Stages Involved in Flocculation Process
- First Stage. The goal of the first stage in this process is to negatively charge the suspended solid materials in the water.
- Second Stage. Once the particles have been neutralized, the second stage begins in which the water has to be agitated through mixers.
- Third Stage. ...
- Fourth Stage. ...
What do flocculants do in water treatment?
- Water treatment plant is a generic term. ...
- Let me illustrate a few major water treatment plants.
- Municipal water treatment plants. ...
- They usually contain large filtration and sedimentation tanks to precipitate suspended and colloidal particles to deodorise and supply a clear colourless water. ...
What happens during the process of flocculation?
Improper coagulation related to coagulant may result from:
- Using old chemicals
- Using the wrong coagulant
- Using the wrong concentration of coagulant. This may result from setting the wrong feed rate on the gravimetric feeder or metering pump or from a malfunction of the equipment.
What is added to water to cause flocculation?
Which coagulant is best?
- Aluminum Sulfate (Alum) – One of the most commonly used water treatment chemicals in the world.
- Aluminum Chloride – A second choice to Alum as it is more expensive, hazardous and corrosive.
- Polyaluminum Chloride (PAC) & Aluminum Chlorohydrate (ACH)
What is difference between flocculation and precipitation?
Types
- Precipitation by Diffusion: A precipitation in a solution that mainly involves Oudin, Oakley Fulthorpe, Radial, and Ouchterlony immunodiffusion.
- Precipitation by Electrophoresis: It includes rocket encounter-immunoelectrophoresis.
- Precipitation in Solution: It involves rings and flocculation tests.
What does flocculation do in water treatment?
Flocculation is a water treatment process where solids form larger clusters, or flocs, to be removed from water. This process can happen spontaneously, or with the help of chemical agents. It is a common method of stormwater treatment, wastewater treatment, and in the purification of drinking water.
What is the purpose of the flocculation process?
As with coagulation, the purpose of flocculation is not to directly reduce turbidity or suspended solids, but to prepare the solids for subsequent removal. Flocculation reduces the number of suspended solids particles as smaller particles combine to form larger ones.
What is the purpose of flocculation during the treatment of drinking water quizlet?
The purpose of coagulation and flocculation is to remove particulate impurities and color from the water being treated.
Where is flocculation used in waste water?
Sydney Water is one of the water authorities in the Australian context that uses flocculation for wastewater treatment. Their specific focus is on removing phosphate in the final stages of treatment. Sydney Water uses sand filters for removing the floc from treated wastewater. They backwash the filters every 24 hours to remove the accumulated floc. Backwash water is returned to the primary treatment section of the plant where the floc is removed with other solids.
What is floculation in water?
Flocculation is a water treatment process where solids form larger clusters, or flocs, to be removed from water. This process can happen spontaneously, or with the help of chemical agents. It is a common method of stormwater treatment, wastewater treatment, and in the purification of drinking water. One of the requirements for treated water leaving ...
What happens when a floc is added to wastewater?
Once floc is beginning to form, a polymer chemical is added to the wastewater. Polymers bridge the flocculant from micro to macro flocculant, meaning that the mass of particles collecting together gets bigger. This chemical also binds the collected mass together so that it does not easily disintegrate even when the water is slightly agitated.
Why is high energy mixing required in wastewater?
The wastewater must be agitated with mixers. High energy mixing is required initially to ensure that the coagulant spreads throughout the water. When flocculation is in progress the mixing energy is reduced to prevent the mass of particles from separating again.
What is the charge of suspended solid particles in wastewater?
Suspended solid particles in wastewater are negatively charged. In the first stage of flocculation, a coagulant like aluminium sulphate is added to the wastewater. The positively charged coagulant molecules neutralize the negatively charged solid particles suspended in the water.
What is Cleanawater wastewater?
Cleanawater is an Australian company that specialises in wastewater treatment equipment and solutions. Our track record and experience over more than 20 years means that we have the expertise to help you solve your wastewater problems. Our technical experts can help you evaluate your application and advise you on the optimum solutions for your needs.
What is Cleanawater's solution?
Cleanawater offers a number of solutions for the wastewater industry to help keep wastewater within specification: Chemical dosing, in particular pH dosing, is a common method of wastewater treatment. Regulations require treated wastewater to be in a neutral pH range when discharged into the environment.
Inorganic flocculants
Inorganic compounds are comprised of molecules that do not contain carbon. These compounds make up some of the most widely used flocculation agents on the market.
Organic flocculants
Organic flocculants include carbon-based molecules and may be biological in nature. The following agents may represent a more efficient alternative to inorganic flocculants in some cases.
What are some examples of coagulation operations?
