Wet Land Project

OMTEX CLASSES PROJECT ON WETLAND

Wetland Wetland Table of Contents •

1 Introduction

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2 Types of wetlands

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3 Wetland Categories

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4 Ecological roles of wetlands

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5 Economic benefits of wetlands

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5.1 Water Quality and Hydrology

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5.2 Flood Protection

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5.3 Shoreline Erosion

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5.4 Fish and Wildlife Habitat

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5.5 Natural Products for Our Economy

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5.6 Recreation and Aesthetics

6 Human impacts on wetlands ○

6.1 Hydrologic Alterations

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6.2 Pollution Inputs

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6.3 Vegetation Damage

7 Further Reading

Lead Author: Harold Ornes (other articles) Content Source: Environmental Protection Agency (other articles) Article Topic: Wetlands This article has been reviewed and approved by the following Topic Editor: Cutler J. Cleveland (other articles) Last Updated: November 6, 2008

Introduction The following information focuses primarily on freshwater, inland wetlands and provides brief information about tidal, coastal, estuarine wetlands. It is important to note, that whether inland or coastal, there are several federal agencies that have special interest in and jurisdiction over wetlands and therefore it is important to define some terms and phrases throughout this article. Our intent is to provide the reader who might have special interest in wetland delineation, wetland mitigation, wetland biology, etc. with information or references to additional information that will be helpful.

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Suisun Marsh wetlands. (Source: California Interagency Ecological Program, Suisun Marsh Program) The U. S. Army Corps of Engineers and the Environmental Protection Agency (EPA) in the originally published 1987 Corps of Engineers Wetlands Delineation Manual jointly defined wetlands as: “Those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.” They continue to describe specifics of the three core components that constitute whether or not an area is a wetland, i.e., Vegetation, Soil, and Hydrology. Page 2 of the Manual states that “This report should be cited as follows: Environmental Laboratory. 1987. “Corps of Engineers Wetlands Delineation Manual”, Technical Report Y-87-1, US Army Engineer Waterways Experiment Station, Vicksburg, Miss.” To access an electronic version, see Further Reading. The U.S. Federal Highway Administration has interest in the location, form, and function of wetlands due to highway construction and maintenance. Their policy memoranda from 1994 refers and defers to the Soil Conservation Service (SCS), the Environmental Protection Agency (EPA), and the Corps of Engineers (COE) (see Further Reading). State government agencies often have special considerations regarding wetland delineations. The state of Florida, for example, often has public, state, and federal interests that require careful attention to issues that relate to wetlands. Therefore, special definitions for Hydric soils, Delineation of Wetlands, and Hydrophytic vegetation may be found on their website (see Further Reading). Numerous books are dedicated to plants and animals found in wetlands. Birds and vegetation, for example, are some of the most recognizable, distinguishable features in a wetland landscape, and therefore books may focus on the identification of such birds and plants. The Audubon Society uses the U.S. Fish and Wildlife Service definition in The Audubon Society Nature Guides “Wetlands” by William A. Niering (see Further Reading). From all of these sources, the common elements of wetlands include water on the surface or under (but near) the surface for sufficient lengths of time that the area is dominated by hydric soils and organisms that are sustained by and physiologically adapted to such saturated and/or inundated conditions. Hydrology largely determines how the soil develops and the types of plant and animal communities living in and on the soil. Wetlands may support species ranging from obligate aquatic to obligate terrestrial. When the upper part of the soil is saturated with water at growing season temperatures, soil organisms consume the oxygen in the soil and cause conditions ([anaerobic]) unsuitable for most plants. Such conditions also cause the development of soil characteristics (such as color and texture) of so-called "hydric soils." The plants that can grow in such conditions, such as marsh grasses, are called "hydrophytes." Together, hydric soils and hydrophytes give clues that a wetland area is present.

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The presence of water by ponding, flooding, or soil saturation is not always a good indicator of wetlands. Except for wetlands flooded by ocean tides, the amount of water present in wetlands fluctuates as a result of rainfall patterns, snow melt, dry seasons and longer droughts. Some of the most well-known wetlands, such as the Everglades and Mississippi bottomland hardwood swamps, may have periods of dryness. In contrast, many upland areas are very wet during and shortly after wet weather. Such natural fluctuations must be considered when identifying areas subject to government regulation. Similarly, the effects of upstream dams, drainage ditches, dikes, irrigation, and other modifications must also be considered.

Types of wetlands Wetlands vary widely because of regional and local differences in soils, topography, climate, hydrology, water chemistry, vegetation, and other factors, including human disturbance. Indeed, wetlands are found from the tundra to the tropics and on every continent except Antarctica. Two general categories of wetlands are recognized: coastal or tidal wetlands and inland or non-tidal wetlands. Tidal (coastal) marshes occur along coastlines and are influenced by tides and often by freshwater from runoff, rivers, or groundwater. Salt marshes are the most prevalent types of tidal marshes and are characterized by salttolerant plants such as smooth cordgrass, saltgrass, and glasswort. Salt marshes have one of the highest rates of primary productivity associated with wetland ecosystems because of the inflow of nutrients and organics from surface and/or tidal water. Tidal freshwater marshes are located upstream of estuaries. Tides influence water levels but the water is fresh. The lack of salt stress allows a greater diversity of plants to thrive. Cattail, wild rice, pickerelweed, and arrowhead are common and help support a large and diverse range of bird and fish species, among other wildlife. Inland wetlands are most common on floodplains along rivers and streams (riparian wetlands), in isolated depressions surrounded by dry land (e.g., playas, basins, and "potholes"), along the margins of lakes and ponds, and in other low-lying areas where the groundwater intercepts the soil surface or where precipitation sufficiently saturates the soil (e.g., vernal pools and bogs). Inland wetlands include marshes and wet meadows dominated by herbaceous plants, swamps dominated by shrubs, and wooded swamps dominated by trees. Many of these wetlands are seasonal (they are dry one or more seasons every year), and, particularly in the arid and semiarid western United States, may be wet only periodically. The quantity of water present and the timing of its presence in part determine the functions of a wetland and its role in the environment. Even wetlands that appear dry at times for significant parts of the year—such as vernal pools—often provide critical habitat for wildlife adapted to breeding exclusively in these areas.

