A non-partisan, neutral perspective supporting diversity in the color of water

Tuesday, September 27, 2011

Purplewater Yields More "Green" Problems

School has started again in Oregon, and it appears that the global economy has been good to the academies with nearly all of the institutions under the Oregon Universities System reporting record enrollments!

Seriously, back to business. I am teaching a class titled Sustainability for the Common Good with 300 friends enrolled. The Rainbow Water Coalition is providing an abundance of material to discuss, and one item I have been saving for awhile given the upcoming discussions on carbon footprints in the class is the issue of greenhouse gas emissions and wastewater treatment.

No, not what you might think. Rather, this article on new research provides more fodder for increased water reuse and integrating greywater into that equation. Amy Townsend-Small, Diane E. Pataki, Linda Y. Tseng, Cheng-Yao Tsai, Diego Rosso (2011) examined Nitrous Oxide Emissions from Wastewater Treatment and Water Reclamation Plants in Southern California in the Journal of Environment Quality (40 (5): 1542 DOI: 10.2134/jeq2011.0059) and found the following:

"Wastewater reuse for irrigation, otherwise known as 'showers to flowers', potentially reduces overall freshwater consumption in southern California, which is threatened by dwindling supply and a growing population," Townsend-Small said.

However, she and her co-authors found that the wastewater recycling plant emitted about three times more nitrous oxide than the traditional treatment, when all factors are included. The researchers' data indicate that dense populations of nitrifying and denitrifying bacteria in the wastewater recycling plant were the cause of these high nitrous oxide emissions. They also did preliminary calculations on the impact of wastewater recycling plants on nitrous oxide emissions in southern California.

"Because the Los Angeles area is so heavily urbanized, our calculations indicate that nitrous oxide emissions from wastewater treatment and recycling are several orders of magnitude larger than agricultural nitrous oxide emissions in the region," Townsend-Small said.

Despite the production of nitrous oxide, the authors conclude that -- taken in context -- wastewater recycling is still a good idea.

But California-based greywater experts Oasis Design, Greywater Corps and Greywater Action already knew this. Score another one less greenhouse gas for simply being careful with greywater and reusing at the point of use. 

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