From The Editor | May 22, 2014

'Peecycle' Please: Will Urine Separation For Nutrient Recovery Take Off?


By Kevin Westerling


Is it feasible to separate nutrient-rich urine before it reaches the wastewater treatment plant?

It might be a pipe dream, but researchers are investigating the potential of keeping urine separate from the rest of the wastewater we humans produce. The urine would be diverted as close to the source as possible — at the toilet, via dedicated plumbing — and then stored, treated, and converted into fertilizer. While it’s not realistic to expect urine-diverting (UD) toilets in every home, they could reasonably be installed in high-occupancy buildings.

Fertile Ground For Research

The goal is not only to make fertilizer, but to decrease the amount of nutrient removal required at the wastewater treatment plant (WWTP) — or the “water resource recovery facility” (WRRF), which is the term the Water Environment Research Federation (WERF) prefers. The new moniker certainly fits in this case, as the WERF-sponsored research project is right in line with its mission to capture and utilize the resources that are abundant in wastewater and the treatment process.

Urine has been shown to be an effective fertilizer, densely packed with nutrients such as nitrogen, phosphorus, and potassium. It can also be readily land-applied in its natural, liquid state, as opposed to undergoing the typical process of turning sewage sludge into dry fertilizer. Another benefit is that urine doesn’t contain the bacteria inherent in biosolids, such as salmonella and E. coli. In fact, urine is practically sterile as it leaves the body.

Impact On Water Quality

From an environmental standpoint, this tactic could lessen the nutrient loads deposited in waterways, which are being subject to total maximum daily load (TMDL) restrictions to avoid toxic blue-green algae growth. Non-point sources such as agricultural runoff would still be major contributors of nutrients, but the reduced nutrient levels of sewage coming into the plant should, at worst, make life easier for plant operators to comply with effluent limits and TMDLs. With less coming in, current nutrient removal techniques could bring effluent concentrations to new lows.

In addition to nutrients, urine also stores a range of pharmaceuticals (and illicit drugs) that are passed through the body. These compounds are difficult for water and wastewater facilities to treat, and can ultimately find their way into drinking water. Segregating these potentially dangerous contaminants could better protect consumer health, but that has yet to be determined. It is, however, part of the study.

Research Objectives

WERF identifies four key research objectives:

  1. Determine how urine pretreatments impact pharmaceutical/biological contaminant concentrations.
  2. Understand the fate of nutrients and contaminants once source-separated urine is land-applied.
  3. Evaluate the effectiveness of urine fertilizer.
  4. Develop design and permitting guidelines for high-occupancy buildings to address the practical challenges of urine separation and collection.

Plumbing configuration for a urine-diverting toilet. Credit: "UD flush toilet (company: Dubbletten)," Sustainable sanitation © 2007, used under an Attribution-NoDerivs 2.0 Generic license:

The University of Michigan, in cooperation with WERF, is carrying out the study — the first project for the U.S. EPA-funded National Center for Resource Recovery and Nutrient Management. Two full-scale demonstrations, at Virginia’s Hampton Roads Sanitation District and Vermont’s Rich Earth Institute, are also being conducted as part of the research.

It will be fascinating to see whether this idea is a true pipe dream, or a pipe dream come true.

What do you think about the project’s feasibility? Share your thoughts in the comments section below…

Image 1 credit: "Ceramic UDDT and wash bowl in private household," Sustainable sanitation © 2006, used under an Attribution-NoDerivs 2.0 Generic license: