The relationship between the optimum chitosan dosage and the tur. Coagulationflocculation process for produced water treatment. Hence in coagulation process, the suspended particles are removes by combining small particles into large particles li et al. Coagulation except in polymer science flocculation except in polymer science process of contact and adhesion whereby dispersed molecules or particles are held together by weak physical interactions ultimately leading to phase separation by the formation of precipitates of larger than colloidal size.
In the coagulation and flocculation solids processes,nonsettleable solids are converted into large and heavier settleables solids by physical chemical changes brought about by adding and mixing coagulant chemicals into the raw water. However, colloidal particles in water have insufficient mass to. Thus, the particles combine to form larger particles and this is achieved by rapid mixing of solution which spreads the coagulant agent completely. Flocculation is the slow stirring or gentle agitation to aggregate the destabilized particles and form a rapidsettling floc. Flocculation of hydrophobic and hydrophilic colloidal particles in nearcritical pyrrolidonewater mixtures. Coagulation and flocculation water treatment waste. By adding some chemicals, the surface property of such colloidal particles can be changed or dissolved material can be precipitated so as to facilitate the separation of solids by gravity or filtration. Coagulation or flocculation of colloids pt i youtube. Introduction the need to clarify water aesthetics and health colloids impart color and turbidity to water aesthetical acceptability microbes are colloids too 042716 water treatment 2. The use of these techniques is illustrated for dlvotype particles by recent studies of floc dissociation, and the structures of aggregates produced by reversible flocculation and irreversible coagulation. Previously, we suggested an original technique for colloidal particles separation from water based on physical flow manipulation by an oscillating device. Coagulation and flocculation constitute the backbone processes in most water and advanced wastewater treatment plants.
Groundwater and surface water contain both dissolved and suspended particles. In flocculation the destabilized suspended particles are agglomerated into large rapidly settling flocs l. The process of precipitation of colloidal particles due to aggregation of the particles is called coagulation or flocculation. Colloidal particles always carry an electric charge.
Coagulation and flocculation are used to separate the suspended solids portion from the water. A series of batch flocculation tests with chitosan under different conditions was also con ducted. J j m janssen, j j m baltussen, a p van gelder and j a a j perenboom. Location in the treatment plant after the source water has been screened and has passed through the optional steps of prechlorination and aeration. Coagulation is, the effect produced by the addition of a chemical to a colloidal dispersion resulting in particle destabilization by the reduction of the forces tending to keep the particles apart. Flocculation is the aggregation of a colloid by polymer molecules flocculant bridging between the colloidal particles and forming large fragile network structures flocs, which may be easily removed by sedimentationflotation and filtering. Coagulation large particles can easily be removed by settling. Recovery or removal of colloidal particles is a serious problem in many processes involving particulate solids. The brownian thermal motion of particles, turbulence, presence of a shear field, and external forces such as gravity and electrical forces could cause coagulation. Principles of coagulation and flocculation herman 1983. Material for this article was largely taken from reference 1. Coagulation and flocculation in water treatment prepared by.
Dec 26, 2016 coagulation involves the use of a coagulant which has the potential to destabilize the previously stabilized charged particles in the suspension. Coagulation involves the use of a coagulant which has the potential to destabilize the previously stabilized charged particles in the suspension. Coagulation and flocculation in water and wastewater. Coagulation is the destabilization of colloidal particles brought about by the addition of a chemical reagent called as coagulant. Flocculation is the step where destabilized colloidal particles or the particles formed during the coagulation step are assembled into aggregates.
A colloid is a heterogeneous mixture of one substance of very fine particles dispersed phase dispersed into another substance dispersion medium. To aid this floc to coalesce with neighbouring particles and grow into larger flocs with more settleable masses, the water is gently stirred. Get to know about the coagulation of colloidal solutions, coagulation techniques and more with byjus. Coagulation of colloidal particles in water by chitosan. The aggregation is controlled by a combination of hydrodynamic and surfacechemical interactions. Flocculation is a water treatment process following coagulation. A series of batch flocculation tests with chitosan under different conditions was also conducted. Nonsettleable particles in water are removed by the use of coagulating chemicals. Coagulation is the transformation of colloidal and dispersed particles into small flocs. The colloidal particles are able to scatter light, so the effectiveness of this coagulation and flocculation process can be determined by measurement of the turbidity before and after the treatment. Coagulation or flocculation, using inorganic electrolytes or coagulants, polymers or polyelectrolytes and surfactants, is normally employed for this purpose. Colloidsare very small particles turbidity and color causing particles that can not be removed neither by.
