Most industrial facilities generate numerous streams of wastewater. Generally, they are all co-mingled in trenches, sumps, or equalization tanks.
Often, several of the wastewater sources are very mildly contaminated. They may be so mild that they could discharge into the sewer either untreated or with a simple treatment like running through an oil/water separator or a bag filter. However, even though most of the waste sources are mild, a few may contain difficult to treat contaminants. This could come in the form of dissolved metals, chlorides or other problematic contaminants. When all these streams are co-mingled, often the problematic contaminates are so strong that it becomes difficult and expensive to treat the entire waste stream.