The coagulation-flocculation process can be used as a preliminary or intermediary step between other water or wastewater treatment processes like filtration and sedimentation. Two steps typically are employed: coagulation and flocculation. This will be discussed at length in the filtration chapter of the text, but it’s important to have a basic grasp of that concept at this point in the treatment process. Removing oil from wastewater through coagulation is a physical and chemical method, including aggregation and flocculation two processes (Wen et al., 2018).The oil removal process is shown in Fig. Coagulation and flocculation 14.1 Introduction Coagulation and flocculation provide the water treat-ment process by which finely divided suspended and colloidal matter in the water is made to agglomerate and form flocs. Coagulation Chemical treatment typically is applied prior to sedimentation and filtration to enhance the ability of a treatment process to remove particles. Because of this, the sedimentation step is usually preceded by a chemical process known as coagulation. Have questions or comments? The physical removal of pathogens is accomplished in several steps. Coagulation means to curdle; it basically refers to a chemical process in which the destabilization of non- settleable particles takes place. 0000022998 00000 n 0000014191 00000 n It is important that floc has good size but also density so the floc will not shear during the sedimentation and filtration process. The equation used to calculate detention time, if the flow is in gallons per minute, is: Coagulation forms a mass by neutralizing charges of impurities in the water stream which can then be joined and settled by the addition of a flocculent. However, they can be commonly adopted for de-stabilizing any suspension system. Coagulation and Flocculation in Water and Wastewater Treatment is a readable and useful resource for the water scientist and engineer. What is Coagulation and Flocculation? Operators use different charged groups of polymers known as cationic (positive), anionic (negative), and nonionic (without ionizable groups). The equation used to calculate detention time, if the flow is in gallons per minute, is: In potable water treatment, clarification of water using coagulating agents has been practiced from ancient times. If the raw water has a low pH, agents such as soda ash can be added to increase the pH. 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. 0000017291 00000 n %%EOF They can also be referred to as nonstable solids. The function of a flocculation basin is to ___________. 0000001159 00000 n 0000001599 00000 n Coagulation and flocculation are two processes commonly used in water treatment in order to get rid of unwanted suspended material in water. The most common primary coagulant is ___________. Many water treatment plants use a combination of coagulation, sedimentation, filtration and disinfection to provide clean, safe drinking water to the public. Coagulation Process Description • The term describes the effect produced when certain chemicals are added to raw water containing slowly settling or non-settling particles • Definition of flash mixing is the addition of coagulants to raw November 30, 2012 by admin 2 Comments. What is the dose? In order to enhance flocculation, mineral (activated silica) or natural (starch, alginate) polymers were first used. The flocs that arise due to coagulation are small and can only grow further if the colloidal mixture is slowly stirred. 0.785 × 100ft × 100ft × 30ft × 7.48 Gal/ft3 = 1,761,540 gallons, Feed Rate = 50 × 1.76 × 8.34 = 733.92 pounds/day. The flash mix process only lasts several seconds as the coagulant rapidly mixes and reacts with the raw untreated water. For example, a large rain event has changed the influent turbidity entering the treatment plant. Flocculation or gentle agitation results from velocity differences or gradients in the coagulated water, which causes the fine moving, destabilized particles to come into contact and become large, readily settleable flocs. 0000003306 00000 n We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. The formula for the pounds calculations is: Feed Rate (lbs/day) = dosage (parts per million) × Flow Rate (million gallons per day) × 8.34 lbs/gal. Individual filter efficiency is also closely monitored. Important things to consider when choosing a polymer: Like many processes in water treatment, the theory of coagulation is very complex. The three most common coagulants used in water treatment are Aluminum Sulfate (Alum), Ferric Sulfate, and Ferric Chloride. Round to the nearest tenth or hundredth place to get the most accurate answer. Coagulation and flocculation separates the dissolved and suspended particles from the water by application of chemicals. Flocculation, in physical chemistry, separation of solid particles from a liquid to form loose aggregations or soft flakes. Because coagulation reactions are rapid, detention time for flash mixers is measured in seconds, whereas the detention time for flocculation basins is generally between 5 and 30 minutes. Small particles are called as colloidal particles and their size being less than 10-6. Coagulation and flocculation are used to separate the suspended solids portion from the water. Large, heavy particles settle out readily, but smaller and lighter particles settle very slowly or in some cases do not settle at all. Flocculation or gentle agitation results from velocity differences or gradients in the coagulated water, which causes the fine moving, destabilized particles to come into contact and become large, readily settleable flocs. There is no widespread standard for choosing a polymer. Primary coagulant aids used in the treatment process are ___________. Coagulation is a chemical process that involves neutralization of charge whereas flocculation is a physical process and does not involve neutralization of charge. A water tank that is 30 ft high and 100 f in diameter must be dosed at 50 ppm for disinfection. Electricity is the behavior of negatively and positively charged particles due to their attraction and repulsion. Coagulation & Flocculation in Wastewater Treatment ¾The same aluminum and iron salts are used in wastewater ¾Wastewater requires higher dosages (≥300 mg/l) and coagulates faster than surface water ¾Beside coagulation, lime and iron salts remove phosphorous ¾Coagulant aids include polyelectrolytes, addition of turbidity and lime addition 0000022144 00000 n Coagulation and flocculation occur in successive steps intended to overcome the forces stabilizing the suspended particles, allowing particle collision and growth of floc. How many pounds of 65% calcium hypochlorite must be added to dose the tank? Thus, in terms of water treatment, both can be differentiated easily. How many pounds of Ferric Chloride does the plant use in a day? Coagulation is a process used to neutralise charges and form a gelatinous mass to trap (or bridge) particles thus forming a mass large enough to settle or be trapped in the filter. 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