Ammonia Inhibition Research Articles

Mitigating ammonia inhibition in anaerobic digestion with lignin-based carbon materials synthesized by hydrothermal carbonization

Ammonia inhibition poses a significant challenge to the efficient and stable operation of anaerobic digestion (AD) systems by leading to the inhibition of volatile fatty acid conversion and reduced methane production. This study explores the utilization of lignin-based hydrochar (LHC) and carbon quantum dots (CQDs) produced via hydrothermal carbonization of alkali lignin to alleviate ammonia inhibition in AD processes. The results showed that both LHC and CQDs help counter the decline in methane yield and production rate typically associated with ammonia inhibition. Notably, the addition of 1 g/L CQDs significantly increased methane production by 24.25% compared to the control group. While LHC showed limited ammonia adsorption, its primary impact was enhancing direct interspecies electron transfer (DIET) through improved redox capacity and promoting humic acid-like organics formation. In contrast, CQDs reduced charge transfer resistance, significantly enhancing system redox capacity. Optimizing the hydrothermal carbonization temperature of LHC to 250 °C further optimized its redox properties, boosting methane production by 30.53% at a concentration of 3 g/L. Microbial community and metabolic pathway analyses indicated that LHC and CQDs enriched hydrolytic and acidifying bacteria, as well as DIET-associated microorganisms, facilitating efficient volatile fatty acid production and conversion. This process enabled the sustained operation of both acetoclastic and hydrogenotrophic methanogenic pathways, effectively mitigating the adverse effects of high ammonia nitrogen concentrations.Graphical

Characterization of Magnesium-Iron Modified Biochar to Alleviate Ammonia Inhibition and Enhance Anaerobic Digestion of Chicken Manure

Characterization of Magnesium-Iron Modified Biochar to Alleviate Ammonia Inhibition and Enhance Anaerobic Digestion of Chicken Manure

Achieving stable partial nitrification through synergistic inhibition of free ammonia and salinity on nitrite-oxidizing bacteria

Achieving stable partial nitrification through synergistic inhibition of free ammonia and salinity on nitrite-oxidizing bacteria

Enhancing low-temperature anaerobic digestion of nitrogen-rich feedstocks: Mitigating free ammonia and short-chain fatty acid inhibitions

Enhancing low-temperature anaerobic digestion of nitrogen-rich feedstocks: Mitigating free ammonia and short-chain fatty acid inhibitions

PH Adjustment Alleviates Ammonia Inhibition of Cell Proliferation During a Short Resting Period in Semi-continuous Anaerobic Digestion of Food Waste

pH Adjustment Alleviates Ammonia Inhibition of Cell Proliferation During a Short Resting Period in Semi-continuous Anaerobic Digestion of Food Waste

The characteristics of thermophilic anaerobic bacteria in coal and its methanogenesis mechanism

The research on the characteristics and metabolism of thermophilic methanogens in coal under high temperature conditions is helpful to the development and utilization of deep coalbed methane, improving the potential of microbial methanogenesis and carbon dioxide emission reduction, and expanding the application scope of Coalbed Gas Bioengineering. Therefore, the lean coal in central and southern region of Henan, China with abnormal ground temperature was used as the substrate, and the microorganisms in coal seam water were used as the source of bacteria. The experiments were carried out at 50 °C, 55 °C, 60 °C, 65 °C and 70 °C, respectively. The results showed that hydrogenotrophic methanogenesis was the primary pathway of methane generation by thermophilic anaerobic digestion of coal. The hydrolysis products were consumed by hydrolysis bacteria Coprothermobacter, Acetomicrobium and acetic acid oxidizing bacteria Tepidanaerobacter to produce a large amount of H2 and CO2. Then CO2 was reduced to CH4 by the hydrogenotrophic methanogen Methanothermobacter. From all aspects, 55 °C was the most suitable for coal thermophilic anaerobic digestion to produce methane. At this temperature, the biomethane production at the peak of biogas production could reach 0.45 mL/g, and the cumulative production was 1.81 mL/g. The content of glycosyl transferases (GTs) was found to be the lowest in the anaerobic digestion system operating at 50 °C, resulting in the lowest coal degradation rate. In the 60 °C and 65 °C systems, cellular processes and the utilization of organic compounds exhibited lower activity compared to the 55 °C system, resulting in reduced methane production. Pyruvate metabolism and glycine metabolism were strongest at 70 °C, which could easily lead to acid accumulation and ammonia inhibition. The comprehension of this concept will establish a foundation for mitigating detrimental factors during the implementation process of Coalbed Gas Bioengineering under elevated temperatures.

