What Sewage Treatment Options Are There & Which Is Best?
Building regulations dictate that foul drainage must be connected to a public sewer, unless this isn’t possible – in which case, there are various sewage treatment options available. These can be divided into the three broad categories of cesspools, septic tanks and package sewage treatment plants.
These options are suitable for different circumstances and needs – so here are some of the factors that you will need to think about when considering each one.
A cesspool or cesspit actually involves no sewage treatment at all – instead, it is effectively just an underground sewage holding tank with no outlet, only an inlet. Sewage flows into the cesspool, in which it is stored until the tank is full – at which point, it will need to be emptied by a tanker.
Cesspools may be installed on sites where the ground is unsuitable for the waste to simply soak into the ground, as well as specialised sites, such as Sites of Special Scientific Interest (SSSIs) and sites close to drinking water supplies.
Unfortunately, there are certain stringent requirements that apply if you are to be permitted by your local authority to have a cesspool installed – which is possibly just as well, given that it should only, in any case, be considered as a last resort.
It is unlikely that your local council will approve the installation of a cesspool at your property unless it is only intended as a temporary measure while awaiting the imminent construction of a mains drainage system at the site.
Cesspools can also be very expensive to run, with the tanker charges for a family of four potentially exceeding £9,000 a year, to say nothing of how difficult – perhaps even impossible – it can be to sell a property that only has cesspool drainage.
Like cesspools, septic tanks are usually found underground. However, they differ markedly in that they are split into multiple chambers, which enable them to settle the solids out of the sewage, with the septic effluent discharging into a soakaway drainage field.
The primary chamber of a septic tank is where primary treatment – the separation of liquids and solids by gravity – takes place. Sewage flows into the tank, with heavy solids ‘sludge’ sinking to the bottom, while lighter solids, grease and oils or ‘scum’ float to the surface. You can find out more about septic tanks in our previous article.
Again, there are certain conditions that apply to the prospective installation of a septic tank; indeed, they were the traditional means of sewage disposal in rural areas, but are now no longer allowed for more than 60% of UK sites.
A septic tank is also only permitted for a population of up to 15 people according to Environment Agency PPG4 rules, and cannot be installed in Zone 1 of a Groundwater Source Protection Zone at all, with even existing ones needing to be decommissioned.
Septic tanks are therefore by no means the solution to everyone’s wastewater treatment requirements. However, they may be considered for single domestic houses or small developments, and where there is enough porosity in the ground to allow for soakaway.
Package Sewage Treatment Plants
For a more sophisticated alternative to a septic tank, you may consider a sewage treatment plant. There are different types of these available, although they all follow the same general principles.
The key difference between a package sewage treatment plant and a septic tank is that it enables not just primary treatment, but also secondary treatment to take place. These plants work by creating an environment facilitating the growth of bacteria, which in turn, break down sewage into non-polluting end products.
You will require an electricity supply if you opt to have this solution installed, as this will be needed in order to artificially introduce air to the treatment plant. It is the transfer of oxygen through the sewage that enables aerobic bacteria to grow, with this bacteria being more effective at breaking down sewage than the bacteria present in a septic tank.
As a result, higher-quality effluent is produced, which means that – subject to Environment Agency Consent to Discharge – it can be directly discharged to a watercourse.
All of this makes package sewage treatment plants suitable for the majority of sites, ranging from single domestic houses to larger developments and commercial premises.
Which Sewage Treatment Option Is Best?
All sewage treatment options have their drawbacks, whether that be cost, permit restrictions or otherwise. Arguably though, for most the best option for sewage treatment in the absence of mains sewer access is a sewage treatment plant. The greater quality of the runoff produced means that there are fewer restrictions around where you can have one and they can generally service more people. As we’ve already mentioned though, all options have their own limitations or compromises, so it’s worth finding out more about each option before choosing the right option for you.
Get Advice On The Best Sewage Treatment Option For You
Are you still unsure as to which sewage treatment system may be the right choice for your own site? Or perhaps you would simply like to ask for more specialised advice or discuss how we can help with the installation of your sewage treatment plant?
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