Nitrite Removal Research Articles

Metagenomic and Metatranscriptomic Analysis of Nitrogen Removal Functional Microbial Community of Petrochemical Wastewater Biological Treatment Systems

Petrochemicals are one of the pillar industries of China. Despite this, the treatment of petrochemical wastewater has long been seen as a massive challenge in the field of water pollution control, hindering the high-quality and sustainable development of the petrochemical industry. The majority of petrochemical enterprises and zones are located near rivers or seas, so their wastewater discharges can easily cause watershed or regional water ecological risks. Specifically, nitrogen pollution in petrochemical wastewater poses a significant threat to water ecological safety and human health. Sludge samples were collected from a petrochemical wastewater A/O nitrogen removal process line in a chemical industry zone in Shanghai. Metagenomic and metatranscriptomic methods were used to analyze the community structure of microorganisms, the functional characteristics of nitrogen removal bacteria, and the key nitrogen metabolism pathways in different sludges during the period when effluent water quality was stable and fluctuating. During the study, it was found that the nitrite and nitrate removal was relatively stable in this process, but ammonia oxidation fluctuated easily. In the study of microbial communities, it was found to be a nitrification-denitrification pathway that primarily removed nitrogen from the A/O process, and no genes related to ANAMMOX were detected. Approximately 90% of the functional genes responsible for removing nitrogen were responsible for denitrification, whereas only 0.17% of them were involved in the conversion of ammonia nitrogen in the nitrification process. Moreover, the abundance of ammonia-oxidizing bacteria in the process was extremely low, and the main genus was Nitrosomonas. It is likely that this is the main cause of fluctuations in ammonia nitrogen concentration in effluent due to water quality shocks in the process line.

Combined acute effect of salinity and substrate concentration on simultaneous sulfide and nitrite removal process

Nitrite or sulfide accumulation has always been a challenge for the treatment of saline or hypersaline wastewater. Simultaneous sulfide and nitrite removal process (SSNIR) targeting sulfide and nitrite as substrates, is a robust and potentially practical autotrophic denitrification biotechnology. Its feasibility to operate under hypersaline wastewater is not fully understood so far. Therefore, the current work explored the practicability of SSNIR to treat saline or hypersaline wastewater, evaluation of the toxicological effects of substrate and salinity on the denitrification and sulfide removal performance and product types. Additionally, the type of combined toxicity of substrate and salinity to SSNIR was determined. The results showed that the respective IC50 values for substrate shock on Specific sulfide oxidation activity (SSOA) and Specific denitrification activity (SDA) were 289.29 mg S/L and 300.92 mg S/L. The IC50 values of salinity shock on SSOA and SDA were 6.19 % wt (98.07 ms/cm) and 3.78 % wt (61.74 ms/cm), even the salinity level as high as 13.2 % wt (204 ms/cm) resulted in the reduction of 40 % nitrite removal efficiency. At salinity value>2.4 % wt (41 ms/cm), increase in salinity casted significantly positive effect on the nitrous oxide emission (P < 0.01). In addition, the combined salinity, substrate toxicity and salinity exposure value of<2.67 % wt (45 ms/cm) on SSNIR showed synergistic inhibition. A further increase in salinity (>45 ms/cm) alleviated the strength of synergistic inhibition and the effect on SSOA was identified as antagonistic inhibition.

Eficiência do reator ABR seguido de filtro anaeróbio na remoção de nutrientes e de organismospatogênicos em efluentes de processamento de pescado

ABSTRACT The aquaculture showed high growth along with the increase in the consumption of animal protein from this sector. The processing industries facilitate the preparation of fish for the consumer; however, they generate large volumes of effluents with a high polluting potential. Environmental legislation establishes norms for the release of effluents, making it necessary to implement treatment systems to reduce the pollutants generated. The objective of this work was to evaluate the performance of a compartmentalized anaerobic reactor (ABR) followed by an anaerobic filter (AF) treating fish processing effluent. The work was carried out in a slaughterhouse that had an effluent treatment station consisting of a static sieve, grease box, ABR reactor and anaerobic filter. Monitoring consisted of physical-chemical and biological analyzes of samples collected from the influent and effluents from each stage of treatment. The parameters evaluated were ammonia, nitrite, nitrate, NTK, phosphate and coliforms. The average results of the removal efficiency of these parameters, respectively, for the ABR reactor were 5, 40, 69, -19, -25 and 83%, and for the AF -0.5, 73, 53, 10, -17 and -17%. The system composed by the ABR reactor followed by the Anaerobic Filter showed high removal of nitrite, nitrate, and coliforms.

