Coagulation and Flocculation in Water and Wastewater Treatment

Treatment of surface wastewater is aimed at returning contaminated water to a previous state for home use or for other purposes. Some sources of wastewater include industrial wastewater from manufacturing, agricultural wastewater, agricultural industry, and household wastewater from sinks, bathtubs, toilets and the like. Particles from water of various sources include bacteria, organic matter, sand, etc. which cause unpleasant odors due to turbid water or appearance discoloration.

Wastewater treatment chemicals mainly include coagulant and coagulant. The coagulant is essentially used to substantially precipitate suspended solids in water and the flocculant causes secondary sedimentation of the particles. Alum (iron / nonferrous), ferrous sulfate, ferric chloride, and PAC (polyaluminum chloride) are mainly used as coagulant. Aggregation is accomplished using polyelectrolytes such as polyacrylamide (anionic, cationic and nonionic), polyamine, poly DADMAC and the like. Flocculants for clarification of medicinal products and biotechnology waste, flotation and sludge dehydration

There are many discussions and confusion about the use of coagulation and condensation terms in the literature. In water purification plants, there is usually a high-energy high-speed mixing unit process (residence time is seconds) adding coagulant to add coalescing tank (residence time 15 to 45 minutes). The inputs are converted into large paddles or other gentle mixing equipment to promote coalescence. In fact, once a metal salt coagulant has been added, a coagulation and flocculation process is in progress. : 74-5

The wastewater to be treated may contain high concentrations of fertilizer (farm pond water) and heavy metals (mine tail ore pond). Important treatment methods include 1) coagulation, coagulation and precipitation 2) particulate activated carbon filtration 3) ozone treatment. 1) Most of the various pollutants such as heavy metals and organic matter (fertilizer) can be removed. 2) Partially treated water can be further polished by adsorbing large organic matter. 3) It helps to decompose high molecular weight organic matter and to some extent sterilization