Sewage Discharge to Watercourse
Discharges to watercourses are only allowed from sewage treatment plants which have an EN12566-3 Performance Certificate. This certificate is obtained after 38 weeks of rigorous testing at an EN Test Centre and costs around £35,000 per plant. It proves that the sewage treatment plant works under all conditions and 'Does what it says on the tin'
At the moment, you do not need to obtain a permit from the EA if the discharge amount is less than 5M³/day, or from 27 people. If you are discharging more than that, then you must apply for a Standard Permit form the EA.
It is no longer legal for new sewage treatment plant installations to discharge into 'Sealed bodies of water'. These are ponds, lakes, etc. which do not have water flowing in and out of them, in other words, they are not connected to ditches or streams.
Discharging to watercourses is always much cheaper than discharging to soakaways, as soakaway construction is very expensive.
Discharge to watercourse should always be your first prefered solution to dispose of sewage treatment plant effluent.