Perfection in Backwashing of Rapid Sand Filter to Augment the Performance of Sand Filter System

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INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616

Perfection In Backwashing Of Rapid Sand Filter To Augment The Performance Of Sand Filter System.

Rajvardhan Patil, Mukund Chougale

Abstract : Back washing is putting it simply; backwashing is cleaning the filter by reversing the flow of water to remove any debris, build up, and contaminants. For the backwashing of rapid sand filter about 5 % of clean water requires and frequent backwashing (24 – 72 hr) will consume more amount of water for the back washing purpose. To minimize the amount of water require for the backwashing system, to improve the structure of rapid sand filter for the high efficient back washing purpose, to improve backwashing technique to consume less time and efficient backwashing system. This project deals with the modified structure and modified technique of backwashing. Here I am going to use the combine water and air filtration technique for backwashing system, this will results to minimize the required water for backwashing. In this project comparative analysis has been conducted by performing the experimental setup for the conventional and modified rapid sand filter system.

Keywords: Rapid sand Filter, Back wash, Gavity Filters, Graded Gravel, filtration,Efficiency. ————————————————————

1. INTRODUCTION solids following occupation and sedimentation to produce Filtration is one of the most important & essential process of low-turbidity. Rapid sand filters also actively remove water treatment. In this process, water allows passing pathogenic cysts such as Cryptosporidium. Rapid sand through sand filter media and then collects in the storage filters are run in the forward direction to remove solids from tank followed by disinfection process. This process helps to the inert water, and must be utilized and backwashed for remove impurities present in the water like suspended cleaning once the bed is fully loaded. One reason rapid colloidal particles which don’t trapped in the sedimentation sand alteration (as practiced in industrialized countries) is process. At certain interval of time, sand pores may get difficult to implement in resource-poor communities is that clogged due to fine colloidal particles and decreases the high own rates are necessary to backwash filters. efficiency of filter bed. And hence it is needed to remove these fine particles from the pores of the sand. The well- The Importance of Cleaning Rapid Gravity Filters Properly known process for removal of these fine particles is filter The cleaning of Rapid sand filters used in the water industry backwashing. Filter backwash is the process in which about has long been a poorly understood process. In potable 5% of treated water is kept aside for backwashing. This water treatment, rapid gravity filters (RGFs) have been amount of treated water is then allowed to flow through the used as a final polishing stage after coagulation and bed in reverse direction i.e. upward flow. The duration sedimentation, or as a roughing stage, for preliminary required for backwashing with treated water is 7 to 10 particle removal prior to sand filtration. These filters require minutes with additional flow of air. Air helps to make sand cleaning either when the solids captured in the filter results free from fine clogged particles. This process is carried out in decrease in driving head, or when the filter quality starts when the head loss is more and efficiency becomes less. In to deteriorate. rainy season backwashing is to be carried out frequently because turbidity in surface water is more in those days. Objectives Usually, backwash water discharges into a natural stream Our objective is to achieve improved quality of filtration. We by most of the WTPs. In this study, an approach is done are interested in preparing alternative to the conventional towards the recirculation and reuse of backwash water. filter design so that it can remove disadvantages of Backwashing is an essential process in the effective commonly used RSF in more efficient and economical way. operation of rapid gravity filters. Few models have This project leads the below objectives – attempted to describe the backwash process in terms of operational requirements (volume of deposit to be removed, To suggest more efficient filter design. time required to remove it), but mainly focus on the hydraulics of backwashing or backwashing regimes for To remove turbidity effectively. optimum deposit. Based on a fluidizing water wash, the backwash process is modelled in two parts. Part I of the To increase filtration rate and run time. model develops expressions describing the volume of deposit detached into suspension at any time during the To reduce backwashing requirement. backwash. Part 2 models the change in Concentration experienced in the bed during the backwash. Using the To provide economical method for purification output of part I to determine the rate of change of of water. concentration generated within the bed. Initial conditions prior to backwashing are determined from a suitable Testing of model and comparative filtration model. Rapid sand filters are important in surface experimental analysis for the time and water water treatment because they remove residual suspended requirement of backwashing system.

