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1.
Sheng Wu Gong Cheng Xue Bao ; 36(2): 287-294, 2020 Feb 25.
Artículo en Chino | MEDLINE | ID: mdl-32148001

RESUMEN

China is now the largest and only producer of avermectin in the world. However, its current yield is still lower than other similar antibiotics. Therefore, we studied the effect of nitrogen on the growth and the synthesis ability of B1a to improve the overall yield. Nitrogen had significant effects on the cell activity, PMV of Streptomyces avermitilis and the synthesis of B1a in the middle and later phase of fermentation. Additional feeding yeast powder based on carbon-dioxide evolution rate in a 100-L bioreactor significantly improved the synthesis of B1a. The production of avermectin reached 8 697 mg/L, 26.9% higher than the original process. In short, this study will serve in production enhancement of avermectin at industrial production.


Asunto(s)
Fermentación , Carbono , Dióxido de Carbono , China , Ivermectina/análogos & derivados , Nitrógeno
2.
J Environ Manage ; 261: 110173, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32148263

RESUMEN

Green walls that effectively treat greywater have the potential to become a part of the solution for the issues of water scarcity and pollution control in our cities. To develop reliable and efficient designs of such systems, the following two research questions were addressed: what would be the optimal design of a green wall for greywater treatment, and how tall should the system be to assure adequate treatment. This paper reports on (i) a long-term pollutant removal comparison study of two typical green wall configurations: pot and block designs, and (ii) a short-term profile study exploring pollutant retention at different heights of a three-level green wall, across different plant species. Removal of suspended solids (TSS), nitrogen (TN), phosphorus (TP), chemical oxygen demand (COD) and Escherichia coli was tested, as well as various physical parameters. Pot and block designs were found to exhibit similar pollutant removal performance for standard and high inflow concentrations, while the block design was more resistant to drying. However, due to its multiple practical advantages, pot designs are favoured. The greatest removal was achieved within the top green wall level for all studied pollutants, while subsequent levels facilitated further removal of TSS, COD, and TN. Interestingly, colour, pH, and EC increased after each green wall level, which must be taken into account to determine the maximum height of these systems. The optimal size of the system was found to be dependent on plant species choice. The results were used to create practical recommendations for the effective design of greywater treatment green walls.


Asunto(s)
Fósforo , Contaminantes Químicos del Agua , Análisis de la Demanda Biológica de Oxígeno , Ciudades , Color , Nitrógeno , Aguas Residuales
3.
J Environ Manage ; 261: 110204, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32148275

RESUMEN

The effects of exogenous Escherichia coli on nitrogen cycling (N-cycling) in freshwater remains unclear. Thus, seven ecosystems, six with submerged plants-Potamogeton crispus (PC) and Myriophyllum aquaticum (MA)-and one with no plants were set up. Habitats were assessed before and after E. coli addition (107 colony-forming units/mL). E. coli colonization of freshwater ecosystems had significant effects on bacterial community structure in plant surface biofilms and surface sediments (ANOVA, P < 0.05). It reduced the relative abundance of nitrosification bacteria (-70.94 ± 26.17%) and nitrifiers (-47.86 ± 23.68%) in biofilms which lead to significant reduction of ammoxidation in water (P < 0.05). The N-cycling intensity from PC systems was affected more strongly by E. coli than were MA systems. Furthermore, the coupling coefficient of exogenous E. coli to indigenous N-cycling bacteria in sediments (6.061, average connectivity degree) was significantly weaker than that in biofilms (9.852). Additionally, at the genus level, E. coli were most-closely associated with N-cycling bacteria such as Prosthecobacter, Hydrogenophaga, and Bacillus in sediments and biofilms according to co-occurrence bacterial network (Spearman). E. coli directly changed their abundance, so that the variability of species composition of N-cycling bacterial taxa was triggered, as well. Overall, exogenous E. coli repressed ammoxidation, but promoted ammonification and denitrification. Our results provided new insights into how pathogens influence the nitrogen cycle in freshwater ecosystems.


