On-Site Wastewater Treatment Systems

1. Michael Urynowicz, Ph.D., P.E. Assistant Professor Department of Civil & Architectural Engineering University of Wyoming, Laramie, WY 82071-3295 Telephone: 307.766.4398 Email: murynowi@uwyo.edu On-Site Wastewater Treatment Systems

2. Presentation Outline Workshop On-Site Wastewater Treatment Systems Centralized vs Decentralized Wastewater Treatment Systems Wastewater Constituents Conventional Septic System Septic Tank Soil Absorption System Importance of the Clogging Matt Importance of the Unsaturated Zone Fate and Transport of Pathogens Alternative On-Site Wastewater Systems Video and Closing Remarks

3. On-Site Wastewater Treatment Systems Underground cesspool (France, 1870s) Septic tank systems (U.S.A., early 1900s)

4. On-Site Wastewater Treatment Systems Nearly 25% of the U.S. population is served by on-site and decentralized wastewater systems. Approximately one-third of new development is supported by such systems. Roughly 25 million existing systems. Approximately 0.2 million new systems being installed each year.

5. On-Site Wastewater Treatment Systems Traditionally, onsite systems were viewed as temporary disposal solutions. �Good enough for now� (i.e., until the public sewer is available).

6. On-Site Wastewater Treatment Systems Why have on-site treatment systems been traditionally viewed as inferior to centralized systems?

7. On-Site Wastewater Treatment Systems

8. Why the shifting paradigm? On-Site Wastewater Treatment Systems

9. On-Site Wastewater Treatment Systems Questions and Considerations (Micro-Scale) Levels of purification achieved by conventional onsite systems Effects of using alternative on-site systems Vadose zone sampling Clogging zone formation affects Source of pathogens in water

10. On-Site Wastewater Treatment Systems Questions and Considerations (Macro-Scale) Public health impacts associated with using decentralized versus centralized systems Public health impacts associated with catastrophic events (e.g., flooding) Public health impacts associated with inadequate design, siting and operation and maintenance Watershed effects

11. Most of the areas using septic systems also rely on private wells for domestic supply. On-Site Wastewater Treatment Systems

12. Organic Compounds BOD, COD, TSS Nitrogen NH4+-N, organic-N, NO3--N, N02�N Anaerobic (NH4+-N, organic-N) Aerobic (NO3--N) Wastewater Constituents

13. Nitrogen Dissolved Inorganic Nitrogen (NO3--N, N02�N, NH4+-N) Kjeldhal Nitrogen (NH4+-N and organic-N) Wastewater Constituents

14. Phosphorous Organic-P, Orthophosphates Pathogens Bacteria, viruses, protozoa, helminths Most water borne pathogens can cause illness with 10 to 1000 infectious units Wastewater Constituents

17. Conventional Septic Systems Advantages Can provide excellent treatment and disposal of wastewater Reliable, cost-effective method Least costly to maintain Disadvantages Can be used at fewer and fewer sites

28. Importance of the Clogging Mat

29. Importance of the Unsaturated Zone Water travels more slowly through the unsaturated zone Slower flow ? Longer residence time (more opportunity for purification to occur) Good aeration is necessary to achieve die-off of bacteria and viruses

30. Alternative On-Site Wastewater Treatment Systems Not all sites are well suited for conventional on-site wastewater treatment systems Distance from building, property line, property lines, potable water lines, water well, waterways etc.) Availability of perc. land

31. Alternative On-Site Wastewater Treatment Systems Advantages Can provide excellent treatment and disposal of wastewater. Can be used at more problematic sites. Disadvantages Higher maintenance Higher cost

45. Community Onsite Options

46. Decentralized wastewater treatment systems are now considered an effective and long-term wastewater treatment approach. Requires proper design, installation, and operation & maintenance. Matching the system with the site is critical. The use of on-site wastewater treatment systems will continue to grow and evolve. Closing Remarks