Thus, we can understand the process of coagulation and flocculation with the help of examples derived from water treatment techniques. Coagulation indicates the process which colloidal particles and very fine solid suspensions are destabilized, so that they can begin to agglomerate if the conditions are appropriate. In this paper, results are reported that show the interaction between primary and secondaryminimum flocculation when the interparticle potential curve reflects both attractive and electrostatic repulsive forces. The object of coagulation and subsequently flocculation is to turn the small particles into larger particles called flocs, either as precipitates or suspended particles. Coagulation and flocculation process may be used as a pretreatment step prior to biological treatment in order to enhance the biodegradability of organic compounds amuda and amoo, 2007 or to increase the efficiency of removal of colloidal particles colla et al. Correct application of coagulation and flocculation depends upon these factors. Colloidal particles removal from water is a challenge in surface water treatment. In addition to removing turbidity from the water, coagulation and flocculation process removes many bacteria which are suspended in the water and can be used to remove color from the water. Colloidal particles colloids are midway in size1 between dissolved solids and. Colloidal particle an overview sciencedirect topics. Flocculation of hydrophobic and hydrophilic colloidal.
Colloidal particles carry charges on their surface, which lead to the stabilization of the suspension. Industrial examples include water treatment 1, mineral beneficiation 2, pulp. The diameter of the particles is about 10 nm and its flocculate shows network structure which benefits to adsorbingbridging in doubly distilled water. The settleable solids can then be removed by the sedimentation and filtration processes. Coagulationflocculation process for produced water. Their mass allows them to settle to the bottom of a tank and then be removed as sludge. For the love of physics walter lewin may 16, 2011 duration. Effects on effluent quality of industrial waste water.
At first glance, coagulation flocculation is a simple process. Coagulation is achieved by various mechanisms such as interparticle bridging, charge. Development of an oscillationbased technology for the. The objective of flocculation is to provide increasein thenumberof. Coagulation is a chemical process that involves neutralization of charge whereas flocculation is a physical process and does not involve neutralization of charge. Agglomeration except in polymer science coagulation except in polymer science flocculation except in polymer science process of contact and adhesion whereby dispersed molecules or particles are held together by weak physical interactions ultimately leading to phase separation by the formation of precipitates of larger than colloidal size. However the coagulation and flocculation processes are similar but not the same. More specifically, aggregate is used to describe the structure formed by the cohesion of colloidal particles.
The process of coalescence is known as flocculation. In coagulation, colloidal particles are destabilized by neutralizing those opposite forces which keep them separate. Brownian flocculation of polymer colloids in the presence. Coagulation of colloidal solutions and coagulation techniques. Computer simulation of the coagulation and flocculation of. Ene 806 project report 2 coagulation and flocculation. Coagulation is a process of accumulation and settling down of particles within a colloid.
Colloid particles are removed from water via coagulation and flocculation processes. This article provides an overview of the processes and looks at the latest thinking. Well, according to the general definition, coagulation is one of the various properties exhibited by colloidal solutions. Difference between coagulation and flocculation coagulation. Flocculation brings the deestablished colloidal particles together and they form large aggregates. Analytical methods and their applied results in the flocculation dynamics on the basis of geometric structure and binary collision process are reportedthe author refers to flocculation in terms of the dissolved polymer as colloidal aggregation. Pdf waste water treatment by coagulation and flocculation. Coagulation is the process by which colloidal particles and. In contrast, in flocculation, the destabilization is brought about by physical techniques such as mixing of the solution, and also sometimes by the addition of polymers. The flocculation step can only operate on a waterwastewater where the particles are already destabilized. Coagulation and flocculation in water and wastewater treatment. To ensure uniform dispersions of the coagulant a rapid mixing system is required at the. A colloid is a heterogeneous mixture of one substance of very fine particles dispersed phase dispersed into another substance dispersion.
