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These chemicals are called coagulants, and have a positive charge. The positive charge of the coagulant neutralizes the negative charge of dissolved and suspended particles in the water. When this reaction occurs, the particles bind together, or coagulate (this process is sometimes also called flocculation).
What is coagulation and flocculation in the water treatment process?
Coagulation and flocculation are used to separate the suspended solids portion from the water. Suspended particles vary in source, charge, particle size, shape, and density. Coagulation and flocculation occurs in successive steps, allowing particle collision and growth of floc.
What is the process of coagulation water treatment?
Coagulation is a process used to neutralise charges and form a gelatinous mass to trap (or bridge) particles thus forming a mass large enough to settle or be trapped in the filter.
Why do we use flocculation?
4 Flocculation. Flocculation is a process by which a chemical coagulant added to the water acts to facilitate bonding between particles, creating larger aggregates which are easier to separate. The method is widely used in water treatment plants and can also be applied to sample processing for monitoring applications.
What are the factors affecting coagulation?
Factors. Coagulation is affected by the type of coagulant used, its dose and mass; pH and initial turbidity of the water that is being treated; and properties of the pollutants present. The effectiveness of the coagulation process is also affected by pretreatments like oxidation.
Does alum increase pH?
Ionic species present in alum solutions are highly dependent on the degree of reaction with hydroxyl ions. It is tempting to say that “the composition is pH-dependent.” However, in the vicinity of pH=4.3 the composition of alum solutions changes a great deal with very little change in pH.
Is the first step of sewage treatment?
Treatment Steps
- Step 1: Screening and Pumping. The incoming wastewater passes through screening equipment where objects such as rags, wood fragments, plastics, and grease are removed.
- Step 2: Grit Removal.
- Step 3: Primary Settling.
- Step 4: Aeration / Activated Sludge.
- Step 5: Secondary Settling.
- Step 8: Oxygen Uptake.
- Sludge Treatment.
Which coagulant is used for sewage treatment?
Alum is used in water treatment whereas Ferric Chloride is used in sewage treatment.
What are the side effects of alum?
Side effects of Alum The excessive amount of alum intake may cause breathing difficulty, facial puffiness, pricking sensation & small ulcers on the skin, chest/throat tightness, and burns rarely seen in some cases.
What is the difference between flocculant and coagulant?
Depending on the charge and chemical composition of your wastewater, flocculants can either be used on their own or in combination with coagulants. Flocculants differ from coagulants in that they are often polymers, whereas coagulants are typically salts.
Why alum is used in wastewater treatment?
Iron free Aluminum Sulfate (Alum) is most widely used in municipal drinking water and wastewater treatment systems. In potable water applications, alum functions as an excellent primary coagulant. Through charge neutralization and flocculation in raw water, alum removes: Turbidity.
What are the 4 steps of water treatment?
These include: (1) Collection ; (2) Screening and Straining ; (3) Chemical Addition ; (4) Coagulation and Flocculation ; (5) Sedimentation and Clarification ; (6) Filtration ; (7) Disinfection ; (8) Storage ; (9) and finally Distribution. Let’s examine these steps in more detail.
Why does pH affect coagulation?
Since pH values affect the surface charges and forms of the coagulants and impurities to be removed, controlling the level of pH would significantly improve the coagulation process. Therefore, not only coagulant dosage, but also pH value should be optimized to maximize the removal of impurities present in raw water.
What is the most important step in water treatment?
It is, however, an important primary step in the water treatment process, because coagulation removes many of the particles, such as dissolved organic carbon, that make water difficult to disinfect. Because coagulation removes some of the dissolved substances, less chlorine must be added to disinfect the water.
What is the function of coagulant?
In water treatment, coagulants are used to remove a wide variety of hazardous materials from water, ranging from organic matter and pathogens, to inorganics and toxic materials, like arsenic, chemical phosphorous and fluoride.
Why is alum a good coagulant?
The pH of the water plays an important role when alum is used for coagulation because the solubility of the aluminum species in water is pH dependent. If the pH of the water is between 4 and 5, alum is generally present in the form of positive ions (i.e., Al(OH)2+, Al8(OH)4+, and Al3+).
How does flocculation work in water treatment?
How does flocculation work? Flocculation is based on a chemical process. It involves adding chemicals to the wastewater in sequence and allowing tiny solid particles to collect together in a larger mass called a floc. As a treatment of wastewater, flocculation is carried out in stages.
What is the first step in primary treatment plant?
Primary treatment in sewage treatment involves physical removal of particles (large and small) from the sewage through filtration and sedimentation. Initially floating debris is removed by sequential filtration. Then the grit (soil and small pebbles) are removed by sedimentation.
What is an example of coagulation?
Examples of Coagulation Milk proteins coagulate to thicken the mixture that forms yogurt. Blood platelets coagulate blood to seal a wound. Pectin gels (coagulates) a jam. Gravy coagulates as it cools.
What is the principle of coagulation?
Coagulation and flocculation are related terms describing the process of preparing colloidal materials for removing by sedimentation. Coagulation is the process used to reduce the energy forces present around particles that tend to keep them from joining together to form a larger mass.
What is flocculation wastewater?
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.
Is coagulation reversible?
Coagulation is irreversible, the proteins cannot be turned back into their liquid form.
Is alum a coagulant or flocculant?
To accomplish this, the water is treated with aluminum sulfate, commonly called alum, which serves as a flocculant. Raw water often holds tiny suspended particles that are very difficult for a filter to catch. Alum causes them to clump together so that they can settle out of the water or be easily trapped by a filter.
How coagulation is useful for the treatment of wastewater?
Coagulation is the chemical water treatment process used to remove solids from water, by manipulating electrostatic charges of particles suspended in water. This process introduces small, highly charged molecules into water to destabilize the charges on particles, colloids, or oily materials in suspension.
What is the first step in the water treatment process?
Coagulation and flocculation are often the first steps in water treatment. Chemicals with a positive charge are added to the water. The positive charge of these chemicals neutralizes the negative charge of dirt and other dissolved particles in the water.
