The performance of coagulation is the major factor in improving water treatment efficiency. Water industries globally consider coagulation/flocculation is one of the major treatment units used to improve overall treatment efficiency and cost effectiveness for water and wastewater treatment.
What is the role of coagulation in water treatment?
Coagulation plays primary and important roles in water and wastewater treatment. Researches are needed for novel coagulants, hybrid processes and control schemes. Study of floc properties is essential to enhance the coagulation efficiency. The performance of coagulation is the major factor in improving water treatment efficiency.
What is coagulation/flocculation and why is it important?
Water industries globally consider coagulation/flocculation is one of the major treatment units used to improve overall treatment efficiency and cost effectiveness for water and wastewater treatment.
When was the first coagulant used in water treatment?
Modern use of coagulants for water treatment started more than 100 years ago and researches on coagulation have been continuously undertaking since then.
What is a a coagulant?
A coagulant is a chemical that is used to remove suspended solids from drinking water. They are made up of positively charged molecules, which help to provide effective neutralization of water.
Why coagulation is so important for wastewater treatment?
Coagulation helps to remove a number of different pollutants that cause your water to become dirty or toxic, including: Organic compounds and certain dissolved organic materials, commonly referred to as Natural Organic Matter (NOM) or Dissolved Organic Carbon (DOC)
What causes coagulation in water treatment?
Coagulation is a somewhat simple chemical process that involves bringing insoluble materials together by manipulating the charges of particles, by adding iron or aluminum salts, such as aluminum sulfate or ferric sulfate, to a wastewater stream.
What is the function of coagulation in water treatment quizlet?
The purpose of coagulation and flocculation is to remove particulate impurities and color from the water being treated.
Why is coagulation and flocculation important?
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. Correct application of coagulation and flocculation depends upon these factors.
What is the principle of coagulation?
At a glanceWorking PrincipleSuspended particles are destabilised by addition of a clarifying agent leading to the neutralisation of their charges. Particles thus agglomerate (flocs formation) and are able to decant.Main strengthRemoves solids and improves filtrationMain weaknessContinuous input of chemicals required6 more rows•May 24, 2019
What is the most important consideration in coagulation flocculation process control?
The most important consideration in coagulation-flocculation process control is selection of the proper type and amount of coagulant chemical(s) to be added to the water being treated. This decision is made with the help of a jar test.
What is the purpose of adding a coagulant like aluminum sulfate alum to the raw water?
Chemicals (coagulants) are added to the water to bring the nonsettling particles together into larger, heavier masses of solids called floc. Aluminum sulfate (alum) is the most common coagulant used for water purification.
Why does secondary treatment of wastewater require O2?
Why does secondary treatment of wastewater require O2? - to encourage microbial growth. p. 787 - microbial growth is actively encouraged during secondary treatment, allowing aerobic organisms to oxidize the biologically degradable organic material to carbon dioxide and water.
What is coagulation in water?
Coagulation is a process for combining small particles into larger aggregates (flocs) and for adsorbing dissolved organic matter on to particulate aggregates so that these impurities can be removed in subsequent solid/liquid separation processes. The modern use of coagulants for water treatment started more than 100 years ago, when ferric chloride and aluminum sulfate were used as coagulants in full-scale water treatment works. The coagulation mechanism was firstly explained by the Schultz–Hardy rule and the Smoluchowski's particle collision function, which form the theoretic basis of coagulant demand and changes in particle number in flocculation process. Mattson [ 1] firstly derived that the hydrolysis products of Al and Fe salts were more important than the trivalent ions themselves, although this approach was widely accepted and accorded its proper position in coagulation chemistry 30 years later. Black and co-workers [ 2] conducted a series of studies on the effect of pH and various anions on the time of floc formation. After these early studies, the coagulation research focused on the study to produce better flocs and search for better coagulant aids including bentonite, silicates, and limestone.
What are coagulants used for?
Coagulants used for water and wastewater treatment are predominantly inorganic salts of iron and aluminum. When dosed into water the iron or aluminum ions hydrolyse rapidly and in an uncontrolled manner, to form a range of metal hydrolysis species.
What is the IEP of a titanium floc?
The floc isoelectric point (IEP) was found to be near pH 5, and the titanium flocs possessed greater density, diameter and settling velocity than the aluminum flocs. The titanium flocs were composed of TiO (OH) 2, which would change from the amorphous phase into anatase TiO 2 under elevated temperatures.
