RESUMO
Submerged zone in bioretention facilities for stormwater treatment has been approved to be an effective structure amendment to improve denitrification capability. However, the role and influence of water quality changes in the submerged zone under natural continuous random rainfall patterns are still not clear, especially when the rainfall is less than the pore water in the submerged zone. In this study, continuous rainfall events with different rainfall volume (light rain-light rain-heavy rain) were designed in a lab-scale woodchip mulched pyrite bioretention facility to test the effects of rainfall pattern. The results exhibited that light rain events significantly affected the pollutant removal performance of bioretention for the next rainfall. Different effects were observed during the long-term operation. In the 5th month, light rain reduced the ammonia removal efficiency of subsequent rainstorm events by 8.70%, while in the 12th month, when nitrate leakage occurred, light rain led to a 40.24% reduction in the next heavy rain event's nitrate removal efficiency. Additionally, light rain would also affect the concentration of by-products in the next rainfall. Following a light rain, the concentration of sulfate in the subsequent light rainfall can increase by 24.4 mg/L, and by 11.92 mg/L in a heavy rain. The water quality in the submerged zone and media characteristics analysis suggested that nitrogen conversion capacity of the substrate and microbes, such as Nitrospira (2.86%) and Thiobacillus (35.71%), as well as the in-situ accumulation of pollutants under light rain played important roles. This study clarifies the relationship between successive rainfall events and provides a more comprehensive understanding of bioretention facilities. This is beneficial for field study of bioretention facilities in the face of complex rainfall events.
Assuntos
Chuva , Nitratos/análise , Desnitrificação , Nitrogênio/análise , Amônia/análise , Poluentes Químicos da Água/análise , Qualidade da ÁguaRESUMO
The stormwater biofilter is a prevailing green infrastructure for urban stormwater management, but it is less effective in dissolved nitrogen removal, especially for nitrate. The mechanism that governs the nitrate leaching and performance stability of stormwater biofilters is poorly understood. In this study, a water quality model was developed to predict the ammonium and nitrate dynamics in a biochar-pyrite amended stormwater biofilter. The transport of dissolved nitrogen species was described by advection-dispersion models. The kinetics of adsorption and pyrite-based autotrophic denitrification are included in the model and simulated with a steady-state saturated flow. The model was calibrated and validated using eleven storm events. The modeling results reveal that the contribution of pyrite-based autotrophic denitrification to nitrate leaching alleviation improves with the increased drying duration. The nitrate removal efficiency was affected by a series of design parameters. Pyrite filling rate has a minor effect on nitrate removal promotion. Service area ratio and submerged zone depth are the key parameters to prevent nitrate leaching, as they influence the emergence and discharge time of nitrate breakthrough. The high inflow volume (high service area ratio) and small submerged zone can lead to earlier and increased discharge of peak nitrate otherwise the peak nitrate could be retained in the submerged zone and denitrified during the drying period. The developed mechanistic model provides a useful tool to evaluate the treatment ability of stormwater biofilters under varying conditions and offers a guideline for biofilter design optimization.
Assuntos
Nitratos , Nitrogênio , Ferro , DesnitrificaçãoRESUMO
Aspartame (APM) is one of the most widely used artificial sweeteners worldwide. Studies have revealed that consuming APM may negatively affect the body, causing oxidative stress damage to multiple organs and leading to various neurophysiological symptoms. However, it's still unclear if consuming APM and one's daily biological rhythm have an interactive effect on health. In this study, healthy adult C57BL/6 mice were randomly divided into four groups: Control group (CON), oral gavage sham group (OGS), daytime APM intragastric group (DAI) and nighttime APM intragastric group (NAI). DAI and NAI groups were given 80â¯mg/kg body weight daily for 4 weeks. We found that DAI and NAI groups had significantly increased mean body weight, higher serum corticosterone levels, up-regulated pro-inflammatory responses in serum and brain, and exacerbated depressive-like behaviors than the CON and the two APM intake groups. Moreover, all these changes induced by APM intake were more significant in the DAI group than in the NAI group. The present study, for the first time, revealed that the intake of APM and daily biological rhythm have an interactive effect on health. This suggests that more attention should be paid to the timing of APM intake in human beings, and this study also provides an intriguing clue to the circadian rhythms of experimental animals that researchers should consider more when conducting animal experiments.
