The effluent from the contact oxidation process is not very clear

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I’m a newbie who has just started working in the environmental protection industry. The unit is used to treat cake wastewater. It is designed to handle 40 cubic meters per day, but in practice it processes around 18 cubic meters; there is no external wastewater. Previously, water was introduced and aeration took place for 6 to 8 hours during the day; since that was the only amount of water available, the system was not in operation from 6 p.m. until 9 a.m. Before the 20th, the appearance of the water and the sedimentation of sludge were all in acceptable condition; things like fleas could hardly be seen in the secondary sedimentation tank. Today, on the 23rd, the COD of the incoming water was around 1100, while in the ABR hydrolysis-acidification tank the COD was 440. The COD of the water leaving the secondary sedimentation tank was 100. These are the data obtained after the adjustments started on the 24th; it has been 3 days now. Previously, the dissolved oxygen level was around 7. For the inlet COD, no measurement tool was available, so it wasn’t measured. It is preliminarily judged that it is caused by a low water inflow load and excessive aeration volume. On the 24th, it was adjusted to 3 hours of water injection per day followed by 2 hours of aeration. The purpose is to increase the load. However, the appearance of the water exiting did not improve. The dissolved oxygen level just won’t rise. It’s been around 0.3. Moreover, there are also some areas around the aeration tank that resemble aged sludge residues with a few white bubbles. The sludge in the secondary sedimentation tank is black. Is my approach to making these adjustments correct? Can the previous water output be restored?