Metal Removal from Process Wastewater

[ChemEng87]

Dear members,

I have been given an assignment to design a process for the following water condition and requirements. I don't have much experience in this field so any help about the overall process and equipment required would be highly appreciated.

Wastewater to be treated includes:

Average TSS: 250 mg/L
Maximum TSS: 500 mg/L
pH: 7.5
Dissolved Copper: 2.5 mg/L
Dissolved Zinc: 3.6 mg/L

Discharge requirement:
TSS: <300 mg/L
Total Copper: <1 mg/L
Total Zinc: <2 mg/L

Assume reduction of TDS is not required in order to meet the discharge requirements.

Thank you in advance for your cooperation.

 

[bimr]

The traditional method to remove soluble metal ions from solution is to precipitate the ion as a metal hydroxide. You will need a clarifier and multimedia filter.

There is no selective method to remove the metals without removal of the TSS.

 

[ChemEng87]

bimr,

Thank you for your response. I was wondering if you could give me a little more details about the process. For example what type of clarifier to be used and what chemicals to be added? Would a lime softener work in this case? Also isn't TSS too high to be handled with a media filter? Based on the research I did, typical TSS level to be handled by media filter is <100ppm. If that is true, can we use IGF/DAF instead of media filter?

Thanks again!

 

[bimr]

It is possible to use lime or sodium hydroxide. It is more cost effective to use lime on larger systems.

A gravity plate settler will provide satisfactory service as a clarifier. The effluent from any type of clarifier should typically be less than 10 mg/L.

Generally, the metal concentration in the effluent is the total of the dissolved metals and the metals contained in the TSS. It is essential to remove all of the TSS to produce a good effluent. For that reason, a multimedia filter is normally used.

 

[jojopari77]

I suggest you do a simple jar test with this.

First you can coagulate the TSS using some coagulant like PAC, and then you just have to give some floculant on it, Let it settle for 10 minutes. Do a quick filtration, using filter papper. And you will see the result.



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http://www.on-water.us

 

[kybhosale]

All heavy metal precipitate above pH value of 10.5.
for pH correction Lime is cost effective but it produces too much of sludge and Caustic will be another option for sludge reduction.

Krunal Bhosale

http://waterengineer.co.in

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