Page 301 - Materials Chemistry, Second Edition

282 Life Cycle Assessment of Wastewater Treatment

the wastewater. However, the concept of the circular economy has moved WWTP
concepts to other technologies with overall low environmental impacts, cost, and
investment operations and high energy efficiency. Thus, WWTP should produce not
only a clean effluent fulfilling the environmental legislation, but also a treated stream
able to be reused, recovering energy and nutrients during the process (Massara et al.,
2016).
In the case of industrial effluents, anaerobic treatment has been proposed in dif-
ferent configurations and different industries (Massara et al., 2016; Dvořák et al.,
2015), such as the dairy industry (Georgiopoulou et al., 2008; Bialek et al., 2014),
food-processing plants (Wu et al., 2010), the corn starch industry (Vera et al., 2015),
or olive mill wastewater and agro-industrial wastewaters in general (Meneses-
Jácome et al., 2016; Jaouad et al., 2016).
The LCA inventory of some anaerobic reactor configurations, such as AnMBR,
lacks critical data, such as energy demand, since literature on full-scale application
is scarce, and even data reported at pilot-plant scale are not completely accepted,
as the limited size could compromise the reactor’s energy attainment (Krzeminski
et al., 2017). Nevertheless, Table 13.1 summarizes the most relevant studies regard-
ing anaerobic reactors in the treatment of industrial wastewaters.
Foley et al. (2010) evaluated the potential environmental impacts of three indus-
trial wastewater treatment alternatives: a high-rate anaerobic sludge reactor with
biogas generation (with full-scale data); a microbial fuel cell treatment with direct
electricity generation (pilot plant–scale data); and a microbial electrolysis cell with
hydrogen peroxide production (data obtained from a laboratory-scale reactor). The
results demonstrated a major negative impact associated with electricity consump-
tion in all cases. The microbial electrolysis cell with hydrogen peroxide production
was the best option of the three technologies, mainly due to the positive impact of
the production of chemicals. In the anaerobic reactor, the positive impact derived
from biogas and energy production outweighed the negative environmental impacts.
Actually, the benefits coming from the displacement of fossil fuel–dependent
resources outweigh the environmental cost of constructing and operating the treat-
ment plant in all three cases, although the limited scale of the data available for one
of the processes critically influenced this result (Foley et al., 2010). However, the
environmental benefits obtained from anaerobic biological reactors do not always
balance the negative potential impacts. Vera et al. (2015) performed the environ-
mental evaluation of a corn starch WWTP with simultaneous microbial oil produc-
tion as compared with a non-oil-producing treatment scheme. The implementation
of the new system required substantial inputs of electrical energy, increasing the
indirect GWP related to the electricity consumption by about 2330%. The produc-
tion of microbial oil by a fermentation process increased the COD removal, reducing
the negative effect. But finally, it was necessary to implement the system using corn
stover biomass as a renewable source of energy to obtain environmental benefits by
reducing the GWP impact and improving the local economy.
It is evident that the interpretation of LCA results is crucial in this methodology,
but this is not easy to perform. For example, a comparison of the environmental per-
formance of different configurations for pulp and paper effluent treatment based on
six processes, including an upflow anaerobic sludge blanket (UASB) reactor, revealed