• Gravity Separation
  • Settling – Gravity settling in a large circular tank is often the simplest way to separate solids from liquids. The solids are plowed to the center of the bottom cone of the tank by a rotary rake and pumped away as a slurry.
  • Clarification – If suspended solids must be removed from liquid to a low level, the settler tank can be made larger or chemical treatment can used to modify the interactions of solid particles.
  • Flocculation – When finely divided particles remain suspended in a liquid for hours or days, it is often due to electric charges pushing the particles apart. The charges on the particles can usually be neutralized so that they flocculate or clump together by adding ferric sulfate, aluminum chloride, and/or charged polymers.
• Filtration
  • Lab testing – Testing a process slurry with various filter media under process conditions is an important step in designing a filtration system. Information that can be obtained includes filtration rate, filtrate clarity, cake release from media, cake moisture content, and media blinding.
  • Equipment selection – A huge variety of equipment is available to remove solids from liquids and gases. Selection depends on many factors including:
    • Is the product the filtrate, the solids collected, or both?
    • For batch filtration, should the cycle time be short to reduce equipment size or long to get very clear filtrate by depth filtration?
    • Will the filtrate or filter cake attack common filter media?