Wetland Categories

Wetland habitat along this Idaho riparian corridor provides food and shelter for diverse wildlife species.

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Inland wetlands found in the United States fall into four general categories—marshes, swamps, bogs, and fens. Marshes are wetlands dominated by soft-stemmed vegetation, while swamps have mostly woody plants. Bogs are freshwater wetlands, often formed in old glacial lakes, characterized by spongy peat deposits, evergreen trees and shrubs, and a floor covered by a thick carpet of sphagnum moss. Fens are freshwater peat-forming wetlands covered mostly by grasses, sedges, reeds, and wildflowers. More elaborate and detailed classifications may be found in publications from the U.S. Department of Interior's Fish and Wildlife Service.

Ecological roles of wetlands Wetlands are among the most productive ecosystems in the world, comparable to rainforests and coral reefs. An immense variety of species of microbes, plants, insects, amphibians, reptiles, birds, fish, and mammals can be part of a wetland ecosystem. Physical and chemical features such as climate, landscape shape (topology), geology, and the movement and abundance of water help to determine the plants and animals that inhabit each wetland. The complex, dynamic relationships among the organisms inhabiting the wetland environment are referred to as food webs.

Wetlands support a rich food web, from microscopic algae and dragonfly larvae to alligators, and black bears. Wetlands can be thought of as "biological supermarkets." They provide great volumes of food that attract many animal species. These animals use wetlands for part of or all of their life-cycle. Dead plant leaves and stems break down in the water to form small particles of organic material called "detritus." This enriched material feeds many small aquatic insects, shellfish, and small fish that are food for larger predatory fish, reptiles, amphibians, birds, and mammals. The functions of a wetland and the values of these functions to human society depend on a complex set of relationships between the wetland and the other ecosystems in the watershed. A watershed is a geographic area in which water, sediments, and dissolved materials drain from higher elevations to a common low-lying outlet or basin a point on a larger stream, lake, underlying aquifer, or estuary. Wetlands play an integral role in the ecology of the watershed. The combination of shallow water, high levels of nutrients, and primary productivity is ideal for the development of organisms that form the base of the food web and feed many species of fish, amphibians, shellfish, and insects. Many species of birds and mammals rely on wetlands for food, water, and shelter, especially during migration and breeding. Wetlands' microbes, plants, and wildlife are part of global cycles for water, nitrogen, and sulfur. Furthermore, scientists are beginning to realize that atmospheric maintenance may be an additional wetlands function. Wetlands store carbon within their plant communities and soil instead of releasing it to the atmosphere as carbon dioxide. Thus wetlands help to moderate global climate conditions.

Economic benefits of wetlands

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Only recently have we begun to understand the importance of the functions that wetlands perform. Far from being useless, disease-ridden places, wetlands provide values that no other ecosystem can, including natural water quality improvement, flood protection, shoreline erosion control, opportunities for recreation and aesthetic appreciation, and natural products for our use at no cost. Wetlands can provide one or more of these functions. Protecting wetlands in turn can protect our safety and welfare.

Water Quality and Hydrology Wetlands have important filtering capabilities for intercepting surface water runoff from higher dry land before the runoff reaches open water. As the runoff water passes through, the wetlands retain excess nutrients and some pollutants, and reduce sediment that would clog waterways and affect fish and amphibian egg development. In performing this filtering function, wetlands save us a great deal of money. For example, a 1990 study showed that without the Congaree Bottomland Hardwood Swamp in South Carolina, the area would need a US$5 million waste water treatment plant. In addition to improving water quality through filtering, some wetlands maintain stream flow during dry periods, and many replenish groundwater. Many Americans depend on groundwater for drinking.

Flood Protection Wetlands function as natural sponges that trap and slowly release surface water, rain, snowmelt, groundwater and flood waters. Trees, root mats, and other wetland vegetation also slow the speed of flood waters and distribute them more slowly over the floodplain. This combined water storage and braking action lowers flood heights and reduces erosion. Wetlands within and downstream of urban areas are particularly valuable, counteracting the greatly increased rate and volume of surface water runoff from pavement and buildings. The holding capacity of wetlands helps control floods and prevents water-logging of crops. Preserving and restoring wetlands, together with other water retention, can often provide the level of flood control otherwise provided by expensive dredge operations and levees. The bottomland hardwood-riparian wetlands along the Mississippi River once stored at least 60 days of floodwater. Now they store only 12 days because most have been filled or drained.

Shoreline Erosion The ability of wetlands to control erosion is so valuable that some states are restoring wetlands in coastal areas to buffer the storm surges from hurricanes and tropical storms. Wetlands at the margins of lakes, rivers, bays, and the ocean protect shorelines and stream banks against erosion. Wetland plants hold the soil in place with their roots, absorb the energy of waves, and break up the flow of stream or river currents.

Fish and Wildlife Habitat

The Redwinged blackbird (Agelaius phoeniceus), Blue-winged teal (Anas discors), and the Mallard (Anas platyrhynchos) can all be found in playa lakes at some time of the year. More than one-third of the United States' threatened and endangered species live only in wetlands, and nearly half use wetlands at some point in their lives. Many other animals and plants depend on wetlands for survival. Estuarine and marine fish and shellfish, various birds, and certain mammals must have coastal wetlands to survive. Most commercial and game fish breed and raise their young in coastal marshes and estuaries.

