Introduction
Cattails are a type of wetland plant that have long, thin leaves with cylindrical flower spikes on top. They typically grow in dense stands in marshy or flooded areas. Cattails are well known for their ability to remove pollutants from water, which improves water quality. This occurs through several mechanisms such as filtration, absorption, sediment trapping, and microbial activity around the plant roots. Cattails are considered a natural treatment system and are sometimes used in constructed wetlands to treat wastewater. This content will examine whether cattails effectively improve water quality in natural and engineered systems through an analysis of research studies and real-world examples.
Natural Habitat
Cattails are found naturally throughout wetland habitats in North America. They thrive along the edges of ponds, lakes, rivers, streams, marshes, and swamps (The Nature Conservancy). Cattails grow best in shallow water depths up to about 1 meter deep. They can tolerate both freshwater and brackish water environments (The Nature Conservancy).
The plants grow in dense stands in areas with saturated soils. Cattails propagate quickly to form colonies in muddy areas along waterways. They stabilize shorelines and prevent erosion. Cattails are well adapted to thrive in disturbed wetland areas and will readily colonize newly flooded lands (The Nature Conservancy).
Pollutant Removal
Cattails are highly effective at removing pollutants like nitrogen and phosphorus from water sources. They uptake these excess nutrients through their roots and incorporate them into their tissues as they grow (1). This nutrient uptake can significantly reduce algae growth, as algae feed on nitrogen and phosphorus. With less nutrients available, algae blooms are limited, improving water clarity.
One study found that planted cattail beds removed an average of 78% of nitrogen and 48% of phosphorus from agricultural runoff over two years of growth (2). The nutrient removal effectiveness depends on factors like plant density, growth stage, and pollutant concentrations. But overall, cattails demonstrate a valuable ability to extract problematic nutrients from polluted waters.
Cattails are especially useful for removing nitrogen in the form of nitrates, a common agricultural pollutant. The oxygen-rich environment around the cattail roots enablesconversion of nitrates into nitrogen gas through microbial denitrification (3). This removes the nitrogen from the water system permanently.
With their natural pollutant-removal capabilities, cattails can provide an effective biological water treatment solution. Strategic cattail planting may significantly improve water quality in polluted wetlands and watersheds.
Sources:
(1) https://cleantechnica.com/2009/05/16/cattail-army-deployed-to-fight-water-pollution/
(2) https://www.researchgate.net/publication/272212021_Cattail_Farming_for_Water_Quality_Harvesting_Cattails_for_Nutrient_Removal_and_Phosphorous_Recovery_in_the_Watershed
(3) https://www.sciencedirect.com/science/article/abs/pii/S0043135414002772
Water Filtration
Cattails have natural filtering abilities that help improve water quality. The stems and leaves of cattail plants act as a filter to trap sediment as water flows through them. Their dense growth forms a net that can capture quite a bit of particulate matter. This includes trapping silt, clay, and various organic particles https://www.producer.com/crops/cattails-suck-floating-water-filters/.
One study created floating cattail rafts to filter greywater and test their pollutant removal abilities. They found the cattail filtration system significantly reduced levels of phosphate, cyanuric acid, and alkalinity in laundry greywater. It also helped regulate pH levels https://projectboard.world/project/greywater-filtration-using-common-cattail.
Overall, the dense structure of cattail leaves and stems provides an effective natural filtration system for sediment and particulate matter in water.
Denitrification
Cattails have been shown to enhance denitrification, which is the process by which anaerobic bacteria in the soil around the plant’s roots convert nitrates to nitrogen gas, removing it from the ecosystem.1 One study found that cattail-invaded wetlands supported a greater diversity and richness of denitrifying bacteria compared to uninvaded wetlands.1 Additional research demonstrated higher rates of denitrification enzyme activity in sediment with cattails compared to other wetland plants.2
This nitrogen removal through denitrification can help reduce eutrophication, which is the excessive buildup of nutrients like nitrates and phosphates that leads to increased algae growth and reduced oxygen levels.3 By converting nitrates to inert nitrogen gas, cattails can intercept and reduce nitrogen runoff before it reaches lakes, rivers, and other water bodies.
Limitations
While cattails can help improve water quality in ponds and wetlands, they have limitations in their ability to treat serious pollution problems. According to Advantages and Disadvantages of Cattails in Storm Water Management Facilities, cattails alone cannot solve heavy pollution from industrial sources or overwhelmed sewage systems. Their capacity to absorb nutrients and contaminants can be overwhelmed by high concentrations of pollution.
