Researchers have found that a common species of freshwater green algae is capable of removing certain endocrine disrupting chemicals (EDCs) from wastewater. The results of this study from the Desert Research Institute (DRI) in Las Vegas have been recently published in the in the international journal Environmental Pollution.
In the study, DRI researchers Xuelian Bai and Kumud Acharya explored the potential for use of a species of freshwater green algae called Nannochloris to remove EDCs from treated wastewater.
EDCs are natural hormones and can also be found in many plastics and pharmaceuticals. They are known to be harmful to wildlife, and to humans in large concentrations, resulting in negative health effects such as lowered fertility and increased incidence of certain cancers.
“This type of algae is very commonly found in any freshwater ecosystem around the world, but its potential for use in wastewater treatment hadn’t been studied extensively,” said Bai, lead author and Assistant Research Professor of environmental sciences at DRI. “We wanted to explore whether this species might be a good candidate for use in an algal pond or constructed wetland to help remove wastewater contaminants.”
During a seven-day laboratory experiment, the researchers grew Nannochloris algal cultures in two types of treated wastewater effluents collected from the Clark County Water Reclamation District in Las Vegas, and measured changes in the concentration of seven common EDCs.
In wastewater samples that had been treated using an ultrafiltration technique, the researchers found that the algae grew rapidly and significantly improved the removal rate of three EDCs (17β-estradiol, 17α-ethinylestradiol and salicylic acid), with approximately 60 percent of each contaminant removed over the course of seven days. In wastewater that had been treated using ozonation, the algae did not grow as well and had no significant impact on EDC concentrations.
One of the EDCs examined in the study, triclosan, disappeared completely from the ultrafiltration water after seven days, and only 38 percent remained in the ozonation water after seven days — but this happened regardless of the presence of algae, and was attributed to breakdown by photolysis (exposure to light).
“Use of algae for removing heavy metals and other inorganic contaminants have been extensively studied in the past, but for removing organic pollutants it has just started,” said Acharya, Interim Vice President for Research and Executive Director of Hydrologic Sciences at DRI. “Our research shows both some of the potential and also some of the limitations for using Nannochloris to remove EDCs from wastewater.”
A previous study by Bai and Acharya published in November 2018 in the journal Environmental Science and Pollution Research had examined the impacts of these same seven EDCs on quagga mussels (Dreissena bugensis) collected from Lake Mead near Las Vegas. Their results showed that several of the EDCs (testosterone, bisphenol A, triclosan, and salicylic acid) were accumulating in the body tissues of the mussels.
Bai explained, “Algae sit at the base of the food web, thereby providing food for organisms in higher trophic levels such as quagga mussels and other zooplantkons. Our study clearly shows that there is potential for these contaminants to biomagnify, or build up at higher levels of the food chain in the aquatic ecosystem.”
Although Las Vegas’s treated wastewater meets Clean Water Act standards, Bai hopes that her research will draw public attention to the fact that treated wastewater is not 100 percent clean, and will also be helpful to utility managers as they develop new ways to remove untreated contaminants from wastewater prior to release.
“Most wastewater treatment plants are not designed to remove these unregulated contaminants in lower concentrations, but we know they may cause health effects to aquatic species and even humans, in large concentrations,” Bai said. “This is concerning in places where wastewater is recycled for use in agriculture or released back into drinking water sources.”