SUMMARY of Interpreting Science in the Real World Session
Robert K. Bastian
U.S. Environmental Protection Agency, Office of Wastewater Mgnt., Washington, D.C. USA
What we know:
The design guidance, regulations, and management practices currently employed by modern sustainable land application projects involving municipal and industrial effluents, sludges and manures have evolved over many years, built upon extensive research and demonstration efforts as well as experience with both pilot- and field-scale projects. Current land application practices and our understanding of them have evolved over time. Today’s land application practices, which are designed to effectively treat and/or recycle wastes, have gradually developed from efforts to cheaply dispose of these relatively low-value waste materials without much regard for the protection of the environment.
Environmental problems, such as elevated nitrates in the underlying shallow groundwater, severe erosion and runoff from application sites into nearby water bodies, poor cover crop performance, severe odors and other undesirable site conditions resulted from the excess moisture, organic matter, and nutrient loadings, were often associated with historical municipal and industrial effluent and sludge land disposal systems, due to excessive moisture, organic matter, and nutrient loadings. Similar problems have also resulted from excessive manure application rates to farmland in some areas where the number and size of confined animal production facilities have dramatically increased, requiring feed to be imported rather than produced on their own land, thereby limiting the animal producer’s land base available for effectively recycling manure by land application. By applying our current scientific knowledge on how the soil can function as an integral part of the treatment and recycling system in a sustainable manner, we can establish sustainable land application systems that avoid such historical environmental problems.
Modern day land application projects can effectively treat and recycle wastewater effluents and organic residuals using the soil as an integral part of the treatment system in a sustainable manner. In addition to their use on productive farmland, treated sewage sludge (“Biosolids”), industrial residuals, and manure can be effectively used on forests and marginal lands with poor soils as organic soil conditioners and a source of nutrients in a manner that enhances soil conditions and helps establish sustainable vegetative cover and maximize crop yields. Both types of land application practices can be utilized in a sustainable manner to minimize negative impacts on the environment and to restore disturbed areas with poor soil conditions (e.g., resulting from construction activities, surface mining, forest fires, over grazing, etc.) - even highly contaminated sites (e.g., resulting form mining, smelting, and other industrial activity).
Such sustainable land application systems depend heavily upon the soil as an integral part of the treatment and/or recycling system to effectively process and manage macro- and micro-nutrients, inorganic and organic contaminants, and pathogens. Taken as a whole, the information that has been developed over the years describing the soil and crop benefits derived from land application practices, the fate and effect of pollutants present in the land applied effluents and organic residuals suggests that sustainable land application systems can be established and maintained under a wide range of conditions. Optimal crop yields can be achieved using effluents as a water supply and source of nutrients, effluents and organic residuals as a source of nutrients and soil amendments. Contaminants, such as excess trace heavy metals, toxic organics, nitrogen and phosphorus, as well as pathogens can be controlled and effectively managed by land application systems. The soil reactions to the contaminants in the waste that is applied represent the key to sustainable land application systems. The soil and its associated microorganisms and vegetation react to the specific nutrient, organic matter, heavy metal, inorganic and organic contaminant, or pathogen additions and may modify the form of the contaminant through direct oxidation/reduction reactions, adsorption/desorption, biodegradation, plant uptake, etc. In some cases the reactions may be quite temporary, while in other cases they are essentially permanent, or nearly so unless the overriding factors controlling the soil properties are changed by external sources. Scientists don’t need to reinvent the wheel by studying the fate of each and every contaminant that may be present in each and every waste source in order to predict how they will behave in land application systems over time and the extensive available technical information can be effectively applied in the development of technical guidance and regulatory requirements for the development of sustainable land application practices.