OMTEX CLASSES PROJECT ON WETLAND

Menhaden, flounder, sea trout, spot, croaker, and striped bass are among the more familiar fish that depend on coastal wetlands. Shrimp, oysters, clams, and blue and Dungeness crabs likewise need these wetlands for food, shelter, and breeding grounds. For many animals and plants, such as wood ducks, muskrat, cattails, and swamp rose, inland wetlands are the only places they can live. Beaver may actually create their own wetlands. For others, such as striped bass, peregrine falcon, otter, black bear, raccoon, and deer, wetlands provide important food, water, or shelter. Many of the U.S. breeding bird populations—including ducks, geese, woodpeckers, hawks, wading birds, and many song-birds—feed, nest, and raise their young in wetlands. Migratory waterfowl use coastal and inland wetlands as resting, feeding, breeding, or nesting grounds for at least part of the year. Indeed, an international agreement to protect wetlands of international importance was developed because some species of migratory birds are completely dependent on certain wetlands and would become extinct if those wetlands were destroyed.

Natural Products for Our Economy We use a wealth of natural products from wetlands, including fish and shellfish, blueberries, cranberries, timber, and wild rice, as well as medicines that are derived from wetland soils and plants. Many of the nation's fishing and shellfishing industries harvest wetland-dependent species; the catch is valued at US$15 billion a year. In the Southeast, for example, nearly all the commercial catch and over half of the recreational harvest are fish and shellfish that depend on the estuary-coastal wetland system. Louisiana's coastal marshes produce an annual commercial fish and shellfish harvest that amounted to 1.2 billion pounds worth US$244 million in 1991. Wetlands are habitats for fur-bearers like muskrat, beaver, and mink as well as reptiles such as alligators. The nation's harvest of muskrat pelts alone is worth over US$70 million annually.

Recreation and Aesthetics Wetlands have recreational, historical, scientific, and cultural values. More than half of all U.S. adults (98 million) hunt, fish, birdwatch or photograph wildlife. They spend a total of US$59.5 billion annually. Painters and writers continue to capture the beauty of wetlands on canvas and paper, or through cameras, and video and sound recorders. Others appreciate these wonderlands through hiking, boating, and other recreational activities. Almost everyone likes being on or near the water; part of the enjoyment is the varied, fascinating lifeforms.

Human impacts on wetlands

Seasonal wetland in summer. Human activities cause wetland degradation and loss by changing water quality, quantity, and flow rates; increasing pollutant inputs; and changing species composition as a result of disturbance and the introduction of nonnative species.

Hydrologic Alterations

OMTEX CLASSES PROJECT ON WETLAND

A wetland’s characteristics evolve when hydrologic conditions cause the water table to saturate or inundate the soil for a certain amount of time each year. Any change in hydrology can significantly alter the soil chemistry and plant and animal communities. Common hydrologic alterations in wetland areas include: •

Deposition of fill material for development;

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Drainage for development, farming, and mosquito control;

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Dredging and stream channelization for navigation, development, and flood control;

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Diking and damming to form ponds and lakes;

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Diversion of flow to or from wetlands; and

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Addition of impervious surfaces in the watershed, thereby increasing water and pollutant runoff into wetlands.

Pollution Inputs Although wetlands are capable of absorbing pollutants from the surface water, there is a limit to their capacity to do so. The primary pollutants causing wetland degradation are sediment, fertilizer, human sewage, animal waste, road salts, pesticides, heavy metals, and selenium. Pollutants can originate from many sources, including: •

Runoff from urban, agricultural, silvicultural, and mining areas;

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Air pollution from cars, factories, and power plants;

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Old landfills and dumps that leak toxic substances; and

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Marinas, where boats increase turbidity and release pollutants.

Vegetation Damage Wetland plants are susceptible to degradation if subjected to hydrological changes and pollution inputs. Other activities that can impair wetland vegetation include: •

Grazing by domestic animals;

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Introduction of nonnative plants that compete with natives; and

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Removal of vegetation for peat mining. Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Environmental Protection Agency. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Environmental Protection Agency should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

Florida's Everglades, the largest wetland system in the United States.[1] This article contains general information pertaining to all wetlands. For more details, see the specific wetland types, such as bog, marsh, and swamp. For Charlotte Roche's novel see Feuchtgebiete.

OMTEX CLASSES PROJECT ON WETLAND

A wetland is an area of land whose soil is saturated with moisture either permanently or seasonally. Such areas may also be covered partially or completely by shallow pools of water.[2] Wetlands include swamps, marshes, and bogs, among others. The water found in wetlands can be saltwater, freshwater, or brackish. The world's largest wetland is the Pantanal which straddles Brazil, Bolivia and Paraguay in South America. Wetlands are considered the most biologically diverse of all ecosystems. Plant life found in wetlands includes mangrove, water lilies, cattails, sedges, tamarack, black spruce, cypress, gum, and many others. Animal life includes many different amphibians, reptiles, birds, and furbearers.[3] In many locations, such as the United Kingdom, Iraq, South Africa and the United States, wetlands are the subject of conservation efforts and Biodiversity Action Plans. The study of wetlands has recently been termed paludology in some publications.[4] •

[edit] Technical definitions Wetlands have been categorized both as biomes and ecosystems.[3] They are generally distinguished from other water bodies or landforms based on their water level and on the types of plants that thrive within them. Specifically, wetlands are characterized as having a water table that stands at or near the land surface for a long enough season each year to support aquatic plants.[3][5][6] Put simply, wetlands are lands made up of hydric soil. Wetlands have also been described as ecotones, providing a transition between dry land and water bodies.[7] Mitsch and Gosselink write that wetlands exist "...at the interface between truly terrestrial ecosystems and aquatic systems, making them inherently different from each other, yet highly dependent on both."[8]

[edit] Ramsar Convention definition Under the Ramsar international wetland conservation treaty, wetlands are defined as follows: •

Article 1.1: "...wetlands are areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres."

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Article 2.1: "[Wetlands] may incorporate riparian and coastal zones adjacent to the wetlands, and islands or bodies of marine water deeper than six metres at low tide lying within the wetlands".

