Virginia regulations provide for submission and approval of a sludge management plan for a permitted treatment works, that addresses sludge management issues including treatment and final disposition of residuals. Final disposition of treated sewage sludge may involve use or disposal. Use of treated sewage sludge as biosolids requires that the level of treatment meet or exceed a defined level of pathogen control and vector attraction reduction. In addition, the biosolids must be tested for various regulated constituents and if the measured level of a constituent exceeds the standards, the use of the tested biosolids would be restricted.
For the purpose of the State Biosolids Use Regulations (12 VAC 5-585), "use" includes resource recovery, recycling or deriving beneficial use from the material. "Disposal" involves the final disposition of a waste material without resource recovery, recycling or deriving beneficial use from the material. All practical use options should be evaluated before disposal options are evaluated or selected. Sludge use practices include land application, for agricultural, nonagricultural and silvicultural purposes and the distribution and marketing of acceptable sludge products. Sludge disposal methods typically include incineration, landfill burial and other dedicated disposal practices, such as storage on dedicated sites (surface disposal). Water quality protection and monitoring requirements must be included in all sludge management plans, except for those land application use practices designed for limited loadings (amounts per area per time period) within defined field areas such as specified for agricultural use.
Sludge treatment processes are primarily designed to increase the solids content of the sludge by separation and removal of liquid and are designed to stabilize the solid fraction through biochemical conversions that inactivate pathogens and reduce vector attraction characteristics and the potential for odor production. Such treatment should be designed to improve the characteristics of the sludge for a particular use/disposal management practice, increase the economic viability of a particular management practice and reduce the potential for public health, environmental and nuisance problems.
The new federal standards, promulgated by USEPA as 40 CFR Part 503 Regulations, include numerical standards for sludge quality as established by environmental health risk assessments for exposure to regulated constituents that might occur during various management options and receptor exposure pathways. The Virginia Regulations contain similar requirements but also provide for site specific management controls such that the sludge contaminants will not exceed human health and environmental criterion established for the relevant exposure pathways. All land application field management controls must be adequately addressed in the approved operational plan and may include:
1.) Operational methods.
2.) Application rate controls.
3.) Access restrictions.
4.) Buffer restrictions.
5.) Crop rotations and use restrictions.
Sewage sludges will concentrate all of the various trace elements detected in raw sewage, but only a few contaminants are found at levels sufficient to pose concerns based on risk assessments. These regulated trace substances must be monitored on a regular basis and compared to the standards established for the selected management option. Maximum contaminant levels have been developed for each regulated contaminant for a particular use or disposal option. To be used sludge must be treated to reduce the microorganism content to a safe level using established treatment methods.
The federal and State Regulations address two treatment classifications to achieve pathogen control as required to protect public health when treated sludge is used as biosolids:
1.) Class A: Processes for further reduction of pathogens (PFRP).
2.) Class B: Processes for significant reduction of pathogens (PSRP).
Sludge management through land based use options requires that both Class B pathogen control and an approved means of vector attraction reduction, be attained as a minimum. Sludge so stabilized and of proper quality is defined as biosolids and is suitable for agricultural use. The Class B biosolids land applied in Virginia typically contain levels of the indicator microorganisms that are are 100 to 1000 fold below the maximum allowable Class B Standard. In addition, the typical levels of regulated constituents that are measured in land applied biosolids are one fourth to one tenth of the maximum standards allowed. Class A treated biosolids such as compost may be distributed and marketed for public use, although directions for proper use of such products is to be provided to the end users. The Biosolids Use Regulations (12 VAC 5-585) contain site specific requirements or management practices for land application, or marketing, or distribution of biosolids by contractors hired by the treatment works owners. Conventional biosolids production methods include digestion and alkaline stabilization. Non-conventional treatment of biosolids may require microbiological testing to verify the treatment classification.
The primary agronomic value of biosolids is the nutrient and organic content which must be established prior to agricultural use. Nitrogen and phosphorous concentrations typically found in biosolids can support crop growth. However, nitrate is mobile in soil and can accumulate in groundwater as a pollutant. Thus, the amount of biosolids applied to land is usually restricted to the nitrogen requirements of the crop grown on the amended site immediately following application (agronomic rate). Nutrient management plans may be required for certain sites based on the application frequency and use of other fertilizers. In addition, soil erosion and site runoff from wet fine textured soils may result in nutrient pollution of surface waters if surface application of biosolids is not controlled. The results of approved monitoring programs (soil and water) may be utilized to verify annual or frequent application rates (the agronomic rate is applied more than one time in three (3) year period). The phosphorus content of certain soils may also affect nutrient management restrictions.
Regulated agricultural utilization of biosolids done in compliance with the Biosolids Use Regulations (12 VAC 5-585), is a viable, safe and effective method of sludge management. Public opposition to land application projects normally stems from aesthetic concerns and sociopolitical issues, but implementation of such projects are often criticized due to technical weaknesses, including absence of constant surveillance of the transportation and the application of biosolids to field areas. All concentrated waste management use or disposal systems located in Virginia are required to operate under site specific permits. Approved sludge management plans have been made a condition of approval for certificates to operate such facilities. The recently adopted amendments to the Biosolids Use Regulations provide for the collection of fees from land appliers and use of those fees to reimburse local governments for costs related to the monitoring and testing activities of assigned local biosolids monitors and coordinators. Local Monitors can help ensure that land application operations are being conducted in compliance with the Biosolids Use Regulations. The VDH requires that health protection is addressed in biosolids management plans and assures that public meetings are arranged to discuss technical issues, as required by the State Health Code 32.1-164.2 and 164.5 prior to issuing permits to land application contractors. However, recurring odor problems, the Not-In-My-Backyard Syndrome (NIMBY), together with political jurisdictional disputes, can overwhelm the technical issues and delay or prevent issuance of permits. Thus, many municipalities are considering disposal options such as incineration in order to maintain their direct control over sludge management. However, incineration releases certain pollutants to the outside air and health risk assessment data clearly reveals that air pollution is a much more serious health concern than is the permitted land application of biosolids.
As a result of the public opposition to persistent odors and uncertainties of agricultural use of biosolids, many treatment work owners are now planning to utilize sludge treatment technology designed to provide Class A biosolids for distribution and marketing. Class A treatment processes include various combinations of the following technologies:
1.) High Temperature Digestion and/or Composting.
2.) Alkaline Stabilization (combinations of heat and alkali).
3.) Pasteurization (heat and pressure).
4.) Thermal (high temperature with either pressure drying or desiccation).
Such additional treatment is significantly more expensive in comparison with Class B treatment processes, but can produce a relatively unobjectionable material that can be safely used as a soil conditioner.
Recycling initiatives have also encouraged the use of dried sludge and incinerator ash as additives in material products such as aggregate for the manufacture of: bricks, building blocks, structural elements for prevention of soil and beach erosion and flowable fill for soil stabilization and backfill.