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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