Slow sand filter and rapid sand filter pdf

A slow sand filter ssf is a means of treating water for drinking water purposes and involves filtering water through a bed of media usually sand. Slow sand filtration cdc pdf pdf 2 pages a slow sand filter is a sand filter adapted for household use. Since the slow aand filter was cleaned manually by periodic removal of the dirty surface sand layer, deep penetration and short filter runs could not be permitted. Rapid sand water filter does not use biological filtration and depends primarily on. Rapid and slow sand filtration techniques and their. Apr 18, 2020 compare rapid sand filter and slow sand filter mbbs video edurev is made by best teachers of mbbs. A welldesigned and properly maintained slow sand filter ssf effectively removes turbidity and pathogenic organisms through various biological, physical and chemical processes in a single treatment step. Compare rapid sand filter and slow sand filter mbbs video. Water from a slow sand filter will be relatively safe, certainly much improved over the raw surface water, and will be of better quality than water from this source treated by rapid sand filters. Rapid sand filters these filters use coarser sand than slow sand filters and the effective size of the filter media is usually greater than 0.

Biosand filters and slow sand filters are both sand filters, meaning they use the same sand filtration methods to filter water see page 9 of the biosand filter construction manual for more information about how sand filtration works. Rapid sand filters pertama kali didesign oleh oleh george w. In a slow sand filter, the filter bed is constructed of a medium with high surface area which can be colonized by suppressive microorganisms. The schmutzdecke is formed in the first 1020 days of operation and consists of bacteria, fungi, protozoa, rotifera and a range of aquatic insect larvae. A is total required area for slow sand filter in m2. Item slow sand filter rapid sand filter coagulation not required required. Slow sand filtration oasis filter international ltd. The biosand filter is a slow sand filter that has been modified to serve household needs. This practical guide provides recommended procedures for operating, monitoring, and maintaining all types of filters used for conventional water treatment. Maximum ph reduction was noted with dual media and less by the rapid system, while more turbidity was reduced with the slow sand and less with the dual media filtration system. The slow sand filter is a gravitydriven filtration process ideally suited to smallscale applications and can. This is cost of typical sand filter, excluding labour costs. The flow rates are normally between 4 and 21 mh equating to 400 to 2100 lh per m2 of filter.

This is larger than the sand used in slow rate filtration. Selection of optimum filtration rates for sand filters. Operate the equipment to filter the water leaving the sedimentation tanks. Slow sand filtration relies on both physical and biological activity in controlling plant pathogens. The rapid sand filter or rapid gravity filter is a type of filter used in water purification and is commonly used in municipal drinking water facilities as part of a multiplestage treatment system rapid sand filters were first developed in the 1890s, and improved designs were developed by the 1920s.

Most rapid sand filters contain 2430 inches of sand, but some newer filters are deeper. The first design that was used as a model for the slowsand filter was the ceramic water purifier developed in 1981 by dr. A slow sand filter is comprised of a bed of graded sand which is supported by a layer of gravel. Slow sand filtration is more cost effective than rapid sand filtration for populations up to 30,000 and possibly considerably higher. The rapid sand filter rsf water treatment equipment differs from the slow sand filter water treatment equipment in a variety of ways, the most important of which are the much greater filtration rate and the ability to clean automatically using back washing. This fine media also presents a physical barrier to the passage of spores of plant pathogens. Types of sand filter the use of sand and gravel as filter media for water supplies can me split into three basic filter types. Slow sand filters work through the formation of a gelatinous layer or biofilm called the hypogeal layer or schmutzdecke in the top few millimetres of the fine sand layer. What are the main differences between a biosand filter and.

From experience gained in building slow sand filters, some general guidelines for filter design have been established as follows. Slow sand filtration for water treatment oasis design. Design and construction of a modified rapid sand filter for treatment of raw water. Coarse filtration to remove large particles is the first stage of treatment and can be carried out with a screen filter, a rapidrate sand filter or a slow sand filter. Descriptions of slow sand filtration technology can be found in. Abstract for over 200 years, slow sand filtration ssf has been an effective means of treating water for the control of microbiological contaminants in both small and large community water supplies. Negative and positive controls were run simultaneously and served both slow and rapid sand filters. The filter sand used in rapid sand filters is manufactured specifically for the purpose of water filtration. A welldesigned and properly maintained slow sand filter ssf effectively removes turbidity and. The water should not be too turbid, otherwise the filter will get clogged. Very few disease causing organisms are inactivated. Usa rapid sand filter design inputs design a rapid sand filter to treat q 20000 m3d allowing filtered water for backwashing.

