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Reed Bed Treatment Systems

Reed bed treatment systems are self-contained, artificially engineered, wetland ecosystems. They are designed to optimise the microbiological, chemical and physical processes naturally occurring in the wetland. Wetland plants, such as reeds, transfer atmospheric oxygen down through their roots in order to survive in waterlogged conditions. This creates both aerobic and anaerobic soil conditions, allowing extraordinary microbial species diversity to flourish. These bacteria and fungi can use organic pollutants as a food source, breaking down a wide range of organic chemical products. So, chemicals are not simply stored in the reed bed; they are actually degraded into harmless components. Other contaminants, such as metals, are transformed from a toxic, mobile state and fixed in the soil via complex chemical reactions. Soils adsorption capacity also provides a buffer for peak or shock effluent loads.

The complexity of microbial life and powerful reactions within the root zone of the soil based reed bed result in an extraordinary water cleaning capability. This capability is often far less constrained than in many chemical or physical wastewater treatment systems.

The plants within the reed bed system have three main functions:

  • They provide the means for secondary restructuring of the soil system. The very extensive root and rhizome system creates channels for the water to pass through and also keeps the soil open through the constant growth and die back of the root system.
  • The roots of the aquatic plant introduce oxygen down into the body of soil, providing an environment where aerobic, or oxygen dependent, bacteria can thrive. Such bacteria are required for the effective breakdown of many types of compounds, and the plants allow them to thrive.
  • The plants are capable of taking up a certain amount of nutrient from the wastewater themselves.

Reed beds are suitable for treatment of organic contaminants, either natural or synthetic, and some inorganic contaminants are also withheld or converted to safe products within the substrate of the reed bed system. Some of the contaminants that can be tackled in reed bed systems are as follows:

  • Biological Oxygen Demand (BOD) & Chemical Oxygen Demand (COD)
  • Ammonia
  • Heavy metals, suspended solids, sewage 
  • Organic petrochemical derivatives including diesel and various solvents
  • Phenol and phenolic compounds
  • Pesticides &
  • Faecal coliforms, bacterial contamination etc.

Reed bed treatment systems essentially comprise self-contained artificially engineered wetland ecosystems. They utilize particular combinations of plants, soils, bacteria, substrates, and hydraulic flow systems to optimise the physical, chemical, and microbiological processes naturally present in the root zone.

Treatment is possible due to the special characteristics of wetland plants, such as reeds, which transfer substantial amounts of atmospheric oxygen through their root systems. This role of the plants encourages an extraordinary quantity of species diversity of microorganisms to flourish in the soil around the plant roots.

The breakdown of contaminants is achieved by the controlled seepage of the water borne pollutants through the root zone of the wetland plants. Organic pollutants are broken down as a food source by microorganisms and the plants, while other contaminants, such as metals and PCBs, are fixed in the humic acid (and via cation exchange bonds) in the soil or mineral substrates in which the plants are rooted.

The complexity of microbial forms and powerful reactions within the root zone of the oil based reed bed result in an extraordinary water cleaning capability. This capability is often far less constrained than in many chemical or physical treatment systems.

 

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