7 Del. Admin. Code § 7202-6.0

Current through Register Vol. 28, No. 4, October 1, 2024

Section 7202-6.0 - Pathogens and Vector Attraction Reduction Requirements

6.1 Requirements for Pathogen Control.

6.1.1 All sewage sludges and domestic septage prepared for land application in Delaware must at a minimum be treated by one of the processes described in this section to significantly reduce pathogens (PSRP). Sludges treated to meet PSRP requirements will be defined as Class B sludges for the purpose of these regulations.

6.1.2 All sewage sludges prepared for Distribution and Marketing in Delaware must be treated by one of the processes to further reduce pathogens as described in the section (PFRP). Sludges treated to meet the PFRP requirements will be defined as Class A sludges for the purpose of these regulations.

6.1.3 Any sewage sludge or domestic septage prepared in a manner to meet the Class A or Class B requirements of this section must also meet the additional requirements found in these regulations prior to being applied to land, given away or sold in bulk or bag.

6.2 Class B Sludge - Sewage sludges processed to Significantly Reduce Pathogens (PSRP). (Septage included herein as sewage sludge)

6.2.1 Sludges prepared to meet the Class B requirements of this section must be processed by means of one of the following alternatives:

6.2.1.1 Class B Alternative 1.

6.2.1.1.1 Seven samples of the sewage sludge shall be collected at the time the sewage sludge is used or disposed.

6.2.1.1.2 The geometric mean of the density of fecal coliform in the samples 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).

6.2.1.2 Class B Alternative 2.

6.2.1.2.1 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 degrees Celsius and 60 days at 15 degrees Celsius.

6.2.1.2.2 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 zero degrees Celsius.

6.2.1.2.3 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 to 55 degrees Celsius and 60 days at 20 degrees Celsius.

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

6.2.1.2.5 Lime stabilization - Sufficient lime is added to the sewage sludge to raise the pH of the sewage sludge to 12 after 2 hours of contact.

6.2.1.3 Class B - Alternative 3. Sewage sludge 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 Department.

6.2.2 Monitoring and Reporting.

6.2.2.1 Sludge processed to significantly reduce pathogens must be monitored in accordance with the requirements described in the alternative used. Additional monitoring may be required by the Department as a condition of the preparer's permit.

6.2.2.2 The preparer must submit a report of process monitoring on a form provided by the Department. The frequency of reporting shall conform with the reporting frequency specified in Section 701 of the regulations or as specified in any permit issued for preparation.

6.3 Class A Sludge - Sludges processed to further reduce pathogens (PFRP).

6.3.1 Sludges prepared to meet Class A requirements must be processed by means of one of the following alternatives. The Class A pathogen requirements in Subsection 603(1)(a-f) shall be met either prior to meeting or at the same time the vector attraction reduction requirements in Subsection 604 (except for 604(f), (g) and (h)) are met.

6.3.1.1 Class A - Alternative 1.

6.3.1.1.1 Either 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 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) at the time the sewage sludge is prepared for sale or give away in as bag or other container for application to the land; or at the time the sewage sludge or material derived from sewage sludge is prepared to meet the requirements in Section 700.

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

6.3.1.1.2.1 When the percent solids of the sewage sludge is seven 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 (2), except when small particles of sewage sludge are heated by either warm gases or an immiscible liquid.

Where,

D = time in days.

t = temperature in degrees Celsius.

6.3.1.1.2.2 When the percent solids of the sewage sludge is seven 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 2.

6.3.1.1.2.3 When the percent solids of the sewage sludge is less than seven 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 (2).

6.3.1.1.2.4 When the percent solids of the sewage sludge is less than seven 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 (3).

Where,

D = time in days.

t = temperature in degrees Celsius.

6.3.1.2 Class A - Alternative 2.

6.3.1.2.1 Either 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 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) at the time the sewage sludge is used or disposed; at the time the sewage sludge is prepared for sale or give away in a bag or other container for application to the land; or at the time the sewage sludge or material derived from sewage sludge is prepared to meet the requirements in Section 700.

6.3.1.2.2

6.3.1.2.2.1 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.

6.3.1.2.2.2 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.

6.3.1.2.2.3 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 percent.