[edit] Regional definitions In the United States, wetlands are defined as "those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas"[9]. Some states, such as Massachusetts and New York, have separate definitions that may differ from United States federal laws.

[edit] Conservation Due to their lack of potential financial benefits, wetlands have historically been the victim of large-scale draining efforts for real estate development, or flooding for use as recreational lakes. Wetlands provide a valuable flood control function, but building levees helps replace natural flood controls. Wetlands were very effective at filtering and cleaning water[10], so to help with the ever increasing challenge of decreasing water pollution (often from agricultural runoff from the farms that replaced the wetlands in the first place), millions of dollars have been invested on water purification plants and expensive remediation measures. The USA came to understand how biologically productive wetlands are, so the USA passed laws limiting wetlands destruction, and created requirements that if a wetland had to be drained, developers at least had to offset the loss by creating artificial wetlands. One example is the project by the U.S. Army Corps of Engineers to control flooding and enhance development by taming the Everglades, a project which has now been reversed to restore much of the wetlands as a natural habitat for plant and animal life, as well as a method of flood control.

OMTEX CLASSES PROJECT ON WETLAND

By 1993 half the world's wetlands had been drained.[11] Since the 1970s, more focus has been put on preserving wetlands for their natural function — sometimes also at great expense. The South African Department of Environmental Affairs and Tourism in conjunction with the departments of Water Affairs and Forestry, and of Agriculture, supports the conservation and rehabilitation of wetlands through the Working for Wetlands program.[12] The aim of this program is to encourage the protection, rehabilitation and sustainable use of South African wetlands through co-operative governance and partnerships. The program is also a poverty relief effort, providing employment in wetland maintenance. Over 90% of the wetlands in New Zealand have been drained since European settlement, predominantly to create farmland. Wetlands now have a degree of protection under the Resource Management Act.

[edit] Ramsar Convention Main article: Ramsar Convention The Convention on Wetlands of International Importance, especially as Waterfowl Habitat, or Ramsar Convention, is an international treaty designed to address global concerns regarding wetland loss and degradation. The primary purposes of the treaty are to list wetlands of international importance and to promote their wise use, with the ultimate goal of preserving the world's wetlands. Methods include restricting access to the majority portion of wetland areas, as well as educating the public to combat the misconception that wetlands are wastelands.

[edit] Climate Temperature Temperatures vary greatly depending on the location of the wetland. Many of the world's wetlands are in temperate zones (midway between the North and South Poles and the equator). In these zones, summers are warm and winters are cold, but temperatures are not extreme. However, wetlands found in the tropic zone, which is around the equator, are always warm. Temperatures in wetlands on the Arabian Peninsula, for example, can reach 50 °C (122 °F). In northeastern Siberia, which has a polar climate, wetland temperatures can be as cold as −50 °C (−58 °F). Rainfall The amount of rainfall a wetland receives depends upon its location. Wetlands in Wales, Scotland, and Western Ireland receive about 150 cm (59 in) per year. Those in Southeast Asia, where heavy rains occur, can receive up to 500 cm (200 in). In the northern areas of North America, wetlands exist where as little as 15 cm (6 in) of rain fall each year.

[edit] List of wetland types

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Constructed wetland From Wikipedia, the free encyclopedia

Jump to: navigation, search This article is missing citations or needs footnotes. Please help add inline citations to guard against copyright violations and factual inaccuracies. (April 2008)

Vertical Flow Constructed Wetlands A constructed wetland or wetpark is an artificial marsh or swamp, created for anthropogenic discharge such as wastewater, stormwater runoff or sewage treatment, and as habitat for wildlife, or for land reclamation after mining or other disturbance. Natural wetlands act as biofilter, removing sediments and pollutants such as heavy metals from the water, and constructed wetlands can be designed to emulate these features.

Contents [hide] •

1 Wetlands

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2 General contaminant removal

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3 Removal of nitrogen

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3.1 Organic nitrogen

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3.2 Ammonia (NH3) and ammonium (NH4+)

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3.3 Nitrogen removal in constructed wetlands used to treat domestic sewage

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3.4 Nitrogen removal in constructed wetlands used to treat mine water

4 Removal of phosphorus ○

4.1 Incorporation into biomass

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4.2 Phosphorus retention by soils or root-bed media

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4.3 Phosphorus removal in constructed wetlands used to treat domestic sewage

5 Removal of metals

OMTEX CLASSES PROJECT ON WETLAND •

6 Set-up of commercial treatment ponds/combined treatment ponds construction in urban areas ○

6.1 Design characteristics of the commercial systems

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6.2 Plants/organisms used in treatment ponds in commercial undertakings

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7 Finishing

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8 Literature citations

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9 See also

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10 References

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11 External links

[edit] Wetlands Vegetation in a wetland provides a substrate (roots, stems, and leaves) upon which microorganisms can grow as they break down organic materials. This community of microorganisms is known as the periphyton. The periphyton and natural chemical processes are responsible for approximately 90 percent of pollutant removal and waste breakdown. The plants remove about seven to ten percent of pollutants, and act as a carbon source for the microbes when they decay. Different species of aquatic plants have different rates of heavy metal uptake, a consideration for plant selection in a constructed wetland used for water treatment. Constructed wetlands are of two basic types: subsurface-flow and surface-flow wetlands. Subsurface-flow wetlands can be further classified as horizontal flow and vertical flow constructed wetlands. Subsurface-flow wetlands move effluent (agricultural or mining runoff, tannery or meat processing wastes, wastewater from sewage or storm drains, or other water to be cleansed) through a gravel lavastone or sand medium on which plants are rooted; surface-flow wetlands move effluent above the soil in a planted marsh or swamp, and thus can be supported by a wider variety of soil types including bay mud and other silty clays. In subsurface-flow systems, the effluent may move either horizontally, parallel to the surface, or vertically, from the planted layer down through the substrate and out. Subsurface horizontal-flow wetlands are less hospitable to mosquitoes, whose populations can be a problem in constructed wetlands (carnivorous plants have been used to address this problem). Subsurface-flow systems have the advantage of requiring less land area for water treatment, but are not generally as suitable for wildlife habitat as are surface-flow constructed wetlands. Plantings of reedbeds are popular in European constructed wetlands, and plants such as cattails (Typha spp.), sedges, Water Hyacinth (Eichhornia crassipes) and Pontederia spp. are used worldwide. Recent research in use of constructed wetlands for subarctic regions has shown that buckbeans (Menyanthes trifoliata) and pendant grass (Arctophila fulva) are also useful for metals uptake.

