Filtration is often applied to wastestreams where particulate matter could disturb subsequent unit operations. Sometimes, the simple filtration step itself may be sufficient. Filtration equipment in this category would include bag type, depth or fiber wound cartridges, and sand or diatomaceous earth media.
Some membranes are fairly rugged and reusable after cleaning.
Most RO membranes are easily fouled by oil and grease and certain organic materials and can, therefore, be destroyed by continuous exposure to chlorine or other oxidants and organic solvents. Ion exchange resins are expensive and are highly susceptible to degradation by oxidizers or fouling by oil and grease and certain organic materials. Most resins are organically derived synthetics that can be adversely affected by biological activity. Activated carbon is a surface-active adsorption medium that is often used for removal of dilute organic solvents from a wastestream. Activated carbon has also been used for removing low levels of heavy metals, including mercury, from both gaseous and aqueous streams.