Flash Mixing and Flocculation

Flash Mixing and Flocculation

Flash Mixing and Flocculation in municipal and industrial wastewater treatment is a complex process in which wastewater is treated to be suitable to be released to the sewer.  It goes through several phases of mechanical, physical and chemical nature starting with a physical-chemical process of flash mixing and flocculation.  Flash mixing and flocculation are essential in the treatment of industrial and municipal wastewater which contains colloidal-type suspension materials.  These are particles that are too small or light to be able to settle and be eliminated and to allow sedimentation and agglomeration in larger particles, flash mixing treatments and flocculation are fundamental.

Flash Mixing in Water Treatment

Flash Mixing in Water Treatment, this stage of rapid mixing consists in adding chemicals to raw water to foster coagulation, attracting particles which do not settle.  Attracted by coagulants, such as ferric chloride (FeCl3)PAC (poly aluminium chloride Al2Cl(OH)5), aluminium sulphate (Al2(SO4)3), these particles are then easy to agglomerate during the flocculation stage.

The duration of the flash mixing stage is a key factor and determines the quality of the whole process.  Too short retention time will not ensure a homogeneous distribution of the chemicals within the basin volume, resulting in an unsuccessful reaction, whereas too long retention time will lead to coagulant overdosing preventing the process efficiency.  It is essential to carefully calculate the residence time taking into consideration parameters including the reactor volume and the water flow rate through the vessel.

Vertical agitators are required at this stage as well as during the flocculation stage.  Our vertical agitators are designed to result in an efficient flash mixing phase with a thorough agitation of chemicals in the raw water before the flocculation chamber.  Our high-efficiency impellers with a hydrodynamical profile are perfect to accomplish flash mixing creating a high flow rate while ensuring maximum efficiency.

What is Flocculation in Water Treatment?

Flocculation is the phase that occurs after flash mixing which particles are brought to larger agglomerations called flocs.  This is necessary in order to settle in the sedimentation chamber and be easily filtered. This is the result of a reaction with a polymer solution, which acts as a flocculant agent.   Flocculation agitators need to be engineered carefully to ensure an effective flocculation process.   Minimum time, energy and chemical consumption and high-quality water along with an increased dry content during a result of dewatering.

Flocculation Agitator Design

Flocculation agitator design is critical as flocculation needs an effective and homogeneous mixing to encourage flocs contact.  If the agitation is too vigorous it prevents agglomeration and will start to break the newly formed flocs. It is crucial to maximising the impeller flow rate while minimizing the shear. A variable speed drive is recommended to control the mixing speed during the process so that the process and change the output speed according to the process needs.

For more details on the Enduramaxx mixers, polymer makeup units and vessels please get in touch.

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