This paper is displayed with permission from David Wright of the Department of Environmental Protection, Bureau of Hazardous Materials & Solid Waste Control. A copy, or further information, may be obtained by contacting him at the Maine DEP: Telephone-207 287-2651; FAX 207 287-7826.

Regulating Agricultural Utilization of Solid Wastes in Maine

(October 7, 1996)

by David Wright, Sludge and Residuals Utilization Unit, Division of Solid Waste, BRWM, Maine Department of Environmental Protection

Introduction: As an alternative to costly solid waste disposal, the Maine Department of Environmental Protection (the Department) allows solid waste to be used, if the Department determines that the use will not pollute any water of the state, contaminate ambient air, constitute a hazard to health or welfare, or create a nuisance (38 M.R.S.A. 1310-N). This paper focuses in on how the Department regulates agricultural utilization of solid waste in the State. Utilization is "[t]he controlled land application of sludge or residuals at a rate commensurate with the nutritional needs of the crop to be grown and the assimilative capacity of the soil, usually requiring harvesting of the crop to compensate for the added nutrients. Some utilization programs may also have the improvement of soil conditions as a primary goal" (Chapter 567, 1994). Beneficial use, on the other hand, is the use of solid waste to substitute for a raw product in manufacturing, as fill, as a building material, or as a fuel. This summary does not cover beneficial use.

State Regulations: The Department oversees land application or composting of solid waste, such as food waste, wood ash, sewage sludge, paper mill sludge, or fish waste, under Department regulations Chapter 567, "Rules for Land Application of Sludge and Residuals." These rules establish a framework to characterize a residual's suitability for utilization on agricultural or forest lands, and establish siting and management criteria to protect public health and the environment.

The degree to which a residual is regulated varies with the potential human or environmental threat posed by the material. Generators must analyze a residual waste proposed for utilization to determine the residual's beneficial properties as well as contaminant content. Generators must obtain site specific licenses from the Department to utilize residuals that require special handling or when protection of public health and the environment depends on specific siting criteria. Utilization of more benign residuals is afforded through a blanket approval process or a permit-by-rule procedure.

Benefits: The potential benefits of a given solid waste will vary. Residuals such as sewage sludge and fish by-products are rich in nutrients, and are ideal replacements for mineral fertilizers. Farmers can substitute other residuals for agricultural lime, such as wood ash and lime-mud, to adjust soil pH for optimal plant growth. Others, such as primary paper mill sludge or wood wastes, can enhance a soil's moisture holding capacity and structure. By using these products, farmers and foresters can increase the health of their crops (e.g. Clapp, 1993), which may in turn reduce the need to apply pesticides or herbicides.

Pathogens: Sewage sludge and similar residuals contain pathogens, which are micro-organisms that can cause disease in humans, including bacteria, viruses, protozoa and helminths. The Department has not established risk based standards for pathogens due to their high variety in sewage sludge, the cost and uncertainty of identifying and quantifying viable pathogens, and the lack of risk assessment protocols for these organisms (Farrell, 1992). Rather, the Department uses technology-based standards for treatment of pathogens. An epidemiological study conducted in Ohio suggests that this approach of using process standards rather than establishing pathogen concentration standards to mitigate pathogenic risks is protective of human health (Hamparian, 1985).

At a minimum, the Department requires that residuals containing pathogens be treated by a process to significantly reduce pathogens (PSRP), which reduces pathogens by approximately 90%. Maine treatment plants achieve PSRP standards through lime stabilization, in which the facility mixes enough hydrated lime with the sludge to raise the pH to 12 and to keep it above pH 11.5 for at least 2 hours. Once a residual has undergone PSRP it may be land applied at a licensed site where pathogenic organisms are reduced to background concentrations by environmental factors such as ultraviolet radiation from the sun, desiccation, temperature changes, soil pH, competing soil microorganisms and organic matter (Farrell, 1992). In order to protect public health while this environmental destruction of pathogens takes place, Chapter 567 mandates waiting periods before a farmer can harvest crops or graze livestock on the land where PSRP residuals are utilized. The Department requires that a generator obtain a utilization permit prior to land application of a residual that is treated to a PSRP standard, in order to ensure that the sites are appropriately managed. As part of the federal regulation governing land application of sewage sludge (40 CFR part 503, 1995), EPA also promulgated similar types of management practices. In general, EPA's harvesting restrictions are more stringent than currently required under Department regulations Chapter 567.

