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Schematic diagram of the sequencing batch reactor (SBR): (1) Operation interface, (2) Stirrer, (3) Thermostatic reflecting plate, (4) pH probe, (5) Temperature probe, (6) Dissolved oxygen (DO)
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This work aimed to enrich a denitrifying bacterial community for economical denitrification via nitrite to provide the basic objects for enhancing nitrogen removal from wastewater. A sequencing batch reactor (SBR) with continuous nitrite and acetate feeding was operated by reasonably adjusting the supply rate based on the reaction rate, and at a te...
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Context 1
... sequencing batch reactor (SBR) (BLBIO-5GJ, BLBIO Corp., Shanghai, China) with a working volume of 4 L was operated to enrich the denitrifying bacteria using nitrite as an electron acceptor, as shown in Figure 1. The continuous substrate feed stream (NaNO2, nitrogen source; CH3COONa, organic carbon source; mixed together) and the hydrochloric acid (HCl) feed stream (1 mol/L-5 mol/L of raw feed; pH buffer; the concentration increasing with the denitrification rate) were supplied via two individual high-concentration stock solutions contained in each feed bottle, which were connected to two peristaltic pumps to control the flow rates. ...
Context 2
... the nitrite feed stream added into the reaction liquid was adjusted according to the nitrite denitrification rate of the previous cycle. The reactor was filled with foam due to the high performance of nitrogen removal from synthetic wastewater at the end of Cycle 24 on Day 12 (as shown in Figure S1), leading to the NO2 − -N remaining from the uncompleted reaction, and the calculated amount of NO2 − -N consumption was as high as 3304.25 mg/L in this cycle (12 h). Due to the limited volume of the reactor, the foam inside the reactor had a negative influence on the denitrification process carried out by the activated sludge. ...
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... In addition, the nitrifying organisms grow in flocs of the activated sludge, and without this bioaugmentation, the nitrifiers will tend to grow suspended in the medium; when bioaugmentation is combined with the deammonification process, the negative effects of the nitrogen load of WWTPs are reduced as well as the loss of biomass, so it can be considered that the deammonification process is efficient for the removal of nitrogen and cultivation of nitrifiers for bioaugmentation (Berends et al. 2005;Muszyński-Huhajło et al. 2021;Nsengiyuma et al. 2021;Van Loosdrecht and Salem 2006). A high concentration of nitrite can inhibit denitrifying microorganisms; however, by using the bioaugmentation process in an sequencing batch reactor (SBR) with continuous feeding of nitrite and acetate, the denitrifying bacterial community was enriched, and the nitrite denitrification rate increased from 10 to 275 mg/L h, showing an increase in the microbial biodiversity involved in the denitrification process from 2.16% to 84.26% during the enrichment period (Yao et al. 2019). An SBR operated at 3 different temperatures (20, 15, and 10 °C) was bioaugmented with archaea resulting in up to 20% removal of total nitrogen contained in municipal wastewater compared to other SBR that was not bioaugmented (Szaja and Szulżyk-Cieplak 2020). ...
Water is a universal solvent and liquid required in most anthropogenic, natural, and biochemical processes. Once used, water will have chemical or microbiological pollutants (wastewater), and knowing that the amount of water on the planet will always be the same, a treatment process must be chosen that aims to eliminate the greatest amount of pollutants to be able to return it to the receiving bodies of water or to be able to reuse it, reducing the impact on the environment. These wastewater treatment processes can be grouped into chemical, physical, and biological. In the case of biological treatment, it consists of using enzymes, microorganisms, or plants to accumulate, transform, or degrade contaminants through their metabolism. Biological treatment systems can be divided into conventional and advanced. Conventional ones are activated sludge, rotating biological contactors, biofilters, nitrification, and denitrification, among others. As an example of advanced biological treatment systems, we can name all the processes that mineralize nitrogenous compounds to molecular nitrogen (such as ANAMMOX, CANON, OLAND), the bioaugmentation batch-enhanced process (BABE), the use of aerobic granular sludge (AGS), and constructed wetlands (CW), among others. Advanced biological treatment systems can offer some of the following advantages compared to conventional biological systems: decreased hydraulic retention times, fewer space requirements, mineralized contaminants, a better landscape, and nominal investment costs in equipment and infrastructure. The present chapter will focus on discussing the most recent advances in biological wastewater treatment and how these systems can be applied to deal with existing and emerging pollutants in wastewater.
