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Implications of Heavy Metals in Sewage Sludge

Implications of Heavy Metals in Sewage Sludge. Where Do We Stand on Regulations?. Regulation?. Why? - Authorization or mandate How? - Concepts, goals, assumptions, and approaches What? Contents Implement-able package. Regulate? Not Regulate?. Opponent

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Implications of Heavy Metals in Sewage Sludge

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  1. Implications of Heavy Metals in Sewage Sludge Where Do We Stand on Regulations?

  2. Regulation? • Why? - Authorization or mandate • How? - Concepts, goals, assumptions, and approaches • What? • Contents • Implement-able package

  3. Regulate? Not Regulate? • Opponent • Potentially hazardous substances are present • Assuming practice will be harmful until proven safe • Ban or strict limitation • Advocate • Practiced for a long time without “documented” harmful effects • Assuming practice is safe until proven otherwise • Promotion, no need to regulate, or general guidelines • Framework of mind • Decision of regulate may be different

  4. Cumulative Loading

  5. Annual Loading

  6. Discrepancies, Why? • Rule making process • Mandates • Concepts • Goals • Assumptions • Approaches

  7. Rule Making Process • Objective • goals regulation must accomplish • Assumptions • domain within which proposed rules apply • Approach • strategy to accomplish objective • Final rule • Reasonable? • Implement-able? • Acceptance? Public, stakeholders

  8. Approaches • Ecological Balance • Prevent pollutant accumulation in soils • Capacity utilization • Maximize pollutant attenuation capacity of soils

  9. Prevent Pollutant Accumulation Assumptions • Soil - foundation of terrestrial ecosystem and irreplaceable natural resource • Use without undue restrictions, if soil is free of pollutants • Experience increasing difficulty to support uses, if pollutants are allowed to accumulate • Unknown ecological consequences

  10. Prevent Pollutant Accumulation Goal • No pollutant accumulation in the sewage sludge-receiving soils

  11. Prevent Pollutant Accumulation Regulatory Approach • Pollutant-free sewage sludge • Pollutant input = Pollutant output

  12. Prevent Pollutant Accumulation Advantages • In agreement with ecology - sustainable practice • Numerical limits - obtain from simple mass balance calculations • Detailed knowledge on fate and transport of pollutants not needed • One set of standards fits all situations • Easy to implement

  13. Prevent Pollutant Accumulation Disadvantages • Require rigorous pretreatment for wastewater discharge • Phase out incompatible industrial raw material and household products • Performance and reliability of wastewater treatment processes • Little agronomic benefit

  14. Maximize Attenuation CapacityAssumptions • Soil assimilates, attenuates, and detoxifies pollutants • Capacity should be utilized - realize benefits of resource conservation • Land application, environmentally, is equal if not a better option • Stringent limits discourage resource conservation and recovery

  15. Maximize Attenuation CapacityGoal • Realize agronomic benefits of applying sludge on land • Keep pollutants in the soil at a safe level - public health and environment • Beneficial use without compromising public health and environment

  16. Maximize Attenuation CapacityRegulatory Approach • Identify safe/unsafe sludge for land application • Determine maximum tolerable pollutant input • Set maximum tolerable pollutant levels in soil or products

  17. Maximize Attenuation CapacityAdvantages • Resource conservation - appreciation of agronomic benefits • Flexibility of developing safe and site-specific land application operations • Cost effective - competitive with other options

  18. Maximize Attenuation CapacityDisadvantages I • Upper limits for each pollutant must be evaluated separately • Technical information is not always available - uncertainties in setting numerical limits • Pollutant levels in receiving soil will increase - under long-term use and high rates

  19. Maximize Attenuation CapacityDisadvantages II • Margin of safety “may be” narrower • Site may require long-term monitoring

  20. U.S. vs Europe • U.S. - maximizing pollutant attenuation capacity of soils • European countries - preventing pollutant accumulation in soils

  21. Will Sludge Ever Be Free of Metals? • Not likely • Metals will always be used in industrial processing and consumer goods • They will find their ways into the wastewater collection systems • Source control is essential

  22. Heavy Metals in Sewage Sludge Trends • Metal concentration of sludge continued to decrease - implementation of industrial waste pre-treatment program • Pollutant input decreases when “agronomic rate” is followed

  23. USEPA Sewage Sludge Survey

  24. AMSA Sewage Sludge Survey

  25. Estimated Pollutant Inputs(1000 t ha-1) • Reasonable application: <10 t ha-1y-1 for <100 y, therefore <1000t ha-1 • Use Sewage Sludge from San Jose as an example • Estimated pollutant inputs are considerably less than pollutant loading rates specified in Part 503 regulation

  26. San Jose Sewage Sludge

  27. San Jose Sewage Sludge

  28. Implementation • No rule is and will be perfect • Fulfill its mandate and accomplish its goals • If not implementable, regulation = no regulation • Regulations are better than no regulation • Technological issues • Costs issues

  29. Possible Approaches • Match benefits • Waste disposal • Plant nutrients • Sharing and distribution of cost and risk • Urban-rural alliance • Special district • Cooperative • Collective planning and implementation • Long-lasting institutional entities

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