Enhancement of anammox performance in a novel non-woven fabric membrane bioreactor (nMBR)

© 2015 The Royal Society of Chemistry. To reduce operating costs and membrane fouling of conventional membrane bioreactors (cMBR), a novel MBR using a non-woven fabric membrane (nMBR) was constructed and the performance of the two MBRs was compared for anaerobic ammonium oxidation (anammox) cultivation. The results showed that the start-up period for the nMBR (44 days) was notably shorter than that for the cMBR (56 days), meanwhile the nMBR achieved a 2-times higher nitrogen removal rate (231.5 mg N per L per d) compared to the cMBR (112.3 mg N per L per d). Illumina MiSeq sequencing showed that Candidatus Kuenenia and Candidatus Jettenia were the main distinguished anammox bacteria. FISH analysis revealed that anammox bacteria predominated in both reactors, especially in the nMBR (58%) corresponding to a qPCR analysis of 1.07 × 109 copies per mL (day 120). N2O emission analysis confirmed the advantage of the nMBR in N2O reduction to reduce the influence of greenhouse gas emission while treating identical nitrogen. These results clearly demonstrated that nMBRs could be a prospective choice for anammox start-up and performance enhancement

Autotroofsed lämmastikuärastuse protsessid lämmastikuärastuseks kõrval- ja peavoolureoveest

Väitekirja elektrooniline versioon ei sisalda publikatsiooneTekkivate jäätmekoguste suurenemine ohustab tänapäeval keskkonna kvaliteeti ja inimeste tervist. Reovee bioloogiline puhastus on energiasäästlik viis orgaaniliste ja anorgaaniliste saasteainete eemaldamiseks reoveest ning jääkainete põhjavette sattumise tõenäosuse vähendamiseks. Mitmete biogaasijaamade rakendamine hõlmab orgaanilise süsiniku muundamist biogaasiks ning kõrgenenud sisaldusega lämmastiku- ja fosforiühendite esinemist heitvees. Selliste jäätmevoogude töötlemine on kulukas traditsiooniliste meetoditega (nitrifikatsioon-denitrifikatsioon), mis nõuab orgaanilise süsiniku lisamist tagasi töötlemisprotsessi (sageli metanooli kujul). Reoveepuhastuse tehnoloogiate hulgas on anaeroobset ammooniumi oksüdatsiooni protsessi (anammox) kaasatud autotroofse lämmastiku eemaldamisse piloot- ja täismahus tehnoloogiates lämmastiku eemaldamiseks reoveest vähese orgaanilise süsiniku kasutamisega. Peavoogu võib nimetada olmereoveeks ja kõrvalvoogu väduks, viimane tekib pärast liigmuda kääritamist ja tsentrifuugimist. Anammox protsessi on püütud kaasata nii kõrvalvoo kui ka peavoo puhastusse, kasutades liikuvate kandjatega biokilereaktorit (MBBR) ja annuspuhastuse reaktori (SBR) tehnoloogiaid. Võrreldes kõrvalvoo puhastamisega, on peamised takistused, mis tuleb ületada, et saavutada edukas anammox protsessi kasutamine peavoos: reovee kõrge süsiniku ja lämmastiku suhe (C/N>1) ja reovee madal temperatuur (põhjamaade kliimas 12,5–19 °C). Varasemad uuringud peavoo anammox protsessi kasutamise kohta on näidanud, et madalad temperatuurid võivad tekitada probleeme anammox biomassi kasvule. Et ületada madalate temperatuuride pärssivat mõju anam-mox bakterite kasvukiirusele, saab peavoo süsteemi nakatada kõrvalvoolu tingimustes kasvatatava biomassiga. Muutused redokspotentsiaalis (ORP-s) mõjutavad bakterite jaoks elutähtsate valkude koostist või mõjutavad bakterite mitokondriaalsete