Appropedia:Shared Source Initiative biosand staging area

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Licensing[edit source]

See Sand Filter staging area#Licensing (same author).


Progress[edit source]

Done:

*Specific_details 
*Baffle_detail 
*Input screen 
*Complete filter 
*first flush diverter 
*Clean water from filter 
*Input without coarse screen 
*Fine screen 
*Baffle pipe design 
*Recent Modifications 
*JUNE 1 2008: NEW FILTER DESIGN 
*Water test results
*Contact the author

More in left navbar.

Content[edit source]

Building a small slow sand water filter for individual use 6
San Juan Sunset
images by: David Tarsi
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> Introduction -

Specific_details -
Baffle_detail -
Input screen -
Complete filter -
first flush diverter -
Clean water from filter -
Input without coarse screen -
Fine screen -
Baffle pipe design -
Recent Modifications -
JUNE 1 2008: NEW FILTER DESIGN -
Water test results-
Contact the author-
 First posting 2007-08-13-
 Website Last updated 2010-02-05-


Here are some links to other sites on BioSand and slow sand filters: General information on Slow sand filters

Harvesting rainwater and BioSand filters

Brief description and drawing of a BioSand filter

Filters are used in many parts of the world

Drawings and explanations

Manufacturer of filters

Manufacture of filters

Nice explanation and drawing in English and other languages

Very detailed explanations are here at this site

More detailed explanations here

M.I.T. site

Commercial site and one of the first developers of the BioSand filter

Pictures and explanations here

this link has information about the size of sand grains: (.15 - .35 mm)

http://www.shared-source-initiative.com/biosand_filter/biosand.html An article on slow sand filter maintenance

Introduction-

* NEW * GOOD NEWS FOR RESIDENTS OF WASHINGTON STATE:note As of October 9 2009, HARVESTING RAINWATER FROM YOUR ROOF IS NO LONGER A CRIME! The department of Ecology in Washington state (the D.O.E.) has finally clarified the law so as to allow individuals to catch rainwater for their own use. (from this preceding link, click on the links at the D.O.E. site on the upper right hand side of their page that say "new" highlighted in yellow.) -

* NEW * The slow sand filter and first flush diverter described here will remove petroleum hydrocarbons from water collected from the composition roof used here (to collect water) down to less than 2 parts per ten million by weight. The preceding link points to all the info.-

* NEW * Download the first flush diverter DEMONSTRATION VIDEO-

     Also see a demonstration video of the roof water filter system:-

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This site is about the filtration and purification of water through the use of sand, gravel and naturally occurring processes and describes how to put together a small slow sand water filter for under eighty five dollars.. The results of the tests on water run through the filter described on this website can be found here. If you want to know how well the filter works this would be the best place to start. A summary of this entire project along with details of the construction and performance of two additional filter designs can be found at slowsandfilter.org. This is a work in progress and information will be added as more investigation is done. Also, read this blog for discussion, questions, and collaboration on slow sand filters. -

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Note: In the past five or six months websites describing biological sand filters / slow sand filters have been appearing with instructions recommending BACK WASHING a biological sand filter when the flow rate slows down. This is TOTALLY WRONG. DO NOT BACK WASH A BIOLOGICAL SAND FILTER - YOU WILL RUIN IT. The flow rate is slowed by a buildup of material on the TOP FEW CENTIMETERS of sand. Simply gently agitating this layer and DRAINING OFF the cloudy water is all that needs to be done.28 (p.17, 93) These well meaning people have apparently confused rapid sand filtration with biological sand filtration. -

If designed correctly these biological sand and gravel filters do not need any electricity or petroleum products to enable their operation, they work because of the pull of gravity on water and naturally occurring biological processes. If the filter and the storage containers are positioned such that the filter is higher than the storage container/s the water will flow into them and a pitcher pump can be used to extract the water from the storage container. Pathogens, and to some extent inorganic chemical pollutants, can be removed from water through the use of biologically active layers of sand in an aquatic oxygen-rich environment often called a slow sand filter, or biosand filter. Both of these types of filters are very good examples of sustainable technology as they can work without electricity or petrochemicals and they do not pollute or produce unusable by-products, last many years, and can be built from recycled materials. If you intend to build a filter, please read ALL of the information on this website BEFORE you start. Many sources of water, particularly in the U.S., contain chemical pollutants that require more than just a slow sand or biosand filter for their complete removal, however this is the exception rather than the rule - for now. . . .-

What is a slow sand filter?-

A slow sand filter (often called a BioSand filter, or a biological sand filter) is used to filter and clean water through the use of layers of sand and biological action. As oxygen and organisms in water pass through the sand, a biofilm - an aquatic biological strata of living organisms in the sand - forms in the top layers of the sand as water passes through the filter. This biofilm or schmutzdecke extends from the surface of the sand down 2 or 3 cm although biological activity occurs with less density at greater distances from the surface of the sand. Through biological action and some sand filtration, pathogens are rendered harmless through complex naturally occurring processes."Viruses are effectively removed or inactivated by slow sand filtration and soil passage, but they are more resistant to UV and coagulation combined with sedimentation (9, 43, 50)." 1 The complete operation of the biological action in a slow sand filter is complex and is currently being studied by scientists; however effective filters can be built by the average person.4 A slow sand filter must maintain a constant water level above the surface of the sand; and oxygen is necessary to maintain proper operation. Slow sand filters are now gaining popularity because they do not require chemicals or huge amounts of energy to function. -

What is the difference between a slow sand filter and a BioSand filter?-

These two names both refer to a water filter that uses naturally occuring biological processes in layers of sand and gravel to purify water. A slow sand filter usually has a constant flow of water through the sand and gravel, is quite large and used to purify water for municipal water distribution systems. The concept of slow sand filtration has been around almost as long as civilization, but there have been many improvements on the design and the understanding of operation. The BioSand filter, developed by a scientist from Canada, is a modification of the slow sand filter design . It is usually much smaller and can be operated intermittently; and it is particularly well suited for use on an individual household basis. The biofilm layer in both types of filters must be continuously covered by water but the depth of the water on top of the sand is only about 1 inch in a BioSand filter because the intermittent flow of water limits the oxygen supply. Oxygen supply is critical to keep the biofilm alive and functioning in both types of filters. A slow sand filter can be small (50 gallons) or large (public water supply). A "BioSand filter" is usually small (65 gallons or less). In both types of filters the biofilm can take up to 3 weeks to become fully effective in a newly constructed filter.-

How safe is the water from a slow sand filter / biosand filter? This is not a simple question to answer. These filters have been in use in the U.S. since 1829; and are becoming more popular because of their ability to produce clean water acceptable to new standards set by the EPA.14 Biological sand filters are very efficient at removing disease causing bacteria from water. They remove 99.9 percent of beaver fever cysts and cryptosporidum from water. These bacteria are very resistant to chlorine in conventional water treatment and are more effectively removed by slow sand / biosand filters. Some viruses are trapped in the biofilm as their bacterial hosts are killed when they are trapped and consumed in the biolayer, however the removal of viruses by slow sand filters / biosand filters is still being studied. This is water purification by the removal of harmful pathogens.These filters do not add inorganic chemicals to kill organisms. Most conventional public water supply systems add chemicals such as chlorine, or ozone to kill micro-organisms and as a result chemical toxins are produced (this DOES NOT happen in a biosand, or slow sand filter) and furthermore, not all viruses are completely inactivated by chlorine. ( Not as much is known about the inactivation of viruses as is known about the removal and inactivation of bacteria in slow sand / biosand filters )8,9,10,11 In the filter described on this website, all Ecoli are removed along with all coliform bacteria. Turbidity (cloudiness) is significantly reduced. If there is at least 3 feet of sand in the filter covered by water continuously and the simple design parameters and operating instructions found on this website and in many other places on the web are followed - and the water used is free from chemical contamination, the water will be safe to consume. Chemical pollutants such as heavy metals, pesticides, herbicides and petroleum contaminants are not removed as completely as pathogens and organic particles, however a significant percentage of this type of contamination is removed. IF YOU ARE PUTTING A FILTER TOGETHER FOR THE FIRST TIME, HAVE THE WATER TESTED BEFORE YOU CONSUME ANY, and educate yourself about the operation, theory and maintenance of these filters. Many of the filter designs that are in use in parts of the world other than the U.S.have been tested and are known to work. Understanding the theory does not require a college degree. If you can read and / or use the internet, you should have enough knowledge to easily build and use one of these filters successfully. Once the filter is operational, the water is safe, but maintenance is critical and absolutely necessary, so educate yourself!! Disease causing pathogens can enter the water from anywhere. If you intend to consume the water from one of these filters, be absolutely certain you have a way to test the water. If you live near a creek or small stream, the water from that source can be purified by a slow sand filter and will be safe to drink - but caveat emptor - have the water tested before you drink it - if it flows through a suburban or urban area in the U.S. with dwelling units near it, pathogens in the water may be the least of the problem - pesticides, herbicides, petroleum distillates and many other chemicals and poisons may be in the water caused by runoff from roads, roofs, drain fields, and yards that have been treated with pesticides, herbicides and wood preservatives. Since many populations in the U.S. have access to thousands of "products" that contain poisons, the situation in affluent neighborhoods the U.S. is not the same as the situation in other places. In many other areas of the world the main problem with the water is biological contamination, which is easily handled by a slow sand filter; however in the U.S. and some other "advanced industrialized cultures" chemical poisons are an enormous problem and are only partially removed by slow sand filters.-

Will a slow sand filter / biosand filter purify water collected from a roof?-

Yes, under certain conditions. If you intend to drink the water collected from a roof, I STRONGLY URGE YOU TO USE A "FIRST FLUSH DIVERTER"7; it will minimize the extent of dissolved chemicals from dust, pollution and roofing material in the water collected after a dry spell. Most asphalt 3 tab roofing material has a coating of inert mineral material attached to the asphalt base and may not leach significant amounts of petroleum based chemicals until it is near the end of its life and starts breaking down, or when it is very new.5-

Although the water from a slow sand filter is of very high quality, I would strongly recommend the use of a UV filter followed by a ten stage carbon filter, or a "drip filter" to filter the water from the slow sand filter that you intend to drink on a regular basis.-