far greater reliance is placed on disinfection to inactivate Limitations of Study bacteria. It is also worth noting that rapid sand filters are not I am going to compare the modified and conventional model effective in removing viruses. Slow sand filters operate at in terms of efficiency, time required for the back washing slow flow rates, 0.1 - 0.3 metres per hour. The top layers of system and water requirement for the backwashing system. the sand become biologically active by the establishment of The Propose model is a combination of air and water a microbial community on the top layer of the sand combine effect of backwashing to reduce the time of substrate. This means that efficient pre-treatment is backwashing and reduces the amount of water required for required to ensure that the filters do not become the backwashing system but, this system when overloaded. Slow sand filters can cope with shock implemented at an actual sight then, system is quite turgidities of up to 50 NTU, but only for very short period of complex to implement at a large level. time before they block. The sand used in slow sand filters is fine, thus high turbidities cause the bed to block rapidly and Slow Sand filtration necessitates more frequent cleaning and therefore greater Sand filtration can be either rapid or slow. The difference time out of action. Nevertheless, slow sand filters are still between the two is not a simple matter of the speed of used in London and were relatively common in filtration, but in the underlying concept of the treatment WesternEurope until comparatively recently and are still process. Slow sand filtration is essentially a biological common elsewhere in the world. The move away from slow process whereas rapid sand filtration is a physical treatment sand filtration has largely been a function of rising land process. Slow sand filters have an advantage over rapid prices and labour costs which increased the cost of slow sand filters in that they produce microbiologically "clean" sand filter produced water, where this is not the case, slow water which should not require disinfection to inactivate any sand filters still represent a cost-effective method of water bacteria, although the addition of a disinfectant to provide a treatment. residual for the distribution system is still advisable. However, because of their slow flow rate, slow sand filters What Is Rapid Sand Filter require large tracts of land if they are to supply large Rapid sand filtration is an integral part of a particular water populations and can be relatively labour intensive to treatment procedure and cannot produce drinking-water operate and maintain.. However, rapid sand filters do not without precedent and subsequent treatment steps. produce water of the same quality as slow sand filters and a

Fig. 1 :- Rapid Sand Filter [12]

Rapid sand filters work at much higher rates of flow (up to inactivated. Rapid sand filters require frequent cleaning 20 meters per hour) and essentially rely on physical (daily or twice daily) which is achieved through removal of suspended solids, including any flocs carried backwashing filters with clean water to re-suspend the over from the settlers. Although rapid sand filters achieve sediment. Cleaning takes relatively little time and the filters some reduction in microbial populations in water as it can be put back into operation immediately. Rapid sand removes particles to which bacteria are attached, it is not a filters are far smaller than slow sand filters and are biological treatment and the use of a terminal disinfectant is commonly employed in batteries. The rapid flow rate vital to ensure that bacteria in the water have been through these filters means that demand can be more 6766 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616 easily met from smaller plants. With the small land requirement, several rapid sand filters can be The Figure 1. shows a typical rapid sand filter water accommodated in small area and thus it is easy to maintain treatment with components. The filter is contained within a capacity to meet demand when filters are being cleaned. filter box, usually made of concrete. Inside the filter box are layers of filter media and gravel. Below the gravel, a network of pipes makes up the under-drain system which Rapid Sand Filter Consist Of Following Parameters collects the filtered water and evenly distributes the The major parts of a gravity rapid sand filter are: backwash water. Washwater troughs help distribute the in- 1. Filter tank or filter box, fluent water and are also used in collecting the dirty washed 2. Filter media, water during backwashing. 3. Gravel support, In addition to the components mentioned above, most rapid 4. Under drain system, and sand filters contain a flow controller, or filter control system, 5. Wash water troughs which regulates flow rates of water through the filter. Other 6. Feeding tanks, parts, such as valves, a loss of head gauge, surface 7. Constant head tank, washers, and a backwash pump, are used while cleaning 8. Feeding pump, the filter. 9. Filtration column

