High Ammonia Concentrations Research Articles

Growth of Scenedesmus obliquus in anaerobically digested swine wastewater from different cleaning processes for pollutants removal and biomass production

Anaerobically digested swine wastewater (ASW) purification by microalgae provides a promising strategy for nutrients recovery, biomass production and CO2 capture. However, the characteristics of ASW from different cleaning processes vary greatly. At present, the cultivation of microalgae in ASW from different manure cleaning processes is rarely investigated and compared. That may bring uncertainty for microalgae growth using different ASW in large-scale application. Thus, the ASW from three cleaning processes were tested for cultivating microalgae, including manure dry collection (I), water flushing (II) and water submerging processes (III). The characteristics of ASW from three manure cleaning processes varied greatly such as nutrient and heavy metals levels. High concentration of ammonia and copper in ASW significantly inhibited microalgae growth. Fortunately, the supply of high CO2 (10%) effectively alleviated negative influences, ensuring microalgal growth at low dilution ratio. The characteristics of three ASW resulted in significant differences in microalgae growth and biomass components. The maximal biomass production in optimal diluted ASW-I, II and III reached 1.46 g L−1, 2.19 g L−1 and 2.47 g L−1, respectively. The removal of organic compounds, ammonia and phosphorus by optimal microalgae growth in diluted ASW-I, II and III was 50.6%/94.2%/64.7%, 63.7%/82.3%/57.6% and 83.2%/91.7%/59.7%, respectively.The culture in diluted ASW-I, II and III obtained the highest lipids production of 12.1 mg L−1·d−1, 16.5 mg L−1·d−1 and 19.4 mg L−1·d−1, respectively. The analysis of lipids compositions revealed that the proportion of saturated fatty acids accounted for 36.4%, 32.4% and 27.9 % in optimal diluted ASW-I, II and III, as ideal raw materials for biodiesel production.

Integrated water quality dynamics in Wadi Hanifah: Physical, chemical, and biological perspectives.

The Wadi Hanifah, a crucial aquatic ecosystem, has unfavorable consequences from natural occurrences and human activities. Recognizing the critical need for sustainable water management, this study provides an in-depth evaluation of wadi water quality. A comprehensive assessment was conducted, analyzing physical properties (temperature, pH, electrical conductivity, turbidity, color, and odor), chemical constituents (nitrogen compounds, ion concentrations, heavy metals), and bacterial diversity. The study found significant temperature fluctuations, particularly in sun-exposed or stagnant water areas. The water exhibited slight alkalinity and variable electrical conductivity and turbidity, indicating differing pollution levels. High ammonia and heavy metal concentrations suggested organic and industrial contamination, respectively. In addition, the prevalent fecal-indicator bacteria pointed to possible sewage or agricultural runoff. The research highlights the complex interplay of natural and anthropogenic factors affecting Wadi Hanifah's water quality. It emphasizes the need for location-specific environmental management strategies focusing on pollution control and conservation to safeguard the wadi's ecological health. This study provides vital insights for effective water resource management in Wadi Hanifah, serving as a model for similar ecosystems.

Abundant urinary amino acids activate glutamine synthetase-encoding glnA by two different mechanisms in Escherichia coli.