IMPORTANT!-

The roofing material on many houses in the U.S. contains poisons that kill moss. These poisons will be in the water collected from these roofs and cannot be completely removed by a biosand filter. In this part of our state there are roofing companies who advertise a moss-kill product they will apply to your roof to kill "that nasty moss that will destroy your roof". Our roof, here in the forest, was covered with moss, and lasted 30 years. The part that was in the worst shape was the part exposed to the sun - the moss was not the problem. Go figure. Also, the more research I do, the more convinced I am that any composition shingle roof (3 tab) is not a good surface from which to draw drinking water, because of the petroleum based chemicals (bitumens) used in the manufacture of this type of roofing material; however, most asphalt 3 tab roofing material has a coating of inert mineral material attached to the asphalt base and may not leach significant amounts of petroleum based chemicals until it is near the end of its life and starts breaking down, or when it is very new.5 As the roof material wears out, increasing amounts of these chemicals may be in the water collected from these types of roof surfaces.5 At the best, with a first flush diverter this water may be OK for temporary use, but consumed over a long period of time will be very harmful unless extensive carbon filtering is used. The biosand filter will remove the harmful pathogens very efficiently and will remove most of the non-organic particles,-

however for drinking water the best type of roof is a metal roof called "Galvalume". It is coated with non-toxic baked on enamel. This is the type of roofing material that "green" buildings have installed.-

If you have a "carport" or garage with metal roofing that is not rusted and has a non-toxic paint coating (most do) that would be a good place to start and if you intend to drink the water, I would still highly recommend a "first flush diverter". The roof will add no toxins however air pollution particles deposited during a dry spell will be in the first 15 or 20 gallons that run off the roof.-

The level of chemical pollutants from roof water will vary - if you don't have built in moss-killing poison or zinc strips on your asphalt (3 tab) roof, and it is in the "middle" of its "life" with moss growing on it, a "first flush diverter"7 will eliminate most of the harmful chemicals originating from the roof material5 and atmospheric pollution. The danger from these chemicals, since many bio-accumulate, is in prolonged exposure (as in years). If you use a 10 stage carbon filter following the slow sand filter, your water quality will probably be acceptable. The slow sand filter / biosand filter will remove nearly all the bacteria so moss on a roof is not a concern. Run the water through the biosand filter first, the bacteria will clog a carbon filter quickly. Carbon filters do not remove all the bacteria; in fact over time, bacteria will grow in a carbon filter and produce water outflow that has more contamination than the inflow. Non-toxic metal roofing can be installed over existing composition roofing material. It is slightly more expensive, but is lighter, will outlast a composition roof by 2 to three times the number of years, stand up much better in a storm, will not pollute the water that runs off of it, and metal roofing is fireproof. There are non-toxic coatings that can be applied to composition roofs that will prolong the life of the roof and allow water not contaminated with herbicide or petroleum derivatives to be collected from the roof. Also, if you have a roof without embedded moss-killing poison,(composition, fiberglass (3 tab)) a plastic tarp (check to make sure the tarp does not contain poisons) draped over the part of the roof that delivers water to your filter will help to keep most of the petroleum pollutants to an acceptable level. Even if you take water from a "non-toxic" roof, there will be poison chemicals in the water from local air pollution and small traces from atmospheric pollution. The amount will vary depending on your location. A stream that flows year round is constantly refreshing the water. A roof often sits dry for weeks or months, so pollutants build up on the roof surface and are far more concentrated in the first rain event than they would ever be in a small stream or creek several days after the first rain following a dry spell. This is why a first flush diverter is absolutely necessary.-

WARNING!!!!!!: Almost all raccoons carry parasites (Baylisascaris procyonis) often called raccoon roundworms, that are usually harmless to the raccoons. These roundworms each produce millions of eggs which can remain active in the environment for years. Ingestion of the active eggs of Baylisascaris procyonis can cause serious illness and there is no cure; and furthermore, chlorine, alcohol or ozone will not kill them. Young children are particularly susceptible. Roof surfaces can be contaminated by these parasites' eggs if raccoons have access to the roof in question. Water collected from a roof contaminated with these eggs may wash them into rain barrels. Although infection in people from Baylisascaris procyonis is rare, the dire consequences warrant extreme caution. Even though a functioning slow sand filter should remove these eggs, (they are larger than 50 microns) the filters described here have not been tested for the removal of these parasites' eggs. If you have ANY raccoons anywhere near your roof you must assume your roof is contaminated and be aware that a slow sand filter may not remove the parasite's eggs from the roof water unless it is functioning correctly, and that WATERING A VEGETABLE GARDEN WITH UNFILTERED WATER FROM A RAIN BARREL THAT IS CONTAMINATED WITH THE EGGS WILL LIKELY RESULT IN INFECTION AND SEVERE DISABILITY, and even fatality in some cases. Please read the references listed in the following link for more detailed information: 29, 30, 31, 32-

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New!-

Links to pages showing how to put rain catchment systems together:-

An interesting rain barrel project page This site has very detailed specific information on constructing and setting up rain barrels - the first step in getting water from a roof.-

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Why would someone want to put one of these together?-

If you live in an area where water is at all an issue then there is every reason to do this. The water that runs off your roof can be collected and run through one of these filters and then be safe to use for just about anything. however before you consume any roof water from a slow sand filter or biosand filter HAVE IT TESTED - and if you plan to use the water as your main supply use a 10 stage filter followed by a UV filter for the water you intend to consume. If you are on a public water supply system DO NOT HOOK YOUR FILTER OUTPUT UP TO YOUR PLUMBING. -

The moss-killing poison, and/or petroleum based pollutants present in roofing material will end up in the water that that runs off of many, if not most roof asphalt surfaces and as a result will be concentrated in the ground around the houses that have them, or worse; in many cities this water goes directly to the storm drain where the chemicals do not have a chance to biodegrade (if indeed they actually do break down in the soil). From the storm drain, the water from thousands of roofs often goes directly into rivers and streams. Now that there are droughts in many places in the U.S. we, as a nation, have to face our own arrogance in neglecting to think ahead. If our roofing materials were not designed such as to leach poisons, there would be a lot more water available at far less expense for us all. But then hindsight is always 20/20 . . . -

In the metro areas of most cities, during a dry spell water is rationed. If you have a flower garden, or a vegetable garden, this water from a slow sand filter can be used for that purpose. After you have set up the collection system and the filter the water is free. Ten 55 gallon drums can hold a lot of water. Simply collecting the water that runs off your roof is OK, but if anyone ingests it they could get very sick. Once the water has been run through a functioning slow sand filter it is much safer than untreated water. ( remember: The water from a roof is not the same as the water from a creek or small stream. ) If I lived in Arizona, Nevada, or any of the dry hot areas of the southwest U.S. I would consider something like this an absolute necessity, and I would have a storage tank of very large capacity to hold the filtered water. -

Several inches of rain on the average roof can yield thousands of gallons of water. (do the math here). If you are careful about the material used on your roof this water could be used for drinking water, but I would have it tested first; however, as evidenced by the information at the links above, BioSand filters are now being used in many areas around the world to make drinking water safe. -

At the risk of sounding ultra-paranoid, the following must be considered:-

It is important to know the condition of the environment from which the water is being taken. The situation in the location of this filter is unique in that the water collection surface is surrounded by trees and a large wildlife area located in the northwestern part of the U.S. . If water from a slow sand filter system similar to this one in surroundings and design is to be used for consumption on a regular basis, it would be advisable to run the water through a UV (ultra-violet) filter following the output from the slow sand filter In other areas of the world the situation will very likely be quite different.-

The operation of these biological sand filters has been documented with repeated investigations and tests showing the same result: Disease causing organisms are removed through naturally occurring processes; and turbidity is reduced to the extent that the water is safe to consume. This website is documentation of one more independent observation that shows the same result as the others. When properly constructed and maintained, biological sand filters work as claimed regarding the removal of bacterial pathogenic organisms. All of The test results can be seen here (a large image file). -

For those who are interested in the Laboratory doing the testing; I will supply the other details on request. -

File:12.png-

note Why is this "good" news? -

1. Enough water for survival should be free for everyone. It is as necessary for life as air - that one is sort of a no brainer.-

2. If enough people in the city catch rainwater in rain barrels, the load on the storm drains is reduced considerably - and there is-

less chance of the drains overflowing and spreading contaminated water into the environment before it is treated. This is good news for-

everyone, as less pollution is washed into streams, rivers, lakes, and oceans during a significant rain event.-

3. In the summer, water can then be conserved by using the stored water for flower gardens, lawns, and if filtered by a slow sand filter, -

vegetable gardens can also be irrigated; thereby significantly reducing the load on the public water supply.-

4. Most importantly, it appears as though government is finally getting a clue. . . hopefully I'm not wrong about this. -

Good job WA. state gov., thank you! Tax dollars well spent this time! -

WARNING: DO NOT WATER VEGETABLES WITH WATER STRAIGHT FROM A RAIN BARREL, AND NEVER - EVER CONSUME WATER FROM A RAIN BARREL.-

ROOFTOPS COLLECT LOTS OF PATHOGENS (HARMFUL BACTERIA AND VIRUSES) AND POISONS THAT WILL MAKE PEOPLE VERY SICK.-

A first flush diverter and a slow sand filter, at the very least, must be used if vegetables are to be safely irrigated using water from rain barrels.-

Read this slow sand filter FAQ page before you set up rain barrels.-

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REFERENCES:-

1. Presence of Noroviruses and Other Enteric Viruses in Sewage and Surface Waters in The Netherlands W. J. Lodder and A. M. de Roda Husman* Microbiological Laboratory for Health Protection, National Institute of Public Health and the Environment, Bilthoven, The Netherlands.-

Corresponding author. Mailing address: -

Microbiological Laboratory for Health Protection, National-

Institute of Public Health and the Environment, P.O. Box 1,-

NL-3720 BA Bilthoven, The Netherlands. Phone: 31 30 274 4325.-

Fax: 31 30 274 4434. E-mail:-

2. Coliform Bacteria and Drinking Water (Washington State Department of Health)-

3. The "average" roof can collect many undesirable substances. Caution is advised.-

4.The following abstracts were accessed: November 23, 2007 and would be very good reading especially for understanding the biological action in a (slow) sand water filter:-

Biological and Physical Mechanisms in Slow Sand Filtration-

Haarhoff, J; Cleasby, JL-

IN: Slow Sand Filtration. American Society of Civil Engineers, New York. 1991. p 19-68, 11 fig, 10 tab, 54 ref.-

Slow Sand Filtration: Influences of Selected Process Variables-

Author(s): Bellamy, William D.; Hendricks, David W.; Logsdon, Gary S.-

Citation: Journal AWWA, Vol. 77 Iss. 12, December 1985, Page(s) 62-66-

Bacterivory by a chrysophyte in slow sand filters-

Monroe L. Weber-Shirk* and Richard I. Dick-

School of Civil and Environmental Engineering, Cornell University, Ithaca, NY 14853-3501, USA-

Received 1 September 1997; accepted 1 June 1998. Available online 25 February 2000.-

