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January 29, 2008

Odor controls at wastewater treatment facility will be costly

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Ron Taylor (right) of Hazen and Sawyer presents the odor control report while Woolen Mills residents Bill Emory (left) and Karl Ackerman (center) listen

A plan to eliminate virtually all odors from the urban area's waste water treatment plant could cost as much as $32.3 million in capital costs, according to a report presented to the Board of Directors of the Rivanna Water and Sewer Authority (RWSA).

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The report was commissioned after the RWSA continued to receive complaints from residents about odors emanating from the vicinity of the Moores Creek Wastewater Treatment Plant. In February of last year, the RWSA closed down a composting facility as the first step in addressing complaints from residents of the city's Woolen Mills and Belmont-Carlton neighborhoods. A report from the firm Hazen and Sawyer identified the closure as the most cost-effective way of reducing the odor.

Despite a reported drop in the number of complaints in the summer of 2007, the second study was commissioned to identify additional methods of removing odors.  The RWSA heard this report at their monthly meeting on January 28, 2008.

Hazen and Sawyer, a company that specializes in wastewater management, is also working with RWSA staff to design mandated upgrades to Moores Creek to comply with Department of Environmental Quality (DEQ) efforts to clean up the Chesapeake Bay watershed.

Prior to the presentation of the report, Woolen Mills resident Karl Ackerman told the Board that the odor problem affects the whole area serviced by the RWSA. He said this past fall was particularly awful because odors are worse in drought conditions. Ackerman pleaded with the RWSA Board to solve the problem no matter the cost, and pointed out that much of the growth in wastewater and sewage anticipated to be treated at the plant in coming years will come from County homes.

“If builders, new residents and County officials expect to send all of this new sewage to Moore's Creek, we who live beside it will only accept it odor-free,” Ackerman said. “We breathe the air fouled by the biological waste of the greater community.” He called for a surcharge on all new homes built in the County to pay for the option. 

According to this second Hazen and Sawyer report, Moores Creek currently does not have any specific odor control mitigation steps, besides what is called for in the wastewater industry's best practices. The review identified three levels of odor removal that could possibly be attained.


Option 1 would guarantee a 99.7% mitigation of 99.7%, which would translate to an estimate of at least an average of one day per year where the plant could be smelled by its neighbors. Option 2 would include one less scrubber, and would provide 99% removal of odor. Option 3 would provide 95% removal and would cost $11.2 million.

“There is a significant diminishing of returns as you try to get to higher and higher percents of removal,” said Ron Taylor of Hazen and Sawyer. He said only a small number of wastewater treatment plants in the United States provided any specific odor control problems, and those that do only provide 95 percent removal of odors.  The report states that “it is cost prohibitive to design a system that would guarantee that odors will never migrate off site.”

Technologies that might apply to Moores Creek include wet scrubbers, carbon absorption units, bio-filtration, and thermal oxidizers.

Option 1 would provide 99.7% removal of odor (Source: Hazen and Sawyer)

Option 1 would include completely enclosing various pump stations and holding tanks. An entirely new septage receiving station would be constructed. Chemicals would be used to scrub the sewage as it proceeds through the grit removal facilities, gravity thickeners and digesters. Option 1 also features a $10 million dollar scrubber for the holding ponds.

If the RWSA was to proceed with odor control, Taylor recommended using a phased approach in which any odor mitigation procedures would be added while the nutrient removal upgrades are performed. Major capital costs in Taylor's suggested phase 1 would include the new septage station, a new scrubber facility for the north side of the plant, as well as the covering of several pools and basins that are currently open to the air.

“The first phase would address those areas that are most likely to propagate odors off site,” Taylor said.

Phase 1 would cost $6 million, which is exactly how much RWSA Executive Director Tom Frederick said is budgeted for odor mitigation for this year.

City Public Work Director and RWSA Board member Judy Mueller said she wanted her engineers to review the report before making a decision. City Manager Gary O'Connell said he wanted someone to schedule time to explain these possibilities to neighborhood residents.

The Board deferred action until February.


  • The Board also heard details on its proposed five-year 2008-2013 Capital Improvement Program, which for the first year includes costs associated with the implementation of the Community Water Supply Plan. The RWSA is now waiting to find out if the DEQ will schedule a formal public hearing to consider the draft permit for the new Ragged Mountain Dam, a key component of the plan. Charlottesville Tomorrow will cover this story in a separate article.
  • Frederick said computer modeling shows area reservoirs are likely to refill before late April. However, he said residents should continue to voluntarily conserve water to ensure that the reservoirs won't quickly empty if dry conditions persist. The drought warning was reduced to a drought watch earlier this month.
  • The Board  passed a resolution calling on the Governor and the General Assembly to not renege on funding the Water Quality Improvement Fund, which the RWSA is counting on for $16 million to pay for a good portion of the upgrades to Moores Creek Wastewater Plant.

Sean Tubbs


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