Iowa Administrative Code › Agency 567 - Environmental Protection Commission › Title IV - Wastewater Treatment and Disposal › Chapter 67 - Standards for the Land Application of Sewage Sludge › Rule 567-67.7 - Land Application Requirements for Class I Sewage Sludge

Current through Register Vol. 47, No. 3, July 24, 2024
(1)
Class I
				sewage sludge criteria.
Class I sewage sludge is sewage sludge that
				meets the pollutant concentrations in paragraph 67.7(1)
"a,"
the Class A pathogen reduction requirements in paragraph
				67.7(1)
"b,"
and the vector attraction reduction requirements
				in paragraph 67.7(1)
"c"
below.
a.
Pollutant concentrations for Class
				I sewage sludge.
The concentration of each pollutant in the sewage
				sludge shall not exceed the concentration for the pollutant in Table 1.
TABLE 1-POLLUTANT CONCENTRATIONS
Pollutant
Monthly Average Concentration milligrams per
								kilogram*
Arsenic
41
Cadmium
39
Copper
1500
Lead
300
Mercury
17
Nickel
420
Selenium
100
Zinc
2800
*Dry weight basis
b.
Class A pathogen requirements for
				Class I sewage sludge.
The sewage sludge shall comply with
				subparagraphs 67.7(1)
"b"
(1) and (2) below.
(1) The sewage sludge shall comply with one
				of the following monitoring processes. Compliance with pathogen density shall
				not be based on an average value. Each individual sample result shall meet the
				numerical pathogen standards.
1. The density
				of fecal coliform in the sewage sludge shall be less than 1000 Most Probable
				Number per gram of total solids (dry weight basis), or
2. The density of Salmonella sp. bacteria in
				the sewage sludge shall be less than three Most Probable Number per four grams
				of total solids (dry weight basis).
(2) The sewage sludge shall comply with one
				of the following analytical and treatment processes.
1. The temperature of the sewage sludge shall
				be maintained at a specific value for a period of time using one of the
				procedures detailed below.
* When the percent solids of the sewage sludge is 7 percent
				  or higher, the temperature of the sewage sludge shall be 50 degrees Celsius or
				  higher; the time period shall be 20 minutes or longer; and the temperature and
				  time period shall be determined using Equation 1, except when small particles
				  of sewage sludge are heated by either warmed gases or an immiscible
				  liquid.
* When the percent solids of the sewage sludge is 7 percent
				  or higher and small particles of sewage sludge are heated by either warmed
				  gases or an immiscible liquid, the temperature of the sewage sludge shall be 50
				  degrees Celsius or higher; the time period shall be 15 seconds or longer; and
				  the temperature and time period shall be determined using Equation 1.
* When the percent solids of the sewage sludge is less than 7
				  percent and the time period is at least 15 seconds, but less than 30 minutes,
				  the temperature and time period shall be determined using Equation 1.
Equation 1:
D = 131,700,000/100.1400t
Where D = time in days; t = temperature in degrees
				  Celsius.
* When the percent solids of the sewage sludge is less than 7
				  percent; the temperature of the sewage sludge is 50 degrees Celsius or higher;
				  and the time period is 30 minutes or longer, the temperature and time period
				  shall be determined using Equation 2.
Equation 2:
D = 50,070,000/100.1400t
Where D = time in days; t = temperature in degrees
				  Celsius.
2. The sewage
				sludge shall meet all of the following requirements:
* The pH of the sewage sludge shall be raised to above 12 and
				  shall remain above 12 for 72 hours;
* The temperature of the sewage sludge shall be above 52
				  degrees Celsius for 12 hours or longer during the period that the pH of the
				  sewage sludge is above 12; and
* At the end of the 72-hour period during which the pH of the
				  sewage sludge is above 12, the sewage sludge shall be air dried to achieve a
				  percent solids in the sewage sludge greater than 50 percent.