membraanide laengut. ORP muutusi saab juhtida aeratsiooni sisse/välja lülitamisega või aeraatoripõhiste intensiivsuse muutuste muutmisega, kasutades ORP-anduri signaali ja sobivate väärtuste vahemikke. Reovee soolsus ja hüdrasiini mõju on olulised parameetrid, mille abil hinnata anammox protsessi kulgu. Optimaalse soolsuse taseme saavutamine suurendab anammox protsessi aktiivsust ja lämmastiku eemaldamise kiirust. Anammox protsessi vaheühend – hüdrasiin, võib mõjutada anammox protsessi efektiivsust, kuid kahandada ka muid protsesse, näiteks denitrifikatsiooni, et saavutada kõrge lämmastiku eemaldamine autotroofselt.The increase in the amount of generated waste today threatens the quality of the environment and human health. Biological treatment of wastewater is an energy-efficient way to remove organic and inorganic pollutants from wastewater and to reduce the likelihood of residues entering the groundwater. The implementation of several biogas plants involves the conversion of organic carbon into biogas and the presence of elevated nitrogen and phosphorus compounds in the effluent. Treatment of such waste streams is costly with traditional methods (nitrification-denitrification), which require adding organic carbon back to the treatment process (often in the form of methanol). Among wastewater treatment technologies, the anaerobic ammonium oxidation process (anammox) has been incorporated into autotrophic nitrogen removal in pilot and full-scale technologies for nitrogen removal from waste with low organic carbon content. The mainstream can be called domestic sewage, and the side stream centrifuged anaerobic sludge reject water. The latter is formed after the fermentation and centrifugation of excess sludge. Attempts have been made to incorporate the anammox process into both sidestream and mainstream treatment using moving media biofilm reactor (MBBR) and batch scrubber (SBR) technologies. The main obstacles to be overcome in order to achieve a successful use of the anammox process in the mainstream are the high carbon to nitrogen ratio of the waste (C/N > 1) and the low temperature of the wastewater (12.5–19 °C present in the Nordic climate). Previous studies using the mainstream anammox process have shown that low temperatures can cause problems with anammox biomass growth. To overcome the inhibitory effect of cold temperatures on the growth rate of anammox bacteria, the mainstream system can be inoculated with biomass grown under side stream conditions. Changes in redox potential (ORP) affect the composition of proteins vital to bacteria or the charge of bacterial mitochondrial membranes. ORP changes can be controlled by turning aeration on/off or changing aerator-specific intensity changes using the ORP sensor signal and appropriate value ranges. The salinity of the wastewater and the effect of hydrazine are important parameters to evaluate the course of the anammox process. Achieving an optimal salinity level increases the activity of the anammox process and the rate of nitrogen removal. An intermediate in the anammox process, hydrazine, can affect the efficiency of the anammox process but also reduces other processes, such as denitrification, to achieve high nitrogen removal autotrophically.https://www.ester.ee/record=b552787