Growth of uropathogenic Escherichia coli in the bladder induces transcription of glnA which codes for the ammonia-assimilating glutamine synthetase (GS) despite the normally suppressive high ammonia concentration. We previously showed that the major urinary component, urea, induces transcription from the Crp-dependent glnAp1 promoter, but the urea-induced transcript is not translated. Our purpose here was to determine whether the most abundant urinary amino acids, which are known to inhibit GS activity in vitro, also affect glnA transcription in vivo. We found that the abundant amino acids impaired growth, which glutamine and glutamate reversed; this implies inhibition of GS activity. In strains with deletions of crp and glnG that force transcription from the glnAp2 and glnAp1 promoters, respectively, we examined growth and glnA transcription with a glnA-gfp transcriptional fusion and quantitative reverse transcription PCR with primers that can distinguish transcription from the two promoters. The abundant urinary amino acids stimulated transcription from the glnAp2 promoter in the absence of urea but from the glnAp1 promoter in the presence of urea. However, transcription from glnAp1 did not produce a translatable mRNA or GS as assessed by a glnA-gfp translational fusion, enzymatic assay of GS, and Western blot to detect GS antigen in urea-containing media. We discuss these results within the context of the extremely rapid growth of uropathogenic E. coli in urine, the different factors that control the two glnA promoters and possible mechanisms that either overcome or bypass the urea-imposed block of glutamine synthesis during bacterial growth in urine.IMPORTANCEKnowledge of the regulatory mechanisms for genes expressed at the site of infection provides insight into the virulence of pathogenic bacteria. During urinary tract infections-most often caused by Escherichia coli-growth in urine induces the glnA gene which codes for glutamine synthetase. The most abundant urinary amino acids amplified the effect of urea which resulted in hypertranscription from the glnAp1 promoter and, unexpectedly, an untranslated transcript. E. coli must overcome this block in glutamine synthesis during growth in urine, and the mechanism of glutamine acquisition or synthesis may suggest a possible therapy.

Enhanced ammonia recovery from wastewater by a transmembrane electro-chemisorption system directly connecting anode chamber and cathode chamber with gas permeable membrane

A transmembrane electro-chemisorption (TMECS) system was developed via directly connecting anode chamber (AnC) and cathode chamber (CaC) with a hydrophobic gas permeable membrane (GPM). The special structure of the TMECS system with AnC and CaC at two sides of GPM contributed to both forming localized extreme pH layers at two sides of GPM and using electrical field forces to enrich NH4+, thus realizing on-site utilization of authigenic acid and base to enhance the ammonia recovery from wastewater. Increasing applied voltage (from 2.0 to 6.0 V) and salt concentration (from 80 to 500 mM) could improve the system performance by promoting water splitting and reducing internal resistance, respectively. The system showed wide applicability for the influent ammonia concentration (from 560 to 5000 mg NH4+-N/L) with the ammonia removal and recovery efficiencies of 61.9 %–77.1 % and 78.5 %–91.9 % at 24 h, respectively. For high influent ammonia concentration (5000 mg NH4+-N/L), a specific energy consumption of 21.8 kWh/kg N could be reached. Moreover, the system can be easily scaled up by stacking the TMECS units. Therefore, the system shows good prospects in saving chemicals, wide applicability and easy scale-up for ammonia recovery from wastewater.

Acclimation of Microbial Consortia to Ammonia and Salt in Methane Fermentation

As methane fermentation is inhibited by ammonia derived from organic waste, anaerobic microbial communities tolerant to enriched wastewater with high concentrations of ammonia and salt must be obtained for methane fermentation. Therefore, acclimation cultures were prepared in bottles for 60–80 weeks with artificial wastewater medium added every 2 weeks, using three types of sludge from wastewater treatment plants in food factories. These cultures were maintained without substantially decreasing methanogenesis and gradually increasing NH4-N and salt concentrations to 5 and 34 g/L, respectively, via the accumulation of ammonia and salt through anaerobic digestion and direct addition. The culture did not show the severe inhibition of methanogenesis or the accumulation of volatile fatty acids (VFAs) such as acetic and propionic acids. The analysis of bacterial consortia in the acclimated sludge based on the 16S rRNA sequence showed that hydrogenotrophic methanogenic bacteria of the genus Methanoculleus were dominant among archaea, whereas bacteria from the orders Clostridiales and Bacteroidales were dominant among eubacteria. Further, VFA-assimilating bacteria, including synthetic acetate-oxidizing bacteria coupled with hydrogenotrophic Methanoculleus to convert methane from acetate, were present to prevent the excessive accumulation of VFAs in the acclimation culture. The proposed acclimation process can enhance the anaerobic digestion of wastewater for methane production.

