A Greek research team has tested common tertiary treatments’ effectiveness in cleaning pharmaceuticals and other ECs from wastewater
According to the United States Environmental Protection Agency, emerging contaminants (ECs) are a group of chemicals, predominantly of manmade origin, that exist and persist in the soil, air, food, and water.
ECs, also known as “contaminants of emerging concern,” are materials “characterized by a perceived, potential, or real threat to human health or the environment or by a lack of published health standards.” Although they can be physiologically disruptive to humans and other organisms, regulation has yet to fully catch up to their growing threat to the environment.
EC Removal Technologies
While water management long lacked a comprehensive study of the best wastewater treatment technologies for EC removal, a new study led by Greek researchers Dr. Olga S. Arvaniti and Professor Athanasios S. Stasinakis now fills in many of the knowledge gaps.
The team prioritized using common treatment technologies for conventional pollutants as tertiary treatments for ECs in order to meet environmental protection goals without elevated costs for facilities.
ECs of different chemical classes coexist in domestic sewage, creating chemical mixtures, so another goal was to determine which technologies were effective against many ECs. Testing was conducted under actual sewage treatment plant conditions. The 38 ECs studied included:
- Pharmaceuticals (PhCs).
- Endocrine-disrupting chemicals (EDCs).
- Benzotriazoles (BTRs).
- Benzothiazoles (BTHs).
- Perfluorinated compounds (PFCs).
Findings showed that microfiltration (MF) only removed one of the 38 ECs, so it was relegated to the pretreatment stage. Exposure to ultraviolet radiation fared slightly better, removing five ECs. Nanofiltration membranes with smaller pores effectively removed eight of the ECs better than the other tested membrane processes, but only from two chemical classes, PhCs and PFCs, with negligible effect on EDCs. Powdered activated carbon (PAC) treatment, however, fared better.
Results showed PAC treatment removed most of the list of ECs, with 70% removal rates for nine compounds, partial removal for 22 compounds, and low removal rates for the remaining seven.
The study was the first of its kind to comprehensively look at applying familiar tertiary wastewater treatment processes to many EC classes under realistic operating conditions. The team suggests future research to scale up PAC to actual conditions, combining it with other processes, and conducting a comprehensive economic and environmental assessment for EC removal.
Potential of Reverse Osmosis
There’s some controversy over whether water purification technologies should be chosen based solely on cost, or whether using the technology best fit for specific ECs should be the only consideration. Perhaps the higher cost of reverse osmosis (RO) excluded it from the study, but the authors acknowledge it may be highly effective.
For example, in one recent study, the smaller pore sizes of RO membranes rejected more than 90% of all the studied ECs. Another study showed tight nanofiltration running a close second to RO, with RO still leading at 85% rejection of neutral contaminants and 99% rejection of ionic contaminants.
No matter how clients decide how to address ECs, Seven Seas Water Group commands a full roster of tertiary treatment technologies from a wide supplier network. Our experts tailor EC treatment systems to specific source waters, and our Water-as-a-Service® contracts streamline the infrastructure delivery process with P3, BOO, and BOOT structures. Contact Seven Seas’ experts to find out more about the flexible, low-stress options.
Image Credit: totojang1977/123RF