3 Stage Flocculation Tank
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- Manufactured from PP
- Double wier and mixer bridges
Enduramaxx 3 Stage Flocculation Tank with double wiers and mixer bridges available in 3 sizes from 1m3 to 4m3 sizes.
What is the definition of flocculation?
In simple terms, flocculation is the process by which individual solid particles in liquid clot together into bigger particles known as ‘clots’ or ‘flocs’ which can then be separated off to leave a cleaner and clearer liquid behind.
What is flocculation used for?
Conventional coagulation, flocculation or sedimentation practices are essential pre-treatments in a 3 Stage Flocculation Tank for a range of water purification systems. Flocculent chemicals are used in water treatment processes for removal of unwanted solids and contamination to produce cleaner, safer and potentially drinkable water. Other applications include sewage treatment, cheese production, and brewing. It is also used in surface and physical chemistry, biology, and civil engineering.
What are the processes in flocculation in 3 Stage Flocculation Tank?
Flocculation, or sometimes referred to as clarification, consists of four distinctive processes – coagulation, flash mixing, flocculation, and clarification. Sufficient time and velocity are necessary to maximise the effectiveness of the flocculent so that the individual parts come together.
- Step 1. Adding the Flocculent
During the coagulation process, chemical coagulants, also known as flocculants, are added to the water to destabilise the smaller individual particles and cause them to begin aggregating.
- Step 2. Flash Mixing
After the flocculent is introduced, the water is mixed vigorously by the flash mixer so that the chemicals are evenly dispersed throughout the water. This particular step plays a large role in the effectiveness of water treatment. So that the chemicals are evenly distributed it is flash mixed from 30-60 seconds. Coagulation actually begins during the flash mixing process as the coagulants neutralise the electrical charge of the fine particles. This stops the repulsion of the individual particles and allows them to begin sticking together to form bigger ‘flocs’.
- Step 3. Flocculation
After the initial more aggressive mixing, flocculation begins after slowing down the mixing so that the smaller particles produced during the coagulation start adhering together. The flocculation stage usually goes continues for around 30-45 minutes in a flocculation tank that may have several compartments. Each of these compartments has a different mixing speed, and the speed decreases as the water flows from the top of the basin to its bottom. This approach allows the growing flocs to form without being shattered by the mixing blades.
After the flocculation process, most of the particles should have bonded together, which is called the Floc. Floc consists of larger masses of particulates bonded together in clusters of about 0.1 to 3 mm in size. It is critical that the floc is not too small otherwise, it doesn’t settle well enough or too big otherwise, it will likely break apart in the flocculation tank.
- Step 4. Clarification
Clarification is the last of the steps in the flocculation process. Clarifiers typically consist of polyethene cone tanks which hold the water long enough to allow the floc and other particulates to move to the bottom of the tank. The clarification process makes the water clear by removing all kinds of particles, sediments, oil, natural organic matter and colour.
Coagulation and Flocculation
Groundwater and surface water contain both dissolved and suspended particles. Coagulation and flocculation are used to separate the portion of the suspended solids from the water. Suspended particles vary in source, charge, particle size, shape, and density. Correct application
of coagulation and flocculation depends upon these factors. Suspended solids in water have a negative charge and since they have the same type of surface charge, they repel each other when they come close together. Therefore, suspended solids will remain in suspension and will not clump together and settle out of the water, unless proper coagulation and flocculation is used. Coagulation and flocculation occur in successive steps, allowing particle collision and growth of floc. This is then followed by sedimentation (see Sedimentation Chapter). If coagulation is incomplete, the flocculation step will be unsuccessful, and if flocculation is incomplete,
sedimentation will be unsuccessful.
Coagulant chemicals with charges opposite those of the suspended solids are added to the water to neutralise the negative charges on non-settlable solids (such as clay and colour-producing organic substances).
Once the charge is neutralised, the small suspended particles are capable of sticking together. These slightly larger particles are called microflocs, and are not visible to the naked eye. The water surrounding the newly formed microflocs should be clear. If not, coagulation and some of the particle’s charge have not been neutralised. More coagulant chemicals may need to be added. A high-energy, rapid-mix to properly disperse coagulant and promote particle collisions is needed to achieve good coagulation. Over-mixing does not affect coagulation, but insufficient mixing will leave this step incomplete. Contact time in the rapid-mix chamber is typically 1 to 3
1m3, 1.5m3, 2m3, 4m3