Assuntos
Aspartame , Peso Corporal , Corticosterona , Citocinas , Depressão , Camundongos Endogâmicos C57BL , Edulcorantes , Animais , Corticosterona/sangue , Aspartame/toxicidade , Depressão/induzido quimicamente , Depressão/sangue , Masculino , Camundongos , Peso Corporal/efeitos dos fármacos , Citocinas/sangue , Citocinas/metabolismo , Edulcorantes/administração & dosagem , Edulcorantes/toxicidade , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Ritmo Circadiano/efeitos dos fármacos , Ritmo Circadiano/fisiologia , Comportamento Animal/efeitos dos fármacosRESUMO
Persistent concerns regarding environmental hazards arise from the difficulty in disposing of radioactive plant-based wastes originating from the nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FNPP) in Japan in 2011. In this study, three anaerobic digestion (AD) strategies were proposed: Sole anaerobic wet fermentation, and wet fermentations with either alkaline-heat or ultrasonic pre-treatment, which were employed for long-term anaerobic treatment of a genuine radioactive grass stemming from the FNPP accident. The objectives of this work are to investigate the effects of pre-treatments on biomass conversion efficiency and to gain insight into the leaching behavior of radiocaesium (Rad-Cs) within AD processes. Experimental results indicate that by introducing alkaline-heat and ultrasonic pre-treatments to AD systems, the removal efficiencies of total solids (TS) from the raw grass increased by 60.8 % and 42.5 %, respectively, compared to sole wet fermentation. Pre-treatments have been shown to enhance the stability of AD systems, both in terms of enhancing methane production and mitigating pH fluctuations triggered by the accumulation of organic acids. Remarkably, even though the Rad-Cs leaching rate was highest when the AD system was fed with the alkaline-heat pre-treated grass, it remained unsatisfactory at only 5.77 %. We inadvertently isolated a soil-like component from the raw grass, and analyzed both its proportion in the raw grass and the radioactivity intensity. The results indicate that although the soil constituted only 9.51 % TS of the raw grass, it accounted for a significant 81.35 % of the total radioactivity. The soil, which has a pronounced affinity for ionic Cs, being mixed into the raw grass, was identified as the primary factor limiting the leaching efficiency of Rad-Cs throughout both the pre-treatment and wet fermentation phases.
Assuntos
Acidente Nuclear de Fukushima , Monitoramento de Radiação , Radioatividade , Poaceae , Fermentação , Anaerobiose , Biomassa , Radioisótopos de Césio/análise , Japão , SoloRESUMO
Bioretention systems are one of the most widely used stormwater control measures for urban runoff treatment. However, stable and effective dissolved nutrient treatment by bioretention systems is often challenged by complicated stormwater conditions. In this study, pyrite-only (PO), pyrite-biochar (PB), pyrite-woodchip (PW), and pyrite-woodchip-biochar mixed (M) bioretention systems were established to study the feasibility of improving both stability and efficiency in bioretention system via multi-media interaction. PB, PW, and M all showed enhanced dissolved nitrogen and/or phosphorus removal compared to PO, with M demonstrating the highest efficiency and stability under different antecedent drying durations (ADD), pollutant levels, and prolonged precipitation depth. The total dissolved nitrogen and dissolved phosphorus removal in M ranged between 64%-86% and 80%-95%, respectively, with limited organic matter and iron leaching. Pore water, microbial community, and material analysis collectively indicate that pyrite, woodchip, and biochar synergistically facilitated multiple nutrient treatment processes and protected each other against by-product leaching. Pyrite-woodchip interaction greatly increased nitrate removal by facilitating mixotrophic denitrification, while biochar further enhanced ammonium adsorption and expanded the denitrification area. The Fe3+ generated by pyrite aerobic oxidation was adsorbed on the biochar surface and potentially formed a Fe-biochar composite layer, which not only reduced Fe3+-induced pyrite excessive oxidation but also potentially increased organic matter adsorption. Fe (oxyhydr)oxides intermediate product formed by pyrite oxidation, in return, controlled the phosphorus and organic matter leaching from biochar and woodchip. Overall, this study demonstrates that multi-media interaction may enable bioretention systems to achieve stable and effective urban runoff treatment.
