A sand filter can be placed in various phases of water management - as a pre-treatment, as side-stream filtration and as a polishing filter. The biosand filter (BSF) is an adaptation of the traditional slow sand filter, which has been used for community water treatment for almost 200 hundred years. reaches a certain level in the tank or in timed doses. NSFC. Sand filters remove many pathogens, such as viruses and harmful
Set outfall underdrain pipe 2' above stream invert and
Soil boring observations reveal that
Recirculating sand filters reduce odors by ensuring an adequate
Sand trap may be designed with or without top slab it depends on the situations if some traffic is to be passed over the sand trap then top slab is required to be constructed over the sand trap here in these examples we are not considering the top slab of the sand trap. Step 4. They are used most often for sources generating up to 120,000
Construction of the sand filter units themselves usually is
Compute volume within practice: Volume within filter bed (V f): V f = A f (d f) (n); n = 0.4 for sand (Porosity) V f = (473 sq ft) (1.5') (0.4) = 284 cubic feet Slow sand filter (SSF) characterized by slow flow rate (0.1–0.2m3/h) and a biological layer over filter bed called schmutzdecke is fairly efficient in removal of coliform microorganisms such as Giardia, Cryptosporidium, Salmonella, Escherichia coli, total coliform and fecal coliform, fecal streptococci, bacteriophage, and MS2 virus from wastewater. about sand filters or are interested in utilizing one, contact your local health
Loading rates determine the amount of maintenance needed and how long the system will last. If covered, it should be vented to maintain aerobic
A sand filter can be placed in various phases of water management - as a pre-treatment, as side-stream filtration and as a polishing filter. inches, but a few additional inches improves overall performance, pathogen
the filter in one day. recirculation tank. media bed. A sand filter often provides an effluent with potential for re-use. Exhibit 4 - II (page 4-6 of TR-55), q u = 900 csm/in, and therefore qp = (900 csm/in) (0.62") (3.0
expensive or needs to be hauled a long distance, costs are much
), = 1000/[10+5*1.0+10*0.62-10(0.622+1.25*0.62*1.0)½]. Most sand filters are designed
wastewater to flow. How Well Do Sand Filters Perform?, Sand Filters Require Maintenance, How Much Do Sand Filters Cost?, Information. Introduction to Filtration Purpose The purpose of filtration is to remove suspended particles from water by passing the water through a medium such as sand. Uneven
for extended aeration package plants and other treatment options. this time and the finer gravel is placed under the coarser gravel closest to the
Field effectiveness studies have documented E. coliremoval rates of 80-98%. Exact costs for sand filter construction, operation, and
The filter media is then placed
Maximum required area per filter – 50 m 2.. Design filter size and number of filters required. attract positively charged waste particles and bond with them through a process
In turn,
the settling chamber, using 4.33' as the design height; (2727 cubic ft)/4.33' = 630 sq ft; 630/15.5' yields a length of 40.6 feet (say 40'), new sedimentation chamber dimensions are 15.5' by 40'. themselves, cannot be used. tanks are the most common and usually the least expensive pretreatment method
Bottomless ISFs The bottomless ISF has no impermeable liner and does not discharge to a drainfield, but rather directly to the soil below the sand. be weeded regularly and may develop algal mats that need to be
Some
The ecosystem in a slow sand filter includes bacteria, protozoa such as rhizopods and ciliates, rotifers, copepods, and aquatic worms. Use a concrete weir to pass the
Doses should be spaced
ten-year flow (14.0 cfs) into a grassed overflow channel using the Weir equation. The exact dimensions will be sized later, but the volume stored within the sediment chamber
Our unique design of Pressure Sand filter ensures the maximum utilization of the surface area, lesser pressure drop across the filter bed and effective removal of the impurities. The final sand filter effluent also is of higher
The first two require the use of flocculant chemicals to work effectively while slow sand filters can produce very high quality water with pathogens removal from 90% to >99%, taste and odour without the need for chemical aids. (November, 1997), Health Departments: If you would like more information
is relatively consistent and they have low operation and maintenance requirements. Classes are available for GATE. From
the sand filter bed allows effluent to be pumped to a drainfield at any location or elevation. The filter can then be loaded below the insulating sheet of
The standing water depth over filter varies between 1.0 and 2.0 m. Another cold-weather operating strategy entails raking the
A municipality wishes to install rapid sand filters. media) are contained in a liner made of concrete, plastic, or other impermeable
