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On-Site Wastewater Treatment Conventional Systems, Existing Alternatives, and Research Needs

On-Site Wastewater Treatment Conventional Systems, Existing Alternatives, and Research Needs Harold W. Walker, P.E ., Ph.D. Professor and Director Civil Engineering. Conventional Septic System. Conventional Septic System. Leaching Pit. Nitrogen Cycle. Feammox. Anammox. O 2.

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On-Site Wastewater Treatment Conventional Systems, Existing Alternatives, and Research Needs

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  1. On-Site Wastewater TreatmentConventional Systems, Existing Alternatives, and Research Needs Harold W. Walker, P.E., Ph.D. Professor and Director Civil Engineering

  2. Conventional Septic System

  3. Conventional Septic System Leaching Pit

  4. Nitrogen Cycle Feammox Anammox • O2 Denitrification Nitrification ORG-N • O2 Nitrification

  5. Survey of N Reduction Studies Scientific consensus: Little nitrogen removal occurs in septic systems with a traditional drainfield or leaching pit • USEPA Design Manual (2002) states 10-40% removal of N in soil infiltration systems based on studies in the 1970s (p.3-23). • Beal et al. (2005) reviewed the literature and found very little N removal in soil absorption systems, though depended on redox state, microbial composition, and labile carbon. • Wastewater Treatment Workgroup, Chesapeake Bay Partnership (2012) established a 20% reduction credit TN in a conventional septic system based largely on earlier studies by Jennson (1990) and Long (1995). • George Loomis (University of Rhode Island, Extension Service) estimates 10-15% removal of nitrogen in septic systems and cesspools, as quoted in Newsday.

  6. Conventional Septic SystemPerformance – Nitrogen Septic Tank EffluentTKN = 60 mg/L ORG-N = 5 mg/L NH3-N = 55 mg/L NO2-+NO3-=<1 Final EffluentTKN = 50 mg/L ORG-N = 0 mg/L NH3-N = 0 mg/L NO2-+NO3-= 50 mg/L InfluentTKN = 60 mg/L ORG-N = 45 mg/L NH3-N = 15 mg/L NO2-+NO3-=<1

  7. Alternative Treatment Systems

  8. Alternative On-Site Systems • Mixed Biomass • Activated Sludge Systems • Fixed Film Systems • Sequencing Batch Reactors (SBRs) • Two Phase Biomass • Heterotrophic denitrification • Autotrophic denitrification • Soil Infiltration/Uptake • Constructed Wetlands

  9. Alternative On-Site Systems

  10. Alternative On-Site Systems

  11. Concluding Remarks • Existing cesspools and septic systems (with leach pits) remove little nitrogen. • Currently available, alternative systems can remove >50% TN in some cases, but may not be widely adopted due to cost, reliability, or other factors. • Demonstrating and installing currently available alternative technology is a good start, but better technology is needed. • Significant advances in technology will be made if R&D funding available

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