6.3.1.2.3 Class A - Alternative 3.

6.3.1.2.3.1 Either 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 the density of Salmonella sp. bacteria in sewage sludge shall be less than three Most Probable Number per four grams of total solids (dry weight basis) at the time the sewage sludge is used or disposed; at the time the sewage sludge is prepared for sale or give away in a bag or other container for application to the land; or at the time the sewage sludge is prepared to meet the requirements of Section 700.

6.3.1.2.3.2

6.3.1.2.3.2.1 The sewage sludge shall be analyzed prior to pathogen treatment to determine whether the sewage sludge contains enteric viruses.

6.3.1.2.3.2.2 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.

6.3.1.2.3.2.3 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.

6.3.1.2.3.2.4 After the entric virus reduction in paragraph (iii)(C) of this section 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 paragraph (ii)(C) of this section.

6.3.1.2.3.3

6.3.1.2.3.3.1 The sewage sludge shall be analyzed prior to pathogen treatment to determine whether the sewage sludge contains viable helminth ova.

6.3.1.2.3.3.2 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.

6.3.1.2.3.3.3 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.

6.3.1.2.3.3.4 After the viable helminth ova reduction in (iii)(C) 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 (iii)(C) of this subsection.

6.3.1.2.4 Class A - Alternative 4.

6.3.1.2.4.1 Either 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 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) at the time the sewage sludge is used or disposed; at the time the sewage sludge is prepared for sale or give away in a bag or other container for application to the land; or at the time the sewage sludge or material derived from sewage sludge is prepared to meet the requirements in Section 700.

6.3.1.2.4.2 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) at the time the sewage sludge is used or disposed; at the time the sewage sludge is prepared for sale or give away in a bag or other container for application to the land; or at the time the sewage sludge or material derived from sewage sludge is prepared to meet the requirements in Section 700 unless otherwise specified by the permitting authority.

6.3.1.2.4.3 The density of viable helminth ova in the sewage sludge shall be less than one per four grams of total solids (dry weight basis) at the time the sewage sludge is used or disposed; at the time the sewage sludge is prepared for sale or give away in a bag or other container for application to the land; or at the time the sewage sludge or material derived from sewage sludge is prepared to meet the requirements in Section 700, unless otherwise specified by the permitting authority.

6.3.1.2.5 Class A - Alternative 5.

6.3.1.2.5.1 Either 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 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) at the time the sewage sludge is used or disposed; at the time the sewage sludge is prepared for sale or given away in a bag or other container for application to the land; or at the time the sewage sludge or material derived from sewage sludge is prepared to meet the requirements in Section 700.

6.3.1.2.5.2 Sewage sludge that is used or disposed shall be treated in one of the Processes to Further Reduce Pathogens described below:

6.3.1.2.5.2.1 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 degrees Celsius or higher for three days.

Using the windrow composting method, the temperature of the sewage sludge is maintained at 55 degrees or higher for 15 days or longer. During the period when the compost is maintained at 55 degrees or higher, there shall be a minimum of five turnings of the windrow.

6.3.1.2.5.2.2 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 percent or lower. Either the temperature of the sewage sludge particles exceeds 80 degrees Celsius or the wet bulb temperature of the gas in contact with the sewage sludge as the sewage sludge leaves the dryer exceeds 80 degrees Celsius.

6.3.1.2.5.2.3 Heat treatment - Liquid sewage sludge is heated to a temperature of 180 degrees Celsius or higher for 30 minutes.

6.3.1.2.5.2.4 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 to 60 degrees Celsius.

6.3.1.2.5.2.5 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 degrees Celsius).

6.3.1.2.5.2.6 Gamma ray irradiation - Sewage sludge is irradiated with gamma rays from certain isotopes, such as Cobalt 60 and Cesium 137, at room temperature (ca. 20 degrees Celsius).

6.3.1.2.5.2.7 Pasteurization - The temperature of the sewage sludge is maintained at 70 degrees Celsius or higher for 30 minutes or longer.

6.3.1.2.6 Class A - Alternative 6.

6.3.1.2.6.1 Either 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 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) at the time the sewage sludge is used or disposed; at the time the sewage sludge is prepared for sale or given away in a bag or other container for application to the land; or at the time the sewage sludge is prepared to meet the requirements in Section 700.

6.3.1.2.6.2 Sewage sludge 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 permitting authority.

6.3.2 Monitoring and Reporting.

6.3.2.1 Any sludge processed to further reduce pathogens must be monitored in accordance with the requirements described in the alternative used. Additional monitoring may be required by the Department as a permit condition.

