Surface disposal of biosolids

Standards (40 CFR Part 503) for the use or disposal of sewage sludge were published in the Federal Register on February 19, 1993 (Bastian, 1993; Crites et al., 2000; USEPA, 1994a). The regulation discusses land application, surface disposal, pathogen and vector attraction reduction, and incineration. Land application is defined as beneficial use of the sludge at agronomic rates, while all other placement on the land is considered to be surface disposal. Heavy-metal concentrations are limited by two levels of sludge quality: pollutant ceiling concentrations and pollutant concentrations ("high quality"). Two classes of quality with regard to pathogen densities (class A and class B) are described. Two types of vector attraction reduction are presented: sewage sludge processing or the use of physical barriers.

The USEPA rules were evaluated by the National Research Council (NRC, 2002) and the results were presented in a report issued in July 2002. The NRC concluded that there was no documented scientific evidence that the regulations had failed to protect the public health; however, uncertainty on possible health effects exists. Further research was recommended to address public health concerns, scientific uncertainties, and data gaps in the sewage sludge standards. A response to the NRC review was published by the USEPA (2003c), and the plan to conform to the recommendations in the NRC report was presented. Beecher et al. (2004) reviewed the current understanding of risk perception, risk communication, and public participation with regard to biosolids management. They agree with the NRC (2002) that risk assessment is subjective and is a blending of science and judgment. Choosing models to address the issues is difficult, and data availability is limited.

For land application, sewage sludge or material derived from sewage sludge must as a minimum meet the pollutant ceiling concentrations, class B requirements for pathogens, and vector attraction reduction requirements. Cumulative pollutant loading rates are required for sewage sludges that meet the pollutant ceiling concentrations but do not satisfy the pollutant concentrations.

The concepts described in this section are generally limited to those operations designed for treatment or reuse of the sludge via land application or surface disposal. Landfills and other "high-quality" surface disposal practices are covered in other texts (USEPA, 1978, 1979, 1981b). Some degree of sludge stabilization is typically used prior to land application or surface disposal, and dewatering may be economically desirable; however, systems are designed so the receiving land surface provides the final sludge treatment as well as utilizing the sludge organic matter and nutrients. These natural sludge management systems can be grouped into two major types: land application and surface disposal.

Land application systems involve the vegetation, soils, and related ecosystem for final treatment and utilization of the sludge. The design sludge loadings are based on the nutrient and organic needs of the site as constrained by metals, toxics, vector control, and pathogen content of the sludge (USEPA, 1981b). Systems in this group include agricultural and forest operations where repetitive sludge applications are planned over a long term, as well as reclamation projects where the sludge is used to reclaim and revegetate disturbed land. The site is designed and then operated so no future restrictions are placed on the use of the land. The flowchart in Figure 9.3 presents a series of steps to follow that make it easy to determine if land application of sludge is appropriate (Sieger and Herman, 1993). A process design manual for land application of sewage sludge and domestic septage is available from the USEPA (1995c).

Surface disposal systems depend almost entirely on reactions in the upper soil profile for treatment. Vegetation is typically not an active treatment component, and no attempt is made to design for the beneficial utilization of sludge organic matter or nutrients. The site is often dedicated for this purpose, and restrictions may be placed on future use of the land, especially for crop production involving the human food chain. Systems receiving biodegradable sludges utilize acclimated soil organisms for that purpose and are designed for periodic loading and rest periods. Petroleum sludges and similar industrial wastes are often managed in this way. Figure 9.4 is a flowchart that makes it easy to determine the applicability of surface disposal of sludges (Sigmund and Sieger, 1993). A process

Are the pollutants in the sludge or the material derived from the sludge less than or equal to the limits in Table 9.15?

Consider other land disposal (surface disposal) and incineration under Part 503 Regulations, or additional treatment. Consider also landfilling with municipal solid waste or other wastes, or incineration with other wastes. NOTE: Other regulations and requirements may be applicable to other disposal methods.

You may apply sludge to land providing the following are met:

Congratulations! You have an exceptionally high-quality sludge and you are not limited by the General Requirements,a Management Practices" and Tables 9.14 and 9.16, for sludge used on:

Agricultural land Forests

Public contact sites Reclamation sites Rangeland Pastures

Lawn or home gardens'1

a Unless otherwise required by the EPA regional administrator or the state director of a state with an approved sludge management program.

b For bulk or sold/given away material derived from exceptionally high-quality sludge, the material is exempt from record-keeping, monitoring, and reporting requirements.

Are the pollutants in the sludge or the material derived from the sludge less than or equal to the limits in Table 9.15?

Does the sludge meet class B pathogen requirements and associated site restrictions?

Does the sludge meet one of the vector attraction reduction criteria 1-10?_

I Yes

Are the pollutants in the sludge or the material derived from the sludge less than or equal to the limits in Table 9.15?

