The researchers used a special process called A/O-MBR to clean up city wastewater. They checked the water before and after treatment to see how well it worked. The results showed that the process removed a lot of harmful stuff like COD, ammonia, nitrogen, and phosphorus from the water. The key factors for success were how long the water stayed in the system, the amount of sludge returned, and the oxygen levels. Keeping the system stable and removing sludge regularly were important to make sure the water was cleaned up properly.