Illustration of granular activated carbon treatment system Credit: Credit: Hazen and Sawyer

The Albemarle County Service Authority has chosen the cheaper of two filtration options being studied for use in the Charlottesville-Albemarle drinking water supply.

The Rivanna Water & Sewer Authority has been evaluating plans to implement a granular-activated carbon filtration system since July 2012, when the approach was selected over the use of chloramines.

“We are going to go from very high-quality water to super-very high-quality water, if you want to try to find some superlatives,” said Thomas L. Frederick Jr., the RWSA’s executive director. “We chose granular-activated carbon, which absorbs natural organic matter … whereas other technologies, like chloramines, add another chemical …”

The project’s upfront capital costs of $17.3 million are $2.2 million less than a competing option. Separately, the water treatment plants in Scottsville and Crozet are being upgraded to use granular-activated carbon.

The RWSA must upgrade its water treatment system by October to comply with more stringent federal regulations. With significant public opposition to the introduction of chloramines, the Albemarle Board of Supervisors and Charlottesville City Council unanimously agreed last year to evaluate the costs of multiple carbon treatment options.

The full treatment option, which would cost $19.5 million and was not selected, would send all urban area drinking water through a granular-activated carbon filtration system.

Last year, Frederick recommended the study of a hybrid option to lower costs. It would treat portions of the water supply with carbon filtration systems, then blend it with regularly treated water.

Frederick told the ACSA board at its meeting Thursday that very few communities in the country are using granular-activated carbon because of its significant costs vs. chemical treatment.

“Those few that do have gone full-scale,” Frederick said. “There is one we are aware of in Georgia that is trying something similar to [the hybrid approach] we are talking about, but they have not implemented it yet.”

He said consultants with Hazen and Sawyer had to develop their own scientific analysis and computer models to evaluate the options for the RWSA.

“We hoped when we initiated the study of the hybrid approach that we would come up with a significant [cost] difference to present to you,” Frederick said. “Well, it didn’t work out that way and that sometimes happens when you are pushing that envelope, that you don’t get the results you are hoping for.”

Besides the $2.2 million cost difference for upfront capital equipment, Frederick said there are not significant qualitative or quantitative differences between the two approaches.

“I can stand behind either one,” Frederick said.

Annual operating costs for the hybrid approach are projected at $920,000. The average cost increase in a household water bill will be $3.29 per month.

Board member and Albemarle Supervisor-elect Liz Palmer asked if the hybrid system could be upgraded to full treatment in the future. Frederick said the system was modular and could be expanded, though that would be more expensive than doing it all at once.

Board member Bill Kittrell captured the board’s sentiment.

“It’s flexible and you are saving $2.2 million in capital costs,” Kittrell said.

Frederick said that after he provided a similar report to the City Council, the city also was supportive of the hybrid approach. The RWSA board is expected to make a final decision at a meeting in December.