Nitrogen-rich Saline Wastewater Research Articles

Effects of salinity on the simultaneous anammox and denitrification process: performance, sludge morphology and shifts in microbial communities.

In this study, the long-term effects of different salinities on the performance, sludge morphology and shifts in microbial communities were studied in a simultaneous anammox and denitrification (SAD) process at a C/N ratio of 0.5. Stable nitrogen removal efficiencies of 86.96 and 84.58% and nitrogen removal rates of 0.95 and 0.93 kg (m3 d)−1 could be achieved under low (25 mmol l−1) and moderate (50 mmol l−1) salinity, respectively. However, the performance collapsed when the system was exposed to high salinity (100 mmol l−1). The content of extracellular polymeric substances increased as salinity increased, which resulted in larger sizes of granular sludge under low and moderate salinities. Nevertheless, high salinity shock disintegrated granular sludge, thereby decreasing the average granule size. The Illumina-Miseq sequencing results revealed that Candidatus Jettenia was the sole salinity-tolerant AnAOB genus during the entire operation, whereas the main denitrification bacterial genera shifted from Denitrisoma under low salinity to Denitrisoma, Thauera and Ignavibacterium under high salinity. The results of this study provide a comprehensive and practical evaluation of the SAD process for organic nitrogen-rich saline wastewater treatment.

Marine anammox bacteria-driven nitrogen removal from saline wastewater under different vanadium (v) doses: Evaluation on performance and kinetics

This study used a sequencing batch reactor to investigate the nitrogen removal performance of marine anammox bacteria (MAB) from nitrogen-rich saline wastewater with addition of a transition element, vanadium (V(V)). The findings showed that the performance of nitrogen removal by MAB was enhanced by dosing proper amount of V (V) (i.e. 0.25–20 mg/L), but the effectiveness deteriorated at higher doses (>20 mg/L). Vanadium (V) level at 1 mg/L was found to be an optimal dose for complete removal of ammonia (NH4+-N) within only 160 min. Substrate conversion rates were improved and stayed at high for longer periods with lower vanadium doses (0.25–10 mg/L), which indicates that the MAB-mediated anammox reaction rate was accelerated by adding V(V). Moreover, V(V) was more preferential than partial nitrite (NO2−) to be used as the electron acceptor by MAB, thus the new marine anammox process is termed as Vammox. Kinetic analysis using remodified Logistic model, modified Boltzman and Gompertz models on the nitrogen removal processes in typical operational conditions with V(V) addition revealed that none of the three models was appropriate at higher V(V) doses (>20 mg/L). Nevertheless, the remodified Logistic model was most suitable at lower V(V) doses (≤20 mg/L).

Insights into microbial community variability and functional genes of various Candidatus Scalindua-based anammox processes treating nitrogen-rich saline wastewater

Marine anammox bacteria (MAB) has been enriched in four sequencing batch reactors to treat nitrogen-rich saline wastewater. The community variability and cell activity of MAB were studied under different operating conditions. Besides, a novel hydrazine oxidoreductase (Hzo) primer set was designed and used for fast detection of MAB. The results indicated that, independent of operating conditions, Candidatus Scalindua wagneri was the dominant species in nitrogen-rich saline wastewater treatment. Low inoculation pretreatment temperature was a useful operational method to enhance the MAB abundance. Both the enzyme synthesis and cell penetrativity were promoted by Fe(III) addition, which benefited to improve the nitrogen removal performance. High influent NH4+-N and NO2−-N could decrease the synthesis of enzyme and protein which related with nitrogen removal from saline wastewater through MAB. The Hzo gene was an effective functional gene for specific and fast detection of MAB in engineered systems.

Build the expressway for the salt-tolerant anammox process: Acclimation strategy tells the story

The wide existence of saline wastewater has attracted public attention due to its environmental destructiveness. The potential of anammox to treat saline wastewater was systematically evaluated in this study. Three bioreactors with different salinity increasing strategies (R1: inhibition kinetic; R2: gradient increasing; R3: pulsed increasing) were operated to identify the optimal acclimation mode. The results showed that the inhibition of anammox activity by salinity was mainly caused by the loss of enzyme activity. Under the condition of 25.0 g NaCl L−1, the highest nitrogen removal rate of R3 (2.36 ± 0.14 kg N m−3 d−1) indicated that the pulsed strategy might be optimal. Changes in microbial community might be the primary reason lead to different acclimatization results. The relative abundance of anammox bacteria increased by 37.19% in R1 and by 46.81% in R3, but remained stable in R2 with increasing salinity. Dynamic varations in bacterial interactions, proteins, and functional genes revealed the potential resistance mechanisms of bacteria to salinity. The present work provides a novel approach and guidance for the treatment of nitrogen-rich saline wastewater by the anammox process.

