Many natural and manmade substances will cause foam when water is agitated. The major cause of foaming is surfactants, which are synthetic organic chemicals used as the principal ingredient in modern detergents. Foaming is an undesirable property of drinking water because foaming agents may impart an unpleasant taste, cause frothing, and usually can be associated with contamination of groundwater.

Surfactants are the foaming agents which are measured to determine if drinking water has an acceptable Foamability. The MCL* of 0.5 mg/l is based on levels of foaming agents that would prevent the occurrence of visible foam.

Although foam itself is not generally hazardous, other possible hazardous materials may be present along with the foam. Water with high foamability should be analyzed to determine what treatment may be required and to help determine the origin of contamination.

Foaming substances can be removed by conventional treatment consisting of coagulation/flocculation, sedimentation, and filtration, or by activated carbon.