However, science and the available technical information are only part of what goes into developing sustainable land application projects and their applicable regulatory requirements and management practices in the real world. The controls imposed on land application practices are generally aimed at protecting public health and the environment, but also must take into account such factors as available control technologies, cost-effectiveness, public policy objectives, public acceptance and of course political realities. During the early years of practice, efforts were made to base land application requirements upon good management practices and the general consensus of the scientific community that were often softened by the realities of best available control technologies and affordability. The “plant/soil barrier” was viewed as providing an effective means of protecting humans from exposure to excessive levels of most chemical contaminants. Over time, loading limits for specific chemicals have been developed by various means ranging from not allowing any increase in background chemical concentrations to establishing acceptable levels based upon various risk assessment and modeling approaches. Pathogen controls have primarily been based upon treatment through process technology controls and waiting periods to allow for natural die-off. The basic paradigm used for human health risk assessment - hazard identification, dose-response assessment, exposure assessment, and risk characterization (NRC, 1983) - has become the usual framework behind the development of many of the regulations in the U.S., although less so in Europe. This approach has established limits on the chemical contaminants associated with sustainable land application practices. Of course the risk assessment-based approach is data intensive, and often leads to the use of conservative default values and sensitivity analyses, Monte Carlo simulations, etc. to address areas of uncertainty. Concerns raised over emerging pathogens and chemicals or other areas for which little or no data are available tend to be put off for future consideration when more adequate scientific data are generated.
The importance of public involvement and the need to gain and maintain public acceptance in maintaining sustainable land application projects simply can’t be over stated. Most modern projects are faced with the realities of local neighbors and in many cases individuals and/or public interest groups that may find even the concept of land applying wastewater effluents, sludges, manures and other residuals as simply unacceptable. While many states have adopted standards or guidelines to accommodate land treatment and effluent reuse as well as broad goals calling for increased recycling of organic wastes in an effort to conserve landfill capacity, both of which strongly support the objectives of land application practices, NIMBY reactions by local neighbors to notices issued about proposed land application projects and to the start-up of new projects are now the norm. Unless their concerns and interests are taken into account and accommodated by planned projects, such local concerns can easily gain momentum and grow into formal project opposition, and may result in the involvement of external groups and individual with even broader agendas to create political and legal barriers to moving projects forward.
In many cases, the initial basis for local concerns has been linked to the production of odors and/or other nuisance conditions (e.g., noise, dust, flies, truck traffic, etc.) associated with land application projects. When such concerns aren’t effectively dealt with, complaints about such nuisance conditions often escalate to complaints about potential health impacts that may result from the odors, potential bioaerosols, dust, runoff, etc. from the land application site. This then raises the question - When does exposure to odors or dust and the compounds and/or potential bioaerosols associated with them lead to health impacts that should be controlled? - which will likely vary considerably due to individual sensitivities. Attempting to regulate land application of wastewater effluents, biosolids, industrial residuals and manures based upon the potentially most sensitive individuals to odors could lead to very restrictive practices in the future.
Efforts to actively involve potentially affected and interested stakeholders in the development and implementation of sustainable land application practices as a means of avoiding problems that might otherwise be overlooked until it is too late have lead to the establishment of various types of voluntary partnerships. Environmental Management Systems, ISO 14,001 Standards, and various other coalitions that follow Demming’s basic “Plan/Do/Check” management model principles encourage achieving continuous improvement and going beyond just complying with the minimum regulatory requirements as an approach for resolving and solving issues and concerns associated land application practices so that they can be less controversial and more sustainable.
Legislative statutes at the Federal and state levels contain numerous provisions encouraging the safe and beneficial recycling of wastewater effluents, sludges and organic residuals, and require establishment of guidance and regulatory requirements for governing various land application practices as well as other use and disposal practices. Such mandates, along with the well-established formal rule-making process requirements, must be considered during the development of regulations that impact land application practices. In addition to formal regulations, both federal and state agencies often develop and issue policy and guidance documents to help explain regulations and voluntary programs, as well as to provide technical assistance. While the regulatory agencies are generally committed to using sound science in their decision-making, many other factors go into the development of policies, regulations, and guidance documents, including implementation costs, technical feasibility, economic effects on small businesses, social and political considerations.
At least some of the constraints on agricultural land application practices created by the various regulations and local requirements imposed on them can be overcome when projects are established that help deal with other environmental problems such as the restoration, revegetation and rehabilitation of highly disturbed and contaminated sites. After 30 years of field experience and numerous well documented research and demonstration projects, land applied organic residuals have become an effective tool for reducing the bioavailability of heavy metals and establishing sustainable vegetative cover on a number of highly contaminated sites in the U.S. and overseas, including a number of SUPERFUND and Brownfield sites.