Fig.2 Filtration

Operation of a Rapid sand filter during water filtration is from a central pipe gallery or from a inlet channel. The sizes similar to operation of a slow sand filter. The influent water of the filters vary according to the quantity to be treated. flows down through the sand and support gravel and is The number of filters is selected to minimize the effect of collected by the under drain system is shown in the above removing the filter from service for washing on remaining Figure. However, the influent water in a rapid sand filter is filters. Water treatment filter bed sizes vary from 25 to 100 already relatively clear due to coagulation, flocculation and m2 with lengths in the range of 4 to12 m and widths in the clarification, so RSFs operate much more quickly than range of 2.5 to 8 m and length to breadth ratio of 1.25 to SSFs. The rate of filtration varies from 80 to 120 Lpmin/ m2 1.33. The wash water collection channel is located on one (4800 to 7200 Lph/ m2) of filter bed area or 4.8 to 7.2 m/ h. side along the length of the filter. Filter beds of twice this The average rate of filtration for design purpose may be size can be constructed as two identical beds separated by assumed as 100 Lpmin/ m2 filter area or (6 m/h the wash water collection channel, thus limiting the length of travel of feed water to 5 m, a minimum overall depth of Water Filter Tank 2.6 m including a free board of 0.5 m is adopted. Fig 3. The filter tank is generally constructed of concrete and is shows the cut section of RSF box showing the under most often rectangular. Filters in large plants are usually drainage system, gravel, sand media and wash water constructed next to each other in a row, allowing the piping gutters. from the clarifier basins to feed the water treatments filter

Fig.3 Conventional RSF

Fig. 3d view of Conventional RSF

Filter media

Fig. Filter media filters. This larger sand has larger pores which do not fill as The filter media is the important component of the water quickly with particles removed from the water. Coarse sand treatments filter which actually removes the particles from also costs less and is more readily available than the finer the water being treated. Water Treatment filter media is sand used in slow sand filtration. The filter sand used in most commonly sand, though other types of media can be rapid sand filters is prepared from stock sand specifically for used, usually in combination with sand. The sand used in the purpose. rapid sand filters is coarser than the sand used in slow sand

Graded Gravel

Fig. Graded Gravel

The water filter gravel at the bottom of the water filter bed is Under-drainage System for Rapid Sand Filters not part of the filter media and it is merely providing a The under-drainage system of the water filter is intended to support for media above the under drains and allowing an collect the filtered water and to distribute the wash water even distribution of flow of water across the filter bed during during backwashing in such a fashion that all portions of the filtering and backwashing. The gravel also prevents the bed may perform nearly the same amount of work and filter sand from being lost during the operation. The filter when washed receive nearly the same amount of cleaning. gravel is usually graded of size from 2.5 to 50 mm (largest Since the rate of wash water flow is several times higher size being at the bottom) in four to five layers to total than the rate of filtration, the former is the governing factor thickness of 45 to 50 cm, depending on the type of under in the hydraulic design of filters and under drainage system, drain system used. In case the under drainage system with which are cleaned by backwashing. The most common type pourous bottom or false floor no gravel base is required. of under-drain is a central manifold with laterals either The filter gravel shall be classified by sieves into four or perforated on the bottom or having umbrella type strainers more size grades, sieves being placed with the coarsest on on top. Other types such as wheeler bottom, a false bottom top and the finest at the bottom. with strainers spaced at regular intervals or a porous plate floor supported on concrete pillars are all satisfactory when properly designed and constructed.

Wash water Troughs

Fig. Wash water Troughs

Wash-water troughs placed above the filter media collect head is maintained across the entire filter. The troughs may the backwash water and carry it to the drain system. Proper be made with the same cross-section throughout its length placement of these troughs is very important to ensure that or it might be constructed with varying cross-section the filter media is not carried into the troughs during the increasing in size towards the outlet end. backwash operation and removed from the filter. The upper edge of the wash water trough should be placed sufficiently Backwashing nearer to the surface of sand so that a large quantity of dirty Proper backwashing for cleaning the water treatment filter water is not left above the filter sand after completion of is a very important step in the operation of a water filter. If washing. At the same time, the top of the wash-water the filter is not backwashed periodically, it will eventually trough should be placed sufficiently high above the surface develop additional operational problems. If a filter is to of the sand so that the sand will not be washed into the operate efficiently during a filter run it must be cleaned gutter. Width of the filter bed must be equally divided by the regularly at every 24 to 48 hours. Treated water from troughs so that each trough covers an equal area of the storage is used for the backwashing. This treated water is filter. Maximum clear spacing between the troughs may be generally taken from elevated storage tanks or pumped in 180 cm. The horizontal travel of wash-water to trough directly from the clear water drain by passing in the reverse should not be more than 90 cm. All the wash water troughs direction from under drains to the media. The below Figure must be installed at the same elevation so that they remove shows the flow pattern during the backwashing the backwashed water evenly from the filter so that an even

