Constructed wetlands are an alternative wastewater treatment method that mimics natural processes to cleanse water. Microorganisms that naturally live in water, on rocks, in soil, and on the stems and roots of wetland plants feed on organic materials and nutrients, removing pollutants from the wastewater.
What is a constructed wetland?
wHAT ARE CONSTRUCTED WETLANDS? Constructed Wetlands are natural water purification systems. A constructed wetland is essentially, a shallow basin filled with a substrate, usually sand and gravel, and planted with vegetation tolerant of saturated conditions.
What are constructed wetlands?
Types and design considerations
- Subsurface flow constructed wetland - this wetland can be either with vertical flow (the effluent moves vertically, from the planted layer down through the substrate and out) or with horizontal ...
- Surface flow constructed wetland (this wetland has horizontal flow)
- Floating treatment wetland
How to building a floating wetland?
Floating wetlands are container gardens that float on the surface of the water. You can plant floating pond islands with any wetland marsh plants except trees and shrubs. They make a beautiful addition to any pond. As the plant roots grow beneath the island, they absorb excess nutrients from fertilizer runoff, animal wastes and other sources.
What is MBBR wastewater treatment?
- Compact: MBBR is an excellent option for facilities with space constraints, since it typically has a much smaller footprint than other systems. ...
- Simple: Another practical advantage of MBBR is that it is a relatively straightforward process. ...
- Low maintenance: MBBR is also known for being a low-maintenance process. ...
How does wetland based sewage treatment work?
2:335:19Constructed Wetlands for Wastewater Treatment - YouTubeYouTubeStart of suggested clipEnd of suggested clipAnd nutrients. For example natural removal is mainly done via nitrification. And denitrificationMoreAnd nutrients. For example natural removal is mainly done via nitrification. And denitrification processes in which the ammonia is oxidized to nitrate by nitrifying bacteria under aerobic conditions
What is the purpose of a constructed wetland?
A constructed wetland is used to recreate the treatment processes that occur in natural wetlands. Natural wetlands generally have visible water in the system. (NOTE: Natural wetlands are not to be used to treat wastewater. Constructed wetlands are sized and designed specifically to treat wastewater.)
How effective are constructed wetlands?
If properly built, maintained and operated, constructed wetlands can effectively remove many pollutants associated with municipal and industrial wastewater and stormwater. Such systems are especially efficient at removing contaminants such as BOD, suspended solids, nitrogen, phosphorus, hydrocarbons, and even metals.
Do constructed wetlands improve water quality?
Constructed wetlands are used throughout the world to treat wastewater and runoff, improving water quality. They may also be used residentially, following primary septic tank treatment. Using constructed wetlands to treat greywater is a growing trend in water conservation.
What are the disadvantages of constructed wetlands?
Disadvantages of constructed wetlands include high land area requirements (depending on the design, they may require a relatively large land area compared to a conventional facility), the need for a preliminary treatment before the wastewaters treated by the system (normally they do not used to treat raw wastewaters), ...
What are the two types of constructed wetlands?
Subsurface wetland provide greater pathogen removal than surface wetlands. There are two main types of constructed wetlands: subsurface flow and surface flow constructed wetlands. The planted vegetation plays an important role in contaminant removal.
Do constructed wetlands smell?
Water flows through the wetland by passing from one pore space to the next while remaining below the surface of the media. If the total cross-sectional area of pore spaces is too small, wastewater cannot enter the media, and the water level rises to the surface of the wetland, causing odors.
How do you create a constructed wetland?
0:3626:11Constructed Wetland Design - YouTubeYouTubeStart of suggested clipEnd of suggested clipAnd often you'll have reed plants that are then emerging. Out there's also storm water wetlands. SoMoreAnd often you'll have reed plants that are then emerging. Out there's also storm water wetlands. So these are wetlands that are designed to hold water and then infiltrate it slowly.
Are constructed wetlands expensive?
Constructed wetlands are finding increasing uses communities because they cost less than conventional wastewater treatment plants. Also they readily can be accommodated in these areas, which have the land such systems require.
How does wetlands purify water?
Wetlands can improve water quality by removing pollutants from surface waters. Three pollutant removal processes provided by wetlands are particularly important: sediment trapping, nutrient removal and chemical detoxification.
What is a wetland septic system?
