When vector attraction reduction is accomplished prior to
application of biosolids to the land, the requirements in one of subsections
(1) through (6) of this section must be met.
The vector attraction reduction requirements in subsection (1),
(2), or (3) of this section must be met at the same time or after the Class A
pathogen requirements in WAC
173-308-170.
(1)
Alternative 1: Volatile Solids
Reduction. The mass of volatile solids in the biosolids must be reduced
by a minimum of thirty-eight percent.
(a)
Bench-scale test for anaerobically digested
solids. When the thirty-eight percent volatile solids reduction
requirement in this subsection cannot be met for anaerobically digested
biosolids, vector attraction reduction can be demonstrated by digesting a
portion of the previously digested biosolids anaerobically in the laboratory in
a bench-scale unit for forty additional days at a temperature between 30 and
37°C (86 and 98.6°F). After the forty-day period, the vector attraction
reduction requirement is met if the volatile solids in the biosolids at the
beginning of that period are reduced by less than seventeen percent.
(b)
Bench-scale test for
aerobically digested solids. When the thirty-eight percent
volatile solids reduction requirement in this subsection cannot be met for
aerobically digested biosolids, vector attraction reduction can be demonstrated
by digesting a portion of the previously digested biosolids that has a percent
solids of two percent or less aerobically in the laboratory in a bench-scale
unit for thirty additional days at 20°C (68°F). After the thirty-day period,
the vector attraction reduction requirement is met if the volatile solids in
the biosolids at the beginning of that period are reduced by less than fifteen
percent.
(2)
Alternative 2: Specific Oxygen Uptake Rate (SOUR). The specific
oxygen uptake rate (SOUR) for biosolids treated in an aerobic process must be
less than or equal to 1.5 milligrams of oxygen per hour per gram of total
solids (dry weight basis) at a temperature of 20°C (68°F).
(3)
Alternative 3: Aerobic
Process. The biosolids must be treated in an aerobic process for
fourteen days or longer. During that time, the temperature of the biosolids
must be higher than 40°C (104°F) and the average temperature of the biosolids
must be higher than 45°C (113°F).
(4)
Alternative 4: pH
Adjustment. The pH of the biosolids must be raised to twelve or higher
by alkali addition and, without the addition of more alkali, must remain at
twelve or higher for two hours and then at 11.5 or higher for an additional
twenty-two hours.
(5)
Alternative 5: Percent Solids for Stabilized Solids. For biosolids
that do not contain unstabilized solids generated in a primary wastewater
treatment process, the percent solids must be equal to or greater than
seventy-five percent based on the moisture content and total solids prior to
mixing with other materials.
(6)
Alternative 6: Percent Solids for Unstabilized Solids. For
biosolids that contain unstabilized solids generated in a primary wastewater
treatment process, the percent solids must be equal to or greater than ninety
percent based on the moisture content and total solids prior to mixing with
other materials.
