Among many pretreatment and post-treatment methods, rapid filtration (RF), multi-medium filtration (MMF), and precision filtration (PF) are commonly employed with membrane separation process. Rapid filtration usually only uses single or double layers of quartz sand and has a high flow rate. MMF employs multi-layer medium for filtration. It is a common used pretreatment technology to remove dissolved organics. PF uses tens to hundreds layers of high strength filters such as stainless steel filters to achieve high filtration efficiency. Precision filtration is usually employed with membrane separation process.