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Newly Planted Constructed Wetland.

The same constructed wetland two years later.

[edit] General contaminant removal Physical, chemical, and biological processes combine in wetlands to remove contaminants from wastewater. An understanding of these processes is fundamental not only to designing wetland systems but to understanding the fate of chemicals once they have entered the wetland. Theoretically, treatment of wastewater within a constructed wetland occurs as it passes through the wetland medium and the plant rhizosphere. A thin aerobic film around each root hair is aerobic due to the leakage of oxygen from the rhizomes, roots, and rootlets.[1] Decomposition of organic matter is facilitated by aerobic and anaerobic micro-organisms present. Microbial nitrification and subsequent denitrification releases nitrogen as gas to the atmosphere. Phosphorus is coprecipitated with iron, aluminium, and calcium compounds located in the root-bed medium.[2][3] Suspended solids are filtered out as they settle in the water column in surface flow wetlands or are physically filtered out by the medium within subsurface flow wetland cells. Harmful bacteria and viruses are reduced by filtration and adsorption by biofilms on the rock media in subsurface flow and vertical flow systems.

[edit] Removal of nitrogen The dominant forms of nitrogen in wetlands that are of importance to wastewater treatment include organic nitrogen, ammonia, ammonium, nitrate, nitrite, and nitrogen gases. Inorganic forms are essential to plant growth in aquatic systems but if scarce can limit or control plant productivity.[4] The nitrogen entering wetland systems can be measured as organic nitrogen, ammonia, nitrate and nitrite. Total Nitrogen refers to all nitrogen species. The removal of nitrogen from wastewater is important because of ammonia’s toxicity to fish if discharged into water courses. Excessive levels of nitrates in drinking water is thought to cause methemoglobinemia in infants, which decreases the oxygen transport ability of the blood. The UK has experienced a significant increase in nitrate concentration in groundwater and rivers.[5]

[edit] Organic nitrogen Mitsch & Gosselink define nitrogen mineralisation as "the biological transformation of organically combined nitrogen to ammonium nitrogen during organic matter degradation".[6] This can be both an aerobic and anaerobic process and is often referred to as ammonification. Mineralisation of organically combined nitrogen releases inorganic nitrogen as nitrates, nitrites, ammonia and ammonium, making it available for plants, fungi and bacteria.[6] Mineralisation rates may be affected by oxygen levels in a wetland.[3]

[edit] Ammonia (NH3) and ammonium (NH4+) The formation of ammonia (NH3) occurs via the mineralisation or ammonification of organic matter under either anaerobic or aerobic conditions (Keeney, 1973). The ammonium ion (NH4+) is the primary form of mineralized nitrogen in most flooded wetland soils. The formation of this ion occurs when ammonia combines with water as follows: NH3 + H2O ⇌ NH4+ + OH[6]

Upon formation, several pathways are available to the ammonium ion. It can be absorbed by the plants and algae and converted back into organic matter, or the ammonium ion can be electrostatically held on negatively charged surfaces of soil particles.[6] At this point, the ammonium ion can be prevented from further oxidation because of the anaerobic nature of wetland soils. Under these conditions the ammonium ion is stable and it is in this form that nitrogen predominates in anaerobic sediments typical of wetlands (Brock & Madigan, 1991; ).[3] Most wetland soils have a thin aerobic layer at the surface. As an ammonium ion from the anaerobic sediments diffuses upward into this layer it is converted to nitrite or nitrified (Klopatek, 1978). An increase in the thickness of this aerobic layer results in an increase in nitrification.[3] This diffusion of the ammonium ion sets

OMTEX CLASSES PROJECT ON WETLAND

up a concentration gradient across the aerobic-anaerobic soil layers resulting in further nitrification reactions (Klopatek, 1978).[3] Nitrification is the biological conversion of organic and inorganic nitrogenous compounds from a reduced state to a more oxidized state.[7] Nitrification is strictly an aerobic process in which the end product is nitrate (NO3-); this process is limited when anaerobic conditions prevail.[3] Nitrification will occur readily down to 0.3 ppm dissolved oxygen (Keeney, 1973). The process of nitrification (1) oxidizes ammonium (from the sediment) to nitrite (NO2-), and then (2) nitrite is oxidized to nitrate (NO3-). The overall nitrification reactions are as follows: (1) 2 NH4+ + 3 O2 ⇌ 4 H+ + 2 H2O + 2 NO2(2) 2 NO2- + O2 ⇌ 2 NO3(Davies & Hart, 1990) Two different bacteria are required to complete this oxidation of ammonium to nitrate. Nitrosomonas sp. oxidizes ammonium to nitrite via reaction (1), and Nitrobacter sp. oxidizes nitrite to nitrate via reaction (2) (Keeney, 1973). Denitrification is the biochemical reduction of oxidized nitrogen anions, nitrate (NO3-) and nitrite (NO2-) to produce the gaseous products nitric oxide (NO), nitrous oxide (N2O) and nitrogen gas (N2), with concomitant oxidation of organic matter.[7] The general sequence is as follows: NO3- → NO2- → NO → N2O → N2 The end products, N2O and N2 are gases that re-enter the atmosphere. Denitrification occurs intensely in anaerobic environments but will also occur in aerobic conditions (Bandurski, 1965). A deficiency of oxygen causes certain bacteria to use nitrate in place of oxygen as an electron acceptor for the reduction of organic matter.[3] The process of denitrification is restricted to a narrow zone in the sediment immediately below the aerobic-anaerobic soil interface (Nielson et al., 1990).[6] Denitrification is considered by Richardson et al. (1978) to be the predominant microbial process that modifies the chemical composition of nitrogen in a wetland system and the major process whereby elemental nitrogen is returned to the atmosphere.[3] To summarize, the nitrogen cycle is completed as follows: ammonia in water, at or near neutral pH is converted to ammonium ions; the aerobic bacterium Nitrosomonas sp. oxidizes ammonium to nitrite; Nitrobacter sp. then converts nitrite to nitrate. Under anaerobic conditions, nitrate is reduced to relatively harmless nitrogen gas, that is given off to the atmosphere.