... Based on our own research, it can be concluded that the addition of GSS will increase DHA, CAT and URE. It may indicate an increase in microbial biomass and the rate of denitrification as a result of using GSS, which was also observed in the studies by Yao et al. [33]. In addition, an increase in the enzyme activity under the influence of GSS may be due to the fact that organic matter was additionally introduced into soil along with the sludge with a pool of macro-and microelements, which could additionally stimulate the growth of soil microorganisms. ...
One of the solutions implemented in order to improve the quality of soils exposed to pesticides is the application of sewage sludge, which is a by-product of wastewater treatment. As an organic substrate, it provides soil with important nutrients, such as nitrogen and phosphorus, and enriches it with organic matter, thanks to which it can be a valuable fertilizer. The aim of the presented research was to evaluate the influence of granulated sewage sludge (GSS) on the biological properties of soil treated with herbicides (MCPA and dicamba) and fungicides (thiophanate-methyl and azoxystrobin). The following aspects were investigated: the activity of selected soil enzymes, the genetic biodiversity of bacteria and fungi, and the abundance of the bacterial gene responsible for ammonia oxidation. A field experiment was conducted, in which granulated sewage sludge (GSS) was applied to soil at a single dose of 3 t/ha. Wheat (Triticum aestivum L.) was sown on the prepared plots. The herbicides (H) and fungicides (F) as well as their mixture (F + H) were applied to the plants in the appropriate growth phases in the doses recommended by the producer. The control was soil without sewage sludge (C). The samples taken were tested for: dehydrogenases, catalases and urease activities, genetic biodiversity structure of bacteria and fungi by TRFLP assay, and the abundance of the bacterial amoA gene by qPCR. On the basis of the obtained results, it was found that the application of pesticides to soil fertilized with sewage sludge influenced the enzymatic activity of soil, and their activity differed depending on the tested enzyme. The activity of URE and DHA on the plots with GSS was higher by approx. 20% and 30%, respectively, as compared to the plots without GSS application. Moreover, both the genetic biodiversity of microorganisms and the abundance of amoA gene differed depending on the variant of the experiment. The GSS treatment of soil significantly influenced the growth of the studied gene as compared to C, and its abundance was 9.15 log10 gene copies/g DW of soil. Due to the content of nutrients in sewage sludge, it can be a valuable fertilizer in agricultural crops treated with pesticides.
... On the other hand, Flavobacterium (27.1%) and Brevifollis (14%) became more abundant in the BER-20. Flavabacterium was capable of using a nitrogenous compound for anaerobic respiration, with a high NO 2 -N denitrification rate of 275.35 mg/L-h and a high specific removal rate of 51.80 mg/g-h [30]. In addition, Flavabacterium was able to grow in an aeration condition (DO > 5 mg/L) [31]. ...
... On the other hand, Flavobacterium (27.1%) and Brevifollis (14%) became more abundant in the BER-20. Flavabacterium was capable of using a nitrogenous compound for anaerobic respiration, with a high NO2-N denitrification rate of 275.35 mg/L-h and a high specific removal rate of 51.80 mg/g-h [30]. In addition, Flavabacterium was able to grow in an aeration condition (DO > 5 mg/L) [31]. ...
