What are biosolids?
Biosolids can be safely applied to soil as a fertilizer and/or soil conditioner to improve and maintain agricultural and forest lands as well as to restore damaged acreage. Biosolids is the final product, safe to recycle and rich in plant available nutrients, created through multiple processes and scientifically-advanced treatment of sewage sludge generated by thousands of Publicly-owned municipal water treatment facilities all across the country.
Since every community of any size must process the wastewaters generated by its population, recycling biosolids for added benefit to agriculture and horticulture makes sense. Created during the past 30 years, the biosolids process has resulted in the rapid and remarkable cleansing and restoration of America’s rivers and streams.
What is wastewater?Wastewater comes from home kitchens, bathrooms, and laundries as well as process and washwater from industries and businesses. It is treated in septic systems or at wastewater treatment facilities. Wastewater is mostly water (about 99.5%). Less than 1/2% is suspended solids which must be removed so the water can be returned safely to the environment. The suspended solids are either inorganic (sand, grit, nutrients such as nitrogen and phosphorus, salts, and metals) or organic (primarily waste products of animal or vegetable origin). Wastewater also contains living organisms such as bacteria, some of which come from the human digestive system.
Why do we have wastewater treatment?
Wastewater treatment is necessary to protect the public health and environment. Discharging raw sewage into lakes and streams harms those environments and can spread disease. In lakes and streams, native bacteria, algae, and other microscopic organisms (microbes) use the waste as food. These microbes eat and reproduce using the available oxygen dissolved in the water. If too much waste enters a waterbody, the microbes will use too much of the available oxygen needed by fish and other aquatic life.
How does wastewater treatment work?
Publicly-owned municipal wastewater treatment facilities use the same biological and physical processes by which water is cleaned in nature. The steps to clean water include industrial pre-treatment, preliminary treatment, primary treatment, and secondary treatment.
What is industrial pre-treatment?
Certain industries create wastewater that contains unacceptable levels of chemicals or metals. These industries must pre-treat their wastewater before sending it to the community wastewater treatment facility. Pretreatment regulations were developed under the Clean Water Act. These regulations ban the discharge of any toxic substance that might...
- Hinder the wastewater treatment process,
- Pass through the wastewater treatment plant and contaminate the plant’s receiving waters, or
- Concentrate in the biosolids.
Who enforces pre-treatment regulations?
State and local governments usually enforce pretreatment programs. Permits are generally required by federal or state regulatory agencies before industrial discharges to the community treatment facility are allowed. Reporting and monitoring requirements are also usually set by state and local regulatory agencies.
How does pre-treatment work?
Industries use physical, chemical, or biological methods to pre-treat their wastewater. Some examples:
- Physical – filters, sedimentation tanks, flotation;
- Chemical – bind contaminants to particles which are removed by physical methods, or destroy the contaminants;
- Biological – use microbes to consume organic material or nutrients.
What is Preliminary Treatment?
Preliminary treatment is the initial physical screening of wastewater at a wastewater treatment facility. This process removes debris such as rags, wood, and plastics.
What is Primary Treatment?
At a wastewater treatment facility, after grit and debris are removed, wastewater flows into a large sedimentation tank or "clarifier." Here wastewater is held relatively motionless for several hours. Solids settle and collect on the bottom; these are called "primary solids" or "primary sludge." Grease and oils float to the top and are removed for either further treatment or disposal at a landfill. Preliminary and Primary Treatments remove about 50-65% of the solids in wastewaters.
What is Secondary Treatment?
Secondary treatment is a biological process which relies on the same microbes that clean natural waterways. After primary treatment, wastewater is held in another large tank in which microbes feed on the suspended and dissolved solids in the wastewater. Treatment plant operators carefully monitor and control the temperature, pH (acidity), and amount of oxygen in the wastewater to ensure the health of the working microbes. Gradually, older microbes, which have eaten their fill, die and settle to the bottom. They take with them the suspended and dissolved solids that they consumed. The nearly pure water flows out of the top of the secondary treatment tank and is disinfected prior to being released into a river, ocean, or groundwater. The collected "secondary solids" are mixed with the "primary solids" and treated and tested for recycling. Secondary Treatment removes about 85% of the remaining suspended solids and nutrients.
What type of monitoring occurs during the wastewater treatment process?
Wastewater treatment facilities constantly monitor incoming wastewater, internal flows, outgoing clean water ("effluent"), and biosolids to properly control the treatment process. Each facility must document compliance with exhaustive requirements of the federal Clean Water Act, including the "Part 503" regulations. Monitoring requirements include:
- Samples collected at various locations in the facility,
- Frequency of sampling, and
- Frequency of reporting to regulatory agencies.
What types of testing are undertaken?
There are several types of testing:
- Physical examination – color, odor, turbidity, temperature;
- Biological examination – testing for certain indicator organisms;
- Chemical examination – oxygen levels, pH, total solids, volatile solids, nutrients, and priority pollutants.
Depending upon the certification of the treatment plant’s laboratory, testing may be done in-house or by other laboratories.
What do "Class A" and "Class B?" mean?
The federal Clean Water Act Part 503 regulations identify two classes of pathogen reduction.
