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Riparian zones are considered as an effective measure on preventing agricultural non-point source nitrogen (N) pollution. However, the mechanism underlying microbial N removal and the characteristics of N-cycle in riparian soils remain elusive. In this study, we systematically monitored the soil potential nitrification rate (PNR), denitrification potential (DP), as well as net N 2 O production rate, and further used metagenomic sequencing to elucidate the mechanism underlying microbial N removal. As a whole, the riparian soil had a very strong denitrification, with the DP 3.17 times higher than the PNR and 13.82 times higher than the net N 2 O production rate. This was closely related to the high soil NO 3 - O production rate near the farmland edge were relatively low. In terms of N-cycling microbial community composition, the taxa of denitrification, dissimilatory nitrate reduction, and assimilatory nitrate reduction accounted for a large proportion, all related to NO 2 O production rate near the farmland edge were relatively low. In terms of N-cycling microbial community composition, the taxa of denitrification, dissimilatory nitrate reduction, and assimilatory nitrate reduction accounted for a large proportion, all related to NO 3 - -N reduction. The N-cycling microbial community in waterside zone showed obvious differences to the landside zone. The abundances of N-fixation and anammox genes were significantly higher in the waterside zone, while the abundances of nitrification (amoA&B&C) and urease genes were significantly higher in the landside zone. Furthermore, the groundwater table was an important biogeochemical hotspot in the waterside zone, the abundance of N-cycle genes near the groundwater table was at a relative higher level. In addition, compared to different soil depths, greater variation in N-cycling microbial community composition was observed between different profiles. These results reveal some characteristics of the soil microbial N-cycle in the riparian zone in an agricultural region and are helpful for restoration and management of the riparian zone., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Inc.)

The inhibition of over-accumulated nitrite on anaerobic ammonium oxidation (anammox) activity has been widely reported and intensively studied. Surprisingly, there are limited researches on the strategy to deal with nitrite inhibition. In this work, to eliminate nitrite inhibition in an up-flow granular anammox reactor, acetate dosing (600 mg COD L -1 ) and simultaneous acetate and denitrifying sludge dosing (600 mg COD L -1 and 1.4 g dry weight L -1 ) were implemented to temporarily activate microbial denitrification to reduce nitrite, respectively. In two strategies, reactor nitrogen removal and extracellular ATP were resumed to initial levels, while the recovery ratios of intracellular ATP and nitrite removal rate (67.1% and 15.6 mg N h -1 ) of the former were higher than those (52.5% and 11.2 mg N h -1 ) of the latter, indicating acetate dosing was more qualified to nitrite removal. Meanwhile, although a decrease of the dominated Ca. Brocadia from 30.7 to 25.8% was not reversed through high-throughput sequencing, acetate dosing did not cause denitrifiers proliferation. As easily implemented acetate dosing was as effective as direct discharge of inhibitory nitrite as the control strategy, it was recommended when nitrite inhibition happened. Additionally, an irregular behavior of nitrate overproduction via nitrite oxidation and the drastic increase of extracellular ATP were detected and proposed as the response of AnAOB to nitrite inhibition., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

Two-stage anoxic/oxic combined membrane bioreactor (A/O-A/O-MBR) process was used to treat leachate generated from Shenyang Laohuchong landfill, and the effect of hydraulic retention time (HRT) was studied. A long HRT of 9 d and a short HRT of 5 d showed negative effect on the stability of process, resulting in a higher organic concentration of effluent than that with a HRT of 7 d, while the highest removal of chemical oxygen demand (COD), ammonia (NH 4 -N) and total nitrogen (TN) were achieved with a HRT of 7 d, which was 82.4%, 99.1% and 75.3% respectively. The analysis of microbial communities by high-throughput sequencing showed that phyla Proteobacteria and Bacteroidetes were the dominant bacteria, which accounted for 36.63-42.39%, 29.21-38.66%, respectively. For genus classification, the most representative of Ferruginibacter, unclassified-Saprospiraceae and Nitrosomonas accounted for 20.76-35.11% totally. The other communities, including Nitrobacter, Planctomyces, Rhodobacteraceae and Nitrospirae, were also developed for organic degradation and denitrification.+ -N) and total nitrogen (TN) were achieved with a HRT of 7 d, which was 82.4%, 99.1% and 75.3% respectively. The analysis of microbial communities by high-throughput sequencing showed that phyla Proteobacteria and Bacteroidetes were the dominant bacteria, which accounted for 36.63-42.39%, 29.21-38.66%, respectively. For genus classification, the most representative of Ferruginibacter, unclassified-Saprospiraceae and Nitrosomonas accounted for 20.76-35.11% totally. The other communities, including Nitrobacter, Planctomyces, Rhodobacteraceae and Nitrospirae, were also developed for organic degradation and denitrification., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

