1. Common Causes of High Ammonia Nitrogen (Aerobic Tank Normal but Ammonia Nitrogen High)
Insufficient quantity/low activity of nitrifying bacteria
The sludge age is too short, and the sludge discharge is too fast, causing the nitrifying bacteria to be washed out
The sludge concentration (MLSS) appears normal, but the effective nitrifying bacteria are scarce
2. The dissolved oxygen appears sufficient but is actually insufficient
Nitrification requires DO > 2mg/L; localized hypoxia prevents the reduction of ammonia nitrogen
3. Low pH
Optimal pH for nitrification: 7.0–8.5
◦ pH < 6.5, nitrification is essentially halted
4. The temperature is relatively low
The nitrification rate significantly decreases below 15°C
Winter is the most common season for "normal indicators but elevated ammonia nitrogen levels."
5. Toxic Inhibition
Slaughterhouse wastewater: fats, high salt content, heavy metals, disinfectants
It specifically inhibits nitrifying bacteria, leaving COD unaffected while ammonia nitrogen spikes
6. The carbon-to-nitrogen ratio is too high, and heterotrophic bacteria compete for oxygen
The COD of slaughterhouse wastewater is high, with heterotrophic bacteria consuming oxygen first
Nitrifying bacteria can't compete, ammonia nitrogen won't decrease
II. Consequences of High Ammonia Nitrogen Levels
The ammonia nitrogen level in the discharged water exceeds the standard, failing directly
2. Subsequent deep processing faces significant pressure
3. Insufficient nitrification → Total nitrogen is also difficult to meet standards
4. Increased risk of sludge bulking
5. Return flow to anaerobic/anoxic zones affects nitrogen removal efficiency
6. Eutrophication of water bodies, fines and production restrictions for receiving waters
Basic knowledge of the activated sludge process
3. The 4 Most Critical Areas to Investigate Now (Fastest Diagnosis)
1. pH (Is it slightly acidic?)
2. DO (Whether the terminal aerobic zone is ≥2mg/L)
3. Sludge Retention Time (SRT) (Is it too short, preventing nitrifying bacteria from staying)
4. Water temperature (whether <15°C) How does wastewater treatment degrade pollutants step by step
