The pH in the aerobic tank drops very quickly
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It was originally an AO process, but now the anaerobic tank has been converted into an aerobic tank. The COD level of the incoming water is 400–1500, while the ammonia nitrogen level is 40–70. The COD level in the effluent is in the low twenties, and the ammonia nitrogen level has decreased by about 50%. However, the pH level in the aerobic tank drops rapidly; the pH of the incoming water is 8–9, but it drops to around 5.5 in the aerobic tank. With approximately 200 cubic meters of water entering per day, it takes about 3 packs of 25 kg each of caustic soda to bring the pH back to 7. Is this caused by the digestion process? The pH can still drop without adding alkali. I ask the experts here to explain this – how can it be improved?
It is likely caused by nitration; it is recommended to add soda ash in addition to caustic soda, so that less caustic soda needs to be used and the pH will not fluctuate significantly.
It is likely caused by nitrification; sodium hydroxide can be added in appropriate amounts, or lime can also be used, which makes the cost lower.
Nitration can cause the pH level in the aerobic tank to drop; however, it generally stops when the pH falls to 6.5. A pH level around 5 may be due to inaccurate measurements or the presence of acidic substances – it is necessary to identify the cause as soon as possible.