[edit] Nitrogen removal in constructed wetlands used to treat domestic sewage In a review of 19 surface flow wetlands (US EPA, 1988) it was found that nearly all reduced total nitrogen. In a review of both surface flow and subsurface flow wetlands Reed (1995) concluded that effluent nitrate concentration is dependent on maintaining anoxic conditions within the wetland so that denitrification can occur. He found that subsurface flow wetlands were superior to surface flow wetlands for nitrate removal. The 20 surface flow wetlands reviewed reported effluent nitrate levels below 5 mg/L; the 12 subsurface flow wetlands reviewed reported effluent nitrate ranging from <1 to < 10 mg/L. Results obtained from the NiagaraOn-The-Lake vertical flow systems show a significant reduction in both total nitrogen and ammonia (> 97%) when primary treated effluent was applied at a rate of 60L/m²/day. Calculations made showed that over 50% of the total nitrogen going into the system was converted to relatively harmless nitrogen gas. Effective removal of nitrate from the sewage lagoon influent was dependent on medium type used within the vertical cell as well as water table level within the cell (Lemon et al.,1997).

[edit] Nitrogen removal in constructed wetlands used to treat mine water Constructed wetlands have also been used to remove ammonia from mine drainage. In Ontario, Canada, drainage from the polishing pond at the Campbell Mine flows by gravity through a 9.3 hectare constructed wetland during the ice-free season (See brief description in[2]). Ammonia is removed by approximately 95% on inflows of up to 15,000 m3/day during the summer months, while removal rates decrease to 50-70% removal during cold months. Other contaminants, including copper, are also removed in the wetland, such that the final discharge is full detoxified. Thanks to this constructed wetland, Campbell was one of the first gold mines in Ontario to produce a completely non-toxic discharge, as determined by acute and chronic toxicity tests. At the

OMTEX CLASSES PROJECT ON WETLAND

Ranger Uranium Mine, in Australia, ammonia is removed in "enhanced" natural wetlands (rather than fully engineered constructed wetlands), along with manganese, uranium and other metals. Other mines have used natural or constructed wetlands to remove nitrogenous compounds from contaminated mine water, including cyanide (at the Jolu and Star Lake Mines, where natural muskeg and wetlands were used) and nitrate (demonstrate at the Quinsam Coal Mine). Wetlands were also proposed to remove nitrogenous compounds (present as blasting residues) from diamond mines in Northern Canada. However, land application is equally effective and is a technology easier to implement than a constructed wetland.

[edit] Removal of phosphorus Phosphorus occurs naturally in both organic and inorganic forms. The analytical measure of biologically available orthophosphates is referred to as soluble reactive phosphorus (SR-P). Dissolved organic phosphorus and insoluble forms of organic and inorganic phosphorus are generally not biologically available until transformed into soluble inorganic forms.[6] In freshwater aquatic ecosystems phosphorus has been described as the major limiting nutrient. Under undisturbed natural conditions, phosphorus is in short supply. The natural scarcity of phosphorus is demonstrated by the explosive growth of algae in water receiving heavy discharges of phosphorus-rich wastes. Because phosphorus does not have an atmospheric component as does nitrogen, the phosphorus cycle can be characterized as closed. The removal and storage of phosphorus from wastewater can only occur within the constructed wetland itself. According to Mitsch and Gosselink phosphorus may be sequestered within a wetland system by the following: 1. The binding of phosphorus in organic matter as a result of incorporation into living biomass, 2. Precipitation of insoluble phosphates with ferric iron, calcium, and aluminium found in wetland soils.[6]

[edit] Incorporation into biomass Higher plants in wetland systems may be viewed as transient nutrient storage compartments absorbing nutrients during the growing season and releasing large amounts at senescence (Guntensbergen, 1989).[8] Generally, plants from nutrient-rich habitats accumulate more nutrients than plants found in nutrient-poor habitats, a phenomenon referred to as luxury uptake of nutrients (Guntensbergen, 1989; Kadlec, 1989). Aquatic vegetation may play an important role in phosphorus removal and, if harvested, extend the life of a system by postponing phosphorus saturation of the sediments (Breen, 1990; Guntensbergen, 1989; Rogers et al., 1991). According to Sloey et al. (1978) vascular plants may account for only a small amount of phosphorus uptake with only 5 to 20% of the nutrients detained in a natural wetland being stored in harvestable plant material. Bernard and Solsky also reported relatively low phosphorus retention, estimating that a sedge (Carex sp.) wetland retained 1.9 g of phosphorus per square metre of wetland.[8] Bulrushes (Scirpus sp.) in a constructed wetland system receiving secondarily treated domestic wastes contained 40.5% of the total phosphorus influent. The remaining 59.0% was found to be stored in the gravel substratum (Sloey et al., 1978). Phosphorus removal in a surface flow wetland treatment system planted with one of Scirpus sp., Phragmites sp. or Typha sp. was investigated by Finlayson and Chick (1983). Phosphorus removal of 60%, 28%, and 46% were found for Scirpus sp., Phragmites sp. and Typha sp. respectively. More recent work by Breen (1990) may prove this to be a low estimate. His work on an artificial wetland indicated that vascular plants are a major phosphorus storage compartment accounting for 67.3% of the influent phosphorus. Thut (1989) attributed plant adsorption with 80% phosphorus removal. Only a small proportion (<20%) of phosphate removal by constructed wetlands can be attributed to nutritional uptake by bacteria, fungi and algae (Moss, 1988). Swindell et al., (1990) found that the lack of seasonal fluctuation in phosphorus removal rates suggests that the primary mechanism is bacterial and alga fixation. However, Richardson (1985) dismisses this mechanism as temporary saying that although the initial removal of dissolved inorganic phosphorus from the water under natural loading levels is due largely to microbial uptake and adsorption, the microbial pool is small and quickly becomes saturated at which point the soil medium takes over as the major contributor to phosphate removal.

