0000000016 00000 n rapid sand filtration) to enhance the ability of a treatment process to remove particles. 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 Coagulation is the destabilization of colloidal particles brought about by the addition of a chemical reagent called as coagulant. Coagulation / Flocculation Coagulation and flocculation is a form of water treatment used for the removal of suspended material through sedimentation or filtration. Mechanical flocculators can be installed both horizontally and vertically. In wastewater treatment these clarification aids help with the removal of other contaminants such as oil, phosphate and heavy metals. Filtration cannot occur without proper coagulation and flocculation. 277 0 obj <>stream Coagulation is most effective in the pH range of 5-7 because of the waters ability to react with alkalinity. There is no widespread standard for choosing a polymer. Coagulation and flocculation process in water treatment. 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. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. How many pounds of 65% calcium hypochlorite must be added to dose the tank? Water quality can change frequently and operators must ensure they are on top of changing conditions. Coagulation and flocculation process in water treatment. Coagulation and flocculation are two processes commonly used in water treatment in order to get rid of unwanted suspended material in water. Coagulation and Flocculation in Water and Wastewater Treatment is a readable and useful resource for the water scientist and engineer. The first two steps include the processes of coagulation and flocculation. 0000014191 00000 n This article provides an overview of the processes and looks at the latest thinking. 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. water treatment - coagulation-flocculation general ... Coagulation and flocculation are two processes commonly used in water treatment in order to get rid of unwanted suspended material in water. What was the dose rate? Coagulation is the destabilization of colloidal particles brought about by the addition of a chemical reagent called as coagulant. 0000001599 00000 n The coagulation-flocculation process can be used as a preliminary or intermediary step between other water or wastewater treatment processes like filtration and sedimentation. November 30, 2012 by admin 2 Comments. In this range, the water tends to buffer or stay in the same pH range and will allow the complete mixing of coagulant chemicals. The purpose of flocculation is to ___________. The mechanical wheel can be used to solve a chemical dosage problem by plugging in the given information and then multiplying or dividing as indicated to determine the solution. It’s used in the first stage of solids-liquids separation: settling, flotation or filtration. The coagulation-flocculation process can be used as a preliminary or intermediary step between other water or wastewater treatment processes like filtration and sedimentation. Underdosing coagulants will cause problems with floc formation while overdosing coagulants can cause clogging during the filter process. Flocculents, such as polyelectrolytes (PE), can be added to improve the flocculation … 0000003529 00000 n There are three steps: 1. * Start the equation as you normally would. Wouldn’t it be nice to have a record of what the operators did three years ago? A treatment plant has a maximum output of 30 MGD and doses ferric chloride at 75 mg/L. Finally, pumps can be used to push coagulant into water flow. <]>> It is important to note that when using the pounds formula, the water production is always expressed in MGD. Coagulation, Flocculation, & Sedimentation. IWA Publishing, a leading international publisher of water, wastewater and environmental publications, offers a high-quality service in print and digital format. Number of particle collisions to increase floc. The coagulation-flocculation processes facilitate the removal of SS and colloidal particles. 0000003258 00000 n Coagulation is a chemical process that involves neutralization of charge whereas flocculation is a physical process and does not involve neutralization of charge. The addition of chlorine can effect polymer effectiveness, As with any chemical, there is a dosage limit, Humic and fulvic molecules separate better with lower pH. Many water treatment plants use a combination of coagulation, sedimentation, filtration and disinfection to provide clean, safe drinking water to the public. * This sample problem is pretty simple. A: There’s a difference between coagulation and flocculation, and the mechanism that causes particles to aggregate and come together so that they can be filtered or settled. In flocculation one can make a distinction between perikinetic and Electricity is the behavior of negatively and positively charged particles due to their attraction and repulsion. Mixing can be achieved by utilizing hydraulic mixers, mechanical mixing, diffusers, or pumped blenders. The enhanced coagulation process is used to remove natural organic matter by adjusting the pH and coagulant dose to remove the greatest amount of suspended matter during the treatment process. 0 Chemistry of Coagulation and Flocculation; The chemistry of coagulation and flocculation is primarily based on electricity. Coagulation -flocculation is a conventional pre-treatment method (typically in combination with sedimentation] and rapid sand filtration) used to separate the suspended and dissolved compounds (turbidity) from the water in (semi-)centralised drinking water treatment plants. Coagulation and flocculation are often used in combination. Coagulation occurs very quickly in the rapid mix or flash mix process. The two-part process in water treatment involves chemical deactivation and physical removal of pathogenic organisms. x�bb�e`b``Ń3� �� ��� In order to enhance flocculation, mineral (activated silica) or natural (starch, alginate) polymers were first used. Remember, if the chlorine solution is not 100 percent available chlorine you are going to need more to dose properly! 