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Virginia Administrative Code
Title 9. Environment
Agency 25. State Water Control Board
Chapter 31. Virginia Pollutant Discharge Elimination System (VPDES) Permit Regulation
8/11/2020

9VAC25-31-710. Pathogens.

A. Biosolids - Class A.

1. The requirement in subdivision 2 of this subsection and the requirements in either subdivisions 3, 4, 5, 6, 7, or 8 of this subsection shall be met for a biosolids to be classified Class A with respect to pathogens.

2. The Class A pathogen requirements in subdivisions 3 through 8 of this subsection shall be met either prior to meeting or at the same time the vector attraction reduction requirements in 9VAC25-31-720, except the vector attraction reduction requirements in 9VAC25-31-720 B 6 through B 8, are met.

3. Class A - Alternative 1.

a. Either the density of fecal coliform in the biosolids shall be less than 1,000 Most Probable Number per gram of total solids (dry weight basis), or the density of Salmonella sp. bacteria in the biosolids shall be less than three Most Probable Number per four grams of total solids (dry weight basis) at the time the biosolids is used or disposed; at the time the biosolids is 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 in 9VAC25-31-510 B, C, E, or F.

b. The temperature of the sewage sludge that is used or disposed shall be maintained at a specific value for a period of time.

(1) When the percent solids of the sewage sludge is 7.0% or higher, the temperature of the sewage sludge shall be 50°C 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.

EQUATION (1)

D = 131,700,000/100.1400t

D = time in days

t = temperature in degrees Celsius

(2) When the percent solids of the sewage sludge is 7.0% 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°C or higher; the time period shall be 15 seconds or longer; and the temperature and time period shall be determined using equation (1).

(3) When the percent solids of the sewage sludge is less than 7.0% 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).

(4) When the percent solids of the sewage sludge is less than 7.0%; the temperature of the sewage sludge is 50°C 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

D = time in days

t = temperature in degrees Celsius

4. Class A - Alternative 2.

a. Either the density of fecal coliform in the biosolids shall be less than 1,000 Most Probable Number per gram of total solids (dry weight basis), or the density of Salmonella sp. bacteria in the biosolids shall be less than three Most Probable Number per four grams of total solids (dry weight basis) at the time the biosolids is used or disposed; at the time the biosolids is 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 in 9VAC25-31-510 B, C, E, or F.

b. (1) The pH of the sewage sludge that is used or disposed shall be raised to above 12 and shall remain above 12 for 72 hours.

(2) The temperature of the sewage sludge shall be above 52°C for 12 hours or longer during the period that the pH of the sewage sludge is above 12.

(3) 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%.

5. Class A - Alternative 3.

a. Either the density of fecal coliform in the biosolids shall be less than 1,000 Most Probable Number per gram of total solids (dry weight basis), or the density of Salmonella sp. bacteria in biosolids shall be less than three Most Probable Number per four grams of total solids (dry weight basis) at the time the biosolids is used or disposed; at the time the biosolids is 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 in 9VAC25-31-510 B, C, E, or F.

b. (1) The sewage sludge shall be analyzed prior to pathogen treatment to determine whether the sewage sludge contains enteric viruses.

(2) When the density of enteric viruses in the sewage sludge prior to pathogen treatment is less than one Plaque-forming Unit per four grams of total solids (dry weight basis), the sewage sludge is Class A with respect to enteric viruses until the next monitoring episode for the sewage sludge.

(3) When the density of enteric viruses in the sewage sludge prior to pathogen treatment is equal to or greater than one Plaque-forming Unit per four grams of total solids (dry weight basis), the sewage sludge is Class A with respect to enteric viruses when the density of enteric viruses in the sewage sludge after pathogen treatment is less than one Plaque-forming Unit per four grams of total solids (dry weight basis) and when the values or ranges of values for the operating parameters for the pathogen treatment process that produces the sewage sludge that meets the enteric virus density requirement are documented.

