Wastewater Explosion in UK

[dik]

From CTV News:

LONDON -- Four people died following an explosion in a silo that holds treated biosolids at a wastewater treatment plant near the southwest England city of Bristol, police said Thursday.

Three Wessex Water employees and one contractor died in the incident, which is not being treated as terror-related, Avon and Somerset Police Chief Inspector Mark Runacres said at a media briefing. A fifth person was injured during the explosion at the plant in the industrial area of Avonmouth, but the injuries are not considered life-threatening, Runacres said.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Alistair_Heaton]

was just reading about it.

https://www.bbc.com/news/uk-england-bristol-55173667

 

[itsmoked]

Betting someone may have forgotten or ignored the high methane hazard that lurks around that stuff.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[FacEngrPE]

Picture of the tank here.

https://inews.co.uk/news/uk/avonmouth-explosion-chemical-tank-blast-bristol-four-workers-dead-782549

The tank appears to have been built with a frangable top - the top came loose from the shell, and the shell did not split, so the blast was directed mostly upward.
Accidents involving confined spaces and sewage / sewage products are way too frequent and often tragic like this one.

 

[dik]

oh, sh*t!

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[JohnRBaker]

The tank appears to have been built with a frangable top - the top came loose from the shell, and the shell did not split, so the blast was directed mostly upward.

So discounting what led up to the explosion, once it did explode, everything seemed to work as it was designed to, eh?

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Alistair_Heaton]

looks like our old friend ammonia nitrate was involved again. Along with some lime.

Trying to make fertiliser.

 

[JStephen]

I would say judging from the amount of damage that it was not anything like an ammonium nitrate explosion unless it was a very small amount, more likely methane.
Way back when, an asphalt tank exploded with similar results- roof plate flipped like a flapjack and landed on the tank. The difference was that nobody was on it or close enough to be injured.
I have heard of similar explosions when workers were welding on a municipal water tank- due to getting methane in with the well water and not realizing the hazard.

 

[Alistair_Heaton]

They mix it in with the sludge then throw some lime in. To much lime and it starts heat exothermically and makes the methane off gas.... Spark or hot exhaust nearby and bang.

Seen it happen on a farm with pig poo.

 

[Alistair_Heaton]

Being reported now that it was 3 old boys near retirement with a 16 year old apprentice that were killed.

 

[MJCronin]

Another, more detailed picture of the exploded tank here:

https://www.mirror.co.uk/news/uk-news/avonmouth-explosion-victim-thrown-150-23114784

Looks like the tank/silo is a robust assembly constructed of bolted panels, such as would follow the US Standard AWWA D103.

I do not believe that the tank designers or any D103 tank can be designed specifically with a frangible roof. Stubby bolted panel tanks are naturally robust, not subject to a lot of membrane stresses and the only joint that will usually fail is the shell to roof joint..

Again, .... only my opinion

Probably a cigarette lit up by one of the deceased set off the explosion ..... Here in the US, it is usually maintenance welding that blows up our tanks

Was there a HAZOP (or the UK equivalent) that evaluated the hazards and explosive areas of this facility ?

Methane generation in waste water tanks is nothing new ...

MJCronin
Sr. Process Engineer

 

[Alistair_Heaton]

I think its actually a mixing pot with a rotator mixing mechanism.

I am starting to think they might be dealing with powder.

 

[Hoxton]

MJCronin

The water industry in the UK is pretty hot on health and safety and good design practice. They used to be nationalised (state owned) but were privatised in 1989.

They still have common standards (WIMES) for electrical and mechanical systems:

http://www.pumpcenter.com

Could not find any design guides, but I found the attached Health and Safety guide on our HSE website, which recognises the danger of dust in the plant which dries the sludge - which seems to be where the explosion occurred.

This refers to our hazardous area legislation ie DSEAR and ATEX etc.

One would anticipate that a HAZOP would be part of the design process.

We used to put generation plant in sewage works running on digester gas. Getting prequalified as a contractor is a major task, and if you didn't get your risk assessments submitted and approved before going to site, they did not let you on, even large capable contactors fall foul of this.

Too early to speculate on the cause, we will probably find out mid next year. One of those who died was 16...