3.13 Biosolids Land Application, Part 503 & Virginia Permitting

Biosolids Land Application, Part 503 & Virginia Permitting

The ABC Wastewater outline lists "solids disposal: land application, landfill" as a treatment process task and places regulatory compliance and reporting in the Security, Safety, and Administrative Procedures area. In Virginia, biosolids land application is also politically visible, which means the operator's records will be read by people other than regulators.

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1. The Three Independent Part 503 Requirements

Biosolids applied to land must simultaneously satisfy all three of the following. Failing any one disqualifies the material.

1. Pollutant limits (metals concentrations and loadings)
2. Pathogen reduction (Class A or Class B)
3. Vector attraction reduction (one of 10 listed options)

They are not alternatives, and a candidate who treats them as a single test will miss the question.

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2. Pollutant Limits (40 CFR 503.13)

Part 503 regulates nine metals with four different limit tables.

How the tables interact:

• Ceiling concentration limits are absolute. Exceed any one and the material cannot be land applied at all, regardless of anything else.
• If a batch meets the pollutant concentration (Table 3) limits, it is "exceptional quality" with respect to metals, and cumulative loading tracking is not required.
• If it meets ceilings but not Table 3, it may still be applied, but the applier must track cumulative loading on each site against the Table 2 limits and observe the Table 4 annual limits.

"Exceptional quality" (EQ) biosolids meet the Table 3 pollutant concentrations and Class A pathogen reduction and one of the vector attraction options 1 through 8. EQ material can be bagged and sold to the public with essentially no general requirements or site restrictions.

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3. Pathogen Reduction

Class A

• Fecal coliform below 1,000 MPN per gram of total solids (dry weight), or Salmonella below 3 MPN per 4 grams of total solids, measured at the time of use or disposal.
• Plus one of six alternatives (time-and-temperature, alkaline treatment with pH and temperature and drying conditions, prior/no prior testing for enteric virus and helminth ova, a Process to Further Reduce Pathogens (PFRP), or an equivalent process approved by the permitting authority).
• Listed PFRPs: composting, heat drying, heat treatment, thermophilic aerobic digestion, beta ray irradiation, gamma ray irradiation, and pasteurization.
• Class A material carries no site restrictions.

Class B

• Meet one of three alternatives: (1) a geometric mean of seven samples below 2,000,000 MPN or CFU fecal coliform per gram of total solids dry weight; (2) use of a Process to Significantly Reduce Pathogens (PSRP); or (3) an equivalent process.
• Listed PSRPs: aerobic digestion, anaerobic digestion, air drying, composting, and lime stabilization.
• Class B material must be applied with site restrictions (below).

Class B site restrictions (40 CFR 503.32(b)(5))

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4. Vector Attraction Reduction (40 CFR 503.33)

Ten options; the ones an operator is most likely to be using:

1. 38 percent volatile solids reduction across the treatment process.
2. Anaerobic bench test - additional anaerobic digestion of a sample for 40 days at 30 to 37 degrees C yields less than 17 percent additional VS reduction.
3. Aerobic bench test - additional aerobic digestion for 30 days at 20 degrees C yields less than 15 percent additional VS reduction.
4. Specific oxygen uptake rate (SOUR) at or below 1.5 mg O2 per gram of total solids per hour at 20 degrees C (aerobically digested only).
5. Aerobic treatment 14 days or longer at above 40 degrees C with an average above 45 degrees C (composting).
6. Alkali addition to pH 12 for 2 hours and pH 11.5 for an additional 22 hours without adding more alkali.
7. Drying to at least 75 percent solids with no unstabilized solids.
8. Drying to at least 90 percent solids where unstabilized solids are present.
9. Injection below the surface with no significant amount on the surface within one hour.
10. Incorporation into the soil within 8 hours of application. For Class A material, the sludge must additionally be applied to the land within 8 hours after being discharged from the pathogen reduction process.

Note that options 9 and 10 are management practices at the field, not treatment at the plant, and they are the two most commonly relied upon by Class B land application programs.

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5. Agronomic Rate - Nitrogen Usually Controls

The agronomic rate is the biosolids application rate that supplies the plant available nitrogen (PAN) the crop needs and no more, so that nitrogen does not leach to groundwater.

Application rate (dry tons/acre) = Crop N requirement (lb/acre) / PAN (lb N per dry ton)

PAN is computed from the biosolids analysis:

PAN = (Kmin x Organic N) + (Kvol x NH4-N) + NO3-N

• Kmin is the first-year mineralization rate of organic nitrogen - typically 0.20 for anaerobically digested, 0.30 for aerobically digested, 0.10 for composted.
• Kvol accounts for ammonia volatilization loss - typically 0.5 for surface application, 1.0 for injected or immediately incorporated material.

Worked example

Biosolids contain 38,000 mg/kg organic N, 6,000 mg/kg ammonium N, and negligible nitrate. They are anaerobically digested (Kmin 0.20) and surface applied (Kvol 0.5). The crop needs 130 lb N per acre.

1. Convert mg/kg to lb per dry ton: multiply by 0.002. Organic N = 38,000 x 0.002 = 76 lb/dry ton. Ammonium N = 6,000 x 0.002 = 12 lb/dry ton.
2. PAN = (0.20 x 76) + (0.5 x 12) = 15.2 + 6.0 = 21.2 lb PAN per dry ton
3. Rate = 130 / 21.2 = 6.1 dry tons per acre

Why nitrogen controls. At 6.1 dry tons per acre, the cumulative metals loading is a small fraction of the Part 503 limits - typically a few percent per application. A site would need decades of repeated application to approach a cumulative metals limit, whereas nitrogen constrains every single event. That is why "agronomic rate" and "nitrogen-based rate" are treated as synonyms in practice, except where a state imposes a phosphorus-based rate on high-phosphorus soils.

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6. Virginia's Additional Requirements

Federal Part 503 sets the floor. Virginia adds requirements through DEQ under the Virginia Pollution Abatement (VPA) permit regulation, 9VAC25-32, which contains the state's biosolids use standards.

Practical obligations layered on top of Part 503:

• Permits. Land application requires a VPA permit or coverage under the general permit for biosolids management, held by the generator or the land applier. Individual field sites are approved and mapped.
• Nutrient management plan. Prepared by a certified nutrient management planner for each site, setting the application rate on nitrogen and, on high-phosphorus soils, on phosphorus.
• Setbacks and buffers from occupied dwellings, property lines, wells, surface waters, and roads, with distances that vary by application method - injected material gets smaller setbacks than surface-applied.
• Notification. Advance notice to the local governing body and, in many cases, posted signage before application begins. This is a Virginia-specific requirement that has real enforcement consequences.
• Local monitoring. Virginia localities may adopt an ordinance to monitor land application and may charge a fee; local monitors have authority to observe operations and report violations to DEQ.
• Certified land applier requirements and operator record retention.
• Recordkeeping and annual reporting covering quantities, sites, analytical results, pathogen and vector attraction certifications, and cumulative loading where applicable.

What the operator actually does. Sample and analyze each batch for the nine metals, nutrients, percent solids, and pathogen indicator; verify and document the vector attraction option used; certify pathogen class; give the hauler and applier the analysis; and retain records - Part 503 requires five years for most records and indefinitely for cumulative loading records at sites receiving non-EQ material.