Powder coating waste water treatment of sludge (acid/alkaline reaction)

[PowderCoatEngineer]

I work for a powder coating company and am responsible for the treatment of the waste water that the process creates, I have recently taken over this job after my predecessor retired and although the system they have been using for the last 30yrs works to an extent I can’t help feeling there is a better way to treat the waste water!

The process uses an alkaline cleaner followed by a fresh water rinse then it goes though an acid stage (galvanised products) then a final rinse before a bonding aid is applied,

So the waste water is a mixture of acidic and alkaline and this courses a reaction that results in sludge suspended in the water column. This water now ph neutral is pumped to a settlement tank that has a weir to allow the clean water to leave the tank, currently the ph is keeped as close to 8-9 as possible and chemicals are added to help try and settle the sludge. The chemicals added are rodel ER and calcium chloride and the following ratios in separate tanks then drip feed into the waste water;

Rodel ER 100ml per 100L
Calcium chloride 25kg per 100L

The sludge that settles is then put though a press, collected and taken away for safe disposal.

The Issue is it’s a constant battle to get the sludge to settle, there must be more effective chemicals that will drop the sludge and force it to settle?

We also have a large amount of zink in the waste water but it all gets trapped in the sludge so is removed from the water.

A way to reduce the amount of sludge might also help?

Thanks in advance for your help and I look forward to reading your thoughts.

 

[GeoEnvGuy]

If you want to adjust the chemical add mix you need to conduct a jar test. The amount of calcium chloride seems high but it is cheap. Your predecessor probably completed studies on chemical additives either inhouse lab or outside lab or chemical salesman sample tests.

Also to help settling you can consider centrifuge instead of sludge tanks and belt press. Higher energy but can be higher recovery of sludge.

 

[ashtree]

Can you tell us something about the additive Rodel ER?

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[miningman]

Unless the Rodel is a coagulant, have you looked into adding coagulants??