Solids Management
Solids Management
The solids that enter the wastewater treatment plant are separated from the water portion of the wastewater so that these “biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality” can be reused. This nutrient-rich, organic material is a valuable resource that just like any other fertilizer, can improve the condition of the of soil and contribute to better crop yields. Wastewater treatment plants that recycle biosolidsTreated sewage sludge that has met strict federal and state...
Processes
During wastewater treatment, bacteria and other microorganisms break down components in wastewater into simpler and more stable forms of organic matter. Non-organic matter also settles into sludge. For instance, small amounts (parts per million) of heavy metals and other potentially toxic materials, including flame retardants (PBDEs) and persistent organic pollutants, are commonly found in sewage sludge in parts per million levels. What does not settle into sludge leaves the treatment facility as a treated wastewater effluent. BiosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality in their liquid form look like muddy water and contain 1-10% solids. BiosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality may be dewatered in a second step of the treatment process, which turns it into a “cake” with the texture of a wet sponge. In this stage it contains 20 to 25% solids. Racine dewaters their biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality using belt filter presses to remove excess water from the product.
United States
According to the U.S. Environmental Protection Agency (EPA), biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality that meet the treatment and pollutant standards outlined in Part 503.13 can be safely recycled and used as fertilizer to sustainably enhance soil quality and promote plant growth. Following the 1991 Congressional ban on ocean dumping, the EPA established regulationsA rule or directive made and maintained by an authority., which continued to allow land application of biosolids—a practice previously permitted. Throughout the 1990s, the EPA actively supported biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality recycling.
The Part 503 regulationsA rule or directive made and maintained by an authority. were created with input from university researchers, EPA scientists, and the U.S. Department of Agriculture (USDA). These rules were based on a comprehensiveComplete; including all or nearly all elements or aspects of something. review of scientific studies and included the largest risk assessment the EPA had conducted at the time. However, that assessment did not evaluate the risks of pathogens or chemicals, and heavy metals were not classified as carcinogens under the regulationsA rule or directive made and maintained by an authority.. The final rule went into effect in 1993.
In 1997, municipal wastewater treatment plants in the U.S. produced an estimated 7.7 million dry tons of biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality, followed by 6.8 million dry tons in 1998, based on EPA data. By 2002, about 60% of these biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality were being applied to land as fertilizer and soil amendments.
BiosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality that meet Class B standards for pathogen treatment and pollutant limits can be used on land, but only with strict site restrictions and recordkeeping requirementsA thing that is needed or wanted.. Those that achieve Class A pathogen reduction or undergo equivalent treatment through a Process to Further Reduce Pathogens (PFRP) face the fewest usage restrictions. PFRP methods include pasteurization, heat drying, thermophilic composting (the most common, using aerobic digestion), and irradiation using beta or gamma rays.
While PFRP methods effectively reduce pathogens, they do not affect heavy metal concentrations and may or may not reduce other trace pollutants. Treatments like composting or alkaline stabilization, which involve adding other materials, may dilute total trace metal content in the final product.
History of Bio-Solids
Historically, the problem of human waste disposal began when communities first formed. At that time, population densities were low enough that the surrounding land or waterways could handle human wastes. Wastes that were applied to land increased soil fertility. As populations grew, the nearby land could not handle all the wastes, so they were dumped into streams and rivers that carried the problem “away.”
Some early cultures put their human waste to good use. For thousands of years, Chinese society returned sewage, called “night soil,”...
Evolution of Residual Solids/Biosolids
Before the era of wastewater treatment, municipal wastewater was untreated and biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality did not exist. BiosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality are an end product of municipal wastewater treatment and contain many of the constituents removed from the influent wastewater. BiosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality are a concentrated suspension of solids, largely composed of organic matter and nutrient-laden organic solids, and its consistency can range in form from slurry to dry solids, depending on the type of treatment.
Agricultural utilization of biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality was practiced since residual solids were first produced. Given our experience with the use of human excrement, sewage, and animal manure on croplands, the application of biosolids to agricultural lands was a logical development. As an early example, municipal biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality from Alliance, Ohio was used as a fertilizer as early as 1907. During the same period, Baltimore, Maryland used domestic septage in agricultural production.
