Complete Establishment Plan for a Nitrification System Treating High-Ammonia Wastewater (Practical Version)
September 7, 2026
English Translation
The essence of nitrification is the enrichment of autotrophic nitrifying bacteria (ammonia-oxidizing bacteria + nitrite-oxidizing bacteria). These bacteria grow slowly and are highly sensitive to toxicity, temperature, pH, and dissolved oxygen. Therefore, a high-ammonia wastewater system must NEVER be hit with a full-load shock all at once. The process must follow: low-load startup → gradual load increase → stable operation.
I. Prerequisites Before Startup (Meet These First, Then Cultivate the Bacteria)
1. Sludge Source
Priority should be given to inoculating with sludge from a mature aerobic tank (waste sludge from a municipal WWTP / nitrifying sludge from a similar biochemical system). Inoculation amount: control MLSS at 3,000–4,500 mg/L. If no ready-made sludge is available, activated sludge can be slowly acclimated naturally, though this takes a longer period.
2. Toxicity Control of Influent (The Biggest Pitfall of High-Ammonia Wastewater: Free Ammonia (FA) Inhibition)
Free ammonia rule: the higher the pH and the higher the temperature, the stronger the toxicity.
During early startup, do NOT feed raw influent directly — dilute it to lower the influent ammonia concentration;
Control pH at 7.5–8.2 (nitrification produces acid, which automatically lowers pH, so alkalinity must be dosed);
Optimal temperature: 20–30 °C; below 15 °C, the nitrification rate slows down dramatically.
3. Dissolved Oxygen (DO)
Nitrification is an aerobic reaction. Maintain DO in the aerobic tank at 2.0–3.5 mg/L, never below 2 mg/L. Aeration must be sufficient, but excessive aeration must be avoided as it causes sludge aging and disintegration.
4. Alkalinity Reserve (Critical)
Oxidizing 1 g of NH₄-N consumes approximately 7.14 g of alkalinity as CaCO₃. Reserve sufficient alkalinity before startup, and dose soda ash (Na₂CO₃) / sodium bicarbonate (NaHCO₃) daily to prevent a pH crash that would directly kill the nitrifiers.
II. Three-Stage Acclimation to Establish Nitrification (Core Operating Procedure)
Stage 1: Low-Load Acclimation Period (7–15 days)
Dilute the influent and keep the initial ammonia load very low. Ammonia sludge loading rate F/M: 0.02–0.05 kg NH₄-N/(kg MLSS·d)
Pass criteria: effluent ammonia keeps decreasing, and nitrite (NO₂⁻) begins to appear — indicating that ammonia-oxidizing bacteria (AOB) have established.
Phenomenon: short-term nitrite accumulation (a "nitrite peak") is a normal part of the acclimation process.
Stage 2: Gradual Load-Increase Transition Period (10–25 days)
