EnviroMix delivers low maintenance aerobic digestion with BioCycle-D process

Eastside Wastewater Treatment Plant in Albertville, Alabama 

Decoupling aeration from mixing optimizes efficiency and process control. 

Owned by the Municipal Utilities Board (MUB), the Eastside Wastewater Treatment Plant in Albertville, Alabama, handles an average daily flow of about 6.0 MGD and serves approximately 20,000 residential customers. In summer 2024, the plant completed a digestion improvements project which included the conversion of two existing anaerobic digesters into aerobic digesters.  

Challenge

Prior to the upgrade, Eastside was operating two parallel solids lines — one with aerobic digestion and the other with anaerobic digestion. The contents of the aerobic and anaerobic digesters were blended, sent through a sludge dryer, and ultimately land applied as Class A biosolids.

David Gilbert, WWTP Assistant Manager, explained, “We had a lot of small parts, pieces, and pumps and constantly recirculated sludge in that old anaerobic digester.” The WWTP needed a low-maintenance solution that simplified operations

Solution

After comparing EnviroMix’s BioCycle-D Optimized Aerobic Digestion Process with a conventional design, the MUB and design engineer, Krebs Engineering, selected the BioCycle-D process for its energy efficiency and straightforward operation.  

By decoupling aeration from mixing, the BioCycle-D process operates on the principle of alternating aerobic and anoxic conditions to optimize digestion and save energy. Through instrument feedback, the controller automatically transitions the cycles from aerobic for volatile solids destruction to anoxic/anaerobic for facilitating denitrification, alkalinity recovery, and energy savings. 

Compressed gas mixing nozzles are interlaced with aeration equipment. 

The MUB staff installed the system themselves with engineering support from EnviroMix, making the overall project more economical. The new process has simplified operations and reduced maintenance. Now, all sludge goes through the aerobic digesters, then through the sludge dryer and on to land application. Anaerobic digestion is no longer utilized.  

“I really can't say anything bad about it. The ease of operation in the digestion process — going from anaerobic to aerobic — it simplified things,” Gilbert said. “It made it safer with less to worry about.”

Results

Compared to the conventional approach, the BioCycle-D process is projected to deliver $90,000 annually in energy savings. The technology reduces operator demands by using instrumentation to adjust the aerobic and anoxic cycle durations based on real-time demands, and the BioCycle-D process has significantly reduced the maintenance burden on the plant. Gilbert stated, “With BioCycle-D, there is less hands-on, everyday housekeeping and maintenance, less equipment that we have to monitor and maintain.” 

The blowers, compressor system, and receiver tank for the aerobic digesters are easily accessible and protected under a canopy.