[audio:http://wamcradio.org/EarthWise/wp-content/uploads/2012/03/EW-05-11-12-Sewage.mp3|titles=EW 05-11-12 Sewage]
Modern society produces a lot of wastewater. Households, hospitals, businesses, and institutions discharge their dirty water into sewers. Each month, we allow every industry in the U.S. to discharge 33 pounds of hazardous waste. Sewage treatment plants are tasked with removing pathogens, metals, and an array of chemical compounds.
Sewage sludge is a byproduct of wastewater treatment. Because sludge concentrates toxins, it’s a pollutant under the Federal Clean Water Act. Up until 1992, when the Ocean Dumping Ban Act took effect, sludge was routinely disposed of in the ocean.
Sludge disposal is now limited to incineration, landfill burial, or land application. When sewage sludge is applied to land it is called a bio-solid, and has to meet Environmental Protection Agency’s standards.
Bio-solids are a way for municipalities to recycle sludge into inexpensive fertilizer. Each year millions of tons of bio-solids are spread on parks, golf courses, residential lawns, crops, and reclaimed land. This begs the question – are bio-solids safe? The jury is out.
A National Academies of Sciences report highlighted a number of concerns, among them the persistence of lead, PCBs, pharmaceuticals, and antibiotic resistant superbugs—which can wind up polluting wells, sickening livestock, and contaminating soil. Most major food suppliers, like Heinz and Del Monte, won’t take produce grown on land treated with bio-solids.
Recycling mixed sewage as fertilizer is a tenuous concept that, at a minimum, warrants ongoing scientific scrutiny and public transparency.
Photo, taken on October 11, 2011 using a Nikon D300S, courtesy of Susana Secretariat via Flickr.