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The efficient and economical disposal of urea wastewater for promoting wastewater reuse, are still tough obstacles for the sustainable development of urea industry. In order to explore newly efficient and economical alternative for urea wastewater treatment, a novel one-stage autotrophic nitrogen removal reactor (submerged aerated biological filter, SABF) simultaneously combining with urea hydrolysis, partial nitritation (PN) and anammox was carried out and stably operated for 126 days. The SABF reactor not only presented excellent urea removal efficiency (˃ 99.5%) with average effluent urea concentration of 0.83 mg/L to meet reuse standard, but also achieved high nitrogen removal loading, ammonium removal efficiency and total nitrogen removal efficiency as 1.5 kg N/(m3·d), 89.46% and 77.09%, respectively. The urea removal mechanism was proven as the intracellular urea hydrolysis, which was conducive to accomplish the persistent free ammonia (FA) inhibition on nitrite-oxidizing bacteria for stable PN and guaranteed total nitrogen removal by anammox. High-throughput sequencing analysis results revealed that Nitrosomonas accounting for 15.92% should be responsible for excellent urea hydrolysis and PN performance and Candidatus_Brocadia with relative abundance of 1.63% was the main anammox bacteria for further nitrogen removal in the SABF reactor. The proposed process showed significant advantages of extremely low operational cost and high removal efficiency with recyclable effluent for urea wastewater treatment. This study provided a novel and superior alternative for the cleaner production of urea manufacturing enterprises, which can well alleviate the stress of urea wastewater treatment and further benefit the sustainable development of urea industry in the future. [Display omitted] • A novel one-stage nitrogen removal process for urea wastewater was developed. • Intracellular urea hydrolysis, partial nitritation, anammox were integrated in SABF. • A high N removal rate of 1.5 kg N/(m3·d) was achieved at 30 °C. • Effluent urea concentration was stably lower than 1 mg/L. [ABSTRACT FROM AUTHOR]

Cost-effective nitrogen removal from iron oxide wastewater is a limitation in the sustainable development of the iron oxide manufacturing industry. Two processes, namely, complete nitritation (in a sequencing batch reactor with zeolite powder, ZSBR) combined with traditional denitrification and partial nitritation (in the same ZSBR) combined with anaerobic ammonium oxidation (anammox), were successfully developed and then compared for long-term nitrogen removal from iron oxide wastewater. Stable and complete nitritation with nitrite accumulation ratio (NAR) > 95.1% was achieved in the ZSBR. Nitrogen removal rates (NRRs) of up to 4.083 ± 0.727 kg N/m3/d were obtained subsequently in a denitrifying upflow sludge blanket reactor at an influent chemical oxygen demand/total nitrogen ratio of 2.5. Efficient partial nitritation was also achieved with effluent NO 2 −–N/NH 4 +–N ratios of 1.1–1.5 and NAR > 92.0% in the ZSBR, with a final NRR of 1.175 kg N/m3/d in the subsequent anammox reactor. The addition of zeolite achieved persistent free ammonia inhibition on nitrite oxidizing bacteria in the ZSBR and resulted in efficient and controllable nitrite accumulation. The total chemical cost in the complete nitritation–denitrification process was 3.32 USD/kg NH 4 +–N, which was 1.14 times higher than that in the partial nitritation–anammox process. Both processes were effective and reliable in achieving nitrogen removal from iron oxide wastewater for the sustainable development of the iron oxide manufacturing industry. [Display omitted] • Two novel nitrogen removal processes were compared for iron oxide wastewater. • Both complete nitritation and partial nitritation (PN) were effectively achieved. • Free ammonia inhibition on nitrite oxidizing bacteria was crucial for nitritation. • Nitritation-denitrification consumed 2.14 times the chemical cost of PN-anammox. [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 coupled process of thiosulfate-driven denitrification (NO 3 −→NO 2 −) and Anammox (TDDA) was a promising process for the treatment of wastewater containing NH 4 +-N and NO 3 −-N. However, the high concentration of SO 4 2− production limited its application, which needs to be alleviated by an economical and effective way to promote the application of TDDA process. In this study, TDDA process was started in