National Conference on Research Advances in Communication, Computation, Electrical Science andStructures (NCRACCESS-2015) Analysis and Design of Cascade Aerator Construction for Mettur Water Treatment Plant Kokila.K1, R.Divya2 Assistant Professor, Civil Engineering Bharathiyar Institute of Engineering for Women Abstract: Generally water can be treated in treatment plants for removing harmful substances present in it. The treatment process includes pretreatment, aeration, coagulation, flocculation, sedimentation, filtration, fluoridation, conditioning and disinfection. In our project we concentrate on aeration process using cascade aerators. The cascade aerators are efficient in raising dissolved oxygen content of water, CO2 removal and a large contribution occurs to the self-purification of water due to increase in DO, which accelerates the process of decomposition of organic matter. The working stress method approach of design has been used and recommendations of IS 456-2000, IS 875(Part III), IS 1893 (Part I):2002 and SP-16 have been adhered too. Here we analysis and design a Cascade Aerator for Mettur water treatment plant having a height of 21.6m using Staad Pro v8i and Auto Cad 2010 respectively. The elements of the aerator such as top and bottom ring beams, slab, column, plinth beams, footing & foundation are to be designed.M25 and Fe415 have been used to design all the components of the aerator. The typical analysis of a cascade aerator has been performed on the basis of quantity of water intake. I. INTRODUCTION: The main objective of treating water intended for public water supplies is to produce a supply of water that is chemically and bacteriologically safe for human Consumption. The treatment process includes pre-treatment, aeration, coagulation, flocculation, sedimentation, filtration, fluoridation, conditioning and disinfection. In our project we undergo aeration process using cascade aerators. Aeration brings water and air in close contact in order to remove dissolved gases (such as carbon dioxide). It oxidizes dissolved metals such as iron, hydrogen sulfide, and volatile organic chemicals (VOCs). ISSN: 2348 – 8352 Aeration is often the first major process at the t reatment plant. During aeration, constituents are removed or modified before they can interfere with the treatment processes. All aerators are designed to create a greater amount of contact between air and water to enhance the transfer of gases and increase oxidation. This makes the impure source of water in greater rate of purity approximately 60 to 70% .The aeration processes is carried out through various types of aerators. II. TYPES OF AERATORS: Aerators Gravity Mechanical Aerators Fountain Aerators Injection or Diffused Aerators Chemicals removed or oxidized by aeration Constituents commonly affected by aeration are: Volatile organic chemicals, such as benzene (found in gasoline), or trichloroethylene, dichloroethylene, and perchloroethylene (used in dry-cleaning or industrial processes). Ammonia Chlorine Carbon dioxide Hydrogen sulfide Methane Iron and Manganese www.internationaljournalssrg.org Page 42 The aerator should preferably be installed in open air. usually. The oxygen transfer efficiency should be as 2. as they help to break water flow into separate jets. All aerators are designed to create a greater amount of contact between air and water to enhance the transfer of gases and increase oxidation. Operating considerations: Aeration raises the dissolved oxygen content of the water.6 m/s . freezing and algal growth.9 m/s in theCollecting channel 7 CO2 removal 20 . efficiency Cascade Aeration In this method. are simple to be kept clean and can be made of robust and durable materials with a long life. or timber.3 m in each step. due to increase in DO. The air-in-water method creates small bubbles of air that are injected into the water stream. Computation. but not for CO2 removal.internationaljournalssrg. The simplest type of a free fall aerator is known as a Cascade Aerator. The plates can be made of cast iron. for protection against air pollution. the water becomes supersaturated.3. The cascade aerators are efficient in raising dissolved oxygen content of water. it can be installed in a small house having plenty of louvered air inlets. the rate of flow may vary between 20 to 100 m³/h per m length of weir. cascade aerator. Such aerators are widely used as water features. They will take large quantities of water in a comparatively small area at low head. the