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U.S Environmental Protection Agency

Onsite Wastewater Treatment Systems Manual: A Performance Based Approach for Designing and Managing Onsite Wastewater Systems. U.S Environmental Protection Agency. In the beginning . . . . And thou shalt have a Paddle upon thy Weapon, and it shall be:

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U.S Environmental Protection Agency

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  1. Onsite Wastewater Treatment Systems Manual:A Performance Based Approach forDesigning and Managing Onsite Wastewater Systems U.S Environmental Protection Agency

  2. In the beginning . . . . • And thou shalt have a Paddle upon thy Weapon, and it shall be: • When thou wilt ease thyself abroad, Thou shalt dig therewith, • and shalt Turn Back and Cover that which Cometh from Thee • Deuteronomy 23:13

  3. Where we’ve been . . .

  4. 2002 USEPA Onsite Manual • Complements the 1980 Design Manual • Promotes the use of design performance requirements • Advocates perpetual management of all systems • Focuses on risk- based assessments • Available on the Internet and CD

  5. How to access the OWTS Manual CDs are available at www.epa.gov/owm/onsite The online version is available at: http://www.epa.gov/ORD/NRMRL/ To order a printed version, send a request to: U.S. EPA/NSCEPP.O. Box 42419Cincinnati, Ohio 45242-0419 Send an email to ncepimal@one.net or call 1-800-490-9198 or (513) 489-8190

  6. Summary of manual contents • Background and use of OWTSs • Management of onsite systems • System performance requirements • Treatment processes and technologies • Treatment system selection

  7. Note: The Onsite Wastewater Treatment Systems Manual is not intended to determine appropriate or inappropriate uses of land. The manual presents information that can be used to select appropriate technologies and management strategies to minimize risks to human health and water resources in areas not connected to centralized sewage systems.

  8. Background and use of OWTSs

  9. Current shortcomings • Lack of clear performance requirements • Few O&M or management programs • Watershed/regional impacts often ignored • Poor public outreach and education • Little coordination with planning, zoning, water resource, and other agencies and stakeholders

  10. Reasons for concern • Public health • Water quality • Property values • Community quality-of-life

  11. OWTS pollutants of concern

  12. Nutrients and bacteria from a variety of sources are primary pollutants in the U.S. Onsite systems are a source of nutrients and bacteria

  13. Onsite system malfunction rates • U.S. Census Bureau Reports 7-10% • National Small Flows Clearinghouse 10% • Nelson, Dix, Shepard Survey up to 70% ??? • Best professional judgement; failure definitions varied A significant number of community water systems list onsite systems as a potential contaminant source for drinking water supplies . . .

  14. Buttermilk Bay Assessment

  15. POPULATION GROWTH 100% increase in public water withdrawals (1960 - 1995) Food production needs URBAN SPRAWL Concentrates demand Leads to reductions in ground water recharge ECOSYSTEM MAINTENANCE Water supplies are needed to maintain sensitive ecosystems and/or endangered species (e.g., Pacific NW, FL) Increasing demand for groundwater

  16. Elevated nitrate concentrations in groundwater in Kent County, MI Nitrogen sources include agriculture and lawn fertilizers, atmospheric deposition, onsite systems Source: Kent County Health Dept.

  17. Source Water Assessment & Protection Program (168,000 PWSs Must Have Complete Assessments By 2003) 2,156 (98%) 4,211 (96%) 2,103 (98%) 1,347 (95%) 550 (96%) 2,023 (97%) 8,352 (98%) 1,628 (85%) 2,645 (96%) 10,630 (97%) 11,724 (99%) 718 (96%) 2,080 (98%) 479 (94%) 12,350 (98%) 736 (97%) 10,389 (97%) 3,705 (98%) 1,932 (94%) 4,279 (95%) 5,939 (95%) 1,329 (97%) 4,837 (96%) 551 (97%) 675 (95%) 5,801 (93%) 1,414 (94%) 3,815 (98%) 953 (91%) 3,776 (96%) 2,101 (95%) 1,079 (93%) 2,701 (94%) 8,146 (91%) 712 (67%) 7,511 (97%) 1,173 (79%) 1,527 (90%) 1,732 (93%) 1,199 (89%) 1,274 (95%) 1,687 (94%) 2,572 (92%) 1,645 (98%) 1,485 (88%) 702 (63%) Puerto Rico 490 (74%) 1,820 (87%) 6,865 (89%) 141 (74%) 6,607 (94%) 1996 SDWA Source Water Assessments Source Water Protection 2003 1. Delineate Source Water area 5. Establish local SW protection risk management measures 2. Contamination source inventory 6. Develop Contingency Plans 3. Susceptibility Determinations 4. Public distribution & discussion of findings

  18. Management of onsite systems • Chapter 2 of the OWTS manual deals with system management • The USEPA Office of Water has developed guidelines and a handbook for managing onsite and clustered systems

  19. Management:traditional management focus . . . . • Permitting: prescribed limits on acceptable sites; prescribed system designs • Installation: oversight of construction and installers and/or licensing, registration • O & M: homeowner booklets and brochures, tank pumping info • Corrective actions: repair or replacement upon receipt of verified complaints

