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Septic Systems: The Real Poop

Septic Systems: The Real Poop. Dennis McQuillan, New Mexico Environment Department, September 2003. Septic Tanks. The purpose of a septic tank is to: separate solids and oil/scum (sinkers and floaters) from the waste water;

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Septic Systems: The Real Poop

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  1. Septic Systems: The Real Poop Dennis McQuillan, New Mexico Environment Department, September 2003

  2. Septic Tanks The purpose of a septic tank is to: • separate solids and oil/scum (sinkers and floaters) from the waste water; • provide some degree of anaerobic digestion of organic matter; and • deliver the waste water to the subsurface

  3. Septic Tank Inside Tank: phase separation; digestion of organic matter; gas generation (methane and hydrogen sulfide) This and previous slide courtesy of New Jersey Department of Environmental Protection

  4. Septic Tanks • Septic tanks are a suitable means of waste disposal in many areas of New Mexico where lot sizes are large enough, and subsurface conditions are favorable enough, for contaminants to be naturally attenuated to acceptable levels. • Non-biodegradable materials should not be disposed of to septic tanks. • Septic tanks must be pumped periodically to remove solids and scum.

  5. New Mexico • ~220,000 household septic systems (septic tanks and cesspools), with ~6500 new systems/year • ~75 million gallons per day of wastewater discharged to the subsurface • most of this wastewater eventually percolates to ground water • many areas using septic systems also rely on private wells for domestic supply

  6. Environmental Justice

  7. Environmental Problems • Leachfield failure: surfacing sewage, backed up toilets and sinks; • Surface-water contamination: elevated nutrients, algae blooms; • Ground-water contamination: nitrate or anoxic conditions; septic systems are the leading cause of GWC in N.M.

  8. Regulatory Controls • < 2000 gpd, domestic waste only, EIB Liquid Waste; • > 2000 gpd domestic, or any non-domestic, WQCC.

  9. Failed Leachfield

  10. Raw Sewage Discharge

  11. Algae Bloom Caused by Nutrients in Sewage

  12. Gallinas River, Mora River, Red River, Rio Cebolla, Rio Pueblo, Rio Ruidoso

  13. Meth Lab Cesspool Ground Water

  14. Septic Tank Floating on GW

  15. What’s Wrong with this Picture? nitrification Montana State University

  16. Drinking Your Neighbor’s Sewage ammonia, urea nitrification nitrate ground-water flow

  17. ABQ West Mesa NO3-N (mg/L) 1 1 2 Ground-Water Flow 10 8 10 10 12 2 15 6 22 11 10 18 13

  18. Atmospheric Nitrogen Atmospheric Nitrogen Animal &Human Manure Industry Fertilizer Nitrogen Fixation Plant Decay N2 Gas Organic nitrogen Ammonification Oxidation Ammonium Nitrite Denitrification Oxidation Plant Uptake Nitrate Leaching Water Table Nitrate Contamination Environmental Nitrogen Cycle Nitrification

  19. Ground-Water ContaminantsCaused by Septic Systems

  20. Anoxic Ground-Water Conditions • Oxygen deficiency • Nitrate is chemically unstable, ammonia in sewage will not oxidize to nitrate • Manganese, iron and hydrogen sulfide may be present, and can cause taste, odor and staining problems

  21. REDOX Reactions • Aerobic respiration • Denitrification • Manganese reduction • Iron reduction • Sulfate reduction • Methanogenesis Decreasing Energy Yield (to ground-water bacteria)

  22. South Valley Wastewater Loading

  23. South Valley GW Manganese

  24. Three Domains of Life on Earth • Bacteria: lack true cell nucleus • Archaea: morphologically same as bacteria but have different RNA sequence • Eucarya: complex cell structure & nucleus; protozoans, algae, plants & animals • Viruses: tiny, parasitic, non-cellular lifeforms?; no independent metabolism; cannot reproduce w/o host

  25. Ground Water Microbes • Bacteria: Pseudomonas (common aerobes in GW),Escherichi, (E. coli), Shigella, Salmonella • Archaea: geologically important; methanogens • Eucaryotes: less abundant in GW; algae, fungi & protozoa (Giardia, Cryptosporidium); low mobility; can prey on bacteria • Viruses: enteroviruses detected in GW; pathogen survival 1-3 months?; hepatitis

  26. Contamination Factors • Wastewater flow • Vadose-zone conditions (redox, % saturation, hydraulic conductivity) • Depth to ground water • Ground-water conditions (redox, hydraulic conductivity, gradient) • Lot size • Nearest down-gradient supply well

  27. Alamogordo, Albuquerque, Anthony, Arenas, Belen, Bernalillo, Bosque Farms, Caballo, Carlsbad, Carnuel, Chamita, Chilili, Chimayo, Clayton, Corralles, Cuyamungue, Deming, Des Moines, Dexter, Elephant Butte, El Rancho, Espanola, Folsom, Gabaldon, Glorieta, Hernandez, Hobbs, Holman, Hondo, Jacona, Jal, Jarales, Lamy, La Puebla, Las Placitas, Lordsburg, Los Lunas, Lovington, Magdalena, Medanales, Monticello, Nambe, Nara Visa, Pojoaque, Portales, Quartales, Quemado, Questa, Raton, Reserve, Roswell, Santa Cruz, Santa Fe, Sedillo, Seneca, Silver City, Tesuque, Tome, Tucumcari, Velarde

  28. Ground-Water Modeling • N.J. nitrate dilution model: uses population density and soil type to calculate acceptable lot size • Nitrate dispersion simulation: after 50 years, nitrate dilutes to safe level in 600 feet; low level plume extends ~1 mile • Lot size simulations: minimum lot sizes of 2, 5, and 40 acres to protect valley-fill, karts and fractured rock aquifers, respectively in Bernalillo County

  29. Health Effects Nitrate – blue-baby case in Carnuel Pathogens – • 1980’s study in ABQ South Valley found no relationship between diarrheal illness and consumption of private well water • Additional human health studies are needed /w emphasis on Colonias’

  30. Alternatives to Conventional Septic Tanks • Composting toilets • Holding tanks • Evapotranspiration (ET) mounds • Aerobic treatment systems • Centralized management of on-site systems • Regional collection/treatment systems

  31. Composting Toilet

  32. Septic Tank and ET Mound

  33. Advanced Treatment System

  34. Small Lot Policy • Permit applications for conventional septic tanks on lots smaller than ¾ acre will be scrutinized to make sure that highly vulnerable bodies of water are protected. • NMED may require that advanced treatment systems be installed on these small lots.

  35. Highly Vulnerable Bodies of Water • water-table aquifer with a vadose zone thickness of 100 foot or less containing no soil or rock formation that would act as a barrier to saturated or unsaturated flow; • aquifer with known anthropogenic anoxic or nitrate contamination; • aquifer overlain by fractured bedrock; • aquifer in karst terrain; or • gaining stream known to be impacted by nutrients from liquid waste systems

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