Why treat industrial wastewater?

The most basic answer is to make dirty water clean. Treatment facilities simply compress the organic decomposition processes which take place in nature. This is performed by a combination of physical, biological, and chemical treatment stages. Nature (receiving waters) can only accept small amounts of sewage before becoming polluted, that is, natural bacteria feed on the sewage organics and create an abnormal amount of dissolved oxygen uptake. Dissolved oxygen which exists in minute amounts (10 parts per million @ 20oC), is required by all marine life for survival. One of the principle objectives of wastewater treatment is to prevent as much of this "oxygen-demanding" organic material as possible from entering the receiving water.

Metal Plating Waste Regulatory Requirements

Untreated metal plating waste is generally considered a hazardous material, and as a result it is under federal jurisdiction. When the material is solidified using cement and concrete materials, the waste becomes stabilized, but in some cases it may still be subject to federal restrictions.

A process for removing heavy metal ions or cyanide ions from a waste water stream originating in a metal plating plant or a mine comprising the steps of pretreatment in which the waste water stream is first pretreated by removing particulates, fats and oils; filtration by means of a first sand filter to remove suspended particulates down to 50 microns, a second bag filter to remove suspended particulates down to 3.5 microns, a third micro filter to remove particulates down to 0.1 microns in size and a fourth ultrafilter to remove particulate down to a molecular weight of 10,000; concentration of the heavy metal ions in the waste water stream by means of a first stage nanofiltration unit and second stage nanofiltration unit or reverse osmosis membrane unit down to a molecular weight of about 200 with nanofiltration and less by reverse osmosis; increase the concentration of heavy metal species in the waste water stream to above 700 ppm; electrodialysis to further increase the concentration of heavy metal ions in the waste water stream to approximately 6000 ppm; electrolysis to remove heavy metal ions. Alternatively, ion exchange columns can be used to remove the heavy metal ions after the filtration and concentration in the nanofiltration membranes.

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