Advancing anaerobic digestion with MnO2-modified biochar: Insights into performance and mechanisms.

The use of bio-based composites to enhance the methane production in anaerobic digestion has attracted considerable attention. Nevertheless, the study of electron transfer mechanisms and the applications of biochar/MnO2 (MBC) in complex systems remains largely unexplored. Biochar composited with MnO2 at 10:1 mass ratio (MBC10) increased the content of volatile fatty acids by 9.09 % during acidogenic phase. During the methanogenic experiments using acetate, cumulative methane production (CMP) rose by 5.83 %, and in the methanogenic experiments using food waste, CMP increased by 24.32 %. Microbial community analysis indicated an enrichment of Syntrophomonas, Bacilli, and Methanosaetaceae in the MBC10 group. This enrichment occurred mainly due to the redox capability of MnO2 enhancing MBC capacitance, thereby facilitating microbial electron transfer processes. Additionally, under 2 g/L ammonia nitrogen concentration and 30 g/L organic load, the CMP of MBC10 increased by 12.74 % and 9.44 %, respectively, compared to the BC600 group. This study illuminates MBC's electron transfer mechanisms and applications, facilitating its wider practical adoption and fostering future innovations.

Rapid-response nanofiber films against ammonia based on black wolfberry anthocyanins, polyvinyl alcohol and sodium alginate for intelligent packaging.

To develop novel intelligent indicator films, the mixture of anthocyanin (BWA), polyvinyl alcohol (PVA) and sodium alginate (SA) were spun into PVA/SA/BWA nanofiber films with BWA concentration of 0 %, 5 %, 10 %, and 15 % (based on PVA and SA) via electrospinning technology. The results showed that the BWA was sensitive to pH and was controlled release from films. With increasing BWA concentration, the fiber diameter, tensile strength, and elongation at break gradually decreased, while water contact angle, thickness, moisture content, and antioxidant properties gradually increased. The electrospinning films exhibited high sensitivity to ammonia with rapid color changes in 1 s and excellent color reversibility and color stability within 21 d. The application for shrimp packaging showed that the colorimetric response of the films was closely related to the changes in pH, total volatile basic nitrogen (TVB-N), and total viable count (TVC) of shrimp. This suggests that the prepared films are promising in application for intelligent packaging.

Comparison of moving bed biofilm reactor and bio-contact oxidation reactor start-up with heterotrophic nitrification-aerobic denitrification bacteria and activated sludge inoculation under high ammonia nitrogen conditions.

To overcome poor ammonia tolerance and removal performance of bio-contact oxidation (BCO) reactor inoculated with activated sludge for high-ammonia nitrogen (NH4+-N) chemical wastewater treatment, this study compared inoculating heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria in moving bed biofilm reactor (MBBR) with activated sludge inoculation in BCO reactor under simulated high NH4+-N conditions. Results revealed that MBBR achieved faster biofilm formation (20 days vs. 100 days for BCO) with notable advantages: 27.6 % higher total nitrogen (TN) and 29.9 % higher NH4+-N removal efficiency than BCO. Microbial analysis indicated optimal enrichment of the key nitrogen removal (NR) bacterium Alcaligenes, leading to increased expression of NR enzymes hydroxylamine reductase, ensuring the superior NR efficiency of the MBBR. Additionally, functional enzymes and genes analysis speculated that the NR pathway in MBBR was: NH4+-N â†’ NH2OH â†’ NO3--N â†’ NO2--N â†’ NO â†’ N2O â†’ N2. This research offers a practical and theoretical foundation for extending HN-AD bacteria-inoculated MBBR processes.

Decoding the Role of Extracellular Polymeric Substances in Enhancing Nitrogen Removal from High-Ammonia and Low-C/N Wastewater in a Sequencing Batch Packed-Bed Biofilm Reactor.

