A Reed Bed Wastewater Filtration System is constructed using planted reed vegetation floating on top with the roots embedded into sand bed or rock layer at the bottom to form narrow trenches and allow wastewater or sludge to pass through beneath the plants’ bacterial populated rhizome network. The bed will usually come complete with an underdrain piping system located below the supporting bed to collect back the percolate and return it to the treatment plant for further processes. The system has several uses mainly that acts as a tertiary biological purification option to filter and improve the quality of wastewater or in other applications, can also be applied towards control of landfill generated leachate. Apart from that it is also a workable solution for sludge dewatering purpose which has become a standard practice largely used in Europe and North America.
The working principle of a reed bed system is actually more or less similar compared to an artificial wetland construction except that instead of the water flowing downwards, it is now moving horizontally and the roots network in its way, it will slow down the flow. The root systems of the plants are actually capable to trap the sludge solids and absorb the water which are then lost through evapotranspiration going to the atmosphere. This will help to concentrate and reduce the liquid content of the sludge solids and biological action of the bacteria populating the rhizomes will help to breakdown the waste using the available oxygen provided by the plants. It is considered the most effective plant-based treatment system because overall, based on yearly assessment and analytical research, it is concluded that there are huge reduction of the water content which means it is an Eco-friendly approach without the needs for huge investment and energy input and yet capable of producing wastewater discharge with low COD level.
Compared to sand drying beds for sludge dewatering, this setup has several advantages, the fact that it can withstand sludge accumulation and hold on with this current condition for several years without affecting performance and degrading the capability to treat high COD load. Sand drying beds on the other hand, would always require immediate attention to remove accumulated solids or else the crust that forms on the surface will drastically affect the water evaporation. The only problem that affects efficiency in reed bed process is that the wastewater feed to the unit should have low organic content or else, it will overwhelm the treatment capability of the reeds and in worse case situation will kill the vegetation. Normally depending on whether the feed wastewater sludge is aerobically or anaerobically digested in the earlier processes, the solid should not exceed 4% or else with increased loading rate, it will prevent the system from operating at its peak.
Design and construction of the reed bed treatment facility is very much similar to the sand drying beds and the material needed for the setup can be easily sourced locally without escalating the project cost. These days there are even small-scaled plants which can be easily built to serve residential and individual home treatment requirements like sewage and generation of effluent wastewater. Usually for those systems that are built and operate as part of a large treatment facility, special considerations have to be carefully studied with possible cases related to seepages and how to prevent incidence of groundwater contamination. Thus it is important that there should be a liner put in place and with groundwater monitoring wells used for periodic checking of the water quality.