Many types of particles may settle out of water on their own. Pdf coagulation of colloidal particles in water by chitosan. Because small suspended and colloidal particles and dissolved constituents will not settle in a reasonable. Coagulation is the addition and rapid mixing of coagulants the destabilization of colloidal and fine particles the initial aggregation of destabilized particles flocculation is the gentle agitation to aggregate destabilized particles to form rapidsettling floc. The results show that the colloidal hydrated manganese dioxide shows negative electricity in doubly distilled water and raw water. Coagulation of colloids methods associated colloids. However, the resulting aggregate in both cases, coagulation and flocculation, is referred to as a floc. Magnetic hetero flocculation of paramagnetic colloidal particles. Its used in the first stage of solidsliquids separation. The coagulationflocculation processes facilitate the removal of ss and colloidal particles. Flocculation refers to the process used to bring the coagulated particles together so that they can combine to form larger, settleable, and filterable masses of particles called floc. Science chemistry colloids coagulation of colloidal solution. Coagulation and flocculation provide the water treatment process by which finely divided suspended and colloidal matter in the water is made to agglomerate and form flocs. The purpose of coagulation and flocculation is to remove particulate impurities, especially nonsettleable solids and colour from the water being treated.
Coagulation, flocculation and clarification of drinking water. Colloidal particles are too small to be removed by sedimentation or by sand filtration processes. The main factors considered are brownian motion, external fields, and the roles of interparticle hydrodynamic and colloidal interactions. Coagulation, a process of agglomerating colloidal particles, using chemicals such as aluminum sulfate, ferrous sulfate, ferric chloride, aluminum chloride, etc. Coagulation and flocculation are an essential part of wastewater treatment in a variety of industries. Today, the coagulation and flocculation processes are implemented with the purpose of agglomerate colloids and fine particles in water into larger particles, which is also known as floc. Effects on effluent quality of industrial waste water using. Both these techniques are employed in the treatment of water. Coagulation and flocculation water treatment waste water. Waste water treatment by coagulation and flocculation. The feasibility of applying chitosan, as prepared from the crab chitin, was assessed in this study for the coagulation of colloidal particles. Design of slow mixing flocculation units destabilized colloids resulting from coagulation may still settle very slowly flocculationis a slow mixing process in which these particles are bought into contact in order to promote their agglomeration. This enables their removal by sedimentation, dissolved air flotation or filtration.
Their objective is to enhance the separation of particulate species in downstream processes such as sedimentation and filtration. The primary purpose of the coagulation and flocculation is to destabilize the charged colloidal particles in water and make them to settle so as to remove turbidity from the water. The results indicate that chitosan is a potent coagulant for bentonite suspension. The presence of the same type of electric charge on colloidal particles causes repulsion and keep them in a suspended state. Apr 27, 2016 coagulation and flocculation in water treatment prepared by. Image and coagulation behavior of colloidal hydrated.
Addition of positively charged particles in the coagulation process is aimed to destabilizing the colloids. Coagulation and flocculation are an essential part of drinking water treatment as well as wastewater treatment. So treatment involving coagulation and flocculation is typical of surface water. To meet the requirements of potable, industrial and agricultural water, the immediate need is to treat waste water, particularly the sewage sludges and slimes from the municipal and industrial effluents respectively. Coagulation is the process used to reduce the energy forces present around particles that tend to keep them from joining together to form a larger mass. As a result, they stay dispersed and dissolved or coagulation process colloidal in the water. Aggregation is the process or the result of the formation of aggregates. Furthermore, the product of the coagulation between these particles and hydroxoalum complexes has low solubility levels in the ph range of normal use. Prospects and challenges of using coagulationflocculation. Pure water is an essential requirement for the survival of human beings. The coagulation flocculation process can be used as a preliminary or intermediary step between other water or wastewater treatment processes like filtration and sedimentation.
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