The slow sand filter projects documented on this website have taken place in the pacific northwest area of washington state, usa. The slow sand filter is a gravitydriven filtration process ideally suited to smallscale applications and can be regenerated by simple raking or automatic backflushing. Slow sand filtration was the first type of porous media filtration used in water treatment. Some specialized slow sand filtrationbased systems are available, which will tend to cost more but with other advantages. This process is known for its simplicity and efficiency. From about the 1930s water treatment by coagulation and rapid gravity filtration or pressure filtration tended to replace slow sand filtration in new plants and, in some cases, slow sand filters were replaced by rapid gravity filters. Slow sand filtration sswm find tools for sustainable.

Rapid sand filters are made using graded sand, sometimes with an. An introduction to slow sand filtration world water forum. Coarse filtration to remove large particles is the first stage of treatment and can be carried out with a screen filter, a rapid rate sand filter or a slow sand filter. However, to guarantee pathogenfree water at all times, particularly during the initial ripening period after filter. A skidmounted bank of three highrate rapid sand filters ready for shipment to the field is presented in figure 7. It consists of a tank inside of which lies a bed of sand i. The basic elements of a slow sand filter are described, as are planning, design, and construction aspects, with special emphasis on maintenance. Relatively simple technology no potentially harmful chemicals used, so no risk to. Slow sand filtration water passes slowly downwards ooo ooo ooo oo oo oo o ooo through a bed of fine sand at a steady rate. Economy high cost cheap and economical qty, of sand more less. The difference between rapid sand filtration and slow sand filtration is not just a matter of speed, but lies in the entire concept behind each filtration system. Rapid sand filtration is a physical treatment of water often used in swimming pools and garden ponds, whereas slow sand filtration is used for biological drinking water treatment.

Traditional slow sand filter tssf traditional slow sand filters or slow sand filters are known for their ability to remove very small inorganic and organic, living and dead particulate materials from water. Slow sand filter biological filter elements of a slow sand filter 1. A flow of between 4 21 mh can be expected from a rapid sand filter, which is somewhere between 20 and 50 times faster than the range of slow sand filtration. Pathogens are naturally removed in the top layer where a biological film builds up. Fernando mazariegos of the central american industrial research institute. Pdf slow sand filter for sewage effluent treatmentt. The water quality tests that have been done by epa certified testing.

The comparison of slow sand water treatment filter and rapid sand water treatment filter with reference to design criteria, advantages and disadvantages is summarized in. The first filter project filter one was started in early 2007. Please note that although commonly referred to as the biosand filter external, the biosand filter terminology is trademarked to one particular design, and this page encompasses all. Water discharged at the facility is treated and either reused for truck washing, street cleaning, or other road maintenance operations, or it is discharged from the. As an epigeal biofilm ages, more algae tend to develop and larger.

A slow sand filter treatment served as a nonbackflushed control to the two rapid sand filters and also as its own unique filtration technique. This filter media is confined in a box with openings at both ends allowing water to flow in and out, while operating on a topdown, gravity basis. Design ini banyak digunakan di sistem pengolahan air pemerintah amerika diberbagai tempat sejak kesuksesannya di tahun tersebut, karena design ini tidak membutuhkan tempat yang luas dibandingkan slow sand filter. Slow sand filter technology in everyday life cbse grade. Introduction it is a solidliquid separation process in which the liquid passes through a porous medium to remove as much fine suspended. Design and construction of a modified rapid sand filter. The first modern rapid sand filtration plant was designed and built by george w. Trigger the appropriate controls to supply air and water to the plant.

Apart from desalination and reverse osmosis, slow sand filters are perhaps the most. Including slow sand filters and precoat filtration water operators will find a wealth of handson information on the operation and maintenance of pretreatment, rapidrate granular media filtration, slowsand filtration, and diatomaceousearth filtration systems in this book. The minimum number n of slow sand filtration units required can be determined by. However, such systems lost popularity to rapid sand filters mainly due to smaller land requirements and less sensitivity to water quality variations. Transfer the plant from standby power to the main power supply. During the initial operational period of slow sand filters, the separation of organic matter and other solids generates a layer of.

In a rural area where rio las ceibas is flowing in the region huila in colombia, an. Some cost figures for systems in india and colombia. It is simple in design, construction and operation. Slow sand filtration is a type of centralised or semicentralised water purification system. What is the difference between rapid sand filtration and. Contents theory of filtration, slow sand filter rapid sand, dual multimedia roughing and pressure filtersoperation and design. Water operators will find a wealth of handson information on the operation and maintenance of pretreatment, rapidrate granular media filtration, slowsand filtration, and diatomaceousearth filtration systems in this book. Rapid sand filtration may be differentiated from slow sand filtration in that the sand used is larger than 1mm in diameter, compared to the much finer sand used in slow sand filtration. Under suitable circumstances this type of slow sand filters is a very effective water treatment method purifying the water with both mechanical and biological processes. The smallest particle that can be filtered out by a particular rapid sand filter is. All of the projects are ongoing and will continue as long as the author is able.