Transcript Effect of Processing

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
[email protected]
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
• “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 landapplied biosolids, based on our review
of the scientific literature.”
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
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Paper
Fecal matter
Kitchen wastes
Bacterial mass from WW treatment
Gray water residues
Solids in street runoff
Industrial wastes
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?
• 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
Concentration Dose/response
Metals
yes
yes
Toxic organics
Yes
Much
knowledge
Pathogens,
dead bacteria
No
Great variations
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
Surface
Water
Ingestion
Ground
Water
Ingestion
Direct
Soil
Ingestion
Plant
Ingestion
Host/Pathogen
Interaction: Disease
Transmission
Inhalation
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)
Dose/Response for Pathogens
Organism
Infective Dose
Protozoa
1-50 cysts
Enteroviruses
1-50 PFU
Helminths
One egg
Pathogenic bacteria
100-1,000,000
CFU
Bacterial Pathogens of Potential
Concern in Biosolids
Major Concern
New issues
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Salmonella
Shigella
enteropathogenic E. coli
Yersinia enterocolitica
Campylobacter jejuni
Vibrio cholera
Leptospira
Fecal coliform
E. coli 0157:H7
Listeria
Helicobacter
Mycobacteria
Aeromonas
Legionella
Burkholderia
Endotoxins
Antibiotic resistance
Human Enteric Viruses (from Gerba)
Virus Group
Enterovirus (polio, coxsackie,
echo)
Hepatitis A virus
Reoviruses
Rotaviruses
Adenoviruses
Astroviruses
Hepatitis E virus
Caliciviurses
No. of Types
69
1
3
8
49
7
1
3?
Major Helminths/Protozoa in
Sludge
Protozoa
Cryptosporidium spp.
Giardia spp.
Helminths
Ascaris spp.
Toxocara spp.
Trichuris spp.
Taenia
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
SOIL
PLANTS
PATHOGEN
ABSOLUTE
MAXIMUM
COMMON
MAXIMUM
ABSOLUTE
MAXIMUM
COMMON
MAXIMUM
Bacteria
1 year
2 months
6 months
1 month
Viruses
6 months
3 months
2 months
1 month
Protozoa
10 days
2 days
5 days
2 days
Helminths
7 years
2 years
5 months
1 month
Reductions due to Processing
Anaerobic
digestion
1/30
Lime
treatment
>>1/100
composting
, pasteurize
>>1/100
>>1/100
>>1/100
enterovirus 1/10
>>1/100
>>1/100
Helminth
eggs
?, 1/10
>>1/100
Fecal
coliform
Pathogenic 1/10
bacteria
1/3
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
• 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)
• 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
• 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
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Aerobic Digestion
Air Drying
Anaerobic Digestion
Composting
Lime Stabilization
(for each process, specific minimum
conditions are specified)
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
• 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
• 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?
• 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
• 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
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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
• Increase Government oversight,
toughen penalties
• Require certification of satisfactory
operation by independent evaluators
(e.g., the Biosolids Partnership)
Concn.: Exceptional Qual. Biosolids
METAL (mg/kg)
NOVA SCOTIA
US EPA
Arsenic
Cadmium
13
3
41
39
Chromium
Cobalt
Copper
210
34
400
1200
Mercury
Molybdenum
Nickel
Lead
0.8
5
62
150
17
18
420
300
Selenium
2
36
Zinc
700
2800
1500
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
• 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
• 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
• 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