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*The most commonly encountered toxic heavy metals in wastewater: Arsenic, Lead, Mercury, Cadmium
* Less common: Chromium, Copper, Nickel, Zinc
§ The sources of these heavy metals are: * Industrial, for example;board manufacturing, metal finishing and plating, semiconductor manufacturing, textile dyes
*Street runoffs
* Landfills
§ Ways of minimizing the concentrations of heavy metals :
Pretreatment of industrial effluents,Agreements for industrial effluents with fixed limits for heavy metals, Control samples from effluents.
Removal of heavy metals: Ion exchange, Adsorption Flotation and also Membrane filtration, Electrochemical methods.
Common Heavy metals in wastewater: Lead, Cadmium, Nickel, Iron, Zinc, Arsenic, Mercury
This effluent is basically from electroplating industries. Best and cheapest treatment method is by primary chemical treatment.
1. Mostly pH is acidic. Add10% lime solution. Adjust pH to7.
2. Add Poly Electrolyte (1ppm).
3. Metals get precipitated over a period of30 mins.
4. Seperate out the clear supernatant and remaining is the chemical sludge containing heavy metals at the bottom.
