From: Krista Wigginton <enveng@umich.edu>
To: Jane Williams <housing.director@umich.edu>
Date: July 10, 2018
Subject: RE: RE: Collaboration with Urine Diversion Research team for Renovations of Bursley Hall
Hello Jane,
Thank you for your response and for your questions. I’ve attempted to address your questions in the email below, as well as in the included attachments.
a. Why create fertilizer from urine?
First of all, urine contains nitrogen and phosphorus, the two primary components in fertilizers. In fact, though urine makes up just 1% of wastewater, urine contains approximately 80% of the nitrogen (N) and 45% of the phosphorus (P) in wastewater.○ Wastewater treatment plants are required to remove the N and P from wastewater before the effluent is discharged, because lakes, overexposed to nutrients, become polluted by excess algae, resulting in the die-off and decomposition of freshwater species from algae blooms. Blue-green algae is especially problematic because it may produce toxins that are harmful to humans and animals when ingested.○ The processes required to remove N and P from wastewater are often energy intensive and expensive for utilities.○
At the same time, fertilizer is also being produced through separate but also energy-intensive processes. Though nitrogen is abundant on the earth, transforming it into a form that is usable by plants is difficult. This is primarily done through the Haber-Bosch process, an energy-intensive process that requires fossil fuels, contributing to increased atmospheric carbon dioxide concentrations, and to climate change.○
Photo credit:
Rich Earth Institute
chm.bris.ac.uk ›
Accessing phosphorus for fertilizer use has environmental implications as well. Phosphorus in fertilizer generally comes from phosphate rock, which is in short supply. Some scientists believe that the earth’s phosphorus supply could be depleted in the next 50–100 years.○
Therefore, recovering N and P from a dilute source such as urine and recycling them on land makes economic and environmental sense.
- Create a fertilizer product with a lower environmental impact than conventional fertilizer production
- Reduce the energy use and expense of treating wastewater to remove nitrogen and phosphorus
- Improve water quality. According to a model of nutrient loads in the Lower Peninsula of Michigan, point sources such as wastewater treatment plants contribute 2% of total annual nitrogen loads in the region, and 10% of total annual phosphorus loads. Septic systems add an additional 6% of annual nitrogen loads and 19% of annual phosphorus.○ Though the proposed campus bathrooms would obviously not immediately lead to large reductions in these nutrient loads, they would be an opportunity to pilot technology that could eventually have a larger impact.
youtube.com ›
Photo credit:
Rich Earth Instituterichearthinstitute.org ›
b. What would be the responsibility of the maintenance team for the building?
The maintenance/janitorial team would simply be responsible for cleaning the bathrooms. They would not have any additional responsibilities—the research team would handle any other issues that arose. We assume that the maintenance team would be as willing to clean these technologies as they are traditional toilets and urinals.
c. Have urine-diverting toilets been installed elsewhere? Do they pose any maintenance issues unique to urine-diverting toilets? How do users react to these toilets?
Urine-diverting toilets have been installed on building and community scales in several locations. For example, the Hampton Roads Sanitation District, a public utility in Virginia, has experimented with urine-diverting facilities that pipe their urine to a separate holding tank, as we are proposing here.
Urine-diverting toilets have also been installed in large numbers in Durban, South Africa. These toilets were waterless urine-diverting models that were not connected to septic or sewer systems; rather urine was stored in holding tanks outside of the toilet, while solid waste is stored in vaults under the toilet bowl, to be emptied every six months.○ As a result of this, some toilet users felt that the urine-diverting toilets were a stepping stone on the way to a conventional flush toilet, which is seen as a “first class” toilet option.○ However, at the same time, these toilets provide an environmentally sustainable approach to sanitation. By using them in the United States context, it is possible that we can begin to shift the paradigm of an ideal toilet to one that is environmentally sustainable, such as the urine-diverting toilet.
Photo credit:
Carolina Gårdeforsd. Do they smell?
Urine-diverting toilets can be retrofitted with a vinegar-dosing mechanism that adds vinegar to the waste stream to keep the collected urine at a sufficiently low pH so that it doesn’t off-gas ammonia, which is what causes the urine smell. In other words—no, urine-diverting toilets do not smell any more than conventional toilets. The urine storage and treatment room also does not smell.
Sincerely,
Krista Wigginton
Professor of Environmental Engineering