He discovered that biological layer living in the sand could survive for extended periods of time if the water level is no more than 5 cm above the bio-film. The Manual of Design for Slow Sand Filtration provides state-of-the-art information on the feasibility of using this technology and on design, construction, and operations to best achieve desired production and performance. recirculating sand filters are summarized in the table below. Silica sand and anthracite are among the most common types for solids filtration. Praktisch: Verglichen mit Sand lassen sich die Filter Balls viel leichter hinzufügen oder wechseln. regularly dosed with warm septic tank effluent. Langlebig. system components need to be checked regularly, and screens and filters need to
every type of sand filter system. maintenance depend on the filter design and local costs for labor and materials. Written for civil engineers who are considering slow sand filtration, the manual provides the Pressure sand filter is the first unit process in any treatment. The effective size of each granule of sand … Composition, size, uniformity, and depth of the media all affect
measure of the amount of waste particles suspended in the wastewater. It also is important that wastewater be applied evenly across
Eventually, the biomat becomes clogged, and the top layer of sand
of oxygen microorganisms need to consume and break down organic matter. Wastewater flows by gravity from a septic
Recommended velocity for filtration is 10 m/hr to 30 m/hr. sand filter designs. tank, aerobic unit, or other sedimentation process. piping goes over—not through—the sand filter liner, so the integrity of the liner is protected. filters-are a practical option for treating wastewater from small communities,
removed. Säurebeständigkeit, Alkalibeständigkeit, hohe Temperaturbeständigkeit. Compute WQv peak discharge (qp): Compute modified CN for 1" rainfall (Note: In this example the WQv corresponds to the runoff from a 1"
Common Sand Filter Designs. freezing. Logisticon manufactures both sand and activated carbon filters, in steel, under its own management. Description of Recirculating Sand/Media Filter Septic Systems. also is extremely important that the media be washed. In Stock Free Shipping. DIY-slow sand filters have been used in Afghanistan and other countries to aid the poor. It will remove practically all the turbidity from water, together with virtually all harmful eggs, protozoa, bacteria and viruses without the addition of chemicals and may frequently be constructed largely with local materials. at (888) 398-4636, the U.S. Department of Agriculture at (202) 720-3377, or
portions of the filter bed to rest by switching the sections to be dosed. Particles
frequencies can improve filter performance in low temperatures. Logisticon manufactures standard or client-specific coated steel filter tanks varying from 1.2 to 3.1 metre in diameter for its rental fleet and for specific projects. filter. receiving aerobic unit effluent, because the organic strength of the septic tank
*Catherine Taylor and Joseph Yahner, Agronomy (765) 496-3454,
DynaSand™ is a world-leading continuous sand filter developed by the Axel Johnson Institute in Sweden in the late 1970s. appropriate rate is determined based on the dosing pattern, the size of the
In addition, overall treatment costs should compare favorably with other alternative
TSS are indicators used by regulatory agencies to assess treatment and its
This problem sometimes can be
All wastewater treatment methods that rely on natural processes
offset by adjusting the dosing frequency and the recirculation ratio or by
There are several different sand filter types and designs. that it clogs the filter. are permitted on an experimental basis in Indiana. factored in when evaluating the overall system costs. Because some odor is released when septic tank effluent is dosed
the runoff from small storm events. Characteristics of the media's composition, such as its
dependable high performance often make them an attractive choice. Stormwater Design Example:
called adsorption. Beneath the stone layer is a minimum of 0.75m of filter sand The distance between the pipes are represented by a variable letter “S”. the seasonally high water table is at 13.0 feet. The water enters the top or side of the filter through a multiport or … bottom of recharge filter and water table. Experience has shown proper filter maintenance is necessary for optimal performance so proper user training and follow-u… The total available head is 21.0 - 16.67 or 4.33 feet. Pressure Sand Filter is used for removal of suspended solids & turbidity from Water & Wastewater. Hayward 25 inch Sand Filter (11) $732.99. waste before the fluid infiltrates the soil below the sand filter. Hayward 24 Inch Swim Pro Sand Filter with 6 Way Valve. greater than the recharge requirement of 1,688 cubic feet. In Stock Free Shipping. A drawback to recirculating sand filters is they are more
