Interior of Greater Cincinnati Water Works' Granular Activated Carbon (GAC) contactor building. The 240-mgd post-filtration GAC facility with onsite reactivation removes contaminants such as pharmaceuticals by adsorption. Photo: Greater Cincinnati Water Works
Ozone generators at River Mountains Water Treatment Facility in Las Vegas treat up to 300 mgd of water each day. Photo: Southern Nevada Water Authority
The conservative approach
Given that only a few have been detected in and around its service area, Administrative Scientist Gary Burlingame says the Philadelphia Water Department can't justify diverting resources from more pressing issues to eliminate trace levels of compounds that may or may not be harmful.
The department reports the presence of unregulated compounds in its annual water quality report and Web site.
The department uses chlorination, sedimentation, and filtration to treat surface water from the Delaware River and Schuylkill River watersheds, producing 270 mgd for 1.6 million people. It's investing about $500,000 in liquid chromatography and a double mass spectrometer to screen source water. “We want to establish a scientific understanding of the issue, to know what's out there in our watershed,” says Burlingame.
Until EPA requires monitoring of particular chemicals, the department's participating in voluntary cooperative efforts such as take-back programs and watershed controls through the Philadelphia Partnership for Pharmaceutical Pollution Prevention. Other members include EPA Region 3 and the Women's Health and Environmental Network.The aggressive approach
Fifteen years ago, a small outbreak of cryptosporidiosis prompted the Southern Nevada Water Authority to introduce ozonation, replacing pre-oxidation with chlorine, even though cryptosporidium had never been detected in finished water.
Ozonation costs five to 10 times more than traditional treatment processes such as chlorine, depending on energy costs, but it also removes 80% to 90% of EDCs and PPCPs. As a result, the authority subsidized some of the early research in 1998 on the compounds' occurrence, was an early participant in studies about EDCs, and has been testing for EDCs since 2003.
“These communications are very important,” says Water Quality Research and Development Manager Dave Rexing. “As a consumer, I'd feel more confident in the safety of my water if I knew the agency was progressive and doing research into those areas.”
By selling 600 mgd to five municipal retail authorities, the authority ultimately supplies 2 million people. Its two plants draw Colorado River water through Lake Mead, applying ozone as a pre-oxidant and then ferric chloride as a coagulant.
Like Las Vegas, Greater Cincinnati Water Works (GCWW) has put in place a robust treatment train. But it tests for PPCPs as well as EDCs. The agency provides an average 135 mgd to 1.1 million people.
Ohio River water first goes through chemical coagulation, which makes the particulates sticky and heavy so they fall out of the water in the subsequent settling process. Then the water is filtered through sand. Finally, it is sent through granular activated carbon filters, a final step that removes organic molecules such as pesticides, oils, industrial chemicals, and pharmaceuticals.
Because numerous manufacturing plants are located along the river, managers chose granular activated carbon in case of an industrial spill. But Assistant Superintendent of Water Quality Jeff Swertfeger says research shows the process is also an effective treatment for removing EDCs and PPCPs. In 2007, the Water Research Foundation reported that routinely regenerating the material, as GCWW routinely does, removed all target compounds at participating water utilities.
“If we didn't have it in place, I'd be looking at a process — such as ozonation or membranes — that doesn't just remove EDCs and PPCPs but has other benefits that improve water quality,” he adds.
— Renner (email@example.com) is executive director of the Water Research Foundation, an international nonprofit organization that funds research that helps utilities provide safe, affordable drinking water.