The decision on whether or not to install a $7.1 million ultraviolet disinfection system at the Littleton/Englewood Wastewater Treatment Plant is on hold while members of the Englewood and Littleton city councils and staff evaluate the data presented at a June 28 joint meeting.

The June 28 meeting was for the presentation of a second opinion about last year’s evaluation by consultant Brown and Caldwell recommending the UV system be installed immediately.

Littleton’s city council hired consultant CH2M HILL to do an independent evaluation of the immediate need for a UV system.

The CH2M HILL report to the joint city council meeting stated the plant will eventually have to install a UV system but it doesn’t have to be done right now because the current process meets all federal and state treatment standards.

The plant on South Platte River Drive provides wastewater treatment for 300,000 regional customers. It is jointly owned by the two cities so the ultimate decision to proceed with any capital project rests with the two city councils.

Littleton Mayor Doug Clark chaired the June 28 joint council meeting and turned it over to the two CH2M HILL representatives, who presented their company’s evaluation of the ability of the plant to meet the requirements established in the 2014 permit granted by the Colorado Department of Public Health and Environment.

Paul Swaim, CH2M HILL vice president of global technology for water treatment, said future regulations probably will mandate installation of a UV process

However, he said based on evaluation of plant data from January 2009 until March 2011, the current system provides wastewater treatment that meets the 2014 standards for ammonia removal and treatment for E.coli. However, even though the current process is very complex, there appears to be a low risk of compliance failure.

CH2M Hill representative Larry Schimmoller, global technology leader, water reuse, said ammonia removal is particularly complex because, at a later treatment stage, a small amount of ammonia must be mixed with chlorine to provide disinfection. Then another chemical must be added to remove the chlorine before the treated water is returned to the river.

He said while the current system meets ammonia removal limits and requirement for treatment for E.coli, installation of UV disinfection would create provide a less complex treatment system and eliminates the need for chlorine use.

Both men said the UV system is effective and they reported 13 of the 15 wastewater treatment plants in Colorado surveyed used UV disinfection.

Littleton Councilmember Jim Taylor asked how long it would be before the UV installation would be required.

“The 2014 permit will be good for five years so it is likely it will be 15 or 20 years until UV installation will be required at the Littleton/Englewood plant,” Swaim said.

Clark wrapped up the meeting when questions ended.

“I don’t think anyone expected a decision today since this is the first time the Englewood people have seen this report,” he said. “I would guess they would like take time to discuss this information with staff and review the data.”

He said once Englewood has evaluated the report, another joint council meeting will be scheduled to decide when a UV system should be installed at the wastewater treatment plant.