A novel system integrating Johannesburg (JHB) and sulfur autotrophic denitrification (SAD) process was proposed with the purpose of efficient removal of organic matter and nitrogen when treating low COD/TN ratio municipal wastewater. The characteristics and fate of dissolved organic matter in the Johannesburg-Sulfur autotrophic denitrification (JHB-SAD) system were investigated using excitation–emission matrix fluorescence spectroscopy with a parallel factor analysis. Three components were identified including tryptophan-like (componentC1), tyrosine-like (componentC2), and fulvic-like (componentC3) materials. The tyrosine-like and tryptophan-like materials, which were more abundant than fulvic-like materials, were the dominant components of the raw municipal wastewater in Shenyang North Wastewater Treatment Plant. In the JHB-SAD system, the tyrosine-like and tryptophan-like materials were more efficiently removed than the fulvic-like materials, and the removal efficiencies of the three components were 80.8% (tryptophan-like materials), 72.5% (tyrosine-like materials), and 33.4% (fulvic-like materials), respectively. Furthermore, the removal performance of the three components varied in the different zones of the JHB-SAD system. The tryptophan-like and fulvic-like materials were removed in the pre-anoxic, anaerobic, and aerobic zones. The tyrosine-like materials were mainly degraded in the anoxic and aerobic zones; then, they were released by the bacteria in the SAD reactor. In addition, the tryptophan-like materials had a very significant positive linear correlation with the concentrations of soluble chemical oxygen demand. [ABSTRACT FROM PUBLISHER]

In order to investigate the effect of operational mode, temperature, and planting on the performance of tidal flow constructed wetland (TFCW), four lab-scale units were operated in parallel experiments. They were operated in three cycles d−1tidal flow mode with planting (3TF+P), three cycles d−1tidal flow mode without planting (3TF), one cycle d−1tidal flow mode with planting (1TF+P), and continuous flow mode with planting (CF+P), respectively. The results demonstrated that the multi-cycle tidal flow operational mode promoted the biofilm growth and pollutant removal with the low relative clogging coefficient (RCC) of 21.42% during the whole experimental period. The average COD,-N, and-P area removal rate in 3TF+P reached 18.00, 2.38, and 0.24 g m−2 d−1, respectively. Meanwhile, the influence of low temperature on the performance of TFCW in the winter was partially compensated by the multi-cycle operational mode, which made the performance of TFCW more stable than that of other systems under temperature variation. PlantingCanna indicaL.(Cannaceae) led to an increase in average area removal rate of N with 24.17%. The net uptake of N by planting was 0.35 g m−2 d−1, which accounted for 17.95% of the total nitrogen removal. Besides the direct uptake, the combination of aerobic zone close to rhizosphere and anaerobic zone around rhizosphere may also play an important role in the nitrification–denitrification process. The direct P removal byCanna indicaL. (Cannaceae) was quantified as 0.01 g m−2 d−1, which only accounted for 4.17% of the-P removal. [ABSTRACT FROM AUTHOR]

Dry-spun acrylic fiber (DAF) is typically synthesized by the polymerization of acrylonitrile (AN) monomers under high-temperature conditions. DAF manufacturing factories produce DAF polymerization and AN manufacturing wastewaters that are complex, toxic and bio-refractory. In this study, a bench-scale combined Fenton-sequencing batch membrane bioreactor (SBMBR) process was developed for DAF wastewater treatment. Fenton oxidation was used for the pretreatment of DAF polymerization wastewater, with which the COD removal efficiency exceeded 47.0 % under the optimum conditions of HO 90.0 mM, Fe 20.0 mM, pH value 3.0, and reaction time 120 min. The pretreatment increased the BOD/COD ratio of DAF polymerization wastewater from 0.35 to 0.69 and observably decreased the toxicity (assessed with the Vibrio fisheri bacteria light loss) from 92.0 to 32.0 %. As for the biological treatment, the mixture liquor of Fenton effluent and AN manufacturing wastewater was fed to a bench-scale SBMBR system. Under the designed operation conditions, the average COD, NH-N and TN removal efficiencies reached 82.5, 98.4 and 74.6 %, respectively. The final effluent of SBMBR could steadily meet the National Discharge Standard of China of Grade I (GB8978-1996). The polyvinylidene fluoride flat-plate membranes used in this study showed excellent anti-fouling performance throughout the operation period. [ABSTRACT FROM AUTHOR]