Long-term effects of dead algal deposition on sediment surfaces: Behavior of endogenous phosphorus release in sediments

Algae blooms are frequently triggered owing to the improvements in aquatic trophic levels. The aggregated algae from these blooms are eventually dead and accumulate on sediment surfaces, impacting the microenvironment and phosphorus cycling in aquatic systems. However, research on the effects of naturally dead algal deposition on endogenous P release from sediments is lacking. In this study, we investigated the long-term effects of dead algal deposition at varying concentrations on P release from sediments and the underlying mechanisms by assessing microbial metabolism and community structure. The results showed that following the dead algal deposition, the release of P from sediments to the water column peaked on day 40 (0.14±0.017 mg L-1 in Amend12) and the SRP exchange capacity reached maximum (6.09 ± 1.63 mg/(cm2·d) in Amend12) at sediment-water interface in phase1 (0–3 day). This might be primarily attributed to the deposition of dead algae introducing much organic matter (such as organic carbon and organic phosphorus), thus altering the sediment microenvironment, which increased the activity of phosphorus-cycle microorganisms, such as polyphosphate-accumulating organisms, through increasing C source metabolism, reducing intracellular ammonia inhibition, and creating more suitable anaerobic conditions. Therefore, this study has improved our understanding of the management strategies for controlling endogenous phosphorus release in eutrophic shallow lakes, suggesting that the priming effects of freshly deposited algae could be mitigated by harvesting algae at the peak of blooms.

Effects of different quorum sensing signal molecules on alleviation of ammonia inhibition during biomethanation

Anaerobic digestion (AD) is a promising technology for achieving both organic wastes treatment and energy recovery. However, challenges such as ammonia inhibition still remain. Quorum sensing (QS) system is relevant with the regulation of microbial community behaviors by releasing and sensing signal molecules, which could improve methane production during AD process. Therefore, the current study explored the effects of different quorum sensing signal molecules on alleviation of ammonia inhibition. The results showed that both secretion of N-butyryl-DL-homoserine lactone (C4-HSL) and N-(β-ketocaproyl)-DL-homoserine lactone (3OC6-HSL) could be inhibited by high ammonia stress while stimulation of N-hexanoyl-L-homoserine lactone (C6-HSL) and N-octanoyl-DL-homoserine lactone (C8-HSL) secretion might be triggered by ammonia toxicity. Moreover, the alleviation of ammonia inhibition could be achieved by both introducing 3OC6-HSL (0.5 μM) and combination of 3OC6-HSL (0.1 μM) and biochar (4 g/L). Exogenous 3OC6-HSL could regulate microbial social behaviors and enhance the secretion of extracellular polymeric substances (EPS) to promote anaerobic digestion. In addition, the mitigation of ammonia inhibition through exogenous 3OC6-HSL and biochar were confirmed by microbial community changes (Methanobacterium, Propionicicella and Petrimonas). Critical enzymes involved in both acidification and methanogenic steps were enhanced after adding the combination of 3OC6-HSL and biochar. The combination of low levels of 3OC6-HSL and biochar could promote both direct interspecies electron transfer (DIET) process and communication between different anaerobic microorganisms to mitigate ammonia inhibition. The current study will provide primary insights for conquering ammonia inhibition during biomethanation.

