Filamentous bacteria are long strands of bacteria growing end to end, resembling strands of hair or spaghetti, which interlock with each other to form a mesh. This “mesh” will help to hold the floc together to form larger pieces for better settling. Filaments are most prevalent in activated sludge systems but are typically found in low concentrations in aerated stabilization basins as well. The types of filamentous bacteria present can indicate certain things about a wastewater system, like nutrient availability or dissolved oxygen concentration. Excessive amounts of filaments can lead to poor settling or bulking sludge, especially in activated sludge systems. In normal amounts, they aid floc formation and help to catch small particles during settling yielding a less turbid effluent. They are also excellent BOD degraders.
The filament characteristics will enable a trained person to identify the type of filament and the root causes that are associated with that particular filament. Once the cause is determined, the plant can make the necessary changes to the system to control the growth rate of that type of filament. Once a filamentous bulking event has been identified, it may be possible to control the filaments temporarily by using remedial methods like chlorination or the addition of hydrogen peroxide. This can be accomplished with minimal damage to the floc in a system if controlled dosages are applied. Note, however, that the filaments will come back if changes to the growth environment are not conducted appropriately. By reducing or removing the causative agent, it will impair the filament’s ability to grow and control them long-term.EBS can help identify the types of filaments present in these systems and the causes for each one.