Residuals containing pathogens, such as sewage sludge, can also be treated by a process to further reduce pathogens (PFRP). PFRP standards require concentrations of pathogens be reduced to ambient soil concentrations prior to application (Rubin, 1994). In the state of Maine, this is usually done through composting the residual. Chapter 567 defines Composting as "the biological decomposition and stabilization of organic matter under aerobic conditions and high temperature, resulting in a humus-like product that can be used as a soil amendment." Heat drying is another common PFRP process used on sludge from other states that is subsequently utilized in Maine. The Department licenses in-state compost facilities, but does not require a permit for utilization of compost, since harvesting restrictions are not required as they are for PSRP residuals, composting reduces odorous emissions, and nutrients are generally less available in composted materials verses lime stabilized materials. The Department requires in-state compost facilities to keep records of who they sell the compost to and its intended use. The Department currently does not license PFRP products used in Maine that are processed out-side of Maine to meet federal 40 CFR Part 503 sewage sludge standards, provided the residual meets State dioxin and metal concentration standards.

Nutrient Imbalances: Similar to manure, repeat applications of residuals that are not optimally balanced to the nutrient uptake by crops will result in soil nutrient imbalances. Left unchecked, repeat applications of residuals can lead to excessive loading of nitrogen, phosphorus and potassium; alter optimal soil pH; or alter optimal saturation of the soil's Cation Exchange Capacity (CEC) with calcium, potassium and magnesium. Chapter 567 requires that good farm practices be followed at utilization sites to prevent nutrient imbalances.

Groundwater contamination is a potential problem at utilization sites if nitrogenous residuals are mishandled. Nitrogen contamination in groundwater, reduced to nitrite by bacteria and ingested by humans, interferes with the blood's ability to transport oxygen to cells, particularly in infants (Hicks, 1993). Department regulations Chapter 567 protects ground water by requiring that nitrogenous residuals be applied at an agronomic rate, or the amount of residual necessary to supply the nitrogen needs of the crop. In this way the crop takes up the nitrogen before it passes through the root zone to groundwater. Further, the Department prohibits utilization of nitrogenous residuals on excessively drained soil, on soil with a depth to bedrock less than 20 inches, or within 300 feet of a water supply well.

Degradation of surface water quality is a concern when utilizing phosphorus containing residuals. Excessive phosphorus export to surface waters leads to eutrophication, since phosphorus is the limiting nutrient in most surface waters (Krebs, 1978). Phosphorus binds strongly to soil particles and is primarily transported to lakes from land application sites due to erosion of soil particles (MEDEP, 1992). The Department protects sensitive water bodies by prohibiting utilization of high phosphorus residuals on poorly drained soils, on land that slopes in excess of 15%, and when soil concentrations exceed 100 pounds of Phosphorus per acre. Additionally, land appliers must maintain buffers between utilization areas and surface waters, and must monitor soil annually for phosphorus content.

The Department protects crop productivity by requiring annual soil tests at licensed utilization sites to monitor the saturation of the CEC with calcium, potassium, and magnesium. The ratio of these essential cations must be balanced in soil for proper plant growth. The CEC is a measure of the soil's ability to hold onto essential cations, and prevent their loss from the system by leaching. The CEC varies with soil texture, organic matter content and pH. The optimal target levels of the essential cations in soil will vary depending on the crops being grown (Hoskins, undated). Many residuals increase the CEC of soil and thus increase the availability of cations for plant growth. However, residuals may over-saturate the CEC with a given cation, thus displacing other essential cations that leach from the system. When cation imbalances are detected, the Department prohibits further utilization of the residual until the CEC balance is restored through continued use of the field or addition of other nutrients. Generators of residuals are beginning to blend residuals to provide nutrients balanced to the crops need.

Heavy Metals: Some residuals, such as wood ash or sewage sludge, may contain heavy metals which in excessive amounts could be detrimental to human health, crop productivity, or wildlife. The Department requires that generators quantify metal levels in residuals and generally prohibits land application of residuals that exceed state standards. Sewage treatment facilities that do not meet Departmental concentration standards for sludge may require that industrial discharges pre-treat their effluent to remove contaminants that accumulate in a treatment plant's sludge. Wood ash generators can change the fuel mix to meet Departmental standards. Other residual generators can manipulate process controls or chemical inputs in order to meet residual concentration standards.