OMTEX CLASSES PROJECT ON WETLAND

There are more indirect ways in which plants contribute to wastewater purification. Plants create a unique environment at the attachment surface of the biofilm. Certain plants transport oxygen which is released at the biofilm/root interface perhaps adding oxygen to the wetland system (Pride et al., 1990). Plants also increase soil or other root-bed medium hydraulic conductivity. As roots and rhizomes grow they are thought to disturb and loosen the medium increasing its porosity which may allow more effective fluid movement in the rhizosphere. When roots decay they leave behind ports and channels known as macropores which are effective in channeling water through the soil (Conley et al., 1991). Whether or not wetland systems act as a phosphorus sink or source seems to depend on system characteristics such as sediment and hydrology. Kramer et al., (1972) indicated that there seems to be a net movement of phosphorus into the sediment in many lakes. In Lake Erie as much as 80% of the total phosphorus is removed from the waters by natural processes and is presumably stored in the sediment. According to Klopatek (1978) marsh sediments high in organic matter act as sinks. He has also shown that phosphorus release from a marsh exhibits a cyclical pattern. Much of the spring phosphorus release comes from high phosphorus concentrations locked up in the winter ice covering the marsh; in summer the marsh acts as a phosphorus sponge. Simpson (1978) found that phosphorus was exported from the system following dieback of vascular plants. It has been demonstrated by Klopatek (1978) that phosphorus concentrations in water are reduced during the growing season due to plant uptake but decomposition and subsequent mineralisation of organic matter releases phosphorus over the winter and accounts for the higher winter phosphorus concentrations in the marsh (Klopatek, 1978;).[6]

[edit] Phosphorus retention by soils or root-bed media Two types of phosphate retention mechanisms may occur in soils or root-bed media: chemical adsorption onto the medium (Hsu, 1964) and physical precipitation of the phosphate ion (Faulkner and Richardson, 1989). Both result from the attraction between phosphate ion and ions of Al, Fe or Ca (Hsu, 1964; Cole et al., 1953) and terminates with formation of various iron phosphates (Fe-P), aluminum phosphates (Al-P) or calcium phosphates (Ca-P) (Fried and Dean, 1955). Oxidation-reduction potential (ORP, formally reported as Eh) of soil or water is a measure of its ability to reduce or oxidize chemical substances and may range between -350 and +600 millivolts (mV). Though the oxidation state of phosphorus is unaffected by redox potential, redox potential is indirectly important because of its effect on iron solubility (through reduction of ferric oxides). Severely reduced conditions in the sediments may result in phosphorus release (Mann, 1990). Typical wetland soils may have an Eh of -200 mV (Hammer, 1992). Under these reduced conditions Fe3+ (Ferric iron) in insoluble ferric oxides may be reduced to soluble Fe2+ (Ferrous iron). Any phosphate ion bound to the ferric oxide may be release back into solution as it dissolves (Faulkner and Richardson, 1989; Sah and Mikkelson, 1986). However, the Fe2+ diffusing in the water column may be re-oxidized to Fe3+ and re-precipitated as an iron oxide when it encounters oxygenated surface water. This precipitation reaction may remove phosphate from the water column and deposit it back on the surface of sediments [7]. Thus, there can be a dynamic uptake and release of phosphorus in sediments that is governed by the amount of oxygen in the water column. A well documented occurrence in the hypolimnion of lakes is the release of soluble phosphorus when conditions become anaerobic (Burns & Ross, 1972; Williams & Mayer, 1972). This phenomenon also occurs in natural wetlands (Gosselink & Turner, 1978) and Kramer et al., (1972) report that oxygen concentrations of less than 2.0 mg/l result in the release of phosphorus from sediments.

[edit] Phosphorus removal in constructed wetlands used to treat domestic sewage Adsorption to binding sites within the sediments was identified as the major phosphorus removal mechanism in the surface flow constructed wetland system at Port Perry, Ontario (Snell, unpublished data). Release of phosphorus from the sediments occurred when anaerobic conditions prevailed. The lowest wetland effluent phosphorus levels occurred when oxygen levels of the overlying water column were above 1.0 mg / L. Removal efficiencies for total phosphorus were 54-59% with mean effluent levels of 0.38 mg P/L. Wetland effluent phosphorus concentration was higher than influent levels during the winter months.

