Using Single Pass or Recirculating Septic Media Filters InspectAPedia® -
Using Single Pass Septic Media Filters as Components of Alternative Septic Systems
UsingRecirculating Septic Media Filters
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This document discusses the single pass and recirculating septic media filter systems.
Media filter septic systems use a conventional septic
tank followed by any of several methods to further filter and treat septic effluent before it is discharged to
the soil, soil surface, or waterway.
Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted. Use of this information at other websites, in books or pamphlets for sale is reserved
to the author. Technical review by industry experts has been performed and is ongoing - reviewers welcomed and are listed at "References."
Single pass media filers using sand, other natural septic filter media or manufactured/synthetic media filter media,
are usually designed for effluent to
be applied (dosed) using a pressure distribution system, typically a small-diameter perforated pipe.
The single pass septic media filter design permits
effluent to be applied to the filter uniformly, in small, regular doses, permitting the filtering and biomat processes
to do their work and avoiding overloading the system.
A recirculating septic media filter system, in general, may be constructed using the same materials discussed
throughout this document. What's different?
A recirculating media filter system will be water tight (commonly using 30-mil polyvinyl chloride plastic (PVC) - so that it can process and then recirculate the effluent back to the
pumping station.
Effluent cycles through the recirculating media filter a specified number of times before being later
discharged to a dispersal system. A common design to make final disposal of the effluent
uses a pressure distribution system to disperse effluent into the soil.
Where high levels of treatment of the effluent are achieved
(see below), a biomat is not going to form so the absorption system can be expected to have a longer life.
A recirculating effluent septic system, by its ability to handle higher volumes of effluent or
effluent at a higher rate, may be constructed with a much smaller footprint than a single-pass media filter.
Recirculating media filter septic systems may also be better at reducing the nitrogen load in the processed effluent. Jantrania cites
ratios of total recirculating effluent to incoming effluent as ranging from 2:1 to 50:1 depending on system requirements.
A typical recirculating media filter system, if constructed using sand, will be constructed in a watertight excavation
and filled in layers, from the bottom up, 12" of gravel, 24" of coarse sand coarse (0.05-2.0 mm),
topped with another 12" of gravel. The bottom of the recirculating media sand and gravel filter
bed slopes (perhaps 1" in 8 ft) to drain to the return from the media filter to the pumping station. 4" PVC pipe returns
effluent by gravity to the pumping station.
Wastewater is applied to a system of this design usually at 4-5 gallons per square foot
of area of the media filter system's footprint. So a family of four, using 70 gpd of wastewater, (figure 300 gpd total, a
commonly-used number which I am betting is low) would need only 75 sq. ft. for the filter bed if you believe these calculations.
Naturally the actual system will be built with more capacity to handle aging, variations in efficacy, and variations in loading
rate.
A recirculating sand media filter of this design can remove 30% to 70% of the nitrogen in the incoming effluent, and
10 to 30% of the phosphorus in the incoming effluent. BOD may be reduced from 175 mg/L (leaving the septic tank)
to 20; fecal coliform may be reduced from 1 million or much higher MPN/100mL leaving the septic tank to perhaps
5000 to 100,000 MPN/100mL.
A recirculating sand bed media filter system produces highly treated effluent and has good
removal of nitrogen. In part because of the larger sand used in a recirculating system, fecal coliform is not reduced as
effectively as a single pass sand media filter or a peat media filter.
The life expectancy of a recirculating media filter system of this type and the frequency with which the sand needs to be
raked or replaced, is not an easy statistic to find. I'll plug that data in here when I can dig it out from the experts.
Clearly a septic media filter system like this needs regular maintenance and more frequent attention than a conventional septic tank and drainfield.
Figure on a regular maintenance contract with perhaps quarterly inspections of the return media flow (slowing indicates clogging),
returning effluent quality, and proper operation of the pump and controls.
The University of Minnesota Extension Service estimates an
annual operating cost including inspection, maintenance, and electricity of $200.-$500./year. This figure does not appear to include, however,
the cost of periodic replacement of the media.
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References: Portions of the text in this section were based on comments in
"Advanced Onsite Wastewater Systems Technologies", Jantrania and Gross, and others on an article by the
University of Minnesota Extension Service on recirculating sand bed media filter systems
at http://www.extension.umn.edu/distribution/naturalresources/DD7670.html. The two sources are in general agreement.