Assuntos
Carvão Vegetal , Ferro , Nitrogênio , Sulfetos , Nitrogênio/análise , Fósforo/análise , ChuvaRESUMO
Anaerobic ammonium oxidation (anammox) granular sludge is a promising biotechnological process for treating low-carbon nitrogenous wastewater, and is featured with low energy consumption and footprint. Previous theoretical and experimental research on anammox granular sludge processes mainly focused on granulation (flocs â granules), but pay little attention to the granulation cycle including granulation and regeneration. This work reviewed the previous studies from the perspective of anammox granules lifecycle and proposed various sustainable formation mechanisms of anammox granules. By reviewing the anaerobic, aerobic, and anammox granulation mechanisms, we summarize the mechanisms of thermodynamic theory, heterogeneous growth, extracellular polymeric substance (EPS)-based adhesion, quorum sensing (QS)-based regulation, biomineralization-based growth, and stratification of microorganisms to understand anammox granulation. In the regeneration process, the formation of precursors for re-granulation is explained by the mechanisms of physical crushing, quorum quenching and dispersion cue sensing. Based on the granulation cycle mechanism, the rebuilding of the normal regeneration process is considered essential to avoid granule floatation and the wash-out of granules. This comprehensive review indicates that future research on anammox granulation cycle should focus on the effects of filamentous bacteria in denitrification-anammox granulation cycle, the role of QS/ quorum quenching (QQ)-based autoinducers, development of diversified mechanisms to understand the cycle and the cycle mechanisms of stored granules.
Assuntos
Matriz Extracelular de Substâncias Poliméricas , Esgotos , Oxidação Anaeróbia da Amônia , Biotecnologia , Águas ResiduáriasRESUMO
Simultaneous nitrogen and phosphorus removal (SNPR) biofilm system is an effective wastewater treatment process. However, the understanding on the mechanism of functional microorganisms driving SNPR is still limited, especially the role of complete ammonia oxidation (comammox) Nitrospira and glycogen-accumulating organisms (GAO). In this study, a sequencing batch biofilm reactor (SBBR) performing SNPR was operated for 249 d. Based on the 16S rRNA gene, comammox amoA amplicon sequencing, metagenomics and batch experiment, we found that comammox Nitrospira was the main ammonia-oxidizing microorganisms (AOM) and provided nitrite for anaerobic ammonia oxidation (anammox) bacteria (AnAOB). Besides, GAO was dominated by the bacteria of genus Defluviicoccus and played a primary role in reducing nitrate rather than nitrite. Fluorescent in situ hybridization (FISH) analysis confirmed that Nitrospira was enriched in the inner layer of the biofilm. Thus, we put forward a novel insight into the mechanism of SNPR biofilm system. Comammox Nitrospira was responsible for nitrite and nitrate production in the inner biofilm, and AnAOB consumed the produced nitrite during the anammox process. While GAO reduced nitrate to nitrite and polyphosphate-accumulating organisms (PAO) converted nitrite to dinitrogen via denitrifying phosphorus removal in the outer biofilm. These findings provide a new understanding in SNPR biofilm system.
Assuntos
Amônia , Nitrogênio , Nitritos , Nitratos , Nitrificação , Fósforo , RNA Ribossômico 16S/genética , Hibridização in Situ Fluorescente , Oxirredução , Bactérias , Biofilmes , Reatores Biológicos/microbiologiaRESUMO
The conventional functional microorganisms for nitrogen and phosphorus removal, such as Nitrosomonas, Nitrobacter, Nitrospira and Candidatus Accumulibacter, were hotspots in past research. However, the role of diverse unconventional functional microorganisms was neglected. In this study, a biofilm system was developed to explore the potential role of unconventional functional microorganisms in nutrients removal. According to the results of microbial community dynamics and metagenomics, complete ammonia oxidizing (comammox) bacteria was 20 times more abundant than ammonia-oxidizing bacteria (AOB) at day 121 and its abundance of amoA gene was almost the same as AOB. Although Nitrospira dominated the nitrite-oxidizing bacteria (NOB), diverse unconventional nxrB-containing microorganisms, particularly Chloroflexi, also significantly contributed to the nitrite oxidation. Binning analysis showed that Myxococcota-affiliated Haliangium had the necessary genes owns by phosphorus-accumulating organisms (PAO) and was likely to be the primary PAO since its abundance (6.38 %) was much higher than other conventional PAO (0.70 %). Comparing metagenome-assembled genomes of comammox bacteria with AOB and ammonia-oxidizing archaea (AOA), it possessed potential metabolic versatility in hydrogen and phosphorus, which may be the primary reason for the positive effect of the alternating anaerobic and aerobic conditions on the enrichment of comammox bacteria. Collectively, our findings broaden the understanding on the microbial mechanism of nitrogen and phosphorus removal in biofilm system.
