Search

For the sake of high efficiency and saving operational cost for high-concentration urea wastewater treatment, a novel two-stage partial nitritation (PN)-anammox process containing simultaneous urea hydrolysis and PN in sequencing batch reactor (SBR) was investigated. Although the influent urea concentration increased from 500 to 1200 mg/L, the SBR simultaneously achieved urea removal efficiency higher than 98% and stable PN with effluent NO 2 −-N/NH 4 +-N ratio of 1.0–1.3 without any extra alkalinity addition. The intracellular hydrolysis was the dominant mechanism for urea removal and persistent free ammonia inhibition on nitrite-oxidizing bacteria was the main reason for nitrite accumulation of 97.92% in SBR. The subsequent anammox reactor showed efficient nitrogen removal performance with average ammonium removal efficiency, nitrogen removal efficiency and maximum nitrogen removal loading rate of 98.08%, 81.45% and 1.05 kg N·m−3·d−1 respectively. High-throughput sequencing results indicated Gemmatimonadetes became the most abundant bacterial phylum related to potential intracellular urea hydrolysis and displayed obvious ammonium-oxidizing bacteria enrichment and nitrite-oxidizing bacteria inhibition in SBR, and the dominant anammox bacteria (Candidatus_Kuenenia) in anammox reactor. The proposed process was proven to be promising for high-concentration urea wastewater treatment, facilitating the sustainable development of the urea industry in the future. [Display omitted] • A novel biological nitrogen removal process for urea wastewater was investigated. • Autotrophic N removal with no alkalinity added was achieved for urea wastewater. • Intracellular urea hydrolysis and stable partial nitritation was integrated in SBR. • 81.45% of total N was removed by anammox with N removal rate of 1.05 kg N·m−3·d−1. [ABSTRACT FROM AUTHOR]

The nitrogen pollution control of liquid-ammonia mercerization wastewater (LMWW) is one of the typical obstacle restricting the sustainability of textile industry. In this study, a 500 kg N/day two-stage partial nitritation/anammox (PN/A) process containing PN reactor filled with zeolite and biofilm anammox reactors was successfully started up in 45 days and operated stably with high shock resistance over one year for LMWW treatment. The large-scale process achieved an average ammonium removal efficiency (94.3 ± 2.3%), total nitrogen removal efficiency (89.4 ± 2.7%) and nitrogen removal rate (1.003 ± 0.386 kg N/m3/day) during one year engineering operation. Simultaneous denitrification was revealed by the contribution of 5.2% total nitrogen removed. High-throughput sequencing results showed that Nitrosomonas was the most dominant genus in PN reactor, and Ca. Anammoxoglobus and Ca. Kuenenia were the functional bacteria for nitrogen removal in anammox reactors. Compared to traditional nitrification-denitrification process, the large-scale process reduced a total operational cost of 46.03 CNY/kg N for LMWW. This study revealed the proposed process was quite reliable with fast start-up and high impact resistance to overcome the obstacle of nitrogen pollution control for LMWW economically and conducive to the sustainable development for textile industry. • 500 kg N/day two-stage partial nitritation/anammox process was initiated in 45 days. • 89.4 ± 2.7% TN removal was achieved at N removal rate of 1.003 ± 0.386 kg N/m3/day. • The process showed high shock resistance facing NH 4 +-N ranging at 1000-500 mg/L. • The large-scale process reduced a total operational cost of 46.03 CNY/kg N. [ABSTRACT FROM AUTHOR]

The adsorption process for low concentration phosphorus wastewater treatment has advantages of simple convenience, stable performance and less sludge, while most of current adsorbents fail to be separated for reuse. Meanwhile, few people pay attention to the removal of low concentration phosphorus from tail water by adsorbents. In this study, a newly efficient Fe–Mg–Zr layered double hydroxide beads were prepared by simple in-situ crosslinking method and applied for low concentration phosphorus adsorption from real tail water. The maximum adsorption capacity of Fe–Mg–Zr beads was 21.61 mg/g, showing more practical application value for phosphorus removal. Fixed bed experiments showed that 5.0 g adsorbent could removed 2.12 mg phosphorus from tail wastewater containing 1.03 mg/L phosphorus. The beads adsorbent can be reused with excellent adsorption performance even after five cycles of adsorption-desorption operation. After detailed analyses, it was found that ligand exchange and ion exchange were the dominant mechanisms for phosphorus adsorption by this beads. Overall, the material has the advantages of simple preparation, good adsorption performance, easy separation and recycle, indicating a great potential for low concentration phosphorus wastewater treatment. [Display omitted] • Fe–Mg–Zr layered hydroxide beads was prepared for efficient low P adsorption. • The beads could be easily separated and reused for real low P wastewater. • P removal mechanisms by the beads were ligand exchange and ion exchange. [ABSTRACT FROM AUTHOR]

In order to assess the performance of anaerobic ammonium oxidation (anammox) bioreactors, it is necessary to study the stoichiometry of the anammox reaction and pH. This study focused on the effect of the hydraulic retention time (HRT) on the effluent pH in anammox-upflow anaerobic sludge blanket (UASB) bioreactors. Anammox-UASB bioreactors with and without a recirculation system were used to investigate the effluent pH and bioreactor performance. It was concluded that under varying HRT conditions, the decrease in effluent pH did not indicate the deterioration of nitrogen removal, but did indicate that the nitrogen removal efficiency was reduced owing to a sudden increase in the nitrogen loading rate resulting from the decrease in HRT. Moreover, the results showed that the HRT directly affected the concentration of OH−, which affected the increase/decrease in effluent pH. This study demonstrated that effluent pH is a more powerful tool than previous techniques used to assess bioreactor performance. We suggest that the effluent pH could be used for preliminary assessment. • The decrease in effluent pH does not always indicate the deterioration of nitrogen removal. • The clear decrease in the effluent pH showed that the NRE decreased. • The change in the effluent pH was related to the NRE rather than the NRR. • Two UASB reactors with and without recirculation were used for effluent pH and NRE investigation. • The effect of the HRT on the effluent pH was investigated. [ABSTRACT FROM AUTHOR]