References for this Septic Media Filters Discussion
Septic Contaminants, identifying - what are the Nitrogen contaminants produced by septic systems and what can be done about them if they escape initial treatment?
Safety: Septic System, Septic Tank, & Cesspool Safety Warnings for Septic Inspectors, Septic Pumpers, and Homeowners
The Septic System Owners's Manual, Lloyd Kahn, Blair Allen, Julie Jones, Shelter Publications, 2000. ISBN 0-936070-20-X - order a copy from the InspectAPedia bookstore (Amazon.com)
Onsite wastewater
treatment systems, Bennette D. Burks & Mary Margaret Minnis. Textbook and reference manual on all aspects of onsite treatment. This is one of the best books we've reviewed on the subject, with an excellent balance of clear simple explanation and solid engineering. Topics: Soil & Site Selection, Hydraulics, System Selection & Design, Wastewater Biology, History & Mythology of Onsite Wastewater
Treatment. $49.95, Hogarth House, Ltd., 800-993-2665 x327 order a copy from the InspectApedia bookstore (Amazon.com) or order by telephone 800 -993-2665 x327 (Univ. Wisc. Bookstore)
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Advanced Onsite Wastewater Systems Technologies, Anish R. Jantrania, Mark A. Gross. Anish Jantrania, Ph.D., P.E., M.B.A., is a Consulting Engineer, in Mechanicsville VA, 804-550-0389
(2006), Advanced Onsite Wastewater Systems Technologies.
Outstanding technical reference especially on alternative septic system design alternatives. Written for designers and engineers, this book is not at all easy going
for homeowners but is a text we recommend for professionals--DF.
AEROBIC SEPTIC SYSTEMS
Builder's Guide to Wells and Septic Systems, Woodson, R. Dodge: $ 24.95; MCGRAW HILL B; TP;
Quoting from Amazon's description: For the homebuilder, one mistake in estimating or installing wells and septic systems can cost thousands of dollars. This comprehensive guide filled with case studies can prevent that. Master plumber R. Dodge Woodson packs this reader-friendly guide with guidance and information, including details on new techniques and materials that can economize and expedite jobs and advice on how to avoid mistakes in both estimating and construction. Chapters cover virtually every aspect of wells and septic systems, including on-site evaluations; site limitations; bidding; soil studies, septic designs, and code-related issues; drilled and dug wells, gravel and pipe, chamber-type, and gravity septic systems; pump stations; common problems with well installation; and remedies for poor septic situations. Woodson also discusses ways to increase profits by avoiding cost overruns.
Country Plumbing: Living with a Septic System, Hartigan, Gerry: $ 9.95; ALAN C HOOD & TP;
Quoting an Amazon reviewer's comment, with which we agree--DF:This book is informative as far as it goes and might be most useful for someone with an older system. But it was written in the early 1980s. A lot has changed since then. In particular, the book doesn't cover any of the newer systems that are used more and more nowadays in some parts of the country -- sand mounds, aeration systems, lagoons, etc.
Design Manuals for Septic Systems
US EPA Onsite Wastewater Treatment Systems Manual [online copy, free] Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm Onsite wastewater treatment and disposal systems,
Richard J Otis, published by the US EPA. Although it's more than 20 years old, this book remains a useful reference for septic system designers.
U.S. Environmental Protection Agency, Office of Water Program Operations; Office of Research and Development, Municipal Environmental Research Laboratory; (1980)
"International Private Sewage Disposal Code," 1995, BOCA-708-799-2300, ICBO-310-699-0541, SBCCI 205-591-1853, available from those code associations.
"Manual of Policy, Procedures, and Guidelines for Onsite Sewage Systems," Ontario Reg. 374/81, Part VII of the Environmental
Protection Act (Canada), ISBN 0-7743-7303-2, Ministry of the Environment,135 St. Clair Ave. West, Toronto Ontario M4V 1P5 Canada $24. CDN.
Manual of Septic Tank Practice, US Public Health Service's 1959.
Onsite Wastewater Disposal Books
Onsite Wastewater Disposal, R. J. Perkins;
Quoting from Amazon: This practical book, co-published with the National Environmental Health Association,
describes the step-by-step procedures needed to avoid common pitfalls in septic system technology.
