National Academy of Sciences. Biosolids Applied to Land:
Advancing Standards and Practices

Chapter 2:  Biosolids Management [abridged]

Wastewater treatment necessarily produces two end products: effluent and sewage sludge. All wastewater generated in homes, businesses, industries, and other venues that is conveyed to wastewater treatment plants is treated to allow effluent discharge back into the surface and groundwaters of the United States. Sewage sludge is likewise treated in the wastewater process, generally through aerobic or anaerobic microbial activity for specified time periods and temperatures. Both effluent and sewage sludge require treatment to ensure that their release into the environment is protective of human health and the environment as required by the Clean Water Act (CWA). Sewage sludge is defined as the solid, semi-solid, or liquid residue generated during the treatment of domestic sewage in a treatment works, and biosolids are defined in this report as sewage sludge that has been treated to meet standards for land application under Part 503 of the CWA or any other equivalent land-application standards.

Of the nation's estimated 263 million people in 1996, 190 million of them or 72% contributed wastewater directly through a sewerage system to approximately 16,000 publicly owned treatment works (POTW) (EPA 2000a). The remaining 73 million people discharged wastewater to some form of on-site treatment system or holding tank, more than half of which also is ultimately discharged to a POTW (Razvi 2000). Each person discharging human waste to a wastewater treatment system produces approximately 47 dry pounds (21 kilograms) of sewage sludge each year (EPA 1993). As the population of the United States increases, the percentage of the population directly discharging to POTWs is projected to increase to 88% by 2016 (EPA 2000a). The ability to effectively treat and return wastewater and sewage sludge to the environment in a protective manner is of paramount importance from both a public-health and an environmental perspective. In partial recognition of this fact, Congress passed the CWA of 1972 and the federal government has contributed $61.1 billion in grants and $16.1 billion in low-interest loans to municipal and local governments between 1972 and 1999 for capital construction costs to provide necessary support for wastewater and sewage-sludge treatment and disposition of biosolids (EPA 2000a). Approximately 40% of that amount has been used for sewage sludge treatment and disposition of biosolids (Peavy et al. 1985). Sewage sludge is generated in several treatment processes that generally include primary (from primary clarification) and secondary (from secondary clarification) sewage sludge. The general process of treating wastewater and sewage sludge is illustrated in Figures 2–1 and 2–2.

EPA is responsible under Section 405 of the CWA to promulgate regulations for sewage sludge use or disposal. The CWA Amendments of 1987 added special provisions that required EPA to identify toxic pollutants and set sewage-sludge standards that are "adequate to protect public health and the environment from any reasonably anticipated adverse effect of each pollutant" (emphasis added). Recognizing that sewage-sludge production will continue to increase and that sewage sludge possesses many potential beneficial properties for agricultural production, federal and state agencies have long advocated the recycling of it as biosolids through land application (EPA 1981, 1984, 1991). The other primary options for sewage sludge disposition are to bury it in a landfill or to incinerate it. Although these latter options possess inherent risks and environmental difficulties, these options are beyond the scope of this report (see Chapter 1).

Of the 16,000 POTWs in the United States, approximately 8,650 generate sewage sludge that must be used or disposed of at least annually (Wisconsin Department of Natural Resources, unpublished data, 2001). Based on data from 37 states, approximately 5,900 of these sewage sludge generators (68%) either land apply or publicly distribute over 3.4 million dry tons of biosolids each year (see also End Use Practice section of this chapter). Most of this recycling use is conducted without public opposition and with no documented adverse health effects. However, recent allegations of adverse health effects have received media and congressional attention. Chapter 3 assesses the epidemiological evidence and approach for health effects associated with biosolids production and application, but does not systematically investigate these allegations. Rather, the report examines the process by which the regulations were established and determines whether advances in risk-assessment methods warrant a revisiting of the process.

This chapter briefly examines the development of the Part 503 rule, certain related issues, and what EPA has done to implement the rule since promulgation. It also reviews how states implement the rule, whether or not they have explicit delegated authority from EPA. An examination of biosolids regulations and practices in Europe is then used to compare and contrast these practices. An overview of the acceptable pathogen treatment controls and land application site restrictions, is presented, as well as associated methods for stabilization to reduce the attraction to vectors, such as rodents. Issues are raised that relate to the verification of the efficacy of treatment. Finally, this chapter examines end-use practices in the United States, biosolids quality achieved, data on nonregulated pollutants, risk-management practices inherent to land application of biosolids (primarily Class B) and to the risk-assessment process, and compliance and enforcement strategies and action taken by EPA or states.