Information on roofing material:-

5. A review of Methods for the Manufacture of Residential Roofing Materials. Hashem Akbari, Ronnen Levinson, and Paul Berdahl. Heat Island Group Lawrence Berkeley National Laboratory, Berkeley, Ca. 94720. A report prepared for: California Energy Commission PIER Program. June 2003.-

6.Use this information at your own risk. The Author assumes no responsibility whatsoever for any damages of any kind as a direct or indirect result of the use of any information on this website. The information provided here is free and published with the intent of sharing experience, and is not provided as an absolute solution to anything. This is a work in progress. Mistakes will likely be found. We reserve the right to remove this content or change it at any time we choose. You have been advised.-

7. A first flush diverter will not eliminate ALL bacteria or viruses from roof water, although in some cases a considerable percentage of pathogens may be removed.-

8. Read more about viruses here: freedrinkingwater.com/water-education2/87-water-disinfection2.htm-

9.Mechanisms of inactivation of hepatitis A virus in water by chlorine dioxide: Jun Wen Li Corresponding Author Contact Information, E-mail The Corresponding Author, Zhong Tao Xin , Xin Wei Wang , Jin Lai Zheng and Fu Huan Chao Institute of Health and Environmental Medicine of Tianjin, 1 Da Li Road, Tianjin City 300050, People's Republic of China Received 15 April 2003; Revised 7 November 2003; accepted 13 December 2003. Available online 4 March 2004.-

10. www.moh.govt.nz/moh.nsf/0/5A25BF765B400911CC25708F0002B5A8/$File/07-viruscompliance.doc-

11. viruses that are not killed by chlorine in swimming pool water (caliciviruses): www.cumc.columbia.edu/dept/ps/2007/mid/2006/transcript_02_mid37.pdf -

12. The Turbidity Tube: Simple and Accurate Measurement of Turbidity in the Field: Written April 2006 for the requirements of CE 5993 Feild Engineering in theDeveloping World and FQ 5770 Community Planning and Analysis. Elizabeth Myre and Ryan Shaw M.S. Candidates. Department of Civil and Environmental Engineering; Master's International Program. Michigan Technological University. -

13. SUSTAINABLE DRINKING WATER TREATMENT FOR SMALL COMMUNITIES USING MULTISTAGE SLOW SAND FILTRATION; by Shawn A. Cleary. A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master of Applied Science in Civil Engineering Waterloo, Ontario, Canada, 2005 © Shawn A. Cleary 2005. page 31,32. uwspace.uwaterloo.ca/bitstream/10012/926/1/scleary2005.pdf accessed Sept 27 2008. -

14. "BACTERIVORY BY A CHRYSOPHYTE IN SLOW SAND FILTERS" MONROE L. WEBER-SHIRK and RICHARD I. DICK-

School of Civil and Environmental Engineering, Cornell University, Ithaca, NY 14853-3501, U.S.A.-

Wat. Res. Vol. 33, No. 3, pp. 631-638, 1999. -

15.Toxicant and parasite challenge of Manz intermittent slow sand filter G. Palmateer, D. Manz, A. Jurkovic, R. McInnis, S. Unger, K. K. Kwan, B. J. Dutka Environmental Toxicology. Volume 14, Issue 2 , Pages217 - 225. Copyright © 1999 John Wiley and Sons, Inc.-

16. Logan, A.J.; Stevik, T.K.; Siegrist, R.L.; Rønn, R.N. 2001. Transport and fate of Cryptosporidium parvum oocysts in intermittent sand filters. Wat. Res. Vol. 35, No. 18, pp.4359 - 4369.;-

17. Concise International Chemical Assessment Document 59-

First draft prepared by Ms Joann A Wess, Dr. Larry D. Olsen, and Dr. Marie Haring Sweeny, National Institute for Occupational Saftey and Health, Cincinnati, Ohio, USA.-

World Health Organization Geneva, 2004-

http://www.who.int/ipcs/publications/cicad/en/CICAD59_AsphaltWebVersion_2004_08_04.pdf-

18. The Contribution of particles washed from rooftops to contaminant loading to urban streams.-

P.C. Van Metre, B.J. Mahler. US Geological Survey, Research and INvestigations, 9802 Exchange Dr., Austin TX. 78754-3898.-

Chempsphere www.elsevier.com/locate/chemosphere -

http://tx.usgs.gov/coring/pubs/rooftops%20Chemosphere.pdf-

19. House Roof Runoff: Is It as Clean As We Think?-

Jennifer Gadd and Paul Kennedy. Kingett Mitchell and Asociates-

http://www.kma.co.nz/downloads/PDFs/Publications/House%20Roof%20Runoff%20-%20Gadd,%20Kennedy.pdf-

20. Determination of Polycyclic Aromatic Compounds in Asphalt and In Correspoinding Leachate Water.-

A.J. Kriech, J.T. Kurek, L.V. Osborn, H.L. Wissel, B.J. Sweeney. Heritage Research Group, Indianapolis, Indiana, USA.-

Polycyclic Aromatic Compounds, 22:517-535, 2002.-

21. Information on Tannins from Cornell university (www.ansci.cornell.edu/plants/toxicagents/tannin.html)-

22.Western Wood Preservers Ltd. 26035 - 31B Avenue, Aldergrove, BC V4W 2Z6 - Telephone: (604) 857-1900 - 856-7779-

23.Using CCA Preservative-Treated Lumber in Gardens and Landscaping. Publication Number: 8128 Inventory Type: PDF File Language: English ISBN-13: 978-1-60107-307-5 Copyright Date: 2004 Length: 8 pp.-

University of California http://anrcatalog.ucdavis.edu/Items/8128.aspx-

24.EPA evaluation of Chromated Copper Arsenate (CCA) and other preservatives-

25.Corso PS, Kramer MH, Blair KA, Addiss DG, Davis JP, Haddix AC. Cost of illness in the 1993 Waterborne Cryptosporidium outbreak, Milwaukee, Wisconsin. -

Emerging Infectious Diseases. (serial online) 2003 Apr. Date Cited: 2009-01-03. -

Available from: URL: http://www.cdc.gov/ncidod/EID/vol9no4/02-0417.htm -

26.The significance of algae as trihalomethane precursors-

Graham, NJD | Wardlaw, VE | Perry, R | Jiang, Jia-Qian-

RESERVOIR MANAGEMENT AND WATER SUPPLY--AN INTEGRATED SYSTEM. pp. 83-89. Water Science and Technology (Water Sci. Technol.). Vol. 37, no. 2.-

27.Identification of New Drinking Water Disinfection by - Products from Ozone, Chlorine Dioxide, Chloramine, and Chlorine-

Journal Water, Air, and Soil Pollution-

Publisher Springer Netherlands-

ISSN 0049-6979 (Print) 1573-2932 (Online)-

Issue Volume 123, Numbers 1-4 / October, 2000-

DOI 10.1023/A:1005265509813-

Pages 95-102-

Subject Collection Earth and Environmental Science-

SpringerLink Date Monday, November 29, 2004-

S. D. Richardson1, A. D. Thruston Jr.1, T. V. Caughran1, P. H. Chen1, T. W. Collette1, K. M. Schenck2, B. W. Lykins Jr.2, C. Rav-Acha3 and V. Glezer3-

(1) National Exposure Research Laboratory, U.S. Environmental Protection Agency, 960 College Station Rd., Athens, GA 30605, USA-

(2) National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr., Cincinnati, OH 45268, USA-

(3) Research Laboratory of Water Quality, Israel Ministry of Health, 69 Ben-Zvi St., Tel-Aviv, 61082, Israel-

http://www.springerlink.com/content/v07603q640222762/ -

accessed: 2009-01-03-

28. Slow Sand Filtration. L. Huisman, Professor of Sanitary Engineering, Department of Civil Engineering,-

Technological University, Delft, Netherlands. W.E. Wood, F.I.C.E. Formerly Chief, Community Water Supply, World Health Organization , Geneva.-

World Health Organization, 1974, ISBN 9241540370-

www.who.int/water_sanitation_health/publications/ssf/en/index.html accessed 2009-04-03.-

29. Eberhard ML. Nace EK, Won KY, Punkosdy GA, Bishop HS, Johnston SP. Baylisascaris procyonis in the metropolitan Atlanta area. Emerg Infect Dis 2003 Dec. Available from: URL: http://www.cdc.gov/ncidod/EID/vol9no12/02-0795.htm Accessed 2009-07-06-

30. Patrick J. Gavin, Kevin R. Kazacos, and Stanford T. Shulman . Baylisascariasis. Clinical Microbiology Reviews, October 2005, p. 703-718, Vol. 18, No. 4. Accessed 2009-07-06. http://cmr.asm.org/-

31. http://www.dpd.cdc.gov/DPDx/html/ImageLibrary/A-F/Baylisascariasis/body_Baylisascariasis_il3.htm -

32. Shafir SC, Wang W, Sorvillo FJ, Wise ME, Moore L, Sorvillo T, et al. Thermal death point of Baylisascaris procyonis eggs. Emerging Infectious Diseases. Volume 13, number 1. 2007 Jan. Accessed 2009-07-09 Available from http://www.cdc.gov/ncidod/EID/13/1/172.htm -

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input-

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complete biosand filter-

Complete filter

filtered water in glass-

Water in glass

input without first screen -

Input without the first screen

second screen-

Second screen

baffle pipes-

Baffle pipes

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Specific Details[edit source]

Specific details

BioSand filter slow sand filter

biosand filter drawingFilter Drawing

These filters work, and they work quite well. The idea is not new, but the idea of intermittent use is. The idea is to give the filter a constant supply of oxygen so the biological process that takes place in the top layer of the sand can continue. This is done by maintaining 3 to 5 cm of water above the surface of the sand. I recommend 3 cm (a little over 1 inch - 2.54 cm = 1 inch), the more oxygen the filter has the better it will work.

Maintenance: Periodically slow sand filters or biosand filters must be cleaned because as the biofilm matures material accumulates on top of the sand inside the filter causing the flow rate to decrease. The top layer of sand must be carefully cleaned by first plugging the output spout (to prevent the excess biofilm and silt from traveling down into the filter bed) and gently agitating the water and the top surface of the sand. The excess build-up of silt and biofilm in the top 2 to 5 centimeters of sand are broken loose and the excess "silt-like material" and biofilm allowed to drain off while fresh water is added through the baffle until the "drained off" water is running clear. The extent to which the top layer of sand is disturbed will determine the length of time the filter must run to build up the biolayer so it effectively filters the water. I suggest if you are not sure about the effectiveness of your cleaning process, and have no way to test the water, have 2 systems running started about 3 weeks apart. That way each system can be cleaned alternately allowing a continuous supply of water to be available. With a basic understanding of the operation of these water filters (read the info found by clicking on the links below), the cleaning process can be accomplished by just about anyone. Be careful, however because the thicker the biofilm layer the better the filtration. It is a matter of maintaining a balance between flow rate and water purity. To be safe, allow 3 weeks of running time after cleaning before consuming the water. NOTE: DO NOT "BACKWASH" A SLOW SAND FILTER, OR A BIOSAND FILTER. DOING SO WILL DISTURB THE SAND LAYER FORMATIONS IN THE FILTER, AND DESTROY ITS EFFECTIVENESS. Back washing is used on rapid sand filters. Rapid sand filters are used in large municipal water supply treatment facilities.

