Table of Contents
Water treatment coagulants are comprised of positively charged molecules that, when added to the water and mixed, accomplish this charge neutralization. Inorganic, organic, or a combination of both coagulant types are typically used to treat water for suspended solids removal.
Why are coagulants used in water treatment?
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.
What are some of the coagulants used in water treatment?
Aluminum and iron salts are the most commonly used inorganic coagulants in the wastewater treatment settings. These include based aluminum metals (aluminum chloride, aluminum sulfate, sodium aluminate) and iron based metals (ferrous sulfate, ferric sulfate, ferric chloride) [13, 17, 18].
What is the purpose of coagulation?
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.
What are the common coagulants?
The commonly used metal coagulants fall into two general categories: those based on aluminum and those based on iron. The aluminum coagulants include aluminum sulfate, aluminum chloride and sodium aluminate. The iron coagulants include ferric sulfate, ferrous sulfate, ferric chloride and ferric chloride sulfate.
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.
Is alum a coagulant?
Alum is one of the most widely used coagulants in the water treatment industry (Benschoten and Edzwald 1990). For water and wastewater treatment, the coagulants used more frequently are the inorganic salts of aluminum.
Is Lime a coagulant?
Lime (Ca(OH)2 or CaO): Lime, or calcium hydroxide, is predominantly used to adjust pH, but as a softener, it can also be used as a coagulant aid. The lime bonds with the other particles and increases the size/weight of the flocs which then increases the speed with which they settle out of the water.
What are coagulants?
Coagulants are a substance which cause particles in a liquid to curdle and clot together. Particles stay suspended in water rather than settling because they carry surface electrical charges that mutually repel each other.
What two chemicals are commonly used as water coagulants?
Aluminum sulfate (alum) is the most common coagulant used for water purification. Other chemicals, such as ferric sulfate or sodium aluminate, may also be used.
Why alum is used as coagulant?
When alum is added to water, it reacts with the water and results in positively charged ions. Coagulation removes colloids and suspended solids from the water. These particles have a negative charge, so the positively charged coagulant chemicals neutralize them during coagulation.
What is the most used coagulant?
Iron and aluminium salts are the most widely used coagulants but salts of other metals such as titanium and zirconium have been found to be highly effective as well.
What is form when coagulant is added to water?
What is formed when coagulant is added to water? Explanation: When coagulant is added to water, then white gelatinous precipitate is formed called floc.
How effective is coagulation?
Several studies have reported the effectiveness of dual coagulants application when dealing with various types of wastewater where it can reduce up to 90% of COD, total suspended solids (TSS), turbidity, and colour.
What is coagulant milk?
Coagulation is essentially the formation of a gel by destabilizing the casein micelles causing them to aggregate and form a network which partially immobilizes the water and traps the fat globules in the newly formed matrix. This may be accomplished with: enzymes.
Is coagulation reversible?
Coagulation is irreversible, the proteins cannot be turned back into their liquid form.
How do coagulants work?
Coagulants work by creating a chemical reaction, eliminating negative charges that cause particles to repel each other. The action of these bubbles forces clots or flocs of particles to the water surface where they can be skimmed off. Dissolved air flotation is an alternative to sedimentation.
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.
Is FeCl3 a coagulant?
Ferric chloride (FeCl3) is the most common iron salt used to achieve coagulation. Its reactions in the coagulation process are similar to those of alum, but its relative solubility and pH range differ significantly from those of alum. Both alum and ferric chloride can be used to generate inorganic polymeric coagulants.
What are the types of water treatment?
Processes
- Chemical. Tanks with sand filters to remove precipitated iron (not working at the time)
- Physical. Sedimentation for solids separation that is the removal of suspended solids trapped in the floc.
- Physio-chemical.
- Biological.
- Desalination.
- Portable Water Purification.
- Boiler water treatment.
- Cooling water treatment.
What is most common used coagulant?
1. Alum (aluminum sulfate), Al2(SO4)3. Still, the most common coagulant in the United States, it is often used in conjunction with cationic polymers.
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.
Where are coagulants used?
Flocculants & Coagulants. Flocculation and coagulation treatment chemicals are used in effluent water treatment processes for solids removal, water clarification, lime softening, sludge thickening, and solids dewatering.
What are the water treatment methods?
Coagulation, flocculation and sedimentation are processes used to remove colour, turbidity, algae and other microorganisms from surface waters. Aluminium sulphate and ferric sulphate are two of the most commonly used coagulants , although others are available.
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.
What is coagulation process?
Coagulation is a process of combining particles, colloids, and dissolved organic material into larger aggregates (Amirtharajah and O’Melia, 1990). These aggregates are then removed from the water usually by clarification and filtration processes in most conventional WTWs.
Why alum is used in water treatment?
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.
