All biological wastewater treatment processes depend largely on the solids capture efficiency of their secondary clarifiers. Because solids escaping secondary clarifiers are primarily organic, they contribute to the oxygen demand of receiving waters. They also contain nitrogen and phosphorus, as well as heavy metals and nonbiodegradable toxic organics, which are released into the environment if secondary clarifiers perform poorly. Effluent suspended solids (SS) not captured by secondary clarifiers also can hinder downstream processes such as filtration and disinfection.