Possible pathogenetic role of ammonia in liver cirrhosis without hyperammonemia of venous blood: The so-called latency period of abnormal ammonia metabolism.

Ammonia plays a crucial role in the pathogenesis of hepatic encephalopathy. Ammonia is also involved in many other pathological conditions seen in cirrhosis, such as sarcopenia, liver fibrosis, hepatocellular injury, immune dysfunction, and hyperammonemia. Furthermore, the ammonia level of the veins is a useful prognostic factor for cirrhosis. In cirrhosis without hyperammonemia of the vein, however, covert hepatic encephalopathy has been reported. This discrepancy is because of the anatomical features of ammonia metabolism. There are two systems in the body for detoxifying ammonia: one is the urea cycle in the liver, and the other is the glutamine synthesis pathway in skeletal muscle and other tissues. The blood processed in the liver's urea cycle is then transported via arteries to various organs. Further processing occurs in the brain and skeletal muscle's glutamine synthesis pathway before entering the veins. When the urea cycle function decreases in cirrhosis, the ammonia levels in the artery increase. In response, the glutamine synthesis pathway compensates by increasing the capacity to process ammonia. Therefore, the ammonia concentration in the veins downstream of skeletal muscles does not increase immediately. However, the brain and skeletal muscles, which receive arterial blood, might be exposed to high ammonia concentrations. In addition, branched-chain amino acids in venous blood decrease. This period is the transition phase from early- to late-phase cirrhosis, and understanding the pathophysiology during this stage is extremely important for preventing the progression of cirrhosis.

Treatment and Handling of Hydraulic Shock Load of Urea Fertilizer Wastewater in Sequencing Batch Reactor

The production process in the urea fertilizer industry produces wastewater with a very high ammonia content, which exceeds the quality standards for fertilizer wastewater. Therefore, it is necessary to treat urea fertilizer wastewater, which has a high ammonia content. One of the technologies that can be used to treat this type of wastewater is the Sequencing Batch Reactor (SBR) technology. The SBR technology was chosen because it only requires one reactor for the entire process, in which in conventional activated sludge systems it occurs in several reactors. Shock loading often occurs in wastewater treatment plants, including both organic shock loads and hydraulic shock loads. The waste used in the SBR operation in this research is urea fertilizer wastewater originating from a urea fertilizer industry in West Java, Indonesia. The parameters to be tested were COD, MLVSS, DO, pH, temperature, turbidity, and ammonia concentration. The results showed that the efficiency of reducing ammonia levels under normal loading with a flow rate of 300 mL/day was 99.5%, whereas when given a shock load of 600 mL/day, an efficiency of 98% was obtained. This proves that SBR can handle shock loads even though its efficiency slightly decreases.

Removal of Heavy Metals and Bulk Organics towards Application in Modified Constructed Wetlands Using Activated Carbon and Zeolites

Constructed wetlands are a versatile technology for various treatment approaches, especially in emerging countries. The research aims to study and optimize the hybridizing process of a vertical subsurface flow constructed wetland with adsorption technology to provide energy-efficient and sustainable removal of heavy metals and bulk organics before their discharge into water bodies or water reuse for irrigation. This study focuses on the adsorption of selected heavy metals present in sewage from Kanpur, India, a cluster of tanning industries and other relevant industrial polluters, investigating the pollutant adsorption onto activated carbon and zeolites in batch and column tests. The results of the batch tests indicated high zeolite loading rates for lead (91.6 mg/g), chromium (60.8 mg/g) and copper (47.4 mg/g). In the column tests applying different adsorbent combinations and ratios, the average removal rates were as follows: 54.6% for cadmium, 14.1% for chromium, 52.4% for copper, 2.2% for iron, 29.2% for manganese, 26.6% for nickel, 35.2% for lead and 44.6% for zinc. The column tests conducted in preparation for field testing in pilot wetlands showed that shorter retention times and background bulk organic concentrations, as well as high ammonium concentrations, negatively affected heavy metal removal by reducing the adsorption and ion exchange capacity of the adsorbents.