In addition to residual concentration standards, the Department has established maximum allowable cumulative soil concentrations of metals at utilization sites and requires that generators of sludge or other residuals monitor soil accumulation and plant uptake of metals at utilization sites. Cation saturation of the CEC or nutrient buildup in soil curtails utilization activities long before the site reaches cumulative metal limits, so that utilization of residuals has never been suspended due to metal loading. A review of the concentration of heavy metals in soil at the most heavily utilized sites in Maine (Houtman, 1995) indicates that soil and plant metal concentrations are still within typical agricultural soil (Pollock, 1995; Shacklette, 1984) and plant (ERG, 1992) background concentrations, and do not even approach risk based standards (ERG, 1992). In addition to residual quality standards, the same siting restrictions that protect surface and ground water from nutrient loading at utilization sites serves to protect these resources from potential heavy metal impacts.

The Department established metal standards in 1985 based upon EPA and FDA guidelines designed to protect human health and agricultural crops (Nault, 1984). In 1992, EPA concluded a re-evaluation of the risks posed by metals and select organic contaminants in land applied sewage sludge. This re-evaluation included a review of the scientific literature regarding the movement of contaminants from sewage sludge into the environment. In the study, EPA evaluated fourteen (14) pathways of exposure including direct ingestion of sludge by children, drinking water impacts, contamination by airborne dust, ingestion of plants or animals from sludge amendment sites, phytotoxic effects and impacts to animals (ERG, 1992). This risk assessment indicates that current State metal standards protect human health and the environment. The reader should note that the results of the risk assessment on sewage sludge are not necessarily applicable to other media, such as wood ash.

Dioxin: Dioxin and furans are a class of 205 halogenated aromatic hydrocarbons, which can have detrimental impacts on human health at very low concentrations (EPA, 1994). Several congeners of dioxin and furans have been detected in sludge from sewage treatment plants, and in some residuals from tanneries, textile mills, and paper mills (Mower, 1994). Dioxin forms when organic substances are heated in the presence of chlorine. Sources of environmental dioxin are from the use of herbicides containing 2,4,5-T; wood preservatives; incineration of bio-medical, hazardous and solid wastes; wood combustion in the presence of chlorine; transformer fires; and leaded gasoline use (ASTDR, 1989). It is unknown whether the presence of dioxin in sewage sludge originates from the sewage treatment system, industrial contributions, or from airborne deposits that subsequently enter the sewage treatment plant from storm sewers.

The Department requires that generators test sludge and residuals with the potential for containing dioxin prior to utilization. Dioxin and furan concentrations are expressed in 2378 TCDD equivalents, which is the summation of the dioxins' proportional toxicity to the most potent dioxin congener, 2,3,7,8 tetrachlorodibenzo-p-dioxin (2378 TCDD). The Department prohibits growing crops or animals for human consumption at sites where generators apply sludge or residuals with concentrations of dioxins above 27 ppt (parts per trillion) 2378 TCDD equivalents. Additionally, generators must locate and manage sites to minimize erosion of soil into waterways. There are no additional restrictions for utilization of residuals containing 27 ppt 2378 TCDD equivalents or less. The Department prohibits utilization of residuals containing greater than 250 ppt 2378 TCDD equivalents.

Currently all Maine sewage treatment plants landfill sludge that has concentrations above 27 ppt 2378 TCDD equivalents. Some paper mills continue to utilize dioxin containing sludge on forest land. Under an agreement with the Natural Resources Council of Maine, these mills limit application to a maximum of 18 dry-tons per acre, and only apply on a one time basis.

Other Hazardous Substances: Other organic hazardous substances have been detected from time to time in residuals generated in Maine. These hazardous substances are often divided into general categories based on the methods used to analyze for them, such as volatile compounds and acid/base-neutral compounds, or by specific chemical classes such as poly-chlorinated biphenyls (PCBs) or dioxins. Sludge or residuals generated in industrial settings have the potential to contain these hazardous substances and therefore the Department requires that generators test for these compounds before utilization. Examples of residuals found to contain these substances are sewage sludge with industrial inputs, paper mill sludge, and textile sludge.

When hazardous substances are detected in a residual, the Department screens the concentrations of contaminants against risk-based soil clean-up guidelines (e.g. EPA, 1994b; Smith, 1995). These guidelines are designed to protect a highly exposed individual ingesting either soil or groundwater contaminated by soil. The approach of screening residual concentrations against guidelines developed for soil errs on the side of protecting human health since the approach does not take into account the dilution, volatilization and degradation that will reduce contaminant concentrations at the utilization site (Overcash, 1981, Howard, 1991). However, in the majority of instances, the contaminant concentrations found in residuals are less than these conservative screening guidelines. In situations where residuals exceed these screening guidelines, site specific research into degradation processes or more sophisticated risk assessments are conducted to determine if the residual can be safely utilized, or if it must be landfilled (MEDEP, 1994).

