AUBURN – Homeland security costs are pushing the Twin Cities’ water utilities to change treatment methods a few years ahead of schedule.

Norm Lamie, general manager of the Auburn Water District, said the Lewiston and Auburn utilities hope to begin using liquid chlorine, or sodium hypochlorite, by this time next year. They hope to convert water treatment at the Lewiston-Auburn Water Pollution Control Authority by spring 2009.

Both cities use gaseous chlorine now to treat drinking water as it comes from Lake Auburn and wastewater as it returns to the Androscoggin River. Gaseous chlorine is a potentially hazardous chemical strongly regulated by the federal government.

“And as the increasing regulations on the federal level have gotten more and more onerous, the number of producers have decreased,” Lamie said. That’s made the chemical grow more expensive over the past five years.

Other federal guidelines will require both cities to provide at least two means of water purification by 2012. They hope to install an ultra-violet system about then.

“And then, we’ll have both chlorine and UV treatment,” Lamie said. “We had considered converting to liquid chlorine then, in 2011. But the way federal guidelines on gaseous chlorine have changed, it makes sense to do it ahead of schedule.”

Lamie said it will cost between $400,000 and $500,000 to complete the conversion. They’ve hired Massachusetts-based engineering firm Camp Dresser and McKee Inc. to design the conversions.

Costs would be split between the two cities. He estimates liquid sodium hypochlorite costs about 10 percent less than gaseous chloride now. That gap will widen as the gas gets more rare and expensive.

“So we’re hoping to save a little more over time,” he said.

Sodium hypochlorite contains about 15 percent active chlorine – about five times as potent as store-bought chlorine bleach.