water is made to fall through certain height (1 to 3m) over a series of steps (3 to 10) with a fall of about 0. or even of glass. Where a stream passes over an artificial or naturally occurring obstacle.40 cm 5 Rise of step 20 . which accelerates the process of decomposition of organic matter. Electrical Science and Structures (NCRACCESS-2015) Design criteria 1 Number of steps 2 Space requirement 3 Head required Typical value 3 to 6 normally (maximum could be More than 10. higher the efficiency) 0.h 0. the efficiency is reduced. each receiving basin should have a pool of water of depth 0. or of RCC.5 kg O2 / kWh.3 to 0.National Conference on Research Advances in Communication. of course.5 m² per 1m³/h water treated. which is removed only in the range of 60 to 70%. To allow entrained air to mix in the water.45% efficiency 8 H2S removal 35%. in fact more the number.org Page 43 . The water-in-air method is designed to produce small drops of water that fall through the air. Weirs and waterfalls of any kind are.0. The structure so formed is known as a free fall Aerator. especially at low discharge rates.0.40 cm 6 Velocity of water 0. If the water is allowed to cling to the steps. Aerators fall into two categories.045 m²/m³. a large contribution occurs to the selfpurification of the river water. In a cascade ISSN: 2348 – 8352 aerator. The space requirement is typically of the order of 0.15 to 0.015 . They either introduce air to water.5 m. or water to air.0 m 4 Tread of step 20 . If too much oxygen is injected into the water.50 . Figure 1 Process of Cascade aerator www. However. Weirs with serrated edges perform better. concrete does not have a definite modulus of elasticity as in steel. In this project. Computation. However nominal shear reinforcement in accordance with the requirements of IS: 456 shall be provided for plain cement concrete structural members. Because of creep and nonlinear stress. It assumes that both concrete and steel acts together and are perfectly elastic at all stages so that the modular ratio ISSN: 2348 – 8352 Method deals only with the elastic behavior of the member.National Conference on Research Advances in Communication. it neither shows its real strength nor gives the true factor of safety of the structure against failure. code of practice (IS: 3370Part-II. The modular ratio itself is an imaginary quantity. General design requirements according to the Indian standards. www. This will automatically take care of failure due to cracking. Electrical Science and Structures (NCRACCESS-2015) Figure 2 Cascade aerator plan layout Cascade aerator typical design criteria: (ratio between module 0f elasticity of concrete and steel) can be used to determine the stresses in steel and concrete. III. Even though the structures designed by this method have been performing their functions satisfactorily for many years. The design moment and shear in the structure are calculated by elastic analysis with the characteristic loads. the construction of cascade aerator for effective treatment of water has been done. But this method forms the part of limit state design for a serviceability condition.org Page 44 . I.internationaljournalssrg. 1965) Plain concrete structures Plain concrete members of reinforced concrete liquid structures may be designed against structural failure by allowing tension in plain concrete as per the permissible limits for tension in bending specified in IS456-2000. SPECIFICATIONS Working stress method This method of design was evolved around in 1990 and was theoretical method accepted by National Codes of practice for design concrete sections. Figure 3 Cascade aerator in Mettur water treatment plant Objective of project The main objective is to produce a supply water that is chemically and bacteriological safe for human consumption.strain relationship. it has three major defects. The stress in concrete and steel in the sections are calculated on the basis of elastic behavior of composite section.S 456 recommended a modulus of elasticity of concrete which varies with the strength of concrete.8(with respect to yield strength) for steel. 1. Scope of project The scope of the study covers the design of cascade aerator for water treatment plant. 2. Mettur using a new logic of increasing the number of steps for effective splitting of Water molecules and by reducing the usage of Alum in Water treatment. It used a factor of about three times with respect to cube strength for concrete and a factor of safety of about 1. 