Coagulation operations can be useful in some cases for the removal of inorganics. Examples of successful applications are copper and mercury reductions from wastewaterplant effluents. Two applications discussed in more detail below are arsenic and fluoride removals in potable water treatment:
Why is coagulation important?
Coagulation is also important in several wastewater treatment operations. A common example is chemical phosphorus removal and another, in overloaded wastewatertreatment plants, is the practice of chemically enhancing primary treatment to reduce suspended solids and organic loads from primary clarifiers.
What is the best coagulant for organics removal?
Organics removal and enhanced coagulation are effective with traditional coagulants like aluminum sulfate, ferric chloride and ferric sulfate, as well as formulations like polyaluminum chloride (PACl) and acid alum. Acid alum formulations are aluminum sulfate with 1 to 15-percent free sulfuric acid.
What are the variables in coagulation?
The efficiency of the coagulation-flocculation process is dependent on many variables. For a particular water these may include: 1 Type of coagulant used 2 Coagulant dosage 3 Final pH 4 Coagulant feed concentration 5 Type and dosage of chemical additives other than primary coagulant (e.g. polymers) 6 Sequence of chemical addition and time lag between dosing points 7 Intensity and duration of mixing at rapid mix stage 8 Type of rapid mix device 9 Velocity gradients applied during flocculation stage 10 Flocculator retention time 11 Type of stirring device used 12 Flocculator geometry.
How to remove arsenic from water?
These include adsorption on granular iron based media; adsorption on ion exchange resins;adsorption on activated alumina; coprecipitation in iron removal plants; coagulation with alum or ferric followed by conventional filtration; and coagulation with ferric followed by membrane filtration. Some studies have shown that the removal of arsenic by coagulation is more economical than other treatment alternatives.
When was alum used in water?
As early as 2000 BC the Egyptians used almonds smeared around vessels to clarify river water. The use of alum as a coagulant by the Romans was mentioned in around 77 AD. By 1757, alum was being used for coagulation in municipal water treatment in England.
What is the charge carried by oocysts?
The negative charge carried by the oocysts is believed to arise from carboxylic acid groups in surface proteins. Removal of Cryptosporidium using alum coagulation appears to be by a sweep floc mechanism. Zeta potential measurements suggest that removal does not appear to be by a charge neutralization mechanism at lower DOC concentrations. At higher DOC, it appears that the mechanism is mediated by a NOM-assisted bridging between aluminum hydroxide and oocyst particles.
What is flocculation?
Flocculation is the separation of a solution, commonly the removal of sediment from a fluid. The term is derived from floc, which means flakes of material; and when a solution has been flocculated, the sediment has formed into larger aggregated flakes, making them easier to see and remove. This process occurs naturally, or it can also be forced using flocculants and/or physical processes.
What are the differences between flocculants and coagulants?
While both coagulation and flocculation are both common processes used in the treatment and purification of water , they are in fact very different. Coagulation is a chemical process, whereby the chemical properties of the solution are altered to promote coagulation. Coagulate means to curdle, and coagulants initiate the same process that naturally occurs in milk, when the pH of the liquid changes and the milk solids clump together. Coagulants are usually salts, which break down to release positive or negative charges. Flocculation, on the other hand, is a physical process that causes particles to floc together, first forming a cloud and then a precipitate. Flocculants are often polymers, which induce the settling of particles into larger and larger flakes or flocs. Physical agitation or other techniques are often required to promote flocculation, while coagulation will occur as soon as the coagulant has been added to the solution, without any physical processes being required.
Why are organic flocculants used?
Organic polymeric flocculants are most widely used today, due to their ability to promote flocculation with a relatively low dosage. Although, their lack of biodegradability and the associated dispersion of potentially harmful monomers into water supplies is causing the focus to shift to biopolymers, which are more environmentally friendly. The problem with these is they have a shorter shelf-life, and require a higher dosage than organic polymeric flocculants. To combat this, combined solutions are being developed, where synthetic polymers are grafted onto natural polymers, to create tailored flocculants for water treatment that deliver the optimum benefits of both.
How do coagulants work?
Coagulants work by destabilising particles present in a stable solution, causing them to aggregate, and allowing them to be bonded together by flocculants . The flocculants join the particles together into flocs, which are then separated from the solution, once they have either fallen as sediment or floated to the surface.
What is the purpose of coagulation in water?
Water can contain colloidal solids, like clay particles, bacteria, plankton, decaying plant material or other organic matter; and using coagulation and flocculation to purify water has been an active practice since as early as 2000BC, when the ancient Egyptians used almonds smeared around vessels to purify river water.
What is the process of coagulation?
