Aerobic treatment unit final treatment stage details:
Here we explain the final treatment stage of aerobic septic systems or aerobic treatment units, and we suggest sources for designs and products for aerobic septic treatment units (ATUs) for onsite waste disposal, also called fine bubble aeration systems.
We address aerobic septic system design, features, inspection, repair, and maintenance. Product sources are also listed.
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Post Processing or Final Treatment of Aerobic or Aeration Septic System Effluent
Septic effluent, after having been processed through the aerobic treatment unit (ATU), may require further
polishing, such as by a private wetland or greenhouse system, and may also require disinfection such as
by chlorination or UV light.
Other common final ATU effluent treatment systems include sand bed filters,
raised bed septic fields, drip irrigation systems, evaporation/transpiration effluent disposal systems,
or even a conventional septic drainfield.
When all of this processing has been completed, the effluent may be sufficiently
sanitary to permit discharge into a nearby body of water or directly onto the ground surface. In other
circumstances the effluent is discharged into a subsurface system such as a drainfield.
In this last case,
the drainfield or soil absorption system will not need to meet the same treatment requirements as a conventional
septic drain field, because of the pre-processing and sanitizing that have already taken place.
Aerobic or aeration septic systems should have a second settlement chamber at or past the septic tank
Because the treatment tank is continually agitated the level of suspended solids remains high.
Therefore
an aerobic treatment unit will also include a second settling chamber to make sure that solids are not
being sent out to the soil absorption system. Some designs may include a filter at the tank outlet for added
protection of the absorption system. Sludge from the settling chamber is returned to the primary tank for
further treatment.
Chlorine or Calcium Hypochlorite Disinfection for Aerobic or Aeration Septic Systems
Disinfection methods for treated effluent include chlorination or UV light treatment.
Where chlorine tablets are used it is essential that the proper type of tablets are placed into the system (see the two
links below about chlorine tablets, swimming pool chlorine tablets, and calcium hypochlorite tablets (the proper stuff to use).
OPINION DF: Although they may be approved for this application, I have never been completely confident in UV-light disinfection systems for several reasons:
The "install and forget it" image of a UV light treatment system means that owners may never notice that the system has stopped working
Sludge and debris may coat the UV light treatment bulb, shortening its effective life
Any UV light water or wastewater treatment system is limited by the flow-rate of water past the light. If water flows faster than the
design point, treatment will be ineffective. Many systems I've seen installed had no method for limiting or even monitoring the
flow rate past the light.
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Design Alternatives for Septic Systems: Alternate Onsite Wastewater Disposal Designs for Septic Systems - design engineers, consultants, products, books for special problem situations, difficult soils, old system repairs.
Aerobic septic systems, chemical, composting, incinerating & waterless toilets, Evaporation-Transpiration (ET) Septic Systems, septic media filters, greywater systems, holding tank septic systems, mound septics, raised bed septics, pressure dosing septic systems,
sand bed filters, peat beds, constructed wetlands, septic disinfection systems.
Septic SystemReferences & Books
"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.
US HEW, MANUAL of SEPTIC TANK PRACTICE [PDF] 1975, U.S. Department of Health, Education and Welfare, Public Health Servicve, original source: https://nepis.epa.gov/
Manual of Septic Tank Practice, US Public Health Service's 1957, reprinted in 1963, 1967, 1969 and in a 1975 edition given just above.
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). 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 I recommend for professionals--DF.
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, 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 wastewatre 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 buty this book is at Amazon
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
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 priceO 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.
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.
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
In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Carson Dunlop Associates provides extensive home inspection education and report writing material. In gratitude we provide links to tsome Carson Dunlop Associates products and services.