Usually, wastewater treatment plants are lauded as defenders of the environment. A new study suggests that they do more harm to the planet than previously believed.
When the Intergovernmental Panel on Climate Change (IPCC) estimated global carbon dioxide emissions, it failed to include accurate emission estimates from wastewater, according to a press release from the American Chemical Society.
“Although it does take into account greenhouse gases methane and nitrous oxide, the IPCC model assumes that wastewater largely contains and releases carbon from non-petroleum sources — for example, human waste,” per the release. “However, studies have shown that relevant amounts of petroleum products, such as synthetic chemicals from detergents, wash into wastewater and can eventually add to total greenhouse gas emissions.”
One such study, published in the journal Environmental Science & Technology, looked at the fossil-related carbon content in municipal and industrial wastewaters during the treatment process and concluded that total greenhouse gas emission could be 12 to 23 percent higher than estimates that only account for methane and nitrous oxide.
“Analyzing radiocarbon at different treatment points within municipal WRRFs [water resource recovery facilities], we verified that the fossil content could amount to 28 percent in primary influent and showed varying distribution leaving different unit operations,” the researchers wrote in the study’s abstract. “With such a considerable impact, CO2 should be analyzed for each WRRF and not omitted from [greenhouse gas] accounting.”
It’s critical that the most relevant and up-to-date information is incorporated into the IPCC’s estimates, as the agency is responsible for providing international policymakers with assessments on climate change, as it did before the 2015 conference that lead to the Paris Agreement.
“With their findings, the researchers are recommending the addition of wastewater treatment plants to the climate action plans of the government to curb emissions from the source,” reported Nature World News.
The study, conducted by researchers from Colgate University; University of California, Irvine; and others, also found that wastewater sludge presents the chance to make wastewater treatment plants more environmentally friendly.
“Furthermore, the researchers found that treating wastewater sludge could offer an opportunity to reduce the fossil carbon emissions from treatment plants, noting that on-site carbon sequestration run on renewable energy could also lower these plants’ impact,” Nature World News reported.
Image credit: "Greenhouse Gases" Faizan Shaharyar © 2008, used under an Attribution 2.0 Generic license: https://creativecommons.org/licenses/by/2.0/