Assuntos
Amônia , Microbiota , Amônia/metabolismo , Nitrogênio/metabolismo , Oxirredução , Filogenia , Bactérias/genética , Bactérias/metabolismo , Archaea/metabolismo , NitrificaçãoRESUMO
The formation of anammox-hydroxyapatite (HAP) coupled granules has been shown to be an approach to efficient nitrogen removal and phosphorus recovery in the anammox EGSB reactor. However, the granulation cycle mechanism of anammox-HAP coupled granules for sustainable regeneration and growth is still not well understood. In this study, the microstructure, chemical composition and microbial structure of a total of six different-sized granules, from 0.25 mm to 2.8 mm, was determined. An SEM-EDS analysis indicated that the small granules (<0.5 mm) were composed of poly-pellet clusters with anammox biofilms attached to the HAP cores, and the large granules (>0.5 mm) consisted of a three-layer structure: a surface anammox biofilm layer, a middle connection layer, and a HAP mineral inner core. The analysis of elemental composition and microbial structure suggested homogenous granular characteristics regardless of granule size. The dominant microorganisms were anammox bacteria of Candidatus Kuenenia stuttgartiensis and heterotrophic denitrifying bacteria. Based on these results, a granulation cycle mechanism for anammox-HAP coupled granules was proposed for the first time. The growth of the small granules with the simultaneous enlargement of anammox biofilms and HAP cores results in the formation of large granules. Large granules regenerate new small granules in a two-step procedure. The first step is the separation of embryo HAP crystals from the mother core via heterogeneous growth, and the second step is the separation of the biofilms due to biodegradation and shear stress.
Assuntos
Reatores Biológicos , Durapatita , Oxidação Anaeróbia da Amônia , Nitrogênio , FósforoRESUMO
Tar generated as a by-product during biomass gasification contains a high concentration of refractory organic matters. In this study, a hybrid upflow anaerobic sludge-biochar bed reactor was established for tar treatment, and the methane yield was 120-154 NmL-CH4/g-CODinf, 20-30% higher than the control reactor. COD removal and methane production significantly decreased in both reactors when the influent tar concentration was doubled from 4954 mg-COD/L to 9964 mg-COD/L. When the influent concentration was reduced, the biochar packed reactor showed a faster recovery. Batch tests confirmed that higher tar concentration inhibited methane production and induced longer lagphase. Biochar addition effectively relieved the inhibition and prolonged the retention of organic matters. SEM observation and 16S rRNA analysis suggested that biochar also acted as the microbe's carrier, and promoted the growth of some microbes. The results of this study provide new ideas for tar treatment.