3. Sewage sludge treated in other known
				processes shall be analyzed prior to pathogen treatment to determine whether
				the sewage sludge contains enteric viruses and viable helminth ova. The density
				of enteric viruses in the sewage sludge after pathogen treatment shall be less
				than one plaque-forming unit per four grams of total solids (dry weight basis).
				The density of viable helminth ova in the sewage sludge after pathogen
				treatment shall be less than one per four grams of total solids (dry weight
				basis). Once the process has been demonstrated to achieve the required pathogen
				reduction, the process must be operated under the same conditions that were
				used during the demonstration.
4.
				Sewage sludge treated by unknown processes or by processes operating at
				conditions less stringent than the operating conditions at which the sewage
				sludge could qualify as Class I under other alternatives shall be analyzed
				prior to pathogen treatment to determine whether the sewage sludge contains
				enteric viruses and viable helminth ova. The density of enteric viruses in the
				sewage sludge shall be less than one plaque-forming unit per four grams of
				total solids (dry weight basis). The density of viable helminth ova in the
				sewage sludge shall be less than one per four grams of total solids (dry weight
				basis).
5. Sewage sludge shall be
				treated in one of the Processes to Further Reduce Pathogens (PFRP) described in
				567-67.11(455B).
6. Sewage sludge
				shall be treated in a process that is equivalent to a Process to Further Reduce
				Pathogens (PFRP), as determined by the department.
c.
Vector
				attraction reduction requirements for Class I sewage sludge.
The
				sewage sludge shall meet one of the following vector attraction reduction
				requirements.
(1) The mass of volatile solids
				in the sewage sludge shall be reduced by a minimum of 38 percent.
(2) Digest a portion of the previously
				anaerobically digested sewage sludge anaerobically in the laboratory in a
				bench-scale unit for 40 additional days at a temperature between 30 and 37
				degrees Celsius. If, at the end of the 40 days, the volatile solids in the
				sewage sludge at the beginning of that period is reduced by less than 17
				percent, vector attraction reduction is achieved.
(3) Digest a portion of the previously
				aerobically digested sewage sludge that has 2 percent solids or less
				aerobically in the laboratory in a bench-scale unit for 30 additional days at
				20 degrees Celsius. If, at the end of the 30 days, the volatile solids in the
				sewage sludge at the beginning of that period is reduced by less than 15
				percent, vector attraction reduction is achieved.
(4) The specific oxygen uptake rate (SOUR)
				for sewage sludge treated in an aerobic process shall be equal to or less than
				1.5 milligrams of oxygen per hour per gram of total solids (dry weight basis)
				at a temperature of 20 degrees Celsius.
(5) Sewage sludge shall be treated in an
				aerobic process for 14 days or longer. During that time, the temperature of the
				sewage sludge shall be higher than 40 degrees Celsius and the average
				temperature of the sewage sludge shall be higher than 45 degrees
				Celsius.
(6) The pH of sewage
				sludge shall be raised to 12 or higher, measured at 25 degrees Celsius, by
				alkali addition and, without the addition of more alkali, shall remain at 12 or
				higher for 2 hours and then at 11.5 or higher for an additional 22
				hours.
(7) The percent solids of
				sewage sludge that does not contain unstabilized solids generated in a primary
				wastewater treatment process shall be equal to or greater than 75 percent based
				on the moisture content and total solids prior to mixing with other
				materials.
(8) The percent solids
				of sewage sludge that contains unstabilized solids generated in a primary
				wastewater treatment process shall be equal to or greater than 90 percent based
				on the moisture content and total solids prior to mixing with other
				materials.
(9) Sewage sludge shall
				be injected below the surface of the land and no significant amount of the
				sewage sludge shall be present on the land surface within one hour after the
				sewage sludge is injected.
(10)
				Sewage sludge applied to the land surface or placed on a surface disposal site
				shall be incorporated into the soil within six hours after application to or
				placement on the land.