Flow Pattern During backwashing

During filtration, the grains of water filter media become adhering floc and, the rising wash water carries the material coated with the floes, which plug the voids between the and discharge into the gutters. The backwash flow rate has filter grains, making the filter difficult to clean. Backwash to be great enough to expand and agitate the filter media should, therefore, be arranged at such a pressure that sand and suspend the floes in the water for removal. On the bed should expand to about 130 to 150% of its undisturbed other hand an unduly high rate of flow will cause more volume so as to dislodge the deposited floes from the filter expansion than needed, so that the sand grains will be media during the backwash. Washing causes the sand separated further and scrubbing action will be decreased grains to impinge on one another and thus dislodging 6770 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616 and the media will be washed from the filter into the troughs system placed between the gravel and the sand layer. and out of the filter. Though the former results in better washing, the gravel is likely to be disturbed. The cleaning of water treatment filter Water filters with air agitation followed by backwash is a very efficient Should be backwashed until the backwash water is clean, method but requires the installation of a large air blower to For high rate back wash, the pressure in the under drainage produce the air. The normal design of backwashing system should be 6 to 8 m with wash water requirement employing conjunctive air and water wash, air will be being 650 to 850 Lpm/ m2 of filter (40 – 50 m/hr) for a applied at 700 to 850 Lpm/ m2 of filter area (45 – 50 m/hr) duration of 6 to 10 minutes. and water at 200 to 250 Lpm/ m2 of filter area (12-15 m/hr).

Air Wash System Surface Washing In most cases the filter backwash rate will not be sufficient The upper layer of the water filter bed becomes the dirtiest to break up the mass on the top of the filter. During filter and any inadequate washing will lead to the formation of backwash, the media expands upwards and around the mud balls, cracks and clogged in the water filters. These washing arms only. If air is forced through the under-drains troubles are overcome by adequate surface wash which until the sand is thoroughly agitated, for a period of about can be accomplished by stirring the expanded water five minutes the expansion of sand media and complete treatment filter bed mechanically with jet of water directed removal of the floes could be achieved. In the air wash into the suspended sand. Surface washers spray water system, compressed air is used to secure effective over the sand at the top of the filter breaking down mud- scrubbing action with a smaller volume of wash water. The balls. The below Figure shows the surface wash air may be forced through the under drains before the arrangements, wash-water is introduced or through a separate piping

Fig. Surface Washin

2. MATERIAL AND METHODS

METHODOLOGY The methodology of the project is as explained below,

To Study the Conventional Methods of Rapid Sand Filter Water Purification .

Study the Structure of Rapid Sand Filter

Design the Modified and Conventional Structure Of Rapid Sand Filter

Model Making of Rapid Sand Filter

Comparison of Rapid Sand Filter

Testing & Experimentation of Conventional & Modified Design of Rapid

Sand Filter CONCLUSION

Fig. Flowchart of Methodology

Block diagram

Conceptual

Design of Design of modified Design conventional model model

Manufacturing of Manufacturing of

Experimental Setup

Modified Model Conventional Model

Results Tests

Fig Block Diagram of Rapid Sand Filter

Design of a Conventional Model metres. The water is supplied to the top of the sand-bed The conventional model of Rapid sand filtration is a purely and filtered as it flows through the layers of graded sand physical drinking water purification method. Rapid sand and gravel. A system of perforated pipes on the bottom filters (RSF) provide rapid and efficient removal of relatively drains the chamber (WHO 1996). The filter chamber can be large suspended particles. Two types of RSF are typically constructed as open tanks (rapid gravity filters) or closed used: Rapid Gravity sand filters and Rapid Pressure sand tanks (pressure filters). In the course of these processes, filters. For the provision of safe drinking water, RSFs more and more particles accumulate in the filter medium, require adequate pre-treatment (usually coagulation- increasingly causing clogged filters and decreased flocculation) and post-treatment (usually disinfection with performance. Initial filtering performance can be re- chlorine). Both construction and operation is cost-intensive. achieved through a cleaning of the filter bed. This is usually It is a relatively sophisticated process usually requiring conducted through backwashing: the flow of water is power-operated pumps, regular backwashing or cleaning, reversed, so that treated water flows backwards through the and flow control of the filter outlet. Rapid sand filtration is filter. The sand is re-suspended and the solid matter is common in developed countries for the treatment of large separated in the surface water. Often, air is injected quantities of water where land is a strongly limiting factor, additionally to support the cleaning process (WHO 1996). and where material, skilled labour, and continuous energy supply are available. Construction of conventional rapid sand filter The major parts of a gravity rapid sand filter are: The design procedure of the conventional RSF is as 1. Chamber: Filter tank or filter box follows, 2. Filter media (sand) Conceptual Design: We design the model conceptually with 3. Gravel support the reference of some research papers 4. Under drain system Design of conventional model: With the help of conceptual 5. Wash water troughs design we design the conventional model Material used: Acrylic sheet, SS Net, PVC pipes, etc. The filter chamber is usually made out of reinforced Filter Media: Small and medium size granules (sand) concrete, filled with sand and gravel to the height of 1.5-2 Size of Model: 760mmX430mm