Biostimulation of a marine anammox bacteria-dominated bioprocess by Co(II) to treat nitrogen-rich, saline wastewater

The biostimulation of a marine anammox bacteria (MAB)-dominated bioprocess with Co(II) was studied in a sequencing batch reactor (SBR) treating nitrogen-rich saline wastewater at 15 °C. The low Co(II) load of 0.0015 kgCo2+added/(m3.d) had little effect on the removal of nitrogen. The nitrite removal rate (NRR), ammonia removal rate (ARR), and specific anammox activity (SAA) reached 0.73 kg/(m3·d), 0.59 kg/(m3·d), and 0.23 kg/(kg·d), respectively, under the Co(II) load of 0.009 kgCo2+added/(m3.d). However, the loadings of Co(II) at 0.024–0.03 kgCo2+added/(m3.d) negatively affected the activity of MAB. Besides, the values of ΔNO2−-N/ΔNH4+-N (1.15–1.29) were lower than the theoretical ratio values (around 1.32) likely because of the marine commamox process. The removal of nitrogen from nitrogen-rich saline wastewater was achieved by the synergy between Candidatus Scalindua (27.11%) and Candidatus Kuenenia (9.55%). The nitrogen removal with Co(II) addition could be well described by a modified Logistic model.

Long-term nitrogen removal performance and kinetics of anaerobic ammonia oxidation bacteria treating nitrogen-rich saline wastewater with trehalose addition.

A sequencing batch reactor was used to study long-term nitrogen removal performance of anaerobic ammonia oxidation bacteria (AnAOB) with trehalose addition treating nitrogen-rich saline wastewater. The operating temperature was controlled at 35±0.5°C with influent pH of 7.5±0.1. Trehalose played a significant role in enhancing long-term nitrogen removal performance. When trehalose was 0.1, 0.2, and 0.3mM, ammonia removal efficiency (ARE) increased by 4.9%, 16.2%, and 32.4%, and nitrite removal efficiency (NRE) improved by 7.5%, 27.9%, and 42.2%, respectively. Optimal ARE and NRE were 92.4% and 97.4% achieved at 0.35mM trehalose. Moreover, was removed completely within 2hr at high trehalose content due to the synergistic effect resulting from AnAOB and heterotrophic denitrifying bacteria. increased with trehalose addition, while decreased. Compared to , fluctuated greatly. The remodified Logistic model and modified Gompertz model were suitable for describing nitrogen removal in an operating cycle with trehalose addition. Fitted AREmax values were consistent with experimental values. Appropriate trehalose addition could shorten the response time of AnAOB coping with hazardous environment stress. Lag time was within 1hr and the minimal fitted λ value got close to 0 achieved at 0.15mM trehalose. PRACTITIONER POINTS: Trehalose enhanced nitrogen removal of AnAOB in saline wastewater treatment. Optimal ARE and NRE were 92.4% and 97.4% achieved at 0.35mM trehalose. Remodified Logistic and Gompertz models can analyze nitrogen removal with trehalose. Appropriate trehalose can shorten response time of AnAOB coping with salt stress.

Nitrogen removal performance of marine anammox bacteria treating nitrogen-rich saline wastewater under different inorganic carbon doses: High inorganic carbon tolerance and carbonate crystal formation

With different inorganic carbon (IC) doses, nitrogen removal performance of marine anammox bacteria (MAB) treating nitrogen-rich saline wastewater was investigated in a sequencing batch reactor. Ammonium removal efficiency (ARE) was above 99% at 108–3600 mg/L IC, which indicated MAB had a good tolerance to high IC dose. When IC was 108–1200 mg/L, ARE reached 90% within 2.5 h. MAB activity was greatly promoted by providing adequate IC. Besides, the maximal substrate conversion rate (3.4 kg/(m3 d)) was achieved at 180 mg/L IC. Both the modified Logistic and Boltzmann models were appropriate to describe nitrogen removal at low IC doses, while the modified Gompertz model was more accurate at high IC doses. Calcium carbonate crystal was formed on the surface of MAB granule at high IC doses, which resulted in a significant deterioration of nitrogen removal performance.

Enhanced nitrogen removal through marine anammox bacteria (MAB) treating nitrogen-rich saline wastewater with Fe(III) addition: Nitrogen shock loading and community structure

Marine anammox bacteria (MAB) were used to treat nitrogen-rich saline wastewater with Fe(III) addition under nitrogen shock loading. Ammonia loading rate (ALR) and nitrite loading rate (NLR) gradually increased from 0.033 and 0.039 to 0.68 and 0.89 kg/(m3·d), respectively. With 5 mg/L Fe(III) addition, ammonia removal rate (ARR) and nitrite removal rate (NRR) reached maximal values of 0.56 and 0.60 kg/(m3·d), respectively. The value of ΔNO2−-N/ΔNH4+-N was lower than theoretical ratio due to existing marine Feammox process. The growth rate of MAB was accelerated by Fe(III) and it dominated the reactor (27.70%). Besides, MAB were synergized with Marinicella and Caldithrix to achieve higher total nitrogen removal. Haldane model was proper to analyze and predict the effect resulting from nitrite on the activity of MAB under nitrogen shock loading. Overall, this study provides novel insights into the effect of Fe(III) on MAB treating nitrogen-rich wastewater.

Underlying mechanisms of ANAMMOX bacteria adaptation to salinity stress.