Effect of Mineral Carriers on Biofilm Formation and Nitrogen Removal Activity by an Indigenous Anammox Community from Cold Groundwater Ecosystem Alone and Bioaugmented with Biomass from a "Warm" Anammox Reactor.

Simple SummaryDuring more than 50 years of exploitation of the sludge repositories near Chepetsky Mechanical Plant (Glazov, Udmurtia, Russia) containing solid wastes of uranium and processed polymetallic concentrate, the soluble compounds entered the upper aquifer due to infiltration. Nowadays, this has resulted in a high level of pollution of the groundwater with reduced and oxidized nitrogen compounds. In this work, quartz, kaolin, and bentonite clays from various deposits were shown to induce biofilm formation and enhance nitrogen removal by an indigenous microbial community capable of anaerobic ammonium oxidation with nitrite (anammox) at low temperatures. The addition of a “warm” anammox community was also effective in further improving nitrogen removal and expanding the list of mineral carriers most suitable for creating a permeable reactive barrier. It has been suggested that the anammox activity is determined by the presence of essential trace elements in the carrier, the morphology of its surface, and most importantly, competition from rapidly growing microbial groups. Future work was discussed to adapt the “warm” anammox community to cold and provide the anammox community with nitrite through a partial denitrification route within the scope of sustainable anammox-based bioremediation of a nitrogen-polluted cold aquifer. In this unique habitat, novel species of anammox bacteria that are adapted to cold and heavy nitrogen pollution can be discovered.The complex pollution of aquifers by reduced and oxidized nitrogen compounds is currently considered one of the urgent environmental problems that require non-standard solutions. This work was a laboratory-scale trial to show the feasibility of using various mineral carriers to create a permeable in situ barrier in cold (10 °C) aquifers with extremely high nitrogen pollution and inhabited by the Candidatus Scalindua-dominated indigenous anammox community. It has been established that for the removal of ammonium and nitrite in situ due to the predominant contribution of the anammox process, quartz, kaolin clays of the Kantatsky and Kamalinsky deposits, bentonite clay of the Berezovsky deposit, and zeolite of the Kholinsky deposit can be used as components of the permeable barrier. Biofouling of natural loams from a contaminated aquifer can also occur under favorable conditions. It has been suggested that the anammox activity is determined by a number of factors, including the presence of the essential trace elements in the carrier and the surface morphology. However, one of the most important factors is competition with other microbial groups that can develop on the surface of the carrier at a faster rate. For this reason, carriers with a high specific surface area and containing the necessary microelements were overgrown with the most rapidly growing microorganisms. Bioaugmentation with a “warm” anammox community from a laboratory reactor dominated by Ca. Kuenenia improved nitrogen removal rates and biofilm formation on most of the mineral carriers, including bentonite clay of the Dinozavrovoye deposit, as well as loamy rock and zeolite-containing tripoli, in addition to carriers that perform best with the indigenous anammox community. The feasibility of coupled partial denitrification–anammox and the adaptation of a “warm” anammox community to low temperatures and hazardous components contained in polluted groundwater prior to bioaugmentation should be the scope of future research to enhance the anammox process in cold, nitrate-rich aquifers.

Evaluating bioretention scale effect on stormwater retention and pollutant removal.

Bioretention column studies are commonly used in laboratory to assess the performance of such structures in removal of pollutants and to investigate different conceptions aiming to increase their efficiency. However, no studies were found recommending suitable diameters or sizes, or about the uncertainties related to the transfer of results among the different scales (i.e., among different experiments or from the laboratory to field scale). This study assessed the effect of the varying diameters in experimental bioretention columns on the retention and removal of pollutants from stormwater runoff. Three sets of columns with diameters of 400mm, 300mm, and 200mm were assessed. The results showed that runoff retention (R) was affected by the time interval between stormwater events, but not by the bioretention diameter, although the diameter influenced the variability of R results. The removal of TSS (95%), nitrite (98%), and phosphate (96%) did present variability among the different bioretention diameters. However, the nitrate removal was statistically different among the bioretention columns, with removal efficiency above 50% in the 300-mm and 200-mm columns, while the 400-mm columns acted as a source of nitrate by increasing its concentration in the outflow stormwater by up to 285%, suggesting that the removal of this pollutant can be influenced by the scale effect of the bioretention columns and the experiments with small bioretention diameters may not provide reliable results.