Struvite crystallization eliminates ammonia inhibition in thermal hydrolysis of waste activated sludge: Role of Mg/P ratio

Thermal hydrolysis (TH) is a promising sludge pretreatment technology, but the ammonia it produces can be hazardous to subsequent anaerobic digestion (AD). This study assessed the potential of using struvite crystallization to mitigate ammonia inhibition in the AD process and examined the impact of the Mg/P ratio. The Mg/P ratio of 1.0 effectively reduced the ammonia concentration to 409 ± 22 mg/L, although methane production decreased by 14 %. Reducing the Mg/P ratio to 0.6 resulted in an 11 % increase in methane production. The study revealed that an excess of Mg2+ hindered sludge solubilization and inhibited the AD process by reducing enzyme activities, which led to a microbial community detrimental to methane production. This study provides a new idea to alleviate the ammonia inhibition of sludge AD, which is of great scientific value and practical significance for applying of struvite crystallization to TH.

Removal of ammonia from rubber wastewater using rubber-sludge-based biochar to enhance biogas production

Anaerobic digestion of rubber wastewater (ADRW) is an option for methane derivation for biogas production. However, the ammonia content in rubber wastewater, known as ammonia inhibition, has made the practical implementation of ADRW not yet feasible due to anaerobic digestion (AD) instability and low substrate degradation. Numerous studies have mentioned the use of biochar to overcome its inhibitory effect in AD. However, there are no report on the performance of rubber-sludge-based biochar (RSB) for removing ammonia from rubber wastewater to enhance biogas production. Therefore, this study investigates the potential of RSB to remove ammonia from wastewater to enhance biogas production. Initially, the RSB adsorbent was prepared by facile carbonization method and characterized with scanning electron microscopy (SEM), N2 physisorption, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis. The performance of the RSB adsorbent for ammonia removal from wastewater was examined using the one -factor -at -one -time (OFAT) adsorption method. The AD process was then conducted using the treated wastewater. The results show that RSB possessed significant porous structure with high carbon content and a surface area of 20.3218 m2/g. The highest ammonia removal was 7.5 mg/l at an initial adsorbent loading dosage of 1.5 g of RSB for 30 min of mixing. Further, during the AD process, the highest biogas yield of 19.061 ml/g was achieved after 28 days at pH 8. Approximately 83 % of the methane composition was obtained from the biogas yield, indicating that the RSB contributes to the enhancement of biogas production by removing ammonia from rubber wastewater.

Mechanisms of horizontal gene transfer and viral contribution to the fate of intracellular and extracellular antibiotic resistance genes in anaerobic digestion supplemented with conductive materials under ammonia stress

The addition of conductive materials (CMs) is an effective strategy for mitigating ammonia inhibition during anaerobic digestion (AD). However, the introduction of CMs can result in increased antibiotic resistance genes (ARGs) pollution, potentially facilitated by enhanced horizontal gene transfer (HGT). The complex dynamics of intracellular and extracellular ARGs (iARGs/eARGs) and the mechanisms underlying their transfer, mediated by CMs, in ammonia-stressed AD systems remain unclear. In this study, we investigated the effects of three commonly used CMs—nano magnetite (Mag), nano zero-valent iron (nZVI), and granular activated carbon (GAC)—on the fate of iARGs and eARGs during the AD of waste activated sludge under ammonia stress. The results revealed an unexpected enrichment of iARGs by 1.5 %–10.9 % and a reduction of eARGs by 14.1 %–25.2 % in CM-supplemented AD. This discrepancy in the dynamics of iARGs and eARGs may be attributed to changes in microbial hosts and the horizontal transfer of ARGs. Notably, CMs activated prophages within antibiotic-resistant bacteria (ARB) and their symbiotic partners involved in vitamin B12 provision, leading to the lysis of ARB and the subsequent release of eARGs for transformation. Additionally, the abundance of potentially mobile ARGs, which co-occurred with mobile genetic elements, increased by 56.6 %–134.5 % with CM addition, highlighting an enhanced potential for the HGT of ARGs. Specifically, Mag appeared to promote both transformation and conjugation processes, while nZVI only promoted conjugation. Moreover, none of the three CMs had any discernible impact on transduction. GAC proved superior to both nano Mag and nZVI in controlling the enrichment of iARGs, reducing eARGs, and limiting HGTs simultaneously. Overall, these findings provide novel insights into the role of viruses and the mechanisms of ARG spread in CM-assisted AD, offering valuable information for developing strategies to mitigate ARG pollution in practical applications.

