Sewage pathogens:

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.

Article Contents

• SEWAGE PATHOGENS in SEPTIC SLUDGE
  • COMPONENTS ENTERING A SEPTIC TANK
  • COMPONENTS OF RAW SEWAGE
  • COMPONENTS OF SEPTIC TANK EFFLUENT
  • SETTLED SEPTIC TANK SLUDGE
  • FLOATING SEPTIC TANK SCUM
    
  • GASES IN THE SEPTIC TANK
  • NITROGEN REDUCTION in SEPTIC SYSTEMS

For a detailed list of the pathogens found in common household wastewater such as a septic tank and drainfield, see also our discussion of pathogens in sewage at SEWAGE PATHOGENS in SEPTIC SLUDGE: what makes up the contents of residential sewage? (SEWAGE & SEPTIC CONTAMINANTS)

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.

Another contaminant 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."

Minnis (see references at the Septic Systems Home Page) cites total solids as 300-1200 mg/L, subcategorized into dissolved fixed volatile, suspended fixed volatile, and settleable. Also see SEWAGE CONTAMINATION in BUILDINGS and
SEWAGE CONTAMINANTS in FRUIT / VEGETABLES.

What are the Components of Raw Sewage

Jantrania & Gross (see references at the Septic Systems Home Page) list the following as characteristics of raw sewage

1. Total suspended solids: 155-330 mg/L
2. 5-Day BOD: 155-286 mg/L
3. Total coliform bacteria: 10⁸ to 10¹⁰ CFU/100mL
4. Fecal coliform bacteria: 10⁶ to 10⁸ CFU/100mL
5. Ammonimum-nitrogen, N₄-N: 4-13 mg/L
6. Total nitrogen: 26-75 mg/L
7. 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).

1. Total suspended solids: 38-85 mg/L
2. 5-Day BOD: 118-189 mg/L (this is about a 40% reduction from the level of the entering sewage)
3. Fecal coliform bacteria: 10⁶ to 10⁷ CFU/100mL (note that this little or no reduction over the level of coliform in the entering sewage)
4. Ammonimum-nitrogen, N₄-N: 30-50 mg/L (note that this is considerably higher than their number for raw sewage)
5. Total nitrogen: 29-63 mg/L
6. 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 & SEWER 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.

Nitrogen Levels & Reduction in Septic Tanks, Effluent, Septic Absorption Systems

From earlier in this article we have these typical nitrogen levels in a residentials septic tank

1. Ammonimum-nitrogen, N₄-N: 4-13 mg/L
2. Total nitrogen: 26-75 mg/L

Wastewater treated by a properly functioning OSS generally contains significant amounts of nitrate. After leaving a properly functioning drainfield, nitrified effluent flows through soil.

What happens to nitrates in soil is highly variable. It may be used by plants, flow to ground or surface water, or be consumed by bacteria.

The amount of nitrate removed after leaving the drainfield varies between 0 and 90% depending on site conditions. - Washington State DOH, Nitrogen Removal Fact Sheet

and

In untreated wastewater entering the septic tank, nitrogen is mainly in the form of organic nitrogen compounds, primarily urea. Urea is readily converted to ammonium in the septic tank and the nitrogen content of wastewater exiting the tank, referred to as septic tank effluent, is typically about 85 percent ammonium and 15 percent organic nitrogen.

The concentration of total nitrogen in septic tank effluent is quite variable, ranging from 20 to 200 mg/l.

The median value is roughly 50 to 60 mg/l. After the wastewater exits the septic tank and flows to the unsaturated soil of the drainfield, further transformations occur. The remaining organic nitrogen is converted to ammonium (ammonification).

Most of the ammonium is converted first to nitrite and then to nitrate (nitrification). In sufficiently alkaline soils some of the ammonium may be converted to ammonia and lost to the atmosphere as ammonia gas. Some ammonium may attach to soil particles and be consumed by soil microbes.

Under certain conditions, such as the presence of saturated, anaerobic, organic-rich soil below the unsaturated zone, natural denitrification may take place. However, in the vast majority of conven- tional septic systems this combination of conditions is not present. As a result, denitrification does not take place to any significant extent and the final nitrogen product is mostly nitrate. - NESC Pipelines (2012)

• Alternative Septic System Pretreatment Solutions for New Hampshire, Massachusetts and Maine [Web Article], retrieved2018/05/17, original source: www.ajfoss.com/industry_articles/nitrogen-reduction-septic-systems.php
• MINIMIZING NITROGEN DISCHARGES from ONSITE WASTEWATER SYSTEMS [PDF] NESC, National Environmental Services Center, Tel: 800-624-8301, West Virginia University, Pipelines Vol. 23 No. 1 Summer 2012, retrieved 2018/05/17, original source: http://www.nesc.wvu.edu/pdf/ww/publications/pipline/PL_SU12.pdf
  
  In some locales, property owners are being encouraged or even required to add nitrogenreducing systems to new and existing septic systems. This Pipeline explores why controlling nitrogen is an issue and how the units work.
• SEPTIC SYSTEM NITROGEN HARM [PDF] - Nitrogen Removal Fact Sheet [PDF] Washington State DOH, Nitrogen Removal Fact Sheet - original source www.doh.wa.gov/Portals/1/Documents/4450/337-142-Nitrogen-Removal-from-OSS-FactSheet.pdf
• US EPA Design Manual for Onsite Wastewater Treatment and Disposal [PDF]

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.
• Breuer, T., Benkel, D.H., Shapiro, R.L., Hall, W.N., Winnett, M.M., Linn, M.J., Timothy, J.N., Barrett, J., Dietrich, S., Downes, F.P., Toney, D.M., Pearson, J.L., Rolka, H., Slutsker. L., & Griffin, P.M. (2001). A multi-state outbreak of Escherichia coli O157:H7 infections linked to alfalfa sprouts grown from contaminated seeds. Emerging Infectious Diseases, 7(6), 977-982.
• 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, i inoculum /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.

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Continue reading  at SEWAGE CONTAMINANTS in FRUIT / VEGETABLES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• BACTERIAL PATHOGENS in FRUIT & VEGETABLES - research citations on sewage contaminants in fruits & vegetables
• SEWAGE & SEPTIC CONTAMINANTS
• SEWAGE BACKUP, WHAT TO DO
• SEWAGE NITROGEN CONTAMINANTS
• WASTEWATER BIOCOMPATIBILITY

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