Consider developing or revising an industrial pretreatment program, pollution prevention program, etc.

You may apply sludge to land providing the following are met:

Cumulative pollutant loading limits in Table 9.14 apply to sludge application on:

Agricultural land Forests

Public contact sites Reclamation sites Rangeland Pastures

Annual pollutant loading rates in Table 9.16 apply to sludge that is sold or given away in a bag or other container for application to land. Must label bags/ containers with defined information. Bulk sludge may not be applied to lawns or home gardens.

You may apply sludge to land providing the following are met:

Cumulative pollutant loading limits in Table 9.14 apply to sludge application on:

Agricultural land Forests

Public contact sites Reclamation sites Rangeland Pastures

Sludge may not be given away or sold in a bag or other container for application to land. Sludge may not be applied to lawns or home gardens.

You may apply sludge to land providing the following are met:

Sludge may be applied to the following without annual or cumulative pollutant limits:

Agricultural land Forests

Public contact sites Reclamation sites Rangeland Pastures

Sludge may not be given away or sold in a bag or other container for application to land. Sludge may not be applied to lawns or home gardens.

All general requirements; management practices, such as not exceeding agronomic rates for nitrogen; recordkeeping; monitoring; and reporting requirements must be met.

FIGURE 9.3 Flowchart to determine the applicability of land application of sludge. (From Sieger, R.B. and Herman, G.J., Water Eng. Manage, 140(8), 30-31, 1993. With permission.)

So, you want to dispose of sewage sludge by the surface disposal method?

Is sludge covered with soil or other material at the end of each operating day? (See vector attraction reduction criteria 11)

Will (does) the surface disposal unit contaminate the aquifer? If not, a liner and leachate collection system may not be required.

Is the sludge hazardous?

Consider other disposal methods presented in the Part 503 regulations or additional treatment. Consider developing or revising an industrial pretreatment, a pollution prevention program, etc. Consider also landfilling with municipal solid wastes or other waste, or incineration with other waste. Consider a liner and leachate collection system, and meet other applicable regulations and requirements. NOTE: Other regulations and requirements may be applicable to other disposal methods.

Will the permitting authority consider and set specific pollutant limits for this surface disposal unit?

Are the pollutants in the sludge less than or equal to the limits in Part 503 regulations?

Is the limit of the surface disposal unit greater than 150 meters (492 feet) away from the property line?

Will the permitting authority consider and set specific pollutant limits for this surface disposal unit?

Yes

Does the sludge meet the class A or class B Pathogen requirements?

Is the concentration for each pollutant (arsenic, chromium, or nickel) less than or equal to the limits at the distances noted in Part 503 regulations?

I Yes

Does the sludge meet one of the vector attraction reduction criteria 1-10?

Does the sludge meet one of the vector attraction reduction criteria 1-10?

You can surface disposal of sludge in accordance with the Part 503 Regulations provided General Requirements, Management Requirements, record keeping, Monitoring and Reporting Requirements are met.

FIGURE 9.4 Flowchart to determine the applicability of surface disposal of sludge. (From Sigmund, T.W. and Sieger, R.B., Water Eng. Manage., 140(9), 18-19, 1993. With permission.)

TABLE 9.12

Human Hazard Quotient (HQ) Values >1 at the 95th Percentile of the HQ Distribution by Pathway for the Agricultural Land Application Scenario

TABLE 9.12

Human Hazard Quotient (HQ) Values >1 at the 95th Percentile of the HQ Distribution by Pathway for the Agricultural Land Application Scenario

CASRN

Chemical

Pathway

Receptor

HQ

14797-65-0

Nitrite

Irrigation of surface water

Child

1.1

Total ingestion

Child

1.3

7440-22-4

Silver

Ingestion of milk

Adult

3.8

Child

12.0

Total ingestion

Adult

4.0

Child

12.3

Source: USEPA, Technical Background Document for the Sewage Sludge Exposure and Hazard Screening Assessment, Document No. 822-B-03-001, Office of Water, U.S. Environmental Protection Agency, Washington, D.C., 2003.

Source: USEPA, Technical Background Document for the Sewage Sludge Exposure and Hazard Screening Assessment, Document No. 822-B-03-001, Office of Water, U.S. Environmental Protection Agency, Washington, D.C., 2003.

design manual for surface disposal of sewage sludge and domestic septage is available from the USEPA (1995a).

The basic feasibility of these natural sludge management options is totally dependent on the federal, state, and local regulations and guidelines that control both the sludge quality and the methodology. It is strongly recommended for all sludge management designs that the first step should be determining the possible sludge disposal/utilization options for the area under consideration. The engineer can then decide what has to be done to the sludge in the way of treatment and dewatering so it will be suitable for the available options. The most cost-effective combination of in-plant processes and final disposal options is not always obvious, so an iterative design procedure is required.