Asunto(s)
Ecosistema , Escherichia coli , Bacterias , Nitrógeno , Ciclo del Nitrógeno
4.
J Environ Manage ; 261: 110241, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32148310

RESUMEN

A novel Anoxic-Aerobic Process (AnAP) that eliminated the anaerobic process was optimized and operated for the simultaneous remediation of phosphate, nitrate, and chemical oxygen demand (COD) from industrial effluents. Two sequential batch reactors (SBR) with AnAP were established for the treatment of effluent from two industries; phosphate fertilizer (AnASBR_PPL) and dairy industry (AnASBR_DW). The adaptability of the bacterial consortium in the SBRs, dominated by denitrifying phosphate accumulating organisms (DNPAOs), facilitates the stable performance of AnAP for simultaneous nutrient and COD removal. Up to 90% and ~80% of COD removal were achieved in AnASBR_PPL and AnASBR_DW, respectively. Nearly complete denitrification was observed along with phosphate removal accounted for ~90% in both the reactors. Granulation of sludge has been widely reported in aerobic reactors; however, interestingly, in this study, partial granulation of the sludge was observed in both the AnASBRs which facilitated the microorganisms to uptake a minimal amount of phosphate and nitrate even under the aerobic condition. The underlying mechanism of DNPAOs and other associated microbes in the consortium were investigated for microbial diversity by 16S rDNA based targeted amplicon sequencing using the Illumina platform and imputed metagenomic analysis. The dominance of Betaproteobacteria, Alphaproteobacteria, Gammaproteobacteria, and Bacteroidia was observed in AnASBRs. At steady-state operation, the identity of the core community members remained largly stable, but their relative abundances changed considerably in both the reactors as a function of varying industrial effluent. However, population of few strains such as Lactobacteriales, Enterobacteriales changed drastically with respect to the influent, as these strains were predominat in AnASBR_DW but not present in AnASBR_PPL. The dominant strains were the vital contributor to the gene pool encoding for denitrification, dephosphatation, TCA cycle, glycolysis, EPS production, and polyhydroxyalkanoate (PHA) storage, etc. Few less abundant but persistent species were also detected as contributors to these functional groups. It unveiled the TCA cycle remains preferable over conventional glycolysis in both the SBR irrespective of carbon source. The new AnASBR was proved to be an efficient alternative system that is energy efficient with higher ease of operation for the treatment of different industrial effluents without fail.


Asunto(s)
Betaproteobacteria , Reactores Biológicos , Análisis de la Demanda Biológica de Oxígeno , Desnitrificación , Nitrógeno , Aguas del Alcantarillado , Eliminación de Residuos Líquidos
5.
J Environ Manage ; 261: 110255, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32148317

RESUMEN

Vegetation Filters (VFs) can be a sustainable solution to treat wastewater and to recover resources such as nutrients, water and biomass from small municipalities and isolated dwellings. However, under certain conditions, the leakage of nutrients, especially of nitrate, can represent a limitation. The addition of two sustainable soil amendments, woodchips and biochar, has been tested as a strategy to improve nutrient attenuation in VFs increasing sorption sites and microbial activity. To this end, unsaturated infiltration and batch experiments have been carried out at laboratory scale. The systems for infiltration experiments contain natural soil, natural soil amended with woodchips and natural soil amended with biochar. To determine the sorption capacity of NH4+, batch tests were performed using an amendment/SWW ratio of 1:20 and an NH4+ initial concentration ranging from 30 to 600 mg L-1. Results from the infiltration experiments show a high attenuation (~95%) of total phosphorous (TP) independently of the amendments. Different behaviour is observed for total nitrogen (TN). The removal of this species is obtained only in the soil amended with woodchips (>85%) whereas the natural soil alone and the soil with biochar have no impact on TN attenuation. In these two porous media, all the NH4+ input concentration is transformed to NO3- that infiltrates without further reactions. According to batch experiment results, the potential role of biochar in the nutrient attenuation is limited to sorption processes (Kd (NH4+) = 21.37-193.18 L kg-1). Woodchips act primarily as a labile source of carbon promoting biodegradation, being more effective for nutrient attenuation than the sorption capacity of biochar.


