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Wastewater treatment of lead
Q. Solubility of metal hydroxides graph indicates that the lowest point corresponds to lowest concentration of LEAD in treated water is where we have approximately 5 mgpl of LEAD at roughly 9.2 pH, whereas the statutory requirement is to bring it down to 0.05 ppm. Can you propose some way out like substituting some other chemical in place of Ca(OH)2 to tackle this situation.
KANWAL PRADEEP KAPUR- CHITTORGARH, RAJASTHAN, INDIA
2005
A. Sulfide chemistry will probably do it. Do some bench tests with sodium sulfide, DTC, TMT-15. If they work, you could perhaps add a polishing stage after calcium hydroxide treatment. You may need hands-on assistance rather than an internet posting though :-)
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Ted is available for instant help
or longer-term assistance.
2005
A. Removing lead to < 0.05 mg/L is very difficult, and probably beyond what conventional treatment can achieve on a consistent basis. My experience is that 9.2-9.3 is the best pH, however, there may still be 0.1-0.3 mg/L of soluble lead present at this pH, and much more if there are any suspended solids present.
Most companies faced with this low limit will either use a chemical precipitant such as carbamate in combination with microfiltration, or use selective ion exchange to polish the effluent after conventional treatment.
consultant - Cleveland Heights, Ohio
2005
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