Assuntos
Oryza , Esgotos , Anaerobiose , Reatores Biológicos , Carvão Vegetal , Metano , RNA Ribossômico 16S/genética , Eliminação de Resíduos LíquidosRESUMO
Media amendment has been more and more frequently tested in stormwater bioretention systems for enhanced runoff pollutant treatment. However, few studies systematically evaluated the amended system over a long time span, which hindered the further optimization of the proposed amended media. In this study, biochar-pyrite system (PB), conventional sand system (SB), and biochar-woodchip system (WB) were established and operated for 26 months. Media amendment greatly enhanced the dissolved nutrient removal, the highest total dissolved nitrogen removal in PB and WB were 65.6±3.6% and 68.2±2.5%, respectively. Compared with PB, WB could maintain excellent nitrogen removal under long-term operation. In contrast, PB demonstrated stable and more effective total dissolved phosphorus removal during all stages (73.1±3.1%-80.3±4.1%). A high content of phosphorus and organic matter was leached in WB especially at initial operation, while the initial pollutant leaching in PB and SB is much lower, about one-third of WB. Microbial and metabolic function analysis indicated that the microbial community in the bioretention system is complicated and stable. Media amendment enhanced microbial diversity and the relative abundance of functional genera related to nitrogen (Nitrospira, Thauera, Denitratisoma, etc.), sulfur (Thiobacillus, Geobacter, Desulfovibrio, etc.), and carbon cycles (cellulomonas, saccharimonadales, and SBR1031, etc.), which well explained the enhanced pollutant removal and by-product leaching in different systems. Overall, the current study indicates that although media amendment is conducive to enhanced dissolved nutrient removal in bioretention systems, it can hardly maintain both stability and efficiency from initial set-up to long-term operation. In practical application, catchment characteristics, prioritized pollutants, meteorological factors, etc. should all be considered before choosing suitable amended media and its design factors, thereby maximising the stability and efficiency of the bioretention system.
Assuntos
Poluentes Ambientais , Chuva , Areia , Fósforo , Nitrogênio , EnxofreRESUMO
Sulfide-based biofilm processes are increasingly used for wastewater denitrification, yet little is known about the extracellular polymeric substance (EPS) composition of sulfide-oxidizing biofilms. This can have an important impact on biofilm mechanical strength and stability. In this research, the properties and roles of EPS components in biofilm stability were investigated. Weak biofilm stability characterized by high roughness and numerous "needle" structures was visualized by optical coherence tomography (OCT) and microscopy. A high abundance of extracellular DNA (eDNA) and a low protein to polysaccharide ratio were found in the biofilm. The roles of eDNA, protein and polysaccharide in biofilm cohesion and adhesion were identified through enzyme treatment and atomic force microscopy (AFM). The enzymatic hydrolysis of eDNA increased the elastic modulus of biofilms by 57 times and reduced the adhesion energy by 96%. The hydrolysis of proteins led to an increase of elastic modulus by 27 times and a loss of adhesion energy by 95.5%. The enzymatic hydrolysis of polysaccharides caused minimal changes in elastic modulus and adhesion energy. These results suggest that eDNA was the key EPS component for biofilm cohesion and adhesion, possibly because it provided special binding sites and can form strong cross-linking with magnesium or other multivalent cations. This study provided new insights into the role of eDNA in biofilm stability and shed light on the development of sulfide-based denitrifying biofilms.
Assuntos
Biofilmes , Matriz Extracelular de Substâncias Poliméricas , DNA/química , DNA Bacteriano/genética , Matriz Extracelular de Substâncias Poliméricas/metabolismo , Polissacarídeos , Proteínas , SulfetosRESUMO
Solid biomass waste amendment and substrates modification in bioretention systems have been increasingly used to achieve effective dissolved nutrients pollution control in stormwater runoff. However, the risk of excess chemical oxygen demand (COD) leaching from organic carbon sources is often overlooked on most occasions. Pyrite is an efficient electron donor for autotrophic denitrification, but little is known about the efficacy of autotrophic-heterotrophic synergistic effect between additional carbon source and pyrite in bioretention. Here, four bioretention columns (i.e., corncob column (C), pyrite column (P), the corncob-pyrite layered column (L-CP), and the corncob-pyrite mixed column (M-CP)) were designed and filled with soil, quartz sand, and modified media to reveal the synergistic effects. The results showed that the corncob-pyrite layered bioretention could maintain low COD effluent concentration with high stability and efficiency in treating dissolved nutrients. When the influent nitrogen and phosphorus concentrations were 8.46 mg/L and 0.94 mg/L, the average removal rates of ammonia nitrogen, total inorganic nitrogen, and phosphate were 83.6%, 70.52%, and 76.35%, respectively. The scouring experiment showed that placing the corncob in the mulch layer was beneficial to the sustained release of dissolved organic carbon (DOC). Erosion pits were found in the SEM images of used pyrite, indicating that autotrophic denitrifying bacteria in the bioretention could react with pyrite as an electron donor. The relative abundance of Thiobacillus in the submerged zone of the corncob-pyrite layered bioretention reached 38.39%, indicating that the carbon source in the mulch layer increased the relative abundance of Thiobacillus. Coexisting heterotrophic and autotrophic denitrification in this bioretention created a more abundant microbial community structure in the submerged zone. Overall, the corncob-pyrite layered bioretention is highly promising for stormwater runoff treatment, with effective pollution removal and minimal COD emission.