Additionally, cattails require specific habitat conditions to thrive and maximize their water treatment capabilities. They need wet, marshy areas with access to sunlight and cannot survive being fully submerged. As noted in Cattails Suck: Floating Water Filters, cattails do not perform as well in absorbing pollutants when water levels are too high. While useful, cattails have limits in the degree of water pollution they can treat.
Case Studies
Cattails have been used extensively in constructed wetland projects to filter wastewater and pollutants. One case study in Texas examined a constructed wetland system planted with cattails to treat municipal wastewater. Over a two year period, the system removed 84% of biochemical oxygen demand, 89% of total suspended solids, 79% of total nitrogen, and 85% of total phosphorus (Dobberteen, 1991).
Another case study in British Columbia, Canada evaluated using constructed wetlands to treat wastewater from a campground. The planted cattail cells removed an average of 76% of total suspended solids, 51% of total phosphorus, and 49% of total nitrogen (Wang, 2018).
These studies demonstrate that constructed wetlands utilizing cattails can effectively reduce many common pollutants found in wastewater, including solids, nutrients, and organic matter. The nutrient removal efficacy does vary based on factors like hydraulic retention time and loading rates. Overall, cattails have proven to be an accessible natural treatment solution for improving water quality.
Cultivation Methods
Cattails can be an effective natural way to improve water quality when cultivated properly. Here are some tips on how to effectively grow cattails for water treatment:
Cattails thrive in shallow, slow-moving or stagnant water that is rich in nutrients. Ideal conditions are freshwater ponds, marshes, and along the edges of lakes and streams. The water level should be 6 inches to 3 feet deep. Cattails can be grown in individual containers or small clumps spaced 3-4 feet apart near the edge of a water body. Make sure to situate cattails where they will receive plenty of sunlight.
Cattails can be started from seed, sprouts or mature plant divisions. Seeds should be planted in trays filled with wet soil and kept moist until germination. Once sprouts are 4-6 inches tall they can be transplanted into the desired location. Divisions of a mature cattail plant can also be potted and replanted. Plant cattail sprouts or divisions about 1 foot apart.
Cattails require nutrient-rich sediment and periodic fertilization for optimal growth. Apply a balanced fertilizer into the water near the cattail roots every 2-3 weeks during the growing season. Prune dying leaves and stems annually to encourage new growth.
With the proper conditions, cattails can spread rapidly and create dense stands that maximize their natural water filtration capabilities. Routine maintenance is important to prevent overgrowth and maintain effectiveness for water treatment.
Additional Benefits
Cattails provide important habitat for wildlife. Their dense stands offer shelter and nesting sites for many types of birds, including red-winged blackbirds, marsh wrens, and ducks. Mammals like muskrats and deer also utilize cattails for food and cover. The plant’s ability to uptake nutrients helps keep algae growth in check, improving water clarity and quality for fish and other aquatic organisms.
As a wetland plant, cattails are excellent carbon sinks. They absorb carbon dioxide from the atmosphere and incorporate the carbon into their tissues as they grow. Much of this carbon gets stored below ground in the rhizomes and roots. When the plants die, the carbon remains sequestered in the soil. Cattail stands can sequester 2-15 tons of carbon per acre per year.[1]
The beauty of cattails adds aesthetic value to wetland landscapes. Their tall stalks and brown, fluffy seed heads create visual interest and texture. Cattails are frequently featured in art, photography, and decorative floral arrangements. Their ability to clean water also helps maintain healthy, vibrant ecosystems people enjoy.
Conclusion
Cattails are native plants that naturally exist in wetland ecosystems around the world. They have a complex root system that helps filter pollutants from water, remove nitrogen through denitrification, and reduce erosion along shorelines.
Studies have shown cattails can effectively remove heavy metals, excess nutrients, and other contaminants from polluted waters if properly cultivated. Their fibrous stems slow water flow, allowing pollutants to settle out. The plant also secretes antibacterial compounds from its roots to prevent disease.
However, cattails alone cannot solve serious pollution issues. They work best when integrated into a comprehensive ecological restoration plan for filtering runoff. Proper management is required to prevent overgrowth. While cattails have demonstrated an ability to improve water quality, their full potential requires further research.
In conclusion, cattails can be an important part of natural, low-cost methods for reducing pollution in lakes, ponds, wetlands and other aquatic ecosystems. When sustainably planted and cared for, their unique root systems and natural filtration abilities make them one of nature’s water cleansers.