1450 rpm 60 m 348 m/hr. Fe 415 170 N/mm² 200 N/mm² IV.org Page 45 . Electrical Science and Structures (NCRACCESS-2015) Permissible stress in concrete for strength calculation Reinforceme nt Permissible tensile stress in the reinforcement and concrete and the corresponding allowable stress in concrete.3 percent of the cross section shall be provided in each principle direction. The recommendations as regards the provisions of joints and for the suitable sliding layer are complied with. 2 3 4 5 Stresses due to dry shrinkage or temperature change 6 Stresses due to drying shrinkage or temperature change may be ignored provided that adequate precautions are taken to avoid cracking of concrete during the construction period and until the reservoir is put into use. 1450 rpm 9 Nos. Where the calculated shear stresses in concrete above exceeds the permissible values . 60% 75% IV. reinforcement acting in conjunction with diagonal compression in concrete shall be provided to take the whole of the shear. of Trays Speed of water Head Water treatment capacity Purity rate In strength calculation the usual permissible stresses. STRESS DIAGRAMS Permissible stress in steel reinforcement for resistance to cracking When the steel and concrete are assumed to act together for checking the tensile stresses in concrete for avoidance of cracking the tensile stresses in steel is limited by the requirement that the permissible tensile stress in concrete is not to exceed so that tensile stress in steel is equal to product of modular ratio of steel ISSN: 2348 – 8352 Figure 4 Stress contour for “Mx” www.National Conference on Research Advances in Communication. METTUR WATER TREATMEN T PLANT Cascade FROM THIS PROJEC T Cascade 4 Nos. Computation. N O PARAMETE R 1 Type of Aerator No. RESULTANT COMPARISON Fe 500 205 N/mm² 245 N/mm² S. or the reservoir is to be used only for the storage of water or aqueous liquids at or near ambient temperature and the circumstances are such that the concrete will never dry out. in accordance with IS456:2000 is used. 60 m 783 m/hr. Stresses in the reinforcement The following working stresses are adopted Near water face Away from water face Mild steel 100 N/mm² 125 N/mm² A steel reinforcement not less than 0.internationaljournalssrg. 6th Edition. CONCLUSION The Design of Cascade Aerator for Mettur water treatment plant has been done successfully. IS 456-2000 & IS 456-1978 Design aids for Reinforced concreteR. 4. plinth beams.Design aids for RC to IS 456-2000 5. SP-16. From our project it is expected to obtain the water treatment capacity on 783 m/hr& the purity rate in about 75%.C. The elements of the aerator such as top and bottom ring beams.org Page 46 . 6. AWWA ASCE Water Treatment Plant Design. General design requirements according to the Indian standards.S 3373 (Part II. IS 875 (Part -I. editor.6m using Staad Pro v8i and Auto Cad 2010 respectively.K. Electrical Science and Structures (NCRACCESS-2015) Figure 5 Stress contour for “My” of increasing the steps or trays in cascade aerator for decreasing the usage of alum in treatment process. Design of Reinforced concrete structures. slab. K.M25 and Fe415 have been used to design all the components of the aerator.S 496:2000. S. The calculations we have done using working stress method are within safe limits.internationaljournalssrg.National Conference on Research Advances in Communication. At present in Mettur water treatment plant. Arun Kumar Jain. 5. New York: McGraw-Hill. 3. the water treatment capacity is 348 m/hr& the purity rate is about 60%. I.Garg on Types of Aerators-Water supply Engineering. Part-III and Part IV-1967) Figure 6 Deflection diagram V. Dr.C. footing &foundation are designed. In our project we introducing a new logic ISSN: 2348 – 8352 www. AshokKumar Jain. We collected some details from Mettur Water Treatment Plant regarding our project. Designs (Reinforcedconcrete structures). I. analyzed 2. Computation.C. Plain and Reinforced 4. Water Quality & Treatment: A Handbook on Drinking Water. AWWA (2010b). N. Edzwald. Baruth EE (Ed. IS 1893 (Part 1) : 2002-Earthquake Resistant Structures 3. code of practice 1. Dr B.) Mc Graw Hill. Water Treatement.Punmia. column. 7.FahidRabah-Environment Engineering. REFERENCES The Staad 3D model is shown below and 1. 4t Edition. Part-III)-Wind & Seismic Loads 2. Part-II. Here we analyzed and designed a Cascade Aerator for Mettur water treatment plant having a height of 21.Krishnaraju. J.
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