Treatment is achieved by a variety of physical, chemical, and biological processes, such as sedimentation, filtration, precipitation, sorption, plant uptake, microbial decomposition, and nitrogen transformations (Wetzel, 2000; Kadlec and Wallace, 2008).
Full Answer
What is a Constructed Treatment Wetland?
"Constructed treatment wetlands are engineered systems, designed and constructed to utilise the natural functions of wetland vegetation, soils and their microbial populations to treat contaminants in surface water, groundwater or waste streams”1+ 2.
What is a wetland system and how does it work?
Wetland systems have always served as natural water treatment systems. During the past few decades people have seriously studied and utilized wetland systems for meeting wastewater treatment and water quality objectives in a controlled manner.
What are the three main components of wetlands?
Constructed wetlands have three primary components: The impermeable layer is usually made of clay that prevents the filtration of waste down into the lower aquifers. The substrate layer provides nutrients and support for the root zone. This is the layer and the root zone where the water flows.
How many wetland treatment systems are there in the US?
Constructed Wetlands for Wastewater Treatment and Wildlife Habitat: 17 Case Studies (EPA832-R-93-005) This document provides brief descriptions of 17 wetland treatment systems from across the country that are providing significant water quality benefits while demonstrating additional benefits such as wildlife habitat.
How are wetlands treated?
What Types of Treatment Wetlands are Used? Three types of treatment wetlands are typically used for water quality improvement: natural treatment wetlands, constructed surface flow treatment wetlands, and subsurface flow treatment wetlands. Each of these alternatives is briefly described below.
How do constructed treatment wetlands work?
Constructed wetlands are designed and built similar to natural wetlands to treat wastewater. They consist of a shallow depression in the ground with a level bottom. The flow is controlled in constructed wetlands so the water is spread evenly among the wetland plants.
What are the three main types of constructed wetlands?
The three types of constructed wetlands discussed in this chapter are: 1) horizontal subsurface flow constructed wetlands, 2) horizontal free water surface flow constructed wetlands, and 3) vertical flow constructed wetlands. Constructed wetlands have been used to treat both centralized and on-site wastewater.
What kind of primary treatment happens before the water reaches the wetland?
In a constructed wetland system for domestic use, wastewater first flows to a septic tank which acts as a primary treatment system. Here solids are settled. From the septic tank, the effluent flows through a perforated inlet or distribution pipe buried in rock or gravel into vegetated submerged beds.
Why are constructed wetlands used for wastewater treatment?
Constructed wetlands are designed to remove water pollutants such as suspended solids, organic matter and nutrients (nitrogen and phosphorus). All types of pathogens (i.e., bacteria, viruses, protozoan and helminths) are expected to be removed to some extent in a constructed wetland.
How Do wetlands perform secondary treatment?
The biological removal of waste in secondary treatment is also done by the wetlands through aerobic consumption.
What is constructed wetland system?
A constructed wetland is an organic wastewater treatment system that mimics and improves the effectiveness of the processes that help to purify water similar to naturally occurring wetlands.
What is the main purpose of constructed wetlands?
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.)
What are integrated constructed wetland?
Integrated Constructed Wetlands (ICW) are landscape features which are used to treat foul runoff using naturally occurring vegetative processes, whist contributing to the surrounding amenity and biodiversity value of the site and wider landscape.
What is floating treatment wetland?
Floating treatment wetlands (FTWs) or islands are small artificial platforms that allow these aquatic emergent plants to grow in water that is typically too deep for them. Their roots spread through the floating islands and down into the water creating dense columns of roots with lots of surface area.
How do wetlands provide flood protection?
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.
What are the 3 primary pollutants that are filtered out of the water by the wetland?
Three pollutant removal processes provided by wetlands are particularly important: sediment trapping, nutrient removal and chemical detoxification.
Who developed the guidelines for the construction of wetlands?
Answers to common questions. The Guiding Principles were developed by the Interagency Workgroup on Constructed Wetlands (U.S. Environmental Protection Agency, Army Corps of Engineers, Fish and Wildlife Service, Natural Resources Conservation Services, National Marine Fisheries Service and Bureau of Reclamation).
What is a wetlands?
Constructed wetlands are treatment systems that use natural processes involving wetland vegetation, soils, and their associated microbial assemblages to improve water quality.
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.
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.
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.
What is a wetlands system?
Constructed treatment wetlands are engineered wastewater purification systems that encompass biological, chemical, and physical processes, which are all similar to processes occurring in natural treatment wetlands. They are implemented for environmental pollution control to treat a variety of wastewaters, including industrial effluents, urban and agricultural runoff, animal wastewaters, sludge, and mine drainage (Scholz and Xu, 2002; Picard et al., 2005; Scholz and Lee, 2005 ). Recently, some large-scale wetland systems have also been successfully applied to treat domestic wastewater ( Scholz, 2010; Dong et al., 2011 ). However, there are few long-term and controlled studies involving domestic wastewater, owing to health and safety concerns.
Why are wetlands important?
Treatment wetlands have become popular both because they have a 'green' image and low operating costs. Wetlands have been used to effectively remove BOD and SS , and in some cases limited nutrient removal is observed . They have also been successfully used to neutralize pH and remove metals from mine impacted waters.
What is wastewater treatment?
In wetlands treatment, wastewater, usually pretreated to a rather high degree in the case of natural wetlands, is allowed to flow, very slowly, through the wetlands system. Bacteria, fungi, and many other types of organisms inhabit the aqueous medium and use pollutants contained in the wastewater for food.
How many cells per ml of protozoa?
Protozoa are plentiful in constructed treatment wetlands, AS and other polluted mixed liquors (up to about 50 000 cells per ml). Protozoa species and their abundances can be related to water and wastewater treatment processes, and their corresponding water quality.
What plants are used in wetlands?
In the case of artificial or constructed wetlands, protection of groundwater by installation of an appropriate liner is a major design consideration. Reeds, cattails, sedges, and bullrushes are types of emergent plants that have performed well in wetlands treatment systems.
Is a treatment wetland noisy?
Although the day-to-day performance of a treatment wetland is ‘noisy,’ performance is not poor. Broadly speaking, steady flows, steady loads, and stable temperatures improve performance. The wetland nevertheless should be sized not for steady averages, but rather for the expected worst case conditions.
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.
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.
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.
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 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 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.
Basic Form
Treatment Principles
- 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.
Constructed Wetland Types
- As outlined above different types of constructed wetlands have evolved over the years driven by the changing needs of clients and increased range of applications. Constructed wetland designers have, through necessity, had to innovate, develop and combine forms as required. An indicative list of systems is given at the end of this section but the principle types are outlined b…
Basic Types
- These are the fundamental forms of constructed wetland which differ only in the direction of effluent flow
How Are Constructed Wetlands built?
Mechanism of Constructed Wetlands
- As mentioned above, a constructed wetland is a composition of water, substrate, plants, invertebrates, and an array of microorganisms. The mechanisms followed in constructed wetlands to improve the quality of water can vary and are often interrelated. The common mechanisms include: 1. The settlement of suspended matter 2. The water coming in contact wit…
Advantages of Constructed 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...