A constructed wetland mimics the treatment processes that occur in natural wetlands. Wastewater flows from the septic tank and enters the wetland cell. The wastewater then passes through the media and is treated by microbes, plants, and other media that remove pathogens and nutrients.
How do wetlands manage water?
Wetlands primarily help filter water in two ways: firstly, by slowing the flow of water, sediment in the water can settle to the bottom of the wetland; and secondly, vegetation in the wetland can absorb excess nutrients reducing the amount of contaminants from urban/agricultural areas that reach downstream aquatic ...
What is a constructed wetland system?
A constructed wetland system for domestic wastewater treatment is designed to mimic the natural wetland treatment processes by Mother Nature. This system uses plants and microbes to improve the wastewater quality.
How does wastewater exit a wetland?
After flowing through the media, wastewater exits the wetland through a water-level control sump.
How is wastewater treated?
Wastewater is treated by the septic tank first. The tank, which should have two compartments, should be sized appropriately to allow enough time for the settling solids to separate from the wastewater. Upon leaving the septic tank, wastewater enters the wetland.
How to determine the size of a wetland?
Wetland systems remove biological materials, suspended solids, nutrients and pathogens from the wastewater. To determine a wetland’s size, consider: 1 Temperature of the system, which affects how fast it removes nutrients; and 2 Amount of waste. A wastewater treatment system must be designed to treat the most wastewater that a residence generates.
How does water flow through a wetland?
Water flows through the wetland by passing from one pore space to the next while remaining below the surface of the media. If the total cross-sectional area of pore spaces is too small, wastewater cannot enter the media, and the water level rises to the surface of the wetland, causing odors.
How much surface area does a wetland need?
In general, a constructed wetland in Texas needs about 1 square foot of surface area for every gallon of wastewater it receives a day. A wetland for an average three-bedroom house producing 300 gallons of wastewater a day would need a surface area of 300 square feet.
What is a wetland?
A constructed wetland, which is a bed of graded stone, with water beneath the surface, where aquatic plants are grown. It removes nutrients, organic matter, suspended solids, and pathogens; and. A final treatment and dispersal system, which disperses the wastewater into the soil for final treatment and dispersal/reuse.
How do wetlands treat wastewater?
Constructed wetlands treat wastewaters by a number of routes; filtration, adsorption, precipitation, ion exchange, plant uptake, and microbial degradation (both aerobic and anaerobic). There are two types of constructed wetland.
What is a constructed wetlands?
Constructed wetlands or treatment wetlands are artificial wetlands that are used for treating organic, inorganic and excess nutrient contaminants in surface water, municipal wastewater, domestic sewage, refinery effluents, acid uranium mine drainage or landfill leachate. A considerable amount of research and applied work has been conducted using constructed wetlands for some of these applications. Kadlec and Knight (1996), Cole (1998) and Pivetz (2001) provide an overview of constructed wetlands. Wetlands and ground-water treatment have not been examined for treatment of radinucleotide wastes. Except in very few cases, constructed wetlands have not been used in remediation of very hazardous waste. However, in future constructed wetlands might become an option for treatment of radionuclides dissolved in water using rhizofiltration; a phytoremediation method well suited to aquatic environments ( Dushenkov, 2003; Eapen, 2007 ). Integration of radioactive hazardous waste site phytoremediation and constructed wetland technologies requires more research and development.
What is CW in wastewater treatment?
CWs for wastewater treatment can be classified according to the life-forms of the dominating vascular plants and water flow regime. CWs have mostly been used for the purification of wastewater, and to improve water quality in streams, rather than for non-point pollution purification.
What is wetlands used for?
At large scale in developed countries, constructed wetlands have been used as tertiary treatment, focused on ‘polishing’ the discharge by removing further biochemical oxygen demand (BOD), solids, and nutrients. Wetlands also may be used for secondary treatment, decreasing the oxygen demand in wastewater. Such secondary treatment is generally ...
What is secondary treatment in wetlands?
Wetlands also may be used for secondary treatment, decreasing the oxygen demand in wastewater. Such secondary treatment is generally at small scale, such as for a village, a cluster of homes or an isolated industry, agricultural site, or landfill leachate.
Who developed HSSF and VF CWs?
The concept of both HSSF and VF CWs was developed in the 1960s by Käthe Seidel in Germany. Before that, between 1952 and 1956, Seidel carried out numerous experiments on the use of wetland plants for treatment of various types of wastewater, including phenol, dairy or livestock wastewater.
