| Description |
The partial nitritation/anammox (PN/A) process, although found to be an energy and cost-effective process, is not well understood yet. This study was carried out to provide a better understanding of PN/A reactors with suspended and attached growth configurations for treating different waste streams that have potential stress factors. Two PN/A reactors with different configurations were successfully initiated to investigate the difference of suspended growth reactor (SR) and attached growth reactor (AR) in nitrogen removal and the overall microbial composition. During the 300 days of operation, both reactors showed a similar nitrogen removal rate at 35°C and 21°C, and harbored similar communities dominated mainly by three phyla: Chloroflexi, Planctomycetes, and Proteobacteria. To further study the external stress effect on the PN/A performance, the suspended growth reactor was kept at 35°C to 21°C and finally at 13°C.. It was confirmed that lower temperature or sulfide content as low as 5 mgS L-1 could eliminate both Nitrosomonas europaea related ammonium oxidizing bacteria (AOB) and Ca. Brocadia sp. affiliated anammox bacteria (AMX). The activity of AOB was inversely correlated with amoA gene expressions. Just the opposite was found with the hzsA gene expression since it correlated well with the activity of AMX. Additionally, anammox process was applied to treat poststruvite precipitated urine in two-stage and single-stage systems. It was found that coupling the struvite precipitation and PN/A process, 99% recovery of phosphorus and up to 80% removal of nitrogen could be achieved. Compared to the two-stage system, the single-stage reactor had a lower nitrogen removal rate. Also, a pilot-scale PN/A reactor was designed and fabricated to treat reject water in a 300 gal sequencing batch reactor at room temperature. The reactor was successfully started and was able to remove 0.164±0.086 kgNkgVSS-1d-1, indicating a relatively high bacterial activity at room temperature. In conclusion, this study evaluated the feasibility and sustainability of the PN/A system in treating different waste streams containing high ammonium. It provided a better understanding of startup and operation strategies for the full-scale installations of anammox in wastewater treatment plants. |
