Current through Register Vol. 24-06, March 15, 2024
This section contains the requirements for biosolids to be
classified either Class A or Class B with respect to pathogens.
The Class A pathogen reduction requirements must be met at the
same time or before the vector attraction reduction requirements in WAC
173-308-180(1), (2), or
(3).
(1)
Class A - Alternative 1: Time and
Temperature.
(a)
Fecal
coliform or Salmonella sp. bacteria density. The density of
fecal coliform in the biosolids must be less than 1000 Most Probable Number per
gram of total solids (dry weight basis) or the density of
Salmonella sp. bacteria in the biosolids must be less than
three Most Probable Number per four grams of total solids (dry weight basis) at
the time the biosolids are used, at the time the biosolids are prepared for
sale or give away in a bag or other container for application to the land, or
at the time the biosolids or material derived from biosolids is prepared to
meet the requirements for exemption in WAC
173-308-200, and one of the
requirements in (b) through (e) of this subsection must be met.
(b) When the percent solids of the biosolids
is seven percent or higher, the temperature of the biosolids must be 50°C
(122°F) or higher, the time period must be twenty minutes or longer, and
the temperature and time period must be determined using equation (1), except
when small particles of biosolids are heated by either warmed gases or an
immiscible liquid.
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Equation (1)
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D
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=
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131,700,000
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100.1400t
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Where:
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D = time in days
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t = temperature in degrees Celsius
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(c)
When the percent solids of the biosolids is seven percent or higher and small
particles of biosolids are heated by either warmed gases or an immiscible
liquid, the temperature of the biosolids must be 50°C (122°F) or
higher, the time period must be fifteen seconds or longer, and the temperature
and time period must be determined using equation (1).
(d) When the percent solids of the biosolids
is less than seven percent and the time period is at least fifteen seconds, but
less than thirty minutes, the temperature and time period must be determined
using equation (1).
(e) When the
percent solids of the biosolids is less than seven percent, the temperature of
the biosolids is 50°C (122°F) or higher, and the time period is thirty
minutes or longer, the temperature and time period must be determined using
equation (2).
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Equation (2)
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D
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=
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50,070,000
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100.1400t
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Where:
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D = time in days
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t = temperature in degrees Celsius
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(2)
Class A - Alternative 2: pH, Time,
Temperature, and Percent Solids.
(a)
Fecal coliform or Salmonella sp. bacteria
density. The density of fecal coliform in the biosolids must be
less than 1000 Most Probable Number per gram of total solids (dry weight basis)
or the density of Salmonella sp. bacteria in the biosolids
must be less than three Most Probable Number per four grams of total solids
(dry weight basis) at the time the biosolids are used, at the time the
biosolids are prepared for sale or give away in a bag or other container for
application to the land, or at the time the biosolids or material derived from
biosolids is prepared to meet the requirements for exemption in WAC
173-308-200, and the requirements
in (b) of this subsection must be met.
(b) The pH of the biosolids that are used
must be raised to above twelve and remain above twelve for seventy-two hours.
(i) The temperature of the biosolids must be
above 52°C (126°F) for twelve hours or longer during the period that
the pH of the biosolids is above twelve.
(ii) At the end of the seventy-two-hour
period during which the pH of the biosolids is above twelve, the biosolids must
be air dried to achieve a percent solids in the biosolids greater than fifty
percent.
(3)
Class A - Alternative 3: Processes to Further Reduce
Pathogens.
(a)
Fecal
coliform or Salmonella sp. bacteria density. The density of
fecal coliform in the biosolids must be less than 1000 Most Probable Number per
gram of total solids (dry weight basis) or the density of
Salmonella sp. bacteria in the biosolids must be less than
three Most Probable Number per four grams of total solids (dry weight basis) at
the time the biosolids are used, at the time the biosolids are prepared for
sale or give away in a bag or other container for application to the land, or
at the time the biosolids or material derived from biosolids is prepared to
meet the requirements for exemption in WAC
173-308-200, and one of the
requirements in (b)(i) through (vii) of this subsection must be met.
(b)
Processes to further reduce
pathogens. The biosolids must be treated in one of the
processes to further reduce pathogens described in this subsection.
(i)
Composting.
(A) Using either the within-vessel composting
method or the static aerated pile composting method, the temperature of the
biosolids must be maintained at 55°C (131°F) or higher for three
days.
(B) Using the windrow
composting method, the temperature of the biosolids must be maintained at
55°C (131°F) or higher for fifteen days or longer. During the period
when the compost is maintained at 55°C (131°F) or higher, there must be
a minimum of five turnings of the windrow.
