Page 60 - Materials Chemistry, Second Edition

Life Cycle Assessment of Municipal Wastewater and Sewage Sludge Treatment 41

Different tertiary treatments based on advanced wastewater treatment tech-
nologies (sand filtration, ozonation, and membrane bioreactors [MBRs]) have been
assessed for their influence on the removal of a range of micropollutants, specifically
organic substances, heavy metals, estrogens, and pathogens (Høibye et al., 2008;
Wenzel et al., 2008; and Muñoz et al., 2009).
More recently, Rodriguez-Garcia et al. (2014b) reported a more extensive analy-
sis including seven WWTPs using MBR and four novel MBR configurations at
pilot-plant scale. The former (i.e., the seven full-scale plants) showed the impor-
tance of removing eutrophying substances, whereas the latter (the four novel
MBRs) focused on the removal of pharmaceuticals and personal care products
(PPCPs), of which only hormones were found to be significant for the toxicity
impact categories.
Fugitive emissions of CH and N O in WWTPs are an environmental issue
2
4
with increasing importance within the scientific and technical literature (Nair
et al., 2014; Pijuán et al., 2014; Venkatesh et al., 2014; and Yoshida et al., 2014b).
CH is principally formed in the WWTP units, where anaerobic conditions pre-
4
vail (Daelman et al., 2012), while N O is mainly generated in anoxic areas of
2
activated sludge reactors (Ahn et al., 2010). However, Guisasola et al. (2008)
reported that dissolved CH present in the sewer influent is emitted via strip-
4
ping in the aerated units. Detailed emission inventories from WWTPs are being
conducted in several countries (Kampschreur et al., 2009; Ahn et al., 2010), and
models have been developed to estimate these emissions (Foley et al., 2010b;
Rodríguez-García et al., 2012), demonstrating the importance of considering
the environmental impacts of wastewater treatment under a holistic perspective.
A long-term study performed in the Kralingseveer WWTP (The Netherlands)
reported that the quantification of direct emissions of N O and CH exceeded the
4
2
plant’s indirect CO emissions related to electricity use (Daelman et al., 2013).
2
A more recent study performed in two different Spanish WWTPs included the
results from GHG sampling campaigns in the environmental assessment of the
facilities (Figure 3.4); the authors concluded that ruling out this type of data will
lead to an underestimation of between 15% and 35% of the final global warming
potential (GWP) impact (Lorenzo-Toja et al., 2015).

3.5.2 tHe paradiGm of nutrient removal or
nutrient recovery from WaSteWaterS
Gallego et al. (2008) quantified the environmental impact of several configurations
to remove N and P in 13 WWTPs of less than 20,000 persons equivalent. The con-
tent of P, N, and organic matter in the treated effluent and the content of heavy
metals in the sludge were identified as the most significant impacts for all WWTPs.
Electricity use plays an important role in five of seven impact categories and pres-
ents the highest importance in four of them. When technologies were compared,
BioDenipho and aerobic-anoxic treatments were found to be the less damaging
®
options for secondary treatment, as they attained higher removal efficiencies of N
and P than extended aeration. The potential for P removal was assessed in different