Dealing with nitrogen-rich saline wastewater produced by industries remains challenging because of the inhibition of functional microorganisms by high salinity. The underlying mechanisms of anaerobic ammonium-oxidizing bacteria (AnAOB) exposed to salinity stress should be studied to investigate the potential of anaerobic ammonium oxidation (ANAMMOX) for applications in such wastewater. In this study, the total DNA from granular sludge was extracted from an expanded granular sludge bed(EGSB) reactor operated at 0, 15 and 30g/L salinity and subjected to high-throughput sequencing. The nitrogen removal performance in the reactor could be maintained from 86.2 to 88.0% at less than 30g/L salinity level. The microbial diversity in the reactor under saline conditions was lower than that under the salt-free condition. Three genera of AnAOB were detected in the reactor, and Candidatus Kuenenia was the most abundant. The predictive functional profiling based on the Clusters of Orthologous Groups of proteins (COGs)database showed that the inhibition of AnAOB under saline conditions was mainly characterised by the weakening of energy metabolism and intracellular repair. AnAOB might adapt to salinity stress by increasing their rigidity and intracellular osmotic pressure. The predictive functional profiling based on the Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway database revealed that the inhibition of AnAOB was mainly manifested by the weakening of intracellular carbohydrate and lipid metabolism, the blockage of intracellular energy supply and the reduction of membrane transport capacity. AnAOB might adapt to salinity stress by strengthening wall/membrane synthesis, essential cofactors (porphyrins) and energy productivity, enhancing intracellular material transformation and gene repair and changing its structure and group behaviour. The stability of the nitrogen removal performance could be maintained via the adaptation of AnAOB to salinity and their increased abundance.

Carbon and nitrogen removal through “Candidatus Brocadia sinica”-dominated simultaneous anammox and denitrification (SAD) process treating saline wastewater

“Candidatus Brocadia sinica”-dominated simultaneous anammox and denitrification (SAD) process was used to treat nitrogen-rich saline wastewater. The reactor was operated at 30 ± 0.5 °C with influent pH of 7.5 ± 0.1. ‘Ca. B. sinica’ could adapt to high saline surroundings after 42 cycles’ operation. With 100% seawater, nitrogen removal rate and organic removal rate were 0.71 kg/(m3·d) and 0.27 kg/(m3·d), respectively. Both were closed to those without seawater. Independent of salinity, percentage of nitrogen removal by anammox was higher than that by denitrification during the whole treatment period. ‘Ca. B. sinica’ had good tolerance to salinity. However, maximum removal rate of NH4+-N declined with growing salinity. Modified Boltzmann model was proper to analyze the effect resulting from salinity on the maximum removal rate of NH4+-N. Granular sludge characterized by anammox granule embedded in denitrifying granule might play an important role in salt tolerance of anammox bacteria.

Performance of anammox process treating nitrogen-rich saline wastewater: Kinetics and nitrite inhibition

A sequencing batch reactor (SBR) was operated more than 200 d to treat nitrogen-rich saline wastewater by anammox process. The temperature was controlled at 35 ± 0.5 °C and the mixed liquor suspended solids (MLSS) was around 4000 mg TSS/L. Anammox reactor could gradually acclimate to 100% seawater. However, the long-term effects of 50% seawater not only affected nitrogen removal performance, resulting in a decrease of nitrogen removal rate (NRR) to 0.114 kg N/(m3·d), but also weakened sludge settling ability. The effect resulting from 50% seawater was reversible and the NRR gradually increased to 0.419 kg N/(m3·d) by adding sponge carriers. Analysis of variance (ANOVA) test shown that △NO3−-N/△NH4+-N ratio was significantly different (p < 0.05) under different seawater content. After inhibition resulting from 100% seawater, the response process of anammox could be divided into three periods. At 100% seawater, nitrogen removal performance of anammox reactor was affected when influent nitrite was higher than 150 mg N/L (NO2−-Ninf/NH4+-Ninf = 1.37 ± 0.02). Luong model was suitable to analyze inhibitory effect resulting from nitrite under saline surroundings.

Enhanced performance and kinetics of marine anammox bacteria (MAB) treating nitrogen-rich saline wastewater with Mn(II) and Ni(II) addition

A sequencing batch reactor (SBR) was used to study nitrogen removal performance of marine anammox bacteria (MAB) with Mn(II) and Ni(II) addition. The reactor was operated at 25 ± 0.5 °C with influent pH of 7.5 ± 0.1. Optimal ammonium removal efficiencies (AREs) were 93.95% and 93.18% with 0.05 mM Mn(II) and 0.025 mM Ni(II), respectively. Both Mn(II) and Ni(II) played key roles in treating nitrogen-rich saline wastewater. However, the effect resulting from Ni(II) was far stronger than Mn(II). With optimal Ni(II) addition (0.025 mM), maximal nitrogen removal rate (NRR) and specific anammox activity (SAA) increased by 14.64% and 57.88%, respectively. Modified Boltzmann model was appropriate to describe nitrogen removal at low Mn(II) and Ni(II) concentrations while remodified Logistic model could be used at high Mn(II) and Ni(II) concentrations. Mn(II) and Ni(II) dosage should be controlled within 0.075 mM to achieve good nitrogen removal in nitrogen-rich saline wastewater treatment.