Biosolids
Biosolids are nutrient-rich organic materials produced through the treatment of sewage in wastewater treatment plants. After extensive sanitization and dewatering processes, these treated materials can be utilized as fertilizers in agriculture, helping to grow various crops and enrich the soil. This recycling of waste transforms what would otherwise be discarded into a valuable resource, effectively supporting sustainable farming practices. However, the use of biosolids does raise some safety concerns, particularly regarding potential contaminants that may remain after treatment, such as heavy metals and pharmaceuticals. While proponents argue that regulatory frameworks ensure the safety of biosolids for use in food production, critics caution that ongoing research may reveal new risks associated with these materials. The historical context of waste management shows a progression from untreated disposal methods, which led to health crises, to modern treatment systems aimed at reducing pathogens and harmful substances. As biosolids continue to be integrated into agricultural and land rehabilitation practices, the debate surrounding their safety and efficacy remains a topic of interest and concern for many communities.
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Biosolids
Biosolids are organic material that is produced by treating sewage in a wastewater treatment plant. After sanitizing the material and removing much of the water, the resulting nutrient-rich material is used as fertilizer. Biosolids are a renewable resource and make use of material that is literally waste to help grow various crops. Biosolids are treated to remove dangerous pathogens, or substances that can cause disease. However, some people raise concerns about the safety of using biosolids on food crops.
Background
The oldest known reference to dealing with human waste is in the Book of Deuteronomy in the Bible, in which a passage describes digging holes and burying waste away from camps. The ancient Romans built rooms that had rows of benches with openings over pits where people could relieve themselves; the waste fell below and was carried away by the used water from the Roman baths. Some private homes in ancient Rome also had bathrooms connected to a primitive sewer system to carry the waste away.
People also used latrines or outhouse-type bathrooms for many thousands of years that put the waste directly into pits in the ground. When people lived in areas where pits were not practical, they often used chamber pots, which were used in the bedroom, or chamber, and emptied into streets or other nearby communal areas. In any case, untreated human waste was most often placed directly into the environment.
Untreated human waste can carry many diseases. It can also provide breeding grounds for many other diseases. Until the 1800s, this led to many outbreaks of illnesses such as cholera and typhoid fever. This was especially prevalent in big cities. In 1854, British physician John Snow documented that a community water source contaminated by sewage had caused a serious cholera epidemic in London. Snow’s work generated support for sewage collection and transport systems. His research paved the way for systems beginning in the nineteenth century that treated the waste to remove disease-causing pathogens and other harmful materials before it was discharged into the environment.
Overview
Biosolids are the result of treating raw sewage sludge from homes and businesses. The material is called sludge until it is treated. Sewage sludge is about 3 percent solid material and 97 percent liquids. The material undergoes several forms of treatment before it can be classified as biosolids.
First, raw sewage sludge is deposited into the sewer system. As the sludge moves through the system and the wastewater treatment plant, solid trash is strained out. The sludge continues through a system of tanks that allow more solid material to settle out of the liquid. Gravity does a lot of this work and is assisted by microbes, or small organisms that help with fermentation that removes sugars and releases other substances.
The fermentation process also generates heat. The heat and the microbes help to “digest” the solids. Along the way, the increasingly solid material is treated to kill any dangerous organisms that may be in the waste. The material is also treated to remove many other hazardous materials, such as cleaning chemicals and soaps, medications that may have been flushed, and other non-organic substances. Finally, the material is dewatered using devices that work much like a salad spinner or washing machine to spin away excess water. This water may also be treated and used for non-drinking purposes, such as watering crops or industrial purposes. Finally, the material that is now at least 15 to 90 percent solid is hauled away for agricultural use.
The fully treated biosolids contain a variety of micronutrients and macronutrients. These can include nitrogen, phosphorous, potassium, copper, calcium, magnesium, zinc, or iron. Depending on their final intended use, biosolids may also contain small amounts of substances known to be hazardous. These include mercury, lead, arsenic, cadmium, and others. The amounts of these substances and any others that might be a danger to humans, animals, or the environment are regulated by government authorities in most countries.
One of the main uses for biosolids is to enrich and treat agricultural land. The organic material in the biosolids serves as a fertilizer to help with plant growth. Biosolids can also be used to help restore and rehabilitate forest lands and residential and park lands. Other applications include using it as a base material for roads and in the manufacture of bricks and glass. Some work has also been done to develop biofuels that use biosolids.
Biosolids are subjected to regulations of various strictness, depending on the laws in different countries; local laws may add additional precautions. Proponents of using biosolids say that these laws provide sufficient protection to humans, animals, and the environment. They point to the benefits of using biosolids. Biosolids contain many beneficial organic substances that help enrich soil; they help hold carbon in the soil; and they treat and recycle material that would otherwise be placed in a landfill, possibly without treatment, or burned, which could cause air pollution.
However, some people are concerned that the regulations are not sufficient to protect against potential risks presented by biosolids use. They raise questions about the safety of having any level of contaminants added to land that will ultimately provide food and filter drinking water. They also argue that human understanding of contaminants continually evolves, and things that are believed to be safe now may be found to be unsafe in the future. Some also point to the fact that the very process that creates the biosolids results in concentrating many contaminants. Opponents urge caution in using biosolids for agricultural purposes and suggest avoiding food that is grown using them.
Bibliography
Epp, Lidia. “The History of Sludge for Agricultural Application.” Mother Earth News, 8 Feb. 2016, www.motherearthnews.com/nature-and-environment/the-history-of-sludge-for-agricutural-application-zbcz1602. Accessed 27 Oct. 2018.
“Frequent Questions about Biosolids.” US Environmental Protection Agency, www.epa.gov/biosolids/frequent-questions-about-biosolids. Accessed 27 Oct. 2018.
“History of Sewage Disposal.” Maine Center for Disease Control and Prevention, 2013, https://www1.maine.gov/dhhs/mecdc/environmental-health/plumb/documents/training/2013/history‗of‗sewage‗disposal.pdf. Accessed 27 Oct. 2018.
Pozzebon, Elizabeth A. and Lars Seifert. "Emerging Environmental Health Risks Associated with the Land Application of Biosolids: A Scoping Review." Environmental Health, vol. 22, no. 57, 21 Aug. 2023, doi.org/10.1186/s12940-023-01008-4. Accessed 6 Nov. 2024.
“What Are Biosolids?” Australian and New Zealand Biosolids Partnership, www.biosolids.com.au/info/what-are-biosolids/. Accessed 27 Oct. 2018.
“What Are Biosolids?” Nebraska Extension in Lancaster County, lancaster.unl.edu/enviro/biosolids/whatare1.shtml. Accessed 27 Oct. 2018.
“What Are Biosolids?” Northwest Biosolids, nwbiosolids.org/what-are-biosolids-overview. Accessed 27 Oct. 2018.
“What Are Biosolids, How Are They Used, and Are They Safe?” Michigan Department of Environmental Quality, www.michigan.gov/documents/deq/deq-ess-faq-water-wb-septagebiosolids-whatarethey‗206712‗7.pdf. Accessed 27 Oct. 2018.
Yorgey, Georgine. “Biosolids – Understanding Benefits and Risks.” Washington State University Center for Sustaining Agriculture and Natural Resources, 16 Aug. 2016, csanr.wsu.edu/biosolids-benefits-risks/. Accessed 27 Oct. 2018.