Phenix City WWTP Biosolids Handling & Biogas System Improvements
Phenix City Utilities Department, AL
The City of Phenix City operates a 7.75 mgd wastewater treatment plant (WWTP) that discharges treated effluent to the Chattahoochee River. The Department of Utilities hired Constantine in 2013 to evaluate the WWTP performance, which was struggling to meet discharge limitations. The plant was exceeding NPDES effluent limits for Total Ammonia Nitrogen, BOD, and toxicity, typically caused by high plant solids, insufficient aeration, inadequate digestion capacity, and failure to sample correctly. As part of the plant evaluation and optimization completed in 2013-2014, Constantine identified significant deficiencies associated with the plant process treatment components, including the existing anaerobic digestion operations, and completed condition assessments and process evaluations using Biowin modeling. The evaluation identified the need for several improvements, including headworks upgrades for grit removal; trickling filter recycle; aeration capacity increase; new aeration blowers; primary sludge pumping improvements; primary sludge and waste sludge thickening; anaerobic digester tank maintenance and mixing improvements; biogas collection and conditioning improvements; secondary sludge recycle improvements; belt press filtrate handling; chemical addition improvements for alkalinity and pH control; monitoring and control system improvements; and electrical distribution and emergency power.
The completed improvements project incorporated scrubbing technology and operations to specifically target and remove siloxanes, which also reduced the release of siloxanes into the environment. The much improved biogas quality is now used as renewable energy for the digestion boilers. Improvements at the plant resulted in proper operation and compliance by 2017.