what is coagulation water treatment

What is coagulation in water treatment process?

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.Dec 20, 2019

What is purpose of coagulation?

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.Feb 19, 2015

What is flocculation and coagulation in water treatment?

Coagulation and flocculation occur in successive steps intended to overcome the forces stabilising the suspended particles, allowing particle collision and growth of flocs, which then can be settled and removed (by sedimentation) or filtered out of the water.May 24, 2019

Why is a coagulant used to treat water?

Coagulation treatment is usually carried out before sedimentation and filtration. During the process, a coagulant is added to water, and its positive charge neutralizes the negative charge of suspended contaminants. Neutralization causes suspended particles to bind together (hence the term).Oct 15, 2021

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 do you mean by coagulation?

Definition of coagulation : the process of becoming viscous or thickened into a coherent mass : the forming of clots (as in blood or cream) : the process of coagulating …

What is coagulation or flocculation?

Coagulation and flocculation are two separate processes, used in succession, to overcome the forces stabilising the suspended particles. While coagulation neutralises the charges on the particles, flocculation enables them to bind together, making them bigger, so that they can be more easily separated from the liquid.

What is meant by coagulation and flocculation?

Coagulation is the destabilization of colloidal particles brought about by the addition of a chemical reagent called as coagulant. Flocculation is the agglomeration of destabilized particles into microfloc and after into bulky floccules which can be settled called floc.

What is the difference between sedimentation and coagulation?

Answer: sedimentation is the separation of a suspension of solid particles into a concentrated slurry and a supernatant liquid, either to concentrate the solid or to clarify the liquid while coagulation is the precipitation of suspended particles as they increase in size (by any of several physical or chemical.Jan 14, 2020

What is the most common coagulant in water treatment?

Aluminum sulfate (alum)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. Coagulation is usually accomplished in two stages: rapid mixing and slow mixing.

Which is example of coagulant?

Examples of primary coagulants are metallic salts, such as aluminum sulfate (referred to as alum), ferric sulfate, and ferric chloride.

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.

What is coagulation in water treatment?

Water and wastewater may contain suspended and dissolved impurities that must be removed in order to meet certain water quality criteria. These impurities include:

What is the purpose of coagulation?

Coagulation is a chemical process in which a chemical compound, a “coagulant”, is added to the water, in order to destabilize the suspended particles and promote creation of flocs. A ‘Stable colloidal particle’ is a colloidal particle that remains as a separate entity in the water, i.e. in a dispersed state.

What are coagulants made of?

Organic coagulants include polyamines, polyDADMACS, dicyandiamide and melamine formaldehyde. Inorganic coagulants are mostly based on metallic salts, such as iron sulfate and aluminum sulfate. When they are introduced to the water, they react with the alkalinity of the water and hydrate to form a metal hydroxide.

What are the different types of coagulants used in wastewater treatment?

Types of coagulants used in water and wastewater treatment: Coagulants can be classified as organic coagulants and inorganic coagulants. Organic coagulants are cationic polymers with high molecular weight.

What are the advantages of organic coagulants?

The major advantage of organic coagulants is that produce much less sludge than inorganic coagulants, due to their higher efficiency . Another advantage is that they do not affect the pH of the treated water. Organic coagulants include polyamines, polyDADMACS, dicyandiamide and melamine formaldehyde.

What is the pH of a coagulant?

Therefore, each coagulant has an optimal pH range in which it works best. For example, Alum works best at a pH of 5.8-6.5, Aluminium chlorohydrate (ACH) works at a pH range of 6.5-7.5.

What is the term for the adsorption and bridging of electrolytes?

Adsorption and bridging. Precipitation, or sweep-coagulation. Compression of the double layer – when electrolytes are introduced. Higher concentration of electrolytes neutralizes more charges, and as a result the thickness of the double electrical layer is reduced, and particles get closer to each other.

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.

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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.

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 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 most widely used water treatment technology?

Many water treatment plants use a combination of coagulation, sedimentation, filtration and disinfection to provide clean, safe drinking water to the public. Worldwide, a combination of coagulation, sedimentation and filtration is the most widely applied water treatment technology, and has been used since the early 20th century.

What is residual water?

Residuals are the by-products that remain in the water after substances are added and reactions occur within the water. The particular residuals depend on the coagulant that is used. If ferric sulphate is used, iron and sulphate are added to the water. If ferric chloride is used, iron and chloride are added.

Why are pathogens removed from water?

Usually, the pathogens that are removed from the water are removed because they are attached to the dissolved substances that are removed by coagulation. In the picture below, the coagulants have been added to the water, and the particles are starting to bind together and settle to the bottom.

What is added to ferric chloride?

If ferric chloride is used, iron and chloride are added. And if aluminum sulphate is used, aluminum and sulphate are added. The majority of municipal water treatment plants use aluminum sulphate as the coagulation chemical. Generally, water treatment facilities have the coagulation process set up so that the coagulant chemicals are removed with ...

What is coagulation in water 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.

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 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.

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.)

Is alum a good coagulant?

It’s the same principle with wastewater treatment. 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. Coagulation is especially useful in removing the chemical phosphorus from water. Yet coagulation water treatment is far ...

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 is the name of the coagulating agent formed when aluminum hydrolyzes?

Hydroxides: e.g., aluminum hydroxide (a polymeric hydroxide formed when aluminum hydrolyzes) is an excellent coagulating agent. Oxyhydroxides.

What is the process of separating flocculated materials from water?

The process traditionally utilizes an anode and a cathode, stimulated by a DC power source to destabilize the charges. This operation separates flocculated materials from water, allowing those materials to be removed, leaving clear water.

What is the largest detractor in electrocoagulation?

Perhaps its largest detractor is passivation. During the electrocoagulation process, electrodes become coated and fouled with a non-conducting oxide, especially when processing wastewater with high concentrations of dissolved solids and scaling compounds.

Overview

Factors

Mechanism

Determining Coagulant Dose

Limitations

See also