Potential of biological sulphur recovery from thiosulphate by haloalkaliphilic Thioalkalivibrio denitrificans

ABSTRACT The aim of this study was to investigate the potential for elemental sulphur recovery from sulphurous solutions under aerobic and anoxic conditions by haloalkalophilic Thioalkalivibrio denitrificans at 0.8–19.6 g S2O3 2−-S L−1 and 0.2–0.58 g NO2 L−1, respectively. The experiments were conducted as batch assays with haloalkaline (pH 10 and ≥ 14 g Na+ L−1) thiosulphate solution. Aerobically, the highest biotransformation rate of thiosulphate obtained was 0.03 h−1 at 8.5 g L S2O3 2−-S. Based on Monod model, the maximum substrate utilisation rate (qm) was 0.024 h−1 with half saturation constant (Ks) 0.42 g S2O3 2−-S L−1 at initial [S2O3 2--S] of 14 g L−1. S0 accumulated at [S2O3 2−-S] ≥ 1.5 g L−1 (10% yield at initial 9.5 g S2O3 2−-S L−1) and the highest S0 yield estimated with the model was 61% with initial [S2O3 2--S] of 16.5 g L−1. Anoxically, the maximum nitrite removal rate based on Monod modelling was 0.011 h−1 with Ks = 0.84 g NO2 − L−1. Aerobically and anoxically the maximum specific growth rates (µm) were 0.046 and 0.022 h−1, respectively. In summary, high-rate aerobic biotransformation kinetics of thiosulphate were demonstrated, whereas the rates were slower and no S0 accumulated under anoxic conditions. Thus, future developments of biotechnical applications for the recovery of S0 from haloalkaline streams from the process industry should focus on aerobic treatment. Highlights Haloalkaline S2O3 2− biotransformations kinetics by Thioalkalivibrio denitrificans Aerobic thiosulphate-S bioconversion up to 0.024 h−1 with Ks = 0.42 g S2O3 2−-S L−1 10% S0 yield with initial 9.5 g S2O3 2--S L−1 in aerobic condition Anoxic NO2 removal up to 0.01 h−1 with Ks = 0.84 g NO2 − L−1

Nitrogen removal performance and rapid start-up of anammox process in an electrolytic sequencing batch reactor (ESBR)

In this study, the electrolytic sequencing batch reactor (ESBR) with different current densities was constructed to investigate the nitrogen removal performance and rapid start-up of anaerobic ammonia oxidation (anammox) process. The changes of total nitrogen removal rate (TNRR), specific anammox activity (SAA) and nitrogen concentration under different current densities were analyzed, and then the effect of the optimal current density on the start-up of anammox in ESBR was explored. The results showed that ammonium nitrogen removal efficiency (92.7%), nitrite nitrogen removal efficiency (15.5%) and total nitrogen removal efficiency (28.1%) were obtained with the TNRR and SAA were 0.0118 g N L−1 d−1 and 0.0050 g N (g Vss d)−1, respectively under the optimal conditions (i.e., current density = 0.10 mA cm−2, temperature = 36 °C and pH = 7.6). In addition, the stoichiometric ratio indicated that anammox was initiated successfully for 91 days in ESBR with the current density of 0.10 mA cm−2, which was shortened by 10 days compared with the conventional SBR without current density. These results suggest that an array of rapid start-up processes of anammox can be developed through applying current density to stimulate the activity of anammox bacteria (AnAOB).

Enhancement of denitrifying anaerobic methane oxidation via applied electric potential.

In this study, single-chamber three-electrode electrochemical sequencing batch reactor (ESBR) was set up to investigate the impact of applying potential on denitrifying anaerobic methane oxidation (DAMO) process. When the applied potential was +0.8V, the conversion rate of nitrite to nitrogen was superior to those of other potentials. With the optimal potential of +0.8V for 60 days, the nitrite removal rate of ESBR could reach 3.34±0.28mgN/L/d, which was 4.5 times more than that of the non-current control (0.74±0.16mgN/L/d). The DAMO functional bacteria Candidatus Methylomirabilis exhibited noticeable enrichment under applying potential, and its functional gene of pmoA was significantly expressed. Through untargeted LC-MS metabolomics analysis, applied potential was shown to affect the regulation of prior metabolites including spermidine, spermine and glycerophosphocholine that were related to the metabolic pathways of glycerophospholipid metabolism and arginine and proline metabolism, which had positive effects on DAMO process. These results show that applying electric potential could be a useful strategy in DAMO process used for methane and nitrogen removal.

