New treatment appears successful in decreasing number of invasive zebra mussels in city’s water main

The interior of a City of Lawrence water transmission main is seen covered in zebra mussels.

After six months of using special electrical currents to treat a water main coated with an invasive species of mussels, city utility officials say they have seen a significant decrease in their numbers.

Last spring, the city discovered a blossoming zebra mussel colony inside the transmission main that brings water from Clinton Lake to the Clinton Reservoir Water Treatment Plant. City officials said that in a relatively short period of time, the colony had extended for 2,000 feet within the pipe.

Indications are that the special equipment purchased to manage the infestation is working well, and Water Quality Manager Aurora Shields said it was fortunate that the colony was detected before it completely clogged the transmission line.

“It can happen very quickly, so we were very glad that we found it and were able to put measures in place to deal with it in the future,” Shields said.

Left unchecked, the mussels can encrust water-intake valves, choke off the inside of pipes and necessitate costly repairs. Utilities Treatment Manager Steven Craig said the colony inside the transmission main was discovered when a section of pipe was being replaced; just 18 months before that an inspection had found no mussels present. The City Commission subsequently approved the purchase of $80,000 worth of the copper ion generation equipment for controlling the mussels.

Craig said that as far as the city is able to tell, the treatment process is going well. He said the city can’t send video equipment into the transmission main without shutting down the water treatment plant, but fewer mussels in the system are being detected. Specifically, Craig said that screening baskets between the lake intake and the treatment plant have accumulated fewer mussels, and no mussels have been found at the plant itself.

“We would also see some periodically slough off the line and end up at the plant, and we haven’t seen that yet either,” Craig said.

Managing the mussels will also have some ongoing costs. Shields said the equipment passes an electrical current through a copper plate, releasing positively charged copper ions that discourage the mussels from attaching to the walls of the transmission line. She said the unit’s copper tubing needs to be replaced regularly, and will cost about $5,000 annually.

“For as long as there are zebra mussels in the world, we will have to use this equipment,” Shields said.

The mussels are less than two inches long and are native to the Black and Caspian seas. They attach to any surface in the water and have been spread around the world by cargo ships. In North America, the mussels were first found in the Great Lakes region in the 1980s and soon spread to other bodies of water. They were first found in Kansas in 2003.

Lawrence has two major sources for its drinking water, the Kansas River and Clinton Lake, and both have zebra mussel populations. Craig said mussel colonies have not been found in the city’s intake system for the river.

Zebra mussels were discovered in the Kansas River in 2009 and in Clinton Lake in 2013. The mussels attach themselves to docks, ramps or boats, and special measures need to be taken to stop the mussels and their microscopic larvae from spreading to uncontaminated bodies of water, according to the Kansas Department of Health and Environment. Those include never moving fish, bait or water from one body of water to another and washing boats and equipment with hot water and allowing them to dry for at least five days.

Since the installation of the copper ion generation equipment, increased monitoring of drinking water has also occurred. Too much copper can be hazardous to human health. The city’s water treatment process already treats drinking water for copper, Shields said, but the frequency of monitoring has been stepped up to ensure safety.

Craig said that the next time the Clinton Reservoir Water Treatment Plant is shut down for maintenance, the city will be able to use video equipment to assess the inside of the transmission main.