Insights on foaming in surface waters: A review of current understandings and future directions

Foam formation in surface waters represents a multifaceted process governed by intricate interactions among surfactants, gases, liquids, and microbial entities. Despite its global prevalence, the scientific understanding of surface water foaming remains constrained, necessitating a comprehensive exploration. This comprehensive review synthesizes current knowledge and delineates prospective pathways concerning surface water foaming. Significant insights emerge surfactants, are sourced from both anthropogenic and natural origins, making it difficult to assign a relative flux. Wastewater treatment plants confront difficulties in effectively treating complex surfactants, resulting in their discharge into water bodies, exacerbating the foam occurrence. Less developed nations with limited treatment infrastructure release untreated sewage into water bodies. Further, many Natural foams, traditionally perceived as harmless, can harbor toxins under specific conditions, necessitating vigilant monitoring. The stability of foam is intricately tied to filamentous bacteria, natural enzymes, and environmental factors, with seasonality playing a pivotal role. Policy recommendations highlights the importance of parameters such as surface tension (>50 mN/m), hardness (>130 mg/l), and surfactant concentration (<1 mg/l) for formulating effective foam prevention guidelines. For rejuvenation of foaming waterbodies, desilting and preemptive inline treatment/treated water discharge (of dissolved oxygen 3.5 mg/l) are suggested. Future research should prioritize gathering long-term databases on foaming water bodies to predict events and developing standardized analytical techniques. These efforts are crucial for making foam prevention policies.