effective than RO but still performant at high contamination (Santos et al. 2015).
Scaling is a main limitation of membranes (RO/NF) with mine water as salt
formation could damage and impair their proper function. As low temperature
favors the crystallization of minerals, this effect is enhanced. TDS, TSS, alkalinity, and bacterial-algal fouling potential are also factors to influence the efficiency
of the membranes, along with energy consumption, which increases the treatment
costs. The pre-treatment of contaminated water is therefore required. The
biosurfactant—rhamnolipid—addition was studied in micellar-enhanced ultrafiltration (MEUF) of heavy metals from contaminated waters (El Zeftawy and
Mulligan 2011). The MEUF system performance was successfully investigated
for copper, zinc, nickel, lead, and cadmium retention by two different membranes
with molecular weight cutoffs (MWCO) of 10,000 Da and 30,000 Da.
2. Evaporation allows the separation of contaminants from a concentrate (brine),
by thermal water removal. Mechanical evaporation/crystallization shows the
greatest prospects. Brine concentrators use a calcium sulfate seed crystal that
acts as a nucleation promoter for gypsum removal. Although efficient, evaporation is mechanically complex and expensive, requires energy and maintenance, as
well as steam and cooling water (Sandy and DiSante 2010). Scale and corrosion
are additional constraints, especially when dealing with high ionic -strength
effluents.
3. Sorption binds undesirable ions in water to solid particles, which can be natural
and residual materials. Over the last decades, various studies have evaluated the
performances of activated carbon, modified biochar, and/or nanomaterials to
remove both organic and inorganic contaminants from municipal and/or industrial wastewater (Dubey et al. 2017; Rodriguez-Narvaez et al. 2017; Sophia and
Lima 2018; Thines et al. 2017). The main advantage of using natural or residual
sorbents to remove organic CECs from municipal and industrial wastewater is the
nonproduction of toxic or treatment of recalcitrant degradation products.
According to the literature review of Rivera-Utrilla et al. (2013), activated
carbons demonstrate high adsorption capacities to remove pharmaceuticals
from waters, with values ranging from 25 to 260 mg/g depending on the sorbent
used and the CEC of interest. The performances of carbon-based nanomaterials
depending on the treatment used for their production are discussed by Adeleye
et al. (2016), Sophia and Lima (2018), and Zhao et al. (2018). For example, Peng
et al. (2012) were able to achieve 100% removal of norfloxacin, an antibiotic,
using single-walled nanotubes (SWNT) and only 35% removal when using multiwalled nanotubes (MWNT). Similarly, the removal of tetracycline achieved 92%
with SWNT, whereas only 16% of this antibiotic was removed with MWNT
(Ji et al. 2010). Halogenated organics such as trichloroethylene, trichlorobenzene
(TCB), dichlorobenzene (DCB), and polychlorinated biphenyls (PCBs) can efficiently be removed using carbon-based nanomaterials (Adeleye et al. 2016). In
their review, Zhao et al. (2018) compared the performances of several
nanomaterials activated or not to remove CECs from water as well as their
29 Future Prospects for Treating Contaminants of Emerging Concern in. . .
595
Scaling is a main limitation of membranes (RO/NF) with mine water as salt
formation could damage and impair their proper function. As low temperature
favors the crystallization of minerals, this effect is enhanced. TDS, TSS, alkalinity, and bacterial-algal fouling potential are also factors to influence the efficiency
of the membranes, along with energy consumption, which increases the treatment
costs. The pre-treatment of contaminated water is therefore required. The
biosurfactant—rhamnolipid—addition was studied in micellar-enhanced ultrafiltration (MEUF) of heavy metals from contaminated waters (El Zeftawy and
Mulligan 2011). The MEUF system performance was successfully investigated
for copper, zinc, nickel, lead, and cadmium retention by two different membranes
with molecular weight cutoffs (MWCO) of 10,000 Da and 30,000 Da.
2. Evaporation allows the separation of contaminants from a concentrate (brine),
by thermal water removal. Mechanical evaporation/crystallization shows the
greatest prospects. Brine concentrators use a calcium sulfate seed crystal that
acts as a nucleation promoter for gypsum removal. Although efficient, evaporation is mechanically complex and expensive, requires energy and maintenance, as
well as steam and cooling water (Sandy and DiSante 2010). Scale and corrosion
are additional constraints, especially when dealing with high ionic -strength
effluents.
3. Sorption binds undesirable ions in water to solid particles, which can be natural
and residual materials. Over the last decades, various studies have evaluated the
performances of activated carbon, modified biochar, and/or nanomaterials to
remove both organic and inorganic contaminants from municipal and/or industrial wastewater (Dubey et al. 2017; Rodriguez-Narvaez et al. 2017; Sophia and
Lima 2018; Thines et al. 2017). The main advantage of using natural or residual
sorbents to remove organic CECs from municipal and industrial wastewater is the
nonproduction of toxic or treatment of recalcitrant degradation products.
According to the literature review of Rivera-Utrilla et al. (2013), activated
carbons demonstrate high adsorption capacities to remove pharmaceuticals
from waters, with values ranging from 25 to 260 mg/g depending on the sorbent
used and the CEC of interest. The performances of carbon-based nanomaterials
depending on the treatment used for their production are discussed by Adeleye
et al. (2016), Sophia and Lima (2018), and Zhao et al. (2018). For example, Peng
et al. (2012) were able to achieve 100% removal of norfloxacin, an antibiotic,
using single-walled nanotubes (SWNT) and only 35% removal when using multiwalled nanotubes (MWNT). Similarly, the removal of tetracycline achieved 92%
with SWNT, whereas only 16% of this antibiotic was removed with MWNT
(Ji et al. 2010). Halogenated organics such as trichloroethylene, trichlorobenzene
(TCB), dichlorobenzene (DCB), and polychlorinated biphenyls (PCBs) can efficiently be removed using carbon-based nanomaterials (Adeleye et al. 2016). In
their review, Zhao et al. (2018) compared the performances of several
nanomaterials activated or not to remove CECs from water as well as their
29 Future Prospects for Treating Contaminants of Emerging Concern in. . .
595