Causes and remedies for filamentous foaming in activated sludge treatment plant

This paper reviews the problem of foaming associated with the activated sludge process and its control using various physical, chemical and biological methods. Activated sludge process is widely used for treatment of every type of wastewater like industrial, domestic and municipal wastewater. This process is driven by a complex microbial population, among which some mycolic acid containing bacteria leads to the stable foam formation which ultimately results in poor efficiency of the plants and leading to major environmental, operational, and health problems. A number of researches provide the evidences of foaming in wastewater treatment plants and its control using physical, chemical and biological methods. Current approaches for controlling foam includes operational adjustments, additional structures, controlling dissolved oxygen levels, water sprays, steam application, polymer addition, chlorination and a novel and ecofriendly approach that is treatment of filamentous bacteria with the specific phages. A detailed study of all methods is presented and collectively described in this review paper for a better understanding of the foam controlling strategies.