Service Water of Cooling Tower

[doomster]

What are the possible effect when I use a high copper and high arsenic concentration in cooling towers?

This water comes from recycling water rain runoffs. The water have high copper and high arsenic because of copper concentrates and dust from smelting.

 

[springrise]

Hi,
do you have idea what would be the resulting concentrations of Cu and As in the cooling water circuit?
Is the copper and arsenic present mainly in particulate/dissolved form? If it's particulate you should be able to filter them out.

Possible problems in the cooling circuit:
- (if particulate) - deposition of particles in the low flow areas, possibly leading to under-deposit corrosion
- (if dissolved) - galvanic deposition of metal copper on carbon steel or aluminium surfaces leading to galvanic corrosion
- (if dissolved) - precipitation of copper hydroxide leading to deposits and under-deposit corrosion
- new health hazard because of the arsenic (and also copper) being present in the cooling tower aerosols
- change in "legal status" of the cooling water blowdown

 

[doomster]

The copper and arsenic concentration at the outlet of the silting ponds are:
Cu - 34.28 ppm
As - 0.46 ppm
Cd - 0.87 ppm
Pb - 0.40 ppm
Zn - 7.12 ppm

Do you have any reference for that? Any studies, journals, or books that you can recommend?

 

[springrise]

Would this be the only source of water for the cooling system? Or is there another feed water source, that is "clean"? What ratio?
I assume you have a recirculating cooling system, because you mentioned cooling towers.

As for the references, the "underdeposit corrosion" is a common corrosion mechanism in cooling systems. So if your metals are in particulate form, you can expect that to happen.
If the metals are in dissolved form you can still expect them to precipitate, because cooling water has (in most cases) alkaline pH. The alkalinity reacts with the dissolved metals to form hydroxides:

http://www.porexfiltration.com/learning-center/technology/precipitation-microfiltration/

 

[doomster]

It's not totally clean because the water is only treated only with caustic for pH correction.
The water is not yet used for cooling tower, still a proposal. If ever the project will push through then it will be use as a make up water for the cooling tower.

Thank you for your help.

 

[bimr]

I don't believe it will be practical since you will be generating aerosols with metal contaminants. The arsenic, lead, and cadmium will be of particular concern.

To recycle water in a cooling tower in California, you probably need to achieve the title 22 standards. Title 22 of California's Water Recycling Criteria refers to California state guidelines for how treated and recycled water is discharged and used.

The cooling tower will also have a blowdown stream where the contaminants will have been concentrated 6-10 times by the cooling tower cycles. You would then have to treat that blowdown stream as well.