Although the role of extracellular polymeric substances (EPSs) as a viscous high-molecular polymer in biological wastewater treatment has been recognized, in-depth knowledge of how EPSs affect nitrogen removal remains limited in biofilm-based reactors. Herein, we explored EPS characteristics associated with nitrogen removal from high-ammonia (NH4+-N: 300 mg/L) and low carbon-to-nitrogen ratio (C/N: 2-3) wastewater in a sequencing batch packed-bed biofilm reactor (SBPBBR) under four different operating scenarios for a total of 112 cycles. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier-transform infrared (FTIR) analysis revealed that the distinct physicochemical properties, interface microstructure, and chemical composition of the bio-carrier were conducive to biofilm formation and microbial immobilization and enrichment. Under the optimal conditions (C/N: 3, dissolved oxygen: 1.3 mg/L, and cycle time: 12 h), 88.9% ammonia removal efficiency (ARE) and 81.9% nitrogen removal efficiency (NRE) could be achieved in the SBPBBR. Based on visual and SEM observations of the bio-carriers, biofilm development, biomass concentration, and microbial morphology were closely linked with nitrogen removal performance. Moreover, FTIR and three-dimensional excitation-emission matrix (3D-EEM) spectroscopy demonstrated that tightly bound EPSs (TB-EPSs) play a more important role in maintaining the stability of the biofilm. Significant shifts in the number, intensity, and position of fluorescence peaks of EPSs determined different nitrogen removal. More importantly, the high presence of tryptophan proteins and humic acids might promote advanced nitrogen removal. These findings uncover intrinsic correlations between EPSs and nitrogen removal for better controlling and optimizing biofilm reactors.

The Aggregation and Dissolution of Citrate-Coated AgNPs in High Ammonia Nitrogen Wastewater and Sludge from UASB-Anammox Reactor.

Silver nanoparticles (AgNPs) are released into the sewage pipes and ultimately wastewater treatment plants during manufacturing, use, and end-life disposal. AgNPs in wastewater treatment plants aggregate or dissolve, and may affect the microbial community and subsequent pollutant removal efficiency. This study aims to quantitatively investigate the fate of AgNPs in synthetic high ammonia nitrogen wastewater (SW) and sludge from an up-flow anaerobic sludge blanket (UASB) anammox reactor using a nanoparticle tracking analysis (NTA), dynamic light scattering (DLS), transmission electron microscope (TEM), and atomic absorption spectroscopy (AAS). Results showed that 18.1 mM NH4+, 2.11 mM Mg2+ in SW caused less negative zeta potential (ζ-potential, -18.4 vs. -37.4 mV), aggregation (388.8 vs. 21.5 nm), and settlement (80%) of citrate-coated AgNPs (cit-AgNPs) in 220 min. The presence of 18.5 mM Cl- in SW formed AgCl2-, AgCl(aq) and eventually promoted the dissolution (9.3%) of cit-AgNPs. Further exposure of SW-diluted AgNPs to sludge (42 mg L-1 humic acid) and induced a more negative ζ-potential (-22.2 vs. -18.4 mV) and smaller aggregates (313.4 vs. 388.8 nm) due to the steric and hindrance effect. The promoted Ag dissolution (34.4% vs. 9.3%) was also observed after the addition of sludge and the possible reason may be the production of Ag(NH3)2+ by the coexistence of HA from sludge and NH4+ from SW. These findings on the fate of AgNPs can be used to explain why AgNPs had limited effects on the sludge-retained bacteria which are responsible for the anammox process.

Effect of high ammonia on granular stability and phosphorus recovery of algal-bacterial granules in treatment of synthetic biogas slurry.

The aim of the study was to investigate the application of algal-bacterial granules in treatment of high ammonia wastewater. Two identical cylindrical reactors, i.e., Rc and Rs was used to develop granular sludge system with synthetic biogas slurry. Rs was run under an artificial solar lamp controlled at 12 h power on and 12 h power off (∼10,000 lux); Rc was operated as control (no light). Results showed that algal-bacterial granules (ABGS) developed in Rs exhibited better structural stability in the face of high ammonia influent. Compared with aerobic granules (AGS), ABGS possessed high proteins (PN) content (145.3 mg/g-VSS) in extracellular polymeric substances (EPS) and better O2 mass transfer inner granules. Higher phosphorus (P) removal capacity was obtained in Rs even under 400 mg/L NH3-N which resulted in higher P content in ABGS biomass (56.4 mg/g-TSS). Bioavailable P in ABGS was 44 mg P/g-SS on day 160, approximately 1.53-times higher than that in AGS.

Nitrogen removal and mechanism of an extremely high-ammonia tolerant heterotrophic nitrification-aerobic denitrification bacterium Alcaligenes faecalis TF-1.