Valuable in matching the septic system to the site-specific conditions, this useful book will help you install a reliable system in
both suitable and difficult environments. Septic tank installers, planners, state and local regulators, civil and sanitary engineers,
consulting engineers, architects, homeowners, academics, and land developers will find this publication valuable.
Onsite Wastewater Treatment Systems, Bennette D. Burks, Mary Margaret Minnis, Hogarth House 1994 - one of the best septic system books around, suffering a bit from small fonts and a weak index. (DF volunteers to serve as indexer if Burks/Minnis re-publish this very useful volume.)
While it contains some material more technical than needed by homeowners, Burks/Minnis book on onsite wastewater treatment systems a very useful reference
for both property owners and septic system designers. We refer to it often.
While Minnis says the best place to buy this book is at Amazon (our link at left), you can also see this book at Minnis' website at http://web page .pace.edu/MMinnisbook
Septic Tank/Soil-Absorption Systems: How to Operate & Maintain, Equipment Tips, U.S. Department of Agriculture, 8271 1302, 7100 Engineering, 2300 Recreation, September 1982, web search 08/28/2010, original source: http://www.fs.fed.us/t-d/pubs/pdfimage/82711302.pdf
Planting Over Septic System Component", Daniel Friedman (author/editor, InspectAPedia.com), The Innovator, Winter/Spring 2008, BCOSSA, British Columbia OnSite Sewage Association, 201-3542 Blansard St., Victoria BC V8X 1W3 Canada
Septic System Owner's Manual, Lloyd Kahn, Blair Allen, Julie Jones, Shelter Publications, 2000 $14.95 U.S. - easy to understand, well illustrated, one of the best practical references around on septic design basics including some advanced systems; a little short on safety and maintenance. Both new and used (low priced copies are available, and we think the authors are working on an updated edition--DF.
Quoting from one of several Amazon reviews: The basics of septic systems, from underground systems and failures to what the owner can do to promote and maintain a healthy system, is revealed in an excellent guide essential for any who reside on a septic system. Rural residents receive a primer on not only the basics; but how to conduct period inspections and what to do when things go wrong. History also figures into the fine coverage.
Test Pit Preparation for Onsite Sewage Evaluations, State of Oregon Department of Environmental Quality, Portland OR, 800 452-4011. PDF document. We recommend this excellent document that offers detail about soil perc tests, deep hole tests, safety, and septic design. Readers should also see Soil Percolation Tests and for testing an existing septic system, also see Dye Tests
Grass is Always Greener Over the Septic Tank, Bombeck, Erma: $ 5.99; FAWCETT; MM;
This septic system classic whose title helps avoid intimidating readers new to septic systems, is available new or used at very low prices.
It's more entertainment than a serious "how to" book on septic systems design, maintenance, or repair. Not recommended -- DF.
US EPA Onsite Wastewater Treatment Systems Manual Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm
Water Wells and Septic Systems Handbook, R. Dodge Woodson. This book is in the upper price range, but is worth the cost for serious septic installers and designers.
Quoting Amazon: Each year, thousands upon thousands of Americans install water wells and septic systems on their properties. But with a maze of codes governing their use along with a host of design requirements that ensure their functionality where can someone turn for comprehensive, one-stop guidance? Enter the Water Wells and Septic Systems Handbook from McGraw-Hill. Written in language any property owner can understand yet detailed enough for professionals and technical students this easy-to-use volume delivers the latest techniques and code requirements for designing, building, rehabilitating, and maintaining private water wells and septic systems. Bolstered by a wealth of informative charts, tables, and illustrations, this book delivers: * Current construction, maintenance, and repair methods
* New International Private Sewage Disposal Code
* Up-to-date standards from the American Water Works Association
Wells and Septic Systems, Alth, Max and Charlet, Rev. by S. Blackwell Duncan, $ 18.95; Tab Books 1992. We have found this text very useful for conventional well and septic systems design and maintenance --DF.
Quoting an Amazon description:Here's all the information you need to build a well or septic system yourself - and save a lot of time, money, and frustration. S. Blackwell Duncan has thoroughly revised and updated this second edition of Wells and Septic Systems to conform to current codes and requirements. He also has expanded this national bestseller to include new material on well and septic installation, water storage and distribution, water treatment, ecological considerations, and septic systems for problem building sites.
The NSFC Products List has an excellent list of design manuals/modules available from their website or by telephone 800-624-8301
Submissions welcome. send us a suggested document link or request an exchange of website links
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