NOTE: THE BULK OF CHAPTER 2's MATERIAL IS NOT INCLUDED, JUST THE FOLLOWING FINDINGS AND RECOMMENDATIONS

FINDINGS AND RECOMMENDATIONS

EPA provides insufficient support and oversight to the biosolids program. EPA gives low priority to its biosolids program, because it contends that risks from exposure to chemicals and pathogens in biosolids are low and that land-application programs generally function as intended and in compliance with the regulations. This contention should be better substantiated.

Recommendations

* EPA should strengthen its biosolids-oversight program by increasing the amount of funding and staff (technical and administrative) devoted to it.

* EPA should provide additional funds (not diverted funds) to states to implement biosolids programs and facilitate delegation of authority to states to administer the federal biosolids regulations.

* Resources are also needed for conducting research into emerging issues and to revise the regulations as appropriate and in a timely fashion (e.g., molybdenum standards should be proposed).

* A process should be established to track allegations and sentinel events (compliance, management, or health based), investigations, and conclusions. Such tracking should be systematic, developed in cooperation with states, and should document both positive and negative outcomes.

The Pathogen Equivalency Committee (PEC) performs invaluable technical support and process assessment.

Recommendations

* The PEC should be funded, supported, and officially sanctioned as an integral part of the federal biosolids program. The following are important in supporting the PEC:

* The PEC members should have a formal portion of their time allocated to PEC responsibilities.

* Travel funds should be put at the disposal of the PEC to enable meeting attendance and visits to selected sites of petitioners.

* There is a perception on the part of PEC members that EPA's Cincinnati laboratories do not include biosolids as a formal part of their mission statement. This needs to be clarified and rectified.

* formal procedure for designation of backup members should be devised.

Biosolids risk-management practices are an integral component of the risk assessment and technological criteria that were used to establish the standards of the Part 503 rule. They are therefore an important component of the regulations for chemicals and pathogens.

Recommendations

* Studies should be conducted to determine whether the management practices specified in the Part 503 rule (e.g., 10-meter setback from waters) achieve their intended effect.

* Additional risk-management practices should be considered in future revisions to the Part 503 rule, including setbacks from residences or businesses, setbacks from private and public water-supply wells, slope restrictions, soil permeability and depth to groundwater or bedrock, and reexamination of whether a greater setback distance to surface water is warranted.

* Provisions for allowing distribution of Class A biosolids in bags or other containers (weighing less than 1 metric ton) should not be allowed when they do not meet pollutant concentration limits (i.e., all biosolids sold or given away should be EQ).

* Exemptions from nutrient management and site restrictions for land application of bulk EQ biosolids should be eliminated.

There are several prescribed treatment processes that can be used to meet regulatory requirements for classifying biosolids as Class A or Class B. However, the efficacy of the treatment processes needs verification, and the stabilization regulations need to be refined for consistent control of vector attraction.

Recommendations

* EPA should conduct national field and laboratory surveys to verify that Class A and Class B treatment processes perform as assumed by their engineering and design principles. Determinations should be made of pathogen density and elimination across the various accepted treatment processes and in the biosolids or environmental media over time.

* Standard treatment design criteria should be adopted nationally to ensure compliance with existing biosolids regulations.

* Stabilization controls need to be further refined and directly correlated to metabolic techniques (e.g., SOUR test, carbon dioxide metabolic release, methane metabolic release).

The available methods for detecting and quantifying pathogens in biosolids have not been validated. There have been a number of advances in detection and quantification of pathogens in the environment and in approaches to environmental sample collection and processing. However, no consensus standards have been developed for pathogen measurements in biosolids.

Recommendation

EPA should support development, standardization, and validation of detection and quantification methods for pathogens and indicator organisms regulated under the Part 503 rule. The sufficiency of these methods and their results should be considered in conducting and interpreting future risk assessments and used to develop applicable risk-management technologies.

The CWA requires EPA to establish biosolids regulations based on risk; however, it is important to acknowledge and consider other approaches to regulating land application of biosolids.

Recommendation

As part of the process of revising the Part 503 rule, EPA should review biosolids protocols used by other nations. This could provide valuable new perspectives and insights into the scientific, technical, and societal bases for the development and implementation of biosolids regulations.

EPA and the U.S. Department of Agriculture cosponsored a workshop on emerging pathogens in June 2001 with international experts in the field. The committee supports the major research recommendations from that workshop (listed below).

Recommendations

Research is needed on the following topics:

* Pathogen survival in processing or emissions during the treatment process.
* Vectors carrying pathogens and toxins.

* Bioaerosols and other chemical aerosols.

* Test-method development and validation for various organisms in sewage sludge and biosolids.

* Field verification of efficacy of Class A and Class B treatment processes (including data to directly relate process controls to initial and final pathogen and indicator densities).

* Development of indicator pathogens for assessment of impact and attenuation in field situations.