Nitrate-nitrogen (NO3-N) contaminating groundwater is an environmental issue in many areas, and is difficult to treat by simple processes. A bio-electrochemical reactor (BER) using copper wire and graphite plate was developed to purify the NO3-N-contaminated groundwater. The low (of 10 mA) and high (of 20 mA) electric currents were applied to the BERs, and various influent hardness levels from 20 to 80 mg/L as CaCO3 due to groundwater characteristics were supplied to clarify the total nitrogen removal efficiency and NO3-N removal mechanisms. In the BER-10, the bio-electrochemical reactions caused 85% of total nitrogen to be removed through heterotrophic and autohydrogenotrophic denitrification in the suspended sludge and biofilm. However, the chemical deposit occurring at the cathode from water hardness affected the decreasing denitrification performance; 12.6% of Mg and 8.8% of Ca elements were observed in the biofilm. The enhancement of electrochemical reactions in the BER-20 caused integrating electrochemical and bio-electrochemical reactions; the NO3-N was electrochemically reduced to NO2-N, and it was further biologically reduced to N2. A better total nitrogen removal of 95% was found; although, a larger deposit of Mg (22.8%) and Ca (10.8%) was observed. The relatively low dissolved H2 in the BER-20 confirmed that the deposit affected the decreasing gaseous H2 transfer and inhibition of autohydrogenotrophic denitrification in the suspended sludge. According to the microbial analysis, both heterotrophic and autohydrogenotrophic denitrification were obtained in the suspended sludge of both BERs; Nocadia (26.8%) was the most abundant genus in the BER-10, whereas Flavobacterium (27.1%) and Nocadia (25.0%) were the dominant genera in the BER-20.
... Currently, the low removal efficiency of NO 3 − -N is one of the main reasons for excessive TN in WWTPs. Rivers and other surface water bodies are the most important receiving water bodies for WWTPs; excessive nitrogen discharged into rivers leads to water eutrophication and the black-odorous water phenomenon, and destroys the balance of natural water ecosystems [2][3][4]. Moreover, NO 3 − -N increases the risk of gastric cancer, causes blue baby syndrome [5] and seriously threatens human health [6][7][8]. ...
Nitrogen pollution of surface water is the main cause of water eutrophication, and is considered a worldwide challenge in surface water treatment. Currently, the total nitrogen (TN) content in the effluent of wastewater treatment plants (WWTPs) is still high at low winter temperatures, mainly as a result of the incomplete removal of nitrate (NO3−-N). In this research, a novel aerobic denitrifier identified as Pseudomonas sp. 41 was isolated from municipal activated sludge; this strain could rapidly degrade a high concentration of NO3−-N at low temperature. Strain 41 completely converted 100 mg/L NO3−-N in 48 h at 15 °C, and the maximum removal rate reached 4.0 mg/L/h. The functional genes napA, nirS, norB and nosZ were successfully amplified, which provided a theoretical support for the aerobic denitrification capacity of strain 41. In particular, the results of denitrification experiments showed that strain 41 could perform aerobic denitrification under the catalysis of NAP. Nitrogen balance analysis revealed that strain 41 degraded NO3−-N mainly through assimilation (52.35%) and aerobic denitrification (44.02%), and combined with the gene amplification results, the nitrate metabolism pathway of strain 41 was proposed. Single-factor experiments confirmed that strain 41 possessed the best nitrogen removal performance under the conditions of sodium citrate as carbon source, C/N ratio 10, pH 8, temperature 15–30 °C and rotation speed 120 rpm. Meanwhile, the bioaugmentation test manifested that the immobilized strain 41 remarkably improved the denitrification efficiency and shortened the reaction time in the treatment of synthetic wastewater.
... Species of Flavobacterium are generally aerobic heterotrophs, many of which are psychrotolerant [62], but the genus also harbors aerobic and facultative anaerobic denitrifiers, thus demonstrating metabolic versatility [63][64][65]. The genus was also found in relatively high abundance in previous studies of denitrifiers from wastewater treatment facilities [66] and bioreactors [19,47]. The absence of Flavobacterium in our denitrifying enrichment cultures indicated the limitations of the enrichment approach, which was performed under anoxic conditions but apparently introduced selective pressures hampering competitive proliferation of Flavobacterium. ...
Denitrifying woodchip bioreactors (WBR), which aim to reduce nitrate (NO3−) pollution from agricultural drainage water, are less efficient when cold temperatures slow down the microbial transformation processes. Conducting bioaugmentation could potentially increase the NO3− removal efficiency during these specific periods. First, it is necessary to investigate denitrifying microbial populations in these facilities and understand their temperature responses. We hypothesized that seasonal changes and subsequent adaptations of microbial populations would allow for enrichment of cold-adapted denitrifying bacterial populations with potential use for bioaugmentation. Woodchip material was sampled from an operating WBR during spring, fall, and winter and used for enrichments of denitrifiers that were characterized by studies of metagenomics and temperature dependence of NO3− depletion. The successful enrichment of psychrotolerant denitrifiers was supported by the differences in temperature response, with the apparent domination of the phylum Proteobacteria and the genus Pseudomonas. The enrichments were found to have different microbiomes’ composition and they mainly differed with native woodchip microbiomes by a lower abundance of the genus Flavobacterium. Overall, the performance and composition of the enriched denitrifying population from the WBR microbiome indicated a potential for efficient NO3− removal at cold temperatures that could be stimulated by the addition of selected cold-adapted denitrifying bacteria.
... They may differ under the long-term investigation with different operational modes. The previous studies reported that biodegradability of carbon sources, temperature, pH, C/N ratio, nitrite concentration and DO concentration were the main factors influencing denitrifying bacteria growth [69,70]. Adjusting the nutrient supply rate and the above-influenced parameters may control over the microbial enrichment reasonably for NO reduction that may be a common property of denitrifying bacteria [63] which accounted as 97% in this analysis. ...
Nitrogen oxide (NOx) emissions cause significant impacts on the environment and must therefore be controlled even more stringently. This requires the development of cost-effective removal strategies which simultaneously create value added by-products or energy from the waste.
This study aims to treat gaseous nitric oxide (NO) by hollow-fiber membrane biofilm reactor (HFMBfR) in the presence of nitrite (NO2⁻) and evaluate nitrous oxide (N2O) emissions formed as an intermediate product during the denitrification process. Accumulated N2O can be utilized in methane oxidation as an oxidant to produce energy. In the first stage of the study, the HFMBfR was operated by feeding only gaseous NO as the nitrogen source. During this period, the best performance was achieved with 92% NO removal efficiency. In the second stage, both NO gas and NO2⁻ supplied to the system, and 91% NO and 99% NO2⁻ reduction were achieved simultaneously with the maximum N2O generation of 386 ± 31 ppm. Lower influent carbon to nitrogen (C/N) ratios, such as 4.5 and 2.0, and higher NO2⁻-N loading rate of 158 mg N day⁻¹ favored N2O generation. An improved NO removal rate and N2O accumulation were seen with the increasing amount of PO₄³⁻ in the medium. The 16S rDNA sequencing analysis revealed that Alicycliphilus denitrificans and Pseudomonas putida were the dominant species. The study shows that an HFMBfR can be successfully used to eliminate both NO2⁻ and gaseous NO and simultaneously generate N2O by adjusting the system parameters such as C/N ratio, NO2⁻ and PO₄³⁻ loading.
... During sewage treatment, the sewage flows continuously along an open curve under the action of gravity, and the curve is divided into multiple sections. The water quality parameters change continuously along the direction of the water flow but do not change with time, thus providing a stable environment for the growth of microorganisms [16,17]. After the operation stabilizes, theoretically, succession occurs in the microbial community structure of different biofilms, and the metabolic function interval is eliminated. ...