Response of mixed community anammox biomass against sulfide, nitrite and recalcitrant carbon in terms of inhibition coefficients and functional gene expressions

Anaerobic ammonium oxidation (anammox) has evolved as a carbon and energy-efficient nitrogen management bioprocess. However, factors such as inhibitory chemicals still challenge the easy operation of this powerful bioprocess. This research systematically evaluated the inhibition kinetics of sulfide, nitrite, and recalcitrant carbon under a genomic framework. The inhibition at the substrate and genetic levels of sulfide, nitrite and recalcitrant carbon on anammox activity was studied using batch tests. Nitrite inhibition of anammox followed substrate inhibition and was best described by the Aiba model with an inhibition coefficient KI,NO2− of 324.04 mg N/L. Hydrazine synthase (hzsB) gene (anammox biomarker) expression was increased over time when incubated with nitrite up to 400 mg N/L. However, despite having the highest specific nitrite removal (SNR), the expression of hzsB at 100 and 200 mg N/L of nitrite was more muted than in most other samples with lower SNRs. Sulfide severely inhibited anammox activities. The inhibition was fitted with a Monod-based model with a KI,S2− of 4.39 mg S/L. At a sulfide concentration of 5 mg/L, the hzsB expression decreased throughout the experiment from its original value at he beginning. Recalcitrant carbon of filtrate from thermal hydrolysis process pretreated anaerobic digester had a minimal effect on maximum specific anammox activity (MSAA), and thus the value of the inhibition coefficient could not be calculated. At the same time, its hzsB expression profile was similar to that in the control. Resiliency and recovery tests indicated that the inhibition of nitrite (up to 400 mg N/L) and recalcitrant carbon (in 100% filtrate) were reversible. About 32% of MSAA was recovered after repeated exposures to sulfide at 2.5 mg/L, while at 5 mg/L, the inhibition was irreversible. Findings from this study will be helpful for the successful design and implementation of anammox in full-scale applications.

Effects of formaldehyde ( Parasite‐S ®) on biofilter nitrification from a cold and a warm freshwater RAS

The effect of Parasite-S® (an aqueous formaldehyde solution) on the nitrification processes of biofilters was evaluated in two recirculating aquaculture systems (RASs). Rearing tanks in the warmwater RAS contained yellow perch (Perca flavescens) and grass carp (Ctenopharyngodon idella) with an initial weight of 166.8 kg and a mean density of 39.5 kg/m3. Rearing tanks in the coldwater RAS contained rainbow trout (Oncorhynchus mykiss) and lake trout (Salvelinus namaycush) with an initial weight of 1377.8 kg at a system density of 41.9 kg/m3. Parasite-S® was administered to the entire system on four consecutive days in both trials to achieve a nominal concentration of 14.8 mg/L formaldehyde (40 mg/L formalin) at the biofilter. Removal efficiencies for total ammonia nitrogen (TAN) and nitrite nitrogen were measured as indicators of biofilter nitrification processes. The active ingredient in Parasite-S®, formaldehyde, was measured until it was below the method detection limit of 0.8 mg/L. TAN volumetric removal rate was significantly decreased in both systems after formaldehyde addition and remained below pre-exposure efficiency in the coldwater RAS. Nitrite nitrogen volumetric removal rate was not significantly different, but the slope and intercepts were less after formaldehyde addition indicating an effect on the nitrifying bacteria. Although removal rates were decreased, no mortality occurred after four consecutive formaldehyde indefinite bath exposures in either system.

Evaluation of the antioxidant effect of a phytocomplex addition in clean label pork salami enriched in n-3 PUFA

Control and n-3 PUFA enriched raw material was used to manufacture clean label and conventional salami; the former were added with a phytocomplex having iron chelating, DPPH, and FRAP activity, obtained from olive vegetation water, oregano, green tea and blueberry leaves, and with acerola powder. Salami were dried at 3 ± 1 °C until an established decrease in the combined pH and aw values, while only the conventional ones underwent a standard process. In the cold dried salami pH changes, aw and weight decrease were delayed; the phytocomplex contributed to lower the pH, and to prevent lipid and protein oxidation, despite the n-3 PUFA enrichment and heme iron release due to nitrite removal. TBARS and protein carbonyls were the highest in the nitrite-added salami undergoing cold and standard drying, respectively. The oxidation marker MDA tended to increase in the simulated digests of salami n-3 PUFA enriched or subjected to cold drying.