Drawing:

Fig Conventional Model

Conventional rapid sand filter

Let,

Tank volume: 12 meter x 8 meter x 2 meter = 192 m3

Filter tank volume: 1.8 meter x 3.5 meter x 1.5 meter = 9.45 m3

Total filter tank volume: 9.45 x 10 = 94.5 meter3

Fill the back wash water only up to the 0.5 meter height, ones it reaches the level start the aeration supply. Construction of modified RSF

The basic concept of designing the modified model of the rapid sand filter is to use the gravitational force to minimize the amount of water required for the backwashing, to do so, i have made changes in the model an inclined structure compared to the conventional model.

With the help of research papers we design the modified model to compare the results between modified and conventional model.

 Material used: MDF sheet, Foam sheet, SS Net, PVC pipes, M-Seal etc.  Filter Media: Small and medium size granules (sand)  Size of Model: 660mmX500mm

Drawing

Fig Modified model

 Manufacturing of modified model: With the help of design and research papers we manufacture the modified model using Acrylic sheet, SS Net, PVC pipes, etc. For comparing the results between modified and conventional model.

 Tests: We take turbidity test on both conventional and modified model and then compare them with each other.

 Results: We take turbidity test on both conventional and modified model and then compare them with each other and the readings are given below.

 Modified rapid sand filter:

With the same volume: 94.5 m3

The volume is divided in to two parts:

The upper part volume: 90m3

Lower part volume: 15 m3

Total volume: 95 m3 == nearly equal to the conventional tank

3.DESIGN OF MODIFIED RSF CREO offers scalable access to designers who are involved in any par of product development. On the other hand, Software used for design of model: specific CREO applications help developers who are a part Creo is a family or suite of Computer-aided design (CAD) of only one particular process. So CREO can also be apps supporting product design for discrete customized to serve single process and also be used, with manufacturers and is developed by PTC. The suite consists the same efficiency, to serve the needs of the entire of apps, each delivering a distinct set of capabilities for a process. user role within product development. Creo runs on Microsoft Windows and provides apps for 3D 2. Interoperability CAD parametric feature solid modelling, 3D direct modelling, 2D orthographic views, Finite Element Analysis As every CREO application is designed under the same and simulation, schematic design, technical illustrations, roof, the communication between every application is very and viewing and visualization. Creo Elements/Pro and Creo smooth. There are no data lags when any applications is Parametric compete directly with CATIA, Siemens interacting with other application, which saves ample NX/Solid-edge, and Solid-Works. The Creo suite of apps amount of designers time. Hence you can pass the work replaces and supersedes PTC’s products formerly known from one process to other and the same designed will be as Pro/ENGINEER, Co-Create, and Product View. Creo modified to be made perfect. has many different software package solutions and features. Creo Illustrate is a good example. PTC began 2. Combined developing Creo in 2009, and announced it using the code name Project Lightning at Planet-PTC Live, in Las Vegas, Benefits Of Both CAD Modeling Approach in June 2010.[2] In October 2010, PTC unveiled the product Working on CREO means using both the CAD modeling name for Project Lightning to be Creo. PTC released Creo approaches i.e. parametric and direct modeling. Hence you 1.0 in June 2011. achieve two goals with a single software. Designers can enjoy the control provides by parametric modeling on one Features of CREO hand and on the other hand, they can also enjoy the speed CREO works on various stages of product development. and flexibility of direct modeling. Hence CREO is useful in every department of the company. Adding to it, there are four prominent features which defines 4. Operating On Multi-CAD Data the usability of this software. They are CREO can easily work on any CAD data source. Hence designers can save their lot of time and efforts while using 1. Flexibility CREO and operating on various platforms. It also eliminates the minor possibility of human errors while

