Introduction Of Constructed Wetlands Septic System
A constructed wetland would be an organic wastewater treatment method that matches and increases the performance of natural wetlands’ purification processes. The design allows the use of water, aquatic plants, naturally existing microbes, and a filter bed.
Wetlands could be used for secondary or tertiary wastewater treatment.
There are numerous designs available, including vertical wetlands, that need less acreage but take more energy for activities such as pumping or siphoning than horizontal wetlands, which can rather rely on gravity as well as terrain.
The numerous design, material, and technology possibilities allow the created wetland to be tailored to local conditions and land availability.
The cost of manmade wetlands is determined by the cost of land and materials, but where land is inexpensive and widely available, they are a very cost-effective technique of wastewater treatment.
The plants, microbes, and substrates, in general, operate as a filter and purification system. First, water is delayed as it reaches the marsh, allowing sediments to settle. Plant roots and the substrate filter out bigger particles in the wastewater as water flows through the built wetland.
Pollutants including nutrients in sewage are therefore organically broken down and pulled up by groups of bacteria, allowing them to be removed from the water.
The pathogens contained in wastewater will be killed by the retention duration in the wetland, which varies based on the design and desired quality level, as well as UV light and plant secretion of antibiotics.
Water that has been treated in a built wetland can be safely discharged into surface waterways or used for a variety of purposes.
What Is Constructed Wetland?
Constructed wetland (CWs) is a low-cost wastewater treatment method that may efficiently treat wastewater without the use of chemicals or mechanical devices.
However, because the pollutant removal procedures involved in CWs are relatively delayed, adopting CWs to treat wastewater necessitates a considerable land-use footprint.
Types of Constructed Wetlands
Here, the different types of constructed wetlans are as follows.
1. Constructed Wetlands for Habitat Creation:
The goal of these systems is to create wildlife habitats. The major purpose is to take advantage of CWs’ fundamental ecological benefits, not just their role as a therapeutic center.
The major properties of CWs make them ideal for developing an ecological habitat by attracting wildlife, particularly birds, and creating a green space.
There are four different sorts of CWs that can be made:
- Ponds, which may or may not have a suitable depth for fish.
- Herbaceous plants grow in marshes, which are usually shallow watery areas.
- Swamps with a lot of trees.
- ephemeral wetlands are seasonal wetlands that gather water. These systems can also be used as food and fiber sources, as well as public recreation areas.
2. Constructed Wetlands for Flood Control:
The purpose of these wetland systems is to collect runoff during floods. Their adoption might enhance stormwater storage capacity and infiltration volumes while lowering water entering the sewage system and treatment facilities.
These technologies may contribute to Integrated Urban Water Management and give the capacity to recycle the stored water volume within the urban hydrologic cycle.
3. Constructed Wetlands for Wastewater Treatment:
These engineered wetlands are designed to accept and cleanse various types of wastewater using naturally occurring treatment processes.
Depending on the unique parameters of the system, such as the kind of vegetation or the direction of water flow through the system, CWs for wastewater treatment can be further classified into different categories.
There are two sorts of flow paths in a system, depending on the flow path:
- Free water surface constructed wetlands (FWS CWs)
- Subsurface flow constructed wetlands (SF CWs)
Water flows slowly above a substrate medium in FWS CWs, resulting in a free water surface and a water column depth of a few centimeters.
In SF CWs, on the other hand, water flows through a porous substrate. SF CWs can be classified as horizontal (HSF) or vertical (VHF) depending on the flow route direction (VF). Another categorization might be formed based on the vegetation’s growth characteristics.
As a result, the following distinctions can be made:
- Floating treatment wetlands (FTWs) (Floating Islands),
- Emergent macrophyte wetlands, and
- Submerged macrophyte wetlands.
How a Constructed Wetland System Works?
Constructed wetlands are meant to look like natural wetlands and treat wastewater with plants and microbes.
