The solids or Bio-solids are reused to treat the incoming wastewater. As the bio-solids increase a small portion is removed for "Digestion" and referred to as Sludge. The sludge is digested to further stabilize the organic matter to prevent rapid decomposition which creates odor, pathogenic organisms, and attracts bugs and vermin. Once the sludge is stabilized as much excess water as possible is removed and the sludge "cake" is hauled away to use as fertilizer on crops such as corn, soybean, and wheat.