Wet H2S corrosion and degradation of pipeline in amine regeneration system

AbstractThe paper presents the results of non‐destructive testing examinations, metallographic tests and risk assessment of degradation related to corrosion of amine regeneration unit in a desulphurisation system. Intensive corrosion resulting from acid gases environment upon water condensation causes perforation of the pipeline. Detailed analysis reveals cracking related to the mechanism of wet H2S. Hydrogen penetration, resulting from the wet H2S process, causes a decrease in mechanical properties of steel and an increase in hydrogen content inside steel. Corrosion results mostly from high stream velocity, the presence of acid gases (with high ammonia content), the presence of amine and low stream temperature.

Microbiology of Big Soda Lake, a multi-extreme meromictic volcanic crater lake in the Nevada desert.

Big Soda Lake, Nevada, is a multi-extreme meromictic lake, whose hypersaline hyperalkaline bottom waters feature permanent anoxia and high concentrations of arsenic, sulphide and ammonia. These properties make Big Soda Lake-and the adjacent Little Soda Lake-a fascinating system for exploring life's boundaries, discovering novel microbial taxa and identifying biotechnologically useful strains. To date, the taxonomic diversity and metabolic capabilities of microorganisms in this system remain largely unknown. Here, we fill this gap using microbiome surveys across the Big and Little Soda Lake water columns, including 16S rRNA sequencing, fungal ITS2 sequencing and gene- and genome-resolved metagenomics. We accompany these surveys with measurements of salinity, pH, temperature, oxygen, ammonium and ammonia concentrations. Our analyses reveal rich bacterial communities, taxonomically and functionally differentiated along Big Soda Lake's oxycline and, to lesser extent, between lakes. Fungal communities were dominated by a small number of families, while nearly no archaea were detected. Pathways related to perchlorate reduction, anoxygenic phototrophy, fermentation, dissimilatory metabolism of arsenite/arsenate, sulphur compounds, nitrogen compounds and hydrogen, were particularly prevalent. A total of 129 high-quality bacterial and archaeal metagenome-assembled genomes (completeness ≥ 80%, contamination ≤ 5%) were recovered, yielding insight into the taxonomic distribution of microbial metabolic pathways.

High ammonia loading rate and biofilm reattachment initiated partial nitrification and anammox in a membrane aerated biofilm reactor

Inhibition of nitrite oxidizing bacteria (NOB) is important for efficient wastewater treatment via anammox. Here, a novel strategy was demonstrated, which based on the detachment and reattachment of the biofilm to establish partial nitrification and anammox in a membrane aerated biofilm reactor (MABR). The results showed that using free ammonia as the sole inhibitor to start up partial nitrification took more time, and NOB acclimated to the free ammonia inhibition. Detaching the biofilm made it possible for free ammonia to contact NOB in deeper zones of the biofilm while at the same time washing NOB out of the reactor. Nitrite accumulation efficiency (NAE) increased to 70 % in 50 days when both high ammonia loading and biofilm reattachment were applied. With a short hydraulic retention time and high concentrations of ammonia and nitrite, anammox activity appeared in the reactor and resulted in a nitrogen removal efficiency of 60 %. Microbial community analysis indicated that Nitrosomonas, Nitrospira, and Candidatus Brocadia were the main functional taxa. Anaerobic ammonia oxidizing bacteria (AnAOB) proliferated within the biofilm, inhibiting NOB growth by competing for nitrite. Endogenous denitrifying bacteria also grew, coexisting with AnAOB. Predicted abundance of genes related to fermentation correlated with those involved in denitrification, indicating the possibility of heterotrophic denitrification. These findings help further our understanding of biofilm control-based strategies for NOB management and have implications for establishing autotrophic nitrogen removal using MABRs.