What is a constructed wetland?
Constructed wetlands are engineered systems that use natural functions vegetation, soil, and organisms to treat wastewater. Depending on the type of wastewater the design of the constructed wetland has to be adjusted accordingly. Constructed wetlands have been used to treat both centralized and on-site wastewater.
What are the functions of a constructed wetlands?
Similarly to natural wetlands, constructed wetlands also act as a biofilter and/or can remove a range of pollutants (such as organic matter, nutrients, pathogens, heavy metals) from the water. Constructed wetlands are designed to remove water pollutants such as suspended solids, organic matter and nutrients (nitrogen and phosphorus).
What is a CW wetland?
A constructed wetland ( CW) is an artificial wetland to treat municipal or industrial wastewater, greywater or stormwater runoff. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land development. Constructed wetlands are engineered systems that use natural functions vegetation, soil, and organisms to treat wastewater. Depending on the type of wastewater the design of the constructed wetland has to be adjusted accordingly. Constructed wetlands have been used to treat both centralized and on-site wastewater. Primary treatment is recommended when there is a large amount of suspended solids or soluble organic matter (measured as BOD and COD ).
What are the two types of wetlands?
There are two main types of constructed wetlands: subsurface flow and surface flow constructed wetlands. The planted vegetation plays an important role in contaminant removal. The filter bed, consisting usually of sand and gravel, has an equally important role to play. Some constructed wetlands may also serve as a habitat for native ...
How does a horizontal flow constructed wetland work?
In the horizontal flow constructed wetland the effluent moves horizontally via gravity, parallel to the surface, with no surface water thus avoid ing mosquito breeding. Vertical flow constructed wetlands are considered to be more efficient with less area required compared to horizontal flow constructed wetlands.
Where do subsurface flow constructed wetlands come from?
Subsurface flow constructed wetlands with sand filter bed have their origin in China and are now used in Asia. Subsurface flow constructed wetlands with a gravel bed are mainly found in small cities.
What is a biofilter?
The term of constructed wetlands can also be used to describe restored and recultivated land that was destroyed in the past through draining and converting into farmland, or mining.
How do wetlands improve water quality?
The mechanisms followed in constructed wetlands to improve the quality of water can vary and are often interrelated. The common mechanisms include: The settlement of suspended matter. The water coming in contact with substrate undergoes filtration, chemical precipitation, and chemical transformation by bioremediation and denitrification processes.
How long does it take to read a constructed wetland?
Reading time: 3 minutes. Constructed wetland is a natural wastewater treatment system that uses natural geochemical and biological processes in a wetland ecosystem to treat the contaminants.
What are the advantages of wetlands?
The advantages of constructed wetlands are: 1 Less expensive compared to other wastewater treatment methods 2 Low operational and maintenance costs 3 Facilitate wastewater reuse and recycling 4 Tolerate fluctuations in water flow 5 Provide habitat for wetland organisms 6 Can be constructed harmoniously into the landscape 7 An environmentally-sensitive approach
What is the substrate layer?
The substrate layer provides nutrients and support for the root zone. This is the layer and the root zone where the water flows. The bioremediation and denitrification processes are performed in this layer. Above the substrate layer lies the ground vegetative layer that is either planted or allowed to establish naturally.
What are artificial basins used for?
These artificial basins can be used to treat waste from sludge dewatering, landfill leachate, mine drainage, stormwater, industries, domestic or municipal purpose, and agricultural activities. Constructed wetlands provide a sustainable way to treat polluted water with minimum operation and minimum cost.
What are the components of a wetlands?
Constructed wetlands have three primary components: Impermeable layer of clay. Substrate layer made of gravel. Ground vegetation zone. The impermeable layer is usually made of clay that prevents the filtration of waste down into the lower aquifers.
What is the ground vegetative layer?
Above the substrate layer lies the ground vegetative layer that is either planted or allowed to establish naturally. Constructed wetlands are constructed on uplands and outside floodplains without affecting other aquatic sources.
What is a constructed wetland?
As the name implies, a constructed wetland is artificial—that is, a wetland that is not natural but which human hands have built.
How do constructed wetlands treat water?
Constructed wetlands have three features that remove contaminants from water: vegetation, soil, and microbes. These features work together to significantly reduce the concentrations of contaminants in the water, including arsenic, lead, and zinc.