Recent Advancements
Over the past 30 years, extensive scientific research worldwide has focused on understanding the fate of potentially toxic and pathogenic substancesA kind of matter with a specific composition and properties in biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality when applied to agricultural soils. This growing body of knowledge has driven the development of pollutant loading guidelines in the United States and Western Europe.
Since the late 1970s and early 1980s, source control and industrial wastewater pretreatment programs have been implemented to reduce industrial pollutants entering municipal sewer systems. These efforts have significantly lowered the levels of trace elements in wastewater and biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality, especially in industrialized cities. As a result, today’s municipal biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality contain far fewer trace elements than those studied in earlier decades.
The EPA first introduced biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality management regulationsA rule or directive made and maintained by an authority. under the 1972 Federal Water Pollution Control Act to prevent contaminants in biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality from entering the nation’s navigable waters. In 1977, Congress amended the Act requiring the EPA to develop guidelines identifying alternative uses and disposal methods for biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality. These guidelines also specify factors to consider when selecting appropriate management practices and set pollutant concentration limits that could interfere with biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality use.
In 1978, the EPA established limits on cadmium, PCBs, and pathogens in biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality. Then, in 1987, Congress amended Section 405 again, setting a timeline for creating biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality use and disposal guidelines. This amendment directed the EPA to identify toxic pollutants in biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality that might impact public health and the environment and to establish regulationsA rule or directive made and maintained by an authority. detailing acceptable management practices and concentration limits for these pollutants.
The 1987 amendment aimed to “adequately protect human health and the environment from any reasonably anticipated adverse effect of each pollutant.” It also mandates that any permit issued to publicly owned treatment works (POTWs) or other wastewater facilities must include technical standards for biosolidsTreated sewage sludge that has met strict federal and state standards for safety and quality use or disposal.
Frequently Asked Questions
They are nutrient-rich organic materials resulting from the treatment of domestic sewage in a treatment facility. When treated and processed, these residuals can be recycled and applied as fertilizer to improve and maintain productive soils and stimulate plant growth.
Biosolids are treated sewage sludge. Biosolids are carefully treated and monitored and must be used in accordance with regulatory requirements.
We have biosolids as a result of the wastewater treatment process. Wastewater treatment technology has made our water safer for recreation and seafood harvesting. Thirty years ago, thousands of American cities dumped their raw sewage directly into the nation’s rivers, lakes, and bays. Through regulation of this dumping, local governments are now required to treat wastewater and to make the decision whether to recycle biosolids as fertilizer, incinerate it, or bury it in a landfill.
Biosolids are created through the treatment of domestic wastewater generated from sewage treatment facilities. The treatment of biosolids can actually begin before the wastewater reaches the sewage treatment plant. In many larger wastewater treatment systems, pre-treatment regulations require that industrial facilities pre-treat their wastewater to remove many hazardous contaminants before it is sent to a wastewater treatment plant. Wastewater treatment facilities monitor incoming wastewater streams to ensure their recyclability and compatibility with the treatment plant process.
Once the wastewater reaches the plant, the sewage goes through physical, chemical and biological processes which clean the wastewater and remove the solids. The wastewater treatment processes work to control pathogens (disease-causing organisms, such as certain bacteria, viruses and parasites) and other organisms capable of transporting disease.
After treatment and processing, biosolids can be recycled and applied as fertilizer to improve and maintain productive soils and stimulate plant growth. The controlled land application of biosolids completes a natural cycle in the environment. By treating sewage sludge, it becomes biosolids which can be used as valuable fertilizer, instead of taking up space in a landfill or other disposal facility.
The application of biosolids reduces the need for chemical fertilizers. As more wastewater plants become capable of producing high quality biosolids, there is an even greater opportunity to make use of this valuable resource.
The National Academy of Sciences has reviewed current practices, public health concerns and regulator standards, and has concluded that “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.”
Biosolids may have their own distinctive odor depending on the type of treatment it has been through. Some biosolids may have only a slight musty, ammonia odor. Others have a stronger odor that may be offensive to some people. Much of the odor is caused by compounds containing sulfur and ammonia, both of which are plant nutrients.
