Alternative Uses for Sewage Sludge
The Ocean Dumping Ban signed into law in 1988 outlawed the dumping of sewage sludge into the ocean after December 31, 1991. At the same time that municipalities had to come up with alternative methods to dispose of the highly concentrated waste product solids that remain after water extraction, many of them were also confronted with growing populations helping to create increasing amounts of it to dispose of. Landfilling, incineration, and land application became the most common disposal methods, but with increasing concerns over the safety of those methods, researchers around the world have been exploring other ways to manage sludge. In this section, you’ll find samples of that research. Some of the most promising has looked at sludge as a renewable energy source. The renewable part comes as no surprise, but the fact that sludge can be used in a variety of ways to generate energy and fuel may. As exciting a prospect as that may be at a time when we feel an increasing urgency to find alternative energy sources, it’s important to note that this is an emerging technology and that many of the concerning heavy metals, pathogens, and other pollutants found in sludge still need to be addressed. It’s also fair to say that there will be no “one size fits all” solution; no one method will work for every municipality. Finally, it’s critically important to approach the management of sludge in a deliberate, thoughtful manner, as in the following example from Sweden.
Sweden’s Sustainable Waste Management System The Swedish system of Sustainable Waste Management is highly regarded around the globe. As the Swedes put it, “Waste and refuse are resources in the wrong place,” and so they’ve spent decades finding ways to make the most of sewage sludge. According to Stephen J. Salter, an engineer from Victoria, British Columbia, who has written extensively about his travels in Sweden to study their methods, sewage sludge is used to fuel vehicles and heat homes. But it’s not just that the Swedes have turned sludge into energy that makes their system so special. It’s that they’ve developed an integrated approach to dealing with waste that sets them apart from so many other nations, including the United States. In “Powered by the People: Victoria Engineer Discovers Swedes View Sewage as a Valuable Resource” from Victoria’s Times Colonist newspaper, Salter says, “I went [to Sweden] expecting to see really cutting-edge technology, and instead what I found was a lot of common sense applied to community planning,” he said. “Instead of just looking at liquid waste separately, they look at liquid waste, solid waste, energy, transportation and environment. They look at all of those five areas as one plan.”
We can learn a lot from the Swedes.
- Their integrated approach to managing waste and converting it into a resource is one that has evolved over decades. Their first treatment plants were built in the 1930s. Over time, they have upgraded to tertiary plants, meaning that physical, chemical, and biological methods are used in the treatment process.
- Municipalities have control over their waste management systems, as each city owns its own companies for managing sewage, solid waste, energy and transportation.
- Treatment plants are often built within communities, even under an apartment building in one case, so that residents are mindful that the waste we generate doesn’t just go away when we flush the toilet.
- The entire matter of waste management is carefully thought out, so that resources from waste are used to best advantage in each community.
- All of their efforts have resulted in reduced costs for sewage treatment per household , whereas costs in the U.S. continue to rise dramatically and don’t take into account the cost of rebuilding the crumbling sewage infrastructure . By the way, the Swedes also get subsidies for filling their tanks with bio-fuel.
As a means of making use of waste, applying sewage sludge to land as a fertilizer isn’t a terrible idea. It’s an idea carried out in a terrible way in this country. In fact, it’s a great example of how not to manage sewage sludge. In order to use sewage sludge safely as a fertilizer, you would need to know where it’s from, what’s in it, and how to clean it so it doesn’t cause contamination. When sludge is imported from other municipalities and even states, when it’s not sufficiently tested to know what it contains, and when adequate resources aren’t dedicated to cleaning it, it’s impossible to safeguard the soil and the food supply. Instead of making our standards and testing requirements more stringent over time, we have made ours less so. And since “sewage contains 10 times the energy needed to treat it ,” we may be overlooking more efficient ways of using even the cleanest sludge.
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