Different responses of representative denitrifying bacterial strains to gatifloxacin exposure in simulated groundwater denitrification environment

The impact of antibiotics on denitrification in the ecological environment has attracted widespread attention. However, the concentration threshold and inhibitory effect of the same antibiotic on denitrification mediated by mixed denitrifying microbes were conflicting in some studies. In this study, Paracoccus denitrificans, Acidovorax sp., and Pseudomonas aeruginosa were selected as representative denitrifying bacterial strains to explore the response of a single strain to gatifloxacin (GAT) exposure in groundwater denitrification. The results showed that the nitrate and nitrite removal efficiencies of Pseudomonas aeruginosa decreased by 34.87–36.25 % and 18.27–23.31 %, respectively, with exposure to 10 μg/L GAT, accompanied by a significant decline in denitrifying enzyme activity and gene expression. In contrast, the elevated denitrifying enzyme activity and gene expression of Paracoccus denitrificans promoted its nitrate and nitrite reduction by 2.09–10.00 % and 0–8.44 %, respectively. Additionally, there were no obvious effects on the removal of nitrate and nitrite by Acidovorax sp. in the presence of 10 μg/L GAT, which was consistent with the variation in denitrifying enzyme activity and total gene expression levels. The fit results of the Monod equation and its modification further elucidated the nitrate degradation characteristics from the perspective of denitrification kinetics. Furthermore, antibiotic resistance gene (ARG) analysis showed that the addition of 10 μg/L GAT (approximately 30 days) did not observably increase the relative abundance of ARGs. This study provides some preliminary understanding of the response differences of representative denitrifying bacterial strains to antibiotic exposure in groundwater denitrification.

Deciphering the Inhibition of Ethane on Anaerobic Ammonium Oxidation.

Anaerobic ammonium oxidation (anammox) and nitrification, two common biological ammonium oxidation pathways, are critical for the microbial nitrogen cycle. Short chain alkanes (C2-C8) have been well-known as inhibitors for nitrification through interaction with the ammonia monooxygenase, while whether these alkanes affect anammox is an open question. Here, this work demonstrated significant inhibition of ethane on anammox and revealed the inhibitory mechanism. The acute inhibition of ethane on anammox was concentration-dependent and reversible; 0.86 mM dissolved ethane caused 50% inhibition (IC50), and 1.72 mM ethane almost completely inhibited anammox. After long-term exposure to 0.09 mM ethane for 30 days, the ammonium (nitrite) removal rate dropped from 202 (267) mg N L-1 d-1 to 1 (1) mg N L-1 d-1, and the abundance of anammox bacteria decreased from 61.9% to 9.5%. The intercellular ammonium concentration of anammox bacteria decreased after ethane exposure, while metatranscriptome analysis showed significant upregulation of genes for ammonium transport of anammox bacteria. Thus, ethane could suppress ammonium uptake resulting in the inhibition of anammox activities. As ethane is the second most prevalent alkane after methane in various anoxic environments, ethane may have an important effect on the nitrogen cycle driven by anammox that should be investigated in future research.

Operating strategies to optimize a membrane bioreactor enriched in nitrite-dependent anaerobic methane-oxidizing bacteria

The use of N-damo bacteria, which can simultaneously remove nitrite and dissolved methane, could represent a cost-effective and sustainable alternative to minimize the environmental impact of effluents from methanogenic reactors treating domestic sewage. The operation of N-damo bacteria reactors is often not stable, and their activity decrease with no proven reason over time. This study aims to optimize the nitrite removal capacity of a lab-scale MBR by using different operating strategies for 878 days. The reactor was operated in continuous mode and with biomass highly enriched in these microbes. It was found that adjustments in the mineral medium concentration (reduction of Ca, P, and K) and composition (EDTA addition, increasing the Cu and Fe bioavailability), contributed to achieving remarkable and prolonged nitrite removal rates of up to 285.7 mg NO2–-N/L/d. N-damo bacteria dominated the culture, up to 57 %. To the best of our knowledge, the rates attained are the highest reported in an N-damo bacteria enrichment.