Odors: Nitrogenous solid wastes can generate offensive odors at utilization sites. These odors can be strong for several days and may last two weeks, depending on the residual being utilized. Mixing of odorous materials with other residuals, such as wood ash, can alleviate odors. Site management practices, such as incorporation of the residual into the soil, set backs to residences, or waiting for favorable weather conditions can also mitigate odor impacts. Under Chapter 567, the Department can require that land appliers take steps to alleviate odorous emissions from utilization activities.

Groundwater monitoring: The Department designed the residual standards and siting requirements described above to, among other things, protect groundwater from impacts. Therefore, the Department does not require routine groundwater monitoring at utilization sites. The Department may require that the generator monitor groundwater at utilization sites when the generator seeks a variance to a groundwater protection standard in Chapter 567. Nitrogen is generally the parameter of concern monitored at a utilization site since it has a higher mobility in the environment than pathogens, metals, or other organic pollutants (Dowdy, 1993; Larson, 1993; ERG, 1992; NWWA, 1989). Even when the Department has granted a siting variance, performance monitoring indicates that residuals have rarely, if ever, impacted groundwater.

Economics: While solid waste by-products from industries may provide an agronomic benefit to farmers or foresters, improper utilization of these residuals can have deleterious effects on the environment as described above. Generators must remove residuals from treatment plants or factories on a regular basis or they interfere with the primary function of the facility, yet the residuals are only needed at the farm during limited windows of time dictated by crop production. Putrescible residuals may need to be composted or otherwise stabilized to allow for storage. Proper utilization requires that residuals be stored, transported and appropriately managed at the site of utilization, costing in the neighborhood of $15 to $30 a ton to land apply, and $20 to $60 a ton to compost. While agricultural utilization realizes a significant saving over landfilling, which ranges from $30 per ton at a private landfill to over $70 a ton at a commercial landfill, simply stacking residuals outside the generator's gate has significantly lower short-term costs than proper utilization or disposal, although the long-term costs of remediating environmental damage from improper disposal will be much greater than landfilling costs. The Department's regulation of residual utilization compensates for the short-term free market incentives to improperly handle these residuals and also decreases a generator's long-term cost that would otherwise stem from remediating contaminated sites.

Conclusion: Utilization is the land application of solid waste residuals to derive an agronomic benefit. Since 1985, Department regulations Chapter 567 has effectively protected human health and the environment from the risks posed by utilization while promoting the recycling of valuable resources back to the land and providing cost effective disposal options for generators. Specifically, the regulations require generators meet residual standards, apply at agronomic rates, and adhere to siting standards. These regulations need to be revised to incorporate experience gained from implementing the rule during the past decade, the latest scientific research, and legislative changes. Continued regulation of utilization is necessary to compensate for short-term free market incentives to improperly handle residuals, and to avoid increased long-term costs to generators from remediating contaminated sites.

References Cited:

ASTDR, June 1989, Toxicological Profiles for 2,3,7,8, Tetrachlorodibenzo-p-dioxin, ASTDR/TP-88/23.

Chapter 567, 06-096 Code of Maine Regulations, Rules for Land Application of Sludge and Residuals, last amended January 4, 1994).

Clapp, C.E., et. al., 1993, "Crop Yields, Nutrient Uptake, Soil and Water Quality During 20 Years on the Rosemont, Mn Sewage Sludge Watershed", in Sewage Sludge, Land Utilization and the Environment (Conference Proceedings, Soil Science Department and USDA-ARS, Univ. of Min., St. Paul, MN 55108) August 11-13.

Dowdy, R.H., C.E Clapp, D.R. Linden, W.E. Larson, T.R. Halbach, and R. C. Polta, 1993, "Twenty Years of Trace Metal Partitioning in the Rosemount, MN Watershed", in Sewage Sludge, Land Utilization and the Environment (Conference Proceedings, Soil Science Department and USDA-ARS, Univ. of Min., St. Paul, MN 55108) August 11-13.

ERG, Eastern Research Group, 1992, Technical Support Document for Land Application of Sewage Sludge, Vol I & II (Prepared for USEPA, 401 M Street S.W., Washington D.C., document number PB93-1105757).

EPA, 1994, Estimating Exposure to Dioxin-Like Compounds, Volume II: Properties, Sources, Occurrence and Background Exposures (External review draft, EPA/600/6-8/005Cb) June.

