"Tiny Bubbles"

By K. Robert Wendel

When Hawaiian musician Don Ho wrote the song "Tiny Bubbles," it's a safe bet he didn't have wastewater treatment plants on his mind.

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But tiny bubbles are the name of the game at an existing waste water treatment plant on Reno's Westside. There, builders are totally renovating the existing plant and installing new and more efficient pumps, basins, mechanical equipment, filters and motors to cut energy usage.

The $41 million project is only adding an extra 6 million gallons a day of treatment capacity to the existing 40 MGD plant, but the new equipment will cut operating costs and provide better filtration for the area's waste water.

"Fine bubbles are better at oxygenating the water than larger bubbles," said project engineer Dave Michaut of Carollo Engineer's Reno office. "The fine bubbles have more surface area, so it's more efficient. You have to have enough air in there for the bugs to eat away the sewage."

Work on the project started in August 2004, with the excavation of 50,000 cu. yds of nearby hill side to allow the construction of new chemical and support buildings, digesters and aerators. Because the plant must remain operating, contractors needed to develop an exact scheduling system to phase the work while not interfering with plant operations.

"Sequencing is a big issue," said project manager Scott Woodrow of Western Summit.

"At an existing plant, you have to phase it a certain way and finish that phase before you can start the next phase. It's all tied together."

Plans call for a June 2007 completion on the $41 million rehabilitation and expansion.

Nearly 50 percent of the project expenses are for new mechanical systems.

One of the major changes will be converting from a chlorine system to a sodium hypo- chlorate system, or bleach, with a 12.5 percent solution. The bleach solution is safer and easier to handle than chlorine. Still, contractors had to use hardware cast from special alloys to reduce corrosion.

"We have to use Hastalloy bolts rather than stainless steel because stainless would just get eaten up," Woodrow said. "We also have to use titanium bolts, and that gets to be expensive."

The project is a concrete intensive job, with crews pouring more than 8,500 cu. yds of 4,500 psi concrete. Rather than use steel, which will corrode, all of the buildings such as the new chemical- storage building and aerators are cast -in -place.

As with many contractors across the west, builders had qualms about cement prices.

"When we bid the job, we had some concerns and quite a bit of discussion about the cement prices," Woodrow said. "We are here for a long duration and we didn't know what kind of pricing we would get down the road."

The project, which is being delivered on a low-bid contract, includes the construction of a new process train that will increase the plant's capacity by 6 MGD. Plans call for another aeration basin

"They may expand this down the road, but right now, this plant will be good for at least 10 years," Michaut said.