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SECTION V: AN ASSESSMENT OF MAINE'S REGULATION OF BIOSOLIDS

5.1 Introduction
5.2 Agronomic Value
5.3 Soil Quality
5.4 Water Quality
5.5 Air Quality
5.6 Sustainability
5.7 Management

5.1 Introduction
In this assessment of how well Maine’s regulations work to protect the public health and environment, five topics have been addressed:

1. Soil fertility amendment;
2. Soil quality and human risks via soil;
3. Water quality and associated risks;
4. Air quality changes due to odors and bioaerosols; and,
5. Sustainability (long-term effects).

First and foremost, biosolids are regulated and managed for their agronomic value. Using these residuals for fertilizer dates back to the earliest municipal sewerage systems, prior to waste water treatment and well before the current biosolids standards. The regulations are designed to protect soil quality, and ultimately human exposure pathways, by limiting the addition of certain metals or organic compounds to soil. Interactions of biosolids with water are the third topic and this covers impact to water quality, as well as the ability of water to transport components away from the site of utilization. Air is the focus of the fourth topic with particular emphasis on odor and bioaerosols. Finally, the topics of sustainability and the management of biosolids are addressed. The regulations address some of the issues associated with the short and long-term objectives for biosolids utilization.

A basic question asked is, ‘Do the regulations work?’ The simple answer is yes. The validity of a yes answer is substantiated by the numerous land application sites and programs approved for biosolids that meet Maine’s standards. Underlying these approvals are full characterizations of the biosolids, site monitoring, an open review of permits, and compliance with the applicable utilization standards. Site managers and regulators can attest to the hundreds of hours of meetings with town officials and concerned citizens needed to maintain a land-spreading program. Regulatory compliance has been carefully monitored and managed with due diligence, albeit with a currently small staff.

Another basic question is, ‘Do the regulations go far enough to protect the public?’ Again, in many areas the basic answer is yes. The regulatory agency can change regulations in response to advances in knowledge; rarely does this occur quickly. There is a continued need to improve the public dialogue about biosolids and to build a true consensus (Beecher et al., 2005). In part this is because some regulations are set-pieces that are established by legislation, while other aspects may be classified as best-management practices that are evolutionary concepts. Another criticism, one that illustrates differences in the philosophy of reusing waste products, is that the rules do not necessarily support sustainable practices. For example, metal loadings are based on either a maximum concentrations for a single application, or cumulative loading at the ceiling concentration over a period of 20 years. A longer time period, of decades to centuries, is needed for sustainability. Although the rules protect the environment with a reasonable safety factor, the need to utilize biosolids will exceed a 20 year window. This is a logical consequence of our civilization continuing to make wastewater and biosolids for much longer than 20 years.

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5.2 Agronomic Value
As mentioned in the introductory chapter, biosolids must be used for a defined agronomic benefit (Chapter 419, Section 4(B)). This benefit comes from the addition of plant nutrients, such as nitrogen or phosphorous, and depending on the type of processing, a liming benefit. The amount of biosolids utilized at a land-spreading site must be calculated based upon soil testing, biosolids composition, and crop requirements. This is a very important concept, because biosolids contain several major plant nutrients and utilization must not exceed any crop need so that the soil chemistry remains balanced. Since Class B biosolids are land-applied, attention is paid to the nitrogen loading and cumulative phosphorous additions.

Nutrient loading calculations include the carry-over of nitrogen from year to year as organic nitrogen is mineralized into a plant available form (Chapter 419, Appendix A). A sample calculation for a typical Maine biosolids (Class B) is shown in Table VII. In this table, nitrogen loading is calculated for three consecutive years. Notice that there is some small variability in the solids content and total kjeldahl nitrogen content of the biosolids. The crop nutrient requirement is constant (e.g. single crop of hay). The biosolids loading rate is in metric tons per hectare and has been calculated using a conservative loading assumed to be 75 per cent of the target value to avoid excess nitrogen addition. The loading of organic nitrogen is greater than the crop requirement because all of the nitrogen is not plant-available. The organic nitrogen is mineralized over several years and causes a nutrient carry-over that must be tracked; this is the added N-mineralization factor. The net added plant-available nitrogen is slightly less than the crop need and nitrogen loss should be minimized.

TABLE VII. Nitrogen Loading of Biosolids, Sample Calculations

Biosolids also contain the essential plant nutrient phosphorous. Certain additional restrictions apply to the land applications within the direct watersheds of sensitive water bodies. If the biosolids contain more than plant requirements, additional controls on timing, suitable slopes, and setbacks are employed. Using the same example Class B biosolids, phosphorous provides 72 kilograms total-P in year one, 73 kilograms total-P in year two, and 68 kilograms total-P in year three. The annual plant requirement for phosphorous is 22 kilograms per hectare and loading will exceed plant requirements. Presumably the excess phosphorous will remain with the soil. Loading may continue until plant-available phosphorous concentrations exceed 100 pounds per acre (112 kg/ha). Based on our example, site utilization would have to cease after a few years until the stored phosphorous is used up by the crops.

Based upon the example worked here, the Maine rules for the land application of biosolids provide sufficient guidance for agronomic uses. Specific application rates will be determined by the type of crop grown and farmers need to have a nutrient management plan.

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5.3 Soil Quality
The greatest benefits derived from applying biosolids to land are an increase in soil fertility (Section 5.2) and an improvement in soil properties caused by the addition of organic matter that lowers soil density and increases moisture retention capacity. These benefits accrue outside of any regulatory constraint. Biosolids also contain trace metals that may also be plant nutrients, possibly some pathogens in Class B, and possibly some trace organic compounds of concern. The environmental fates of these components of biosolids vary by source and local conditions. Some may move into soil and water, but most tend to reside in the soil. In addition, even though some of these compounds may be present, they are not in an available form because the stability of biosolids retards the release of bound metals or organic compounds (Switzenbaum et al., 1997). The regulations do address biosolids stability during processing, but in a different rule chapters (06-096 CMR Chapters 405 and 409). The regulatory approach has been to set standards that protect the public from likely worst-case situations based upon the state and federal risk assessments.

Metal accumulation in soil is controlled by restricting metal content in biosolids that are land-applied along with a cumulative upper loading limit. Exceptions may occur for metal concentrations exceeding the limit for single application, but not for the cumulative loading. The loadings are consistent with available research on the transfer of metals from soils to plants. A second layer of protection is offered by grazing restrictions. These restrictions control the transfer of metals from the soil to animals via direct ingestion. In terms of the cumulative metal loading limits, the Maine rules are conservative. Cumulative metal loading limits were estimated using the same example biosolids, with continuous land applications at the same rate as needed for crop nitrogen demands. The times needed to reach the cumulative limits are summarized in Table VIII and range from 552 years for copper to 8,055 years for cadmium. This is assuming that all metal loss is through cropped plants and does not account from increased soil mass (a relevant change for that number of years).

The cumulative trace metals added over a 20 year period are most likely to accumulate in the plow layer and slightly deeper. There is some variability in where metals end up that was described in Section 2. The total cumulative metal concentrations are compared to Maine soils and shown in Table VIII. Using this example calculation, the total mean masses of cadmium, copper, and zinc in soil would increase in the plow layer by 144 to 240 per cent. The metal additions still fall within the natural ranges for these metals found in typical Maine soils (Houtman et al., 1995). Significantly smaller increases will occur for molybdenum and lead because their concentrations are so low in biosolids.

TABLE VIII. Nutrient and Metal Loading to Soils Using Cumulative Limits

The presence of potentially hazardous organic compounds in biosolids is explicitly managed under Chapter 419 for dioxin and under Chapter 418 for other listed compounds (579 compounds, many of which are organic compounds). There are few of these listed compounds detected in Maine’s sewage sludges that could ultimately be in biosolids. Although there are genuine concerns about emerging contaminants, the present screening requirements appear to be adequate for most situations since the majority of the organic compounds detected in sewage sludge are decomposed in soils. Additional soil testing at land applications sites would help define changes to soil quality.

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5.4 Water Quality
The protection of water resources, both surface and ground, is accomplished through the siting criteria for permitting utilization sites and restrictions on stockpiling. There is not any systematic monitoring of water quality adjacent to biosolids land-spreading sites. The indirect evidence for surface water quality is that the Maine Chapter 419 regulations adequately manage nutrient loss in runoff. Overall, Maine’s surface waters in rural areas have shown continual improvement in classification, including some streams in agricultural areas (Maine DEP, 2004). Proper site management to control soil erosion and to manage buffer strips around draingeways and water bodies has worked. Protection of groundwater has been harder to assess because much more expense and effort is needed to make a determination. This is further complicated by the use of manure and chemical fertilizers on the same fields as biosolids. In areas of intense agriculture, groundwater may contain elevated concentrations of nitrogen that cannot be attributable to any single source (Pinette, 1993; Pinette et al., 1999).