EPA, 1994b, Soil Screening Guidance, (External review draft, EPA/540/R-94/101, PB95-963529) Dec.

Farrell, Joseph B., 1992, Technical support Document for Reduction of Pathogens and Vector Attraction in Sewage Sludge (Edited by Jan Connery of Eastern Research Group, for USEPA, 401 M Street S.W., Washington D.C., document number PB93-110609)

40 CFR Part 503, Standards for the Use and Disposal of Sewage Sludge, last revised October 25, 1995.

Hamparian, Vincent V., et. al., 1985, "Sludge Disposal on Farm Land: An Epidemiologic Evaluation of the Risk of Infection" in Demonstration of Acceptable Systems for Land Disposal of Sewage Sludge, by Robert E. Brown, Ohio Farm Bureau and USEPA (USEPA Document No. EPA/600/2-85/06) August.

Hicks, LaBelle, 1993, Maine Dept. of Agriculture, "Human Health Effects of Nitrogen in the Environment" in conference proceedings for Nitrogen in the Environment (University of Maine, Water Resources Program, 5715 Coburn Hall, Orono, Maine 04469-5715), Oct. 10

Hoskins, Bruce, (undated), "Interpreting Soil Test Results for Commercial Crops" (Maine Soil Testing Service, 25 Deering Hall, University of Maine, Orono, Maine 04469)

Houtman, Nicolas R., Larry M. Zibilske, David Power, (1995), Survey of Soil Chemistry Data at Sludge Application Sites in Maine, (Maine Sludge and Residuals Utilization Research Foundation, Research Report No. 4, University of Maine at Orono, ME)

Howard, Philip H., et. al., 1991, Handbook of Environmental Degradation Rates, (Lewis Publishers, Chelsea, Michigan).

Krebs, Charles J., 1978, Ecology: The Experimental Analysis of Distribution and Abundance, (Second Edition, Harper & Row Pub., New York, NY)

Larson, W.E. August 11, 1993, "Case Study - Rosemont, Minnesota Watershed" in Conference Proceedings from Sewage Sludge: Land Utilization and the Environment (Soil Science Department and USDA-ARS, University of Minnesota, St. Paul, MN 55108).

MEDEP and MEDHS, 1994, Guidance Manual for Human Health Risk Assessments at Hazardous Substance Sites, (BRWM, MEDEP, 17 Station, Augusta, ME), June

MEDEP, April, 1992, "Best Management Practices to Control Nonpoint Source Pollution, a Guide for Town Officials" (BL&WQC, MEDEP, Station 17, Augusta ME, 04333-0017).

Mower, Barry, March 1994, 1993 State of Maine Dioxin Monitoring Program, (BL&WQC, Maine MEDEP, 17 Station, Augusta, ME).

MWCA, Maine Waste Water Control Association, March 19, 1986, "Potential Health Effects from Dioxin Containing Sludge", (BRWM, MEDEP, 17 Station, Augusta, ME).

Nault, Gary, August 22, 1984, memo to Board of Environmental Protection, "Written Statement Explaining How DEP Handled Comments Concerning Rule 567, Rules for Land Application of Sludge and Residuals" (BRWM, MEDEP, 17 Station, Augusta, ME).

NWWA, 1989, Introduction to Ground Water Geochemistry (Course proceedings: National Water well Association, Dublin, OH) Oct.

Overcash, Michael R. (Ed.), 1981, Decomposition of toxic and Nontoxic Organic Compounds in Soils, (Ann Arbor Science Publishers, Inc., Ann Arbor, MI).

Pollock, James (1995), Background Metal Concentration on Agricultural Soils in Maine, prior to residual utilization (BRWM, MEDEP, 17 Station, Augusta, ME)

Rubin. Alan B., Water Environment Federation, Memo to Interested Parties, RE: Pathogens in Sewage Sludge, October 13, 1994.

Shacklette, Hansford T. and Josephine G. Boerngen (1984), Element Concentrations in Soils and Other Surficial Materials of the Conterminous United States (USGS Professional Paper 1270, US government printing office, Washington, D.C.)

Smith, Roy, 1995, EPA Region III Risk Based Concentration Table, (USEPA Region III, Philadelphia, PA).

Sproul, Bryce, Sept. 17, 1986, Memo to Board of Environmental Protection "Written Statement explaining the factual and policy basis for the amendment to Chapter 567, Part D", (BRWM, Maine MEDEP, 17 Station, Augusta, ME)