(ii)
Heat drying. Biosolids
must be dried by direct or indirect contact with hot gases to reduce the
moisture content of the biosolids to ten percent or less and one of the
following requirements must be met.
(A) The
temperature of the biosolids particles must exceed 80°C
(176°F).
(B) The wet bulb
temperature of the gas in contact with the biosolids as the biosolids leave the
dryer must exceed 80°C (176°F).
(iii)
Heat treatment. Liquid
biosolids must be heated to a temperature of 180°C (356°F) or higher
for thirty minutes.
(iv)
Thermophilic aerobic digestion. Liquid biosolids must be
agitated with air or oxygen to maintain aerobic conditions and the mean cell
residence time of the biosolids must be at least ten days at 55 to 60°C
(131 to 140°F).
(v)
Beta ray irradiation. Biosolids must be irradiated with beta
rays from an accelerator at dosages of at least 1.0 megarad at room temperature
(ca. 20°C (68°F)).
(vi)
Gamma ray irradiation. Biosolids must be irradiated with gamma
rays from certain isotopes, such as Cobalt 60 and Cesium 137, at room
temperature (ca. 20°C (68°F)).
(vii)
Pasteurization. The
temperature of the biosolids must be maintained at 70°C (158°F) or
higher for thirty minutes or longer.
(4)
Class A - Alternative 4: Equivalent
Process to Further Reduce Pathogens.
(a)
Fecal coliform or
Salmonella sp. bacteria density. The density of fecal coliform
in the biosolids must be less than 1000 Most Probable Number per gram of total
solids (dry weight basis) or the density of Salmonella sp.
bacteria in the biosolids must be less than three Most Probable Number per four
grams of total solids (dry weight basis) at the time the biosolids are used, at
the time the biosolids are prepared for sale or give away in a bag or other
container for application to the land, or at the time the biosolids or material
derived from biosolids is prepared to meet the requirements for exemption in
WAC 173-308-200, and the requirements
in (b) of this subsection must be met.
(b) The biosolids must be treated in a
process that is equivalent to a process to further reduce pathogens. Pathogen
equivalency for biosolids applied to land under jurisdiction of the state of
Washington will be determined by the department or by the EPA with the approval
and concurrence of the department.
(5)
Class B - Alternative 1:
Testing. A minimum of seven samples of the biosolids must be collected
at the time the biosolids are used, and the geometric mean of the density of
fecal coliform of the samples must be less than 2,000,000 Most Probable Number
per gram of total solids (dry weight basis) or 2,000,000 Colony Forming Units
per gram of total solids (dry weight basis).
(6)
Class B - Alternative 2: Process to
Significantly Reduce Pathogens. The biosolids must be treated in one of
the processes to significantly reduce pathogens described in (a) through (e) of
this subsection.
(a)
Aerobic
digestion. The biosolids must be agitated with air or oxygen to
maintain aerobic conditions for a specific mean cell residence time at a
specific temperature. Values for the mean cell residence time and temperature
must be between forty days at 20°C (68°F) and sixty days at 15°C
(59°F).
(b)
Air
drying. The biosolids must be dried on sand beds or on paved or
unpaved basins. The biosolids must dry for a minimum of three months. During
two of the three months, the ambient average daily temperature must be above
0°C (32°F). During the air drying period, no additional material may be
added.
(c)
Anaerobic
digestion. The biosolids must be treated in the absence of air
for a specific mean cell residence time at a specific temperature. Values for
the mean cell residence time and temperature must be between fifteen days at 35
to 55°C (95 to 131°F) and sixty days at 20°C (68°F).
(d)
Composting.
Using the within-vessel, static aerated pile, or windrow composting methods,
the temperature of the biosolids must be raised to 40°C (104°F) or
higher and remain at 40°C (104°F) or higher for five days. For four
hours during the five days, the temperature in the compost pile must exceed
55°C (131°F).
(e)
Lime stabilization. Sufficient lime must be added
to the biosolids to raise the pH of the biosolids to twelve after two hours of
contact.
(7)
Class
B - Alternative 3: Equivalent Process to Significantly Reduce Pathogens.
The biosolids must be treated in a process that is equivalent to a process to
significantly reduce pathogens. Pathogen equivalency for biosolids applied to
land under jurisdiction of the state of Washington will be determined by the
department or by the EPA with the approval and concurrence of the
department.
Statutory Authority: Chapters 70.95J and
70.95 RCW. 07-12-010 (Order 06-06),
§ 173-308-170, filed 5/24/07, effective 6/24/07. Statutory Authority:
RCW
70.95J.020 and
70.95.255. 98-05-101 (Order
97-30), § 173-308-170, filed 2/18/98, effective
3/21/98.