6775 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616 redesigning the same design. Thus it is helpful for both the increased. CREO certification is one of the best way, where designers and the organization. a professional can demonstrate his expertise on CREO. Moreover CREO certification also helps the professional to grow on both professional and personal level. Hence the Thus CREO is a software solution which helps company to demand for CREO certification has typically increased design products at a comparatively lower cost and in less among the design engineers and other designing time. On account of this usability of CREO the demand for graduates. professionals who can operate on CREO has also

Fig. Modified RSF creo design

When is Backwashing Needed? BACKWASHING OF RAPID SAND FILTER The filter should be backwashed when the following Backwashing of Rapid Sand Filter conditions have been met: For a filter to operate efficiently, it must be cleaned before the next filter run. If the water applied to a The head loss is so high that the filter no longer filter is of very good quality, the filter runs can be produces water at the desired rate; and/or very long. Some filters can operate longer than one Flow starts to break through the filter and the week before needing to be backwashed. However, turbidity in the filter effluent increases; and/or this is not recommended as long filter runs can A filter run reaches a given hour of operation cause the filter media to pack down so that it is difficult to expand the bed during the backwash. Turbidity Test: Treated water from storage is used for the Turbidity is the cloudiness or haziness of a fluid caused by backwash cycle. This treated water is generally large numbers of individual particles that are generally taken from elevated storage tanks or pumped in invisible to the naked eye, similar to smoke in air. The from the clear well. measurement of turbidity is a key test of water quality. The filter backwash rate has to be great enough to Fluids can contain suspended solid matter consisting of expand and agitate the filter media and suspend particles of many different sizes. While some suspended the sand in the water for removal. However, if the material will be large enough and heavy enough to settle filter backwash rate is too high, media will be rapidly to the bottom of the container if a liquid sample is washed from the filter into the troughs and out of left to stand (the settable solids), very small particles will the filter. settle only very slowly or not at all if the sample is regularly

6776 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616 agitated or the particles are colloidal. These small solid particles cause the liquid to appear turbid. First we take the 15 filters of water in a bucket and added TURBIDITY TESTING PROCEDURE equal amount of dirt and dust in to both the water buckets The water testing kit container is used to perform the and inserted that water in to the conventional filter tank and turbidity test. modified filter tank. Then, took the 10 litre water and send it into the sand filter to find the turbidity. We take the five turbidity readings by sending 3 times 10 litre water in the (kit container) Position the sticker slightly off centre. sand filter. Then we collect this filter water and take 3 Fill the jar to the turbidity fill line located on the outside kit turbidity readings on both conventional and modified model label. and then compare them with each other. The process of Hold the Turbidity Chart on the top edge of the jar. find the turbidity in both filtration and backwashing is same Looking down into the jar, compare the appearance of the but their results are different as given below in table. The secchi disk icon in the jar to the chart. Record the result as turbidity of the sample input water after mixing dust Turbidity in NTU. (suspended solids), the turbidity of the water has been tested and the turbidity of the water is as follows, 4. EXPERIMENTATION TURBIDITY READINGS Experimental Testing for filtration I took the 45 litre water for each sample (45 litre for the conventional and 45 litter for the modified model) to make it a diluted water and Following table shows the turbidity readings of the diluted water for modified model and conventional model.

Sr. No. Sample no. Turbidity readings (NTU) 1. Trial 1 (conventional model) 28 2. Trial 2 (modified model) 27

TURBIDITY READINGS OF CONVENTIONAL MODEL Following table shows the turbidity readings of the filtered water getting out of filtered tank for the conventional and modified rapid sand filter, these values are for the 15 litter sample each performed separately to take the individual readings of the rapid sand filter. The turbidity of the water at the end sample are as shown below separately for the conventional model and modified model.