a relatively short time by stepwise replacing nitrite with nitrate and operated continuously for 146 days. Results presented that the average total nitrogen removal efficiency of 82.18% can be acquired at a high loading rate of 1.98 kg N/(m3·d) with maximum nitrogen removal efficiency up to 87.04%. It was observed that the increase of S/N ratio improved the denitrification efficiency and slightly inhibit the Anammox process. Batch tests showed that Sulfammox process appeared in TDDA process under certain conditions, further contributing 2.59% nitrogen removal and 10.46% sulfur removal (14.42 mg/L NH 4 +-N and 37.68 mg/L SO 4 2--S were removed). This finding was mainly attributed to the reduction of sulfate in TDDA system to elemental S0 or HS−, which subsequently was used as an electron donor to realize the recycling of sulfate (SO 4 2--S) pollutants and promote the sulfur-nitrogen (S–N) cycle. High-throughput analysis displayed that Anammox bacteria (Candidatus_Kuenenia), Sulfur-oxidizing bacteria (Thiobacillus) with relatively high abundance of 5.37%, 7.74%, respectively, guaranteeing the excellent nitrogen and sulfate removal performance in the reactor. The enrichment of phyla Chloroflexi (31.79%), Proteobacteria (31.82%), class Ignavibacteriales (10.55%), genus Planctomycetes (13.57%) further verified the exitence of Sulfammox process in the TDDA reactor. This study provides a new perspective for the practical application of TDDA in terms of reducing the production of high concentration SO 4 2− and saving operational cost and strengthening deeply nitrogen removal. • The TDDA was started in a short time via stepwise replacing nitrite with nitrate. • The Highest TN removal (87.04%) was acquired at the NLR of 1.98 kg N/(m3·d) in TDDA. • Sulfammox process appeared in TDDA process which accelerated S–N cycle of system. • The contributions of various nitrogen and sulfur removal pathways were investigated. • The enrichment of Ignavibacteriales (10.55%) verified the exitence of Sulfammox. [ABSTRACT FROM AUTHOR]

The coupled process of thiosulfate-driven denitrification (NO 3 −→NO 2 −) and Anammox (TDDA) was a promising process for the treatment of wastewater containing NH 4 +-N and NO 3 −-N. However, the high concentration of SO 4 2− production limited its application, which needs to be alleviated by an economical and effective way to promote the application of TDDA process. In this study, TDDA process was started in a relatively short time by stepwise replacing nitrite with nitrate and operated continuously for 146 days. Results presented that the average total nitrogen removal efficiency of 82.18% can be acquired at a high loading rate of 1.98 kg N/(m3·d) with maximum nitrogen removal efficiency up to 87.04%. It was observed that the increase of S/N ratio improved the denitrification efficiency and slightly inhibit the Anammox process. Batch tests showed that Sulfammox process appeared in TDDA process under certain conditions, further contributing 2.59% nitrogen removal and 10.46% sulfur removal (14.42 mg/L NH 4 +-N and 37.68 mg/L SO 4 2--S were removed). This finding was mainly attributed to the reduction of sulfate in TDDA system to elemental S0 or HS−, which subsequently was used as an electron donor to realize the recycling of sulfate (SO 4 2--S) pollutants and promote the sulfur-nitrogen (S–N) cycle. High-throughput analysis displayed that Anammox bacteria (Candidatus_Kuenenia), Sulfur-oxidizing bacteria (Thiobacillus) with relatively high abundance of 5.37%, 7.74%, respectively, guaranteeing the excellent nitrogen and sulfate removal performance in the reactor. The enrichment of phyla Chloroflexi (31.79%), Proteobacteria (31.82%), class Ignavibacteriales (10.55%), genus Planctomycetes (13.57%) further verified the exitence of Sulfammox process in the TDDA reactor. This study provides a new perspective for the practical application of TDDA in terms of reducing the production of high concentration SO 4 2− and saving operational cost and strengthening deeply nitrogen removal. • The TDDA was started in a short time via stepwise replacing nitrite with nitrate. • The Highest TN removal (87.04%) was acquired at the NLR of 1.98 kg N/(m3·d) in TDDA. • Sulfammox process appeared in TDDA process which accelerated S–N cycle of system. • The contributions of various nitrogen and sulfur removal pathways were investigated. • The enrichment of Ignavibacteriales (10.55%) verified the exitence of Sulfammox. [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]