Bay Journal

Biosolids not a threat to environment, human health

  • By Michael Wardell on April 01, 2010
  • Comments are closed for this article.

Nutrient management is a topic of concern to everyone interested in protecting the Chesapeake Bay. This includes engaged private citizens, farmers, regulators, environmental professionals and wastewater managers. There is a danger in trying to pin the blame on a particular nutrient source, whether it is inorganic fertilizers, animal manures, or in the case of a recent commentary, biosolids (See "PA towns prevented from protecting farms from sludge," January 2010.)

To protect the Bay and address climate issues, the time has come to start looking at the complete U.S. wastewater treatment infrastructure.

Over the decades, we have invested trillions of dollars to develop the world's most advanced system. Outbreaks of diseases such as cholera have been virtually eliminated. One only has to read about the recent cholera outbreak in Zimbabwe or imagine the sanitary conditions created by an earthquake in Haiti to gain an appreciation of this benefit.

Technological advances have improved the collection, conveyance and treatment of sewage. Consider that individual septic systems now average $10,000-$20,000 per house to install. Consider that the city of Philadelphia's wastewater treatment plant alone requires 2,980 miles of underground pipe to work. Imagine 50,000 fans showing up for a Ravens game with no sewage system. All of these benefits occur with almost no notice from the public.

Approximately 7 million dry tons of residuals are produced by the wastewater treatment plant infrastructure system in the United States each year. A portion is further treated to produce biosolids, and about 3.5 million dry tons of biosolids are beneficially used as a fertilizer or soil amendment each year. Residuals are also land-filled, incinerated or managed in another manner not involving use on the soil.

In Pennsylvania, the most recent survey by the Department of Environmental Protection showed that 58 percent of the biosolids were land-applied or composted, 27 percent were land-filled, and 15 percent were incinerated.

Land application is often, but not always, the most cost-effective method of managing biosolids, and decades of science tell us it is also a safe and environmentally sound management option.

Biosolids is not a term coined to sell a product. There is a substantial difference between sewage sludge and biosolids. Sewage sludges are the insoluble materials and organisms that remain when wastewater is treated. Sludges may be digested, dried, have lime added to them, or a combination of these treatment processes. These processes involve biological, chemical and physical processes (like heating) which alter the chemical and physical properties of the sludge, destroying bacteria and breaking down many of the organic chemicals present in the untreated sludge.

Biosolids are sewage sludges that have received additional treatment to destroy bacteria and pathogens; stabilize the material to reduce odors and the potential to attract vectors, such as flies; and in many cases, to produce energy during this treatment process. They also contain valuable organic matter and essential plant nutrients.

Biosolids provide not only organic matter to the soil, but both the nitrogen and phosphorus are in forms that are slowly released to the crops. Much of the nitrogen is in the organic form, which is not subject to leaching from the soil into the groundwater. Research at several universities, including Penn State, has shown that the phosphorus is also bound to organic matter and minerals in the biosolids, and is either not available or is slowly released to the growing crop.

When a farmer uses biosolids in place of commercial fertilizers, he is helping to protect the Bay in many ways. The regulations governing the use of biosolids limit the application rates to the nitrogen needs of the crop, meaning there is little excess nitrogen to leach into groundwater. Buffer areas are imposed, which provide setbacks from streams and swales, limiting the potential for nutrient runoff. The organic matter in biosolids improves soil tilth, which serves to increase the water-holding capacity and the soil's ability to retain nutrients.

Recent research has shown that biosolids encourage the production of compounds in the soil that help to reduce drought stress in crops, improving plant health and increasing yields. Farmers using biosolids are required to have nutrient management plans, which are essential to ensure that nutrient application rates do not exceed the needs of the crop.

Looking beyond the boundaries of our region, when a farmer uses biosolids instead of commercial fertilizers, he is reducing the greenhouse gas emissions associated with the production and transportation of the latter.

Biosolids are extensively tested on a regular basis for a variety of compounds, including nutrients, metals and organic chemicals. A study by Penn State published in 1999 showed that median biosolids quality in Pennsylvania met the most stringent quality standards in state and federal regulations, and metal loadings are orders of magnitude lower than what is allowed by regulation.

In addition, this study showed that biosolids also met the more stringent requirements suggested by Cornell Waste Management Institute and others in the 2007 "Guidelines for Application of Sewage Biosolids to Agricultural Lands in the Northeastern U.S." Since 1997, it is reasonable to assume that biosolids quality has improved as industrial pre-treatment programs have expanded and enforcement has improved.