High rate methanogenesis and nitrogenous component transformation in the high-solids anaerobic digestion of chicken manure enhanced by biogas recirculation ammonia stripping

High-solids anaerobic digestion is a promising technology for treating animal manure. However, the high nitrogen content in chicken manure leads to severe ammonia inhibition, thereby hindering the application of this technology for chicken manure. This study operated a high-solid anaerobic system feeding the reactor with 20 % total solids (TS) chicken manure for 650 days to investigate whether the anaerobic metabolic performance could be enhanced by adopting biogas recirculation ammonia stripping. The results show that, with ammonia stripping, the total ammonia nitrogen (TAN) was reduced from 8.2 to 3.0 g/L. The methanogenic activity was enhanced 1.3 – 2.9 fold. This led to a low level of volatile fatty acids (VFA, 0.6 g/L) and a high methane yield of 0.3 L/g-volatile solids (VS). Protein decomposition was facilitated under stripping conditions and correlated with a higher abundance of protein decomposition bacteria and enhanced methane production. The dynamics of ammonium formation and removal were illustrated for different stripping conditions. The ability to maintain low ammonium and the carbon and nitrogen balance was also verified. The proven effectiveness observed in this long continuous experiment may provide a foundation for further demonstrating the high-solids anaerobic digestion of chicken manure.

Rapid achievement of partial nitrification process by adopting the combined strategy of anoxic starvation and free ammonia inhibition

ABSTRACT Partial nitrification (PN) is a prerequisite step for the short-cut nitrogen removal process, which is crucial to provide stable nitrite accumulation for subsequent units. The present study innovatively proposed a new strategy for the rapid establishment of PN by adopting short-term anoxic starvation combined with high free ammonia inhibition. The sludge obtained from the secondary sedimentation tank of a municipal wastewater treatment plant was starved for 7 days under anoxic conditions, and then wastewater with high ammonia nitrogen (400 mg L−1) was introduced. Within 17 days, stable nitrite accumulation was achieved in the sequencing batch reactor, and the nitrite accumulation rate reached more than 95.0%. The activity of ammonia monooxygenase enzyme increased from 0.0364 ± 0.0074 to 0.1275 ± 0.0021 μg NO2 −-N·mg−1 protein min−1, while that of hydroxylamine oxidoreductase enzyme increased from 1.5350 ± 0.0208 to 6.3852 ± 0.0400 EU g−1 SS. The relative abundance of Nitrosomonas increased from 0.10% to 25.90%, while that of Nitrospira consistently remained below 0.04%. And the relative abundance of short-cut denitrifying bacteria, including Truepera, OLB8, and OLB13 all increased. The results proved that the short-term anoxic starvation combined with high free ammonia inhibition was an effective strategy for rapid establishment of PN.

Ammonia inhibition in anaerobic digestion of organic waste: a review

AbstractAnaerobic digestion (AD) has become the technology of choice for organic waste treatment as an environmentally beneficial and sustainable waste treatment technology. However, the nitrogen content of these organic waste streams is generally high. Ammonia is produced in the biodegradation of nitrogenous organic matter. Low concentrations of ammonia favour AD, but high concentrations can lead to digestive system failure. To address the issue of ammonia inhibition and ensure the stability of the digestive system, numerous physical, chemical, and biologicalmethods aimed at controlling ammonia levels and/or strengthening the biological processes have been proposedand developed. Literature evidence suggests that differences in AD reaction conditions and microbial sources result in different tolerances of the digestive system to ammonia and nitrogen. This paper summarises and compares the inhibitory effects of ammonia nitrogen under different conditions and the existing regulatory measures to alleviate ammonia nitrogen inhibition. In addition, since the core of the digestive system is microorganisms, this paper explains the mechanism of ammonia stress especially at the microbial level, and in this way, it explores the future direction of research using biofortification. This review provides a theoretical reference for solving the problem of ammonia nitrogen inhibition.

