United Utilities has opted to design a new fat-busting method to clear a 200 tonnes giant grease ball in a Liverpool sewer.

The giant coagulation of fat and grease, and other matter, took up a massive 250 metres of a central Liverpool sewer causing internal flooding at businesses along Bankhall Lane, Birchall Street and Foster Street.

A new fat-busting technique was developed to remove the mammoth fatberg that literally ate it away from the inside out.

Investigations had quickly located the cause of the problem but the fatberg had resisted traditional methods of removal.

Sammy Nelson, United Utilities’ wastewater programme delivery manager and Stuart Ashton, head of technical at Sapphire Utility Solutions, realised they had a battle on their hands and would need to to find another solution.

In the end the inventive engineers combined and adapted two commonly used processes in water and wastewater engineering. First, they drilled a hole through the centre of the fatberg using a clean water technique known as auger boring. Then they fed a steel rope line through the hole where they hung a specially adapted jet machine used to clear sewer blockages.

Using the steel rope they moved the jet machine backwards and forwards inside the fatberg, literally eating it away from the inside out.

After getting rid of the grease ball, a new UV cured chemical resistant structural liner was installed to prolong the life of the sewer and stop flooding issues from occurring in the future.

Sammy Nelson commented:

“Together we came up with the idea of using guided directional drilling equipment to drill through the fatberg and then allow a cable to be run through which would allow jetting to be carried out.

“We then reconfigured a cutting jet to run along the cable through the centre of the fatberg like a ‘Zip Wire’ – this was done to great success and within a couple of weeks flow was restored to the sewer.”

“All this work was carried out in half the time it would have taken to replace the sewer system and at just over a third of the cost not to mention at much less disruption to Liverpool.”