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Land Application of Sewage Sludges Topics of Current Concern. Ellen Z. Harrison, Director Cornell Waste Management Institute Dept. of Crop and Soil Sciences Topics of Current Concern. Excess nutrients (particularly P) Human health Aerosols and odor

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land application of sewage sludges topics of current concern
Land Application of Sewage SludgesTopics of Current Concern

Ellen Z. Harrison, Director

Cornell Waste Management Institute

Dept. of Crop and Soil Sciences

Cornell Waste Management Institute

topics of current concern
Topics of Current Concern
  • Excess nutrients (particularly P)
  • Human health
    • Aerosols and odor
    • Water (wells and runoff)
    • Direct contact
    • Food chain (animal products, home garden)
  • Long term agricultural productivity/Ecohealth
    • Phytotoxicity (metals)
    • Soil health (metals, organic chemicals)
  • Surface water quality
    • Excess nutrients
    • Organic chemicals
    • Metals

Cornell Waste Management Institute

health effects of land application
Health Effects of Land Application

"The NRC report issued in July 2002 concluded that, although there is no documented scientific evidence that the 503 regulations have failed to protect public health, further scientific work is needed to reduce persistent uncertainty about the potential for adverse human health effects from exposure to biosolids.” EPA letter, 2004

Cornell Waste Management Institute

nrc findings
NRC Findings
  • Complex mix of toxic chemicals, infectious organisms, and endotoxins may be present
  • Anecdotal reports of adverse health reactions
  • No “documented scientific evidence” of failure to protect public health
  • Lack of exposure and health info on exposed populations

Cornell Waste Management Institute

absence of evidence is not evidence of absence
Absence of Evidence is not Evidence of Absence

Cornell Waste Management Institute

stakeholder involvement
Stakeholder Involvement
  • Called for by NRC
  • Real contribution to research through local knowledge
  • Mutual understanding of limitations of research

Cornell Waste Management Institute



Cornell Waste Management Institute



Cornell Waste Management Institute

unevaluated pathways of concern to human health
Airborne contaminants






Water borne contaminants




Unevaluated Pathwaysof Concern to Human Health

Cornell Waste Management Institute

  • DeSoto, Florida
  • Grand Bay, Alabama
  • Menifee, California

Cornell Waste Management Institute

werf incident response effort
WERF Incident Response Effort
  • Biosolids Summit – July 2003
  • Public Partnering Protocol
  • PSC for Incident Response Investigation Project

Cornell Waste Management Institute

organic chemicals in sewage sludges
Organic Chemicals in Sewage Sludges
  • Many thousand chemicals in use
  • Few studied
  • Limits of detection can be insensitive
  • Lit search obtained data on 516

Cornell Waste Management Institute

epa soil screening levels
EPA Soil Screening Levels
  • Risk-based
  • Several exposure paths
  • Trigger for site-specific risk assessment under Superfund
  • Used by NRC as indicator

Cornell Waste Management Institute


A=SSL, ingestion and dermal

From NRC, 2002

Cornell Waste Management Institute

sludge application at the cornell orchard
Sludge Application at the Cornell Orchard
  • 1978: Ley Creek Treatment Plant (Syracuse, NY) sewage sludge, applied at 244 tons/hectare, till depth 20 cm, 0.08 ratio of sludge:soil
  • 1979 to 1983: test crops grown on plots
  • 1985: entire site was deep plowed, limed and grass planted
  • 1986: apple trees planted, ground cover maintained, mowed
  • 2002: apple trees removed
  • 1994 and 2001 (16 and 23 years later): soil samples collected and analyzed for PAHs, PCBs and PBDEs (PBDEs, non-detect) by Hale and Laguardia

Cornell Waste Management Institute

old orchard sludge plot
Old Orchard Sludge Plot

Cornell Waste Management Institute

pahs cornell orchard soil applied 1978
PAHs - Cornell Orchard (soil), Applied 1978

Laguardia and Hale data

Cornell Waste Management Institute

pcbs cornell orchard soil applied 1978 laguardia and hale data
PCBs - Cornell Orchard (soil), Applied 1978Laguardia and Hale data

Syracuse NY. WWTP, 1972-73, PCBs 6600 ng/g (Furr, et al,1976)

Cornell Waste Management Institute

PAHs, PCBs are persistent in Cornell Orchard 23 years after application

PBDEs below detection limit, consistence with estimated usage rate


From LaGuardia, et al VIMS

Cornell Waste Management Institute

long term effects of sludge application
Long-term Effects of Sludge Application
  • One dewatered sludge applied heavily in 1978
  • Cumulative metal loading ~EPA 503 limits
  • Research
    • Effect on worms – 2003 field and laboratory

Cornell Waste Management Institute

looking for earthworms
Looking for Earthworms

Cornell Waste Management Institute

number of worms in the field
Number of Worms in the Field

Cornell Waste Management Institute

accumulating organic matter
Accumulating Organic Matter

Cornell Waste Management Institute

reproductive effects on worms experimental data
Reproductive Effectson Worms: Experimental Data

Cornell Waste Management Institute

risk assessments contain many assumptions and policy choices
Risk assessments contain many assumptions and policy choices

Examination of Several Assumptions that Dramatically Impact Calculated Risks to Water Quality

Cornell Waste Management Institute

different sludges and sludge products behave differently
Different sludges and sludge products behave differently
  • Sludge variations
    • Influents vary
    • WWTP processes vary
  • Sludge treatment variations
    • anaerobic digestion
    • composting
    • lime stabilization
    • heat stabilization/pelletization
    • alkaline soil amendment

