A council's plan to roll out water cremation has been halted after utilities firms raised concerns about the "liquefied remains of the dead going into the water system".

Sandwell Metropolitan Borough Council in the West Midlands had approved the installation of a Resomater water cremation machine, in a move that could pioneer the use of alkaline hydrolysis in the UK. But both Water UK and Severn Trent Water refused its application for a "trade effluent" permit to dispose of dead bodies into the water system, BBC News reported.

"We are not convinced and believe the technology needs to be explored in much greater depth," a source at Water UK told The Telegraph.

"This is an absolute first in the UK. We have serious concerns about the public acceptability of this. It is the liquefied remains of the dead going into the water system. We don't think the public will like the idea."

So what exactly is water cremation, and is it safe?

What is alkaline hydrolysis?

Alkaline Hydrolysis is also known as bio-cremation, resomation, flameless cremation and water cremation. It works by dissolving the remains of a deceased person in an alkaline solution. It is widely regarded as more eco-friendly than burial and cremation - where toxic pollutants are released into the air.

What does it involve?

The body is put inside a pressurised steel vessel filled with 95% water and five percent potassium hydroxide, according to the Funeral Consumers Alliance of Minnesota.

The body is then exposed to temperatures of around 177℃, compared with between 871℃ - 982℃ used during cremation. It is all over in about four hours.

What happens to the body?

Water cremation replicates the physiological processes that occurs naturally in the body after death, according to the Mayo Clinic. So all that remains of a person is a greeny-brown liquid and their bones. These are reduced to a substance similar to granulated sugar, which can be given to a person's loved ones - akin to ashes.

Where is it available?

First patented in the US in 1888, alkaline hydrolysis is available in Australia, while Florida is one of the few US states to use the method for human remains. It will be rolled out in California in 2020 and is already used by institutions including UCLA and the Mayo Clinic in Minnesota. Saskatchewan, Quebec and Ontario in Canada have also legalised the procedure.

Is it safe?

While utilities firms in the UK are sceptical, alkaline hydrolysis is already used to dispose of animals safely and only leaves behind a watery goo. No DNA traces are found in the liquid.

The persisting problem is persuading relatives to reduce their loved ones to a green liquid and send them into the sewers, rather than any legitimate safety issues.