implications of heavy metals in sewage sludge
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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

Implications of Heavy Metals in Sewage Sludge

Where Do We Stand on Regulations?

  • Why? - Authorization or mandate
  • How? - Concepts, goals, assumptions, and approaches
  • What?
    • Contents
    • Implement-able package
regulate not regulate
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
discrepancies why
Discrepancies, Why?
  • Rule making process
    • Mandates
    • Concepts
    • Goals
    • Assumptions
    • Approaches
rule making process
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
  • Ecological Balance
    • Prevent pollutant accumulation in soils
  • Capacity utilization
    • Maximize pollutant attenuation capacity of soils
prevent pollutant accumulation assumptions
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
prevent pollutant accumulation goal
Prevent Pollutant Accumulation Goal
  • No pollutant accumulation in the sewage sludge-receiving soils
prevent pollutant accumulation regulatory approach
Prevent Pollutant Accumulation Regulatory Approach
  • Pollutant-free sewage sludge
  • Pollutant input = Pollutant output
prevent pollutant accumulation advantages
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
prevent pollutant accumulation disadvantages
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
maximize attenuation capacity assumptions
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
maximize attenuation capacity goal
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
maximize attenuation capacity regulatory approach
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
maximize attenuation capacity advantages
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
maximize attenuation capacity disadvantages i
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
maximize attenuation capacity disadvantages ii
Maximize Attenuation CapacityDisadvantages II
  • Margin of safety “may be” narrower
  • Site may require long-term monitoring
u s vs europe
U.S. vs Europe
  • U.S. - maximizing pollutant attenuation capacity of soils
  • European countries - preventing pollutant accumulation in soils
will sludge ever be free of metals
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
heavy metals in sewage sludge trends
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
estimated pollutant inputs 1000 t ha 1
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
  • 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
possible approaches
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