Sweep floe process

Colloids present in the water to be clarified, may serve as condensation nuclei for the precipitation process or may become trapped in the precipitate as it settles. For this reason the process is also known as "sweep floe" coagulation. 

The addition and precipitation of multivalent metal salts like alum or ferric chloride can create a dense and readily separable floe that can enmesh and capture particles in a process known as a sweep floe. In addition to physically ensnaring particles, iron and aluminum hydroxide floes also present a large and active siuface area, which is effective in removing certain dissolved chemicals. 

Hgure 10.9 shows a schematic of a wastewater treatment process that is used specifically to treat CMP wastewater. The process is designed and operated primarily to achieve copper removal but also provides a high level of CMP parlicle removal. The lime addition provides a high concentration of divalent cation, Ca, which destabilizes particles and forms a sweep floe that aids particle removal. 

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