Sr. No. Sample no. Turbidity readings (NTU) 3. Trial 1 8.5 4. Trial 2 7.3 5. Trial 3 6.2

TURBIDITY READINGS OF MODIFIED MODEL

Sr. No. Sample no. Turbidity readings (NTU) 1. Trial 1 8.3 2. Trial 2 7.5 3. Trial 3 6.1

BACKWASHING

The backwashing experimentation procedure is as follows, 7. After the air pressure, start the pump of the water 1. Take the clear water of 20 litter quantity and start and pump will on till the first sample of water the backwashing pump. bucket becomes empty. 2. Provide the air connection (hot air blower) at the 8. Take the sample water of water (end point sample) input side of backwashing. 9. Measure the turbidity of the water 3. The hot air blower air velocity is measured by the 10. Repeat the procedure of hot air blower emission air flow meter (anemometer) which shows the and water pump backwashing till the required readings in meter / sec. turbidity achieved. 4. Initially attach the hot air blower to the input pipe of 11. backwashing for the n number of times unless the backwashing system and start the switch of hot turbidity readings become 3.0 air blower. 12. This procedure verifies that, amount of water 5. Measure the temperature of air and velocity of air required for the backwashing to achieve the same by using digital multi-meter. turbidity. 6. The blower should on for the 10 min initially to get 13. Compare the turbidity of the water and amount of the effective output. water required to achieve the same amount of turbidity.

14. The readings of the turbidity for the conventional and modified filters are as follows,

TURBIDITY READINGS BEFORE BACKWASHING

Sr. No. Sample no. Turbidity readings (NTU) 1. Trial 1 (Conventional) 0.55 2. Trial 2 (modified) 0.65

TURBIDITY READINGS OF CONVENTIONAL MODEL Experimental procedure

Sr. No. Sample no. Turbidity readings (NTU) 3. Trial 1 5.8 4. Trial 2 5.2 5. Trial 3 4.9 6. Trial 4 4.1 7. Trial 5 3.6 8. Trial 6 3.2

TURBIDITY READINGS OF MODIFIED MODEL

 Experimental procedure

Sr. No. Sample no. Turbidity readings (NTU) Trial 1 (hot air) (10 min) 1) 5.6 Trial 1

Trial 2 (hot air) (10 min) 2) 4.5 Trial 2 Trial 3 (hot air) (10 min) 3) 3.8 Trial 3 Trial 4 (hot air) (10 min) 4) 3.5 Trial 4 Trial 5 (10 litter of water ) (hot air) (10 min) 5) 3.1 Trial 5 (10 litter of water )

 The conventional model water required is: 20 litter x 6 trials = 120 litter  The modified model water required is: 20 litter x 4.5 trials = 90 litter It saves the 30 litter of water as compared to the conventional model.

The above charts proves that, the backwashing water saves in modified structure of the rapid sand filter as compared to the conventional model.

HEAD LOSS

Flow rate in project used submersible pump is of 3 litres / min Calculate the Reynolds number to determine whether the flow is laminar or turbulent

3 Q = _____3___ = 0.05 m /s 1 x 60

C = Q A

= 0.05 x 4 π x 0.022

= 159.23 m/s

Re =  c d μ

= 1 x 159.23 x 0.02 1.14 x 10-3

= 189

This is less than 2000, therefore the flow is laminar, and we can use the equation

f = 16 Re

= 16 = 0.036 438

2 hf = 4 f l c 2 g d

= 4 x 0.036 x 1000 x 0.0252 2 x 9.81 x 0.02

= 0.22 m of water

Power to maintain flow = Q γ h

= 5 x 10-5 x (1000 x 9.81) X 0.22

= 0.018 W

Advantages Rapid sand filtration requires very complex technical installations, highly skilled workers for construction and Much higher flow rate than a slow sand filter; about 150 to operation as well as large energy inputs. Unless pre- 200 million gallons of water per acre per day, treatment and disinfection is applied, the filtered water is not safe for drinking. Its application is hence reserved for  Requires relatively small land area. industrialized countries or urban areas where land is a limiting factor. RSF can provide a very efficient method in  Less sensitive to changes in raw water quality, e.g. larger urban water supply systems if preconditions are met. turbidity. For any other areas, RSFs are usually economically  Requires less quantity of sand. unreasonable.

Limitations Future scope I am going to compare the modified and conventional model in terms of efficiency, time required for the back washing TO find alternate capping media to PVC granules. system and water requirement for the backwashing system. Determining optimal strategies for modifications in The Propose model is a combination of air and water rapid sand filter. combine effect of backwashing to reduce the time of Detail backwash study for capped rapid sand filter backwashing and reduces the amount of water required for the backwashing system but, this system when implemented at an actual sight then, system is quite complex to implement at a large level. 5. RESULTS AND DISCUSSION