Why would you use a constructed wetland to treat water?
One of the biggest advantages of constructed wetlands over other water treatment methods is how little maintenance they require. Unlike more active water treatment methods (like water treatment plants), constructed wetlands do not need to be constantly maintained.
Where are constructed wetlands used to treat water?
Constructed wetlands can be used to treat many kinds of water, including agricultural wastewater, industrial water from industries (like the petroleum and pulp and paper industries), municipal wastewater, stormwater runoff, landfill leachate, and mining water.
Bottom line
Constructed wetlands are a low-cost, low-maintenance alternative to other kinds of water treatment. Vegetation, soil, and microbes all work together to treat contaminants in a wetland. They can treat a number of contaminants and different kinds of water, making them a versatile, viable option for many water treatment needs.
What is a constructed wetland?
Basic Form. A constructed wetland is essentially an excavation which is filled with an organic or inorganic particulate media into which reeds are planted. They are generally lined with a rubber (butyl) or plastic (HDPE) material to contain the contaminated water and thus protect ground water and adjacent subsoil.
What are the mechanisms of action in a wetland treatment system?
Constructed wetland treatment systems offer many different mechanisms of action ranging from physical, biological, biochemical and chemical processes and a variety of these mechanisms may be active in any one bed. A list of the principal removal mechanisms is given below.
How have wetland areas been used?
Wetland areas have been used for the informal treatment of wastewater all over the world for hundreds of years. Our ancestors had noted that dirty water passing through wetland areas emerged in a much cleaner state. There is archaeological evidence that the Chinese used this knowledge to their advantage as early as 2000 BC. More recently in the 17th century the Parisians spread wastewater and sludgegathered in simple septic tanks in the centre of the city onto land in the suburbs for treatment.
Where does vertical flow wetlandeffluent drain?
In the most common form of vertical flow wetlandeffluent is not held in the bed but allowed to drain down to the bottom of the bed into a network of collection drainage pipes which then transport the treated effluent out of the bed.
Can clay be used to seal wetlands?
Clay based materials can also be used to seal constructed wetlands providing a more natural alternative. Effluent may be delivered into the system as a continuous flow or in controlled batches.The effluent may move either horizontally across or vertically up or down, through the media depending on treatment requirements.
Summary
Terminology
Overview
Removal of contaminants
A constructed wetland (CW) is an artificial wetland to treat sewage, greywater, stormwater runoff or industrial wastewater. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land development. Constructed wetlands are engineered systems that use the natural functions of vegetation, soil, and organisms to provide secondary treat…
Types and design considerations
Many terms are used to denote constructed wetlands, such as reed beds, soil infiltration beds, treatment wetlands, engineered wetlands, man-made or artificial wetlands. A biofilter has some similarities with a constructed wetland, but is usually without plants.
The term of constructed wetlands can also be used to describe restored and recultivated land that was destroyed in the past through draining and converting into farmland, or mining.
Plants and other organisms
A constructed wetland is an engineered sequence of water bodies designed to treat wastewater or storm water runoff.
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 an…
Costs
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 enter the wetland. Theoretically, wastewater treatment within a constructed wetland occurs as it passes through the wetland medium and the plant rhizosphere. A thin film around each root hair is aerobic due to the leakage …
History
Constructed wetland systems can be surface flow systems with only free-floating macrophytes, floating-leaved macrophytes, or submerged macrophytes; however, typical free water surface systems are usually constructed with emergent macrophytes. Subsurface flow-constructed wetlands with a vertical or a horizontal flow regime are also common and can be integrated into urban ar…
How Are Constructed Wetlands built?
Typhas and Phragmites are the main species used in constructed wetland due to their effectiveness, even though they can be invasive outside their native range.
In North America, cattails (Typha latifolia) are common in constructed wetlands because of their widespread abundance, ability to grow at different water dept…
Mechanism of Constructed Wetlands
Since constructed wetlands are self-sustaining their lifetime costs are significantly lower than those of conventional treatment systems. Often their capital costs are also lower compared to conventional treatment systems. They do take up significant space, and are therefore not preferred where real estate costs are high.
Advantages of Constructed Wetlands
Primary clarifier effluent was discharged directly to natural wetlands for decades before environmental regulations discouraged the practice. Subsurface flow constructed wetlands with sand filter beds have their origin in China and are now used in Asia in small cities.