6.3.2.2 Anyone who prepares a Class A sludge must report the results of all monitoring for the processing alternative used on a form provided by the Department. The frequency of reporting shall comply with the reporting frequency described in Section 701 or as specified in the permit.

6.4 Vector Attraction Reduction Requirements.

6.4.1 All sludge prepared for land application and for sale or give away in bulk or bag must meet the requirements of this subsection for Vector Attraction Reduction in addition to the requirements in Section 700 and in Subsections 402, 602 and 603.

6.4.2 Vector Attraction Reduction requirements may be achieved by application of one of the following processes:

6.4.2.1 The mass of volatile solids in the sewage sludge shall be reduce by a minimum of 38 percent (see calculation procedures in "Environmental Regulations and Technology - Control of Pathogens and Vector Attraction in Sewage Sludge", EPA-625/R-92/013, 1992, U.S. Environmental Protection Agency, Cincinnati, Ohio 45268).

6.4.2.2 When the 38 percent volatile solids reduction requirement in (2)(a) cannot be met for an anaerobically digested sewage sludge, vector attraction reduction can be demonstrated by digesting a portion of the previously 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. When 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.

6.4.2.3 When the 38 percent volatile solids reduction requirement in (2)(a) cannot be met for an aerobically digested sewage sludge, vector attraction reduction can be demonstrated by digesting a portion of the previously digested sewage sludge that has a percent solids of two percent or less aerobically in the laboratory in a bench-scale unit for 30 additional days at 20 degrees Celsius. When 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.

6.4.2.4 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.

6.4.2.5 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.

6.4.2.6 The pH of sewage sludge shall be raised to 12 or higher by alkaline addition and, without the addition of more alkali shall remain at 12 or higher for two hours and then at 11.5 or higher for an additional 22 hours.

6.4.2.7 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.

6.4.2.8 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.

6.4.2.9 Sewage sludge shall be injected below the surface of the land.

6.4.2.10 No significant amount of the sewage sludge shall be present on the land surface within one hour after the sewage sludge is injected.

6.4.2.11 When the sewage sludge that is injected below the surface of the land is Class A with respect to pathogens, the sewage sludge shall be injected below the land surface within eight hours after being discharged from the pathogen treatment process.

6.4.2.12 Sewage sludge applied to the land surface disposal site shall be incorporated into the soil within six hours after application to or placement on the land.

6.4.2.13 When sewage sludge that is incorporated into the soil is Class A with respect to pathogens, the sewage sludge shall be applied to or placed on the land within eight hours after being discharged from the pathogen treatment process.

6.4.2.14 The pH of domestic septage shall be raised to 12 or higher by alkaline addition and, without the addition of more alkali, shall remain at 12 or higher for 30 minutes.

6.4.3 Vector Attraction Reduction requirements may also be met by employment of any one of the following practices in lieu of a specific Vector Reduction process found in 604 (2)(a-j).

6.4.3.1 One of the vector attraction reduction requirements in Subsection 604(2)(a) through (2)(j) shall be met when bulk sewage sludge is applied to agricultural land, forest, a public contact site, or a reclamation site.

6.4.3.2 One of the vector attraction reduction requirements in Subsection 604(2)(a) through (2)(h) shall be met when bulk sewage sludge is applied to a lawn or a home garden.

6.4.3.3 One of the vector attraction reduction requirements in Subsection 604(2)(a) through (2)(h) shall be met when sewage sludge is sold or given away in a bag or other container for application to the land.

6.4.3.4 One of the vector attraction reduction requirements in Subsection 604(2)(i), (2)(j), or (2)(k) shall be met when domestic septage is applied to agricultural land, forest, or a reclamation site.

6.4.4 Monitoring and Reporting.

6.4.4.1 Any sludge prepared for land application or for sale or give away in bulk or bag must be monitored for vector attraction reduction according to the conditions specified in the processes outlined in Subsection 604(2)(a-j) or practices outlined in Subsection 604(3)(a-d).

6.4.4.2 Any person that prepares a sludge for land application or for sale or give away in bulk or bag must report vector attraction reduction monitoring results to the Department on a form provided by the Department. The frequency of reporting must comply with the schedule outlined in Subsection 701 of these regulations or as specified in the permit.

7 Del. Admin. Code § 7202-6.0