Choke bloom refers to a phenomenon that occurs in the primary sedimentation process of wastewater treatment, particularly in activated sludge systems, resulting in reduced efficiency in the removal of organic matter and suspended solids. It is characterized by the excessive growth and accumulation of filamentous bacteria, such as Microthrix parvicella, Nocardia spp., and Chloroflexi-like bacteria, leading to a dense mat or foam formation on the clarifier's surface.
During choke bloom, the filamentous bacteria form long, branching structures that entangle and trap particles, causing them to buoy up instead of settling to the bottom. This mat-like layer reduces the available settling area and hinders the sedimentation of both organic matter and suspended solids. Consequently, the treatment plant's performance is hindered, with increased effluent turbidity and reduced removal rates of pollutants.
Choke bloom is often associated with process disturbances or changes in wastewater composition, such as temperature fluctuations, excessive aeration, nutrient imbalances, and fluctuations in organic loading. It can also occur due to poor process control, inadequate sludge age, or low dissolved oxygen levels. To mitigate choke bloom, wastewater treatment plants may implement various control strategies, including implementing nutrient control measures, adjusting the aeration system, optimizing the sludge age, and promoting competition against the filamentous bacteria through the introduction of specific microorganisms or chemical additives.
Overall, choke bloom represents an unwanted microbial overgrowth that negatively impacts the effectiveness of the primary sedimentation stage in wastewater treatment processes.