A novel heterotrophic nitrifying bacterium with high salt and high ammonia nitrogen tolerance, Alcaligenes faecalis TF-1, was isolated from the leachate of a landfill. The verification of nitrogen removal efficiency of different nitrogen sources and PCR amplification electrophoresis results showed that the HN-AD pathway of the strain TF-1 was NH4+ â†’ NH2OH â†’ NO â†’ N2O â†’ N2. The results of parameter optimization showed that the optimal nitrogen removal conditions were as follows: sodium citrate as carbon source, C/N = 16, pH = 7, and NH4+-N loading of 808.21 mg/L. The strain TF-1 could remove about 94.60% of ammonia nitrogen (1963.94 mg/L). The salinity tolerance range of the strain TF-1 was 0-70 g/L, and the removal efficiency was 52.87% at salinity 70 g/L and NH4+-N concentration 919.20 mg/L and 55.67% at pH = 10 and NH4+-N concentration 994.82 mg/L. The extreme environmental adaptability and remarkable nitrogen removal performance make this strain a promising candidate in leachate treatment.

Effects of ammonia on electrochemical active biofilm in microbial electrolysis cells for synthetic swine wastewater treatment.

When facing wastewater with high organic and ammonia, e. g. swine wastewater, microbial electrolysis cell (MEC) is emerging for energy extraction as hydrogen and methane. However, the effects of highly concentrated ammonia on MEC haven't been fully evaluated. In this study, single-chamber MECs were operated with acetate and sucrose as substrates under various ammonia concentrations. The current generally increased with ammonia loading from 80 to 3000 mg L-1. Yet, the substrate consumption in MECs was inhibited with ammonia concentrations above 1000 mg L-1. As a combined result, the energy recovery efficiency of MECs was stable. The electrochemical activity of anode biofilm reached the peak under 1000 mg L-1 ammonia and was restricted under higher ammonia loadings. Under neutral pH, the NH4+ increases the cell membrane permeability, which benefited the electrochemical activity of exoelectrogens to a proper extent. Nevertheless, the toxic ammonia also accelerated the anode biomass loss and stimulated the extracellular polymeric substance (EPS) secretion. Due to the current increase, the abundance of exoelectrogens generally raised with ammonia loading from 80 to 3000 mg L-1. However, except for anode biomass loss, the carbon and methane metabolism pathways were inhibited in acetate-fed MEC, while the glycolysis acted as the rate-limiting step for substrate degradation in sucrose-fed conditions. This study systematically examined the influences of high ammonia loading on MEC performances, bio-community and anode electrochemical activities, and evaluated practical feasibility and application inch of MECs for the energy recovery and pollutant removal of high concentration organic and ammonia wastewater.

Characterization of Alcaligenes aquatilis as a novel member of heterotrophic nitrifier-aerobic denitrifier and its performance in treating piggery wastewater.

A novel strain AS1 with heterotrophic nitrifying-aerobic denitrifying capacity in the species of Alcaligenes aquatilis was isolated from the aerobic activated sludge. It showed a great capability of ammonia removal, and the aerobic metabolic pathways to yield gaseous-nitrogen by hydroxylamine oxidation and nitrite denitrification were proposed. AS1 could efficiently remove ammonia under a wide range of environmental conditions, including the ratio of chemical oxygen demand to total nitrogen: 15-30, pH: 6-10, NaCl: 0-60 g/L, shaking speed of 0-180 rpm, and succinate, acetate, or citrate as carbon source. In the treatment of actual piggery wastewater, 95.3%, 95.1% and 84.9% of NH4+-N was removed by AS1 when the initial ammonia concentration was 500, 1300, and 2000 mg/L, respectively, with the maximum NH4+-N removal rate of 30.5 mg/L/h and 569.7 mg/L/d. Furthermore, plate colony-counting showed that AS1 achieved an efficient proliferation. These results imply the application potential of AS1 in treating high-ammonia wastewater.

Nitrification performance evaluation of activated sludge under high potassium ion stress during high-ammonia nitrogen organic wastewater treatment.

