Odor will diminish and public safety will improve when the $16 million, nearly two-year overhaul of the Sam Hobbs Wastewater Treatment Plant begins in earnest next month, Casper's City Engineer Hal Hutchinson said Tuesday.

The joint powers board, which is phasing itself out, oversees the plant and approved the project at its monthly meeting.

Those who use water - meaning everybody - will not notice any changes in their ability to take showers, empty a water bottle or flush during and after the construction.

"The only thing they may notice is the air is going to be a lot cleaner," Hutchinson said.

There will be no increase in user fees because of the capital improvements, either, he said.

The largest aspect of the project will be the installation of a $1 million bubble diffuser aerator, and the necessary buildings and equipment to replace the traditional mechanical system of aerating the sewage sludge to enhance its biodegradation, he said.

The aerator will blow bubbles from the bottoms of the sludge tanks instead of having large paddles introduce water to the sewage, Hutchinson said.

The improvements also will include adding iron salts to the effluent that will bind the sulphur and reduce the odor, he said.

Another major change will eliminate the disinfection process that injects chlorine gas into the treated wastewater before the water returns to the North Platte River, Hutchinson said.

Chlorine gas, a component of the dreaded mustard gas used against troops in World War I, is extremely toxic and requires special handling, he said.

Instead, the treatment plant will install ultraviolet light bulbs to treat the hazardous microbes in the water, Hutchinson said.

The UV light does not kill the microbes, but renders them sterile so they cannot reproduce, he said.

Another major component of the overhaul will replace digesters that cook the sludge, which is transferred to large open pits for air drying at the treatment site, Hutchinson said.

Those pits are the source of much of the odor from the plant, he said.

Instead, the plant will install a large centrifuge to spin the wastewater and separate the water from the sludge, Hutchinson said.

The dried sludge then will be transported to the balefill up the hill from the wastewater treatment plant, and the liquid will be processed, he said.

The cost of the overhaul meant that some additional improvements will not be incorporated at this time, Hutchinson said.

Earlier this year, the joint powers board let bids for the project.

The finalist with the low bid for the basic construction needs was about $10.2 million from Garney Wyoming Inc.

That bid meant some money became available to improve the plant's boiler systems, convert the chlorine building into a shop, and build a maintenance and collection building, Hutchinson said.

The new building will include separate shower and toilet facilities for employees, a safer work environment, and put some distance between the current facility's location so the computer equipment doesn't wear out so soon, he said.

Construction will begin with the installation of contractor's trailers and utility lines next month. The completion deadline is Sept. 1, 2008, Hutchinson said.

Reporter Tom Morton can be reached at (307) 266-0592, or at Tom.Morton@casperstartribune.net.