Nitrogen removal in anaerobic ammonium oxidation process-based bioelectrochemical system.

Nitrogen removal process was studied in a microbial electrosynthesis (BES) system at different applied voltages. Three different inoculation methods were compared and cyclic voltammograms were generated to evaluate changes on the bioelectrodes. Results from this study showed that after electrode inoculation gradually lowering the applied potential over a long period of time results in improvement of the nitrogen removal rates. Cyclic voltammetry sowed a strong correlation between the nitrogen removal efficiency of a biocathode and its specific capacitance. This study contributes to the idea that an electrical potential of -0.5 V could result in an increase of ~30% on the nitrogen removal rate of a bioelectrode using anammox process

Oxygen management for optimisation of nitrogen removal in a sequencing batch reactor

In today's progressively urbanised society, there is an increasing need for cost-effective, environmentally sound technologies for the removal of nutrients (carbon, phosphorous, nitrogen) from polluted water. Nitrogen removal from wastewater is the focus of this thesis. Conventional nitrogen removal requires the two processes of aerobic nitrification followed by anoxic denitrification, which is driven by remaining reducing power. While most wastewaters contain a significant fraction of reducing power in the form of organic substrate, it is difficult to preserve the reducing power required for denitrification, due to the necessary preceding aerobic oxidation step. Consequently, one of the major limitations to complete N-removal in traditional wastewater treatment systems is the shortage of organic carbon substrate for the reduction of oxidised nitrogen (NO^2-, NO^3-), produced from nitrification. This thesis followed two main research themes that aimed to address the problem of organic carbon limitation in nitrogen removal from wastewater, by management of the oxygen supply. The first theme was the study of N-removal by simultaneous nitrification and denitrification (SND) in the novel reactor type, the sequencing batch reactor (SBR). It was aimed to increase understanding of PHB metabolism and the limiting factors of SND and then to develop a suitable on-line control strategy to manage the oxygen supply and optimise nitrogen removal by SND. The second main research theme was the application of the CANON(Completely Autotrophic Nitrogen-removal Over Nitrite) process for nitrogen removal from wastewater; a novel process that requires minimal oxygen supply and has the potential to completely circumvent the requirement for organic substrate in nitrogen removal because it is catalysed by autotrophic microorganisms - Anammox (anaerobic ammonium oxidisers) and aerobic nitrifiers. For study of the SND process, a completely automated 2 L sequencing batch reactor was developed with on-line monitoring of the dissolved oxygen concentration, pH and oxidation-reduction (ORP) potential. The SBR was operated continuously for up to 2 years and, due to its separation of different phases by time, enabled the study and optimisation of different microbial activities, including acetate uptake and conversion to PHB (feast phase), PHB hydrolysis and consumption (famine phase), nitrification and denitrification (and SND). All experimental work was performed using a mixed culture and acetate as the organic substrate. Acetate consumption and PHB production was studied under different oxygen supply rates to establish conditions that allow maximum conversion of acetate to PHB during the feast phase. Lower DO supply rates (kLa 6 - 16 h^-1) resulted in preservation of a higher proportion of acetate as PHB than at higher DO supply rates (kLa 30 and 51 h^-1). Up to 77 % of the reducing equivalents available from acetate were converted to PHB under O2-limitation, as opposed to only 54 % under O2-excess conditions, where a higher fraction of acetate was used for biomass growth. A metabolic model based on biochemical stoichiometry was developed that could reproduce the trends of the effect of oxygen on PHB production. Experimental findings and simulated results highlighted the importance of oxygen control during the feast phase of an SBR in preserving reducing power as PHB. To develop an oxygen management strategy for the aerobic famine phase,the effect of the dissolved oxygen (DO) concentration on SND, using PHB as the electron donor, was investigated. There was a clear compromise between the rate and the percentage of SND achieved at different DO concentrations. A DO setpoint of 1 mg L^-1 was optimal for both the percentage of SND (61 %) and rate of SND (4.4 mmol N. Cmol X-1. h^-1). Electron flux analysis showed that most SND activity occurred during the first hour of the aerobic famine period, when the oxygen