Applications The turbidity results are as follows,

TURBIDITY READINGS OF CONVENTIONAL MODEL

Sr. No. Sample no. Turbidity readings (NTU) 1. Trial 1 5.8

2. Trial 2 5.2 3. Trial 3 4.9 4. Trial 4 4.1 5. Trial 5 3.6 6. Trial 6 3.2

Turbidity readings (NTU) 7

4 Turbidity readings (NTU) 3

0 Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Trial 6

TURBIDITY READINGS OF MODIFIED MODEL

Sr. No. Sample no. Turbidity readings (NTU) 1. Trial 1 5.6 2. Trial 2 4.5 3. Trial 3 3.8 4. Trial 4 3.5 5. Trial 5 (10 litter of water ) 3.1

Turbidity readings (NTU) 6

Turbidity readings (NTU) 2

Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 (10 litter of water )

6. CONCLUSION

Conclusion 2248-9622, Vol. 7, Issue 4, ( Part -1) April 2017, pp.60- The conclusion part contains the effectiveness of 6. results, back washing water requirement, [14] Rapid gravity sand filters, Filtration Separation June economical approach in proportion to the efficiency 2007. approach. [15] Yury Skolubovich, Cleaning and reusing backwash By providing sand 50% of conventional filter, there water of water treatment Plants, IOP Conf. Series: was not disturbance in turbidity removal efficiency; Earth and Environmental Science 90 (2017) 012035. head loss and filter run length was not affected. [16] K. Suda, Development of a tank-submerged type Backwashing was good in modified filter and membrane filtration system, Desalination 119 (1998) backwash water was reduced to 40-55%. 151-158. [17] Hani Mahanna, The impact of using raw water in rapid  The conventional model water required is: 20 litter sand filter backwash, 11 December 2016. ISSN : 2258- x 6 trials = 120 litter 9632, Vol. 7, Issue 4, ( Part -1) April 2016, pp.75-6.  The modified model water required is: 20 litter x 4.5 [18] Ger VOS, Full-scale treatment of filter backwash water trials = 90 litter in one step to drinking water, Desalination 113 (1997)  It saves the 30 litter of water as compared to the 283-284.. conventional model.

The above charts proves that, the backwashing water saves in modified structure of the rapid sand filter as compared to the conventional model.

REFERENCES [1] Waleed M. K. Zahid, Tertiary Filtration Of Wastewater Using Local Sand, 1. King Saud Univ., Vol. 16, Eng. Sei. (1), Pp. 23-36. [2] Afshin Ebrahimi, Dataset On The Cost Estimation For Spent Filter Backwash Water(Sfbw)Treatment, Data In Brief 15(2017)1043–1047. [3] Mokhtar Mahdavi, Dataset On The Spent Filter Back Wash Water Treatment By Sedimentation, Coagulation And Ultra-Filtration, Data In Brief 15(2017) 916–921. [4] J.C.J. Gude, Effect Of Supernatant Water Level On As Removal In Biological Rapid Sand Filters, [5] Reuse Of Filtration Of Back Water Using Ultra Filtration Technology, Case Study: Science Direct Paper. [6] R Addicks, Examining The Backwashing Of Rapid Granular Media Filters, Procledinqs Of Tne Filtration Society, January/February 1991. [7] M. J. Bauer, Enhanced Rapid Gravity Filtration And Dissolved Air Flotation For Pre-Treatment Of River Thames Reservoir Water, War. Sci. Tee/<. Vol. 31, No.2, Pp. 35-42, 1998. [8] M.J. Chipps, Achieving Enhanced Filter Backwashing With Combined Air Scour And Sub-Fluidising Water At Pilot And Operational Scale, @Ancedf Ilterb Ackwash [9] Afshin Ebrahimi, Dataset On The Cost Estimation For Spent Filter Back Wash Water (Sfbw)Treatment, Received 21 August 2017, Data In Brief 15(2017) 716– 725. [10] Zane Satterfield, Filter Backwashing. B.M. Brouckaert, Filter Backwash Options For Rural Treatment Plants, 05 June 2014, Data In Brief 15(2014) 816–825. [11] Carolin S. B., Instrumentation Or Lnvesticlatincal And Optimizing Filter Backwashing, Filtration And Separation, Jan-Feb 1998, Page 69-72. [12] D. Hall, A Mathematical Filter Backwash Model, War. Scl Tech. Vol. 37. No. 12.Pp. 371-379. 1998. [13] Mangesh L. Jibhakate, Reuse & Recirculation of Filter Backwash Water of Water Treatment Water, ISSN :