[Characteristics of ANAMMOX Granular Sludge and Differences in Microbial Community Structure Under Different Culture Conditions].

Anaerobic ammonium oxidation (ANAMMOX) granular sludge was cultured during different operating conditions by an expanded granular sludge bed (EGSB) reactor and up-flow anaerobic sludge bed (UASB) reactors, and the characteristics of the granular sludge and microbial community were compared. The results showed that the flocculent ANAMMOX sludge can be granulated after being operated for 384 days by the EGSB and UASB reactors. The average particle size reached 1.17 mm and 1.21 mm, respectively. The particle size ratio of each range (<0.2, 0.2-1.5, 1.5-3, and>3 mm) was 6.06%, 60.05%, 25.25%, and 8.64% in the EGSB reactor, and 7.40%, 58.90%, 32.04%, and 1.66% in the UASB reactor, respectively. The results of scanning electron microscopy showed that the bacterial flora during different operating conditions were mainly Brevibacterium and Cocci aggregates. High-throughput sequencing results showed that the Shannon index of the EGSB reactor was 7.52, higher than the 7.18 of the UASB reactor on day 384; Proteobacteria was the main phylum of the sludge at each stage, and Planctomycetes increased from 3.30% to 12.30% in the EGSB reactor and 13.30% in the UASB reactor on day 384. The main ANAMMOX genera in the EGSB reactor were Candidatus Brocadia, accounting for 7.53%, followed by Candidatus Kuenenia accounting for 1.61%, whereas in the UASB reactor, Candidatus Kuenenia was the dominant anaerobic ammonia genus, accounting for 7.54%, followed by Candidatus Brocadia, which accounted for 3.69%. The proportion of dominant species was related to the change in environmental factors. The proportion of Candidatus Brocadia was positively correlated with the up-flow rate and nitrogen removal rate (NRR), but negatively correlated with hydraulic retention time (HRT). Candidatus Kuenenia was positively correlated with nitrogen removal efficiency (NRE), NRR, and HRT, but negatively correlated with the up-flow rate.

[Process Control and Operation Optimization of PN-SAD Coupling Process Based on SBR-ABR].

This study uses three different operating phases for a sequencing batch reactor (SBR) combined with an anaerobic baffled reactor (ABR) to determine the effect of deep nitrogen and carbon removal by the "partial nitrification-anaerobic ammonium oxidation combined denitrification" (termed PN-SAD) reaction. The effluent of the SBR (NO2--N/NH4+-N ratio range of 1-1.32) was accessed directly to the single compartment ABR anammox system in phase Ⅰ. The results showed that although the anammox reaction was stable, the combined process total nitrogen (TN) removal efficiency was<80%, and the TN concentration of effluent was~20 mg·L-1. In order to increase the denitrification function in the ABR, denitrifying sludge was added to the third compartment of the ABR in phase Ⅱ. We found that the TN removal efficiency of the coupling reaction was still low. An organic carbon source should be supplied in the latter stage of anammox if deep nitrogen removal is required. Therefore, in phase Ⅲ, the effluent of the SBR (NO2--N/NH4+-N ratio of ~5) was mixed with the partial raw water (mixed water NO2--N/NH4+-N ratio of ~1.4; C/N ratio of 2.5). The mixed water was connected to the single compartment of the ABR. The PN-SAD system not only achieved a good matrix ratio at the anammox stage, but also provided a good carbon source for denitrification. The chemical oxygen demand (COD) concentration of the effluent in the whole process was 50 mg·L-1, the TN concentration of the effluent was<6 mg·L-1, and the TN removal efficiency was 95%. We conclude that the stable operation of the combined PN-SAD reaction provides the basis for deep nitrogen and carbon removal using the combined SBR-ABR process.

[Effect of C/N and Sludge Concentration on the pH-Regulated Nitrosation System].

pH is one of the most important means of control for the realization and stability of the nitrosation system. To study the change rule of pH values of the nitrosation system and the influence of pollution removal and transformation at different pH under the conditions of different C/N (0, 1, 2, 3,4) and sludge concentrations (sludge amount:water content was 1:6, 1:3, 1:1), batch tests were conducted with tapered bottles using sodium acetate as the carbon source and inoculated with mature nitrosation sludge. The results showed that the higher the C/N, the higher the pH increment and the denitrification efficiency at the same sludge concentration. At the same C/N, a higher sludge concentration corresponded to a smaller pH increment but a higher denitrification efficiency. The removal and transformation of carbon and nitrogen was highly correlated with pH changes in the reaction system, and the denitrification and nitrosation reactions were in sequence. Throughout the operational period of the system, as pH increased, the specific organic matter removal rate was 7-16 times as much as when pH decreased. However, as pH decreased, the specific ammonia oxidation rate (SAOR) was 1-20 times that of when pH increased. When pH was less than 6.1, the system lost its ability to oxidize ammonia-nitrogen. The highest removal efficiency of carbon and nitrogen in the system was achieved when C/N was 4. Ammonia transformation 80% COD removal at the three sludge concentrations took 480, 350, and 300 min, respectively. Under different conditions, the proportion of nitrosation in the system remained above 50% and the concentration of NO3--N remained below 5 mg·L-1, which indicated that the system was dominated by nitrosation.