Cornell Waste Management Institute

what about class a eq
What about Class A EQ?
  • No different than Class B EQ
  • Endotoxins
  • Nutrients
  • Chemicals
  • Odor potential

Note that processing mode impacts fate and transport, odor potential, pathogens

Cornell Waste Management Institute

risk assessments contain many assumptions and policy choices1
Risk assessments contain many assumptions and policy choices

Examination of Several Assumptions that Dramatically Impact Calculated Risks

  • Assessing the Risk to Surface Water
  • Assessing the Risk to Groundwater
  • Assessing the Risk of Cadmium to Home Gardener Using Sludge
    • How much of each crop does the exposed person eat?
    • How much Cd uptake into the crops?

Cornell Waste Management Institute

map of nys showing relative size of watershed and sludge site under 503 ra assumptions
Map of NYS Showing Relative Size of Watershed and Sludge Site Under 503 RA Assumptions

Only 0.24% of watershed assumed to receive sludge.

A small stream may have much greater %of watershed receiving receiving sewage sludges. What is the risk to person fishing such a stream? What is the environmental risk?

Watershed: 427,000 ha

Sludged Area: 1074 ha


Cornell Waste Management Institute

sludges and water quality
Sludges and Water Quality
  • Movement to Groundwater
    • In solution
    • Macropore preferential flow
    • Enhanced/facilitated transport

(movement of contaminant associated with organic matter)

Cornell Waste Management Institute

groundwater and 503 ra
Groundwater and 503 RA
  • Rapid flow phenomena aren’t accounted for in EPA model (macropores)
  • One test tube experiment with one sludge and one soil are basis for metal mobilities to groundwater in the EPA risk assessment
  • Substantial dilution or attenuation of leachate before reaching receptor well is assumed (arsenic’s leachate/well concentration ratio is 230)

Cornell Waste Management Institute

example tclp leachability of metals as total metals
Example:TCLP Leachability of Metals as % total metals

Sludge Products Behave Differently

Cornell Waste Management Institute

Richards, et al 1997

preferential flow paths
Preferential Flow Paths

Blue dye reached 6 feet in 1/2 hour

Model would predict ~3 years

Cornell Waste Management Institute

comparison of diet used in epa risk assessment and usda recommended diet
Comparison of Diet Used in EPA Risk Assessment and USDA Recommended Diet

How Much Does the Home Gardener Eat?

1+2=USDA Recommended Diet

About 2 x as much veg

1=EPA daily diet

Used Avg. ~1980 consumption

Veg consumption has increased

Home gardeners eat high veg diet



Cornell Waste Management Institute

cadmium uptake into leafy vegetables
Cadmium Uptake into Leafy Vegetables
  • 4 orders of magnitude difference (Different crops and cultivars, soils, pH, sludges, etc)
  • Federal 503 risk assessment used geometric mean
  • Home gardeners eat from a specific, not avg, garden

Cd uptake into leafy veg, data from field studies

Cadmium uptake

Uptake value used in 503--------

Cornell Waste Management Institute

Cadmium Loading


Cadmium Calculation for Home Gardener

Eating Crops from Sludge-amended Soils

Allowable Sludge Cadmium (ppm)

120 EPA calc home gardener risk (not the limiting path)

39 503 limit(soil ingestion path)

- - - - - - - - - - - - - - - - - - -

15 simply changing to USDA diet

5 changing to USDA diet

and arithmetic mean uptake

1.5 changing to USDA diet

and 90th percentile uptake

Changing a few assumptions results in very different standard

Cornell Waste Management Institute

there is no such thing as safe rather what is the acceptable risk to whom under what conditions
There is no such thing as


Rather what is the

Acceptable Risk?

To Whom?

Under what conditions?

Cornell Waste Management Institute

the case for caution
The Case for Caution


  • Our ability to confidently predict risks from land application is very limited
    • Contaminants concentrate in sewage sludges
    • Many unevaluated contaminants in sludges (503 -only indicator pathogens and 9 elements)
    • Present standards are based on a risk assessment with many short comings
  • Liability rests largely with the farmer
  • If problems, hard to prove cause
  • Enforcement and monitoring are inadequate
  • Reports of illness

Cornell Waste Management Institute

management considerations regarding use of sewage sludges and sludge products

Management Considerations Regarding Use of Sewage Sludges and Sludge Products

Cornell Waste Management Institute

  • From homes, schools, etc
  • From wells
  • From groundwater
  • From bedrock
  • From watercourses/floodplains
  • Significant aquifers

Cornell Waste Management Institute

application practices
Application Practices
  • Incorporation - if yes, when
  • Pasture application
  • Food crops
  • Stockpiling
  • Soil type –permeability, steep, karst

Cornell Waste Management Institute

legal administrative
  • Indemnification agreement
  • Record keeping
  • Testing –frequency and/or parameters beyond 503?
  • Archive samples
  • Site specific permits for bulk application

Cornell Waste Management Institute

  • Nutrient Mgmt plan
  • Application rate – P based?
  • Soil testing
  • Limit annual application amount
  • Limit cumulative amount
  • Limit frequency of application
  • Limit % of a watershed that can be sludged
  • Not on frozen ground
  • Not when soils is within 75% of field moisture capacity

Cornell Waste Management Institute