Class A: Class A biosolids undergo a "Process to Further Reduce Pathogens (PFRP)." Pathogens are reduced to a level similar to the native soil and environment. Class A biosolids products can be used on home lawns and gardens, parks and golf courses, and other places where public contact is likely. Class A biosolids products include composted biosolids, lime pasteurized biosolids, and fertilizer pellets. Class A biosolids products are sometimes ingredients in soil amendments, potting soils, and slow-release fertilizers.
Class B: Class B biosolids undergo a "Process to Significantly Reduce Pathogens (PSRP)." This means that while pathogens are significantly reduced to levels which are often below those found in animal manures, additional best management practices (BMPs) are required at the site where they are used. Class B biosolids are used in bulk as fertilizers in agriculture and forestry and to reclaim barren lands. Site permits are required for Class B biosolids use.
Is biosolids recycling safe? How do we know?
Yes! Federal and state standards and management practices for biosolids recycling were developed from a detailed scientific risk assessment ever completed by the U.S. Environmental Protection Agency (EPA). Input included research and expertise from the U.S. Department of Agriculture and premier universities including the Universities of Arizona, California, Colorado, Florida, Maine, Michigan, Massachusetts, Minnesota, New Hampshire, Oregon, Vermont, Washington, and Colorado State, Ohio State, Penn State, and Cornell Universities.
The research strongly supports the finding of the U.S. Environmental Protection Agency (EPA) that: "In fact, in all the years that properly treated biosolids have been applied to the land, we have been unable to find one documented case of illness or disease that resulted" (Martha Prothro, former Deputy Assistant Administrator for Water, EPA, statement made September 1, 1992).
The National Research Council of the National Academy of Sciences stated in an exhaustive 1996 review of biosolids recycling:
"While no disposal or reuse option can guarantee complete safety, the use of these materials in the production of crops for human consumption, when practiced in accordance with existing federal guidelines and regulations, presents negligible risk to the consumer, to crop production, and to the environment" (National Research Council, 1996. See www.nap.edu/readingroom/books/sludge/index.html)
For more about the EPA risk assessment, contact the NEBRA office or EPA at www.epa.gov/owm or the Water Environment Federation at www.wef.org.
Will the use of biosolids adversely impact nearby surface waters and/or groundwater?
No. Properly treated and properly managed biosolids products do not have a negative impact on surface water or groundwater quality. As with any fertilizer or soil amendment, best management practices must be followed to prevent impacts via surface water runoff or via leaching to groundwater. By law, biosolids recycling programs must follow such best management practices; the same is not true for the use of manures and chemical fertilizers. Numerous biosolids recycling programs have caused documented improvements in the quality of surrounding water bodies. How? By enriching soils and helping vegetation grow more vigorously. This results in reduced soil erosion and stabilization of on-site contaminants that had previously contributed to stream and groundwater pollution.
Are There Rules About Where Biosolids Can Be Applied?
There are different rules for different classes of biosolids. Class A biosolids are highly-processed and contain no detectible levels of pathogens. Once permitted, Class A biosolids that meet strict stabilization requirements and low levels metals content may be sold as a fertilizer or soil conditioner Class B biosolids are treated to destroy 99.99% of the monitored organisms, but as with many soil amendments, contain detectible levels of pathogens. There are buffer requirements, public access restrictions, and crop harvesting restrictions for virtually all forms of Class B biosolids.
Will the value of my property be adversely impacted if biosolids are used in my neighborhood?
No. Studies have shown that biosolids are beneficial. By using biosolids, farmers and other landowners are managing the nutrients and processes on their properties more carefully and responsibly than the average landowner. In addition, those who use biosolids may be benefiting from a more efficient fertilizer option and helping their farm fields or other open lands to be more profitable. The more profitable their operations are, the more likely it is that farmers and other landowners will keep their properties green and open for the neighborhood to enjoy.
What about odors?
Most Class A biosolids products (e.g. compost, fertilizer pellets) are basically odor free or have a slight earthy smell. Some bulk Class B biosolids products have odors similar to animal manures used to fertilize farm fields. As with manures, when bulk Class B biosolids are land applied, some odors are possible, but they are temporary.
Is biosolids recycling the right thing to do? Why?
Yes!
- Biosolids recycling returns nutrients and organic matter to soils.
- Biosolids recycling avoids the need for more costly landfill space or incinerators.
- Biosolids products are efficient fertilizers and soil amendments that build soils, restore barren lands, and help keep landscapes open and growing.
- Biosolids recycling has been proven safe and beneficial through decades of scientific study and peer review.
Where Can I Find Out More About The Regulations?
The biosolids rule is described in the EPA publication, A Plain English Guide to the EPA Part 503 Biosolids Rule. This guide states and interprets the Part 503 rule for the general reader. The EPA has also prepared A Guide to the Biosolids Risk Assessments for the EPA Part 503 Rule which shows the many steps followed to develop the scientifically defensible, safe set of rules.
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Note: Web site text prepared in
part with use of information provided by the Virginia Department of Health, the
Biosolids Institute, and the North East Biosolids and Residuals Association,
U.S.
Environmental Protection Agency, Water Environment Federation, National
Biosolids Partnership, and Biosolids.com.