uptake rate (due to NH4 + and PHB oxidation) was highest. Aerated denitrification ceased as soon as NH4 + was depleted. The presence of NH4 + provided an oxygen 'shield', preventing excessive penetration of oxygen into the flocs and creating larger anoxic zones for SND. PHB degradation was first order with respect to the biomass PHB concentration (dfPHB/dt = 0.19 . fPHB). The slow nature of PHB degradation made it a suitable substrate for SND, as it was degraded at a similar rate to ammonium oxidation. While DO control during the aerobic famine phase could increase nitrogen removal via SND, total N-removal in the SBR was still limited by the availability of reducing power(PHB) in the anoxic phase. The length of the aerobic phase needed to be minimised to prevent over-oxidation of PHB after NH4 + depletion. The specific oxygen uptake rate (SOUR) was found to be an effective on-line parameter that could reproducibly detect the end-point of nitrification. A simple method was developed for continuous, on-line measurement of the SOUR, which was used for automated adjustment of the aerobic phase length. Minimisation of the aerobic phase length by feedback control of the SOUR improved nitrogen removal from 69 % (without phase length control) to 86 %, during one cycle. The SOUR-aeration control technique could successfully adapt the aerobic phase length to varying wastewater types and strengths and to varying aeration conditions. The medium- and long-term effects of oxygen management on nitrogen removal was investigated by operating the SBR continuously for up to one month using DO control throughout all stages of the SBR, i.e. oxygen-limitation during the feast phase, a DO setpoint of 1 mg L-1 during the famine phase and SOUR controlled aerobic phase length. Complete oxygen management resulted in minimisation of the amount of PHB that was oxidised aerobically in each SBR cycle and caused an accumulation of cellular PHB over time. The increased availability of PHB during aeration resulted in a higher SOUR and increased N-removal by SND from 34 to 54 %. After one month of continuous SBR operation, the settling efficiency of the biomass improved from 110 mL . g-1X to less than 70 mL . g-1X and almost complete N-removal (9 %) was achieved via SND during aeration, however at a reduced rate (1.5 mmol Cmol X^-1 h^-1). Therefore, long-term oxygen management resulted in biomass with improved settling characteristics and a higher capacity for SND. Results of the first main research theme highlighted the importance of aeration control throughout all stages of the SBR for maximum N-removal via SND. The CANON process was investigated as an alternative to the use of conventional activated sludge for treatment of wastewaters limited by organic carbon substrate. The initial study of the CANON process was performed at the Kluyver Laboratory in Delft, the Netherlands, using an already established Anammox enrichment culture. The effect of extended periods of NH4 +-limitation on the CANON microbial populations was studied, to examine their ability to recover from major disturbances in feed composition. The CANON process was stable for long periods of time until the N-loading rate reached below 0.1 kg N m 3 day-1, when a third population of bacteria developed in the system (aerobic nitrite oxidisers), resulting in a decrease in N-removal from 92 % to 57 %. Nitrite oxidisers developed due to increased levels of oxygen and nitrite. This highlighted the requirement for oxygen control during the CANON process to prevent increased DO levels and growth of undesired microbes. To initiate the CANON process from a local source, Anammox was enriched from local activated sludge (Perth, Western Australia). FISH analysis (fluorescence in situ hybridisation) of the enriched Anammox strain showed that it belonged to the Order Planctomycetales, the same as all other identified Anammox strains, but represented a new species of Anammox. The enrichment culture was not inhibited by repeated exposure to oxygen, allowing initiation of an intermittently-aerated CANON process to achieve sustained, completely autotrophic ammonium removal (0.08 kg N m-3 day-1) for an extended period of time, without any addition of organic carbon substrate. Dissolved oxygen control played a critical role in achieving alternating aerobic and anaerobic ammonium oxidation. The main conclusion drawn from the study is the important role of oxygen management in achieving improved nitrogen removal. A careful oxygen management strategy can minimise wastage of reducing power to improve PHB-driven SND by activated sludge and can prevent major disturbances to the population balance in the CANON system. Oxygen management has the potential to reduce aeration costs while significantly improving nitrogen removal from wastewaters limited by organic carbon

