Reed Bed: A Green Waste Water Treatment Option

A reed bed is an alternate method for sludge treatment. Reed beds have been applied for the treatment of domestic effluents in rural communities, where the relatively small volumes of effluent may mean that conventional systems are not cost-effective. They are also seen as a 'green' water treatment technology, incorporating fit with the landscape, ecological added value, by providing habitats for wildlife, and sustainability.

The proper utilization and disposal of sludge is one of the most critical issues faced by wastewater treatment plants. Landfill costs are increasing, while incineration permits are expensive and difficult to obtain. However, constructed wetland technology such as reed beds provide long-term storage and volume reduction of bio solids to mitigate these concerns.

A reed bed is a natural form of domestic or industrial waste water. Reed bed systems are an effective, sustainable and low maintenance method of sewage treatment. Aesthetically pleasing to the eye, it requires no electricity and once matured provides an ecological habitat for a wide range of species. Reed beds are subject to Environment Agency Permitting guidelines. This method is widely used throughout Europe, Asia, Australia, and United States.

Reed beds are natural habitats found in floodplains, waterlogged depressions and estuaries. Artificial reed beds are used as a method of removing pollutants from gray water. Reed beds use common reed plants to dewater solids in a confined area. The beds can be any shape to accommodate existing land conditions and areas.

How Do Reed Beds Work?

The Common Reed (Phragmites Australis) has the ability to transfer oxygen from its leaves, down through its stem, porous speta and rhizomes, and out via its root system into the rhizosphere (root system.) As a result of this action, a very high population of micro-organisms occurs in the rhizosphere, with zones of aerobic, anoxic, and anaerobic conditions. Therefore with the wastewater moving very slowly and carefully through the mass of reed roots, this liquid can be successfully treated, in a manner somewhat similar to the conventional biological filter bed systems of sewage treatment plants.

Earlier reed bed sewage treatment systems used the horizontal flow type of reed bed, where the liquid flows horizontally through the bed, but it is essential that any form of treatment of sewage should have the capability to not only treat the sewage effectively, but also that its maturation time should be kept to a minimum. To achieve this the reed plants are partially pre-grown, and also with the development of a vertical reed bed system, this maturity of the total system can be more readily achieved. Reed Bed Sewage Treatment Systems can be used to treat a variety of pollution loadings, but great care must always be exercised in their design and implementation.

Types of Reed Beds

Horizontal Flow (HF Systems) : The effluent enters at one end and travels horizontally through the reeds root zone, before being discharged on the far side of the bed. The Common Reed Phragmites australis is able to transfer oxygen from its leaves, down through its stem and rhizomes into the gravels around the root system creating a high population of micro organisms.

Vertical flow (VF Systems) : The reed beds are lined with deeper structures made up of layers of various sized gravels planted with reeds. In this system effluent is delivered to the top of the bed in batches, floods the surface of the bed and drains through. Each batch traps oxygen in the bed leading to an aerated system. VF systems are more effective than HF systems at ammonia removal due to increased oxygen levels within them. VF systems have a smaller footprint than HF systems and can cope with stronger effluents.

Merits :

• minimizes solids
• reduces water content
• minimal day-to-day operation
• no requirement of highly trained operators
• mechanical and electrical equipments are needed
• pumping not necessary as the system works on gravity
• provides sufficient storage time to stabilize bio solids prior to disposal
• blowers to aerate is not required as the aeration is facilitated by reeds

Demerits :

• Large land area is required for correct treatment