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by Derek Peverill, Commercial Manager of Klargester and Titan Pollution Control - leading manufacturers of these products
Tougher building regulations and the need to protect the planet by adopting a more environmentally friendly way of life are having a noticeable effect on the off-mains drainage sector.
Septic tanks, which were once the favoured option for properties unable to access the main sewer by gravity or a pump, are now rapidly being replaced by sewage treatment plants.
While septic tanks merely discharge untreated effluent into the environment, sewage treatment plants provide an environment in which bacteria are cultivated to breakdown sewage. The bacteria survive by using biological matter in the sewage as a food source and the effluent discharged is up to 95 per cent pure.
Since the effluent from a sewage treatment plant is so pure, it may be discharged directly into a river, stream or ditch, with Environment Agency permission. This means that poorly drained soils and areas with a high water table are not a problem, provided there is a suitable watercourse nearby. Discharge into the ground via a soak-away is possible with a sewage treatment plant and will not cause pollution problems.
The quality of effluent from a sewage treatment plant can be further improved by installing a reed bed – a container filled with reeds and gravel. These products are sometimes required as a condition of gaining planning permission in particularly sensitive sites and are suitable for single homes or small domestic developments.
The design of sewage treatment plants has been simplified over the past 20 years, making them easy and cost-effective to maintain.
There are many different sewage treatment plants on the market. However, one of the best ways of ensuring quality is to source products that have been awarded the British Board of Agrément certificate, as this means their design and structure have passed rigorous tests.
It should also be noted that a new European standard has been developed to define the minimum product requirements for small wastewater treatment systems. The standard details a long-term performance test, which will see the key performance indicators of each product clearly stated on the CE (Communauté Européenne) marking label, and allows approved manufacturers to trade across the European Union. Klargester’s BioDisc and Titan Pollution Control’s Biotec have already been tested and certified to these exacting standards.
Size is particularly important when choosing a sewage treatment plant, since no plant will function effectively if it is too small. This issue has been simplified by British Water’s Code of Practice, which aims to promote the collection of accurate and complete information by providing a clear data collection method. One of its key features is a detailed table of loadings for sewage treatment plants.
To ensure best practice, anyone planning to install a private drainage system should liaise with the Environment Agency, (SEPA in Scotland) and their local Building Control department. They should also ensure that a comprehensive site assessment is conducted at the specification stage. This task includes a soil porosity test and a trial hole.
The installer must consider the location of the product in accordance with Building Regulations, particularly Drainage and Waste Disposal H, which came into effect in 2002 in England and Wales. These regulations state that a sewage treatment plant must be sited and constructed in a place where it will not be prejudicial to the health of any person and where it will not contaminate any watercourse, underground water or water supply. There must be adequate access for emptying and maintenance, and the plant must function to a sufficient standard to protect health in the event of a power failure.
Great care must be taken over the final effluent disposal from the site and the drainage field or mound must be located at least 10m from any watercourse or building, unless otherwise agreed by the Environment Agency.
To conclude, sewage treatment plants offer a truly environmentally friendly solution for the off-mains drainage sector and as the desire for a greener style of living continues to increase, these products are likely to entirely replace septic tanks in the future.