Biochar confers significant microbial resistance to ammonia toxicity in n-caproic acid production

Microbial chain elongation integrating innovative bioconversion technologies with organic waste utilization can transition current energy-intensive n-caproic acid production to sustainable circular bioeconomy systems. However, ammonia-rich waste streams, despite their suitability, pose inhibitory challenges to these bioconversion processes. Herein, biochar was employed as an additive to enhance the activity of chain elongating microbes under ammonia inhibition conditions, with an objective to detail underlying mechanisms of improvements. Biochar addition significantly improved chain elongation performance even under severe ammonia stress (exceeding 8 g N/L), increasing n-caproic acid yields by 40 % to 158 % and reducing lag times by 51 % to 90 %, compared with the best-performing group without biochar addition. The material contribution to n-caproic production reached up to 94.3 % (at 4 g N/L). These enhancements were mainly attributed to the new electron syntrophy induced by biochar, which improved electron transfer system activity and electrical conductivity of the fermentation system. This is further substantiated by increased relative abundances of the genus Sporanaerobacter, electroactive bacteria, and up-regulated direct electron transfer-related genes including conductive pili and c-type cytochrome. This study demonstrates that biochar can confer robust resilience to ammonia toxicity in functional microbes, paving a way for efficient and sustainable n-caproic acid production.

Distinct Mechanisms between Free Iron Species and Magnetite Addition in Anaerobic Digestion on Alleviating Ammonia Inhibition

Distinct Mechanisms between Free Iron Species and Magnetite Addition in Anaerobic Digestion on Alleviating Ammonia Inhibition

Disentangling microbial niche balance and intermediates’ trade-offs for anaerobic digestion stability and regulation

Anaerobic digestion (AD) is a key technology for converting organic matters to methane-rich biogas. However, nutrient imbalance can destabilize the whole digestion. To realize stable operation of AD and improve its efficiency, this work considers a new strategy to control the intermediate concentrations of poor AD under nutrient stress. For this purpose, long-term digestion under different nutrient conditions was investigated. Results showed that the feedstock with a low C/N ratio (= 6) caused VFA accumulation (2072 ± 632 mg/L), leading to the inhibition of methane production. Employing a substrate with a higher C/N ratio (= 11) and/or adding NH4HCO3 (200 mg NH4+-N/Ladd) could alleviate the VFA inhibition, but excessive dosage of NH4HCO3 would induce ammonia inhibition. Through the established digestion balance between free ammonia nitrogen (FAN) between 0 and 25 mg/L, volatile fatty acid (VFA) 510–2100 mg/L, and alkalinity (ALK) 3300–7800 mg/L, an efficient methane yield of 150–250 mL/g VS was achieved and stable operation of AD under nutrient stress (low C/N ratio) was realized. Metabolic reconstruction between Euryarchaeota sp. MAG162, Methanosarcina mazei MAG53 and Mesotoga infera MAG119 highlighted that microbial niche balance was developed as a result of digestion balance, which is beneficial for stable operation of AD. These findings improved our understanding of the interaction mechanism between intermediates and microbial niches for stability control in AD.

Ammonia-induced constraints on butyrate degradation in anaerobic digestion: Impact of ammonia levels and pH conditions, and recovery behaviour

The accumulation of butyrate is a recurrent phenomenon in anaerobic digesters utilizing animal manure as the primary feedstock. Despite its prevalence, the factors governing the anaerobic degradation of butyrate remain inadequately explored. In this study, a series of experiments were carried out under different total ammonia concentrations (TAN, 0.18–20 g N/L) and pH conditions (7.0–8.0) to investigate the inhibition of butyrate anaerobic degradation by different ammonia species (NH4+ and NH3) and to assess the recoverability following severe ammonia inhibition. The findings indicate that at pH 7.5, butyrate degradation experienced remarkable inhibition when TAN exceeded 8.0 g N/L, while no discernible impact was observed at pH 7.0–8.0 and 4.0 g TAN/L. Additionally, the lag phase for butyrate degradation extended with increasing TAN concentration. Notably, the activity of butyrate-degrading bacteria exhibited full recovery from severe ammonia inhibition (TAN 20 g N/L or NH3 779.2 mg N/L), provided prolonged adaption time was allowed. The analysis using a modified Monod inhibition model highlighted that NH4+ contributed more to inhibition than NH3 at TAN concentrations of 2.0–20.0 g N/L. Therefore, simply reducing pH levels would not adequately counteract ammonia inhibition. Implementing an extended hydraulic retention time emerges as an effective measure to reduce butyrate accumulation in anaerobic digestion systems, particularly the feedstock being nitrogen-rich materials (e.g., animal manure).