OMTEX CLASSES PROJECT ON WETLAND

Lantzke et al., (1999) investigated phosphorus removal in a VF wetland in Australia and found that the quantity of phosphorus removed over a short term was stored in the following wetland components in order of decreasing importance: substratum> macrophyte >biofilm but over the long term phosphorus storage was located in macrophyte> substratum>biofilm components. They also found that medium iron-oxide adsorption provides additional removal for some years. Mann (1990) investigated the phosphorus removal efficiency of two large-scale, surface flow wetland systems in Australia which had a gravel substratum. He then compared these results to laboratory phosphorus adsorption experiments. For the first two months of wetland operation the mean phosphorus removal efficiency of system 1 and 2 was 38% and 22%, respectively. Over the first year a decline in removal efficiencies occurred. During the second year of operation release of phosphorus from the system was often recorded such that more phosphorus came out than was put in. This release was attributed to the saturation of phosphorus binding sites. Close agreement was found between the phosphorus adsorption capacity of the gravel as determined in the laboratory and the adsorption capacity recorded in the field. The phosphorus adsorption capacity of a subsurface flow constructed wetland system containing a predominantly quartz gravel was investigated by Breen (1990). The adsorption characteristics of this gravel as determined by laboratory adsorption experiments and using the Langmuir adsorption isotherm was 25 mg P / g gravel. Close agreement between calculated and realized phosphorus adsorption was found. Because of the poor adsorption capacity of the quartz gravel, plant uptake and subsequent harvesting were identified as the major phosphorus removal mechanism.[9]

[edit] Removal of metals Constructed wetlands have been used extensively for the removal of dissolved metals and metalloids. Although these contaminants are prevalent in mine drainage, they are also found in stormwater, landfill leachate and other sources (e.g., leachate or FDG washwater at coal-fired power plants), for which treatment wetlands have been constructed. An older web site [3] describes the application of constructed wetlands for treatment of contaminated mine drainage. Other sites (mostly in North America, although some are found in Europe e.g., [4]) describe various other applications of this technology.

[edit] Set-up of commercial treatment ponds/combined treatment ponds construction in urban areas

The 3 treatment set-ups mostly employed As previously mentioned, 3 types of reedbed-set ups are used. All these systems are used in commercial systems (usually together with septic tanks).[10] The system again are: •

Surface flow (SF) reedbeds

•

Sub Surface Flow (SSF) reedbeds

•

Vertical Flow (VF) reedbeds

OMTEX CLASSES PROJECT ON WETLAND

All three types of reed beds are placed in a closed basin with a substrate. Also, for most commercial undertakings (eg agricultural enterprises), the bottom is covered with a rubber foil (to ensure that the whole is completely waterproof, which is essential in urban areas). The substrate can be either gravel, sand or lavastone.

[edit] Design characteristics of the commercial systems

A water-purifying pond, planted with Iris pseudacorus Surface flow reed beds are characterised by the horizontal flow of wastewater between the roots of the plants. They are no longer used as much due to the land-area requirements to purify water for a single person (20 m²), and the increased smell and poor purification in winter.[10] With subsurface flow reedbeds, the flow of wastewater occurs between the roots of the plants itself (and not at the water surface). As a result the system is more efficient, less odorous and less sensitive to winter conditions. Also, less area is needed to purify water for a single person (5-10 m²). A downside to the system are the intakes, which can clog easily.[10] Vertical flow reed beds are very similar to subsurface flow reed beds (subsurface wastewater flow is present here as well), according comparable advantages in efficiency and winter hardiness. The wastewater is divided at the bottom with the assistance of a pump. Other than the 2 previous systems, this system makes almost exclusive use of fine sand to increase bacteria counts. Intake of oxygen into the water is also better, and pumping is pulsed to reduce obstructions within the intakes. Through the increased efficiency, only 3 m² of space is needed to purify the water for one person.[10]

[edit] Plants/organisms used in treatment ponds in commercial undertakings See also: Organisms used in water purification Usually, Common Reed (Phragmites australis) are used in treatment ponds (eg in greywater treatment systems to purify wastewater). In self-purifying water reservoirs (used to purify rainwater) however, certain other plants are used as well. These reservoirs firstly need to be dimensioned to be filled with 1/4th of lavastone and waterpurifying plants to purify a certain water quantity.[11] The water-purifying plants used include a wide variety of plants, depending on the local climate and geographical location. Plants are usually chosen which are indigenous in that location for ecological reasons and optimum workings of the system. In addition to water-purifying (de-nutrifying) plants, plants that supply oxygen, and shade are also added in to allow a complete ecosystem to form. Finally, in addition to plants, locally grown bacteria and non-predatory fish are also added to eliminate pests. The bacteria are usually grown locally by submerging straw in water and allowing it to form bacteria (arriving from the surrounding atmosphere). The plants used (placed on an area 1/4th of the water mass) are divided in 4 separate water depthzones; knowingly: 1. A water-depth zone from 0-20 cm; Yellow Iris (Iris pseudacorus), Simplestem Bur-reed (Sparganium

erectum), ... may be placed here (temperate climates) 2. A water-depth zone from 40-60 cm; Water Soldier (Stratiotes aloides), European Frogbit (Hydrocharis

morsus-ranae), ... may be placed here (temperate climates)

OMTEX CLASSES PROJECT ON WETLAND

3. A water-depth zone from 60-120 cm; European White Waterlily (Nymphaea alba), ... my be placed here

(temperate climates) 4. A submerged water-depth zone; Eurasian Water-milfoil (Myriophyllum spicatum), ... may be placed here

(temperate climates) Finally, 3 types of (non-predatory) fish (surface; bottom and ground-swimmers) are chosen. This is to ensure that the fish may coexist peacefully. Examples of the 3 types of fish (for temperate climates) are: •

Surface swimming fish: Common dace (Leuciscus leuciscus), Ide (Leuciscus idus), common rudd (Scardinius erythrophthalmus), ...

•

Middle-swimmers: Common roach (Rutilus rutilus), ...

•

Bottom-swimming fish: Tench (Tinca tinca), ...

The plants are usually grown on Coco Peat.[12] At the time of implantation to water-purifying ponds, de-nutrified soil is used to prevent the possible growth of algae and unwanted organisms.

Flowforms in treatment pond in Norway

[edit] Finishing Finally, also worth mentioning are the hybrid systems. These are systems that for example aerate the water after the final reedbed using cascades such as Flowforms before holding the water in a shallow pond.[13] Also, primary treatments as septic tanks, and different types of pumps as grinder pumps may also be added.[14]