The federal biosolids rule is contained in 40 CFR Part 503. Biosolids that are to be land applied must meet these strict regulations and quality standards. The Part 503 rule governing the use and disposal of biosolids contain numerical limits, for metals in biosolids, pathogen reduction standards, site restriction, crop harvesting restrictions and monitoring, record keeping and reporting requirements for land applied biosolids as well as similar requirements for biosolids that are surface disposed or incinerated. Most recently, standards have been proposed to include requirements in the Part 503 Rule that limit the concentration of dioxin and dioxin like compounds in biosolids to ensure safe land application.
The biosolids rule is described in the EPA publication, A Plan English Guide to the EPA Part 503 Biolsolids Rule . This guide states and interprets the Part 503 rule for the general reader. This guide is also available in hard copy. In addition to the Plain English Guide, EPA has prepared A Guide to the Biosolids Risk Assessment for the EPA Part 503 Rule which shows the many steps followed to develop the scientifically defensible, safe set of rules (also available from EPA in hard copy.)
Biosolids are used to fertilize fields for raising crops. Agricultural uses of biosolids, that meet strict quality criteria and application rates, have been shown to produce significant improvements in crop growth and yield. Nutrients found in biosolids, such as nitrogen, phosphorus and potassium and trace elements such as calcium, copper, iron, magnesium, manganese, sulfur and zinc, are necessary for crop production and growth. The use of biosolids reduces the farmer’s production costs and replenishes the organic matter that has been depleted over time. The organic matter improves soil structure by increasing the soil’s ability to absorb and store moisture.
The organic nitrogen and phosphorous found in biosolids are used very efficiently by crops because these plant nutrients are released slowly throughout the growing season. This enables the crop to absorb these nutrients as the crop grows. This efficiency lessens the likelihood of groundwater pollution of nitrogen and phosphorous.
Biosolids have been used successfully at mine sites to establish sustainable vegetation. Not only does the organic matter, inorganic matrix and nutrients present in the biosolids reduce the bioavailability of toxic substances often found in highly disturbed mine soils, but also regenerate the soil layer. This regeneration is very important for reclaiming abandoned mine sites with little or no topsoil. The biosolids application rate for mine reclamation is generally higher than the agronomic rate which cannot be exceeded for use of agricultural soils.
Biosolids have been found to promote rapid timber growth, allowing quicker and more efficient harvest of an important natural resource.
Yes, biosolids may be composted and sold or distributed for use on lawns and home gardens. Most biosolids composts are highly desirable products that are easy to store, transport and use.
To determine whether biosolids can be applied to a particular farm site, an evaluation of the site’s suitability is generally performed by the land applier. The evaluation examines water supplies, soil characteristics, slopes, vegetation, crop needs and the distances to surface and groundwater.
There are different rules for different classes of biosolids. Class A biosolids contain no detectible levels of pathogens. Class A biosolids that meet strict vector attraction reduction requirements and low levels metals contents, only have to apply for permits to ensure that these very tough standards have been met. Class B biosolids are treated but still contain detectible levels of pathogens. There are buffer requirements, public access, and crop harvesting restrictions for virtually all forms of Class B biosolids.
Nutrient management planning ensures that the appropriate quantity and quality of biosolids are land applied to the farmland. The biosolids application is specifically calculated to match the nutrient uptake requirements of the particular crop. Nutrient management technicians work with the farm community to assure proper land application and nutrient control.
Anyone who wants to use biosolids for land application must comply with all relevant federal and state regulations. In some cases a permit may be required.
A voluntary EMS is now being developed for biosolids by the National Biosolids Partnership (NBP). The NBP consists of members from the Association of Metropolitan Sewerage Agency, the Water Environment Federation, the U.S. Environmental Protection Agency (EPA) and other stakeholders including the general public. Those facilities who pledge to follow the EMS are agreeing to follow community-friendly practices in addition to being in compliance with applicable state and Federal regulations. Community friendly practices refer to the control of odor, traffic, noise, and dust as well as the management of nutrients. Those who pledge to follow the EMS will be subjected to audit by impartial independent third parties.
