Identifying flocculation equipment

[PhilRhodes]

Hi,

Perhaps forum members will indulge a bit of idle curiosity!

I work in the film industry and was recently involved in a shoot at a disused water treatment plant (at the site called Sandford Mill just outside Chelmsford in Essex, in the UK). Much of the equipment was easily identifiable: pumps, pipework, what looked like screw drives for removing sludge from the settling tanks, and hoppers for the flocculating agent. Two settling tanks were still half full of... well, crusty gunk, left after the plant shut down in the early 80s. What's exercised my brain ever since was two large steel drums in square tanks which were unidentifiable to me.

As you can see by the scale of the access ladder, they're pretty large - at least ten or fifteen feet across and probably as deep, in a trapezoidal tank that's twenty-five feet square. Clearly the notched troughs running across the top were to feed water into the tank. There were two of these, each associated with a settling tank.

Can anyone shed any light on what this actually is? Some sort of aerator?

Thanks!

Phil

 

[coloeng]

I believe that inflow is via a pipe that enters from the bottom of the clarifier into the inside of what you are calling the drum. The flow then exits the drum at the bottom, solids will settle to the bottom of the clarifier and the water will then overflow into the weirs. So the weirs don't feed water into the clarifier but take water away from the clarifier.

 

[PhilRhodes]

Aha, thanks! Now I know what it's properly called, it's easier to look up. I'm not totally surprised to find that it's the equivalent of the large circular arrangements with the rotating arms that exist at more modern plants. I didn't notice any rotating mechanism entering from either above or below, although I notice most of the schematics I can google up indicate an agitator of some sort, and that this is the point that the flocculating agent is introduced. Certainly the hoppers (apparently containing alum - white powdery stuff that seems to corrode metal readily?) are directly beneath.

I presume the giant upturned coffee cup is to ensure flow moves gently out at the bottom of the tank, so it has maximum opportunity for solids to settle out on the way up?



P

 

[bimr]

I agree with coloeng. This looks like a solids contact clarifier. The drum is a mixing chamber where the incoming water is mixed with water that is internally recirculated inside the clarifier. The mixing action improves the efficiency.

 

[PhilRhodes]

Thanks folks. It was a great place to explore, although I'm not entirely sure I haven't been exposed to the sort of chemicals that made the Joker in Batman.

 

[bimr]

Don't be too worried about the chemicals. For example, alum is used in many products such as deodorant.

If you google "solids contact clarifier", you can see examples of this type of clarifier.

http://www.google.com/imgres?sa=X&biw=1280&bih=558&tbm=isch&tbnid=wq9GWtfaVOQGyM:&imgrefurl=http://

http://www.directindustry.com/prod/...cMB4&iact=rc&dur=1808&page=3&start=20&ndsp=16