成本,目前正渐渐在许多国家得到较为广泛的应用．本文简要论述了渗滤湿地的构造与渗滤介质、N和P的去除过程与净化机理、技术性能、现行的设计方法、运行与调控机制、土壤堵塞问题与解决途径、垂直流与水平流人工湿地处理系统的组合及其在不同类型废水处理中的应用等．最后,探讨了这一技术的研究发展方向．     

Life-cycle greenhouse gas emissions assessment and extended exergy accounting of a horizontal-flow constructed wetland for municipal wastewater treatment: A case study in Chile

The life-cycle greenhouse gaseous emissions and primary exergy resources consumption associated with a horizontal subsurface flow constructed wetland (HSSF) were investigated. The subject of study was a wetland for municipal wastewater treatment with a 700-person-equivalent capacity. The effects of two types of emergent aquatic macrophytes (Phragmites australis and Schoenoplectus californicus) and seasonality on greenhouse gas (GHG) gas emissions, the environmental remediation cost (ERC) and the specific environmental remediation cost (SERC) were assessed. The results indicate that GHG emissions per capita (12–22 kgCO2eq/p.e/yr) and primary exergy resources consumed (24–27 MJ/m³) for the HSSF are lower than those of a conventional wastewater treatment plant (67.9 kgCO2eq/p.e/yr and 96 MJ/m³). The SERC varied between 176 and 216 MJ/kg biological oxygen demand (BOD₅) removal, which should be further reduced by 20% for an improved BOD₅ removal efficiency above 90%. The low organic matter removal efficiency is associated with a high organic load and low bacterial development. Seasonality has a marked effect on the organic removal efficiency and the SERC, but the macrophyte species does not.