University of Cincinnati, Department of Geology, Cincinnati, OH 45221, United States.
University of Cincinnati, Department of Geology, Cincinnati, OH 45221, United States; University of Cincinnati, Department of Geography, Cincinnati, OH 45221, United States.
Sci Total Environ. 2015 Feb 1;505:1166-73. doi: 10.1016/j.scitotenv.2014.10.060. Epub 2014 Nov 14.
Water reclamation has the potential to reduce water supply demands from aquifers and more energy-intensive water production methods (e.g., seawater desalination). However, water reclamation via biological nitrification-denitrification is also associated with the direct emission of the greenhouse gases (GHGs) CO₂, N₂O, and CH₄. We quantified these direct emissions from the nitrification-denitrification reactors of a water reclamation plant in Southern California, and measured the (14)C content of the CO₂ to distinguish between short- and long-lived carbon. The total emissions were 1.5 (±0.2) g-fossil CO₂ m(-3) of wastewater treated, 0.5 (±0.1) g-CO₂-eq of CH₄ m(-3), and 1.8 (±0.5) g-CO₂-eq of N₂O m(-3), for a total of 3.9 (±0.5) g-CO₂-eqm(-3). This demonstrated that water reclamation can be a source of GHGs from long lived carbon, and thus a candidate for GHG reduction credit. From the (14)C measurements, we found that between 11.4% and 15.1% of the CO₂ directly emitted was derived from fossil sources, which challenges past assumptions that the direct CO₂ emissions from water reclamation contain only modern carbon. A comparison of our direct emission measurements with estimates of indirect emissions from several water production methods, however, showed that the direct emissions from water reclamation constitute only a small fraction of the plant's total GHG footprint.
污水再生具有减少含水层供水需求和更节能的水生产方法（例如海水淡化）的潜力。然而，通过生物硝化-反硝化进行的污水再生也与温室气体 (GHG) CO₂、N₂O 和 CH₄ 的直接排放有关。我们量化了南加州一家污水再生厂的硝化-反硝化反应器中的这些直接排放，并测量了 CO₂ 的 (14)C 含量，以区分短寿命和长寿命碳。总排放量为 1.5（±0.2）g 化石 CO₂ m(-3) 处理的废水，0.5（±0.1）g-CO₂-eq 的 CH₄ m(-3)，和 1.8（±0.5）g-CO₂-eq 的 N₂O m(-3)，总计 3.9（±0.5）g-CO₂-eqm(-3)。这表明污水再生可以成为长寿命碳温室气体的来源，因此是温室气体减排信用的候选者。通过 (14)C 测量，我们发现直接排放的 CO₂ 中有 11.4%至 15.1%来自化石来源，这挑战了过去的假设，即污水再生的直接 CO₂ 排放仅包含现代碳。然而，将我们的直接排放测量值与几种水生产方法的间接排放估计值进行比较表明，污水再生的直接排放仅占工厂温室气体总足迹的一小部分。