Microbial communities play a key role in wetland water purification and nitrogen cycling. The spatial distribution and diversity of total bacteria in large-scale constructed wetland were investigated by polymerase chain reaction-denaturing gradient gel electrophoresis. The abundance of nitrogen related functional bacteria were measured by real-time PCR using specific primers. The results showed that the diversity of total bacterial community decreased from the inlet zone (Shannon-Wiener index, H′ = 3.471) to the outlet zone ( H′ = 2.566), so did the species richness and evenness. The dominant bacteria of the wetland were Proteobacteria, Acidobacteria and Bacilli. The abundance of amoA gene was higher than those of another two functional genes. There was significant correlation between the abundance of amoA gene and pH ( r = 0.852), DO ( r = −0.595), NH ( r = 0.595) and NO ( r = 0.726) concentrations. The abundance of nosZ gene correlated with the DOC concentration ( r = −0.614). The ratio of amoA/ Nitrospira showed significant correlation with NH concentration ( r = 0.641), while the ratios of amoA/ nosZ ( r = −0.801) and Nitrospia/nosZ ( r = −0.610) could reflect the NO concentrations. Therefore, the three ratios of nitrogen related functional genes may serve as new biological indicators for wetland condition assessment. [ABSTRACT FROM AUTHOR]

A novel system integrating Johannesburg (JHB) and sulfur autotrophic denitrification (SAD) process was proposed to enhance nitrogen removal in treating low COD/TN ratio (COD 129 mg/L, TN 29 mg/L on average) municipal wastewater at low temperature (12.2 ± 0.5 °C). The results showed that under an HRT of 11.3 h, the JHB process effluent COD, TN, and NH $$ _{4}^{ + } $$ -N were 32, 13.8, and 1.6 mg/L on average, respectively. Since NO $$ _{3}^{ - } $$ -N was the prominent compound of TN (average 80.6 %) and COD was low in JHB effluent, the SAD process utilized sulfur granule as electron donor for autotrophic denitrification was employed to remove the rest NO $$ _{3}^{ - } $$ -N of the JHB process. In JHB-SAD system, heterotrophic denitrification cooperated with autotrophic denitrification to enhance nitrogen removal. It was found that 87.0 % JHB effluent nitrogen was removed by SAD process under the most efficient nominal hydraulic retention time (HRT) of 0.32 h. The SAD process effluent of COD, TN, and NH $$ _{4}^{ + } $$ -N were 21, 1.8, and 1.0 mg/L, respectively. Most importantly, the JHB-SAD system could achieve complete nitrogen removal theoretically as long as the NH $$ _{4}^{ + } $$ -N was sufficiently oxidized. The nitrogen removal performance of JHB-SAD system is attractive in treating low COD/TN ratio municipal wastewater at low temperature. Moreover, SAD process was well adapted for limited space because of the efficient NO $$ _{3}^{ - } $$ -N removal, which was propitious to upgrade wastewater treatment plant. [ABSTRACT FROM AUTHOR]

To improve the efficiency of the existing plant for refractory petrochemical dry-spun acrylic fiber (DAF) wastewater treatment, a pilot-scale hybrid anoxic/oxic-membrane bioreactor (A/O-MBR) system with multi-cell section was designed and tested. The operation parameters, alkalinity and carbon source demands in nitrification/denitrification and removal performance of typical pollutants were investigated, and the results were compared with those from the existing wastewater treatment plant (WWTP) of DAF factory. It showed that at hydraulic retention time >32 h, recycle ratio of 80 % and pH 7.2-7.8 in nitrification stage, the average removal efficiency of COD, NH-N and TN in the hybrid A/O-MBR could reach 56.5, 86.6 and 45.9 %, respectively, which had been significantly higher than those of the existing WWTP. The deficiency of alkalinities and carbon sources hindered further nitrogen removal; therefore, NaCO and NaAc were supplemented to improve the performance of nitrification and denitrification, and the recycle ratio was optimized from 80 to 200 %. Then, under the conditions of 200 % recycle ratio, 97.8-148.5 mg/L of alkalinity addition to oxic tank and 107.4-149.6 mg/L of carbon source addition to anoxic tank, the nitrification and denitrification performance in the hybrid A/O-MBR was clearly enhanced, and the NH-N and TN removal efficiency could be improved from 64.3 and 45.9 to 86.9 and 60.5 %, respectively. Meanwhile, the removal efficiency of typical pollutants SO, CN, AN, DMF, BOD and TOC reached 99.3, 91.3, 100, 100, 92.5 and 53.5 %, respectively. Compared with the existing WWPT, the tested hybrid A/O-MBR process had a better treatment performance for nitrification and denitrification, and the effluent could meet the Grade I requirements of the National Discharge Standard of Acrylic Fiber Industry. [ABSTRACT FROM AUTHOR]

