Assessment of instream foam formation and quantification of foam in effluents

Although the foam formation on surface waters nowadays is not comparable with the foam “mountains” in the 1970s, it still is an issue of water quality concern. A drawback in the discussion is the lack of methods to assess instream foam formation and foam emitted by point sources. Foam formation on a transboundary river in Austria led to an intensive study resulting in two parameters to quantify instream and emitted foam. Foam potential is introduced as emission parameter that is defined as flow rate of river water, which can foam due to an effluent’s discharge. The foam index (FI) represents a parameter to assess the foam on the river and allows a semi-quantitative differentiation between the varying foaming conditions. This publication will present the developed methods and show some results to prove their accuracy and applicability.