Selective Recovery of Low-Concentration Light Rare Earth Ions from High-Concentration Ammonium Sulfate System by Coordination Ability

Selective Recovery of Low-Concentration Light Rare Earth Ions from High-Concentration Ammonium Sulfate System by Coordination Ability

Molecular Insights into the Synergistic Effects of Putrescine and Ammonium on Dinoflagellates.

Ammonium and polyamines are essential nitrogen metabolites in all living organisms. Crosstalk between ammonium and polyamines through their metabolic pathways has been demonstrated in plants and animals, while no research has been directed to explore this relationship in algae or to investigate the underlying molecular mechanisms. Previous research demonstrated that high concentrations of ammonium and putrescine were among the active substances in bacteria-derived algicide targeting dinoflagellates, suggesting that the biochemical inter-connection and/or interaction of these nitrogen compounds play an essential role in controlling these ecologically important algal species. In this research, putrescine, ammonium, or a combination of putrescine and ammonium was added to cultures of three dinoflagellate species to explore their effects. The results demonstrated the dose-dependent and species-specific synergistic effects of putrescine and ammonium on these species. To further explore the molecular mechanisms behind the synergistic effects, transcriptome analysis was conducted on dinoflagellate Karlodinium veneficum treated with putrescine or ammonium vs. a combination of putrescine and ammonium. The results suggested that the synergistic effects of putrescine and ammonium disrupted polyamine homeostasis and reduced ammonium tolerance, which may have contributed to the cell death of K. veneficum. There was also transcriptomic evidence of damage to chloroplasts and impaired photosynthesis of K. veneficum. This research illustrates the molecular mechanisms underlying the synergistic effects of the major nitrogen metabolites, ammonium and putrescine, in dinoflagellates and provides direction for future studies on polyamine biology in algal species.

Study on the removal of fulvic acid in water by potassium ferrate-enhanced iron-manganese co-oxide film and its mechanism.

The previous studies have shown that iron-manganese co-oxide film (MeOx) could simultaneously remove ammonium, manganese ion and bisphenol A. In this study, the removal of fulvic acid (FA) was explored by adding potassium ferrate (K2FeO4) to heighten the catalytic activity of MeOx. After adding about 3.0mg/L potassium ferrate, the elimination efficiency of 7.0mg/L FA by the MeOx increased from 20 to 50%. The effects of temperature and ammonium on the elimination of FA were investigated. Higher temperature (above 22°C) and higher ammonium concentration (above 2.0mg/L) caused a decrease in FA removal. Most of FA combined with the ferric hydroxide colloid produced by K2FeO4 in water to form macromolecular groups, and they were subsequently absorbed and covered on the surface of MeOx. Scanning electron microscope showed that more viscous flocs appeared on the surface of MeOx, and the film thickness became thicker. Electron energy-dispersive spectrometer analysis revealed a notable increased in the C-O element ratio and a significant decreased in the Mn-Fe element ratio on the surface of MeOx. From Fourier transform infrared spectroscopy, the content of transition metal carbonyl compounds increased in the surface of MeOx. XPS analysis confirmed that the presence of Fe3O4, FeO, Mn2O3 and Mn3O4 along with functional group substances of FA attached on the surface of MeOx. The removal mechanism of FA was studied.

Effect of ammonium/nitrate ratio on microalgae continuous cultures: Species-specificity of nutrient uptake and modelling perspectives

Microalgae-based wastewater treatment is promising in view of circularity as they can uptake most of the nitrogen sources usually present in waste streams: ammonium, nitrite and nitrate as well as some organic species. However, regulation pathways are not fully understood yet. This complexity is a challenge for accurate modelling of these processes, necessary for the design and optimization of wastewater treatment systems. It is generally observed in microalgae that the presence of ammonium inhibits the assimilation of other nitrogen compounds. This was confirmed in this work for Synechocystis sp. PCC6803, even in acclimated continuous cultures. A different uptake regulation was instead observed for the species Auxenochlorella protothecoides, able to uptake nitrate even when high concentrations of ammonium are present. From a modelling perspective, the Droop model was implemented to account for the exploitation of both ammonium and nitrate: a switch function was used to describe the ammonium inhibition, but this was applicable for Synechocystis only. For A. protothecoides, a changing nutrient uptake rate is needed, which was found to be function of the dissolved nitrogen concentration. A bioinformatic analysis was performed to infer putative players involved in nitrogen uptake, accounting for the different behavior of the two taxonomic groups.