Anaerobic ammonium oxidation (Anammox) was a recent discovery of new energy-efficient, microbiologically mediated nitrogen removal process, which was mainly used for the treatment of rich ammonium wastewater of low C/N ratio in a high operating temperature of 35-40 °C. But the growth rate of anammox bacteria was extremely low and it was easily inhibited by many factors, which becomes a bottleneck problem in the application of this efficient nitrogen removal process in the actual wastewater treatment at ambient temperature. So, influence of several key factors (i.e., COD, methanol, hydrazine, hydroxylamine, pH, nitrate, and phosphate) on the nitrogen removal performance of the anammox process was researched to optimize the operation of the anammox process in a bio-filter, and the total nitrogen removal rate ( R) and the linear correlation coefficient between the total nitrogen removal rate ( R) and influent total nitrogen load ( L) of it were assessed with the real municipal wastewater at ambient temperature. The results demonstrated that (1) the influent of COD <100 mg/L had no visible inhibition on the anammox process in the bio-filter, and the recommendation of COD <80 mg/L was suitable for the operation; (2) short-term shock load of methanol would give significant inhibition on the anammox bacteria, which could be restored by adding a small amount of hydrazine and hydroxylamine, but the recovery process was extremely slow; (3) when the influent total nitrogen load increased suddenly, and the removal capacity of the bio-filter was not enough, the temporary mixed dosing of hydroxylamine and hydrazine could enhance the nitrogen removal performance; (4) the anammox activity was very sensitive to the influent pH, and the best range of pH values was 7.3-7.6; (5) the nitrate of 23.56-463.14 mg N/L had no obvious effect on the nitrogen removal performance; and (6) the phosphate itself had no significant inhibition on the anammox bacteria physiologically and ecologically, but it could form a great deal of deposits, which would lead to the bio-filter plugging. [ABSTRACT FROM AUTHOR]

Abstract: Denitrification is an important pathway of removal depending on wetland soil characteristics. Most studies on denitrification have been conducted in the freshwater wetlands and coastal marshes, but little information is available on how soil and environmental factors affect denitrification of saline wetlands in semi-arid regions. We conducted a correlative study on denitrification potential in relation to the physico-chemical and biological characteristics. Composite soil samples of different depths were collected from different halophyte communities along a saline-impact gradient around Wuliangsuhai Lake, i.e. Comm. Salicornia europaea (CSE), Comm. Suaeda glauca (CSG), Comm. Kalidium foliatum (CKF) and Comm. Sophora alopecuroides (CSA). The CSA soil profile showed the fastest denitrification kinetics and tended to yield the largest amount of N2O, followed by the CKF, CSG and CSE. The mean of potential denitrification rates was the highest across all depths of the CSA soil profile, followed by the CKF, CSG, and CSE. Principal component analysis indicated that exchangeable sodium percentage was a key factor to denitrification potential, apart from organic carbon, nitrate and denitrifying bacteria. The results could have significant implication in integrated assessment and management of salined wetlands for treating nutrient-rich return water from farmland, industrial wastewater and domestic sewage in the diverted trunk drain used for the lakeshore restoration. [Copyright &y& Elsevier]

Dibutyl phthalate (DBP) is a typical contaminant in pharmaceutical wastewater with strong bio-depressive properties which potentially affects the operation of municipal wastewater treatment systems. Based on a year-round monitoring of the quality of influent and effluent of a full-scale pharmaceutical wastewater treatment plant in Northeast China, the DBP was found to be the representative pollutant and its concentration in the effluent ranged 4.28 ± 0.93 mg/L. In this study, the negative effects of DBP on a pilot-scale A2/O-MBR system was investigated. When the influent DBP concentration reached 8.0 mg/L, the removals of chemical oxygen demand (COD) and total nitrogen (TN) were significantly inhabited (P < 0.01), with the effluent concentration of 54.7 ± 2.6 mg/L and 22.8 ± 3.7 mg/L, respectively. The analysis of pollutant removal characteristics of each process unit showed that DBP had the most significant effects on the removals of COD and TN in the anoxic tank. The α- and β-diversity in the system decreased significantly when the influent DBP concentration reached 8.0 mg/L. The impacts of DBP on known nitrifying bacteria, such as Nitrospira , and phosphorus accumulating organisms (PAOs), such as Cadidatus Accumulibacter, were not remarkable. Whereas, DBP negatively affected the proliferation of key denitrifying bacteria, represented by Simplicispira , Dechloromonas and Acinetobacter. This study systematically revealed the impacts of DBP on the pollutants removal performance and the bacterial community structure of the biological municipal wastewater treatment process, which would provide insights for understanding the potential impacts of residues in treated pharmaceutical wastewater on biological municipal wastewater treatment. [Display omitted] • Effects of DBP was investigated in pilot-scale with real wastewater. • High influent DBP (6–8 mg/L) significantly affected the removal of TN and COD. • DBP showed the greatest impact on the anoxic stage. • DBP significantly inhibited the activity of denitrifying bacteria and GAOs. [ABSTRACT FROM AUTHOR]