A built wetland system consists of a septic tank, wetland cell(s), and a mechanism for returning treated wastewater to the environment, such as a drainfield if the soil is suitable, or a polishing lagoon or wildlife habitat pond if the soil is not adequate.
The wastewater is treated first in the septic tank. Solids settle to create a sludge layer, while greases and oils float to form a scum layer, while anaerobic bacteria begin to break down wastes.
The cleared middle layer makes its way to the wetland cell that has been built.
There are two main types of wetlands.
Because wastewater flows on top of existing soil, surface-flow wetlands resemble natural wetlands. They are more cost-effective when it comes to treating huge amounts of wastewater, such as those produced by cities.
The subsurface-built wetland is a gravel cell meant to keep wastewater below the surface for 1 to 3 inches. Mosquitoes are kept at bay, and there is little risk of human interaction with the effluent.
The cell is planted with cattails, bulrushes, reeds, and other aquatic plants. Organic elements in wastewater are broken down by microorganisms dwelling on the surface of gravel stones and plant roots.
In turn, the plants supply oxygen to the cell while also removing some nutrients from the effluent. Some of the wastes settle on the surface of the particles and adhere to them.
Effluent from the wetland passes via a water-level control sump, which allows the water level in the wetland to be controlled. This is critical because the water level in the wetland must remain below the gravel surface to avoid smells while still being high enough to prevent plant roots in the cell from drying out or freezing.
Water levels in the wetland cell may occasionally dip to more than 3 inches below the surface. This is allowed on a recurring basis since it allows for the growth of plant roots.
If the soil and site conditions are adequate, wastewater flows from the built wetland to a subterranean drain-field, where it is treated by microorganisms and soil before being discharged back into the environment.
If the soil isn’t appropriate for a drain field, the effluent may be sent to a polishing lagoon or a wildlife habitat pond, where it will be further treated. Unless permission is acquired, discharge of surface water to land or natural bodies of water is unlawful in Nebraska.
Effluent evaporates into the air and seeps into the soil from the polishing lagoon or habitat pond. The rate of seepage must not be more than 1/8 inch per day.
Constructed Wetland Septic System Cost
A constructed wetland system costs $6,000 to $10,000 on average. This is a one-of-a-kind in-ground system that looks like a marsh. The wastewater is pumped from the tank into a wetland cell.
A liner, gravel, sand, and wetland plants are commonly used to construct wetland cells. Because the plants will always be moist, they must be carefully packed.
The water goes into the wetland cell, where the waste is filtered out by plants, sand, and gravel. After that, the water is discharged into a drain field. Gravity or a pump can be used in this setup.
Advantages of Constructed Wetlands Septic System
Here, the pros of constructed wetlands septic system are as follows.
- Constructed wetlands are a potential solution for water/wastewater treatment and pollution reduction. They fall within the umbrella of natural therapy techniques.
- The primary concept is to use natural materials and naturally occurring processes for treatment under regulated circumstances.
- Constructed wetlands have been described as an ecologically beneficial, long-term technique that offers several economic, ecological, technological, and sociological advantages.
- It is a rapidly developing technology that may be used to treat household, municipal, and industrial wastewater, as well as sludge dewatering and drying.
Disadvantages of Constructed Wetlands Septic System
Here, the cons of constructed wetlands septic system are as follows.
- Large land area requirements, the necessity for a pre-treatment of wastewaters before they are treated by the system, the need for a longer retention period, and the possibility of pest issues
- When flowing into a water body, nutrient-rich streams may lose part of their nutrient content as they travel through wetland plants.
- The establishment of vegetated wetland buffer zones along rivers has proven to be beneficial in reducing non-point source pollution and improving river water quality.
- Wetland buffer zones can reduce nutrient, pesticide, and sediment concentrations in surface runoff, preventing water quality degradation in lakes, streams, and rivers.
- This implies that artificial wetlands may and should be included in management plans for the protection of a watershed’s soil and water resources, or as part of larger restoration efforts.