Over the years the rules are constantly changing and upgrading the quality that is to be discharged. In recent years it’s likely you would have a
small sewage treatment plant (also known as a package treatment plant). Most if not all need a electricity supply- a system that treats the liquid so it’s clean enough to go into a river or stream.
The situation is further complicated by the NEW Environment Agency legislation in 2020 imposing stringent laws to require the replacement of faulty cesspools, septic tank discharging to a watercourse. Wet or damp ground, ditches, or streams and rivers will need to be replaced with a Treatment Plant, providing there is no main drain connection within 30 metres from the property. The distance increases when adding properties.
According to the binding rules, if your treatment system was installed before 1983 there was no British Standard in place. You do not need to do anything to meet the British Standard requirement. You must still meet all the other general binding rules.