Sewage poured into the sea for nearly nine hours after a failure at a Southern Water treatment plant.

The company apologised for the release which started at 10.35am on Wednesday from its Portobello outfall 2.5km off Peacehaven.

There was another 12-hour release yesterday which Southern Water said was due to the technical failure and heavy rainfall. The company said it was "heavily diluted due to the rain".

The company said engineers are working "very hard to resolve the failure".

It comes just over a month after another failure around Southwick and Worthing where swimmers were advised to not go in the water due to raw sewage being released.

An email sent to local authorities seen by The Argus confirmed there had been a “technical failure” at Peacehaven Wastewater Treatment Works which caused an “unpermitted storm overflow release”. Southern Water confirmed the release.

The email said: “We’re sorry this has happened and we are doing everything we can to resolve the issues at Peacehaven. The failure is caused by the primary treatment tanks (known as lamellas) not working as they should do, which means the site is struggling to treat the usual amount of flows.

“We are taking samples and modelling the impact of the release which started at 10.35am today. We will provide these details to the Environment Agency.

“Details of the release can be found on Beachbuoy and we will provide further updates should it have a detrimental impact on bathing water in the area.”

Southern Water’s Beachbuoy, a publicly available website where people can monitor sewage issues, said there were releases from 10.35am to 7.17pm on Wednesday. It said bathing water was not affected.

The Argus revealed bathing water quality at all the beaches in Sussex last month.

The Argus: Inside Southern Water's Peacehaven treatment plantInside Southern Water's Peacehaven treatment plant (Image: The Argus)

The beaches nearest to the Portobello outfall were all rated "excellent" for bathing water quality. These were Kemp Town, Saltdean and Seaford. 

The Argus was invited to the Peacehaven treatment works in July last year.

“It’s people’s imagination that we are just discharging poo straight into the sea,” Southern Water employee Daniel Rayner-Grey told us during the visit. 

“We don’t want to put anything at all in the sea, but we will hold up our hands when we get it wrong.”

Sussex uses a combined sewer network, meaning that sewage and rainwater use the same sewer network to get to the treatment plant.