Welsh Water has stated that the foul sewage smell permeating across the Sully area and beyond poses no health risk to residents.

After weeks of the odour, which locals describe as a rotten egg smell at times strong enough to wake them up at night, Welsh Water has been monitoring the Cog Moor Wastewater treatment plant for Hydrogen Sulphide breaches.

Welsh Water installed intelligent odour loggers at Cog Moors to identify the root cause of the stench. Initial data from these loggers identified elevated levels of odour entering the site from its sewer network.

"We have however identified several defective manhole chambers in the network which were releasing odours, and these have all been rectified this week," said a spokesperson for Welsh Water.

"Further to the health concerns some of the residents have around the dangers of odours and Hydrogen Sulphide (H2S), please find information below which displays the thresholds of symptoms / effects from H2S.

"Please let me give some assurance that the H2S levels recorded directly at our treatment works is 0.015, with surrounding areas likely to be less than this. As such, the odours pose no health risks."

Sully resident Hannah Bevan Mohaffel has continued to log residents' complaints, to provide Welsh Water with a comprehensive report as to when the odour flares up.

"I appreciate your patience, whilst our team look to find the root cause of the odours, and I can assure you that we are actively carrying out thorough investigations to help minimise the disturbance to the local area," said Welsh Water in response to Hannah's efforts.

"I hope the above has given you some comfort knowing that we are taking this matter very seriously. Once we have some data available, I will arrange a meeting to share our findings and next steps."