Control Strategy And Operation Performance On Partial Nitrification Of High Ammonia Nitrogen Wastewater

Partial nitrification, as the initial and limiting step of PN-Anammox process, determines the denitrification efficiency of the PN-Anammox system. The stable operation and effluent NO₂^--N and NH₄⁺-N ratio in PN process are the key to the coupling process. However, generally, ammonia is the main compositon of nitrogen in wastewater. In order to inhibit nitrite oxidation and realize the accumulation of nitrite, the most important condition is to achieve the enrichment of ammonium oxidizing bacteria（AOB） and limitation、inhibition and washout of nitrite oxidizing bacteria（NOB）. In our study, the partial nitrification was achieved and maintained stably under high ammonia loading（1kg/m3 d） with feed-batch using different control stratege. The nitrification activities from each reactor were determined by execution of aerobic batch tests using fresh activated sludge. The quantities and communities of ammonium oxidizing bacteria（AOB） and nitrite oxidizing bacteria（NOB） were detected by using fluorescence in situ hybridization（FISH）. Some main conclusions are as follows:（1） In SBR1, the temperatue and p H value were controlled at 35±1℃ and 8.0, respectively. The ammonia concentration in the influent was 1000mg/L（1kg/m3d）. DO concentration was maintaining at 0.5¹mg/L. Stable accumulation of NOB was established under the dual inhibition of high FA and low DO concentration. The nitrite oxidizing rate reduced from 28.16 mg NO₂^--N/g MLVSS h to 0.3 NO₂^--N /g MLVSS h. The average effluent NO₂^--N concentration and NO₂^--N/NH₄⁺-N ratio were about 466.45 mg/L and 1, respectively. NO3--N concentration in the effluent was lower than 20mg/L. It was suitable for the influent of Anammox. FISH result indicated that the dominant species of AOB and NOB switched from Nitrosomonas and Nitrospira to Nitrosomonas and Nitrobacter in the enrichment period. During the inhibition period, NOB was washed out gradually, Nitrosomonas dominated in the system. The FISH results can prove the partial nitrification achievement from the view of microbiology.（2） In SBR1, the temperatue and p H value were controlled at 35±1℃ and 7.0, respectively. The ammonia concentration in the influent was 1000mg/L（1kg/m3d）. DO concentration was maintaining at 0.5¹mg/L. Stable accumulation of NOB was established under the dual inhibition of high FNA and low DO concentration. The nitrite oxidizing rate reduced from 12.37 mg NO₂^--N/g MLVSS h to 0.1NO₂^--N /g MLVSS h. The average effluent NO₂^--N concentration and NO₂^--N/NH₄⁺-N ratio were 519.88mg/L and 1.07, respectively. NO3--N concentration in the effluent was lower than 15mg/L. It was suitable for the influent of Anammox. FISH result indicated that the dominant species of AOB and NOB switched from Nitrosomonas and Nitrospira to Nitrosomonas and Nitrobacter in the enrichment period. During the inhibition period, Nitrobacter was washed out gradually, Nitrosomonas dominated in the system.Compare the nitrification performance of the two SBRs under different control strategy, the results showed that AOB activity in SBR1 dropped simultaneously with the reduction of NOB activity. However, the activity of AOB in SBR2 still maintained at a high level. SBR2, which was operated uder the dual inhibition of high FNA and low DO concentration, has the advantages of shorter culturvation period, high biological activity and stable operation. It is more suitable for the achievement of the partial nitrification.