Evaluation of upgrading a full-scale activated sludge process integrated with floating biofilm carriers

This study evaluated the performance of a full-scale upgrade of an existing wastewater treatment plant (WWTP) with the intermittent cyclic extended aeration system (ICEAS), located in Qingdao, China. The ICEAS system was not able to meet effluent standards; therefore, a series of modifications and control strategies were applied as follows: (1) floating plastic carriers were added to the tank to aid biofilm formation; (2) operation parameters such as mixing and aeration time, feeding rate, and settling time were adjusted and controlled with a real-time control system; (3) a sludge return system and submersible water impellers were added; (4) the aeration system was also improved to circulate carriers and prevent clogging. The modified ICEAS system exhibited efficient organic and nutrient removal, with high removal efficiencies of chemical oxygen demand (89.57 ± 4.10%), NH₄⁺-N (95.46 ± 3.80%), and total phosphorus (91.90 ± 4.36%). Moreover, an annual power reduction of 1.04 × 10⁷ kW·h was realized as a result of these modifications.