If your filter is to be outside or where the temperature may get below 0 degrees centigrade (32 degrees F). DO NOT GLUE THE PVC PIPE UNLESS THERE IS A WAY FOR THE WATER TO EXPAND WHEN IT FREEZES. If you do glue the pipe and the water cannot expand as it turns to ice, you will be sorry. If the pipe is not glued, or if there is room for the water to expand the freezing water will just loosen or disconnect the pipe or extend past the opening - you may loose some water but you can put the thing back together easily. If the pipes are glued and there is no room for expansion, they will crack and you may not even know it, but you will have to replace them. This just happened to me - I did not glue them - and just finished putting it back together. 2008/01/20. Be careful, however, because if the pipes leak below the water level and the top of the sand is exposed to air, the filter's biofilm will die and foul the entire filter. This is a huge problem - all the sand may have to be removed and sterilized or water must be allowed to run through the filter for quite some time at a rapid rate to remove unwanted odors. Then the filter must be run for at least another 3 weeks and the water tested again before it can be used. Just make sure the filter has a way to keep the surface of the sand covered by water and a way to maintain access to oxygen because the filter's biofilm must be able to "breathe" - its functionality depends on aerobic organisms that get their oxygen from water.

There must be a baffle where the water is added or the biological layer will not form correctly because it will be disturbed every time water is added. Use coarse sand for the bottom layer and fine sand for the top 20 or 30 centimeters. Check the sand before you put it in the device to be sure it is clean, and be sure the device is where you want it and that the weight will be supported. As the filter is assembled, washed sand must be used or the water running through the filter will take quite some time to clear up. To clean the sand use a screen covered with a cloth. Put the sand in the cloth and run water over it until the water draining off of it is clear. For an intermittent filter you will want about 1 inch of water over the top of the sand, much more and there will not be enough oxygen to keep the biological layer alive. Allow at least 2 weeks before using the water. I would recommend 3 weeks and having it tested first. If the sand used is not thoroughly washed the water will not come out clear for some time depending on how much silt is still left in the sand. The filter should be at least 3 feet deep, and have drain system at the bottom similar in construction to the baffle only with larger holes drilled in the PVC pipes, some pea gravel to cover the collection system and then coarse sand over that. To keep 1 inch of water over the sand top bring the output pipe up to 1 inch above the top of the sand. The layer of biological material and activity is in the top layer of sand and to a lesser extent the coarse layer of sand and is where pathogens are metabolized. It helps to use a charcoal (carbon) filter on the output to help remove color. Make sure the carbon is approved for potable water. Water must be run through the filter continuously for 2-3 weeks. At a minimum maintain 3/4 inch water level above the sand by setting the output pipe at the corresponding length.Important: When constructing the filter, at the time the sand is put in, be absolutely sure no air pockets form or the filter will foul itself within several days and the water will not be safe and will likely have a very bad odor. This is because the organisms that grow in the aqueous solution must have water and oxygen continuously or they will die and decompose destroying the filter's operation. Fill the container with water first then add the sand and watch for bubbles to stop - this indicates the sand is saturated with water.

Size of sand: The size of the sand is critical.Graded sand is the best choice. The product description will say something like "4010" followed by "10 percent retained on 40 mesh or coarser" and may include a statement about the effective size for filtering like ".15 mm ES" (Effective Size). The sand used in the most recent version of the filter described on this website is .15 mm ES graded white silica sand. The most recent version of this filter (2007-11-01) has had water tested "pre-filter" and "post filter" and is fully functional. The "uc" (Uniformity Coefficient) of the sand used should be less than 2 with an effective size of .15mm to .35mm .

What about "silica sand"? Silica is a very common component of most sand on the earth. In fact it is so common that the EPA doesn't have any specifications on how much should or should not be in water. The problem with silica is that it is harmful to breathe the dust from it - very harmful - but it is also harmful to breathe water - probably more harmful. Graded silica sand can be purchased in small amounts and is probably the best way to assure proper operation of the filter. When silica sand is wet there is not enough dust to be harmful. When in water in small amounts, silica is not harmful enough to be of concern; in fact silica sand is used to filter water in many water treatment plants all over the country. If you use "silica" sand, don't breath the dust and wash it before you use it.

What about sand in general - what kind of sand should be used? Sand is quite abundant on the earth, unfortunately so is pollution that can find its way into sand. Also naturally occurring substances such as arsenic, mercury, lead and asbestos are sometimes found in sand. WARNING: Know exactly where the sand you use comes from and what is in it before you ever drink any water that has passed through it in your filter. There are two standards that suppliers/manufactures can choose to use, (National Sanitation Foundation)NSF 061 and/or (American Water Works Association) AWWA B100-01. I would highly recommend buying your sand from a manufacturer that adheres strictly to these standards, or use a high quality ten stage carbon filter on any water from your filter you intend to consume (this would not be a bad idea no matter what kind of sand you use).

The following website has listings of NSF certified sand suppliers and processing facilities: http://www.nsf.org/Certified/Common/Company.asp?Standard=061 Two of the companies listed at this nsf.org site have supplied the sand used in the filters described in the study described on this website They are: MANUFACTURERS MINERAL COMPANY in Washington state and Cemex in California. They are wholesale. You will need to find a hardware store, or building supplier near you to order products from them.

Pipes used The piping is all PVC pipe designed for use in drinking water systems. With the exception of the large connector sleeve on the 4 inch PVC, most of the fittings can be purchased for under 1.00 dollar each. The coarse sand and the fine sand are 30.00 dollars per cubic yard, the top layer of extra fine sand is 10.00 dollars for a 100 lb bag. The barrel holds .2 cubic yards which is less than 1.00 for the coarse sand and the fine sand used in the first 6 inches of sand. Four bags of the extra fine sand was used - that's 40.00 dollars for the sand. The cedar 2X6's were 50.00 and from those, 5 barrel tops were made - 10.00 dollars for the top. All the PVC couplings and pipe used cost 18.00 dollars. The screens and washers cost 6.00 dollars. The screens used in the input filter are stainless steel. The fancy vent on top was 7.00 dollars. The gravel used in the bottom cost under 1.00 dollar. The water, from rain is free. The total cost so far is 81.00 dollars.

In this filter, water collected from the roof of a rural building is being used. The water is run through the filter on an intermittent basis, not a continuous flow as in a large slow sand filter. Enough water must be added to keep the biofilm alive by supplying oxygen dissolved in the water. In testing this filter, water has been added daily: once in the morning and once in the evening in volumes of at least 4 litres about (5 quarts) at a time. Coarse, fine and graded sand are used as the filter media. The pea gravel keeps the sand from interfering with the functioning of the water collection pipes.

Since some the sand used in the first version of this filter was not "graded" sand, a random sample was taken from each supply of sand. After measuring, with a micrometer, each individual particle size discernible within reading distance (14 inches) each of these samples were examined and found to have 2 size groups of particles, large and small. The coarse sand having 40% large particles and the fine sand having 10% large particles. The small particles (not discernible from a reading distance as individual) in each sample were measured with a micrometer in 30 each random events giving a statistically accurate indication of the average and median sizes of the finer portions of sand in each sample. Random samples of the totally dry, coarse and fine and extra fine sand used in the filter, were placed in separate identical 1 gallon containers respectively; and water was added to each container in carefully measured amounts of 1 ounce each until the water appeared on the surface of the sand in each container. This way it was determined that the fine sand holds 49 percent water and the extra fine sand holds 50 percent water by volume when saturated; and the coarse sand holds 37.5 percent water by volume when saturated.

sand image

Size of the Sand used: The graded sand used was 4010 (10 percent retained on 40 mesh or coarser) and .15 mm effective size industrial quartz. On the ungraded sand, measurements were taken (in inches) with a micrometer and 30 random samples of the fine portions of both sand types were taken and the measurements recorded.

Coarse Fine
0.0530 0.0950
0.0440 0.0300
0.0430 0.0280
0.0390 0.0220
0.0390 0.0190
0.0390 0.0165
0.0320 0.0160
0.0320 0.0160
0.0300 0.0150
0.0300 0.0150
0.0280 0.0140
0.0280 0.0135
0.0260 0.0130
0.0260 0.0120
0.0260 0.0120
0.0250 0.0110
0.0250 0.0100
0.0250 0.0100
0.0210 0.0100
0.0210 0.0090
0.0210 0.0090
0.0200 0.0080
0.0200 0.0080
0.0190 0.0075
0.0190 0.0075
0.0180 0.0065
0.0175 0.0060
0.0170 0.0060
0.0150 0.0050
0.0120 0.0050
coarse sand fine sand
average: average:
0.0270 (.6858 mm) 0.0152 (.3861 mm)
median: median:
0.0255 (.6477 mm) 0.0115 (.2921 mm)
largest sizes: 40 percent of total largest sizes: 10 percent of total
largest .185 (4.699 mm) largest .112 (2.845 mm)
smallest .080 (2.032 mm) smallest .050 (1.27 mm)
average .133 (3.38 mm) average .081 (2.057 mm)

The 55 gallon barrel used in this filter is filled such that there is room for approximately 21 gallons of water saturating the sand including the water that must be on the surface. Twenty gallons of water are in the saturated sand. This means it takes 5 hours for a complete change of water in the system if 4 gallons are added regularly over a 5 hour period. The flow action of the filter is close to linear above 1 gallon of water added at a time until the water stops running out. Below that level it takes much longer for the water in the filter to be completely replaced. Adding 3/4 of a gallon at a time is the safest way to operate the filter, and still get a fairly acceptable flow rate.

2008-01-20: The filter has been operating for 4 months and the maximum flow rate is 12 litres (3.17 gallons) per hour. The water added has been a combination of continuously recirculated filtered water at a rate of 10 litres per hour combined with the addition of 10 litres of unfiltered water added every 24 hours. The average temperature has been 40 degrees F. A test will be done subsequently and the results posted as time and finance permits.

flow graph

Rainwater volume calculation formula: Back to introduction (Square footage of roof) X (Inches of rainfall) X (.62414) = volume in gallons This formula is derived based on: 1 cu. ft. = 7.481 gallons 1 cu. ft. = 1728 cu. in.

