Page 59 - Materials Chemistry, Second Edition

40 Life Cycle Assessment of Wastewater Treatment

energy, whereas its main drawback is the air emission of toxic substances into the
environment.
Focusing on energy and greenhouse gas (GHG) emissions, Houillon and Jolliet
(2005) compared a range of scenarios for wastewater sludge treatment: agricul-
tural spreading, fluidized bed incineration, wet oxidation, pyrolysis, incineration
in cement kilns, and landfill. From an energy perspective, the first two obtained
the best results. In another work, anaerobic digestion, pyrolysis, and incinera-
tion of sludge were compared (Hospido et al., 2005). Regarding eutrophication,
the benefits due to avoidance of fertilizers if digested sludge is applied to the
land are not present in the other two options, since no nutrients are recovered.
However, land application also has its drawbacks, since the toxic impacts associ-
ated with heavy metal release are strongly reduced when thermal processes are
considered.
The trade-off between anaerobic digestion, aerobic stabilization, and incineration
of sewage sludge indicated that for eutrophication- and toxicity-related categories
(except for terrestrial ecotoxicity), facilities performing anaerobic digestion followed
by sludge incineration show higher environmental impacts compared with plants
treating the sludge by aerobic stabilization prior to agricultural sludge application
(Niero et al., 2014).
In the context of sustainable wastewater treatment and sludge management, future
research is needed for the quantification of long-term toxic impacts on humans and
ecosystems and the potential for carbon sequestration, as well as regarding the assess-
ment of the economic and social repercussions of different management options.

3.5 NEW GENERATION OF WWTPS UNDER
A LIFE CYCLE PERSPECTIVE
Although the main objective of conventional WWTPs has traditionally been the
removal of organic matter, nowadays, key words in wastewater treatment facili-
ties include terms such as micropollutants, GHG emissions, nutrient removal,
resource recovery, reclaimed water, and high-quality effluents. Consequently, LCA
studies should comprise these new targets in the analysis of wastewater treatment
technologies.

3.5.1 QuantifyinG Hidden impactS: emerGinG

pollutantS and direct GHG emiSSionS
Micropollutants are considered as a potential hazard for aquatic organisms and
human health (Carballa et al., 2004). However, their inclusion in life cycle environ-
mental assessments of WWTPs was not possible until their characterization factors
(CFs) for toxicity were available. The potential impacts on ecotoxicity and human
toxicity of wastewaters containing priority and emerging pollutants were quantified
according to the methodology developed by Muñoz et al. (2008), which was later
updated by Alfonsín et al. (2014) by means of the USEtox (Rosenbaum et al., 2008)
and USES-LCA 2.0 (van Zelm et al., 2009) methodologies.