Page 303 - Materials Chemistry, Second Edition

284 Life Cycle Assessment of Wastewater Treatment

LCA methodology has been also applied as a tool for the analysis of the best
available technology for the treatment of wastewater generated in the dairy industry
(Georgiopoulou et al., 2008). Among six different systems (activated sludge, high-
rate and extended aerated sludge, activated sludge with an anoxic reactor before the
aeration basin, an aerated lagoon, and a UASB reactor), AD was the most environ-
mentally friendly and economic option, based on lower GHG emissions and energy
requirements. In this work, the combination of economy and environment was
already established, something that has been further developed in other works. Thus,
it has been accepted that LCA should be combined with technical and economic
aspects (Krzeminski et al., 2017; Hospido et al., 2007), taking also into account the
social dimension, to obtain more complete indicators of sustainable development and
a holistic evaluation of the process (Meneses-Jácome et al., 2016; Smith et al., 2014).
In this sense, different approaches can be found linking all these aspects: LCA,
net energy balance, and life cycle cost as tools to determine the most cost-effective
option among different wastewater treatment alternatives. Thus, Smith et al. found
that energy consumption in AnMBR systems was four times higher than energy
recovery, and the GWP was higher than for other biological reactors for wastewater
treatment. But at the same time, the life cycle costs of the energy recovery system
were lower than those of conventional biological wastewater processes (Smith et al.,
2014). Wu et al. applied a combination of LCA, a fuzzy recognition system, and a
grey relational model to assess the potential environmental impacts related to the
operational efficiency and economic benefits of a food-processing industry in China
(Wu et al., 2010). The results obtained in this study revealed that an increase in ben-
efits with a reduction in consumption could be obtained by looking in the first place
for an improvement in the energy use ratio, which would secondarily ensure higher
COD removal.
To summarize all these studies, LCA combined with economic evaluation is a
critical tool for the evaluation of anaerobic biological reactors for the treatment of
industrial wastewater. This technology exhibits promising characteristics regard-
ing the sustainability of the process, such as GHG emissions mitigation and energy
recovery from the methane produced during the operation. However, each particular
technology and application should be evaluated, as the balance between benefits and
negative impacts is greatly influenced by materials and energy flows.

13.3 ANAEROBIC DIGESTION OF WASTEWATER SLUDGE (ADWWS)

As mentioned previously, the increasing concern to protect the environment from
harmful effects of WWTPs has led governments to adopt strict regulations regard-
ing water quality specifications. Thus, as an example, in EU countries, more effec-
tive WWTPs have been implemented according to specific regulations, increasing
the production of sewage sludge (Pradel et al., 2016; Gourdet et al., 2016). In this
context, in EU countries, about 10 million tonnes of dry solids of sludge is produced
yearly (Heimersson et al., 2017). According to these figures, it can be inferred that
sewage sludge management is a key aspect that must be considered in WWTP, as the
disposal of these wastes may represent up to 50% of the operating costs of a WWTP.
Sludge is a source of energy, carbon, and nutrient content (mainly nitrogen and