Which chemistry was first derived from the hydrolysis products of Al and Fe salts?
Mattson [ 1] firstly derived that the hydrolysis products of Al and Fe salts were more important than the trivalent ions themselves, although this approach was widely accepted and accorded its proper position in coagulation chemistry 30 years later.
Is coagulation a part of disinfection?
Coagulation will still play an important role, directly or indirectly, in the control of particulates, microorganisms, natural and synthetic organic matter, precursors of disinfection by-products (DBPs) and some inorganic ions and metals in water and wastewater treatment. Indeed, the performance of coagulation process is one ...
What are Coagulation and Flocculation in Water Treatment?
Coagulation and flocculation are two processes that go together in water treatment. They are separate, but they are used one after the other to remove particles in water.
How Coagulation Water Treatment Works
Coagulation water treatment prevents the suspended particles from repelling one another and encourages them to form into clumps, or flocs.
How Flocculation Works
The flocculation process follows coagulation in water treatment. Coagulation is the charge neutralisation of fine particles, and flocculants are the agents that then promote the clumping of these particles together.
How Does Temperature Affect Coagulation in Water Treatment?
Temperature can have a significant effect on coagulation and flocculation.
Is Coagulation Caused by Bacteria in Water Treatment?
Suspended solids in water can be the result of natural causes, arising from organic materials such as algae, or inorganic materials such as sediment or silt.
How to Maximise the Effects of Water Treatment
Coagulation is a long-established water treatment, but it doesn’t remove all bacteria from water systems.
How is coagulation affected by pretreatments?
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.
What is the difference between coagulation and flocculation?
Coagulation (water treatment) In water treatment, coagulation flocculation involves the addition of compounds that promote the clumping of fines into larger floc so that they can be more easily separated from the water. Coagulation is a chemical process that involves neutralization of charge whereas flocculation is a physical process ...
What is the SCD for coagulant dose?
The SCD measures the net surface charge of the particles and shows a streaming current value of 0 when the charges are neutralized ( cationic coagulants neutralize the anionic colloids ). At this value (0), the coagulant dose can be said to be optimum.
What force causes colloidal particles to cling together?
Once the repulsive charges have been neutralized (since opposite charges attract), van der Waals force will cause the particles to cling together (agglomerate) and form micro floc.
Why do colloidal particles settle slowly?
In a colloidal suspension, particles will settle very slowly or not at all because the colloidal particles carry surface electrical charges that mutually repel each other. This surface charge is most commonly evaluated in terms of zeta potential, the electrical potential at the slipping plane. To induce coagulation, a coagulant (typically a metallic salt) with the opposite charge is added to the water to overcome the repulsive charge and "destabilize" the suspension. For example, the colloidal particles are negatively charged and alum is added as a coagulant to create positively charged ions. Once the repulsive charges have been neutralized (since opposite charges attract), van der Waals force will cause the particles to cling together (agglomerate) and form micro floc.
Is coagulation a physical process?
Coagulation is a chemical process that involves neutralization of charge whereas flocculation is a physical process and does not involve neutralization of charge. The coagulation-flocculation process can be used as a preliminary or intermediary step between other water or wastewater treatment processes like filtration and sedimentation.
Why is coagulation important?
Coagulation plays primary and important roles in water and wastewater treatment. Researches are needed for novel coagulants, hybrid processes and control schemes. Study of floc properties is essential to enhance the coagulation efficiency.
What is the performance of coagulation?
The performance of coagulation is the major factor in improving water treatment efficiency. Water industries globally consider coagulation/flocculation is one of the major treatment units used to improve overall treatment efficiency and cost effectiveness for water and wastewater treatment.
The role of coagulation in wastewater treatment
In the wastewater treatment process, coagulants play a critical role in dealing with sludge. Often used in combination with other mechanical filtering processes and treatment chemicals, using coagulants helps to thicken the sludge into a form which allows the solids and other particles which are contaminating the water to be easily removed.
The history behind coagulation in the treatment of wastewater
The idea of using coagulation as a way to clean up dirty water is nothing new. There is evidence that the Ancient Egyptians were adding almonds to water in rivers as an attempt to clean it up as early as 2,000 BC. The Romans even added a chemical called alum to water as a coagulant as early as the 8 th century.
