After we flush, our 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 we never see it again unless we clean out the septic tank.
In the Tidewater cities/counties affected by the Chesapeake Bay regulations in Virginia, septic tanks must be cleaned 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 solids to a sewage system, and send it on down the pipe to a watewater treatment plant. At wastewater treatment plants, 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, or into harmless dissolved molecules that are dumped at the end of the processing into a nearby creek or river.
However, some organic sludge and grease accumulates at the top and bottom of the tanks at wastewater treatment plants. The biosolids can be buried in a landfill, but that's expensive. Biosolids can be incinerated so a smaller volume of ash can buried in a landfill, but that's still expensive. In Arlington County, neighbors objected to the incineration and presumed impacts on local air quality, claiming property values would be depressed in the neighborhood. Arlington abandoned incineration - but lacked any landfill for disposal.
The solution: treat the biosolids so they pose no health risk, then use them as fertilizer. Arlington is fully urbanized, so the county has a contractor who transports the "once waste, now nutrient" material to farms and forests. There, the biosolids are applied on pastures or forest soils. Plants and organisms in the soil use the biosolids as food, and the human waste is recycled into grass or trees.
About 60 percent of sewage sludge in the United States was used for land application in 2002,1 In Virginia, biosolids were applied to about 50,000 acres in 2004 and 2005.2 Your 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 Department of Health). Virginia counties may impose fees and require additional testing/monitoring of land application sites, but may not block land application.