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This septic/sewage information article provides a general discussion of the contents: contaminants, pathogens, components of typical residential septic tank sludge and scum and cites several hazards related to septic tanks and septic tank sewage contents.
We also provide links to more detailed information in articles about nitrogen contamination, how to inspect and test and clean up sewage contamination in buildings, and what to do about a septic system after it has been flooded.
What Makes Up Septic Sludge and Septic Scum in Residential Septic Tanks?
Watch out: sewage spills contain contaminants that can cause serious illness or disease. Disease causing agents in raw sewage include bacteria, fungi, parasites, and viruses and can cause serious illnesses including bacterial infections, Tetanus, Hepatitis A, Leptospirosis, infections by Cryptosporidium & Giardia and gastrointestinal diseases.
Components of Sewage Entering and Leaving the Septic Tank
Sewage, or "blackwater" from a typical residential building contains a variety of inorganic and organic substances contained in feces-fecal residue, urine, and food wastes. Included are digested
food, skin cells from the intestinal lining, bacteria (coliform, other),
other organic waste and debris which may have entered the septic system such as food waste or waste from a garbage grinder; cellulose (dissolved
toilet tissue); Nitrogen, ammonia, nitrite, nitrate, phosphorous, sulfate, grease.
First (detailed sewage pathogen lists follow), stated simply, and according to various sources such as the Utah DEQ
"The major contaminant discharged from septic systems is disease-causing
germs. These germs (bacteria and viruses) - can cause many human diseases.
discharged from septic systems is nitrogen in the form of nitrate. If the nitrate level of drinking
water is too high, infants, up to the age of six months old, can develop a fatal disease called blue baby syndrome (methemoglobenemia).
Additionally, if toxic chemicals are disposed in a septic system, they can percolate through the drainfield and into the ground water."
Jantrania & Gross (see references at the Septic Systems Home Page) list the following as characteristics of raw sewage
Total suspended solids: 155-330 mg/L
5-Day BOD: 155-286 mg/L
Total coliform bacteria: 108 to 1010 CFU/100mL
Fecal coliform bacteria: 106 to 108 CFU/100mL
Ammonimum-nitrogen, N4-N: 4-13 mg/L
Total nitrogen: 26-75 mg/L
Total phosphorus: 6-12 mg/L
(The complete list is in their book)
What are the Components of Septic Tank Effluent
Jantrania & Gross (see references at the Septic Systems Home Page) list the following as characteristics of septic effluent as it leaves the septic tank (where only limited
treatment has occurred).
Total suspended solids: 38-85 mg/L
5-Day BOD: 118-189 mg/L (this is about a 40% reduction from the level of the entering sewage)
Fecal coliform bacteria: 106 to 107 CFU/100mL (note that this little or no reduction over the level of coliform in the entering sewage)
Ammonimum-nitrogen, N4-N: 30-50 mg/L (note that this is considerably higher than their number for raw sewage)
Total nitrogen: 29-63 mg/L
Total phosphorus: 8 mg/L
(The complete list of components of septic tank discharged effluent is in their book)
Details about the effects of key septic or wastewater constituents on soils and water and the environment are at WASTEWATER BIOCOMPATIBILITY.
What is Found in Settled Septic Tank Sludge
To be complete, a conventional septic tank contains settled sludge solids at its bottom, a floating grease/scum layer, and a central volume of liquid effluent and dissolved solids.
Because it is difficult to chemically separate individual sewage components, septic "sludge" is measured in the amount of oxygen needed to support the consumption of the waste by microbes (bacteria and other)
- biochemical oxygen demand or "BOD".
Total solids in this waste (if measured by weighing what's left if
sewage has all of its water content removed) are broken down into: - total suspended solids (able to be removed from effluent by use of a
2.0u filter) - total dissolved solids (dissolved in the liquid and thus pass through the filter)
Solid residue can also be broken down into a volatile solids portion
(which is consumed When a sample is ignited at 550 degC) and fixed solids portion which remains after This process.
Settleable solids, that is solids that settle out of the septic
effluent, are defined as those particles which will settle out of the sewage after a specific time period.
What Contaminants are Found in Floating Septic Tank Scum
Oil and grease in sewage will, in a septic tank and given enough time, will rise to the top of the tank and join the floating scum layer there.
In residential sewage the oil and grease will be primarily from animal or vegetable fats.
What Gases are Found in the Septic Tank
Methane Gas Hazards in septic tanks:
Finally, not really a direct component of septic sludge or floating
scum are the gases, including combustible methane gas, produced by decaying organic matter including sewage.
Readers have sent us reports
of fires, explosions, and even deaths associated with accidental igniting of methane gas over a septic tank or asphyxiation caused by
entering or falling into a septic tank.
See METHANE GAS HAZARDS and other septic system gas explosion or asphyxiation hazards such as hydrogen sulfide. Also see SEPTIC & CESSPOOL SAFETY where we describe septic methane gas asphyxiation and explosion hazards.