Regular maintenance of the septic tank is essential to prevent
There are two main types of industrial water filtration systems: tank and membrane. Dunn, Indiana State Department of Health (317) 233-7177. adjustable timing mechanism or a siphon doses the wastewater to the filter in
Logisticon manufactures standard or client-specific coated steel filter tanks varying from 1.2 to 3.1 metre in diameter for its rental fleet and for specific projects. filter from being overloaded or to prevent the filter surface from
appropriate technologies for Indiana. Source: THAMES WATER & UNIVERSITY OF SURREY (2005) The simple design of SSFs makes it easy to use local materials and skills in their construction (HUISMAN 1974). on top of the layer of fine gravel. The organisms living in the filter require a constant supply of oxygen. All calculations and rates are following the Brazilian Standard NBR 12216/92. Ihre Filtrationsergebnisse sind genauer, da sie Partikel im Poolwasser auf eine Größe von nur 1,5 Mikrometer filtern können. that can be operated in parallel or in series, allowing a portion of the filter
"Effective size"
(Tony) Favreau, set out to solve a common problem
Get contact details & address of companies manufacturing and supplying Sand Filters, Industrial Sand Filter … Energy and routine maintenance requirements are more than
Dual‐media filters: two types of media is used usually sand and anthracite 3. Extension Service: Extension service offices can provide
gallons of wastewater per day. institutions, while others are more appropriate for individual homes and small
Bacteria Single-celled microorganisms, typically a few micrometres in length. Too frequent dosing causes similar problems. However, the order is reversed
Calculation for pressure filter design. doses. Another graded layer of gravel is placed on top of the media bed
(2,727 cubic ft)/(15.5' x 28.75') = 6.12' which is larger than the head available (4.33'); increase the size of
There are many possible sand filter system designs. The
filter contains less organic matter and more oxygen than normal septic tank
reducing five-day biochemical oxygen demand (BOD) and total suspended solids
Step 6. to be rested at any time. It features durable corrosion-resistant and easy to operate. = 2.6 cfs. are better suited for small communities, clusters of homes, large businesses, or
Sand filters usually are used as the second step in wastewater
allowable depth (2) (hf) = 4.33', and hf = 2.17'. Effective sizes for sand filter media range from 0.3 mm to 3
The Multigrade Sand Filter is a depth filter that makes use of coarse and fine media mixed together in a fixed proportion. Many larger sand filters are operated in sections to allow
Recommended velocity for filtration is 10 m/hr to 30 m/hr. volume for filter designs. Partially treated wastewater is applied to the filter surface in
The distance between the outside pipe and the edge of the leaching bed is represented by “S” divided by 2. Kann wiederverwendet werden, Schmutz kann gewaschen werden. The system v/as installed in October 1995, and the performance v/as monitored for 15 months. The sand filter effluent drained into the pump vault in the center of the sand filter, which then pressure dosed two shallow soil trenches constructed with chambers. Sand filters are 2 to 4 feet in diameter and look like large balls. In the late 1960s, two engineers with the Illinois Department of
These systems consist of the septic tank, pump chamber, sand filter and drain field. There are many possible sand filter system designs. BOD5 is a measure of the amount
receiving septic tank effluent may need more frequent attention than those
Sand filter units are constructed or assembled onsite by a
which contribute to treatment by consuming organic matter in the wastewater. Low point at stream invert is 12.0'. One disadvantage of sand filters is that they are not very
$439.00. cubic feet) = 5,064 cubic feet. As the water passes through the filter, floc and impurities get stuck in the sand and the clean water goes through. Treatment slows down in cold temperatures, so
requirements. In Stock Pentair 26 Inch Sand Dollar Filter . It uses both physical and biological pathogen control mechanisms. The sand used as filter media in RSF is generally of effective size of 0.4 to 0.7 mm and uniformity coefficient of 1.3 to 1.7. A sand filter often provides an effluent with potential for re-use. A geotextile fabric is placed on top of the entire filter
fields. Tank integrity
systems. to allow the wastewater to flow correctly through it. Recirculating Sand/Media Filters - US EPA Design Information. General maintenance requirements for both single pass and
Slow sand filtration involves allowing irrigation water to slowly pass through a bed of sand or other porous material such as pumice, rockwool, etc for treatment. challenge, they developed the recirculating sand filter, which has since been
This balance between the various life forms and the
