counties where biosolids were applied in 2007, showing tons of nitrogen per county
Source: Virginia Tech, Virginia County-Level Historical Trends
counties where biosolids were applied in 2007, showing tons of nitrogen per county
Source: Virginia Tech, Virginia County-Level Historical Trends
Humans and animals produce biosolids. Though dog owners know the joys of collecting bisolids after walking the pet, most human biosolids are just flushed down a toilet. In some cases, however, what we flush will be recycled to farmland or forests - after processing.
All waste ends up in either the air, the water, or in the ground. In rural areas, waste goes through septic tanks and leach fields. Organic materials are converted by bacteria into carbon dioxide and nutrients in the soil, and humans never see any residue unless the septic tank is cleaned out.
In Tidewater cities/counties affected by the Chesapeake Bay regulations in Virginia, septic tanks must be pumped out every 5 years to remove any grease, clogs, and non-organic solids in the tank (such as cigarette filters or plastic flushed down the toilet). Preventive cleaning helps ensure septic systems work as designed. When a septic system fails, raw sewage can reach the surface of a leach field and contaminate lawns, or flow underground to contaminate nearby creeks.
"Honey wagons" that pump out septic tanks carry the remaining solids (septage) from the underground concrete vaults to a sewer system, and the solids then flow down the pipe to a watewater treatment plant. There, the inorganic solids are screened out and ultimately incinerated or buried underground at a landfill. Most organic solids are converted by bacteria into gas (especially N2 and CO2) and vented into the atmosphere, before the "reclaimed" wastewater is dumped at the end of the process into a nearby creek or river.
However, some organic grease/scum accumulates at the top of the settling and clarifying tanks at wastewater treatment plants, while sludge accumulates at the bottom. The solid residue can be buried in a landfill, but that is expensive. Sewage sludge can be incinerated so a smaller volume of ash can buried in a landfill, but that is still expensive - and buring sewage sludge generates emissions that may disturb people living nearby.
In Arlington County, the wastewater treatment plant on Four Mile Run near Reagan National Airport ended up with politically-influential and wealthy neighbors living in high value homes on Arlington Ridge. The residents objected to the incineration of slude, with presumed impacts on local air quality, and claimed the process could lower property values.
In response, Arlington abandoned incineration of the large volume of sludge produced in primary and secondary treatment. The county has continued to incinerate the inorganic solids screened out of the wastewater at the start of the process, shipping it to the Alexandria/Arlington Waste-to-Energy Facility. Arlington tore down the incinerator smokestack to make clear that the sludge would never be burned again.
The county had no landfill nearby for sludge disposal. Its solution was to treat the sludge, converting it into "Class A biosolids" that posed no health risk. Trucks now haul away the biosolids for use as fertilizer and as a soil amendment, increasing the percentage of organic matter in agricultural and forest soils.
Arlington is fully urbanized; there are no large farms nearby where the residue could be disposed. The county uses a contractor to obtain permission for disposal elsewhere, and to transport the "once waste, now nutrient" material to farms and forests. There, the biosolids are applied on pastures or forest soils. Human waste from people in the sewershed of the Arlington plant is recycled into grass or trees, as plants and organisms in the soil incorporate nutrients and trace elements in the biosolids.
Richmond's biosolids are applied on farms in Amelia, Buckingham, Caroline, Charles City, Charlotte, Cumberland, Hanover, King William, and Powhatan counties
Source: City of Richmond, Biosolids
Under the Environmental Protection Agency's regulations (the 503 Rule), there are two classes of biosolids. To create Class A biosolids, sludge is treated to eliminate nearly all disease-causing organisms (pathogens) and to minimize heavy metals. Class A biosolids can be upgraded to Exceptional Quality (EQ) biosolids, if processed (typically by heat of adding lime to increase pH) so birds, flies, and other vectors would not be attracted to the material. Class A biosolids are handled like commercial fertilizers when spread on farms, while EQ biosolids can be bagged and sold to homeowners for use without any special restrictions.
Class B biosolids may retain detectable levels of pathogens and metals. The Virginia Department of Environmental Quality (DEQ) requires a site permit before authorizing application of Class B biosolids, and limits the application of Class B biosolids near streams/sinkholes and on steep slopes.1
About 60 percent of sewage sludge in the United States was used for land application in 2002. In Virginia, biosolids were applied to about 50,000 acres in 2006. By comparison, untreated animal manure was applied to nearly 400,000 acres.2Your last hamburger may have come from a cow that grazed on grass that was fertilized by biosolds from a Virginia wastewater treatment plant. The newspaper you last read may have been created from pulp from a pine forest that was fertilized by biosolids. The toilet paper you last used could have come from such a forest, making the recycling cycle even more obvious...
Modern urban living emphasizes cleanliness, and antiseptics fill our medicine cabinets and cleaning closets. As a result, many Virginians are ignorant of how their waste is processed and have an "out of sight, out of mind" after we flush. It is typical to get a squeamish reaction when discussing how human waste is applied to farm fields. If the farm field is nearby, the reaction is often much stronger than just "Eeew... gross."Virginia wastewater treatment plants do not ship their biosolids to Ohio or Kansas. To reduce costs, urban wastewater treatment plants haul their biosolids to nearby farms. In many suburbanizing areas, the nearest farms are getting surrounded by modern subdivisions. Houses near the farms are filled with squeamish voters who are unfamiliar/uncomfortable with the idea that human waste, no matter how safe, is going to be dumped nearby.
Land application of biosolids requires various permits, and in many cases the approval process is controversial. Counties have tried to pass local ordinances, often in the guise of zoning for land use control, that limit where biosolids could be applied.
Federal and state regulations supercede local ordinances, and the General Assembly consolidated state permitting into the Department of Environmental Quality starting in 2008 (shifting responsibilities from the Virginia Department of Health). Virginia counties may impose fees and require additional testing/monitoring of land application sites, but may not block land application.
biosolids application starts with hauling the nutrients to a site, then spreading them
Source: Virginia Cooperative Extension, Agricultural Land Application of Biosolids in Virginia: Risks and Concerns
In addition to biosolids generated at wastewater treatment plants from human sewage, "Industrial sludge" is produced from waste at animal processing plants and paper mills.
In 2014, the State Water Control Board was asked by Synagro Technologies to approve use of industrial sludge generated by the Tyson Foods poultry processing plant in Hanover County, the RockTenn Co. paper mill at West Point, and the Smithfield Foods pork processing plant in Isle of Wight County. The application would occur on 16,000 acres in King William, King & Queen, New Kent, Goochland, Hanover, Prince George and Surry counties.3
Acres Permitted for Biosolids Applications, by County, 2004 (wastewater treatment plants in southwestern counties were not disposing of biosolids by land application)
Source: Joint Legislative Audit and Review Commission, Review of Land Application of Biosolids in Virginia (House Document No. 89, 2005)