Impact of scaling on aeration performance of fine-pore membrane diffusers based on a pilot-scale study.

Aeration systems consume a large amount of energy in wastewater treatment plants. Fine-pore membrane diffusers are most commonly used in aeration systems. Scaling and fouling on these membrane diffusers will lead to decreased performance in aeration and increase energy consumption. This pilot-scale study focused on the scaling of the three kinds of fine-pore membrane diffusers under different influent hardness conditions. The results showed that the diffusers were mainly polluted by calcium carbonate scaling. Scaling occurred on the outer surface, orifices and inner surface of the membranes. The dynamic wet pressure (DWP) of ethylene-propylenediene monomer (EPDM), silicone and polyurethane (PU) membrane diffusers increased by 126%, 34% and 304%, respectively, within 50 days when the hardness was 400 mg/L (as CaCO3). However, the increase ratio became obviously slow during the subsequent 60-day operation, indicating a scaling rule of membrane diffusers. Considering that the standard aeration efficiency (SAE) acted as a comprehensive index for judging the aeration performance, the silicone diffuser had better performance than the other two diffusers when severe scaling occurred. This research also provides basic support for the design of membrane diffusers to improve their anti-scaling performance.