0000003306 00000 n 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. In wastewater treatment these clarification aids help with the removal of other contaminants such as oil, phosphate and heavy metals. Since you are adding a solution of chlorine that is not 100 percent an extra step is needed to solve the problem. The purpose of coagulation is to ___________. Coagulation is a process to neutralize charges and then to This process increases particle sizes which assists in removal during the filter process. Proper water quality tests must be performed by operators to promote the proper addition of coagulant chemicals. They can also be referred to as nonstable solids. Coagulation and flocculation constitute the backbone processes in most water and advanced wastewater treatment plants. The colloidal surfaces are negative thus positively charged metal salts are used as primary coagulants. The efficiency of water treatment plants is determined by the combined effluent turbidity reading. After coagulation the destabilized particles can collide, aggregate so flocs can be formed. Flocculation, in physical chemistry, separation of solid particles from a liquid to form loose aggregations or soft flakes. The particles are then more easily removed in the sedimentation and filtration process. It is important that floc has good size but also density so the floc will not shear during the sedimentation and filtration process. Thus, in terms of water treatment, both can be differentiated easily. Flocculation is commonly confused with coagulation, and the terms are consequently used to some extent interchangeably but they are very different processes. Feed Rate= 15 mg/L × 5 MGD × 8.34 lbs/gal. Coagulation is defined as. A treatment plant uses 300 lbs of alum a day. 0.785 × 100ft × 100ft × 30ft × 7.48 Gal/ft3 = 1,761,540 gallons, Feed Rate = 50 × 1.76 × 8.34 = 733.92 pounds/day. Flocculation and coagulation treatment chemicals are used in effluent wastewater water treatment processes for solids removal, water clarification, lime softening, sludge thickening, and solids dewatering. Coagulation aids assist in the building of settable floc. The plant output is 2,500,000 gallons a day. 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 NOM - = natural organic matter - particulate and dissolved organic mater First published in 1993, Coagulation and Flocculation is a practical reference for the researchers in the field of the stabilization and destabilization of fine solid dispersions. Many water treatment plants use a combination of coagulation, sedimentation, filtration and disinfection to provide clean, safe drinking water to the public. If step one is incomplete, the following step will be unsuccessful. 0000002691 00000 n Two steps typically are employed: coagulation and flocculation. 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 are designed to: - remove infectious agents - remove toxic compounds - remove precursors to the formation of disinfection byproducts - make water palatable. However, they can be commonly adopted for de-stabilizing any suspension system. ��K��P)�}��jehH�[�fF�X�D��E�%�q���X��u�h�D4�F4��Q$z�^��"E�e�AE�ED���'bV. Next, you will need to make an adjustment based on chlorine strength. Because of this consideration, jar testing and plant monitoring is all the more critical. xref These flocculates are easily disrupted, being held together only by a force analogous to the surface tension of a liquid. Flocculation is used to enhance ___________. In this process, colloidal particles are destabilized to gather all the suspended material together. During abnormal conditions, it is important for operators to take notes and inform senior operators and/or a supervisor. The process of aggregation of many small particles into a few large ones. For example, a problem may ask what the chlorine production is for a water treatment plant that produces 1,000,000 gallons a day. Mixing can occur in a basin, channel, or pipeline. Particles in water, such as clay, usually have a negative charge. Small particles are called as colloidal particles and their size being less than 10-6. Flocculation is commonly confused with coagulation, and the terms are consequently used to some extent interchangeably but they are very different processes. 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. endstream endobj 276 0 obj <>/Size 253/Type/XRef>>stream Important things to consider when choosing a polymer: Like many processes in water treatment, the theory of coagulation is very complex. Round to the nearest tenth or hundredth place to get the most accurate answer. The process of aggregation of many small particles into a few large ones. Flocculation, in physical chemistry, separation of solid particles from a liquid to form loose aggregations or soft flakes. A similar event happened three years prior and the influent turbidity is very similar to the ones operators are seeing currently. Coagulation Chemical treatment typically is applied prior to sedimentation and filtration to enhance the ability of a treatment process to remove particles. Different states have chemical approval standards that must be met. startxref The equation used to calculate detention time, if the flow is in gallons per minute, is: Coagulation and Flocculation are designed to: - remove infectious agents - remove toxic compounds - remove precursors to the formation of disinfection byproducts - make water palatable. Flocculation is a physical process in which the fine solids produced by coagulation are brought together into … and accordingly will see improvements in treatment such as: One of the most important calculations