Australian practices and experiences with the die-off of pathogens in stored wastewater sludge, digested sludge, and sludge applied to land were reported by the Water Services Association of Australia (1995). Pathogens monitored were enteroviruses, Salmonella, and Giardia. Fecal coliforms and streptococci were also monitored. It was concluded that fecal coliforms and fecal streptococci did not adequately indicate the die-off of pathogens in anaerobic digestion, sludge storage, or soil amendment. It was found that storage of sludge for one year did not further reduce pathogen concentrations. The regrowth of Salmonella and fecal coliforms after a year of storage was the cause. Salmonella and coliforms also occurred in amended soils after rainfall at the end of summer, leading to the conclusion that further treatment would be required if food crops were to be grown.

Documents describing methods to assess biosolids risk and hazards screening are available (USEPA, 1995b, 2003b). Hazard quotients (HQs) for 40 pollutants were developed and the results are presented in Table 9.12, Table 9.13, and Table

TABLE 9.13

Hazard Quotient (HQ) Values >1 at the 95th Percentile of the HQ Distribution for Aquatic and Terrestrial Wildlife Via Direct-Contact Pathways3

TABLE 9.13

Hazard Quotient (HQ) Values >1 at the 95th Percentile of the HQ Distribution for Aquatic and Terrestrial Wildlife Via Direct-Contact Pathways3

CASRN

Chemical

Receptorb

HQ

67-64-1

Acetone

Sediment biota

356.2

120-12-7

Anthracene

Sediment biota

2.9

7440-39-3

Barium

Aquatic community

235.7

7440-41-7

Beryllium

Aquatic community

7.8

75-15-0

Carbon disulfide

Sediment biota

1.9

106-47-8

4-Chloroaniline

Aquatic invertebrates

1.3

333-41-5

Diazinon

Sediment biota

1.1

206-44-0

Fluoranthene

Aquatic community

10.7

Sediment biota

4.2

7439-96-5

Manganese

Aquatic community

13.9

78-93-3

Methyl ethyl ketone

Sediment biota

5.8

108-95-2

Phenol

Sediment biota

102.4

129-00-0

Pyrene

Aquatic community

41.9

Sediment biota

21.1

Soil biota

4.5

7440-22-4

Silver

Aquatic community

246.6

Aquatic invertebrates

28.2

Fish

4.8

a No pollutant resulted in an HQ > 1 for any wildlife species based on ingestion pathways.

b Sediment biota organisms include sediment invertebrates; aquatic community organisms include fish, aquatic invertebrates, aquatic plants, and amphibians; soil biota organisms include soil invertebrates.

Source: USEPA, Technical Background Document for the Sewage Sludge Exposure and Hazard Screening Assessment, Document No. 822-B-03-001, Office of Water, U.S. Environmental Protection Agency, Washington, D.C., 2003.

9.14. HQ values greater than 1 are considered to have failed the human health screen and the ecological screen.

Several attributes necessary to characterize and manage the potential risks for organic chemicals in biosolids are toxicity and dose response, transport potential, chemical structure, environmental stability, analytical capability in the matrix of interest, concentrations and persistence in waste streams, plant uptake, availability from surface application vs. incorporation, solubility factors, and environmental

TABLE 9.14

Human Hazard Quotient (HQ) Values >1 at the 95th Percentile of the HQ Distribution by Pathway for the Sewage Sludge Lagoon Scenario

TABLE 9.14

Human Hazard Quotient (HQ) Values >1 at the 95th Percentile of the HQ Distribution by Pathway for the Sewage Sludge Lagoon Scenario

CASRN

Chemical

Pathway

Receptor

HQ

7440-39-3

Barium

Drinking water from groundwater

Adult

1.5

Child

3.5

106-47-8

4-Chloroaniline

Drinking water from groundwater

Adult

2.7

Child

6.4

7439-96-5

Manganese

Drinking water from groundwater

Adult

32.3

Child

76.3

14797-65-0

Nitrite

Drinking water from groundwater

Adult

13.6

Child

33.8

14797-55-8

Nitrate

Drinking water from groundwater

Adult

9.2

Child

23.0

Source: USEPA, Technical Background Document for the Sewage Sludge Exposure and Hazard Screening Assessment, Document No. 822-B-03-001, Office of Water, U.S. Environmental Protection Agency, Washington, D.C., 2003.

Source: USEPA, Technical Background Document for the Sewage Sludge Exposure and Hazard Screening Assessment, Document No. 822-B-03-001, Office of Water, U.S. Environmental Protection Agency, Washington, D.C., 2003.

fate. Kester et al. (2004) present examples of deterministic and probabilistic models for quantitative risk assessment for polychlorinated biphenyls (PCBs) and dioxin, but they pointed out that, unfortunately, this information is available for only a small number of chemicals. As more information becomes available, better assessments of risk and management techniques will become available.

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    What is surface disposal biosolids?
    5 months ago

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