Intensified fish farming. Performance of electrochemical remediation of marine RAS waters

Aquaculture has been the fastest growing agricultural sector in the past few decades and currently supplies about half of the fish market. A range of environmental and management concerns including limited land and water availability have led to intensifying fish production by recirculating aquaculture systems (RAS). Fish's diet contains 30–60 % protein and about 4–10 % nitrogen (N). As fish assimilate only 20–30 % of the feed to produce body mass, the unassimilated N is released in the form of toxic ammonium that deteriorates water quality and compels its degradation. Widely extended biological nitrification is not efficient in the removal of nitrites nor other chemicals and pharmaceuticals used during fish culture. Electrochemical oxidation, a less developed alternative, reports several advantages such as, i) simultaneous degradation of ammonia‑nitrogen (TAN) and water disinfection in the same step with considerable simplification of the whole process, ii) easy adaptability to different production scales and periods of fish growth, and iii) no generation of harmful by-products and no use of chemicals, among others. Besides, in the case of marine aquaculture, the technology benefits from the high conductivity of seawater; thus, electrochemical oxidation is positioned in a very good place to satisfy the water treatment needs of the increasing production rate of marine aquaculture fish. Here, we report the analysis of the performance of a RAS demonstration plant aimed at farming gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) and provided with electrochemical remediation of culture water. The performance of the plant, with 20 m3 of seawater operating at a recirculation rate of 0.9–1.4 h−1, has been analysed in terms of TAN removal, water disinfection, make-up water intake and energy consumption and compared to data of conventional RAS provided with biofilters. The benefits and advantages of the innovative electrochemical remediation of RAS water are highlighted.

Enhanced Nitrite Electrovalorization to Ammonia by a NiFe Layered Double Hydroxide

AbstractThe development of non‐precious metal (NPM) electrocatalysts for efficient nitrite‐to‐ammonia upcycling is key to enabling a sustainable society. Here, an earth‐abundant NiFe layered double hydroxide (LDH) is prepared to electrochemically reduce nitrite with a Faradaic efficiency as high as 85 %, an ammonia selectivity reaching 98 %, and an ammonia yield rate up to 351 μmol h−1 mgcat−1, rivaling the performance metrics of state‐of‐the‐art NPM catalysts. NiFe LDH further displays excellent stability after 10 consecutive electrolysis runs with its nanostructure unperturbed. By conducting electroreduction of nitrite in a range of solutions, the electrolyte identity is found to play an important role in dictating the overall nitrite removal activity. Through a comparative study with MgFe and NiAl inorganic solids, Ni and Fe are demonstrated to boost nitrite valorization rate as well as ammonia selectivity and yield in a synergistic manner. Taken together, these low‐cost catalysts provide a promising strategy for one‐step conversion of nitrite into ammonia exclusively with implications in next‐generation wastewater treatment and green industrial commodity production.

The eco enzyme application to reduce nitrite in wastewater as the sustainability alternative solution in garbage and wastewater problems

The increasing population growth has an impact on increasing problems in wastewater quality and garbage volume. It is a need to develop a sustainability solution for both problems. In this research, the papaya fruit and spinach vegetable garbage were used as raw organic materials and fermented for six months. This study objective was to determine whether eco enzymes can be used to reduce nitrite concentration in wastewater. The research method was conducted on a laboratory scale with the artificial samples in a batch system. The result showed that eco enzyme made from a mixture of papaya and spinach can reduce the nitrite concentration in the water sample. The t-test showed that the effect of eco enzyme application in reducing nitrite in water samples was significant. The application of eco enzyme 0%, 2%, 4%, and 6% respectively during 10 hours exposure showed the nitrite removal were 0.3 %, 20%, 29%, and 35 %. It can be seen that the reduction of nitrite concentration in samples added by eco enzyme was caused by eco enzyme activity. The application at a higher concentration of 10%, 15%, and 20% showed that nitrite removal efficiencies were 35.7%, 36.7%, 46.7%, 49.4% respectively during 7 hours exposure. It can be concluded that a longer time exposure, and also the more eco enzyme concentration, showed the more result in the effect of nitrite reduction concentration in water. 4. By this study it is proven that application of eco enzyme made from organic garbage can be an alternative solution for garbage and wastewater quality problem.