Synergistic effect and microbial community structure of waste-activated sludge and kitchen waste solids residue mesophilic anaerobic co-digestion.

Anaerobic co-digestion was conducted on the solid residues after three-phase separation of kitchen waste (KWS) and waste-activated sludge (WAS), the synergistic effects and process performance were studied during co-digestion at different ratios of KWS to WAS. KWS and WAS mix ratios of 0:1, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1 and 1:0 (based on TS). The results showed that a ratio of KWS to WAS of 1:1 got a very high methane recovery with a methane yield of 310.45 ± 30.05 mL/g VSadded. The highest concentration of free ammonia among all reaction systems was only 70.23 ± 5.53 mg/L, which was not enough to produce ammonia inhibition in the anaerobic co-digestion system. However, when the KWS content exceeded 50%, methane inhibition and prolongation of the lag phase were observed due to the accumulation of volatile fatty acids (VFAs), and during the lag phase. Microbial community analysis showed that various bacterial groups involved in acid production and hydrolysis were mainly dominated by phylum Firmicutes, Chloroflexi, Proteobacteria and Bacteroidetes. Hydrogenotrophic methanogen was found to dominate all archaeal communities in the digesters. Co-digestion of KWS with WAS significantly increased the relative abundance of Methanobacterium compared with anaerobic digestion of WAS alone.

Regulatory mechanisms of biochar alleviating ammonia inhibition to methanogenesis during long-term operation of anaerobic membrane bioreactor treating swine wastewater

Anaerobic Membrane Bioreactor (AnMBR) is regarded as an advanced technology for the anaerobic digestion (AD) of swine wastewater. However, the high ammonia level in swine wastewater is a crucial issue to inhibit methane production. This study aimed to establish a biochar-assisted AnMBR (BC) to mitigate ammonia inhibition during AD of swine wastewater. As the gradual ammonia loading rate (ALR) increased from 3.0 g/L to 6.0 g/L, BC maintained methane yields ranging from 74.9 % to 48.1 %, which were 9.1 % to 33.3 % higher than those of a regular AnMBR (CT). Moreover, the COD removal efficiency steadily surpassed 80 %. Although the increase in ALR had negative effects on both BC and CT, the presence of biochar enhanced the methanogenic activity of bulk sludge, specifically accelerating processes involved in syntrophic acetate oxidation and CO2-reducing methanogenesis under high ALR conditions. Integrated characterizations using PARAFAC-based EPS analysis, INT-ETS, and WO3 probe-based extracellular electron transfer (EET) activities indicated that biochar stimulated the secretion of humic-like and aromatic protein-like compounds in the TB-EPS, which likely established a redox-active matrix with biochar between VFA oxidation bacteria and CO2-reducing methanogens to facilitate EET. This potentially made the syntrophic VFA oxidation with favorably thermodynamic kinetics under high ammonia stress. Furthermore, the analysis of microbial community coupling prediction of functional genes associated with methanogenic pathways revealed that as ALR increased, the presence of biochar re-shaped the microbial communities by enriching electro-active Syntrophomonas and Methanosarcina/Methanospirillum, which mainly triggering EET-based syntrophic methanogenesis by accelerating the intracellular enzymatic transformation from Formylmethanofuran to 5,10-Methylenetetrahydromethanopterin process. We expect the major findings of this study provide new insights to understand the mechanisms of biochar alleviating ammonia inhibition during long-term operation of AnMBR.