Phantastic Phosphorus

As a child, one of my favorite stories was Isaac Asimov’s Fantastic Voyage, which he adapted from the 1966 movie by 20th Century Fox Films (versus the other way around.) Best known for his science fiction, Asimov also wrote about science, including an essay about phosphorus entitled “Life’s Bottleneck.” Asimov describes how phosphorus is an essential chemical contained in all living organisms. “[L]ife can multiply until all the phosphorus is gone, and then there is an inexorable halt which nothing can prevent,” he wrote. “We may be able to substitute nuclear power for coal, and plastics for wood, and yeast for meat, and friendliness for isolation—but for phosphorus there is neither substitute nor replacement.”

As far back as 1938, President Franklin Roosevelt warned Congress about potential phosphorous shortages. Nothing was done. And now, it is estimated that the earth will be exhausted of phosphorus within 100 years. Where is it going? It’s running off farm fields through soil erosion and runoff, and down swirling toilets, through human waste. But we can recover this precious substance through wastewater treatment plant biosolids and extract it from side-stream processes, such as Ostara.

When Phosphorous is Not Viewed as Precious

With eutrophication of waterways and hypoxic zones growing in the Gulf of Mexico and Chesapeake Bay, the US EPA is targeting municipal wastewater treatment plants as a point source dis-charger of phosphorus. Communities within the Great Lakes Initiative have had effluent phosphorus limits of 1.0 mg/L for some time, but stricter limits have been proposed in WI, as low as 0.07 mg/L. Very recently, in Connecticut regulators have proposed limits of 0.2 mg/L phosphorus that officials say will cost tens of millions in treatment plant upgrades.

Just recently the EPA created a website to monitor nutrient sources. It is generally accepted that point sources, including treatment plants, account for about 30-40% but stormwater runoff and agriculture accounts for the largest fraction. Combined with erosion and loss of topsoil, our agriculture industry relies on more and more fertilizer. So the irony is that the wastewater treatment plants are targeted as sources of phosphorus because of their effluent, but they can also be a solution for returning nutrients to the land and standing in for fertilizer.

Biosolids from Treatment Plants Can Provide Beneficial Phosphorous

The benefits of land applied biosolids were recently substantiated by researchers in Washington[1]. Biosolids improve moisture holding capacity and tilth of soil, and so nutrients like nitrogen and phosphorus are better retained and more readily available to plants. Unfortunately, the lack of knowledge about the efficacy of biosolids and the perception that they are toxic means that only about half of all biosolids produced in the US are land applied. Yes, biosolids contain metals, but with EPA 503 regulations and industrial pretreatment requirements, heavy metals in biosolids should not be an issue.

Unfortunately, many communities landfill biosolids as the simplest answer to its management. But with phosphorus resources rapidly diminishing, our thought leaders should begin advancing the idea of land application to optimize this precious element. Wastewater treatment plants should continue to reduce nutrients in discharges but they can also provide nutrients for the agricultural industry. What factors are standing in the way and what do we do about them?

[1] Brown, Sally, Kate Kurtz, Andy Bary, and Craig Cogger. 2011. “Quantifying Benefits Associated with Land Application of Organic Residuals in Washington State.” Environmental Science & Technology. Vol. 17 (7), pp. 7451-7458.