How does coagulation work?
In simple terms, coagulation describes a chemical reaction. It involves adding a special chemical product called a coagulant, something like iron or aluminium salts to the wastewater, which then affect the electrostatic charge associated with the small particles suspended in the water.
Where can coagulation be used?
Coagulation can be used in a range of different situations, to deal with specific pollutants affecting your water and causing it to become contaminated. Coagulation is particularly effective against:
How coagulation aids mechanical filtration
The main idea behind using coagulation as a treatment for wastewater is to create a state in the water that allows effective mechanical filtration of the effluent. This involves the formation of flocs or clumps of solid material.
What are the different types of wastewater coagulants?
Coagulation doesn’t happen by itself, and in order to kick-start the process you have to add special coagulant chemicals into the wastewater treatment system. The exact combination of chemicals you’ll use will typically depend on the type and concentration of contaminants that are affecting your effluent streams, and the chemical composition.
Organic coagulants
For solid-liquid separation, one of the best options to think about first is the use of organic coagulation. Organic coagulants are also effective when trying to reduce the total volume of sludge which is created as part of the treatment process.
What Coagulants Are Used In Water Treatment?
In order to use coagulation in your water treatment, you have to apply coagulants to chemically initiate the process. These specialty chemicals should be formulated to meet your specific water quality application based on a particle analysis of your dissolved/suspended solids.
Organic Coagulants
Organic coagulants are best used for solid-liquid separation. They are also good options to use when trying to reduce sludge generation. Being organic in nature, these coagulants offer the added benefits of working at lower doses and having no effect on the pH of your water.
Inorganic Coagulants
Inorganic coagulants are typically cheaper than their organic counterparts, making them a cost-effective solution for a broad range of water treatment applications. They are especially effective when used on raw water with low turbidity.
ChemREADY: Your Water Treatment Experts
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What is Coagulation in Wastewater Treatment?
Coagulation is a somewhat simple chemical process that involves bringing insoluble materials together by manipulating the charges of particles, by adding iron or aluminum salts, such as aluminum sulfate or ferric sulfate, to a wastewater stream.
What Coagulants Are Used In Water Treatment?
In order to use coagulation in your water treatment, you have to apply coagulants to chemically initiate the process. These specialty chemicals should be formulated to meet your specific water quality application based on a particle analysis of your dissolved/suspended solids.
What Are The Common Coagulation In Wastewater Treatment?
Organic coagulants are best used for solid-liquid separation. They are also good options to use when trying to reduce sludge generation. Being organic in nature, these coagulants offer the added benefits of working at lower doses and having no effect on the pH of your water.
ChemREADY: Your Water Treatment Experts
With our chemical expertise and mechanical filtration knowledge, ChemREADY offers total water treatment assistance for industrial processes of any kind.
Overview
In water treatment, coagulation and flocculation involve the addition of compounds that promote the clumping of fine floc into larger floc so that they can be more easily separated from the water. Coagulation is a chemical process that involves neutralization of charge whereas flocculation is a physical process and does not involve neutralization of charge. The coagulation-flocculation pr…
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.
Mechanism
In a colloidal suspension, particles will settle very slowly or not at all because the colloidal particles carry surface electrical charges that mutually repel each other. This surface charge is most commonly evaluated in terms of zeta potential, the electrical potential at the slipping plane. To induce coagulation, a coagulant (typically a metallic salt) with the opposite charge is added to the water to overcome the repulsive charge and "destabilize" the suspension. For example, the c…
Determining coagulant dose
The dose of the coagulant to be used can be determined via the jar test. The jar test involves exposing same volume samples of the water to be treated to different doses of the coagulant and then simultaneously mixing the samples at a constant rapid mixing time. The microfloc formed after coagulation further undergoes flocculation and is allowed to settle. Then the turbidity of the sampl…
Limitations
Coagulation itself results in the formation of floc but flocculation is required to help the floc further aggregate and settle. The coagulation-flocculation process itself removes only about 60%-70% of Natural Organic Matter (NOM) and thus, other processes like oxidation, filtration and sedimentation are necessary for complete raw water or wastewater treatment. Coagulant aids (polymers that bridge the colloids together) are also often used to increase the efficiency of the …
See also
• Electrocoagulation
• Industrial wastewater treatment
• Industrial water treatment