FilterPod for failing reed bed systems
FilterPod Trickling filters as an ideal sewage treatment solution versus reed beds
The sustainability and operation of reed beds has recently been subject to re-evaluation. Recent studies have shown that all horizontal flow reed beds clog with biomass, sludge and organic material within 7 to 10 years of their construction. This results in the whole reed bed, gravel and all, needing to be replaced. You cannot 'clean' it without the complete removal of the gravel bed. This can, in theory, be 'washed' clean, but in practise, without hugely expensive cleaning machinery, is impossible and new gravel must be bought. The problem then is the disposal of the old gravel, as this is contaminated waste and very expensive to recycle..
This re-evaluation also includes Northern Europe and other regions which experience colder winters.
Many reed beds freeze during particularly cold winters, such as that experienced in the UK in 2010.. Frozen reed beds will not accept any liquid flowing into them and the effluent backs-up into the septic tank or sewage plant, preventing the use of toilets, baths, washing machines, etc. - in short, making your house unlivable.
The FilterPod sewage treatment system is now accepted as the ideal non-electric sewage treatment solution by wastewater professionals who have re-examined the limitations and running costs of reed beds.
The FilterPod is, in effect, a 'Vertical' Trickling Filter. Reed beds are also filters, but to understand the differences, you must understand reed bed technology
Reed beds were developed about 25 years ago as a natural, eco solution for treating sewage effluent. All sewage treatment systems work by reducing the levels of BOD (Biochemical Oxygen Demand), SS (Suspended Solids) and Ammoniacal Nitrogen in raw sewage to very low levels.
The Design of Reed Beds
There are several different types of Reed Beds:
- Horizontal flow only
- Vertical flow only
- Multi-stage systems incorporating several stages of horizontal or vertical flow
The Horizontal Flow reed beds can only be used for further treatment of effluent from a sewage treatment plant (tertiary treatment) Vertical flow and multi-stage reed beds can be used for septic tank effluent treatment or for tertiary treatment after a sewage treatment plant. The type of reed bed used depends on the nature and strength of the effluent flowing into it and the required quality of the final effluent.
Operating principle of Reed Beds
The common reed, Phragmites australis, is normally used in a planted gravel filter bed. The bed develops aerobic micro-organisms that digest the pollutants in sewage. The oxygen required for this bacterial development is transferred from the plant leaves down through its stem and roots resulting in bacteria growing in the gravel bed. The sewage effluent flows through this gravel bed and the micro-organisms digest the pollutants.
Reed bed systems can be 100% non-electric, but the site MUST have a good gradient. If the site is flat, then electric pumps have to be used to lift up the water to higher levels.
Power Requirement
Even if most sites with decent gradients enable gravity sewage water treatment, the need for electrical power can be necessary when designing a reed bed system in order to ensure that the flow of wastewater doesn’t flood the system
Planted filters - life span
Reed beds may be a long term solution when designed and maintained properly; however site experiences show that most planted filters may only be viable for up to 10 years.
Maintenance of reed beds
Reed bed systems require regular maintenance to keep them working properly and delivering the expected treatment results. This includes regular weeding and re-planting, raking the beds level to prevent 'preferential Pathways' developing over the beds, the cutting and removal of ALL dead reeds in the autumn, to prevent it from rotting and clogging the gravel bed. The primary tank needs to be emptied when required - normally every year.
Refurbishment of reed beds
Clogging often occurs at the inlet or at the outlet of the bed. A blockage at the inlet end will cause the septic tank to 'back-up' to the house. A blockage at the outlet will cause the reed bed to overflow and the gravel bed to flood.
Refurbishing reed beds is VERY expensive and includes the removal and replacement of both the reeds and the gravel bed. The gravel beds clog up naturally over 7 to 10 years - contrary to the expected life of 30 years or more, when they were first invented
The replacement of the reeds and gravel bed is a very expensive and disruptive operation.
Re-evaluating of the suitability of reed beds during cold winters : trickling filters are a better alternative
The possibility of reed beds freezing solid during cold winter periods is a reality. Many did this in 2010 and forced people from their homes. Some companies involved in the design and building of reed beds have stopped recommending them as a result.
FilterPod sewage treatment plants function as the reed bed part of the system. Initially the raw sewage enters a primary tank which provides separation and breakdown of organic solids (Primary Treatment) the same as the septic tank in a reed bed system. The sewage then passes through a Drain-X bristle filter before discharging into the treatment unit. This uses an aerobic digestion process (Secondary Treatment) and filtration process (Tertiary Treatment).
The reed beds acknowledged advantages exist here too (non-electric, green, sustainable and naturally aerated); the main difference is the containment of the filter media in a tank. The filter is hermetically “separated” from the environment. The sewage water is treated “vertically” by the media in the tank instead of “horizontally” by the gravel bed which requires a larger surface area. Numerous benefits result from this method of containing the filter media, such as the reduction in space required and easier effluent sampling when checking the quality of the treated water.
As the FilterPod is underground, insulated by the ground and the water entering from the septic tank is never below about 10 degrees C, there is no chance of the unit freezing. It was tested for it's EN12566-6 Certificate through a full Northern Germany winter.
The media, like the gravel beds, will also clog over time (don't believe rival companies which claim that it doesn't - it does as you cannot defy the Laws of Physics), but the FilterPod media only costs £250 for FULL media replacement every 10 years.
If the FilterPod units are installed in parallel they can cater for large scale installations, offering a real alternative to large-scale reed beds with none of the problems.
FilterPod Costs
A FilterPod treatment system cost a fraction of an equivalent reed bed system. Reed beds are not a cheap or easy option for sewage treatment. They are smelly, labour intensive and costly to maintain. They provide a breeding ground for mosquitos and as such, encourage small mammals that live in the larvae, rats, grass snakes and mice. They are also costly to install and have a large footprint, taking up a lot of land area. Tha FilterPod is only 1.2M diameter in comparison.