Digital Evaluation of Nitrite-Reduced “Kulen” Fermented Sausage Quality

This study aimed to evaluate nitrite reduction impact on geometry, colour, chemical, microbiological, and sensory traits of dry sausage (kulen) traditionally prepared with red hot paprika powder. Three batches of kulen with different nitrite levels were produced and assessed: N110 (control with 110 mg/kg of sodium nitrite), N55 (55 mg/kg of sodium nitrite), and NF (without sodium nitrite). Samples for the analyses were taken on production day, after 8, 16, 24, 32, and 40 days of ripening and after 50 and 100 days of storage. Four novel digital methods for quality assessment were deployed such as computer vision system (CVS), three-dimensional (3D) laser imaging, oral processing, and temporal dominance of sensations (TDS). Reduction and removal of nitrites from the formulation of kulen did not result in significant ( P &lt; 0.01 ) differences in lightness ( L ∗ ), redness ( a ∗ ), and yellowness ( b ∗ ) of the sausage surface, meat, and fat parts that were measured independently by means CVS. Sausages produced by 50% nitrite reduction (N55) showed no significant ( P &lt; 0.01 ) differences in terms of geometrical, chemical, colour, microbiological, and oral processing parameters compared with the control (N110) batch. On the other hand, the complete removal of nitrites from kulen formulation negatively affected biogenic amine levels and oral processing properties of the product. Nitrite reduction showed no significant effect on TDS curves among the batches. The results of this study indicate that nitrite content in traditional kulen can be reduced by 50% (55 mg/kg of sodium nitrite) without adversely affecting the various quality properties of the product.

Characterization of Isolated Aerobic Denitrifying Bacteria and Their Potential Use in the Treatment of Nitrogen-Polluted Aquaculture Water

Ammonia and nitrite treatments are the critical steps that must be done to ensure the healthy growth of aquatic animals. The nitrification process is often used for nitrogen removal purposes due to its efficiency and environmentally friendly properties. However, the varied growth rate between ammonia and nitrite-oxidizing bacteria can cause nitrite accumulation, leading to the massive mortality of aquatic animals at high concentrations. Therefore, this study aimed to integrate the fast-growing heterotrophic nitrite-reducing bacteria with nitrifying bacteria to achieve a quicker nitrite removal activity. The two denitrifying Bacillussp. ST20 andBacillussp. ST26 were screened from shrimp ponds in Bac Lieu province, Vietnam. Obtained results showed that under anoxic conditions, the nitrite removal efficiency of these two strains reached 68.5-82% at nitrite initial concentration of 20mgN-NO2/L after 72h. Higher efficiency of over 95% was gained under oxic conditions. Hence, it enabled the use of denitrifying and nitrifying bacteria-co-immobilized carriers for ammonia oxidation and nitrite reduction simultaneously in a single-aerated bioreactor. A total of over 96% nitrogen content was removed during the bioreactor operation, despite the increase of inputting nitrogen concentration from 40 to 200mgN/L. Moreover, the suitable conditions for bacterial growth and nitrite conversion activity of the ST20 and ST26 were detected as 15‰ salinity and 35°C. The isolates also utilized various C-sources for growth, hence widening their applicability. The present study suggested that the isolated aerobic denitrifying bacteria are potentially used for the complete removal of nitrogen compounds from aquaculture wastewater.

Early activated quorum sensing enhanced a nosZ-deficient strain of Pseudomonas aeruginosa for stably recovering nitrous oxide from incineration leachate in microbial electrolysis cell

In this study, a quorum sensing (QS) signal molecule, 3-oxo-C12-HSL, was supplied into ΔnosZ Pseudomonas microbial electrolysis cell system for strengthening the N2O recovery from incineration leachate. The resistance for high nitrite loading was strongly improved with nitrite removal efficiency of 80.35% compared to 67.07% from the control on day 13 due to the increasing biomass through early activated QS. Higher N2O proportion in biogas (85.85% on average) was achieved in the QS early activated reactor, which indicated the better potential for N2O recovery. Bacterial community analysis showed the purity of ΔnosZ strain with the abundance of 100% in the anode chamber at the end of the operation. This was plausibly related to the increased synthesis of phenazine derivatives by the early activated QS system. These results show a more promising way for N2O recovery by a single engineering bacteria from the high nitrogen contained actual wastewater.