Research tracks tertiary treatments' emerging contaminants removal

New research provides a comprehensive assessment of the effectiveness of tertiary treatment processes in removing several types of emerging contaminants, according a press release by Higher Education Press.

Removing emerging contaminants with tertiary treatments already commonly applied in wastewater treatment plants could provide immense cost savings. With this background, Olga S. Arvaniti and Athanasios S. Stasinakis from University of the Aegean and their team members investigated the effectiveness of microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), ultraviolet (UV) radiation, and powdered activation carbon (PAC) adsorption to remove selected contaminants from secondary clarifier effluents.

Emerging contaminants (ECs) including pharmaceuticals (PhCs), endocrine disrupting chemicals (EDCs), benzotriazoles (BTRs), benzothiazoles (BTHs) and perfluorinated compounds (PFCs), pose a potential ecological threat when they are discharged into the aquatic environment.

UV disinfection, PAC adsorption, and membranes are some of the most common physico-chemical tertiary treatment processes applied worldwide to improve the quality of treated wastewater effluent.

Their work examined the removal of 38 contaminants (PFCs, BTRs, EDCs, BTH and PhCs) at environmentally relevant concentrations, which is the first comprehensive assessment common tertiary wastewater treatment process and relevant operating conditions for a wide range of EC classes. This study, titled “Effectiveness of tertiary treatment processes in removing different classes of emerging contaminants from domestic wastewater,” is published online in Frontiers of Environmental Science & Engineering.

In this work, 38 different ECs (PhCs, EDCs, BTRs, BTHs and PFCs) were initially identified and quantified in the biologically treated wastewater collected from Athens’ (Greece) wastewater treatment plant. Processes already used in existing plants — such as MF, NF, UF, UV radiation, and PAC adsorption — were assessed for contaminant removal, under the conditions that represent their actual application for disinfection or advanced wastewater treatment.

The results indicated that microfiltration removed only one out of the 38 contaminants. UV radiation in the studied conditions showed low to moderate removal for five out of the 38 contaminants. Nanofiltration showed better results than ultrafiltration due to the smaller pore sizes of the filtration system. However, this enhancement was observed mainly for eight compounds originating from the classes of PhCs and PFCs, while the removal of EDCs was not statistically significant.

Among the various studied technologies, PFC stands out due to its capability to sufficiently remove most contaminants. In particular, removal rates higher than 70 percent were observed for nine compounds, 22 were partially removed, while seven demonstrated low removal rates.

The study also provided a constructive suggestion that future research should focus on scaling-up PAC in actual conditions, combining PAC with other processes, and conducting a complete economic and environmental assessment of the treatment.