Atlantic, IA

Sequencing Batch Reactor Wastewater Treatment Plant

  • Client City of Atlantic
  • Type Wastewater
  • Services Planning, Design, Construction
  • Construction Cost $12.3 Million
  • Project Manager Steve Van Dyke, P.E., BCEE
  • Project Engineer Rob J. Baker, P.E.

CHALLENGE

The city (pop. 7,112) has been treating wastewater at this site since 1940. Existing facilities included preliminary treatment, primary clarification, a carbonaceous trickling filter, intermediate clarification, a nitrification trickling filter, final clarification, anaerobic digestion, and liquid sludge storage.

Flow records and observations by city staff indicated that the collection system conveyed much more flow than what the treatment plant could hydraulically pass or effectively treat during periods of high rainfall. These frequent wet weather flow events resulted in untreated wastewater being bypassed to the East Nishnabotna River. While these facilities received major modifications in 1958, 1970, and 1987, no recent modifications had been made to the treatment plant to deal with the wet weather flow problems.

These hydraulic challenges were compounded with new regulatory requirements mandating that disinfection be implemented. Engineering studies began in 2006 to develop a plan to address these major problems. The city reviewed alternatives for new treatment facilities at potential treatment sites, but the high cost caused the city to reduce the scope of the project to adding new flow equalization, raw wastewater pumping, and disinfection.

There were several challenges with using the existing site. First, the FEMA floodplain model needed to be corrected and modified to demonstrate that the proposed improvement would not cause a substantial increase in the extent of flooding. Second, there was buried rubble and waste where the new facilities were proposed to be built. Third, most of the existing facility would need to be demolished and removed to make room for new treatment facilities. Last, the city needed to acquire some of the properties adjacent to the treatment plant along with obtaining separation distance waivers from nearby property owners. New wastewater treatment facilities cannot be built within 1000 feet of residences without a waiver from the property owner.

Tim Snyder, Atlantic WPCD Superintendent, “I’ve never seen grit washing that is cleaner in the end process and produces such clean grit. And I’ve been fortunate to see several other types and brands of grit washers in action. The difference is unbelievable. It makes you want to ask ‘Where did the grit go?’ because of the drop in volume. Without the presence of organics, the volume is reduced tremendously. And because the wash process is so proficient we were able to go back to using outside haulers. And that takes lots of stress off of our own people.”

Headcell (dry)

Headcell (dry)

SOLUTION

In 2008, FOX Engineering was selected to design these new additions to the existing plant. After some additional facility planning, FOX proposed a plan to replace almost all of the treatment facilities with new facilities for a lower cost than the new plant alternatives previously studied. The new facilities would be constructed next to the existing treatment facilities. One of the benefits to staying on the existing site was that the administration, maintenance, and lab building, as well as two tanks could continue to be used after renovation. Two smaller buildings were kept and used for additional storage space.

By deciding to replace most of the existing facilities, the challenges associated with renovating the existing treatment tanks were eliminated. The project included a new 7 MG earthen flow equalization basin, new interceptor sewers with larger capacity to eliminate sanitary sewer backups on the smaller trunk sewer side, new preliminary treatment building with automated screening and grit removal, screenings and grit washers, raw wastewater sampling, flow metering, and raw pump station in a self-cleaning trench style wet well; new blower building to house new positive displacement blowers for the Sequencing Batch Reactor (SBR) secondary treatment process and aerobic sludge holding tanks, main electrical room, and offseason storage for UV modules; new outdoor emergency power generator; four new, continuous inflow Sequencing Batch Reactors (SBRs) with fine-bubble membrane diffusers, automatic real-time measurement of dissolved oxygen and liquid level in the reactors; new ultraviolet (UV) disinfection system; modified existing final clarifier and sludge storage tank to two aerobic sludge holding tanks; reed bed sludge digestion and dewatering facility; renovated laboratory; and modifications to the 6th Street  pump station.

Atlantic Disinfection

Atlantic Disinfection

Flow Equalization Basin (FEB) liner installation

Flow Equalization Basin (FEB) liner installation

OUTCOME

Design began in 2009 and was finalized in September 2010. Construction occurred from 2010 to 2014, and the project reached final completion on January 30, 2014. The project was funded with a $2 million I-Jobs forgivable loan (grant) and Clean Water State Revolving Fund (CWSRF) loan.

Ron Flory, WWTP operator at the time, stated, “The city of Atlantic now has a very impressive set-up. It has come a long way from a very manual, labor-intensive, chain and bucket system to an integrated and automated, high-tech and clean grit washing component.”

Climber screen in service

Climber screen in service

A panoramic view of the SBRs

A panoramic view of the SBRs

RECOGNITION

FOX Engineering Associates, Inc. and the city of Atlantic are recipients of the 2015 American Council of Engineering Companies (ACEC) Engineering Honor Award (2nd Place) for Engineering Excellence in the Water and Wastewater Category for the

Atlantic Wastewater Treatment Plant.