Endocrine flocculation, osmosis followed by activated sludge and ultrafiltration

Endocrine disrupting compounds (EDCs) are a challenge for
water and wastewater treatment because they exist at very low concentrations in
the presence of substances at much higher concentrations competing for
adsorption sites.

Many separation processes such as precipitation, flocculation, and coagulation have been used for
the removal of EDCs from different water 3,5. EDCs may also be removed by bio-degradation
processes 35, but numerous investigations
showed significant variability between the treatment processes 36.

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Conventional biological processes such as constructed wetlands,
bio-filtration, and activated sludge have shown limited removal of EDCs 3,5.
Conventional WWTPs have been typically designed to remove the organic carbon
load and nutrients (N and P) but no attention was given to the specific removal
of EDCs xvi.

Whereas, advanced treatment processes such as ferrate 4 free radical
oxidation, photolysis, granular activated carbon, photocatalysis, ozonation,
separation, Fenton oxidation, chlorination, and membrane separation have shown
more satisfying results 3,5,7,8. Advanced oxidation processes (AOPs), such as
ozonation and non-thermal plasma, have also been studied and proven to achieve
good removal of EDCs in wastewater 30,32–34.
However, the effects of oxidation products are still not fully understood,
which may delay the wide utilisation of such methods. In addition, some hybrid
systems such as membrane bioreactor (MBR) followed by ultra- filtration/nano-filtration/reverse
flocculation, osmosis followed by activated sludge and ultrafiltration can also
remove EDCs efficiently from water and wastewater 3,9. Membrane techniques,
specifically reverse osmosis (RO) and nano-filtration (NF), have attracted
great attention for EDCs removal in wastewater treatment 37–39, while microfiltration (MF) and
ultrafiltration (UF) had limited performance due to their large pore sizes 40. Chemical fouling and bio-fouling remain the
major drawbacks of membrane application in wastewater though. Some researchers
have studied the adsorption of EDCs by activated carbon (AC) and found that AC
is effective in removing EDCs in the lab as well as pilot and full-scale plants
29. However, operational conditions should
be strictly controlled and large amount of AC is required in full-scale plants,
making this method expensive 31. Finally, given
the significant research carried out and knowledge gained so far on the fate of
EDCs in the treatment process and their effects on humans and the environment,
additional treatment modules to the existing WWTPs have been proposed and
investigated in the recent decade. These include physical, biological and
chemical advanced oxidation methods 29,30.