Reed Beds – An Introduction

SCALE                                                                                                  

Constructed reed beds can be created for most scales of operation, from the very large to the very small with the size determined by the wastewater to be treated, the volume, the organic / pollution loading of the liquid and the location.

HOW THEY ARE MADE                                                                       

In general reed beds are constructed out of natural local resources, such as earth banks and clay liners or they can be “more constructed” using some form of containment wall, such a concrete blocks or timber frame with an impermeable rubber/butyl liner. The void space is generally filled with graded gravel or soil gravel matrix and planted with Phragmites australis or other hydrophytes at close spacing. These plants encourage opening up of void spaces to allow wastewater to progress through the matrix, as well as facilitating oxygen transfer to aerobic zones in the matrix and providing a sink for nutrients.

TYPES OF REED BED                                                                         

There are several types of constructed reed bed, but the two main types being horizontal and vertical flow, each performing slightly different tasks. Ideally reed bed systems should be constructed to make the most use of any fall to allow the movement of water through the system via gravity, this reduces operating costs and the reliance on power for pumps and flow systems.

WHAT IT TREATS

In essence constructed reed beds treat liquid waste by removing organic matter, reducing BOD:COD, oxidising ammonia, reducing nitrate and removing phosphorus. The processes are complex involving bacterial oxidation, filtration, sedimentation and chemical precipitation.

SONY DSC    Floating Reed Bed

Constructed Reed Bed     dsc00326