Assuntos
Desnitrificação , Zea mays , Carbono , Ferro , Nitrogênio , Nutrientes , Chuva , Resíduos Sólidos , SulfetosRESUMO
This study investigated the effects of the addition of micro- (Fe, Co, Ni, and Mo) and macro-(Sulfur) nutrients on mono-digestion of sorghum under mesophilic conditions. A continuous stirred-tank reactor was operated for more than 420 days under seven different experimental conditions. The experimental results showed poor performance for methane production and process stability without nutrient supplementation. Serious deficiencies in Co and S were confirmed by nutrient analysis of dry sorghum and digestate. Nutrient augmentation efficiently enhanced methane production and volatile fatty acid (VFA) removal. Methane production reached 223 mL-CH4/g-VS, almost matching the yield predicted by biochemical methane potential (BMP) test. S was demonstrated to have a critical effect on metal availability in the digester. Consequently, to maintain stable methane fermentation, suitable supplementations of S and Co are recommended for anaerobic sorghum mono-digestion.
Assuntos
Biocombustíveis , Sorghum , Anaerobiose , Reatores Biológicos , Metano , NutrientesRESUMO
The potential of the formation of anammox-hydroxyapatite (HAP) granule composites as a cost-effective approach to removing nitrogen and phosphorus in the treatment of wastewater has been recently reported. Before these annamox granules, which consist of an anammox biofilm layer and an HAP crystallizing layer, can be used in applications, the formation mechanism of hydroxyapatite (HAP) encapsulation in the granules needs to be further studied. In this work, the role of extracellular polymeric substance (EPS) secreted by microorganisms and HAP core in Ca and P removal in anammox-HAP coupled granular sludge was investigated. According to the Lamer model, it is possible that the nucleation time of the granules becomes shorter as the crystal seeds. The enhanced buffering capacity of the granules was 0.08 mmol-H+ SS-g-1 with the pH kept above 6.5 for a comfortable environment for anammox. The results of this study show that ion competition and exchange, mainly between cations of Ca2+ and Mg2+ and between anions of PO43- and CO32-, affects the precipitation process. The results of this study indicate that the addition of granule crystal seeds can be used as a strategy to hasten the anammox process, and therefore accelerate the overall process.
Assuntos
Reatores Biológicos , Esgotos , Durapatita , Matriz Extracelular de Substâncias Poliméricas , Nitrogênio , OxirreduçãoRESUMO
The anaerobic ammonium oxidation (anammox) process is an autotrophic nitrogen removal process with great potential as a cost-effective and highly efficient technology in the wastewater treatment field. The main challenges yet to be overcome in this new frontier technology are operating at lower temperatures and achieving a high and stable nitrogen removal efficiency. In this study, an up-flow expanded bed reactor with hydroxyapatite (HAP)-anammox granules was operated for more than 200 days at 7°C. The nitrogen loading rate (NLR) was improved from 1.0 g-N/L/d to 3.6 g-N/L/d, together with a high-level nitrogen removal efficiency of 84-92%, which is the highest to date at extremely low temperatures in a continuous experiment. Candidatus Kuenenia was revealed to be the only dominant anammox genus, with a relative abundance of 35.3-37.5%. The optimal operational temperature was around 35°C and the apparent activation energy (Ea) was calculated as 78.37 kJ/mol. The three-layers architecture and architectural evolution of HAP-anammox granules into HAP-cores and peeling biofilms with outstanding settling performance were characterized. Under 7°C, the high capacity of nitrogen removal with robust removal efficiency using HAP-anammox granules was achieved.