Keep in mind that the area of your roof is not necessarily the same as the area figured from linear measurements around the outside of your house. Most roofs have eaves and slope. Also the type of roof, and the use of a "first flush diverter" will disgard some of the water (a diverter may disgard as much as 10 percent per rain event - this discarded water can be used for irrigation of decorative landscaping and tasks that do not involve direct or indirect consumption - for example; if you water your lawn with this water and then use the clippings in a compost pile you are still concentrating the poison) NO MATTER WHAT KIND OF ROOF SURFACE YOU HAVE,DO NOT USE RAINWATER COLLECTED DIRECTLY FROM A ROOF FOR WATERING A VEGETABLE GARDEN. WITHOUT A DIVERTER THE WATER WILL CONTAIN CONCENTRATED POISONS THAT MAY BIOACCUMULATE IN PLANTS.THIS WILL VARY WITH TIME BETWEEN RAIN EVENTS AND HOW FAR YOUR ROOF IS FROM SOURCES OF AIR POLLUTION. For a roof with a 4/12 pitch with 2 foot eaves add 25 percent to the "linear measurement area result". This chart may help:

pitch: square foot increase:

1/12 ------- 20 percent
2/12 ------- 21 percent
3/12 ------- 23.5 percent
4/12 ------- 25 percent
6/12 ------- 34 percent
7/12 ------- 39 percent
8/12 ------- 44 percent

An 1800 square foot roof will collect approximately 2000 gallons of water from 2 inches of rain. The nature of the surface of the roof (smooth or rough), combined with the frequency of rainfall periods will determine exactly how much water can be collected. The use of a "first flush diverter" is manditory if the water is to be used for anything other than irrigation of landscaping vegetation.The diversion process will subtract at least 10 gallons per 100 square feet of roof area at the beginning of each rain event. If you live in an area that gets 12 inches of rain a year that would be: close to 12,000 gallons of water - not a lot but certainly helpfull and free, after the filter and storage are paid for. Some areas get over 35 inches of rain a year.


Baffle Detail[edit source]

Baffle Detail Baffle drilling detail This is a close-up of the holes drilled in the 1/2 inch pvc tubing. Don't glue the baffle pipe assembly together, it will be very hard to clean if you do. The drill size I used was .047 inches (a number 56 bit).



baffle detail Baffle detail


===Input screen===

Input screen The input on the top from the top. There are 2 screens in there. One is a coarse screen and the other in the center is a fine screen. They are both available at most hardware stores. The small screen in the center is between two washers. You will need to make this one. Witout a screen the baffle pipes will plug up in a very short time. It is much easier to clean out the screens that the baffle pipes.



input screen assembly-

Input screen assembly top view


Complete filter[edit source]

Slow sand filter in barrel The barrel is a recycled container. The top cover is cedar. There is an outlet at the bottom of the barrel.

the pipe on the side is a carbon filter made from pvc pipe and screens inside to hold the charcoal. The silver colored thing on the right is an inexpensive sprinkler head; it lets the air in and keeps the mosquitoes and other critters out. There is a screen on the left also that serves the same function, it was what I had on hand. The idea is that there must be oxygen to the surface of the water or the biofilm will die and the filter won't work. This barrel is almost full of sand and water and it is VERY heavy. When you put one of these together make sure it is where you want it and make sure where ever it is located that there is sufficient support for at least 2000 pounds in a concentrated area. You have been warned.

The top pipe is 4inch pvc fitting into a reducer adapter. You will need to slightly sand down the 4 inch pipe to be able to easily remove it to clean the screens inside. If you are careful this can be done. The 4 inch pipe holds the large input screen (see image below) in place. This length of four inch pipe on top holds about 1 quart of water, it has now been replaced with a 5 gallon bucket that has a .040 hole drilled in the bottom. The bucket sits over the reducer adapter

The fine sand holds 50 percent water by volume when saturated. The coarse sand holds 37.5 percent water by volume when saturated. This 55 gallon barrel is filled such that there is room for approximately 21 gallons of water including the water that must be on the surface. Twenty gallons of water are in the saturated sand. This means it takes 5 hours for a complete change of water in the system if 4 gallons are added regularly over a 5 hour period. The action of water flowing through the filter is close to linear above 1 gallon of water added at a time until the water stops running out. Below that level it takes much longer for the water in the filter to be completely replaced. Adding 3/4 of a gallon at a time is the safest way to operate the filter, and still get a fairly acceptable flow rate. Using the 5 gallon bucket with the .040 inch hole drilled in the bottom allows the water to flow into the filter from the bucket at about the right speed.



BioSand filter-

Slow sand filter

BioSand filter drawing-

Slow sand filter drawing


Input screen-

Input screen


first flush diverter[edit source]

First flush diverter drawing



first flow diverter-

A new version of this first flush diverter and a demonstration video can be found here.-

The idea of a first flush diverter is to keep the most polluted flow of water out of a rain water harvesting system. Most small systems take water from a roof surface. Dust, organic material, bacteria and air pollution particles build up on a roof surface during a dry spell. A month without rain will allow significant amounts of pollutants to settle on a roof. Water is one of the best solvents known to man. Because of this, the first flow from rain after a dry spell will contain concentrated poisons dissolved in the rainwater as it flows across the roof surface, or any impervious surface. Roads and parking lots accumulate even more poisions than roof surfaces. A first flush diverter prevents the first 15 or 20 gallons of toxic water from entering the storage system by diverting it into a temporary holding area and then allowing only the cleaner water to flow into the storage system. The recommended minimum amount of diversion is 1 gallon per 100 square feet of roof surface - this diverter is set for about 2 gallons per 100 square feet.-

How it works:-

New (November 11 2009): The output pipe has been changed to inch-and-a-half pipe; it was 3/4 inch. The 3/4 inch was way too small for moderate to heavy rainfall events. The diverter will now take up to 24 liters per minute without overflowing. Water from the downspout enters the 4 inch pvc pipe and flows directly into the 55 gallon container. As the pre-set space in the 55 gallon container fills; the air vent allows the air inside to escape while the water flowing in displaces it. If there were no vent much of the water would back up and flow into the system before the barrel filled completely during moderate rain-fall events. When the 15 gallon space in the barrel becomes full; the water fills the 4 inch pvc pipe on top until it flows out the pipe on the side. As long as the air vent is higher than the outlet; water will flow out the side pipe. If the air vent leaks or is not "above" the water output the water will just flow out the vent. By the time 15 gallons of water has run off the roof most of the build-up of dust, and organic decaying matter has been washed off the roof surface and is held in the 55 gallon container. The faucet is set to drip slowly enough to allow the 55 gallon container to fill but also allow the 55 gallon container to empty after the rain stops. A 90 degree fitting attached to the output pipe pointing downward on the inside of the 4 inch pvc (added July 2008), keeps all of the first flush water out of the system.

It is important to note that this first flush diverter will reduce, BUT NOT ELIMINATE, disease causing organisms and harmful chemicals from roofwater. Water runoff from a roof can contain many different kinds of substances.Some roof surfaces can produce water that is very safe, while other types of surfaces can produce poisionous water. Also, please note that this design may not work in areas where rainfall is extremely heavy (more than several inches per hour) - the pipes are not of sufficient diameter to carry the resulting flow of water. A good explantion of roof water quality can be found here. If there is some question as to whether or not bacteria will build up in the water that does not drain regularly and spill over into the cleaner output water; note that after 6 months of operation the water from the diverter contained significantly less coliform bacteria - 82 percent less. The tests shown on this site demonstrate this quite clearly. Even with this, since there is no physical seal when the temporary storage fills up during a rain event, it would be a good idea to completely drain and clean out the 55 gallon container at least twice a year (easily done by opening the cleanout valve).

The diverter with the wooden top was sealed with silicone I. All the input and output openings must be sealed or the device will leak. (You might ask why that silly looking air vent with the little hat-like thing on it? Do I really need that? The answer is yes you do. Since the barrel is air tight - without a vent in the top it won't fill correctly. The vent must be higher than your output or the water will simply pour out the vent and never even make it to your output pipe - and the air vent must be sealed where it goes into the wood top. Also a screen over the air vent is a must to keep out mosquitoes and larger objects that might plug it up.The thing works and works well - and its disgard flow rate is easily adjustable.) It has no moving parts (exept the faucet) and nothing to wear out except the screens - if they are stainless steel they will last many years. Set the faucet to drip slowly enough to allow the water to empty between rain periods. I set the rate by watching the water drip out of the downspout after the rain had stopped and the flow from the downspout was typical of what occurs during a very light drizzle, and then set the faucet to approximately the same "drip" rate. In 3 or four days the water level in the 50 gallon container will be down 15 gallons. When any significant rainfall occurs 15 gallons of water will be discarded before any enters the filter with this design. If there is only a light drizzle which is not enough to "wash" the roof none of the water goes into the filter, you don't want it anyway because it has roof chemicals and dissolved dust in it. Where you put the drain faucet will determine how much water is discarded before it is allowed to enter the filter system. If you want to use the disgarded roof water for utility purposes like washing your car or outdoor cleaning you can have the faucet drain into a small container that allows the excess water to fill another storage container. This design is adapted to the rainfall in this area which is usually not concentrated and heavy, but light and continuous. If you live in an area where there are periods of very heavy rainfall, you will probably want to include an overflow pipe on the 4 inch input, otherwise the water will flow over the top of the diverter. Also the ouput to your filter or temporary storage may need to be a larger diameter than what is shown in the pictures above. -

At first, I used a recycled container and built the top from cedar scraps. The sealant was seven dollars, the pipes were ten dollars, the wood ten dollars and the faucets seven dollars. Most commercially available diverters are expensive and have many things that can go wrong. One example of a common problem is when the flow through the diverter becomes blocked by leaves and/or other organic particles. The cleaning process should be very quick and simple. This diverter is very easy to clean. The screens stop nearly all of the debris and the reset drain does not plug up and can be easliy and quickly adjusted, (or replaced with another faucet for about 7 dollars) and the disgarded water can be used for utility purposes. To use the diverter shown here you don't even need to do any thing to the roof gutter, in fact you would not even need to go up on the roof to set one of these up. The one shown here works just fine and could be made to look much better with a little paint. (2009-08-25) A different barrel with a sealed top is now being used. The silicone seal is not easy to keep tight as the wood expands and contracts with varying moisture content and the silicon has cracked several times, and in freezing weather the entire wood top has been broken loose. Cleaning out the screens takes about 5 minutes, and with a drain on the bottom the inside of the barrel can also be cleaned out and all you have to do is open the faucet on the very bottom and let it drain till it is empty - all the muck inside drains out the bottom. -

new water test results-

First flow diverter picture. Note the output pipe has been changed to inch-and-a-half diameter pipe (as of November 11 2009). This allows much more water to flow into storage. This system was tested and will take 24 liters per minute of flow. -