The recycling reverse osmosis (RO) membrane concentrate of some high-ammonia nitrogen (NH4+-N) organic wastewater to the biological unit could cause potassium ion (K+) accumulation, thereby affecting the removal of NH4+-N by activated sludge. Thus, the effects of high K+ stress on activated sludge nitrification performance was studied. The results showed that the high K+ stress promoted the floc sludge to produce more extracellular polymers (EPS), which accelerated the sludge sedimentation and enriched the biomass in sequential batch reactors (SBRs). The ammonia oxidation process and nitrite (NO2--N) oxidation process were further analyzed in the nitrification process. High K+ stress enriched ammonia oxidizing bacteria (AOB), which ensured the efficient ammonia oxidation process in SBRs, and ensured the removal rate of NH4+-N was maintained above 93%. However, high K+ stress (15g/L KCl) inhibited the activity of NO2--N oxidizing bacteria (NOB) and reduced the abundance of NOB, thus leading to the accumulation of NO2--N, and finally worsened the nitrification performance of activated sludge. In short, the performance of activated sludge will not be inhibited when the K+ in the wastewater does not exceed 5.23 g/L. The results could provide a reference for the optimization of the biological performance in treating high-NH4+-N organic wastewater with activated sludge coupled RO membrane treatment process.

Synergistic denitrification, partial nitrification - Anammox in a novel A2/O2 reactor for efficient nitrogen removal from low C/N wastewater.

A biofilm-based anaerobic-aerobic (A2O2) reactor was constructed to treat manure-free piggery wastewater. The reactor contained four compartments, among which the first two were anaerobic (A phase) and the last two were aerobic (O phase). Throughout around one-year operation, high-level nutrient removal was demonstrated. At an optimal reflux ratio of 100%, the average NH4+-N, TN, and COD removal efficiencies were high as 99.4%, 91.7%, and 79.4%, respectively, with the influent concentration of 220.6, 231.6 and 332 mg/L, respectively. The NH4+-N, TN, and COD concentrations in the final effluent were only 1.4, 18.5 and 65 mg/L, respectively. COD and nitrogen removal were mainly removed in the A phase and O phase, respectively. This result revolutionizes the previous perception that nitrogen is only removed in the A phase of conventional A-O configuration. Achievement of PN/A in the O phase was critical to the efficient nitrogen removal. Heterotrophic denitrification in the anaerobic compartments removed the nitrate produced by anammox, ensuring the high-level nitrogen removal. Anaerobic organic degradation was a major pathway for COD removal, as abundant methanogens detected in the A phase. This study provides a feasible technical scheme for the efficient nutrient removal from ammonium-rich wastewater.

Exposure to High Aerial Ammonia Causes Hindgut Dysbiotic Microbiota and Alterations of Microbiota-Derived Metabolites in Growing Pigs.

Ammonia, an atmospheric pollutant in the air, jeopardizes immune function, and perturbs metabolism, especially lipid metabolism, in human and animals. The roles of intestinal microbiota and its metabolites in maintaining or regulating immune function and metabolism are irreplaceable. Therefore, this study aimed to investigate how aerial ammonia exposure influences hindgut microbiota and its metabolites in a pig model. Twelve growing pigs were treated with or without aerial ammonia (35 mg/m3) for 25 days, and then microbial diversity and microbiota-derived metabolites were measured. The results demonstrated a decreasing trend in leptin (p = 0.0898) and reduced high-density lipoprotein cholesterol (HDL-C, p = 0.0006) in serum after ammonia exposure. Besides, an upward trend in hyocholic acid (HCA), lithocholic acid (LCA), hyodeoxycholic acid (HDCA) (p < 0.1); a downward trend in tauro-deoxycholic acid (TDCA, p < 0.1); and a reduced tauro-HDCA (THDCA, p < 0.05) level were found in the serum bile acid (BA) profiles after ammonia exposure. Ammonia exposure notably raised microbial alpha-diversity with higher Sobs, Shannon, or ACE index in the cecum or colon and the Chao index in the cecum (p < 0.05) and clearly exhibited a distinct microbial cluster in hindgut indicated by principal coordinate analysis (p < 0.01), indicating that ammonia exposure induced alterations of microbial community structure and composition in the hindgut. Further analysis displayed that ammonia exposure increased the number of potentially harmful bacteria, such as Negativibacillus, Alloprevotella, or Lachnospira, and decreased the number of beneficial bacteria, such as Akkermansia or Clostridium_sensu_stricto_1, in the hindgut (FDR < 0.05). Analysis of microbiota-derived metabolites in the hindgut showed that ammonia exposure increased acetate and decreased isobutyrate or isovalerate in the cecum or colon, respectively (p < 0.05). Unlike the alteration of serum BA profiles, cecal BA data showed that high ammonia exposure had a downward trend in cholic acid (CA), HCA, and LCA (p < 0.1); a downward trend in deoxycholic acid (DCA) and HDCA (p < 0.05); and an upward trend in glycol-chenodeoxycholic acid (GCDCA, p < 0.05). Mantel test and correlation analysis revealed associations between microbiota-derived metabolites and ammonia exposure-responsive cecal bacteria. Collectively, the findings illustrated that high ammonia exposure induced the dysbiotic microbiota in the hindgut, thereby affecting the production of microbiota-derived short-chain fatty acids and BAs, which play a pivotal role in the modulation of host systematic metabolism.