Coagulation is a chemical process, whereby the chemical properties of the solution are altered to promote coagulation. Coagulate means to curdle, and coagulants initiate the same process that naturally occurs in milk, when the pH of the liquid changes and the milk solids clump together.
What is floculant in chemistry?
Flocculants are substances that promote the agglomeration of fine particles present in a solution, creating a floc, which then floats to the surface (flotation) or settles to the bottom (sedimentation). This can then be more easily removed from the liquid.
Why is flocculation so popular?
Coagulation and flocculation processes have become more and more popular due to the increasingly stringent filtration requirements for industrial and municipal water treatment and wastewater treatment facilities levied by the U.S. Environmental Protection Agency (EPA.)
What is a flocculant?
Flocculants are lightweight, medium weight and heavy polymers that cause the destabilized clumps of particles to agglomerate and drop out of the solution, removing them from the filtered water. The weight used depends on the type of particle.
What is coagulation in wastewater treatment?
Coagulation water treatment is the first step in chemical wastewater treatment. Instead of passing over particles that would otherwise slip through the filter and fall too slowly to be trapped as sediment, coagulation clumps them together so they are more easily removed. Most of us know coagulation from anatomy class. It’s what our blood does when it combines with oxygen, thereby making a scab or a blood clot. It’s the same principle with wastewater treatment.
When was coagulation water used?
Yet coagulation water treatment is far from being a new process. In fact, it was in use by the Egyptians as early as 2,000 B.C. Later the Romans used the coagulation process in water treatment, as did the English in the 18th century.
What does alum do to wastewater?
In coagulation treatment, a harmless chemical such as alum causes all of the particles to give off a positive charge and thus clump together, making them easier to filter.
How does a water treatment unit work?
Even though EPA regulates and sets standards for public drinking water, many Americans use a home water treatment unit to: 1 Remove specific contaminants 2 Take extra precautions because a household member has a compromised immune system 3 Improve the taste of drinking water
Why do people use water treatment units?
Even though EPA regulates and sets standards for public drinking water, many Americans use a home water treatment unit to: Remove specific contaminants. Take extra precautions because a household member has a compromised immune system. Improve the taste of drinking water.
What is the process of boiled water?
Distillation is a process in which impure water is boiled and the steam is collected and condensed in a separate container, leaving many of the solid contaminants behind. Disinfection. Disinfection is a physical or chemical process in which pathogenic microorganisms are deactivated or killed.
What are the steps of water treatment?
Today, the most common steps in water treatment used by community water systems (mainly surface water treatment) include: Coagulation and flocculation are often the first steps in water treatment. Chemicals with a positive charge are added to the water.
What is a water softener?
Water Softeners. A water softener is a device that reduces the hardness of the water. A water softener typically uses sodium or potassium ions to replace calcium and magnesium ions, the ions that create “hardness.”. Distillation Systems.
What is the most common type of water treatment system?
The most common types of household water treatment systems consist of: Filtration Systems. A water filter is a device which removes impurities from water by means of a physical barrier, chemical, and/or biological process. Water Softeners. A water softener is a device that reduces the hardness of the water.
Why is chlorine added to water?
After the water has been filtered, a disinfectant (for example, chlorine, chloramine) may be added in order to kill any remaining parasites, bacteria, and viruses, and to protect the water from germs when it is piped to homes and businesses.
What is coagulation and how is it used in water treatment?
Coagulation is the process of adding specific chemicals to untreated water in order to destabilize the particles within the water. In most cases, aluminum sulfate or ferric chloride is added to achieve this. These particles have positive charges that are opposite to the negative charges of suspended particles within the water.
What is flocculation and how is it used in water treatment?
Flocculation is the process of encouraging the formation of flocs, or small clumps, from solids in the water. The water is mixed and activated slowly, allowing movement of particles and micro solid throughout the waste water treatment chamber.
Deploying coagulation and flocculation together in sequence
Where coagulation is found to be lacking — i.e., in creating large macro flocs that can be easily filtered and removed — flocculation can help. In areas where flocculation is inadequate by itself — for example, in targeting the particles that are suspended within the untreated water — coagulation is useful.
Coagulation and Flocculation in Water and Wastewater Treatment
The Coagulants
Removal of Natural Organic Matter
Pathogen Removal
Removal of Inorganics
Wastewater Treatment
Factors Affecting Coagulation Operations
Rapid Mixing
Flocculation
- Orthokinetic flocculation arises from induced velocity gradients in the liquid. It is here that primary particles are induced to approach close enough together, make contact and progressively form larger agglomerates, or flocs. The principal parameter governing the rate of orthokinetic flocculation is the velocity gradient applied. The degree or ex...
Testing and Control