During the design and operation of slow sand filters, extra care needs to be taken in order to maintain an active biological population within the sand. wastewater can be flushed through the filter before receiving adequate
See Design Criteria - Filters, From filtration chamber (size to pass 1/3 of WQv peak discharge). stick to grain surfaces or get caught in crevices or voids on grains or in
frequently. The On-Site Project is
A. filters are sometimes used in the pretreatment tank as an additional step to
for cleanliness by a qualified individual before it is used in the
The filter sand used in rapid sand filters is prepared from stock sand specifically for the purpose. They are as follows: Filter: This is what your sand filter does 99% of the time, it filters the swimming pool water. The curve number is calculated based on
the long-run sand filters' low energy costs, lower operating costs, and
needs to be raked or removed as part of regular filter maintenance. $399.00. sand filter performance. 0.8 mm to 3 mm, which is somewhat coarser than sand filter media used in single
insulate them from extreme cold weather, minimize maintenance, and reduce the
when they are properly designed, constructed, and maintained. The sand filter may consist of a large concrete box filled with sand. of filter media. Adjacent creek invert is at 12.0'. Coarse media allows wastewater to pass too quickly through the filter
Sand Filter Layout 1. The sand filter used in this study consistently produced a high quality effluent with low BOD, SS, and ammonia nitrogen (NH4-N). Compute remaining volume for sedimentation chamber (Vs): Vs = Vmin - [ Vf + Vf-temp] or 5,064 - [284 + 2053] = 2,727 cubic feet, compute height in sedimentation chamber (hs): hs = Vs/As. collects in underdrains and a portion of it is directed back to the
recharge. Example of a basic design of rapid sand filtration. to be replenished or replaced. recirculated to the sand filter. This water treatment technology does not require expensive equipment or chemicals (coagulants, polymers, limestone, etc...) and can be used in small communities and villages. Recirculating filters using sand, gravel, or other media provide advanced secondary treatment of settled wastewater or septic tank effluent. Organic loading rate depends on the strength of the wastewater. Their performance
Typically, the volume within the practice can be less than the total water quality volume for filter designs. Don Jones, Agricultural Engineering (765) 494-1178, Purdue University and Alan
As with all sand filters, the depth of the
for additional onsite treatment where septic tank/soil absorption systems have
Appendix I. Sand is used to make up for the inadequate amount of soil at the site. the filter bed-with the finer gravel on top of the coarser gravel to keep the
See Design Criteria - Filters. less land area is needed to treat the same amount of wastewater than with other
commercially in a kit. Filter depth depends on the type of filter and media size, but
higher. Hydraulic loading rates for single pass filters typically range
ensure that no solids carry over to the filter in times of heavy water
Filter is designed based on velocity consideration. There are many possible sand filter system designs. Media should be inspected
Sand
assistance. RAYNED series multi-layer sand filters represent the latest filter technology. Suitable filter media can be purchased from aggregate companies
use. However, chemicals sometimes need to be added to improve the yield of the sand filter. produce 0.62" of runoff. effluent, reducing odors. fine. most common types of sand filters, buried, single pass, and recirculating, are
treatment. Note that runoff will enter
Sand Filter Design Slow sand filtration is a simple and effective technique for purifying surface water. A number of factors must be taken into consideration in order to maximize filter effectiveness. ac/640ac/sq mi.) They are one of the best options
Für alle vorhandenen Sand- / Glasfilteranlagen für Schwimmbäder. A sand filter septic system is a good solution for waste water treatment problems in areas with insufficient soil. Biosand Filter Manual iii Glossary Adsorption When a contaminant attaches itself to the surface of a solid. institutions. institutions, and small residential developments and communities in areas where
This stone will eventually clog without protection from settling
The Six Settings of Sand Filters Sand filters always have a six-port valve with different settings. Dr. Manz of the University of Calgary made several modifications to the traditional slow-sand filter to allow for intermittent flow and point-of-use water treatment. Weirs, moveable gates, and other devices can be used
grains must be relatively uniform in size to prevent clogging. Assume the grain sphericity ф= 0.75 and porosity (ε) = 0.40 for both. physical, biological, and chemical processes. physical and chemical processes that take place in the sand filter results in
Single pass sand filters-often called intermittent sand
See
Sand filters do part of the work to keep a pool clean. effective at removing phosphorus from wastewater. The Davnor BioSand Water Filter; Manual of Design for Slow Sand Filtration, David Hendricks, Amer Water Works Assn (June 1991) Slow Sand Filtration, Huisman L. and Wood, W.E., WHO 1974 Prepared by Colorado State University, CH2M Hill Engineers, Denver (CO) Water Department, Colorado Health Department, Black & Veatch, Dayton & Knight, and RBD Consulting Engineers, June 1991. or other suppliers. Tanks allow
Calculation for pressure filter design. You can purchase classes at a very reasonable price. This is accomplished either by flooding the surface
solids from clogging the filter. National Small Flows Clearinghouse (NSFC): The National
Filtration is used for th… individual system designs. be a problem with sand filters . Slow sand filters on the other hand, should ideally have an effective size of between 0.15 – 0.35mm, and a Uniformity Coefficient of between 1.5 – 3, but preferably less than 2. cost for inspections and maintenance. protozoa feed on the bacteria and help prevent the biomat from becoming so dense
They also can be a good choice for homes, businesses,
Find here Sand Filters, Industrial Sand Filter manufacturers, suppliers & exporters in India. Depending on the system design, sand filters are capable of
10 to 25 years, but eventually need to be replaced. Multimedia filters: three types of media are used usually sand , anthracite , and Garnet Most famous filters inwater treatment are Rapid Sand Filters. Many Factors Affect Sand Filter Performance. The entire filter unit is contained in an impermeable liner. In response to this
Depending on the design, the filter may be situated above ground,
package plants. Single pass filters receiving larger flows usually have two or more beds
Put your sand filter close to the cartridge filter and pump for convenience. After the solids have been removed, a pump equipped with an
Höhere Durchflussrate, bis zu 45%.Die leichten Filterbälle(700g) reduzieren den Filterpumpendruck, dadurch sie Lebensdauer der Filteranlage verlängern. To ensure safety, sand filters serving individual
The wastewater then collects in an underdrain and flows to further
alternative system for wastewater treatment. Oxygen is critical to the biological and chemical treatment processes that take
Biolayer The biological layer formed at the sand-water interface of slow sand filters. System Design Deschutes County recommends a licensed Department of Environmental Quality (DEQ) installer with experience installing sand filters submit the design and hydraulic calculations. surface. discussed. They can remedy an existing malfunctioning system. The filters are filled with sand, which acts as a natural filtering agent. Step 2. Freezing can
and a graded layer of washed gravel or crushed rock are placed at the bottom of
Septic
Intermittent sand filters receive and treat wastewater in
However, further treatment, such as passage through a soil absorption
treatment. Subtract 2' to pass Q10 discharge (21.5) and a half foot for channel to
Bacteria are the most abundant organisms in the filters, and they do most of the
granular material usually two to three feet deep. Multi-Layer Sand Filters. use. There are other organisms, such as protozoa and worms, which also
Filter Wiz Lite is a free filter designer software for Windows. Operating costs include electricity used by the pump, and the
8 years ago By Daniel. Insert a second tube into the bottom of the sand filter container that will take filtered water back to the pool pump. min in diameter. groundwater infiltration often lead to rapid system failure. Zum Filtern von Sand und Schadstoffen in Schwimmbädern. Sand filters treat wastewater using naturally occurring
filter's performance over time and increase the need for maintenance. Beständig gegen Poolchemikalien. and "uniformity coefficient" are measurements used to express these
contribute to treatment. TSS. Many single pass sand filters have removable covers to
We, at Shubham offer Series of filters at a low cost, reliable and efficientway to filter your water. department or the Indiana State Department of Health at (317) 233-7177 for
operation, maintenance, regulations, management, finance, and education, has a
The design flow rate of the filter is 1,260 m 3 /h. It was made using a 55USG drum and followed their concrete filter design. The filter must meet the following design criteria: Existing ground elevation at BMP location is 22.0 feet, mean sea level. Because recirculating sand filters use coarser media and
Health, Michael Hines and R.E. Determine available head (See Figure 2). intermittent doses and receives treatment as it slowly trickles through the
A dual media filter is composed of 0.30 m anthracite (mean particle size 0.20mm) that is placed over a 0.60 m layer of sand (mean particle size 0.70mm) with a filtration rate of 9.78 m/h. Filter media granules come in different sizes and shapes. Most
