Department of Forest and Ecosystem Science, The University of Melbourne, 500, Yarra Boulevard, Richmond, VIC 3121, Australia.
Department of Resource Management and Geography, The University of Melbourne, 500, Yarra Boulevard, Richmond, VIC 3121, Australia.
J Environ Manage. 2014 Oct 1;143:34-43. doi: 10.1016/j.jenvman.2014.04.016. Epub 2014 May 15.
The wastewater treatment process generates large amounts of sewage sludge that are dried and then often stored in biosolid stockpiles in treatment plants. Because the biosolids are rich in decomposable organic matter they could be a significant source for greenhouse gas (GHG) emissions, yet there are no direct measurements of GHG from stockpiles. We therefore measured the direct emissions of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) on a monthly basis from three different age classes of biosolid stockpiles at the Western Treatment Plant (WTP), Melbourne, Australia, from December 2009 to November 2011 using manual static chambers. All biosolid stockpiles were a significant point source for CH4 and N2O emissions. The youngest biosolids (<1 year old) had the greatest CH4 and N2O emissions of 60.2 kg of CO2-e per Mg of biosolid per year. Stockpiles that were between 1 and 3 years old emitted less overall GHG (∼29 kg CO2-e Mg(-1) yr(-1)) and the oldest stockpiles emitted the least GHG (∼10 kg CO2-e Mg(-1) yr(-1)). Methane emissions were negligible in all stockpiles but the relative contribution of N2O and CO2 changed with stockpile age. The youngest stockpile emitted two thirds of the GHG emission as N2O, while the 1-3 year old stockpile emitted an equal amount of N2O and CO2 and in the oldest stockpile CO2 emissions dominated. We did not detect any seasonal variability of GHG emissions and did not observe a correlation between GHG flux and environmental variables such as biosolid temperature, moisture content or nitrate and ammonium concentration. We also modeled CH4 emissions based on a first order decay model and the model based estimated annual CH4 emissions were higher as compared to the direct field based estimated annual CH4 emissions. Our results indicate that labile organic material in stockpiles is decomposed over time and that nitrogen decomposition processes lead to significant N2O emissions. Carbon decomposition favors CO2 over CH4 production probably because of aerobic stockpile conditions or CH4 oxidation in the outer stockpile layers. Although the GHG emission rate decreased with biosolid age, managers of biosolid stockpiles should assess alternate storage or uses for biosolids to avoid nutrient losses and GHG emissions.
污水处理过程会产生大量污水污泥，这些污泥经过干燥后，通常储存在处理厂的生物固体储存库中。由于生物固体富含可分解的有机物，它们可能是温室气体（GHG）排放的重要来源，但目前还没有直接测量储存库 GHG 的方法。因此，我们使用手动静态室，从 2009 年 12 月至 2011 年 11 月，对澳大利亚墨尔本西部处理厂（WTP）三个不同年龄组的生物固体储存库进行了每月一次的甲烷（CH4）、氧化亚氮（N2O）和二氧化碳（CO2）的直接排放测量。所有生物固体储存库都是 CH4 和 N2O 排放的重要点源。最年轻的生物固体（<1 岁）的 CH4 和 N2O 排放量最大，每年每 Mg 生物固体为 60.2kg 的 CO2-e。1 至 3 岁的储存库总体 GHG 排放量较小（约 29kg CO2-e Mg-1 yr-1），而最古老的储存库排放量最小（约 10kg CO2-e Mg-1 yr-1）。所有储存库中甲烷排放量都可以忽略不计，但 N2O 和 CO2 的相对贡献随储存库年龄而变化。最年轻的储存库排放的 GHG 中有三分之二是 N2O，而 1-3 岁的储存库排放的 N2O 和 CO2 相等，而在最古老的储存库中 CO2 排放量占主导地位。我们没有检测到 GHG 排放的季节性变化，也没有观察到 GHG 通量与生物固体温度、水分含量或硝酸盐和铵盐浓度等环境变量之间的相关性。我们还根据一阶衰减模型对 CH4 排放进行了建模，并且模型基于估算的年度 CH4 排放量高于基于直接现场估算的年度 CH4 排放量。我们的结果表明，储存库中的易分解有机物质随着时间的推移而分解，氮分解过程导致大量 N2O 排放。碳分解有利于 CO2 而不是 CH4 的产生，这可能是由于有氧储存库条件或外层储存库层中的 CH4 氧化。尽管 GHG 排放率随生物固体年龄的增加而降低，但生物固体储存库的管理者应评估替代储存或生物固体的使用方法，以避免养分损失和 GHG 排放。
