A reed bed system is an effective way of dealing with effluent waste independently, by harnessing the naturally cleansing powers of wetland eco systems. They are a popular and low-impact form of drainage on organic farms and for properties with sufficient space who wish to take their drainage off the grid and treat their waste water without the need for chemicals.
A reed bed is essentially a large-scale pond into which liquid effluent, such as the outflow of a septic tank, is channelled. The reed bed is home to a number of flora and fauna, including a high concentration of reeds. These help to oxygenate the waste, allowing micro organisms in the bed to work to break it down and turn it into harmless matter.
Constructing a reed bed system
To construct a reed bed system, you need a sufficient amount of space- about the size of half a tennis court. Like a pond, a large hole needs to be dug and lined to avoid water seepage. This is most commonly done with concrete for durability. The size of the hole should be based on the volume and flow rate of effluent water, and generally averages as five square metres per person in the household. The hole is filled with gravel or soil in order for the reeds to take root. The waste water will be delivered into the reed bed either below the water level via a horizontal feeder trench or from above the surface via a vertical flow system.
Horizontal vs vertical deliver systems
Whether you choose to use a vertical or horizontal delivery system for your reed bed depends on the strength of the effluent you wish to treat.
Horizontal flow reed beds are effective when treating lower strength effluents, or ones which have been pre treated in the septic tank. They work to reduce biochemical oxygen demand (BOD) and suspended solids (SS). They help to convert nitrates into nitrogen gas, though they are less effective at reducing ammonia levels in the waste.
Vertical flow reed beds are effective when treating high strength effluents, and therefore work well as standalone treatment systems. They are able to control levels of BOD and SS effectively whilst also breaking down ammonia, which reduces bad smells significantly.
How reed bed systems work
Reed bed systems use a biological process to treat waste water and make it safe. They combine the cleansing properties of soil dwelling microbes, the properties of the base materials- gravel, soil or sand, and the chemical processes performed by the plants themselves. Reed beds are intended to mimic a wetland ecosystem. Wetland plants are known for their aerating properties, transferring oxygen down to their roots below the surface in order to survive in waterlogged conditions. The processes which take place below the surface are both aerobic and anaerobic, so the variety of microbial species within the ecosystem is huge.
The complex root systems of the plants within the reed bed play an important role in treating the waste water. They filter the water by allowing it to pass through their maze of channels, whilst helping aerobic bacteria to thrive within the soil by drawing in oxygen. Aerobic microbes are essential in breaking down ammonia- one of the key harmful chemicals found in sewage, and turning it into nitrate. The reed bed also benefits the plants, delivering a number of essential nutrients to them which encourages healthy growth.
The microbes found within the reed bed system are highly effective, and, when helped along by the plants, are able to transform a number of potentially harmful chemicals into safe and even beneficial ones, maintaining a healthy equilibrium within the ecosystem.
Who can benefit from a reed bed system?
Reed bed systems can be used on a domestic or industrial scale, provided there is enough space to accommodate one. They are especially popular with owners of farms or smallholdings as a sustainable way of treating water by working with a natural biological process rather than simply sterilizing the waste water with treatment chemicals.
Reed bed systems in action
Solid waste cannot be added directly to a reed bed system, as it would simply starve the plant roots of oxygen. Instead, waste water needs to flow to a septic tank (often, your current septic tank can be used to save costs) where solid waste can be removed. Liquid effluent is collected in a feeder tank via gravity flow, and is then passed to the reed bed either via gravity flow or a pump, where the treatment process begins. The reed bed system will actively treat waste water all year round, though the rate of treatment is much higher during the summer months.
When it comes to discharging water from your reed bed system, you will need to contact your local authority, who will suggest a safe and legal way to do so.
Image sourced: Steve Farehamtagsdrainagereed bed systemwater treatment