  20. Performance-based management focus: • Performance requirements based on relative risk to valued surface and ground water resources • Management of all systems based on technology and risk assessments • Simple systems installed at low densities farther away from valued resources = lower management intensity • Complex systems or those installed at high densities near valued resources = managed more intensively

  21. Performance-based management elements • Cooperative watershed planning: specifying the necessary water quality to permit a specific use at a specific location downstream of the onsite treatment systems • Performance-based design: requiring specific treatment levels • Operation: renewable system permits, periodic inspections • Maintenance: requiring tank pumping at regular intervals, maintenance contracts • Corrective actions: replacement requires new performance-based designs

  22. What constitutes a performance-based approach? • Siting and design: • Designing a system that meets performance requirements based on site conditions • rather than requiring the site to meet prescriptive criteria (lot size, soil permeability, depth to groundwater, etc.) needed for the approved system type • System management: • Management programs that provide perpetual system oversight • to protect public health, water resources, property values

  23. Overview of performance-based approach • Wastewater characterization • Site evaluation • Design boundary identification & characterization • Regulatory requirements for system performance

  24. Residential wastewater sources/flows

  25. Residential wastewater characterization:flow and strength analyses • Estimate: • average daily flows (or use meter info) • hourly and instantaneous peak flows • wastewater strength (composition) using similar-facility comparisons or sampling info

  26. Wastewater strength can vary considerably

  27. Assessing site conditions • Preliminary review • Soil surveys, aerial photos, geology, slopes • Info from adjacent systems, installers • Reconnaissance survey • Landscape position, vegetation, buildings, drainage, topography • Identification of prospective sites

  28. Assessing site conditions • Consider broader planning needs • Clustering of systems can improve performance, lower capital & O/M costs • Detailed evaluation • Soil profile analyses via backhoe pit • Characterize subsurface wastewater flow path • Groundwater assessment (redox, wells, maps, etc.)

  29. Identify design boundaries ... places where conditions change abruptly… in subsurface infiltration systems,the soil is part of the treatment system. • Infiltrative surface (biomat location) • Restrictive horizons; perched water tables • Surface of saturated zone (groundwater) • Point at which performance must meet water quality goals (SW/GW discharge, point of re-use, spray irrigation, etc. as required by regs)

  30. Common design boundaries

  31. Close-up of trench system design boundaries

  32. Identify desired performance requirements of regulatory agencies • Assess cumulative ecosystem impacts • TMDLs, 303(d) lists • Source water protection (MCLs) • Watershed restoration action strategies • Anti-degradation requirements

  33. Identify desired performance requirements (cont.) • Protection of public health • No surfacing or well pollution • Protection of water resources • Groundwater (pathogens, nitrate) • Surface waters (pathogens, nutrients) • Meet overall water quality standards • Consider existing/planned system requirements and impacts • System densities, critical areas • Water resource sensitivities

  34. Consider source water protection areas when establishing performance requirements Ground Water Surface Water

  35. Performance requirements should also consider watershed-scale impacts

  36. Assess design boundary loadings • Loadings to treatment system components • controls sizing, technology selection • Loadings to the infiltrative surface • controls size of infiltration system • Loadings to restrictive horizons • controls vertical placement of SWIS • Loadings to groundwater • controls vertical placement, may limit type

  37. Lateral view of an effluent plume showing its movement through the soil toward design boundaries

  38. Typical treatment train components • Septic tank(s) • Single or multiple compartments • Watertight; sized for peak flows • Equipped with effluent screen to protect SWIS • Subsurface wastewater distribution • Trenches filled with gravel • Gravelless trenches (chambers) • Pressure-dosed systems • Alternative systems

  39. Treatment train components (cont.) • Alternative systems • Mounds, at-grades, intermittent or recirculating filters • Aerobic units • Vegetated submerged beds

  40. Chapter 4 topics: processes & technologies • Conventional OWTSs • Soil based treatment and distribution systems • Use of alternative and advanced pretreatment systems • Fact sheets for classes of alternative treatment systems and special issues

  41. Treatment processes: components of a conventional soil-based system

  42. Desirable SWIS characteristics • Width: < 3 ft. wide • Length: Must meet contour load limits • Orientation: Along landscape contours • Vert. Placement: High in soil profile; 2 ft GW/BR • Dosing: Uniform over infiltrative surface • Landscape pos: Ridge lines, hilltop, shoulder slopes • Drainage: Moderate- to well-drained site

  43. Loadings

  44. How well does soil treatment work? Very well . . . IF the topography, soil types, and groundwater levels meet requirements.

  45. Dispersal system options:drip irrigation • Drip lines high in the soil profile enhance treatment • Can be used on sloping sites with trees, etc. Source: University of Minnesota Extension

  46. Other Chapter 4 topics • Aerobic treatment units (ATUs) • Media filters (ISFs and RSFs) • Fact sheets for about a dozen families/classes of available treatment units

  47. Chapter 5:Treatment system selection • New system design approach • Rehabilitation of failed onsite system

  48. Failure analysis: types of failure and effects

  49. Failure analysis: onsite wastewater failure diagnosis and correction procedure

  50. Failure analysis: onsite wastewater failure diagnosis and correction procedure (cont.)

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