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Department of Urban and Environmental Engineering (Environmental Science and Engineering)Anaerobic digestion (AD) is considered a viable method for treating food waste (FW) because it biologically converts organic waste into biogas. However, FW has unique characteristics that complicate its stable AD over the long term, for example, seasonal variations in the production and composition of FW. Korean FW is characterized by a high content of vegetables and fruits (approximately 55%) that are rich in dietary fiber, which can cause difficulties in hydrolysis and, thus, degradation of FW. The amount of FW increases dramatically during the ???Kimjang??? season that mainly Napa cabbage accounts for approximately 20% of the total FW produced in Korea. This significant seasonal variation in the composition of FW recurs annually, and it could influence the performance and stability for the AD of FW. Nonetheless, few studies have systematically investigated the effect of this variation on the performance of AD and methods to enhance the stability of FW digesters suffering the issue of seasonal variations in FW. Bioaugmentation is a method for improving the degradation of organic pollutants through the addition of exogenous microorganisms that can degrade the target compounds in situ. Therefore, the selection of appropriate microorganisms that can thrive and retain the desired metabolic properties in a given environment is an important factor in bioaugmentation. Bioaugmentation has been suggested as a promising strategy for enhancing the performance of AD at the microbial community level. Rumen provides a favorable environment for the formation and development of a naturally formed anaerobic microbial community consisting of metabolically versatile microorganisms, and rumen microorganisms are a good source of hydrolytic bacteria capable of decomposing complex matters, including fibers. Additionally, rumen microorganisms contain acidogens and methanogens, and they produce methane as the final product of biodegradation, similar to AD microbial communities. These characteristics make it feasible to use rumen microorganisms as an exogenous microbial source for bioaugmentation of AD processes. In this doctoral research, the bioaugmentation potential of rumen culture for enhancing the biomethanation of Korean FW was examined, with emphases on increase in substrate digestibility and long-term stability of the bioaugmented process. In study 1, the potential of rumen fluid (RF) as a bioaugmentation source was first examined in batch tests. RF and two cellulolytic Clostridium species were tested in different combinations and various seeding ratios to determine the optimal bioaugmentation source and ratio by using simulated Korean FW. Then, a continuous experiment employing the optimal bioaugmentation condition determined in the batch test (10% RF to the inoculated anaerobic sludge on a volatile suspended solids (VSS) basis) was performed using the same substrate. The experimental results indicated that bioaugmentation with RF effectively enhanced the biomethanation of FW in both batch and continuous modes. The microbial community structures, especially bacterial community structures, shifted significantly after the introduction of RF. Therefore, it was found to be possible to alter the composition and function of microbial communities and, thus, to enhance the biomethanation of FW through bioaugmentation with RF. In study 2, for comparison, the aforementioned bioaugmentation strategy was applied to single- and two-phase processes for treating real Korean FW. In the two-phase process, the amount of RF to be added to the acidogenic reactor was determined based on the VSS concentration in the reactor (i.e., smaller amount of RF compared to that used in the single-phase process) to test the possibility of reducing the consumption of RF, which is a relatively scarce resource. Both processes were operated at varying organic loading rates (OLRs, 0.5???6.0 g volatile solids (VS)/L??d) without pH control. Both processes showed comparable methanogenic performances at OLRs ???4.0 g VS/L??d, and the acidogenic reactor maintained stable production of volatile fatty acids (mainly lactate) and ethanol, despite the highly acidic pH ???3.4. However, the single-phase process achieved stable AD performance with an increased OLR 5.0 g VS/L??d, whereas the two-phase process failed. These results can be ascribed to the provision of a more favorable environment for syntrophic interactions between acidogens and methanogens and the addition of more amount of RF in the single-phase process. Consequently, the single-phase configuration was selected for the subsequent long-term experiment because achieving stable and robust performance is important for AD plants. Study 3 focuses on the feasibility of bioaugmentation with rumen culture (RC) as a strategy to enhance the biomethanation of FW in batch and long-term continuous experiments. Batch tests were conducted for three inocula (i.e., anaerobic sludge with FW, RC-inoculated RF with FW, mixed culture of anaerobic sludge and RC with FW) with Napa cabbage (i.e., simulated kimjang waste (KW)) and cellulose. The results of the three subculture cycles indicated that the mixed-culture inoculum provided a higher biogas yield than the other inocula, indicating that bioaugmentation with RC has the potential for enhancing the biomethanation of fiber-rich FW. Then, bioaugmentation with RC was examined in the continuous experiment with fluctuations by adding KW into FW (0???20% of the total substrate VS). The results demonstrated that bioaugmentation with RC effectively increased the biomethanation of FW (by 12.3% increase in methane yield compared to the control without bioaugmentation), especially after the addition of KW. Changes to the microbial community structure corresponding to bioaugmentation and adaptation to fluctuations in substrate composition, such as the emergence of hydrolytic/acidogenic bacteria originating from the RC and the dominant shift to hydrogenotrophic methanogenesis, were observed. Importantly, the bioaugmented microbial populations seemingly remained active and helped sustain the enhanced AD performance in the long-term experiment (>38 months). Therefore, the proposed bioaugmentation strategy proved to be effective for improving the robustness and resilience of an FW digester in terms of handling seasonal fluctuations in FW composition and loading. In conclusion, this study verified that bioaugmentation with RC is a practical tool for enhancing the AD of Korean FW in terms of energy production and process stability. Moreover, long-term effectiveness of the bioaugmentation strategy was demonstrated in the continuous mode with varying fractions of KW (i.e., simulated seasonal variations). The findings of this study will be useful for managing AD plants that treat FW and significantly add to the literature on this topic.clos

