Evaluation of foaming potential for water treatment: limits and developments

The critical issue generated by foaming in wastewater treatment plants (WWTPs) is a problem that is currently very common and shared, but which to date is treated mainly only at the management level. In this work, an experimental study with foam tests on real and synthetic waters was conducted using a laboratory scale plant and foaming power indices were calculated. To date, the estimation of foaming potential is mainly based on these indices which give information only on height/volume of foams but not on the type of foams, in terms of consistency and therefore stability. Tests showed that foaming power indices were highly variable with the same water: it was not possible to identify a single foaming potential value for each water. Two models were proposed to estimate the percentage increase in height of chemical foams produced following the introduction of air below the surface of a liquid. In terms of determination coefficient, the results obtained from the complex model were better: R2 was 0.82 for the simple linear model and 0.90 for the complex one. This approach has allowed to underline some critical aspects of foaming potential as it is determined today and the possible improvements applicable for a more objective evaluation.