Biogas Dynamics and Microbial Composition Employing Different Inocula and Substrates in Continuous Stirred-Tank Reactors

The current investigation delved into the utilization of cattle and municipal sanitary inocula for anaerobic digestion of poultry wastes, addressing a crucial and pragmatic challenge in waste management. The emphasis on poultry waste is pertinent due to its well-documented impediments in anaerobic digestion, attributed to heightened levels of ammonia and volatile fatty acids (VFAs). The strategic selection of cattle and municipal sanitary inocula suggests an approach aimed at bolstering the anaerobic digestion process. In this study, we evaluated the use of cattle and municipal sanitary inocula for the anaerobic digestion of various poultry wastes, which is often challenged by high levels of ammonia and volatile fatty acids (VFAs). The substrates tested included belt waste (Poultry A), poultry litter plus feed residues (Poultry B), tray hatchery ©, and stillage. These substrates were processed in two continuous stirred tank reactors (CSTRs), R-1 (with antibiotic monensin) and R-2 (without monensin). Initially, both reactors operated with the same hydraulic retention time (HRT), using a substrate ratio of stillage: belt: tray hatchery (S:B:T) of 70:15:15. On the 41st day, the HRT was adjusted to 20 days, and the substrate ratio was changed to S:A:T 70:40:40. The specific methane yield for R-1 started at 10.768 L g−1 COD, but decreased to 2.65 L g−1 COD by the end of the experiment. For R-2, the specific methane yield varied between 0.45 L g−1 COD and 0.243 L g−1 COD. Microbial composition in the reactors changed over time. In R-1, bacteroides were consistently dominant, while firmicutes were less abundant compared to R-2. Proteobacteria were initially low in abundance, but spirochetes were found in both reactors throughout the experiment. The study concluded that Poultry B substrates, due to their rich nutrient and trace element composition, are suitable for biogas plants. Municipal sanitary inocula also showed promise due to their resilience in high ammonia concentrations. Further research into biofilm interactions is recommended to better understand microbial responses to high ammonia concentrations, which can lead to propionate production in anaerobic digestion (AD).

Paper-based colorimetric hyperammonemia sensing by controlled oxidation of plasmonic silver nanoparticles.

High concentrations of ammonia in the human body can occur due to a wide variety of underlying causes such as liver cirrhosis and the symptoms of high ammonia concentrations are diffuse and hard to diagnose. The measurement of blood ammonia levels is an important diagnostic tool but is challenging to perform at the patient's bedside. Here, we present a plasmonic Ag nanoparticle-based ammonia sensor which provides a colorimetric optical readout and does not require specialised equipment. This is achieved using plasmonic Ag/SiO2 nanoparticles with the sensing mechanism that in the presence of OCl- they rapidly degrade reducing their plasmonic extinction and losing their characteristic colour. However, if ammonia is also present in the system, it neutralises the OCl- and thus the silver nanoparticles retain their plasmonic colour as can be measured by the naked eye or using a spectrometer. This sensing was further developed to enable measurements with animal serum as well as a implementing a facile "dip-stick" style paper-based sensor.