(4) After the enteric virus reduction in subdivision 5 b (3) of this subsection is demonstrated for the pathogen treatment process, the sewage sludge continues to be Class A with respect to enteric viruses when the values for the pathogen treatment process operating parameters are consistent with the values or ranges of values documented in subdivision 5 b (3) of this subsection.

c. (1) The sewage sludge shall be analyzed prior to pathogen treatment to determine whether the sewage sludge contains viable helminth ova.

(2) When the density of viable helminth ova in the sewage sludge prior to pathogen treatment is less than one per four grams of total solids (dry weight basis), the sewage sludge is Class A with respect to viable helminth ova until the next monitoring episode for the sewage sludge.

(3) When the density of viable helminth ova in the sewage sludge prior to pathogen treatment is equal to or greater than one per four grams of total solids (dry weight basis), the sewage sludge is Class A with respect to viable helminth ova when the density of viable helminth ova in the sewage sludge after pathogen treatment is less than one per four grams of total solids (dry weight basis) and when the values or ranges of values for the operating parameters for the pathogen treatment process that produces the sewage sludge that meets the viable helminth ova density requirement are documented.

(4) After the viable helminth ova reduction in subdivision 5 c (3) of this subsection is demonstrated for the pathogen treatment process, the sewage sludge continues to be Class A with respect to viable helminth ova when the values for the pathogen treatment process operating parameters are consistent with the values or ranges of values documented in subdivision 5 c (3) of this subsection.

6. Class A - Alternative 4.

a. Either the density of fecal coliform in the biosolids shall be less than 1,000 Most Probable Number per gram of total solids (dry weight basis), or the density of Salmonella sp. bacteria in the biosolids shall be less than three Most Probable Number per four grams of total solids (dry weight basis) at the time the biosolids is used or disposed; at the time the biosolids is 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 in 9VAC25-31-510 B, C, E, or F.

b. The density of enteric viruses in the biosolids shall be less than one Plaque-forming Unit per four grams of total solids (dry weight basis) at the time the biosolids is used or disposed; at the time the biosolids is 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 in 9VAC25-31-510 B, C, E, or F, unless otherwise specified by the board.

c. The density of viable helminth ova in the biosolids shall be less than one per four grams of total solids (dry weight basis) at the time the biosolids is used or disposed; at the time the biosolids is 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 in 9VAC25-31-510 B, C, E, or F unless otherwise specified by the board.

7. Class A - Alternative 5.

a. Either the density of fecal coliform in the biosolids shall be less than 1,000 Most Probable Number per gram of total solids (dry weight basis), or the density of Salmonella, sp. bacteria in the biosolids shall be less than three Most Probable Number per four grams of total solids (dry weight basis) at the time the biosolids is used or disposed; at the time the biosolids is 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 in 9VAC25-31-510 B, C, E, or F.

b. Biosolids that is used or disposed shall be treated in one of the processes to further reduce pathogens described in subsection E of this section.

8. Class A - Alternative 6.

a. Either the density of fecal coliform in the biosolids shall be less than 1,000 Most Probable Number per gram of total solids (dry weight basis), or the density of Salmonella, sp. bacteria in the biosolids shall be less than three Most Probable Number per four grams of total solids (dry weight basis) at the time the biosolids is used or disposed; at the time the biosolids is 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 in 9VAC25-31-510 B, C, E, or F.

b. Biosolids that is used or disposed shall be treated in a process that is equivalent to a process to further reduce pathogens, as determined by the board.

B. Biosolids - Class B.

1. The requirements in either subdivision 3, 4, or 5 of this subsection shall be met for a biosolids to be classified Class B with respect to pathogens.

2. The site restrictions in subdivision 6 of this subsection shall be met when biosolids that meets the Class B pathogen requirements in subdivision 3, 4, or 5 of this subsection is applied to the land.

3. Class B - Alternative 1.

a. Seven representative samples of the biosolids that is used or disposed shall be collected.

b. The geometric mean of the density of fecal coliform in the samples collected in subdivision 3 a of this subsection shall be less than either 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).

4. Class B - Alternative 2. Biosolids that is used or disposed shall be treated in one of the processes to significantly reduce pathogens described in subsection D of this section.