an operator will use is the “Pounds Formula.” The pounds formula can be used to solve water math problems including milligrams per liter to pounds per day, feed rate, chlorine dosage, percent strength, and dilution calculations. hތX T��O3C]b�8(3���j�[Ul�^QA�E���B��Bv��5@�W�D�}���.u��jmkZ_�C/��M���;��w&�ffr�������lF��b��Ϋ֮Y1�Ce�"|����>�7�{�X�xF����Fۡ�(�7�ov�>�s\�$�wd��F�'� �R)����yN��̲��F'��4wh�?4�wr�_��u��� ݫ�o� 0000022144 00000 n ��W�(B�+�̒+��A�J�"(J��V��+|�jUh���|�2$T�n���TQ�5�{]fɽB|��^QrAB��O)Ȩ)C�� If the raw water has a low pH, agents such as soda ash can be added to increase the pH. Primary coagulant aids used in the treatment process are ___________. Humic and fulvic acids are organic acids commonly found in raw water sources, Sulfuric Acid addition before coagulant is added preconditions organic matter. During coagulation, coagulant is added to clump the particles together. How many pounds of chlorine will the operator use? Insoluble is something that will not dissolve. This process, known as flocculation, therefore requires slow mixing and a prolonged retention time. If the floc is not formed properly, then operators cannot effectively remove pathogens from the treated water. The physical removal of pathogens is accomplished in several steps. In this process, colloidal particles are destabilized to gather all the suspended material together. first process in drinking water treatment, coagulation, is to destabilize the particles and allow them the potential to collide and stick together. 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. 0000015147 00000 n Have questions or comments? Coagulation and flocculation water treatment chemicals are used to remove iron, suspended solids, organic color, and hardness from influent water. The measure of alkalinity is the amount of acid that would have to be added to water to lower the pH to 4.5 and there is where the confusion arises. The first step destabilizes the particle’s charges. 0000014904 00000 n The first two steps include the processes of coagulation and flocculation. After coagulation the destabilized particles can collide, aggregate so flocs can be formed. The coagulation and flocculation process requires a great amount of attention to detail along the way. This is done with the help of a coagulant. This may be due to the fact that monitoring at these points is typically not a regulatory requirement. This enables their removal by sedi-mentation, dissolved air flotation or filtration. The chemicals are added together and the process occurs within seconds. 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. W+���!ޡ��P��Z��|EP�|�u�p�&E�B����U��{��*/E��*P�+wQ(}A{*?�J�� Suspended particles vary in source, charge, particle size, shape, and density. EX: A water treatment operator must super chlorinate a 650,000-gallon tank at 50 ppm. * You must divide 650,000 by one million to get .65 to solve the equation. 0000002076 00000 n Coagulation is a process of making colloidal matter dispersed/suspended in a liquid to join in a coherent mass. The speed of the mixing is decreased in each compartment to prevent the particles from breaking apart as they become larger. Colloidal 0000019450 00000 n This phenomenon will be discussed in further detail in Chapter 6. Not all supply water is created equal. The function of a flocculation basin is to ___________. An operator cannot just set a dose and “hope” everything works out. These flocculates are easily disrupted, being held together only by a force analogous to the surface tension of a liquid. Coagulation is a process of making colloidal matter dispersed/suspended in a liquid to join in a coherent mass. The most commonly used primary coagulant in water treatment is Alum because of its wide availability and affordability. Coagulation and flocculation Suspended particles cannot be removed completely by plain settling. Once the waste particles have clumped together using coagulation, flocculating agents in wastewater treatment are used to remove the clumps. Every single water source has a different chemistry and jar tests must be performed to see what polymer works best with the specific source water. 0000015069 00000 n Coagulation and Flocculation Coagulation and flocculationconsist of adding a floc-forming chemical reagent to a water to enmesh or combine with nonsettleable colloidal solids and slow-settling suspended solids to produce a rapid-settling floc. The horizontal type utilizes paddle-style mixers while the vertical style mixers can include paddle, turbine, and propeller style mixers. What is Coagulation and Flocculation? Coagulation is a process to neutralize charges and then to 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. What is the dose? Coagulation treatment neutralizes the negative electrical charge on particles, which destabilizes the forces keeping colloids apart. 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A laboratory procedure that finds the best coagulant dose is determined by a chemical reagent called colloidal! Channel, or hydroxide remember, if the raw water has a low pH, agents such oil... To destabilize the particles from a liquid it is important to note that when using pounds. Some cases, the water will react with the alkalinity in the sedimentation and filtration process portion from treated! Compression, adsorption and charge neutralization, sweep flocculation, in terms of water coagulating... Solids-Liquids separation: settling, flotation or filtration effluent turbidity reading mixing can in... The latest thinking on water quality conditions and growth of floc was largely taken from reference1.Coagulation and.! Finds the best coagulant dose based on chlorine strength is typically not a regulatory requirement mixers require the greatest of! From ancient times the first two steps typically are employed: coagulation and flocculation particles have clumped using.