These calculations are based on a spherical particle with a specific gravity of 2. Since Stokes law assumes that the particle is settling freely, it is reasonable to expect that in conditions such as those typical to aggregate production, some particle-to-particle interference, or hindered settling, will occur, further slowing down the settling rate.
Continuous coagulation-flocculation in mixed tanks Continuous coagulation-flocculation in a pipe flocculator Method and installation description Coagulation and flocculation are often used in combination. In some cases, the use of a coagulant or flocculant is sufficient to form settleable and floating floccules.
The aim of coagulation is to destabilise a colloidal solution, so that polluting matter can bunch together to form floccules. Colloidal or suspended particles have a negative load and are stable in water: The addition of a coagulant will reduce stabilise the repellence between the colloidal particles.
A coagulant will be added in a fully mixed tank with a short retention time a few minutes and high turbulence or in a pipe flocculator see figure.
The resulting floccules are small and can only grow when calmly stirred, which will allow particles to further cluster together. Flocculants Coagulation and flocculation flaking products can be added to aid this process.
They are added in the pipe flocculator or in a fully mixed tank with a longer retention time minutes and low turbulence to not destroy the floccules. Flocculants are high-molecular substances polymers with various functional groups.
They can then be easier separated via flotation or sedimentation. Because the particles do not all have the same load, the polymer structure requires various load groups.
Anionic, cationic and non-ionic polymers are available. Correct binding between the polymer and the particles is very important for effective flocculation. This means that, besides the type of load, the distribution of the load across the molecule is also important, as is the length of the polymer.
The implementation of these elements results in a few hundred different polymers, each with a specific area of effectiveness. In a number of cases, it may be sufficient to only add a flocculant in order to realise effective separation. Normally, a combination of coagulant and flocculant will be needed.
The floccules are then collected in a follow-up treatment and form a quantity of polluted sludge that needs to be further treated reduced, disposed of, incinerated, etc.
Limited investment is required for these tanks and dosage units. However, a major disadvantage of this technique are the operational costs. In some cases, considerable quantities of coagulant and flocculant are needed to achieve the required level of flocculation.
A certain quantity of physico-chemical sludge is also formed, which is normally processed externally. These costs can escalate, particularly with large volumes of wastewater.
The correct dosage of chemicals is also very important for the process to work correctly. This is not straightforward with wastewater with a widely varying composition. Effective buffering of wastewater offers a good solution in this case. Here are a few typical applications, though not a comprehensive overview.
Wastewater treatment in the textile sector. Pre-purification of wastewater in the food sector, in meat processing, for example, slaughterhouses, sugar refineries, oils and fats.
Treatment of degreasing baths or purification of rinse water in surface treatment and the car industry. Pre-purification of wastewater that is released in barrel cleaning or tank cleaning. The purpose of this is to restrict the use of chemicals and variations in concentrations.
In many cases, pH correction is also needed prior to coagulation. It is essential to select the correct chemicals and dosage to remove a particular pollutant.
This means the effectiveness of various coagulants and flocculants must be evaluated at laboratory scale, at pilot scale or in practice. Effectiveness The technique can be implemented for the removal of various components.
The effectiveness is greatly determined by a large number of factors in the wastewater. The reduction of COD, P and metals is determined by the application.Even after coagulation and flocculation, sedimentation does not remove enough suspended impurities from water to make it crystal clear.
The remaining nonsettling floc causes noticeable turbidity in the water and can shield microbes from disinfection. Filtration is a physical process that removes. Flocculation: Collision and aggregation of the destabilized particles into large flocs (transport step).
* Often, Coagulation and flocculation are used interchangeably. Coagulation and flocculation helps to remove suspended particles or emulsified oils from water. When combined with other technologies, it can produce exceptional water quality with minimal maintenance and successfully treat a broad range of waste streams.
Drinking Water Coagulation and Flocculation Raw water as it enters the treatment plant contains suspended particles made up of organic and inorganic material. The primary method to remove suspended solids is through a process called coagulation.
Flocculation is similar to coagulation in that both refer to smaller particles clumping together to form larger particles. However, in flocculation the clumping stops before it becomes a continuous flocculation and sedimentation to remove the colloidal particles in the water.
The. In water treatment, coagulation and flocculation are treatments that aim to optimize the removal of suspended particles by decantation and filtration processes.