Assessment of the nitritation and anammox processes for mainstream wastewater treatment

The implementation of autotrophic nitrogen removal processes such as the combined partial nitritation and anammox processes will contribute to maximise the wastewater energy recovery converting the wastewater treatment plants in net energy producers and enabling the wastewater reuse. Consequently, this thesis aims to assess the nitritation and anammox processes implementation at mainstream conditions characterised by its low temperature, low nitrogen concentration and high fluctuations of wastewater characteristics. Different reactor configurations, including one and two-stage systems, were employed. The treatment of different types of effluents, blackwater from a source-separation on-site system and municipal wastewater were studied, being specially focused on overcoming the nitrite oxidizing bacteria development that challenged the anammox based processes implementations. Special attention was paid to the production of effluents complying with the European discharge limits as well as the evaluation of the activities of the involved microbial populations

Performance of Anoxic-Oxic Sequencing Batch Reactor for Nitrification and Aerobic Denitrification

The biological nitrogen removal (BNR) involves two processes: nitrification and denitrification. Denitrification occurs almost exclusively under facultative anaerobic or microaerophilic conditions; however, aerobic denitrification can occur in aerated reactors. In this chapter, the feasibility of achieving nitrogen removal using a lab-scale biological sequencing batch reactor (SBR) exposed to anoxic/oxic (AN/OX) phases is described in order to attain aerobic denitrification. The SBR was fed with acetate and ammonium sulfate. Nitrite generation was controlled in order to avoid the N2O production by nitrifier denitrification. Experiments under four different operating conditions were carried out: low and high aeration, each one with low and high organic loads. For all the tested conditions, a complete COD removal was achieved. The highest inorganic N removal close to 80% was obtained at pH = 7.5, high organic load (880 mg COD/(L day)) and high aeration given by 12 h cycle, AN/OX ratio = 0.5:1.0, and dissolved oxygen concentration higher than 4.0 mg O2/L. Nitrification followed by high-rate aerobic denitrification took place during the aerobic phase. Denitrification took place mainly from the intracellular reserves of polyhydroxyalkanoates (PHA) during the aerobic phase. The proposed AN/OX system constitutes a simple and potentially eco-friendly process for biological nitrogen removal, providing N2 as the end product and decreasing the formation of N2O, a powerful greenhouse gas

Coupled iron reduction-ammonium oxidation (Feammox) in alkaline soils polluted with nitrogen

Although nitrogen fertilizers help stimulate plant and microbial growth in N-limited soils, the use of excess N fertilizers to improve agricultural yield in Canada can cause adverse side effects of groundwater and surface water pollution, greenhouse gas production, soil acidification, and human health issues. Two N-removal pathways currently used to treat N-polluted wastewater and groundwater include denitrification and anaerobic ammonium oxidation (anammox). This study explored a novel anaerobic N-removal pathway that converts ammonium (NH4+) to inert nitrogen gas (N2) or nitrite (NO2-) while reducing Fe(III) to Fe(II), a.k.a. iron ammonium oxidation (Feammox) via a 118-day anaerobic incubation which included four sequential biostimulation experiments. The goal of the incubation was to identify Feammox in neutral-alkaline soil samples from a N-polluted site in Alberta by stimulating the bioremediation of NH4+. This was done amending the soils with vitamins and sources of NH4+ and Fe(III). The treatments for the anaerobic controls and soil slurries included one or more of the following: ammonium chloride (A), 2-line ferrihydrite (FH), and ferric citrate (FC). Amendments were added to these treatments in four sequential Feammox biostimulation experiments: 1) FC, FH, and A, 2) FC and FH, 3) FC and A, and 4) vitamin and molybdate solutions. The soil slurry with ferric citrate and NH4Cl amendments (S-FCA) had the most notable dissolved NH4+-N loss during the 118-day incubation, particularly when FC and A were added concurrently, i.e. a decrease of 14 ± 1.7 mg L-1 dissolved NH4+-N in the first experiment and a decrease of 13 ± 6.5 mg L-1 dissolved NH4+-N in the third experiment. S-FCA also exhibited signs of Fe(III) reduction throughout the incubation. In the incubation all samples generated minimal dissolved NO2- (0-2 mg L-1). Following the 118-day incubation the S-FCA treatment was subcultured to reproduce results; however, the subcultures did not show notable NH4+ loss, possibly due to dilution or N mineralization. Overall, this study showed a correlation between concurrent ferric citrate and NH4Cl amendments and dissolved NH4+-N loss in near-neutral anaerobic conditions; however, it did not provide clear evidence of Feammox. Additional experiments are necessary to isolate Feammox