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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
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.
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.
Septic & Sewage Pathogens and Contaminants, References & Research Articles
Amahmid, O., Asmama, S., & Bouhoum, K. (1999). The effect of waste water reuse in irrigation on the contamination level of food crops by Giardia cysts and Ascaris eggs. International Journal of Food Microbiology, 49(1-2), 19-26.
Barak, J.D., Whitehand, L.C., & Charkowski, A.O. (2002). Differences in attachment of Salmonella enterica serovars and Escherichia coli O157:H7 to alfalfa sprouts. Applied and Environmental Microbiology, 68(10), 4758-4763.
Beuchat, L.R. (1996). Pathogenic microorganisms associated with fresh produce. Journal of Food Protection, 59(2), 204-216.
Castro-Rosas, J., & Escartin, E.F. (2000). Survival and growth of Vibrio cholerae O1, Salmonella typhi, and Escherichia coli O157:H7 in alfalfa sprouts. Journal of Food Science, 65(1), 162-165.
Charkowski, A.O., Barak, J.D., Sarreal, C.Z., & Mandrell, R.E. (2002). Growth and colonization patterns of Salmonella enterica and Escherichia coli O157:H7 on alfalfa sprouts and the effects of sprouting temperature, iinoculum /in·oc·u·lum/ (-ok´u-lum) pl. inoc´ula material used in inoculation.
Evans, M.R., Ribeiro, C.D., & Salmon, R.L. (2003). Hazards of healthy living: Bottled water and salad vegetables as risk factors for Campylobacter infection. Emerging Infectious Disease, 9(10), 1219-1225.
Frost, J.A., McEvoy, M.B., Bentley, C.A., Andersson, Y., & Rowe, B. (1995). An outbreak of Shigella sonnei infection associated with consumption of iceberg. Emerging Infectious Disease, 1(1), 26-28.
Guo, X., Chen, J., Brackett, R.E., & Beuchat, L.R. (2001). Survival of Salmonellae on and in tomato plants from the time of inoculation at flowering and early stages of fruit development through fruit ripening,
said of meat. See curing. . Applied and Environmental Microbiology, 67(10), 4760-4764.
Guo, X., Chen, J., Brackett, R.E., & Beuchat, L.R. (2002). Survival of Salmonellae on tomatoes stored at high relative humidity, in soil, and on tomatoes in contact with soil. Journal of Food Protection, 65(2), 274-279.
Guo, X., Iersel, M.W.V., Chen, J., Brackett, R.E., & Beuchat, L.R. (2002). Evidence of association of salmonellae with tomato plants grown hydroponically in inoculated nutrient solution. Applied and Environmental Microbiology, 68(7), 3639-3643.
Itoh, Y., Sugita-Konishi, Y., Kasuga, E, Iwaki, M., Hara-Kudo, Y., Saito, N., Noguchi, Y, Konuma, H., & Kumagai, S. (1998) Enterohemorrhagic Escherichia coli enterohemorrhagic Escherichia EHEC Any of the E coli serotypes–eg O29, O39, O145 that produces shiga-like toxins, causing bloody inflammatory diarrhea, evoking a HUS. See Escherichia coli O157:H7, Hemolytic uremic syndrome. O157:H7 present in radish sprouts. Applied and Environmental Microbiology, 64(4), 1532-1535.
Madden, J.M. (1992). Microbial pathogens in fresh produce--The regulatory perspective. Journal of Food Protection, 55, 821-823.
McMahon, M.A.S., & Wilson, I.G. (2001). The occurrence of enteric pathogens and Aeromonas species in organic vegetables. International Journal of Food Microbiology, 70(1-2),155-162.
Puohiniemi, R., Heiskanen, T., & Siitonen, A. (1997). Molecular epidemiology of two international sprout-borne Salmonella outbreaks. Journal of Clinical Microbiology
. 35(10), 2487-2491.
Shearer, A.E., Strapp, C.M., & Joerger, R.D. (2001). Evaluation of polymerase chain reaction-based system for detection of Salmonella enteritidis, Escherichia coli O157:H7, Listeria spp., and Listeria monocytogenes on fresh fruit and vegetables. Journal of Food Protection, 64(6), 788-795.
Takeuchi, K., Hassan, A.N., & Frank, J.F. (2001). Penetration of Escherichia coli O157:H7 into lettuce as influenced by modified atmosphere and temperature. Journal of Food Protection, 64(11), 1820-1823.
Wright, C., Kominos, S.D., & Yee, R.B. (1976). Enterobacteriaceae and Pseudomonas aeruginosa recovered from vegetable salads. Applied and Environmental Microbiology, 31(3), 453-454.
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. 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.
Septic Tank/Soil-Absorption Systems: How to Operate & Maintain [ copy on file as /septic/Septic_Operation_USDA.pdf ] - , 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 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
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.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones