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Coagulation and Flocculation
Published in Subhash Verma, Varinder S. Kanwar, Siby John, Environmental Engineering, 2022
Subhash Verma, Varinder S. Kanwar, Siby John
Flocculation is the slow, gentle mixing of water to encourage tiny particles to collide and clump together to become settleable floc. Slow mixing is a physical process that helps to transform the microfloc formed during coagulation into macrofloc, which is easy to settle. However, as floc grows in size, it becomes more fragile, so it is important that the speed of the mixer is controlled. The idea is to get the floc particles to increase in size until they are heavy enough to settle rapidly. A typical floc size is 1–2 mm. However, floc may vary depending on the characteristics of raw water. If algae are present, they can also be trapped or caught up in the floc particles. When algae are present in large numbers, the flow will have a stringy appearance.
Produced Water Treatment Technologies
Published in Olayinka I. Ogunsola, Isaac K. Gamwo, Solid–Liquid Separation Technologies, 2022
Isaac K. Gamwo, Hossain M. Azam, Hseen O. Baled
Precipitation is considered a conventional chemical treatment processes of PW (Al-Ghouti et al., 2019). Chemical precipitation is used to remove suspended solids, dispersed oil droplets, and colloidal particles from PW using flocculation and coagulation chemicals. The basic idea is to increase the size of the solid particles so they can precipitate. In coagulation, the electrostatic repulsion between the particles is reduced by chemicals called coagulants, such as aluminum sulfate, ferric chloride, and lime. These coagulants react with the suspended particles to form precipitants. In flocculation, the particles are brought together by water-soluble polymeric agents. The addition of coagulation chemicals can remove almost 97% of SS and oil from PW (Al-Ghouti et al., 2019). Chemical precipitation is a simple technology for removing suspended particles, but it is ineffective in removing dissolved components. Another concern is the increased concentration of some toxic metals in the sludge that forms due to the use of chemicals (Duraisamy et al., 2013; Jiménez et al., 2018).
Polymers as Coagulants for Wastewater Treatment
Published in Sreedevi Upadhyayula, Amita Chaudhary, Advanced Materials and Technologies for Wastewater Treatment, 2021
Sai Harsha Bhamidipati, Dharani Prasad Vadlamudi, Sudheshna Moka
Coagulation and flocculation consist of application of chemicals to destabilize the suspended particles and promote sedimentation in wastewater treatment. In various literature, the terms coagulation and flocculation are used interchangeably and equivalently. Here, coagulation is a process by which the particles are destabilized to produce small aggregates, and flocculation involves the conversion of smaller aggregates to larger flocs. The various mechanisms involved in the coagulation are mentioned below, where it is stated that no single mechanism governs the entire process. The mechanisms mentioned below may operate in combination or one might take predominance over others, depending on the type of coagulant in regard to its charge density, molecular weight, coagulant dosage, particle concentration, pH, mixing conditions, and solvent characteristics: Double-layer compressionAdsorption and bridgingCharge neutralization and electrostatic patch mechanismSweep coagulation
Effects of ballasting particles on settling rate of iron ore tailings
Published in Particulate Science and Technology, 2020
Zhijun Zhang, Haitao Nong, Yanan Li, Liang Zhao, Hang Gao
Conventionally, fine tailing particles are treated by coagulation and flocculation processes in the thickener, which are physicochemical methods applied in wastewater treatment. Coagulation is conducted by adding inorganic salts to wastewater for the destabilization of fine particles (Hogg 2000). A variety of chemical agents are used in coagulation such as alum, lime, and ferric chloride. The agents are supposed to release corresponding cations and anions under hydrolysis in an aqueous environment, leading to reduced thickness of the double layer, reducing the repulsive force, and destabilizing the colloids. This results in a higher probability of particle aggregation (Duan and Gregory 2003). Flocculation is to use polymers to form larger flocs and strengthen flocs by adsorption, bridging, and sweeping of the particles or colloids, therefore achieving a better settling performance (Young and Edwards 2000).
Turbidity removal of fine coal–water suspension by flocculation using Taguchi (L16) experimental design
Published in Particulate Science and Technology, 2018
Flocculation with polymers is an important process in many industrial solid–liquid separation applications, such as mineral processing, papermaking, water treatment, and biotechnology. In conventional treatment, sedimentation which is used to remove the most of the impurities also exercises this particular process. On the other hand, the flocculation method is extensively used for the rapid settling of fine coal particles from recirculating plant water in coal preparation industry as well. The turbidity of any slurry predicates the suspended particulate matters in the suspension and a well-flocculated suspension should be settled leaving no suspended solids and hence has a very low turbidity. Therefore, the turbidity removal is an important process for solid–liquid separation and sedimentation.
Application of clay ceramics and nanotechnology in water treatment: A review
Published in Cogent Engineering, 2018
Ebenezer Annan, Benjamin Agyei-Tuffour, Yaw Delali Bensah, David Sasu Konadu, Abu Yaya, Boateng Onwona-Agyeman, Emmanuel Nyankson
Coagulation sometimes referred to as flocculation, is where chemicals are added to aqueous medium in bringing of small de-stabilize colloidal suspensions together to larger aggregates to allow easy removal from water. The level of strength of the Van dar waals forces plays an important role in the flocculation process. Figure 3 gives a representation of the mechanisms that can remove contaminants and thus affects flow. Two particles can agglomerate in the same aqueous phase to remove different contaminants. The agglomeration of the two particles can be enhanced with the aid of a "binder". Indeed the varying factors need to be experimented to ensure the good mix and also attain most agglomeration of the bi-particles. In cases where single medium is being used, a bio-compatible and anhydrous powder with high Van der waals force to attain effective coagulation could be employed. Most villagers in developing countries are prone to the use of alum and chlorination of their river dependent water to ensure some level of coagulation. In most cases the quantities are not accurate and may be the cause of other long-term health effects.