Effect of the rapid increase of salinity on anoxic-oxic biofilm reactor for treatment of high-salt and high-ammonia-nitrogen wastewater.

The washing wastewater from the desulfuration and denitration of power plants has high salt (chloride and sulfate) and ammonia-nitrogen concentrations and is difficult to treat using microbiological methods. A novel anoxic/oxic biofilm process was developed to remove ammonia from wastewater. Three rapid strategies (sulfate concentration was increased from 0 to 60 g/L in 6, 13, and 22 days (R1, R2, and R3, respectively)) were applied and produced biofilm with the same nitrification capacity as slow strategies (100-203 days). Excessive organics inhibited the nitrification capacity of the biofilm. R1 excelled at ammonia removal (from 30% to 95%, 70 mg/(L·d), with an effluent ammonia concentration of 4 mg/L) at 60 g/L salinity after the organic load was reduced. The content of extracellular polymeric substances in biofilm depended on its capacity to remove organics. Pseudomonas and Thauera were enriched in the three reactors. Controlling the organic load might prevent the sulfur cycle.

Novel insights into overcoming nitrite oxidation bacteria acclimatization problem in treatment of high-ammonia wastewater through partial nitrification.

A partial nitrification sequencing batch reactor was operated to reveal mechanisms behind nitrite oxidation bacteria (NOB) acclimatization in high-ammonia wastewater treatment. The influent NH4+-N increased stepwise from 499.7 ± 4.2 mg/L to 6994.5 ± 7.5 mg/L with initial free ammonia (FA) concentration rising from 37.9 ± 3.2 mg NH3-N/L to 715.3 ± 47.3 mg NH3-N/L, respectively. NOB acclimatized this FA range with NO3--N production increasing from 29.2 ± 2.6 mg/L to 144.1 ± 31.0 mg/L in a cycle, which was caused by the shift of dominant NOB genus from Nitrospira to Nitrolencea. Nitrosomonas as ammonia oxidation bacteria, could sustain its activity of 62.1 ± 0.1 mg NH4+-N/(gVSS∙L∙h) under the same condition. Hydroxylamine addition could be implemented as an emergency measure to alleviate NOB acclimatization in short-term operation. The findings expanded knowledge about NOB acclimatization types and provided novel insights for addressing this problem in a targeted way.

Nitrification of anaerobic digestate using a consortium of microalgae and nitrifiers in an open photobioreactor with moving bed carriers.

A consortium of microalgae and nitrifiers has attracted attention as an alternative to the expensive traditional nitrification process. A possible obstacle to achieving this is the inhibition of nitrifiers under strong light irradiation. This study evaluated the effect of moving bed carriers on anaerobic digestate nitrification in an open photobioreactor inoculated with microalgae and nitrifiers under an incident light intensity of 1000 µmol photons m-2 s-1. The results showed higher specific nitrification activity in the carrier-added photobioreactor (103.6 mg-N g-TSS day-1) than in one in which no carrier was added (11.7 mg-N g-TSS day-1). The empirical equations for determining the light intensity at different depths in the photobioreactor showed a significant contribution by carriers in attenuating the incident light intensity. This is due to the large light attenuation caused by the carrier (1.09 cm-1). The average light intensity inside of the photobioreactor decreased considerably in the carrier-added photobioreactor (342 µmol photons m-2 s-1), whereas it did not decrease in the one with no added carrier. It was found that specific nitrification activity was significantly negatively affected by average light intensity inside of the reactor, and not by incident light intensity, by combining the results from different studies including ours. This study demonstrated, for the first time, the effectiveness of adding moving bed carriers in photobioreactors to mitigate light inhibition of nitrifiers in a consortium of microalgae and nitrifiers.

