Occurrence, impacts and removal of emerging substances of concern from wastewater

• Emerging substances of concern (ESOC) are present in water resources worldwide.
• ESOC are mutagens and carcinogens with effect on both aquatic organisms and humans.
• Conventional wastewater treatment processes are ineffective at ESOC removal.
• Membrane bioreactor technology can remove ESOC but has fouling limitation.
• Granulation technology and nano-remediation have strong potential for ESOC removal.

Emerging substances of concern (ESOC) have recently been detected in water resources worldwide, raising human and environmental health concerns. This paper provides an overview of the different classes of ESOC, their impacts, extent of removal by conventional wastewater treatment technologies such as activated sludge process, and documented results on emerging innovative technologies. Conventional wastewater treatment plants exhibit some limitations with respect to ESOC removal since ESOC were not considered in their initial design. Although, advanced oxidation processes using ozone with other oxidation agents such as UV (ultraviolet), hydrogen peroxide, titanium oxide, etc., prove effective, they are cost prohibitive and can produce by-products with unknown toxicity. Early results for emerging biological technologies such as membrane bioreactors (MBRs) and granulation biotechnology indicate very promising ESOC removal. However, membrane fouling is the main drawback of MBRs as it significantly reduces membrane performances and membrane life resulting in an increase in maintenance and operating costs. The main drawback of granulation technology is the deterioration in granule stability under long-term operation and lack of a successful pilot- or full-scale application. Thus, further research is required to abate membrane fouling in MBRs and enhance long-term granule stability in granular systems. The technological revolution offered by nano-materials (NMs) provides a new potential for ESOC removal through nano-remediation. Effective removal of ESOC has been reported using nano-adsorbents, nano-membrane filters and photocatalysts. However, the environmental fate and the toxicological impact of NMs need to be assessed for their potential toxicity and bioaccumulation.