Continued research over the 17 years since the federal regulations were promulgated have added to our knowledge of the constituents of biosolids and improved our understanding of how some of these chemicals move or are sequestered during treatment and after land application. This information continues to be used by regulators and biosolids managers in their decision-making process. This continuing research has not raised undue concern among those charged with protecting human health and the environment because this new information has helped to confirm the safety of current biosolids treatment and management options.

The mere presence of synthetic organic chemicals does not mean they are a danger to the environment or human health. The EPA has recognized the need to consider what compounds are in biosolids, their fate in the environment and what research or regulation is appropriate to ensure the continued safe use of biosolids as an agricultural amendment.

The enforcement of biosolids quality and management regulations in Pennsylvania falls to the DEP's regional offices. At least one inspector in each region is assigned to overseeing the biosolids management programs of the wastewater treatment plants in that region. On-site inspections of both the wastewater treatment plant and the land application facilities are routinely conducted. Inspectors take random samples of biosolids to confirm their quality, and respond quickly to citizen complaints when they occur.

Interviews conducted with all of the regional inspectors revealed that the biosolids management programs were well-run with a minimum of complaints or violations. Enforcement and oversight in Pennsylvania is effective and protective of both human health and the environment.

The concern for human health is one of the major factors regulators and biosolids managers consider when developing regulations or determining how best to manage biosolids. There is no evidence of health impacts associated with biosolids, and there have been no epidemiological studies that confirm a causal link.

Most recently, the Biosolids Expert Panel convened by the Virginia General Assembly made the following observation in their final report. "In the past 18 months, the Panel uncovered no evidence or literature verifying a causal link between biosolids and illness, recognizing current gaps in the science and knowledge surrounding this issue. These gaps could be reduced through highly controlled epidemiological studies relating to health effects of land applied biosolids, and additional efforts to reduce the limitations in quantifying all the chemical and biological constituents in biosolids."

Additional support comes from a 2007 study by three epidemiologists of Virginia's Department of Health who concluded: "Although much still needs to be learned about the content, bioavailability and fate of chemicals and pathogens in biosolids and their health effects, there does not seem to be strong evidence of serious health risks when biosolids are managed and monitored appropriately. Human health allegations associated with biosolids usually lack evidence of biological absorption, medically determined human health effects, and/or do not meet the biological plausibility test."

The Cornell Waste Management Institute, critics of biosolids beneficial use, were co-authors of a guide to the use of biosolids, published in 2007, which does nothing to address the concerns often raised regarding metals or synthetic organic chemicals. That document provides guidelines for the use of biosolids that do not differ substantially from either the federal regulations or the sound agricultural practices used by farmers and biosolids managers today. The suggested metal limits-more stringent than the risk-based federal regulations-can be met by a majority of wastewater treatment plants in Pennsylvania.

Our agricultural soils are a precious resource, and research conducted the last 40 years provides the basis on which we can use the valuable nutrients and organic matter in biosolids without placing that resource at risk. For many farmers who use biosolids, the savings they realize in reduced fertilizer costs, improved soil conditions and increased yields means the difference between staying in business or losing the farm to residential or commercial development.

We continue to study the potential uses of biosolids; and there may be technologies on the horizon which derive energy from these materials. We must not, however, forget that using biosolids as a soil amendment closes the nutrient cycle, returning nitrogen, phosphorus and organic matter from the food we eat to the soils which produced them. We will continue to improve our practices and understanding of how biosolids interact with the environment, and that understanding will help us to continue to manage these materials in a safe and effective manner. Local regulations that seek to ban the use of biosolids do nothing to protect agriculture nor do they enhance the protection of the Chesapeake Bay.

In 2008, approximately 0.4 percent of the farmland in Pennsylvania received biosolids. These materials, which decades of continuing research has shown to be a safe and effective soil amendment, pose neither a threat to the health of citizens near the farms nor the Chesapeake Bay.

The discussion we need to be having is about how we protect and encourage agriculture, which is an important economic engine in our region, while at the same time protecting the Bay from nutrient runoff from all sources, including urban runoff, rural septic systems and improperly managed agricultural operations. Those discussions, which will include biosolids and how best to manage them, as well as all other nutrients sources and their impacts, will help to bring all of the stakeholders together and make a lasting and significant improvement in the health of the Chesapeake Bay.

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About Michael Wardell

Michael Wardell is the executive director of the Mid-Atlantic Biosolids Association.

Read more articles by Michael Wardell

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