Performance of SBR with anaerobic effluent to accumulate nitrite for further integration with UASB anammox reactor

Since the 1990s, research on using the anaerobic ammonium oxidation (Anammox) technique to remove nitrogen from wastewater has been advancing quickly. Nitrite (NO₂—N), acceptor of electron for anammox bacteria, must be present in the wastewater in order for the anammox procedure to be used widely. To achieve the optimum concentration of NO₂—N and the potential for integration with anaerobic treatment processes, partial nitrification (P/N) is a critical step. Continuous aeration (Plan 1), nitrite dosing (Plan 2), and Anoxic intermittent aeration (Plan 3) modes were the three alternative techniques that were assessed. In Plan 1, Using synthetic feed, the P/N process’ starting was accomplished. (NH₄ +-N concentration: 50 mg/L) to enrich 30 days of ammonium oxidising bacteria (AOB) with low dissolved oxygen (DO) of 0.1-1.0 mg/L. This was followed by the replacement of the synthetic feed with UASB (Up Flow Anaerobic sludge blanket) effluent (NH₄+-N-50-65 mg/L; COD: 60–80 mg/L and NO₃−N: 0–5 mg/L). As 100% nitrification was shown, strategy 1 was dominated by nitrite oxidising bacteria (NOB) activity. The study also explored the viability of nitrite dosage 30mg/L for 15d without feeding into the reactor with regular mixing in order to obtain the P/N. As the days went on, strategy 2’s granular sludge started to break down, which inhibited AOB and NOB activity. In order to enrich the AOB bacteria, the reactor was further run using strategy 3 feeding. The findings of this study show that the optimum choice for quickly inhibiting NOB bacteria in the seed sludge is a combination of strategies 1 and 2. This work suggests a perfect method for a rapid P/N startup with low DO concentration, producing enough NO2 to meet the necessary N concentration for the anammox process.