[Long-term Stability of Aerobic Granular Sludge Under Low Carbon to Nitrogen Ratio].

Long-term stability is important for the practical application of aerobic granular sludge system under low carbon to nitrogen ratio (C/N). In this study, aerobic granular sludge, seeded in the reactors A and B, were cultivated under low C/N to investigate the properties, performance, and resilience to shock load in the long-term operation. The load of carbon and nitrogen in the feed was increased gradually. The C/N of reactor A was kept at 2, while that of reactor B was kept at 4 initially and then reduced to 2 in the shock load stage. It was discovered that the aerobic granular sludge stored at 4℃ for 30 days was essentially revived after 25 days of cultivation in reactors A and B, with over 90% removal efficiency for COD and ammonia, respectively. In the following stages, the removal efficiencies of COD and ammonia in reactor B were over 90% and complete nitrification was achieved. In contrast, in reactor A, the removal efficiency of COD was only 80% and only partial nitrification was achieved; however, ammonia removal efficiency of 90% was finally achieved. In the shock load stage, the COD removal efficiencies in reactors A and B were still above 80%, but the ammonia removal efficiencies were severely affected. The removal of ammonia was deteriorated in reactor A, while only partial nitrification was achieved in reactor B. During the entire operation, the physical properties of the aerobic granules in reactors A and B were barely affected, with sludge volume index (SVI30) in reactors A and B maintained at 60 mL ·g-1 and 75 mL ·g-1, and mixed liquid suspended solid (MLSS) at 5 g ·L-1and 3.7 g ·L-1, respectively. Microbial analysis showed that the aerobic granular sludge in reactor B has richer and more diverse microbial community than that in reactor A. The abundance of Zoogloea in reactor B, which is simultaneously able to produce polymeric protein and stabilize the structure of the aerobic granules, may be favorable for the high stability of the aerobic granules. These findings suggested that the aerobic granular system under the C/N of 4 had better performance in ammonia removal and higher tolerance to shock load, which guaranteed high stability of the aerobic granular sludge system in long-term operation, as compared to that under the C/N of 2.

Application of encapsulated algae into MBR for high-ammonia nitrogen wastewater treatment and biofouling control.

Low microbial activity and serious membrane biofouling are still critical problems that hinder the extensive application of membrane bioreactor (MBR) for industrial wastewater treatment. To address these bottlenecks, we report a new specialized microorganism encapsulation strategy for constructing a highly efficient MBR system. In our study, the algae-entrapping fiber macrospheres with polymeric coating were first coupled with membrane separation for treating refractory high-ammonia nitrogen wastewater. In comparison with traditional alginate beads, the developed macrocapsule (~0.5 cm) exhibited higher biomass harvesting and lower microbial leakage because of the confined micro-aerobic environment created by dual encapsulation of rigid inorganic macrosphere and porous polymeric layers. Application of algae-encapsulating macrocapsule to MBR presented excellent chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) removal efficiency of 62.23 and 97.38 %, respectively, which were higher than the corresponding values for algae/SA beads and free algae. The biodegradation performance of NH3-N by encapsulated microalgae was similar or superior to that by free cells when the initial content of ammonia nitrogen ranged from 50 to 100 mg/L. The results well demonstrated that the GFS@polymer macrocapsule as a physical barrier reduced the inhibitory effect of higher concentration ammonia nitrogen on the bioactivity of living cells. Importantly, the encapsulated core-shell macrocapsules showed superior anti-biofouling capacity, which had a membrane resistance of 3-5 times lower than that of cell/alginate beads and free cells. This work will open a new avenue to develop a novel encapsulated MBR for various non-degradable wastewater treatments as an energy-saving and sustainable way.

Performance and microbial ecology of a novel moving bed biofilm reactor process inoculated with heterotrophic nitrification-aerobic denitrification bacteria for high ammonia nitrogen wastewater treatment.