When establishing sustainable land application projects, there is almost always an issue associated with nutrient contents that don’t effectively match the nutrient needs of the crop or vegetation to be grown on the site. In an effort to meet these needs and appropriately balanced the available nutrients, supplemental sources of nutrients are often applied. Comprehensive nutrient management planning plays a key role in avoiding the eventual buildup of nitrates, phosphorus or other nutrients to the point where they become contaminants in the soil, stormwater runoff, and/or underlying ground water.
Numerous, in-depth, systematic research programs have produced information that has helped advance our understanding of how soil-based treatment systems work, address new areas of concern when they arise, and improve the overall design, performance and reliability of land application systems as sustainable soil treatment and recycling systems. Many facilities across the country continue to collect important data associated with the performance of their operating land application projects, but precious few programs are collecting the types of data needed to effectively respond to the questions being raised about emerging pathogens and new chemicals of concern associated with land applied wastewater effluents, biosolids, industrial residuals and manures. Research projects supported by WERF, U.S.EPA, USDA and others will help fill these information gaps over time, but more effort is needed. In-depth, systematic research programs to support studies aimed at producing information that can help advance our understanding of how soil-based treatment systems work, address new areas of concern as they arise, and continue to improve the overall design, performance and reliability of land application systems as sustainable soil treatment and recycling systems is as important today as ever.
Where do we go from here?
While extensive information is currently available on many issues associated with land application practices, further research in a number of areas could lead to better information and tools that would improve our ability to design and operate as well as effectively manage and regulate sustainable land application systems. These include such areas as:
· Develop validated methods for effluent/biosolids/organic residuals sample handling and analysis, especially for pathogens and persistent organic pollutants
· Develop better indicator organism and pathogen information
· Further evaluation of factors controlling chemical contaminant and pathogen removal rates
· Develop quick/inexpensive monitoring methods (e.g., for real-time measurement of pathogens, indicator organisms, persistent organic pollutants, etc.)
· Develop better data on emerging pathogens and persistent organic pollutants to support risk assessments
· Document successes achieved by applying various regulatory controls and Best Management Practices (BMPs) vs natural cycles impacting the fate of nutrients, pathogens, inorganics and persistent organic pollutants
· Develop more effective outreach materials (e.g., detailed reports, brochures, one page fliers, etc.) on technical issues associated with sustainable land application practices – such as the Phosphorus brochure developed jointly by USDA/ARS and U.S.EPA
· Evaluate the effectiveness of various techniques for reducing public opposition, including mechanisms to promote dialogue, education of the public, etc.
· Design the ultimate 1,001th experiment with appropriate stakeholder involvement
· Develop better odor management models and guidance
· Develop better in information on the levels and sensitivities of individuals to bioaerosols, odors and chemicals associated with land applied effluents and residuals
· Evaluate techniques to facilitate more interaction and interface with solid waste management programs
· Undertake environmental lifecycle analyses of sustainable land application projects – including evaluation of all inputs (e.g., energy, chemicals, etc.) and ultimate fate of contaminants (e.g., nutrients, inorganic and organic compounds, and pathogens)
· Develop guidance materials that go beyond meeting CAFO regulatory requirements (e.g., BMPs for odor management, groundwater protection, reducing air emissions, pathogen reduction and metals)
· Evaluate consumer attitudes (e.g., willingness to pay more, etc.) to Green Power projects such as the one in Gainesville, FL
· Develop renewable energy project initiative (e.g., subsidies, grid purchase back requirements, etc.) to facilitate CAFO integrator supported Green Power projects and marketing of power to their own producers
· Evaluate use of credits for C-sequestration, restoration, etc.
Future efforts to better address pathogen concerns and potential ecological impacts associated with land application practices will likely require the development of applicable methodologies for conducting more comprehensive pathogen and ecological risk assessments. Bioassay techniques for better evaluation of the effects of multiple stressors, complex mixtures and compound byproducts resulting from degradation in the environment as well as contaminants that may be present below effective analytical detection limits should also be addressed as a possible part of future regulatory strategies.