If living off the main grid of household services, the method of sewage disposal is an important consideration. If access to mains sewage isn’t possible there are only really three viable options.
These options are:
Cesspools are usually installed as a last resort when there is no option but to store all the waste produced, as there is no suitable method of discharging the effluent by connecting into a land drain (or discharging to a watercourse as in the case of a sewage treatment plant). Cesspools require frequent emptying and need to be checked regularly to ensure they do not overflow. Cesspools are sized upon occupancy, allowing a minimum capacity of 18,000 litres per 2 users and then another 6,800 litres per extra person.
2. Septic Tanks
Septic tanks are the most common type of sewage disposal and consist of a below ground tank which is generally constructed of GRP or Polyethylene (although older installations were brick built with a concrete cover slab). The most popular septic tank is the “Onion Shape”, however there are now also “Shallow Dig” versions which are used where it is difficult to excavate a deep excavation for example rocky ground. The septic tank works by waste entering the tank, the solids sink to the bottom and the naturally occurring bacteria start to break down the solids into sludge and the liquid on top drains off into a drainage field. The tank should be emptied / desludged annually by a licensed contractor. Septic tanks are not allowed to discharge into a watercourse.
3. Sewage Treatment Plants
Sewage Treatment Plants facilitate the growth of bacteria beyond that of a septic tank as they have a secondary treatment process. The secondary chamber artificially introduces air into the waste via a pump (which requires an electrical supply). The aerobic bacteria then breaks down the waste more effectively and this treatment results in a higher quality effluent being produced. The discharge from a treatment plant can usually be directly discharged into a watercourse, subject to a “consent to discharge” permission being granted by The Environment Agency in England and Wales or SEPA in Scotland. If ground conditions allow and there is no watercourse available, sewage treatment plants can also discharge to a drainage field. When choosing or specifying a Sewage Treatment Plant ensure that it complies with British Standard BS EN 12566. The level of the waste treatment can vary between manufactures with some plants producing a cleaner effluent than others.
In January 2015, new rules were introduced that simplify the way septic tanks and small sewage treatment plants are regulated in England, protecting the environment and improving water quality. If you choose to have a septic tank or small sewage treatment plant, by law you must comply with the “general binding rules” by ensuring your system is maintained properly and does not cause pollution. Extra protection is in place in areas designated as environmentally sensitive, where people may need to apply for a permit. It is easy to comply with the general binding rules, here are the main things you need to do:
- Have your system emptied by a registered waste carrier regularly (at least once a year unless the manufacturer says otherwise) to ensure it doesn’t cause pollution.
- Maintain your system regularly, getting any faults or problems fixed immediately.
- You are limited to discharging a maximum of 2,000 litres of treated sewage per day into the ground or 5,000 litres of treated sewage per day to flowing water. If you discharge more you will need a permit. You can calculate how much your system is discharging at www.gov.uk/small-sewage-rules
- Speak to the Environment Agency before installing a new system as you may need a permit. Speak to your local council to check your system will meet planning requirements and building regulations. Only install equipment which meets British Standard BS EN 12566
- If you sell your property, inform the buyer in writing that it has a septic tank or small sewage treatment plant.
For the full set of rules, please go to www.gov.uk/small-sewage-rules for more information and if you are unable to follow the rules, are worried your system may be causing pollution or want to check if your system needs a permit.
Whichever sewage treatment system you decide on or may already have installed here are some handy tips to ensure your system will help prevent pollution, avoid costly repair bills and minimise your energy consumption:
- Get the sludge emptied regularly by a registered waste carrier
- Get it serviced regularly by an accredited engineer and fix problems straight away
- Regularly check for signs of pollution such as sewage smells, pools of water, sludge, foam, lush weeds or grey fungus growing in your local stream or river. If you spot any of these issues call a specialist for help