A person might ask: Why use a diverter, I thought rainwater was pure? I look at the water from my roof and it is perfectly clear and looks good. Whats up with this diverter thing? -

Rainwater is not pure - anymore; although it may be much cleaner in non-industrialized areas. Any pollution that rises into the upper atmosphere where clouds form will be present at times (depending on the wind velocity and direction) in the rainwater collected from your roof Since upper atmospheric winds can bring pollution from thousands of miles away (even from the other side of the earth).1,2 -

(back to introduction) -

There is virtually nowhere on earth, now, where rainwater is "pure" in the sense of free from man made substances. Any surface water will contain man made pollutants, even water taken from reservoirs used for public water supply systems. Many of these pollutants, particularly heavy metals like lead and mercury, build up in soil and water - including the water in reservoirs that supply water to millions of people. But more importantly; any smoke, dust, vehicle exhuast, soot, or contaminated water vapour that is released into the "air" near your roof will also be in the water collected from your roof, but most likely in far higher concentrations than the pollution from thousands of miles away - unless your roof is many miles away from any large city or coal fired power plant. All this poison collects on any surface including your roof. The sun heats up your roof and the poisons that are on it, producing many more poisonous compounds. The upside to this whole thing is that water is a wonderful solvent. As the first rain after a dry spell hits your roof much of this pollution is washed off the surface of the roof. This tainted water will also flow into your filter - that is unless you have a diverter to force the most polluted part of the water away from your system. That is what the first flush (or first flow) diverter does. It allows the most polluted water to be disgarded in favor of the far less polluted water that runs off the washed surface. The downside to all this is that from millions of square feet (probalby more like tens of billions of square feet - the previous link here shows 163 million square feet of impervious surface in one county in one state in the U.S. over ten years ago) of impervious surfaces including roofs, blacktop(roads and freeways loaded with tire dust and oil) and cement, runs all the pollution we produce that can be picked up by water - which is most. In most cases this runoff goes directly into rivers, streams, and eventually the ocean. One advantage of collecting water from your roof is that you dont get the oil that comes from automobiles and trucks on the highway, and less of the tire dust. (Did you ever wonder where the tread on the tires of your car goes as they wear? or how many tons of that tire dust goes into the air and water near your house?) Another advantage is that by collecting and temporarily storing roof water, particularly in urban areas, much of the surge of storm water is held back reducing the flow of storm water into streams, rivers, and lakes, thereby reducing the quantity of pollution flowing into the surrounding bodies of water (fast flowing overfilled streams and rivers break up soil and pick up more pollutants than non turbulent waters). In many areas, pollution from storm water is a major problem and is destroying ecosystems, killing fish, and making people sick.-

My point here is twofold: use a diverter; and THINK. Think very carefully about what is being put into the water our grandchildren will eventually drink. Think about participation in non-sustainable activities which give you your "comforts", yet produce many carcinogenic chemicals that bio-accumulate in plants and people. Try to understand that the same science that has given us all our modern conveniences including increased food production, advanced medical care, and thousands of consumer products is now telling us about the true cost of these things: the health issues due to toxic man made chemicals just about everywhere on earth. -

-

You will definately want a screen in the diverter input:-

diverter screen

gutter line-

gutter line

diverter parts-

diverter screen-

Inside view of the 4 inch pvc


output and screens-

Inside view of the 4 inch pvc with 90 degree fitting and screens installed (the 4 inch pvc can be filled with pea gravel but it is more difficult to clean)



Below is shown how to convert a 55 gallon barrel (with a top already included) into a first flush diverter:-

hole saw and container-

The container must be air tight (water tight - make sure the two original threaded caps are sealed tightly - wrap the threads with plumbers tape and tighten them down securely). Use a pvc male adapter for the water input (a 1 1/4 inch is shown here but a 1 1/2 inch has the same thread size and will handle more flow). A 1 1/2 inch hole saw will make a hole almost the right size for the male adapter threads. The "o" ring is there to provide a seal. Also use "teflon tape" often called "plumbers tape" to seal the threads on the adapter.


adapter installation-

The hole will need to be slightly enlarged to make the pvc male adapter "thread" into the hole. This is a bit tricky. I used the "fine" section of a half-round wood rasp to SLIGHTLY enlarge the hole after drilling it with the 1 1/2 inch hole saw. If you have ever used a tap you will understand that the pilot hole cannot be too big or the whole thing is ruined. Take it slow and only file a very slight amount. It will take some forceful pushing to tap the plastic hole with the pvc adapter but it does work. Be careful so the file is not dropped into the barrel!


adapter installation complete-

This shows the adapter installed. Make sure it is tight. The 4 inch pvc assembly shown in the wood top version is used here. Connect it with 1 1/2 inch pvc pipe. I would suggest gluing one of the connections between the input and the pvc adapter.


diverter with original top-

This shows the input (the same input that is shown in the wood top version) installed with a 2X6 support between the base and the top of the barrel. The vent is installed using a 1/2 inch male adapter and the hole to thread that in is drilled with a 3/4 inch spade bit. The drain faucet is installed the same way the vent is installed. The 3/4 inch spade bit drills a hole just the right size to "tap" the threads of a 1/2 inch faucet into the plastic barrel. Be sure to use an o ring washer and plumbers tape to insure a good seal. I have tested this and it works. The output on the side of the 4 inch pvc should be several inches higher if used in areas where very heavy rainfall occurs - and remember that the vent must be higher than the output. (it works fine here where rainfall is very seldom heavy) This will divert up to 55 gallons of water depending on where the "Drain" faucet (see drawing) is installed. This one is set up to divert 20 gallons. I used an electric drill but this could all be done without the use of any electricty with a brace and bit. The barrel cost 35 dollars, and the pvc pipe, o rings, screen material, and fittings were under 20 dollars. Some paint would make the whole thing look much better - still way under 100 dollars. Be sure the diverter is drained if freezing weather is anticipated



Below are pictures of rain water runoff from a composition roof shown at different stages of filtering. This roof holds moss, leaves, and fir tree needles in abundance. Each picture is of different water using the same container. This same comparison is very different if the water is viewed in a smaller glass container (see below). water sample pre diverter pre filter-

Water straight from the downspout (downspout water).


water sample post diverter pre filter-

Water to be filtered. This is from the diverter output (diverter water).


post diverter post filter-

Water from the diverter output after being run through the slow sand filter (filtered water).



water sample pre diverter pre filter-

(downspout water).


water sample post diverter pre filter-

(diverter water).


post diverter post filter-

(filtered water).


1. Export of atmospheric mercury from Asia. Daniel Jaffe, Eric Prestbob, Phil Swartzendruber, Peter Weiss-Penzias, Shungo Katoc, Akinori Takamid, Shiro Hatakeyamad, Yoshizumi Kajiic;-

Interdisciplinary Arts and Sciences, University of Washington-Bothell, Bothell, WA 98011 8246, USA.-

Atmospheric Environment 39 (2005) 3029-3038. Received 11 October 2004; accepted 2 January 2005. (available online at www.sciencedirect.com)-

2. Long-range transport of Siberian biomass burning emissions and impact on surface ozone in western North America. Dan Jaffe,1 Isaac Bertschi,1 Lyatt Jaegle,2 Paul Novelli,3 Jeffrey S. Reid,4 ´ Hiroshi Tanimoto,5 Roxanne Vingarzan,6 and Douglas L. Westphal4. -

GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L16106, doi:10.1029/2004GL020093, 2004-

Received 26 March 2004; revised 12 June 2004; accepted 19 July 2004; published 20 August 2004.


Clean water from filter[edit source]

Clean water from the filter Water sample This is after 2 1/2 weeks of running. The water is now coming out clear.



water sample in glass-

Water Sample

water sample-

water before going through the filter (this is from a storage barrell full of stagnant roof water)-

water sample 2-

This is after the water has been run through the filter


Input without coarse screen[edit source]

Secondary input screen The input on the top from the top. There are 2 screens in there. One is a coarse screen and the other in the center is a fine screen. They are both available at most hardware stores. The small screen in the center is between two washers. You will need to make this one. Witout a screen the baffle pipes will plug up in a very short time. It is much easier to clean out the screens than the baffle pipes.



input screen assembly Input screen assembly with coarse filter removed top view


Fine screen[edit source]

Close up of secondary input screen This is just a pvc threaded reducer adapter. You will need to turn the threads down several thousandths on a lathe for it to screw into the large reducer. I had to turn the washers down in a lathe to make a groove for the samll screen, and then rivet them together with brass pins. A screen that just fits into the adapter would work just as well.



input screen assembly Small screen


Baffle pipe design[edit source]

Baffle pipes The construction is obvious, with the exception of the small holes drilled in each pipe to gently let the water flow into the top of the filter. Don't glue the pipes; they will be very difficult to clean if you do.



baffle pipes Baffle pipes


Recent Modifications[edit source]

Baffle pipes - and recent modifications

The construction is obvious, with the exception of the small holes drilled in each pipe to gently let the water flow into the top of the filter. Don't glue the pipes; they will be very difficult to clean if you do.



baffle pipes-

Baffle pipe modification note the beveling of the sharp edges-

-

baffle pipes-

Baffle pipe modification note the beveling of the sharp edges and the 2 extra rows of holes drilled.

bucket feed-

A 5 gallon bucket on top, in place of the 4 inch pvc, with a very small hole in the bottom will allow the filter to run for quite some time. I used the same drill as on the baffle pipes. A cloth on top keeps the small hole from getting plugged by small organic particles. This is made from things I had on hand. Most of the material is of very low cost. These buckets can be found for free without lids; however be sure you know what was in them originally - food grade containers are recommended.-

2007-08-21: The sand used in the filter has been changed. Now the top layer of fine sand is graded quartz silica sand: .15 mm effective size. This will give better filtering and allow the biofilm to form more effectively; and this sand is very easy to wash - it runs clean in just a few minutes of washing. Don't let the silica thing scare you; just be very careful and don't breathe the dust - I would suggest wearing a protective mask while you clean the sand. Wet silica sand is harmless and is used in many water filters. -

