October 2007, Vol. 19, No.10

Problem Solvers

As Atlanta’s Population Grows, Wastewater Odor Becomes Problem

Problem: Rapid population growth causes strong odors from wastewater operations.
Solution: Install air-filter system using chemisorption to remove gases from the airstream.

The city of Atlanta encompasses more than 342 km² (132 mi²), and the metropolitan area population recently exceeded 5 million. As people continue to migrate to Georgia’s expanding capital, more neighborhoods and retail spaces are rapidly sprouting to accommodate the growth. While the city’s growth was celebrated for its direct relation to higher commerce, residents and city officials did not initially assess the less attractive byproduct of record-breaking expansion: increasing amounts of waste and wastewater, as well as the resulting odorous gases they produce.

The residents were voicing valid concerns about the odors, caused by mercaptans and other gases, escaping the nearby wastewater air-relief tunnels just yards from their homes. Although the new high-value homes and businesses adjacent to Johnson Ferry Road and neighboring Roswell Road are in prime locations, more than two dozen residents began to complain. Residents near the two construction shaft locations were already sensitive to construction issues, and just when the construction ended, a new problem occurred, according to Purafil (Doraville, Ga.), a manufacturer of air-filtration media and systems. The public was threatening to take the city to court to get the odor problem solved. It was not only a legal issue but potentially a public health issue. Financial ramifications were manifested in the drop in home values due to the persistent odors.

Rob Thurman, who works for Lincoln Associates, a Marrietta, Ga.-based heating, air-conditioning, and ventilation company and Purafil representative, was contacted by the City of Atlanta to address the odor issues. Thurman collected airflow measurements from the Johnson Ferry Road site, and an independent environmental analytical laboratory tested the air for gaseous contaminants. Carbonyl sulfide levels were 6.8 ppb by volume (ppbv), and dimethyl sulfide levels were 4.8 ppbv.

To rectify the situation, Purafil and Lincoln Associates worked with the engineering firm of Jordan, Jones & Goulding (Norcross, Ga.) to find the best solution in the shortest possible time. Within 2 days, they decided to use a Purafil Side Access (PSA) unit with CK-12 modules containing one pass of Puracarb® media and one pass of Purafil® CP Blend Select media to remove the odors and resolve the complaints. The media operate by chemisorption — chemical reaction with odorous gas — to remove gases from the airstream. Ductwork routes the odorous air into the scrubber for the media to do their job. A temporary PSA unit removed odors from 170 m³ of air per minute (6000 ft³/min) for 1 year until the permanent unit was constructed and delivered to the location. Temporary units were initially installed, as the customer needed an immediate solution to alleviate the odors while the permanent units were being approved by the city, purchased, constructed, and delivered.

Once the temporary PSA unit at Johnson Ferry Road proved it could remove the pungent odors effectively, the City of Atlanta contacted Purafil and Lincoln Associates 3 months later for additional odor control solutions at Roswell Road. Excessive amounts of hydrogen sulfide and methyl mercaptans were detected, as well as the carbonyl sulfide and dimethyl sulfide detected previously at the Roswell Road site. The urgency of the problem again required quick action. A temporary Double Wall (DW) PSA unit designed to remove odors at 566 m3/min (20,000 ft3/min) was installed in less than 48 hours. The temporary DWPSA was installed for 6 months until a permanent solution could be constructed and delivered. The permanent odor solution at Johnson Ferry Road is a single-pass Purafil ESD Deep Bed Scrubber (DBS) containing patented Odormix™ SP media.

The DBS removes high concentrations of odorous gases from the air-relief tunnel. The customized, built-to-order unit is sized for 170 m3/min (6000 ft3/min). For the Roswell Road No. 2 site, the permanent installation was a unique Parallel Bed Scrubber measuring 4.6 m long by 2.4 m wide by 3.4 m high (15 ft × 8 ft × 11 ft). This unit was constructed specifically to meet to the end user’s needs, and it was the first one of such an immense size. In fact, a 4.5-m × 4.5-m (15-ft × 15-ft) roll-up door had to be installed in the manufacturing plant in order to transport the unit outside.

The city was satisfied with the engineered solutions to the odor problems.

“The units and media at both locations have performed exceedingly well,” said Ade Abon, City of Atlanta watershed project manager. He added that no odor complaints have been received since installation and that the “effectiveness of both systems is quite amazing.” He also said the community immediately noticed the irritating odors had been removed.

For more information about this project, contact Ade Abon, City of Atlanta watershed project manager, at  (404) 925-0323  or aabon@atlantaga.gov . Contact Purafil (Doraville, Ga.) at  (800) 222-6367  , or see www.purafil.com