5. Class B - Alternative 3. Biosolids that is used or disposed shall be treated in a process that is equivalent to a process to significantly reduce pathogens, as determined by the board.

6. Site restrictions.

a. Food crops with harvested parts that touch the biosolids/soil mixture and are totally above the land surface shall not be harvested for 14 months after application of biosolids.

b. Food crops with harvested parts below the surface of the land shall not be harvested for 20 months after application of biosolids when the biosolids remains on the land surface for four months or longer prior to incorporation into the soil.

c. Food crops with harvested parts below the surface of the land shall not be harvested for 38 months after application of biosolids when the biosolids remains on the land surface for less than four months prior to incorporation into the soil.

d. Food crops, feed crops, and fiber crops shall not be harvested for 30 days after application of biosolids.

e. Animals shall not be grazed on the land for 30 days after application of biosolids.

f. Turf grown on land where biosolids is applied shall not be harvested for one year after application of the biosolids when the harvested turf is placed on either land with a high potential for public exposure or a lawn, unless otherwise specified by the board.

g. Public access to land with a high potential for public exposure shall be restricted for one year after application of biosolids.

h. Public access to land with a low potential for public exposure shall be restricted for 30 days after application of biosolids.

C. Domestic septage: The site restrictions in subdivision B 6 of this section shall be met when domestic septage is applied to agricultural land, forest, or a reclamation site.

D. Processes to significantly reduce pathogens (PSRP).

1. Aerobic digestion. Sewage sludge is 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 shall be between 40 days at 20°C and 60 days at 15°C.

2. Air drying. Sewage sludge is dried on sand beds or on paved or unpaved basins. The sewage sludge dries for a minimum of three months. During two of the three months, the ambient average daily temperature is above 0°C.

3. Anaerobic digestion. Sewage sludge is 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 shall be between 15 days at 35°C to 55°C and 60 days at 20°C.

4. Composting. Using either the within-vessel, static aerated pile, or windrow composting methods, the temperature of the sewage sludge is raised to 40°C or higher and remains at 40°C or higher for five days. For four hours during the five days, the temperature in the compost pile exceeds 55°C.

5. Lime stabilization. Sufficient lime is added to the sewage sludge to raise the pH of the sewage sludge to 12 after two hours of contact.

E. Processes to further reduce pathogens (PFRP).

1. Composting. Using either the within-vessel composting method or the static aerated pile composting method, the temperature of the sewage sludge is maintained at 55°C or higher for three days. Using the windrow composting method, the temperature of the sewage sludge is maintained at 55°C or higher for 15 days or longer. During the period when the compost is maintained at 55°C or higher, there shall be a minimum of five turnings of the windrow.

2. Heat drying. Sewage sludge is dried by direct or indirect contact with hot gases to reduce the moisture content of the sewage sludge to 10.0% or lower. Either the temperature of the sewage sludge particles exceeds 80°C or the wet bulb temperature of the gas in contact with the sewage sludge as the sewage sludge leaves the dryer exceeds 80°C.

3. Heat treatment. Liquid sewage sludge is heated to a temperature of 180°C or higher for 30 minutes.

4. Thermophilic aerobic digestion. Liquid sewage sludge is agitated with air or oxygen to maintain aerobic conditions and the mean cell residence time of the sewage sludge is 10 days at 55°C to 60°C.

5. Beta ray irradiation. Sewage sludge is irradiated with beta rays from an accelerator at dosages of at least 1.0 megarad at room temperature (ca. 20°C).

6. Gamma ray irradiation. Sewage sludge is irradiated with gamma rays from certain isotopes, such as Cobalt 60 and Cesium 137, at dosages of at least 1.0 megarad at room temperature (ca. 20°C).

7. Pasteurization. The temperature of the sewage sludge is maintained at 70°C or higher for 30 minutes or longer.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia.

Historical Notes

Derived from Volume 12, Issue 20, eff. July 24, 1996; amended, Virginia Register Volume 16, Issue 25, eff. September 27, 2000; Volume 29, Issue 24, eff. September 1, 2013.

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