STANDISH – After 20 years using ozone to kill harmful water-borne bacteria and viruses, the Portland Water District announced a new purifying method during a groundbreaking ceremony Tuesday morning at the district’s water treatment plant in Standish.

The district will still use the ozone, but the addition of an ultraviolet light system promises to treat more kinds of harmful, water-borne organisms while at the same time reducing overall energy costs.

Water district officials and representatives from Efficiency Maine, which donated $300,000 toward the construction of a new UV system, since it promises to save substantial energy costs for ratepayers, broke ground on a building that will store the UV treatment process. The new UV process will help the district meet new federal drinking water guidelines.

The ozone system is getting an upgrade, as well. No longer will the district treat ambient air in an effort to create ozone, which is a gas that, when added to water, kills harmful organisms. It will instead truck in liquid oxygen, which can more efficiently be converted into usable ozone gas.

While the ozone upgrade wasn’t necessary, the addition of a UV treatment process is meant to comply with federal regulation, issued in 2006. By spring 2014, the federal Environmental Protection Agency is requiring all water utilities using surface water (such as Sebago Lake) to upgrade their systems to kill cryptosporidium, a protozoa that can cause illness. The district’s UV project began about a month ago and is to be completed by December 2013.

While officials say the district tested for two years and found no cryptosporidium in the lake, the utility still needs to meet the federal guidelines. The UV system, which is being constructed by Portland-based D&C Construction and connects into the existing pipeline soon after it exits the ozone treatment facility, is the most cost-effective method to meet the new regulatory hurdle, officials say. It piggybacks on the existing ozone system, which has been in effect since the treatment plant’s construction in 1994. Together, they provide all-around disinfection of cryptosporidium, giardia and viruses.

The $12.8 million UV upgrade could have been more expensive had cryptosporidium been found, said environmental manager Paul Hunt.

“EPA is requiring all surface water suppliers in the country to design treatment as though cryptosporidium were there, because if it ever did and you didn’t design for it, then people could be made sick. But because our water quality is so high, the level of treatment was less and less expensive than if we had found cryptosporidium. So, our clean lake has saved ratepayers millions of dollars with this project and will continue to do that,” Hunt said.

Portland Water District customers, comprising 15 percent of Maine’s population or about 300,000 users, won’t notice any changes in the water coming from their tap as a result of the UV upgrade. The upgrades could cause rates to increase 6 percent, officials say, but that could be mitigated with energy efficiencies, as well as the expiration of a 20-year bond for the 1994 construction of the ozone plant.

“UV doesn’t affect taste, and ozone, which we’ve been using, actually improves and enhances the taste of water. It clarifies the water from dissolved organics,” said Emile Richard, who’s overseeing the project for the district.

The UV system works, Richard said, not by killing organisms, but by emitting light waves that disinfect the water-borne organisms, rendering them unable to reproduce in a host’s body. Ozone, which is the same chemical produced in a lightning strike and has three parts oxygen, actually kills organisms but does little against the hard-shell cryptosporidium virus, which the EPA is targeting. Cryptosporidium, transmitted by animal and human feces and mostly found in water, causes vomiting and diarrhea in humans.

“Light deactivates the organism, meaning it prevents them from being able to reproduce. So when an organism isn’t allowed to reproduce, it can’t generate a population enough to be effective in the host,” Richard explained. “Ozone attacks the body of the organism by disintegrating it. It’s more of a chemical attack, whereas UV is a light which actually gets to the DNA of the organism. These organisms are clear cells, and light can get through to their cellular parts.”

The new UV system, when complete, will consist of two treatment units each 14 feet long and featuring 84 UV lamps that are designed to come in contact with water molecules as they pass through the pipe. The two UV reactors, as they’re called, connect into the 48-inch diameter water mains as they exit the ozone treatment facility. Each unit is capable of treating 52 million gallons of water a day, which is the design capacity of the plant. The average amount of water used daily is about 24 million gallons.

Officials from the Portland Water District and others break ground on the new UV water treatment facility located at the Sebago Lake Water Treatment Facility on Route 35 in Standish. From left, Gordon Johnson, engineering manager at the Portland Water District; Guy Cote, water district board vice president; Roger Crouse, Maine CDC Drinking Water Program director; Michael Stoddard, Efficiency Maine Trust executive director; and Wayne Ross, water district board president.