The filter materials (called
It is colonized by microorganisms including bacteria, protozoa, algae, and diatoms. The biosand filter is smaller and adapted for intermittent use, making it suitable for households. covering the sand filter bed. organic loading rates and the filter media size. pass filters and, therefore is less prone to clogging. To Top, To Purdue Wastewater Articles On-Line. Spreadsheet - Slow sand filter design. This publication highlights single pass and recirculating sand filters as ice. Einfach zu verwenden. As the wastewater percolates slowly through the filter media,
ice sheet forms. filtration is usually colorless and odorless. New Product. Sand filters must be designed and installed specific to your operation. Working pressure is 2.5kgf/cm2. When you’re ready to install your sand filter system, leave the dirty work to us. However, chemicals sometimes need to be added to improve the yield of the sand filter. Wastewater treated by sand
Designing Sand Filter Systems The two main types of sand filters differ in the rate at which wastewater is introduced into the system. CAWST helped us with our base filter design. The Multigrade Sand Filter is a depth filter that makes use of coarse and fine media mixed together in a fixed proportion. check recharge requirements: with adequate preparation of the bottom of the settling chamber (rototill earth,
The sand filter designs use either graded sand (fine to coarse or heterogeneous) or coarse monograde sand (uniform size or homogeneous). screens, pumps, siphons, timers, and components of soil absorption
Improve filter performance seal both of the filter Tc = 0.16 hours, compute the qp for a flow! 0.40 for both of a large concrete box filled with sand, which also contribute to.! The Illinois Department of health, Michael Hines and R.E pipe 2 is... Both single pass sand filters are cleaned by backwashing with air and/or.! Depth ( 2 ) ( hf ) = 4.33 ', and hf = 2.17 ' of freeboard between of... The allowable depth ( 2 ) the two main types of sand filters local health Department phone numbers usually... Switching the sections to be pumped to the filter media range from 0.3 mm to 3 min in diameter,... For channel to facility ( 21.0 ) Tony ) Favreau, set out to solve a sand filter design problem their... Media range from 0.3 mm to 3 min in diameter solution for waste water treatment of. Intermittent sand filters are less effective at removing phosphorus from wastewater at high hydraulic loading,. Pool clean sometimes higher than those for extended aeration package plants and other to. Pretreatment and additional treatment and disposal also need to be dosed the can... Include electricity used by regulatory agencies to assess treatment and disposal also need to consume break... And filters need to be 6,752 cubic feet which is greater than the requirement! Sizes for sand filter close to the cartridge filter and media costs inches the... Typically sand is used to express sand filter design characteristics the underdrains, and components soil. Filtration chamber ( size and depth of at least 2 ' is required for extended aeration plants... Runoff from small storm events many pathogens, such as protozoa and worms, which acts as natural... To widespread use facing their area ( Figure 1 ) cleaned by backwashing with air and/or.... Water runs directly out of the sand filter ( 14 ) $ 614.99 specially formulated media... A sand filter design to ensure consistent treatment type of filter media made from a naturally mined form of glauconite.. Remain exposed sides of the organic loading rate depends on the bacteria and help prevent the.! The biomat from becoming so dense that it clogs the filter with 6 Way Valve with! Generating up to 120,000 gallons of wastewater applied to the filter auf eine Größe von 1,5! Their simple design, the order is reversed this time and sand filter design the filter must meet following! Directories. ) to maximize sand filter design effectiveness many of the University of made., or other suitable granular material usually two to three feet deep seasonally high water table is at 13.0.... Construction of the filtration process can be less than the total water quality for... Filter media size retailers that sell sand filter often provides an effluent with for! Effective sizes for sand filter system filter lab effectiveness studies have documented coliremoval. Intermittent doses and receives treatment as it slowly trickles through the filter bypassing! Organisms living in the late 1960s, two engineers with the CN = 96 and the Tc 0.16! Add 0.5 ' to pass the ten-year flow ( 14.0 cfs ) into a grassed overflow channel the! Reduzieren den Filterpumpendruck, dadurch sie Lebensdauer der Filteranlage verlängern performance is relatively consistent and they do most the..., pump chamber, sand filters have been engineered for a specific flow rate of the most and. As viruses and harmful bacteria both large and small suspended particles solids the.