Risk to health from the land application of sludge
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RISK TO HEALTH FROM THE LAND APPLICATION OF SLUDGE. Dr. Joseph B. Farrell, Consultant 1117 Stormy Way Cincinnati, Ohio 45230 Phone/Fax: 513-231-7451 FARRELLJ44UND@AOL.COM. Required Reading.

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Risk to health from the land application of sludge


Dr. Joseph B. Farrell, Consultant

1117 Stormy Way Cincinnati, Ohio 45230

Phone/Fax: 513-231-7451


Required reading
Required Reading

  • “Biosolids applied to Land: Advancing Standards and Practices”. 2002. Prepared by Committee on Toxicants and Pathogens in BIosolids Applied to Land, National Research Council, Pub. National Academy Press, Wash., D.C.

  • Smith, J.E., Jr. et al. 2005. “Infectious Disease Agents in Sewage Sludge and Manure.” Pub. The JG Press, Emmaus, PA.

Nrc committee chairman s comment on la report
NRC Committee Chairman’s Comment on LA Report

  • “The Science of Recycling Sewage Sludge” by Thomas A. Burke. 2002. Buckeye Bulletin, p. 34, November,

    Burke’s comment on the NAS report, “We found no evidence of an urgent public health risk from exposure to land-applied biosolids, based on our review of the scientific literature.”

Nrc report s top recommendations
NRC Report’s Top Recommendations

  • Use improved risk-assessment methods

  • Conduct new survey of chemicals and pathogens in sludge.

  • Implement human health investigations.

  • Increase EPA resources for biosolids

Makeup of raw sewage sludge
Makeup of Raw Sewage Sludge

  • Paper

  • Fecal matter

  • Kitchen wastes

  • Bacterial mass from WW treatment

  • Gray water residues

  • Solids in street runoff

  • Industrial wastes

Chemical makeup of sewage sludge
Chemical Makeup of Sewage Sludge

  • Bulk organics (carbohydrate, protein, fat, mineral oil)

  • Trace organics (hormones, plasticizers, dioxins, PCBs)

  • Nitrogen-phosphorus-potassium

  • Industry (insoluble or absorbed inorganic or organic chemicals)

What substances are health risks
What Substances are Health Risks?

  • Inorganic chemicals (heavy metals) – cumulative.

  • Trace organics (dioxins, PCBs) – cumulative

  • Pathogens (viruses, bacteria, parasites) – immediate

  • Dead bacteria (gram-negative bacteria cell walls) - immediate

Quantifying the risk by risk assessment concentrations and dose response must be known
Quantifying The Risk By Risk Assessment: Concentrations and dose/response must be known

Basis of rule

  • Risk-based for chemical contaminants (heavy metals, organic chemicals)

  • Based on best judgment for pathogens

Pathways of toxicants and pathogens in biosolids to man

Land Application

of Biosolids:

Exposure Route

Host/Pathogen Interaction: Disease Transmission

Surface Water Ingestion

Ground Water Ingestion

Direct Soil Ingestion

Plant Ingestion


Pathways of Toxicants and Pathogens in Biosolids to Man

Why no risk assessment for pathogens
Why no Risk Assessment for Pathogens?

  • Pathogen densities are not conserved

  • Die-off rates are not well-quantified

  • Infectious dose vary widely

  • (But, we know enough to establish reasonable controls)

Bacterial pathogens of potential concern in biosolids

Major Concern



enteropathogenic E. coli

Yersinia enterocolitica

Campylobacter jejuni

Vibrio cholera


Fecal coliform

New issues

E. coli 0157:H7








Antibiotic resistance

Bacterial Pathogens of Potential Concern in Biosolids

Major helminths protozoa in sludge
Major Helminths/Protozoa in Sludge


Cryptosporidium spp.

Giardia spp.


Ascaris spp.

Toxocara spp.

Trichuris spp.


Diseases of special concern
Diseases of Special Concern

  • SARS: It is not enteric. It has almost disappeared (but could come back). It is spread by inhalation of large suspended droplets.

  • Prion Diseases: Consumption of contaminated meat by animals or man. Resist thermal treatment but perhaps not biological digestion. Keep it out of sewers. (CWD, BSE, vCJ disease). CWD does not cross species barrier.

Survival times of pathogens on soils and plants
Survival Times of Pathogenson Soils and Plants

Approach to controlling risk from pathogens
Approach to Controlling Risk from Pathogens

Class A

Eliminate pathogens by extreme processing such as pasteurization. Then reduce vector attraction.

Class B

Reduce pathogens by conventional processing. Reduce vector attraction. Surround use with restrictions that eliminate all paths to man, crops and animals.

Var and pr

  • Pathogen Reduction (PR) and Vector Attraction Reduction (VAR) are required.

  • For Class A, PR must take place before or at the same time as VAR.

Vector attraction reduction var methods
Vector Attraction Reduction (VAR) Methods

  • Reduce volatile solids content

  • Reduce specific oxygen uptake rate

  • Compost for 14d above 400C

  • Raise pH above 12, >11.5 at 24h.

  • Dry to 90%, 75%, depending on sludge.

  • Inject below the soil surface

  • Surface apply but plow in promptly

    (Details are found in 40CFR Part 503)

Pfrp processes class a
PFRP Processes (Class A)

  • Composting

  • Heat drying

  • Heat treatment

  • Thermophilic aerobic digestion

  • Irradiation

  • Pasteurization

  • High pH and temperature/time treatment

    (for each process, minimum processing conditions are specified in 40CFR PART503)

Additional class a processes

  • Prior Testing for Enteric Virus & Viable Helminth

  • Routine monitoring of each batch of treated sewage sludge.

  • Use PFRP Equivalent Process.

Class b biosolids microbiological criteria
Class B Biosolids Microbiological Criteria

  • Reduce fecal coliform density to less than 2,000,000 per gram of solids. This is 1/100 of density in wastewater solids.

  • OR, treat the sludge by a specific stabilization process defined in the regulation (a PSRP)

Psrp processes

  • Aerobic Digestion

  • Air Drying

  • Anaerobic Digestion

  • Composting

  • Lime Stabilization

    (for each process, specific minimum conditions are specified)

Class b restrictions site access
Class B Restrictions: Site Access

  • If high public use (ball field), no public access for 12 months.

  • If low public access ( a farm), no public access for 30 days.

Class b site restrictions harvesting
Class B Site Restrictions: Harvesting

  • Above-ground food crops that touch the soil, 14 months after application

  • Below-ground food crops, 20 months if first 4 months are on soil surface. 38 months if < 4 months on surface.

  • No crops harvested within 30 days of application.

Class b restrictions turf and grazing
Class B Restrictions: Turf and Grazing

  • Turf: If high public access (a front lawn), no harvest before one year after application.

  • Grazing: No grazing until 30 days after application.

Is the practice of la safe
Is the Practice of LA safe?

  • Comment: The US NRC says the rule is sufficiently protective (with caveats)

  • Objection: How can one rule fit the entire United States?

  • Any state can add more stringent requirements tailored to their conditions.

Some state actions
Some State Actions

  • Specify distance to water table (Florida)

  • Specify maximum allowable slope (NY)

  • Decreased some allowable metal concentrations (NY, Nova Scotia)

  • Increased most time restrictions

Problems with 40cfr part 503
Problems with 40CFR PART 503

  • Hard to modify the regulation

  • Are the processes working properly

  • PSRP should have been dropped

  • Grazing restrictions should key to temp.

  • Aerobic digestion PFRP should be fixed

  • Low public use access restriction for Class B should be modified

  • Slow pace of Federal research

Improving reliability
Improving Reliability

  • Increase Government oversight, toughen penalties

  • Require certification of satisfactory operation by independent evaluators (e.g., the Biosolids Partnership)

What the federal rule establishes
What the Federal Rule Establishes

  • General requirements (must give details about the site, sludge, planned practice)

  • Pollutant limits (e.g., max. metal concns.)

  • Management practices (e.g., 10m from US waters)

  • Monitoring frequency

More on what the fr establishes
More on what the FR establishes

  • Operatinal standards (spells out how one must achieve pathogen and VA reduction)

  • Recordkeeping (Certify rule is being kept under penalty of law if not true)

  • Reporting (If > 1 MGD, a yearly report)

Approach to controlling risk from metals to man and soil
Approach to Controlling Risk from Metals to Man and Soil

  • Determine metal concentrations in sludge

  • Apply at agronomic rate (to prevent excessive N/P/K loading)

  • Establish max. concn. in the biosolids

  • Establish max. annual and total loading to the soil.

  • Establish concentration below which no harm will occur.

Class a sludge microbiological criteria
Class A Sludge Microbiological Criteria

  • Salmonella

    • < 3 MPN per 4 grams of TS

  • Fecal Coliforms

    • < 1000 MPN per gram of TS

  • Enteric Viruses

    • < 1 plaque forming unit per 4 grams of TS

  • Viable Helminth Ova

    • < 1 per 4 grams of TS