Sully residents have lodged complaints with Welsh Water, after a rotten sewage smell has disturbed them in recent weeks.

The odour, which residents compare to rotten eggs, is believed to come from Cog Moors Wastewater treatment plant.

But the smell has reached homes across the village, from Cog Road to Lynmouth Drive and has also been noticed in Dinas Powys and some parts of Barry.

Carol Stingl, a Minehead Avenue resident, told Nub News she had noticed the smell late at night and early in the morning.

"I've noticed it for a couple of months to be honest," she said. "It's a terrible smell; sulphuric like rotten eggs.

"A couple of weeks ago, the windows were just ajar overnight, and the smell actually woke me up. I had to get up and shut them in the middle of the night.

"It has been really strong on occasion, and we're not that near to Cog Moor."

The Cog Moors site treats wastewater for Dinas Powys, Sully, Penarth, Barry and the West of Cardiff. Welsh Water has been investing £50 million to produce clean, green energy by recovering more biomass from the waste.

Hannah Bevan Mohaffel, a Sully resident and admin on the local Facebook group, has been logging residents' reports and informing Welsh Water when the odour flares up.

She said the smell had been noticeable very occasionally in recent years but had become more frequent this month.

"I live at the top of Cog Road, and when I first smelt it, I thought my dogs had an upset stomach," said Hannah.

"It penetrates the house; my living room stank of it. It's actually woken me up in the night if we've had the windows open while we sleep."

Hannah said two nights ago was the worst yet for complaints.

"I thought if one person gathers all these reports for Welsh Water it stops us jamming the phone line. They're under pressure working from home with staff shortages.

"It wasn't that more people reported it two nights ago, but it was the way people described how bad the smell was.

"At times, I've had 30 reports in an hour. The most noticeable thing isn't the number of complaints though, it's how widespread the issue is."

Hannah praised Welsh Water for how responsive it had been in hearing the reports.

Engineers reportedly found on at least two occasions their odour detectors at Cog Moors recorded h2 breaches. Anything registering over 100 is classed as a breach and numbers between 200-300 were recorded.

Engineers also found an overgrown chamber and two badly fitted and damaged manholes linked to the main sewage system which are all leaking odours.

These landowners are now working with Welsh Water to fix this, and odour detectors will be fitted in these areas to enable Welsh Water to monitor them.

"We are carrying out thorough investigations at Cog Moors Wastewater Treatment Works to identify and address the odour issues being reported by residents in Sully," a spokesperson for Welsh Water told Nub News.

"As part of this, we've installed odour monitors at the site to which have identified odour entering the site from our sewer network, but little to no odour from our new Advanced Anaerobic Digestion facility.

"There are multiple sewer feeds into the site and we are now in the process of setting up odour monitoring on each to identify the source of the odour.

"In addition, we have also undertaken some maintenance work to nearby manhole chambers to minimise the risk of them releasing any odour from the network.

"We sincerely apologise for the inconvenience this is causing residents and appreciate their patience whilst our teams look to find the root cause of the odours. We will ensure residents are kept updated on this important issue as investigations progress."