A word here about sand:Be absolutely certain of what is in the sand you use. Know exactly where it comes from. There could be any kind of harmful substance in sand - asbestos (naturally occuring), petroleum distillates (from runoff), arsenic (naturally occuring) pesticides and/or herbicides (runoff from urban areas) the list goes on . . . . If you are not sure where to get "pure sand" check for nsa/ansi 61 or awwa b100 certification.-

2007-09-01: The top layer of sand down to 2 inches of coarse sand above the gravel has been changed to 2 inches of fine sand with 25 inches of graded sand (effective size .15mm) on top of that. I have added the bucket on top so the water can flow through the filter for quite some time without constant monitoring. I suppose a 10 gallon bucket could also be used which would allow water to flow through the filter for much longer. It would only have to be filled once a day. This graded sand is an off-white color so it is easy to see when the bio-layer has formed. The sand on top will turn greenish brown - looks like pond-scum but actually it is a very good thing - it is nature's filtering system and it works. The most recent test demonstrates that fact - the filter removes enough of the bacteria in the roof runoff water such that none are found in the 100 ml samples. This modified version of the first design has a flow rate of 3 gallons per hour. This is a low flow but the water that comes out is clean. A more substantial flow could be produced by using coarser sand and / or having more water on top of the sand, but the water may not be as clean. Four of these at each corner of a house at a downspout would supply 12 gallons per hour during each rain event.-

This is quite sustainable technology. Most of the filter is made utilizing already existing products. This filter sand will be usefull for five or six years, at which time the sand may have to be replaced. The used sand will go into the vegetable garden, where it will be used, mixed together with compost, to grow food, and flowers. The rest of the filter, if kept out of direct sunlight, will be usefull for many years.-

We are now working on a slightly less sustainable, but much more convenient system. This set up uses a small 12 volt rv faucet pump (ideally powered by solar panels) to recirculate water from the filter that is stored in a 45 gallon storage tank. This water is fed back into the filter at several gallons per hour, therby maintaining a supply of oxygenated water to keep the biofilm alive. A faucet or outlet (which has not yet been installed) about 3/4 of the way down on the storage tank will allow water to be collected until the level goes to below the faucet; then water will be recirculated but not available until more water is added to the system. This will be particularly useful in the summer when temperature rises and less oxygen is available in the water, but more sunlight is available to power the pump. The question is: will there be enough organic matter in the circulated water to keep the proper population of microbes alive in the biofilm? Possibly. If occasional 5 gallon quantities of untreated water are added regularly, the filter should function properly. The water will be tested and I will post the results when they are available. -

Feb 28 2008: The most recent test strongly suggests the biofilm can be maintained in this way. -

water recirculation set up-

A 45 gallon storage tank added (smaller barrel on the right) stores the water that has gone through the filter. From there it is pumped back into the filter at 3.5 gallons per hour using a small dc powered pump. This keeps the oxygen supply available to the biofilm. There is an outlet in the storage barrel to catch the filtered re-circulated water for use. -

dc powered water pump-

This is the pump that I have used to circulate the water. It is powered by a 12 volt deep-cycle marine battery, which can easily be kept charged up (ideally) by a solar panel, or a small battery charger. It can also be used to supply pressurized water to your house while also recirculating the water if you have a much larger storage tank - just use two valves on a tee - (one for the low flow and the other to your water supply) , since the water being pumped back into the filter is already cleaned. There are probably as many ways to do this as there are plumbers in your neighborhood.-

3 gallons per hour flow rate-

The picture above shows what a "3.5 gallons per hour" flow looks like. -

filtered water-

Outlet and filtered water flow from storage tank-

potable water-

Clean water!-

These filters work. And they work well. The water from this filter is better than our well water. It would not surprise me if this water was better than most "tap" water in large cities. The water tastes like bottled water that one pays for at the store. But this system produces no left over plastic bottles, and for the price you would pay for four or five cases of "top quality" bottled water, you can probably build this entire filter. If you buy bottled water year round you could easly pay for the battery, pump, storage barrels and filter for less than it would cost you for the bottled water. Then all your water is free. But you don't even need the pump or battery. If you are living in one of the many areas in the U.S. that are now experiencing 50 or 100 year droughts you may want to consider this seriously . . . build it and have it ready for the first rain, and you will have all the water you need to drink, or water your flowers or wash your car . . . what ever - it's your water. Just remember that the filter must be in operation for at least 4 weeks before the water from it is safe to drink - and be sure to have the water tested before you ever drink any of it I cannot stress this enough. Also, any chemicals you have put on your roof will be in the water you collect. (A "first flush diverter" may help to minimize chemicals dissolved in water collected from a roof) Incidentally those chemicals will eventually end up in water anyway (in lesser concentration) because they flow off your roof into the ground and eventually back into a river or acquifer. In fact, any chemicals you have on your roof - moss killers, petro chemical distillates from shingles, lead residue from vent seals and dust from air pollution, get washed off your roof and into the ground where they build up and eventually run off into surface water - which in turn ends up in rivers, lakes, and streams, and will eventually find their way into your grandchildren's water supply. If you have a surface well you are probably already drinking these chemicals. Public water supply systems cost millions of dollars because they attempt to (and usually do) remove chemicals and bacteria from surface water (the source of public water) Maybe if we all were taking water from our roofs to drink we would think more about what we are putting into our water and on our roofs. -

An 1800 square foot roof will collect over 2200 gallons of water with 2 inches of rainfall. If you have 6 downspouts equally spaced that means each one will deliver over 300 gallons of water. This whole thing assumes you are smart enough to read all the links provided on this site and do a little reading on water quality so you understand the risks involved. You don't need a college degree to be smart enough to figure out how to be careful and how to operate one of these filters. The basic operation is simple. The God given ecosphere of this earth cleans water for us with natural processes that work in these filters much in much the same way wetlands clean water for us. (Too bad many wetlands are now covered with asphalt or drained or filled with toxic chemical waste.) The biofilm that grows on the sand eats nasty bacteria and viruses and forms a membrane that only allows water to pass throught it. These filters (much larger of course) are used in Europe extensively for municiple water supplies. The problem is they don't support chemical companies because they don't require any chemicals to operate, and they cannot provide as much water as fast as it is needed for life in the fast lane U.S.A. style. . Go figure.


JUNE 1 2008: NEW FILTER DESIGN[edit source]

Baffle pipes - and recent modifications The construction is obvious, with the exception of the small holes drilled in each pipe to gently let the water flow into the top of the filter. Don't glue the pipes; they will be very difficult to clean if you do.



baffle pipes-

Baffle pipe modification note the beveling of the sharp edges-

-

baffle pipes-

Baffle pipe modification note the beveling of the sharp edges and the 2 extra rows of holes drilled.

bucket feed-

A 5 gallon bucket on top, in place of the 4 inch pvc, with a very small hole in the bottom will allow the filter to run for quite some time. I used the same drill as on the baffle pipes. A cloth on top keeps the small hole from getting plugged by small organic particles. This is made from things I had on hand. Most of the material is of very low cost. These buckets can be found for free without lids; however be sure you know what was in them originally - food grade containers are recommended.-

2007-08-21: The sand used in the filter has been changed. Now the top layer of fine sand is graded quartz silica sand: .15 mm effective size. This will give better filtering and allow the biofilm to form more effectively; and this sand is very easy to wash - it runs clean in just a few minutes of washing. Don't let the silica thing scare you; just be very careful and don't breathe the dust - I would suggest wearing a protective mask while you clean the sand. Wet silica sand is harmless and is used in many water filters. -

A word here about sand:Be absolutely certain of what is in the sand you use. Know exactly where it comes from. There could be any kind of harmful substance in sand - asbestos (naturally occuring), petroleum distillates (from runoff), arsenic (naturally occuring) pesticides and/or herbicides (runoff from urban areas) the list goes on . . . . If you are not sure where to get "pure sand" check for nsa/ansi 61 or awwa b100 certification.-

2007-09-01: The top layer of sand down to 2 inches of coarse sand above the gravel has been changed to 2 inches of fine sand with 25 inches of graded sand (effective size .15mm) on top of that. I have added the bucket on top so the water can flow through the filter for quite some time without constant monitoring. I suppose a 10 gallon bucket could also be used which would allow water to flow through the filter for much longer. It would only have to be filled once a day. This graded sand is an off-white color so it is easy to see when the bio-layer has formed. The sand on top will turn greenish brown - looks like pond-scum but actually it is a very good thing - it is nature's filtering system and it works. The most recent test demonstrates that fact - the filter removes enough of the bacteria in the roof runoff water such that none are found in the 100 ml samples. This modified version of the first design has a flow rate of 3 gallons per hour. This is a low flow but the water that comes out is clean. A more substantial flow could be produced by using coarser sand and / or having more water on top of the sand, but the water may not be as clean. Four of these at each corner of a house at a downspout would supply 12 gallons per hour during each rain event.-

This is quite sustainable technology. Most of the filter is made utilizing already existing products. This filter sand will be usefull for five or six years, at which time the sand may have to be replaced. The used sand will go into the vegetable garden, where it will be used, mixed together with compost, to grow food, and flowers. The rest of the filter, if kept out of direct sunlight, will be usefull for many years.-

We are now working on a slightly less sustainable, but much more convenient system. This set up uses a small 12 volt rv faucet pump (ideally powered by solar panels) to recirculate water from the filter that is stored in a 45 gallon storage tank. This water is fed back into the filter at several gallons per hour, therby maintaining a supply of oxygenated water to keep the biofilm alive. A faucet or outlet (which has not yet been installed) about 3/4 of the way down on the storage tank will allow water to be collected until the level goes to below the faucet; then water will be recirculated but not available until more water is added to the system. This will be particularly useful in the summer when temperature rises and less oxygen is available in the water, but more sunlight is available to power the pump. The question is: will there be enough organic matter in the circulated water to keep the proper population of microbes alive in the biofilm? Possibly. If occasional 5 gallon quantities of untreated water are added regularly, the filter should function properly. The water will be tested and I will post the results when they are available. -

Feb 28 2008: The most recent test strongly suggests the biofilm can be maintained in this way. -

water recirculation set up-

A 45 gallon storage tank added (smaller barrel on the right) stores the water that has gone through the filter. From there it is pumped back into the filter at 3.5 gallons per hour using a small dc powered pump. This keeps the oxygen supply available to the biofilm. There is an outlet in the storage barrel to catch the filtered re-circulated water for use. -

dc powered water pump-

This is the pump that I have used to circulate the water. It is powered by a 12 volt deep-cycle marine battery, which can easily be kept charged up (ideally) by a solar panel, or a small battery charger. It can also be used to supply pressurized water to your house while also recirculating the water if you have a much larger storage tank - just use two valves on a tee - (one for the low flow and the other to your water supply) , since the water being pumped back into the filter is already cleaned. There are probably as many ways to do this as there are plumbers in your neighborhood.-

