Niccolò Cusano University, via Don Carlo Gnocchi 3, 00166 Rome, Italy.
Industrial Engineering Department, University of Florence, via Santa Marta 3, 50139 Firenze, Italy.
Waste Manag. 2017 Nov;69:365-376. doi: 10.1016/j.wasman.2017.08.040. Epub 2017 Aug 31.
A Life Cycle Assessment (LCA) was applied to compare different alternatives for sewage sludge treatment: such as land spreading, composting, incineration, landfill and wet oxidation. The LCA system boundaries include mechanical dewatering, the alternative treatment, transport, and final disposal/recovery of residues. Cases of recovered materials produced as outputs from the systems, were resolved by expanding the system boundaries to include avoided primary productions. The impact assessment was calculated using the CML-IA baseline method. Results showed that the incineration of sewage sludge with electricity production and solid residues recovery collects the lowest impact indicator values in the categories human toxicity, fresh water aquatic ecotoxicity, acidification and eutrophication, while it has the highest values for the categories global warming and ozone layer depletion. Land spreading has the lowest values for the categories abiotic depletion, fossil fuel depletion, global warming, ozone layer depletion and photochemical oxidation, while it collects the highest values for terrestrial ecotoxicity and eutrophication. Wet oxidation has just one of the best indicators (terrestrial ecotoxicity) and three of the worst ones (abiotic depletion, human toxicity and fresh water aquatic ecotoxicity). Composting process shows intermediate results. Landfill has the worst performances in global warming, photochemical oxidation and acidification. Results indicate that if the aim is to reduce the effect of the common practice of sludge land spreading on human and ecosystem toxicity, on acidification and on eutrophication, incineration with energy recovery would clearly improve the environmental performance of those indicators, but an increase in resource depletion and global warming is unavoidable. However, these conclusions are strictly linked to the effective recovery of solid residues from incineration, as the results are shown to be very sensitive with respect to this assumption. Similarly, the quality of the wet oxidation process residues plays an important role in defining the impact of this treatment.
生命周期评估（LCA）被应用于比较污水污泥处理的不同替代方案：如土地施用、堆肥、焚烧、填埋和湿式氧化。LCA 系统边界包括机械脱水、替代处理、运输以及残留物的最终处置/回收。从系统中产生的作为输出的回收材料案例，通过扩展系统边界以包括避免的初级生产来解决。使用 CML-IA 基线方法计算了影响评估。结果表明，焚烧污水污泥以生产电力和回收固体残渣，在人类毒性、淡水水生生态毒性、酸化和富营养化等类别中收集到最低的影响指标值，而在全球变暖与臭氧层消耗等类别中则具有最高的值。土地施用在非生物消耗、化石燃料消耗、全球变暖、臭氧层消耗和光化学氧化等类别中具有最低的值，而在陆地生态毒性和富营养化等类别中则具有最高的值。湿式氧化只有一个最佳指标（陆地生态毒性）和三个最差指标（非生物消耗、人类毒性和淡水水生生态毒性）。堆肥工艺显示出中间结果。填埋场在全球变暖、光化学氧化和酸化方面表现最差。结果表明，如果目标是减少污泥土地施用对人类和生态系统毒性、酸化和富营养化的常见做法的影响，那么能源回收焚烧显然会改善这些指标的环境性能，但资源消耗和全球变暖的增加是不可避免的。然而，这些结论严格取决于从焚烧中有效回收固体残渣，因为结果对这一假设非常敏感。同样，湿式氧化工艺残渣的质量在确定该处理的影响方面起着重要作用。