To overcome long start-up time, poor ammonia tolerance and removal performance of traditional moving bed biofilm reactor (MBBR) inoculated with activated sludge for high-ammonia wastewater treatment, a novel MBBR based on heterotrophic nitrification-aerobic denitrification (HN-AD) was proposed. Start-up of MBBR was firstly performed via inoculated with HN-AD bacteria. Start-up time was shortened from 39 d to 15 d, NH4+ tolerance was enhanced from 200 mg/L to 1000 mg/L, and TN removal was increased from 30.4% to 80.7%. The carrier types and NH4+ concentration had significant effects on nitrogen removal and microbial ecology. When the NH4+ concentration was increased to 900 mg/L in MBBR using polyvinyl alcohol gel as carrier, the TN removal, the abundance of HN-AD bacteria Acinetobacter, Pseudomonas and Paracoccus, which played a key role in TN removal and ammonia tolerance, and the abundance of genes related to nitrogen removal were much higher than those of MBBR using kaldness.

[Effects of Different Concentrations of Ammonia Nitrogen on the Growth and Enzyme Activity of Four Common Algae Strains].

Treating swine wastewater with a high ammonia nitrogen content with microalgae cultures has proved difficult. In this paper, the strains Chlamydomonas 715, Botryococcus braunii 357, Porphyridium cruentum 806, and Scenedesmus obliquus 417 were tested. Ammonia nitrogen concentrations of 50 mg·L-1, 500 mg·L-1, and 2000 mg·L-1 applied to the media according to the concentrations of biogas slurry. This allowed the effect of different concentrations of ammonia nitrogen on the growth and cell enzyme activity of microalgae to be tested. The results showed that the growth of Chlamydomonas 715 and Scenedesmus obliquus 417 was inhibited at different concentrations of ammonia nitrogen, and the biomass and biomass productivities were lower than for the normal media. However, the biomass and biomass productivity of Porphyridium cruentum 806 in 50 mg·L-1 ammonia nitrogen were 1.78 g·L-1 and 0.16 g·(L·d)-1, respectively, which were higher than the values obtained using KOCK medium. Furthermore, the biomass and biomass productivity of Botryococcus braunii 357 in 500 mg·L-1 ammonia nitrogen were 1.95 g·L-1 and 0.18 g·(L·d)-1, respectively, which were higher than the values obtained using BG11 medium. The SOD, POD, and CAT of all algae species showed a decreasing tendency in response to an increase in the concentration of ammonia nitrogen, as did MDA. These results provide a theoretical basis for the treatment of swine wastewater with high ammonia nitrogen content using microalgae cultures.

[Start-up of a Three-stage PN/A Granular Sludge Reactor for Treating Wastewater with High Concentrations of Ammonia].

In order to apply partial nitritation-ANAMMOX (PN/A) technology to treat wastewater with high concentrations of ammonia, autotrophic nitrogen-removing granular sludge was crushed and inoculated into a three-stage continuous flow reactor. The nitrogen loading rate (NLR), dissolved oxygen (DO) concentration, and free ammonia (FA) levels in each compartment of the reactor were controlled over a 106-day period. Results showed that the nitritation process occurred with the inoculated granules during the initial phase. A limited aeration strategy was employed in the reactor at relatively high NLRs. Given the effective suppression of nitrite-oxidizing bacteria and the prevention of ANAMMOX bacteria from high DO conditions, the compact structure and nitrogen-removal activity of the granules could be improved. When the ammonia-nitrogen concentration was increased in the influent to 350 mg·L-1, the adverse impacts of high FA concentrations on the functional microbe activity in the first compartment should be eliminated. This occurs by reducing the influent pH and alkalinity dosage. This occurs by reducing the influent pH and degree of alkalinity. As a result, a total nitrogen removal rate of 7.2 kg·(m3·d)-1 was achieved in the reactor, which is 50 to 100 times higher than that of conventional activated sludge systems. The consistent improvement in the nitrogen-removal activity of the granules was demonstrated by batch testing at different aeration intensities. This showed that activity was greatest in the first compartment, which showed the highest granular maturity. In addition, a clear linear correlation (R2>0.97) was observed between the amount of extracellular polymeric substance and the specific nitrogen removal rate. This indicated that the dense granules played a positive role in enhancing the performance of the reactor.