Coagulants are designed to improve liquid-solid separation in wastewater treatment. The use of coagulants in wastewater treatment is crucial, because it enables the removal and dewatering of particles, water purification, lime softening, and sludge thickening.
Coagulants aid businesses in maintaining a regular and dependable source of clean water, to support their industrial processes, along with the use of additional specialised chemicals and mechanical filtration techniques.
Let’s understand the objective and aim of coagulation in the treatment of wastewater.
History of coagulation
As early as 2000 BC, when the Egyptians employed almonds to clarify river water, coagulation has been used in wastewater treatment to clear water. Additionally, there is evidence that suggests the Romans began employing alum, as a coagulant about the year 77 AD.
Coagulation technique in the present times
Coagulation and flocculation are still crucial parts of treatment procedures today, lowering water turbidity being one example. Coagulation is necessary during wastewater treatment processes for the elimination of chemical phosphorus, and the reduction of suspended solids.
What is coagulation in the treatment of wastewater?
Coagulation is a very straightforward chemical process that includes mixing insoluble substances together, by adjusting the charges of particles and adding iron or aluminium salts to a wastewater stream, such as aluminium sulphate or ferric sulphate. The main benefit of utilizing a coagulant, in addition to removing other small particles from suspension, is that it makes the water clearer by reducing turbidity.
The negatively charged particles in the water are balanced by the positive charge of the coagulants. This leads to the formation of bigger flocs from the suspended particles in the water. At the base of the water supply, these bigger flocs start to assemble. The floc settles more quickly, as larger the particle size.
Contaminants removed using coagulation
Several different pollutants, such as the following, contribute to the contamination or toxicity of your water, and are removed by coagulation:
· Natural Organic Matter (NOM)
· Dissolved Organic Carbon
· Organic molecules
· Inorganic precipitates that are suspended
· Germs and viruses
Process of coagulation
Industrial water sources are brought into the ideal chemical state through coagulation, for simple mechanical filtering. Once the flocs have accumulated at the bottom of your clarifier, tools like a filter press can be used to remove the bigger aggregated particle clumps, reintroducing clean water into your system.
Coagulants, clarifiers, and filter presses combined offer a maximum water recovery rate of nearly 95%. You can construct a process that is almost completely closed-loop, because less water is actually discharged with the solids.
How does water treatment use coagulants?
Coagulants must be used to chemically start the process in order to use coagulation in water treatment. These specialised chemicals should be created based on a particle analysis of your dissolved/suspended solids, to fulfil your unique water quality application.
The decision between organic and inorganic coagulants is the most important one when picking a coagulant.
What coagulations are typically found in Wastewater Treatment?
· Biological Coagulation
The best coagulants to employ for solid-liquid separation are organic ones. They make excellent choices when attempting to lower sludge creation. These coagulants, which are organic in origin, also have the advantages of acting at lower doses and not affecting the pH of your water.
The most popular organic coagulants are polyamines, which are cationic coagulants that only utilize charge neutralisation to act. The negative charge of the colloids in your water is neutralised by these, which create a spongy mass known as a "microfloc." They don't provide any advantages over the sweep-floc mechanism, because they only coagulate by charge neutralisation.
· Melamine Formaldehydes and Tannins
These natural coagulants coagulate colloidal particles in the water and also add their own precipitated floc, which is somewhat similar to how inorganic coagulants act. This sweep-floc precipitate can coagulate undesirable particles in your water, while absorbing organic compounds like oil and grease.
These coagulants are excellent for processes that produce hazardous sludge, such as what is found in oil refineries, because the precipitate dewaters everything to low moisture concentration. The main benefits of organic coagulants are their low dosage, low sludge production volume, and lack of pH impact.
· Inorganic Coagulant
Because, they are often less expensive than their organic equivalents, inorganic coagulants are an economical choice for a variety of water treatment applications. They work particularly well when applied to low-turbidity raw water.
Inorganic coagulants produce aluminium or iron precipitates when they are added to water. This aids in water purification by soaking up contaminants as they fall into the water. It is known as the "sweep-floc" mechanism. However, this can increase the total volume of sludge that needs to be treated and removed, so it's not always the best option.
The most common kinds of inorganic coagulants consist of:
Many people prefer using aluminium sulphate (alum) as their preferred coagulant, because it is one of the most widely utilized water treatment chemicals in industrial processes. Alum is produced as a liquid, and when it is dehydrated, it transforms into its crystalline form. Alum is somewhat toxic and has similar health effects and corrosion properties, to diluted sulphuric acid.
Aluminium chloride is a coagulant that functions similarly to alum but is costlier, riskier, and more caustic. As a result, it is typically only chosen as a backup in procedures when alum couldn't be used.
The inorganic coagulants, Polyaluminum chloride (PAC) and aluminium chlorohydrate (ACH), work better with simpler water sources.
While, ferric sulphate is more frequently utilised, both iron coagulants, ferrous sulphate and ferric sulphate, function similarly to aluminium coagulants. In situations when a reducing agent or extra soluble iron ions are needed, ferrous sulphate is frequently a wise choice.
Ferric chloride is the least priced inorganic coagulant since it is produced as a waste product, from steel manufacturing processes. It is, however, only utilised in settings that are equipped to handle its reputation, as the most dangerous and corrosive inorganic coagulant.
Once you have the proper coagulant, you quickly mix these chemicals into your unclean water. This makes it simple and quick to move the coagulant throughout the water.
In general, as long as these coagulants are used correctly and in the recommended dosage, their residuals or by-products do not represent a threat to the quality of the water. Due to this, hiring a water treatment specialist is essential. The coagulation process can also be configured by experts with experience in wastewater treatment, so that the coagulant chemicals are eliminated together with the floc during filtration.
Consult your water treatment experts at Netsol Water!
Netsol provides complete water treatment help for industrial operations of any kind, thanks to our chemical competence and mechanical filtration understanding.
We provide a variety of pretreatment chemical products, including pH adjusters, corrosion inhibitors, and biocides, in addition to specifically coagulants, and other water treatment products. From industrial boilers and cooling towers to mining operations and concrete manufacturing, Netsol provides the knowledge you need to keep your systems operating.
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