Foaming in wastewater treatment plants: deciphering biological foaming and challenges in MBR systems

This comprehensive review details the issues concerning foaming in wastewater treatment plants, focusing on membrane bioreactors (MBRs). Beginning with an introduction, the review explores the causes of foaming, categorizing them into physical, chemical, and biological factors while providing a detailed examination of MBR types and their challenges with biological foaming. The operational issues of foaming in MBR systems are also explained. This review investigates various foaming control strategies, including physical, chemical, and biological approaches, offering insights into their efficacy and practical application. Additionally, it introduces innovative techniques such as magnetic field application and biological controls as potential solutions for managing foaming issues. Furthermore, this study details the cost and energy aspects, comparing wastewater treatment processes with and without foaming and highlighting effective foaming control's economic and environmental significance. This review systematically presents existing knowledge on foaming in wastewater treatment, specifically within MBR systems, and outlines promising future research directions. It is essential to effectively address foaming to optimize wastewater treatment processes, ensure environmental sustainability, and minimize operational costs. According to the literature, the best operating conditions for MBRs to avoid foaming phenomena are a pH value of 6.5 to 8.5, a dissolved oxygen concentration above 2.0 mg/L, and a STR of 3 to 4 days; this duration provides great biomass-settling properties.