3 gallons per hour flow rate-

The picture above shows what a "3.5 gallons per hour" flow looks like. -

filtered water-

Outlet and filtered water flow from storage tank-

potable water-

Clean water!-

These filters work. And they work well. The water from this filter is better than our well water. It would not surprise me if this water was better than most "tap" water in large cities. The water tastes like bottled water that one pays for at the store. But this system produces no left over plastic bottles, and for the price you would pay for four or five cases of "top quality" bottled water, you can probably build this entire filter. If you buy bottled water year round you could easly pay for the battery, pump, storage barrels and filter for less than it would cost you for the bottled water. Then all your water is free. But you don't even need the pump or battery. If you are living in one of the many areas in the U.S. that are now experiencing 50 or 100 year droughts you may want to consider this seriously . . . build it and have it ready for the first rain, and you will have all the water you need to drink, or water your flowers or wash your car . . . what ever - it's your water. Just remember that the filter must be in operation for at least 4 weeks before the water from it is safe to drink - and be sure to have the water tested before you ever drink any of it I cannot stress this enough. Also, any chemicals you have put on your roof will be in the water you collect. (A "first flush diverter" may help to minimize chemicals dissolved in water collected from a roof) Incidentally those chemicals will eventually end up in water anyway (in lesser concentration) because they flow off your roof into the ground and eventually back into a river or acquifer. In fact, any chemicals you have on your roof - moss killers, petro chemical distillates from shingles, lead residue from vent seals and dust from air pollution, get washed off your roof and into the ground where they build up and eventually run off into surface water - which in turn ends up in rivers, lakes, and streams, and will eventually find their way into your grandchildren's water supply. If you have a surface well you are probably already drinking these chemicals. Public water supply systems cost millions of dollars because they attempt to (and usually do) remove chemicals and bacteria from surface water (the source of public water) Maybe if we all were taking water from our roofs to drink we would think more about what we are putting into our water and on our roofs. -

An 1800 square foot roof will collect over 2200 gallons of water with 2 inches of rainfall. If you have 6 downspouts equally spaced that means each one will deliver over 300 gallons of water. This whole thing assumes you are smart enough to read all the links provided on this site and do a little reading on water quality so you understand the risks involved. You don't need a college degree to be smart enough to figure out how to be careful and how to operate one of these filters. The basic operation is simple. The God given ecosphere of this earth cleans water for us with natural processes that work in these filters much in much the same way wetlands clean water for us. (Too bad many wetlands are now covered with asphalt or drained or filled with toxic chemical waste.) The biofilm that grows on the sand eats nasty bacteria and viruses and forms a membrane that only allows water to pass throught it. These filters (much larger of course) are used in Europe extensively for municiple water supplies. The problem is they don't support chemical companies because they don't require any chemicals to operate, and they cannot provide as much water as fast as it is needed for life in the fast lane U.S.A. style. . Go figure.


Water test results[edit source]

Baffle pipes - and recent modifications The construction is obvious, with the exception of the small holes drilled in each pipe to gently let the water flow into the top of the filter. Don't glue the pipes; they will be very difficult to clean if you do.



baffle pipes-

Baffle pipe modification note the beveling of the sharp edges-

-

baffle pipes-

Baffle pipe modification note the beveling of the sharp edges and the 2 extra rows of holes drilled.

bucket feed-

A 5 gallon bucket on top, in place of the 4 inch pvc, with a very small hole in the bottom will allow the filter to run for quite some time. I used the same drill as on the baffle pipes. A cloth on top keeps the small hole from getting plugged by small organic particles. This is made from things I had on hand. Most of the material is of very low cost. These buckets can be found for free without lids; however be sure you know what was in them originally - food grade containers are recommended.-

2007-08-21: The sand used in the filter has been changed. Now the top layer of fine sand is graded quartz silica sand: .15 mm effective size. This will give better filtering and allow the biofilm to form more effectively; and this sand is very easy to wash - it runs clean in just a few minutes of washing. Don't let the silica thing scare you; just be very careful and don't breathe the dust - I would suggest wearing a protective mask while you clean the sand. Wet silica sand is harmless and is used in many water filters. -

A word here about sand:Be absolutely certain of what is in the sand you use. Know exactly where it comes from. There could be any kind of harmful substance in sand - asbestos (naturally occuring), petroleum distillates (from runoff), arsenic (naturally occuring) pesticides and/or herbicides (runoff from urban areas) the list goes on . . . . If you are not sure where to get "pure sand" check for nsa/ansi 61 or awwa b100 certification.-

2007-09-01: The top layer of sand down to 2 inches of coarse sand above the gravel has been changed to 2 inches of fine sand with 25 inches of graded sand (effective size .15mm) on top of that. I have added the bucket on top so the water can flow through the filter for quite some time without constant monitoring. I suppose a 10 gallon bucket could also be used which would allow water to flow through the filter for much longer. It would only have to be filled once a day. This graded sand is an off-white color so it is easy to see when the bio-layer has formed. The sand on top will turn greenish brown - looks like pond-scum but actually it is a very good thing - it is nature's filtering system and it works. The most recent test demonstrates that fact - the filter removes enough of the bacteria in the roof runoff water such that none are found in the 100 ml samples. This modified version of the first design has a flow rate of 3 gallons per hour. This is a low flow but the water that comes out is clean. A more substantial flow could be produced by using coarser sand and / or having more water on top of the sand, but the water may not be as clean. Four of these at each corner of a house at a downspout would supply 12 gallons per hour during each rain event.-

This is quite sustainable technology. Most of the filter is made utilizing already existing products. This filter sand will be usefull for five or six years, at which time the sand may have to be replaced. The used sand will go into the vegetable garden, where it will be used, mixed together with compost, to grow food, and flowers. The rest of the filter, if kept out of direct sunlight, will be usefull for many years.-

We are now working on a slightly less sustainable, but much more convenient system. This set up uses a small 12 volt rv faucet pump (ideally powered by solar panels) to recirculate water from the filter that is stored in a 45 gallon storage tank. This water is fed back into the filter at several gallons per hour, therby maintaining a supply of oxygenated water to keep the biofilm alive. A faucet or outlet (which has not yet been installed) about 3/4 of the way down on the storage tank will allow water to be collected until the level goes to below the faucet; then water will be recirculated but not available until more water is added to the system. This will be particularly useful in the summer when temperature rises and less oxygen is available in the water, but more sunlight is available to power the pump. The question is: will there be enough organic matter in the circulated water to keep the proper population of microbes alive in the biofilm? Possibly. If occasional 5 gallon quantities of untreated water are added regularly, the filter should function properly. The water will be tested and I will post the results when they are available. -

Feb 28 2008: The most recent test strongly suggests the biofilm can be maintained in this way. -

water recirculation set up-

A 45 gallon storage tank added (smaller barrel on the right) stores the water that has gone through the filter. From there it is pumped back into the filter at 3.5 gallons per hour using a small dc powered pump. This keeps the oxygen supply available to the biofilm. There is an outlet in the storage barrel to catch the filtered re-circulated water for use. -

dc powered water pump-

This is the pump that I have used to circulate the water. It is powered by a 12 volt deep-cycle marine battery, which can easily be kept charged up (ideally) by a solar panel, or a small battery charger. It can also be used to supply pressurized water to your house while also recirculating the water if you have a much larger storage tank - just use two valves on a tee - (one for the low flow and the other to your water supply) , since the water being pumped back into the filter is already cleaned. There are probably as many ways to do this as there are plumbers in your neighborhood.-

3 gallons per hour flow rate-

The picture above shows what a "3.5 gallons per hour" flow looks like. -

filtered water-

Outlet and filtered water flow from storage tank-

potable water-

Clean water!-

These filters work. And they work well. The water from this filter is better than our well water. It would not surprise me if this water was better than most "tap" water in large cities. The water tastes like bottled water that one pays for at the store. But this system produces no left over plastic bottles, and for the price you would pay for four or five cases of "top quality" bottled water, you can probably build this entire filter. If you buy bottled water year round you could easly pay for the battery, pump, storage barrels and filter for less than it would cost you for the bottled water. Then all your water is free. But you don't even need the pump or battery. If you are living in one of the many areas in the U.S. that are now experiencing 50 or 100 year droughts you may want to consider this seriously . . . build it and have it ready for the first rain, and you will have all the water you need to drink, or water your flowers or wash your car . . . what ever - it's your water. Just remember that the filter must be in operation for at least 4 weeks before the water from it is safe to drink - and be sure to have the water tested before you ever drink any of it I cannot stress this enough. Also, any chemicals you have put on your roof will be in the water you collect. (A "first flush diverter" may help to minimize chemicals dissolved in water collected from a roof) Incidentally those chemicals will eventually end up in water anyway (in lesser concentration) because they flow off your roof into the ground and eventually back into a river or acquifer. In fact, any chemicals you have on your roof - moss killers, petro chemical distillates from shingles, lead residue from vent seals and dust from air pollution, get washed off your roof and into the ground where they build up and eventually run off into surface water - which in turn ends up in rivers, lakes, and streams, and will eventually find their way into your grandchildren's water supply. If you have a surface well you are probably already drinking these chemicals. Public water supply systems cost millions of dollars because they attempt to (and usually do) remove chemicals and bacteria from surface water (the source of public water) Maybe if we all were taking water from our roofs to drink we would think more about what we are putting into our water and on our roofs. -

An 1800 square foot roof will collect over 2200 gallons of water with 2 inches of rainfall. If you have 6 downspouts equally spaced that means each one will deliver over 300 gallons of water. This whole thing assumes you are smart enough to read all the links provided on this site and do a little reading on water quality so you understand the risks involved. You don't need a college degree to be smart enough to figure out how to be careful and how to operate one of these filters. The basic operation is simple. The God given ecosphere of this earth cleans water for us with natural processes that work in these filters much in much the same way wetlands clean water for us. (Too bad many wetlands are now covered with asphalt or drained or filled with toxic chemical waste.) The biofilm that grows on the sand eats nasty bacteria and viruses and forms a membrane that only allows water to pass throught it. These filters (much larger of course) are used in Europe extensively for municiple water supplies. The problem is they don't support chemical companies because they don't require any chemicals to operate, and they cannot provide as much water as fast as it is needed for life in the fast lane U.S.A. style. . Go figure.


contact the author[edit source]

The author is a graduate of the University of Washington (class of 2006) with an interdisciplinary degree in Environmental Science, and additionally has 28 years of professional experience in industry including 25 years restoring antique clocks, 3 years of experience as an electronics technician and 2 years as a part time math instructor. fifteen