Based on the concept of microbial community multi-processing in integrated spatial bacterial succession (ISBS), this study constructs a highly efficient cellular fixed-bed bioreactor that follows the growth of biological flora in the wastewater treatment process. The reactor is organically partitioned based on synergistic laws and in accordance with environmental and microbial metabolic changes, and sewage is subjected to unitized and specialized biological treatment under direct current conditions. The results show that the ISBS reactor exhibits stable nitrogen removal performance under a low-carbon source. Compared with traditional sewage biochemical treatment technology, the microbial concentration is increased by 2–3 times and even up to 12 times, and the ammonia nitrogen removal rate is maintained at 99%. The removal rate reaches 90% (hydraulic retention time of 14 h). High-throughput sequencing analysis based on 16S rDNA reveals the microbial community structure succession at different depths of the same section of the reactor. The microbial community is rich under the influence of environmental factors and exhibits different responses. The intervals vary. An analysis of the microbial community function explains why the ISBS reactor has high nitrogen removal efficiency.
Globally, to ensure food security bio-based fertilizers must replace a percentage of chemical fertilizers. Such replacement must be deemed sustainable from agronomic and greenhouse gas (GHG) emission perspectives. For agronomic performance several controlled protocols are in place but not for testing GHG emissions. Herein, a pre-screening tool is presented to examine GHG emissions from bio-waste as fertilizers. The various treatments examined are as follows: soil with added mineral nitrogen (N, 140 kg N ha-1) fertilizer (MF), the same amount of MF combined with dairy processing sludge (DS), sludge-derived biochar produced at 450 °C (BC450) and 700 °C (BC700) and untreated control (CK). These treatments were combined with Danish (sandy loam) or Irish (clay loam) soils, with carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions and soil inorganic-N contents measured on selected days. During the incubation, biochar mitigated N2O emissions by regulating denitrification. BC450 reduced N2O emissions from Danish soil by 95.5% and BC700 by 97.7% compared to emissions with the sludge application, and for Irish soil, the N2O reductions were 93.6% and 32.3%, respectively. For both soils, biochar reduced CO2 emissions by 50% as compared to the sludge. The lower N2O reduction potential of BC700 for Irish soil could be due to the high soil organic carbon and clay content and pyrolysis temperature. For the same reasons emissions of N2O and CO2 from Irish soil were significantly higher than from Danish soil. The temporal variation in N2O emissions was correlated with soil inorganic-N contents. The CH4 emissions across treatments were not significantly different. This study developed a simple and cost-effective pre-screening method to evaluate the GHG emission potential of new bio-waste before its field application and guide the development of national emission inventories, towards achieving the goals of circular economy and the European Green Deal.
Ubrzani napredak industrije, poljoprivrede i domaćinstva su pogodovali povišenim koncentracijama dušika u vodenom ekosustavu, što uzrokuje eutrofikaciju. Dušik se iz otpadne vode uklanja procesom biološke denitrifikacije. U ovom preglednom radu dan je osvrt na denitrifikaciju, s aspekta mikroorganizama, koncentracije otopljenog kisika, donora i akceptora elektrona.
Even thoughdigestate, which is continually generated in anaerobic digestion process, can only be used as fertilizer during the growing season, digestate treatment is still a critical, environmental problem. That is why the present work aims to develop a method to manage digestate in agricultural biogas plant in periods when its use as fertilizer is not possible. A lab-scale system for the biological treatment of the digestate liquid fraction using the activated sludge method with a separate denitrification chamber was constructed and tested. The nitrogen load that was added tothe digestate liquid fraction accounted for 78.53% of the total nitrogen load fed into the reactor. External carbon sources, such as acetic acid, as well as flume water and molasses, i.e., wastewater and by-products from a sugar factory, were used to support the denitrification process. The best results were obtained using an acetic acid and COD (Chemical Oxygen Demand)/NO3–N (Nitrate Nitrogen) ratio of 7.5. The removal efficiency of TN (Total Nitrogen), NH4–N (Ammonia Nitrogen) and COD was 83.73%, 99.94%, 86.26%, respectively. It was interesting to see results obtained that were similar to those obtained when using flume water and COD/NO3–N at a ratio of 8.7. This indicates that flume water can be used as an alternative carbon source to intensify biological nitrogen removal from digestate.