Effects of Ammonia (NH3) on Flame Characteristics of Methane (CH4) External Premixed Combustion

Methane has long been proposed as an alternative to heavy hydrocarbon fuels due to its low carbon content. However, considering the effect of climate change and the need to transition to zero-carbon, ammonia has recently gained popularity as a sustainable fuel. Nevertheless, previous studies have highlighted the poor combustion of ammonia and the need to blend it with other fuels like methane. As such, this study looks for parameters from the results of the fire of external combustion of premixed methane-ammonia gas. The study was conducted by burning stoichiometry first and then using a volume ratio as the content of the methane-ammonia mixture (ammonia concentration used 0-50%). The gas that comes out of the gas cylinder was adjusted in pressure and flow before mixing and then flowed into the burner to be combusted. The flame propagating from the burner was recorded in a high-speed camera and was used to define the combustion characteristics such as the flame height, flame angle, and dimensionless flame height. The higher concentration of ammonia in the fuel mixture was found to shorten the flame height and dimensionless flame height, while the flame angle became wider.

Comparison study on ammonia recovery from anaerobic digestion slurry by different biochar: Focusing on the effect of feedstock, pyrolysis temperature, and particle size

Treating anaerobic digestion (AD) slurry as industrial wastewater not only consumes a significant amount of energy but also wastes its inherent abundant nutrients, particularly the high ammonium content. Ammonia recovery from AD slurry has attracted attention in recent years and biochar has tentatively been used to adsorb ammonia nitrogen. However, most of the previous studies used pure ammonium chloride solution to simulate ammonia-rich wastewater and ignored the influence of other components. Furthermore, how the physico-chemical properties of biochar influence the adsorption performance of ammonia in AD slurry remains unknown. Therefore, this study focused on the investigation of the adsorption behavior of different types of biochar to ammonia nitrogen in AD slurry. Biochar generated from rice straw, coconut shell, and wood shaving under pyrolysis temperatures of 300 °C, 500 °C, and 700 °C were used to adsorb ammonia from food waste (FW) AD slurry, and five different particle sizes of biochar were also tested. The results showed that biochar derived from rice straw (up to 9.44 mg/g) and coconut shell (up to 8.86 mg/g) had higher ammonium adsorption capacity than biochar derived from wood shaving (up to 5.13 mg/g). Moreover, low pyrolysis temperature resulted in high adsorption capacity, while particle size and surface area of the biochar were not the critical factors determining the adsorption capacity. The correlation results demonstrated that the H/C (aromaticity), O/C (hydrophilicity), pH, electrical conductivity (EC), and ash content influenced the adsorption significantly. Based on the kinetics model results, it seems that physical adsorption was the main adsorption mechanism, while ion exchange and reaction with function groups also contributed to the adsorption. Moreover, the lower adsorption capacity was observed in this study where the real FW AD slurry was used as compared to other studies where pure ammonium chloride solution was used, which implied that microorganisms in FW AD slurry may colonize on the surface or pores of biochar, resulting in a negative effect on the adsorption capacity of biochar. The results derived from this study provided technical support for ammonia recovery of AD slurry.

Integrated dark-fermentation-microbial electrosynthesis for efficient wastewater treatment and bioenergy recovery

High ammonia concentration in wastewater can hinder methane production rate in anaerobic digestion (AD)-microbial electrosynthesis systems (ADMES). To address this issue, a dual-chamber reactor was fabricated using an anion exchange membrane (AEM) to separate the dark-fermentation (DF) and ADMES process, preventing ammonia migration from the DF chamber to the ADMES chamber. As a result, the DF-ADMES achieved a high methane yield based on chemical oxygen demand (COD) of 0.35 L CH4/gCOD compared to control operation AD (0.23 L CH4/gCOD) and ADMES (0.30 L CH4/gCOD). Additionally, hydrogen could be recovered from the DF chamber which improved the energy efficiency of the DF-ADMES reactor (91.7 %) as compared to control AD (53.4 %) and ADMES (71.9 %). Thus, a dual-chamber DF-ADMES with an AEM separator could be a feasible design for scalable treatment of high nitrogen-containing wastewater and high bioenergy recovery.