# Foams in Wastewater Treatment Plants: From Causes to Control Methods
## 6 Discussion and Future Outlooks  
The discomfort generated by foaming in the WWTPs represents a very common problem, but to date, it is treated mainly only at the management level and still too little studied through a globallyshared scientific method. In fact, years of research have not been able to completely clarify the key processes underlying this phenomenon. The complexity of the issue, combined with inaccurate measurement methods, inaccurate definitions of terms and confusion of phenomena have led to numerous partially contradictory descriptions and hypotheses [16]. To date, the most used procedure for assessing foaming in wastewater treatments is the air method, used above all to define the foaming potential and foam stability. As stated by [PERSON] and [PERSON] [62], the principal advantage of the air method is that it is relatively easy to carry out and produces comparative results in a short period of time. However, FP indices give only information on how much foams are produced in terms of height or volume but not on consistency and stability of foams. Therefore, FPs indices should not be used individually but integrate with other values to better define the tendency for foaming of wastewaters. It is not easy to obtain a complete, exhaustive and subjective characterization of a foaming phenomenon. Firstly, apply a method for the evaluation of the foaming potential that allows obtaining careful and constant results on equal conditions is necessary. However, this is not enough. Other tests must be used to further deepen the assessment, such as the stability of the foams, but not only. The ideal goal is to define a mathematical model based on easily and directly measurable on-site parameters. The variables of the model could be the airflow rate, the aeration time and the initial height of the liquid before aeration: their monitoring is not complicated for the operators in WWTPs. Through the model, significant and simple to interpret data/results should be obtained. For example, the parameter resulting from the model could be the percentage increase in the height of the mixed liquor in the aeration basin following the formation of foams. It is good to avoid subjective procedures with little correlation between the parameters considered and hardly applicable on-site by the operators. It is strongly suggested to develop and validate mathematical models that allow evaluating the real weights of the operative parameters on which the formation of foams depends, as different degrees of dependence on the variables analyzed in the model could result.  
Regarding the foams control mechanism, the mechanical control methods are preferable to overcome the disadvantages associated with antifoam chemical agents. However, mechanical devices alone are generally not totally effective, and their action is enhanced by simultaneously using chemical antifoam agents at the lowest possible concentration. Although foam control systems are widely used, when possible, it is preferable to adopt management interventions preventive of foam formation in the reactor [80]. The goal shared by the scientific community must be to clarify the phenomenon as much as possible in order to identify future research directions: (i) develop a shared protocol for the monitoring of foaming phenomena in WWTPs through evaluation procedures and (ii) indicate promising strategies to prevent or control the formation of foams in WWTPs especially of easy applicability from a management and operative point of view. In fact, to date, there is not a standardized assessment and control method available.