Field stacking of Class B biosolids can affect groundwater by leaching high concentration liquids. Depending upon weather and soil conditions, leachate can form over several weeks and move below the root zone. Transport of nutrients and other soluble constituents to depths greater than 1 meter can occur below the stockpile. The Maine rules for field stacking are not sufficient to protect groundwater quality directly below unlined stockpiles. Improper storage or failure of a storage containment structure has contributed to groundwater contamination (nitrogen) at four locations (Maine DEP, 2004). This represents a very small fraction (0.7%) of all the 536 licensed biosolids utilization sites or composting facilities in Maine. The potential for stockpiles to affect water quality is probably much greater because the state has monitored very few sites. According to unpublished data collected by the Maine DEP, groundwater impacts were documented at six of eight sites with required monitoring. In general, the occurrence rate and magnitude of groundwater contamination can not be estimated due to insufficient monitoring. The concentrated solutions associated with storage sites present a very different situation from properly spread biosolids where leachable constituents are loaded at rates more conducive to plant uptake. Properly applied biosolids probably have had minimal impact to groundwater quality (McDowell and Chestnut, 2002). More water quality monitoring would define the occurrence and magnitude of impacts to water quality.

Pathogen transport in waters is not addressed explicitly by Chapter 419. The available research indicates that pathogens usually attach to solids and as long as erosion is prevented, pathogenic organisms are immobile. Surface exposure to ultraviolet radiation and drying rapidly destroys organisms that remain after Class B treatment. Pathogen viability in groundwater is attenuated by soil absorption. The available data support the adequacy of the Maine rules.

5.5 Air Quality
Chapter 419 regulations address controlling odors coming from biosolids. The control of odors during composting, storage, and land application is a major source of complaint about the use of biosolids. Minimizing the impact of odors associated with Class B biosolids is an operational issue. Difficulties in controlling odors illustrate the limitations of both control technology and regulatory oversight. Nevertheless, the number of active permits relative to the occurrence of nuisance odor complaints indicates that most biosolids programs have successful air-quality management techniques. The mandated setback distances from occupied dwellings provide thousand-fold dilutions of odor-causing compounds.

A new concern about pathogenic bioaerosols has grown since the Chapter 419 rules were completed. The studies reported in this document concur that pathogen transport, as air-suspended particles, is possible over relatively short distances. Since biosolids have significantly reduced concentrations of pathogens relative to raw sewage sludge, the current setbacks for odor control are also likely protective of public health from bioaerosols. This aspect of biosolids regulation will need to be addressed in future revisions of the regulations after more research is completed.

5.6 Sustainability
The current rules for the agronomic utilization of residuals do not incorporate the full concept of sustainability (O’Connor et al., 2005). Sustainability, in its simplest form, means a process that balances present day needs with that of the physical world and the demands of future generations. It fuses the daily and future sustenance of human society with the dynamics of an agricultural ecosystem, all subject to the forces that energize economies (Dentel, 2004). The Chapter 419 rules define nutrient management goals that fall within a range of years and metal loading rates that could cap in 20 years, far short of multiple generations.

A field lifetime is almost impossible to define because many variables must be managed. Agricultural fields in some parts of Europe have been farmed continuously since the Iron Age. A sustainable process must have a very long life-cycle. Historical evidence shows this to be a logical desire for agriculture. The prospect of feeding people for centuries to millennia underlies the philosophy of sustainability. Sustainable practices lie within a larger context of economics (profitability), social benefit (food availability), and environmental health. These components need to be considered as a whole to be balanced. Biosolids utilization needs to be managed as part of a sustainable agronomic system. The generation of biosolids is the direct consequence of making surface waters cleaner and sustainable. The best use of biosolids is equally important.

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5.7 Management
An examination of how the State of Maine actually manages the biosolids program was not an explicit objective of this review. The staff of the Maine Department of Environmental Protection should be commended for developing the rules that make up Chapter 419-Agronomic Utilization of Residuals. The research reviewed supports most of the assumptions that are the basis for the rules. The body of scientific research continues to grow and the regulatory process can be adaptive to incorporate new knowledge. The Department has the authority under 38 M.R.S.A. § 1304 to revise Solid Waste Management Rules, including those for regulation of biosolids.

Staffing levels within the Department are low relative to the work load. Staff are required to perform numerous tasks: review and process program applications and site licenses; review required monitoring submissions; approve annual utilization reports; audit operations; approve new technologies; and investigate complaints. The workload required to provide regulatory oversight for 536 sites is divided between five staff in three offices. Time consuming tasks, such as site inspections, clearly have to be sacrificed to other duties of regulatory oversight. This high workload appears to be the rule in the region; other New England states also struggle with few staff assigned to biosolids management.

These demands on staff time affect the Department’s ability to deal with new issues that require policy decisions. Also, the public perception of an agency that may not be able to respond quickly to complaints works against the long-term viability of land-application programs. The public needs to feel confident that the Department can respond to concerns about biosolids and insure that they are protected from unnecessary risks. In particular, what is the Department’s ability to assess quality and perform spot checks? Should there be more field inspections? How can the Department effectively communicate risk management to the public? Clearly, more staff is desirable and there are creative options to cross-train other State agencies to assist in collecting field information.

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