Assuntos
Compostos de Amônio , Nitrogênio , Anaerobiose , Reatores Biológicos , Desnitrificação , Durapatita , Oxirredução , Esgotos , Águas ResiduáriasRESUMO
Biochar is a carbon rich product made from the biomass pyrolysis process. Recently, biochar addition in anaerobic digestion processes has attracted attention for its possible functions to act as pH stabilizing agent, microbial carrier, and interspecies electron transfer. In this study, the effects of rice husk biochar addition in sorghum anaerobic digestion were investigated in batch tests. Under high F/M (food to microorganism) ratio conditions, obvious pH decreases and volatile fatty acids (VFA) accumulation was observed. Addition of 15 g/L biochar was found effective to increase the sorghum maximum methane production rate by 25 % and shorten the lag phase time by 44 %. Further biochar concentration increase showed little effects. Alkalinity increase brought by biochar addition contributed to the performance enhancement. Moreover, the promotive effects of biochar addition on degradation of acetic acid, propionic and butyric acid were not obvious under neutral pH conditions.
RESUMO
The effect of phosphate concentration on the anammox-HAP process was investigated in this work. A high total nitrogen removal efficiency (>82.6%) and a stable total phosphate removal efficiency (>56.2%) was achieved in reactor with the phosphate concentration over 11.4 mg L-1. However, a phosphate concentration below to 5.7 mg L-1, a floatation of sludge occurred caused the deterioration of process. A new understanding for the floatation was divided into three stages: the stable stage, bulking stage and floating stage. First, anammox biofilm coupled with HAP for granulation in the stable stage. Second, the aggregation of bulking sludge resulted in changes in viscoelastic properties of the sludge. Third, the floatation resulted from unreleasable gas bubbles in the granules wrapped a high concentrations of slime layer proteins. Overall, this paper suggests that a control strategy was a sufficient supply of phosphate for the stable operation.
Assuntos
Reatores Biológicos , Esgotos , Anaerobiose , Nitrogênio , Oxirredução , Fosfatos , Eliminação de Resíduos LíquidosRESUMO
While anammox is a cost-effective nitrogen treatment process for wastewater with high nutrient strength, phosphorus remains untouched during this process and needs further treatment. In this study, the nitrogen removal and phosphorus recovery were achieved simultaneously at 25 °C using an anammox expanded bed. A stable high nitrogen removal efficiency of 83.7 ± 4.8% at a 1500 mgN/L influent total nitrogen concentration and a phosphorus removal efficiency of 94.2 ± 1.2% at 100 mg P/L influent total phosphorus were obtained during continuous operation. The effects of the nitrogen loading rate, hydraulic retention time (HRT), pH, Ca2+ and PO43- concentration on the phosphorus removal was verified in the long-term operation of the reactor. The sludge produced contained a high content of phosphorus mainly in the form of hydroxyapatite (HAP), and the sludge composition strongly reflected the nitrogen and phosphorus loading. The structure of the anammox-HAP composite granules was illustrated by the use of fluorescence in situ hybridization (FISH) and Raman spectroscopic mapping analysis. The results in this study indicate that by controlling the operation parameters, it is possible to integrate a high efficiency phosphorus recovery with the anammox process, and significantly reduce the nutrient loading for further wastewater treatment.
Assuntos
Nitrogênio , Fósforo , Anaerobiose , Reatores Biológicos , Desnitrificação , Hibridização in Situ Fluorescente , Oxirredução , EsgotosRESUMO
The characteristic carmine red color due to heme proteins is always observed in enriched anammox biomass. Heme c is a very important co-factor participating the main metabolic reactions with catalytic and electron-transfer potential in the anammox bacteria, and is possible for use as an indicator to evaluate anammox performance. Knowledge of the relationship between the heme c concentration and the anammox reactor performance is, however, very limited available information is constrained at an operation temperature of 35⯰C. In this study, we report the heme c concentration change along with nitrogen removal rate (NRR) in three anammox expanded granular sludge bed reactors operated at different temperatures (15, 25, 35⯰C). The response of specific anammox activity (SAA) to temperature was revealed for biomass originating from three reactors. The results indicate a strong relationship between heme c concentration and NRR at different culture temperatures. The possibility of evaluating the anammox performance by combining heme c quantification and the temperature is revealed.