ABSTRACT
Biosolids thickening (or concentration) is a unit process used to increase the solids content of the biosolids by removing a portion of the liquid fraction. In other words, biosolids thickening is all about volume reduction. Increasing the solids content allows more economical treatment of the biosolids. Biosolids thickening processes include the following:
• Gravity thickeners • Flotation thickeners • Solids concentrators
Biosolids thickening calculations are based on the concept that the solids in the primary or secondary biosolids are equal to the solids in the thickened biosolids. The solids are the same (see Figure 10.1). It is primarily water that has been removed to thicken the biosolids and result in a higher percent of solids. In these unthickened biosolids, the solids might represent 1 to 4% of the total pounds of biosolids, but when some of the water is removed those same solids might represent 5 to 7% of the total pounds of biosolids.
