Identification of Preferential Paths of Fossil Carbon within Water Resource Recovery Facilities via Radiocarbon Analysis.
The Intergovernmental Panel on Climate Change (IPCC) reported that all carbon dioxide (CO2) emissions generated by water resource recovery facilities (WRRFs) during treatment are modern, based on available literature. Therefore, such emissions were omitted from IPCC's greenhouse gas (GHG) accounting procedures. However, a fraction of wastewater's carbon is fossil in origin. We hypothesized that since the fossil carbon entering municipal WRRFs is mostly from soaps and detergents as dissolved organic matter, its fate can be selectively determined during the universally applied separation treatment processes. Analyzing radiocarbon at different treatment points within municipal WRRFs, we verified that the fossil content could amount to 28% in primary influent and showed varying distribution leaving different unit operations. We recorded the highest proportion of fossil carbon leaving the secondary treatment as off-gas and as solid sludge (averaged 2.08 kg fossil-CO2-emission-potential m-3wastewater treated). By including fossil CO2, total GHG emission in municipal WRRFs increased 13%, and 23% if an on-site energy recovery system exists although much of the postdigestion fossil carbon remained in biosolids rather than in biogas, offering yet another carbon sequestration opportunity during biosolids handling. In comparison, fossil carbon contribution to GHG emission can span from negligible to substantial in different types of industrial WRRFs. With such a considerable impact, CO2should be analyzed for each WRRF and not omitted from GHG accounting.
Environmental Studies Program & Department of Physics and Astronomy, Colgate University , 13 Oak Drive, Hamilton, New York 13346, United States.
Linda Y
LY
Tseng
Alice K
AK
Robinson
Xiaying
X
Zhang
Xiaomei
X
Xu
John
J
Southon
Faculty of Veterinary and Agricultural Sciences, The University of Melbourne , Dookie College, VIC 3647, Australia.
Andrew J
AJ
Hamilton
Reza
R
Sobhani
Civil and Environmental Engineering Department, University of California , Los Angeles, California 90095-1593, United States.
Michael K
MK
Stenstrom
Diego
D
Rosso
D002244:Carbon; D002245:Carbon Dioxide; D057231:Climate Change; D005580:Fossils; D017752:Greenhouse Effect; D012722:Sewage; D062066:Water Resources
D012722:Sewage; D002245:Carbon Dioxide; D002244:Carbon