Asunto(s)
Contaminantes del Suelo , Aguas Residuales , Carbón Orgánico , Nitrógeno , Fósforo , Suelo
6.
Water Res ; 174: 115642, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32114019

RESUMEN

Phytoremediation of reverse osmosis concentrate (ROC) with microalgae can simultaneously achieve multi-functions of ROC treatment, CO2 mitigation and microalgae biolipid production. But the performances are usually inhibited by high free ammonia nitrogen (FAN) concentration and chromaticity of ROC. To offset these negative effects, an integrated technique including electrooxidation pretreatment and Chlorella vulgaris remediation was proposed, in which the ROC was first pretreated with electrooxidation to decrease FAN and chromaticity, and then the oxidized ROC was remediated with microalgae to reclaim nutrients and produce biolipid. Results showed that FAN was sharply reduced from 53.0 mg N/L to 13.9 mg N/L and chromaticity was decreased from 1600 to 100 Pt-Co via electrooxidation. Possible reaction mechanism of nutrients removal was discussed via electron mass balance. Explanation on chromaticity decrease was revealed by analyzing humic acid conversion path with fluorescence characteristics. During microalgae remediation process, nutrients removal rate, microalgae biomass concentration and lipid yield were effectively enhanced in electrooxidized ROC. Energy balance analysis indicated that microalge lipid energy under current density of 3.25 mA/cm2 basically compensated total input energy despite ROC sterilization. This work provided a promising strategy for large-scale ROC treatment and microalgae biolipid production.


Asunto(s)
Chlorella vulgaris , Microalgas , Biomasa , Nitrógeno , Ósmosis , Aguas Residuales
7.
Waste Manag ; 105: 364-372, 2020 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-32114408

RESUMEN

This study aims to assess composting efficiency and quality of compost through the study of the parameters of the Catalan Waste Agency (ARC) data-base by developing indicators useful for industrial sector. The study includes 17 composting plants for an 8-years period (2010-2017), the quantities of materials treated and generated in these plants: biowaste, yard trimmings, refuse and compost, as well as chemical characterization of compost: moisture, total organic matter, organic nitrogen, pH, electrical conductivity, self-heating test, pollutants and ammonium. Plant were sorted into 4 size classes depending on size capacity and into 4 technologies employed during thermophilic phase. Different indicators were developed related to improper fraction content, yard trimmings ratio, mass losses, compost production, refuse generation and plant saturation. The main average results indicate that improper fraction is 10%, process losses 68%, refuse generated 25% and saturation 79%. Differences were observed in size and technology; for instance, smaller plants presented lower improper content, refuse and saturation and higher losses while plants with turned windrows during decomposition presented higher improper, yard trimmings ratio and plants with vessel technology showed lower losses and higher saturation. Also, the compost quality is higher if the plant saturation and improper fraction are below 90% and 7%, respectively. The indicators were useful to assess the process and were related to the compost quality obtained.


Asunto(s)
Compostaje , Residuos de Alimentos , Eliminación de Residuos , Nitrógeno , Plantas , Suelo
8.
Water Res ; 174: 115641, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32120068

RESUMEN

Previous studies have reported that biofilm extracted from full-scale biofilters can serve as nitrogenous disinfection by-product (N-DBP) precursors. Detached biofilm materials could escape during filter ripening and form N-DBP upon chloramination. This study examined the potential breakthrough of biofilm and N-DBP precursors during filter ripening at two water treatment plants (WTPs). The presence of biofilm material in aqueous samples was estimated by total adenosine triphosphate (tATP) levels; N-DBP formation potential (FP) tests were conducted under uniform formation conditions to quantify N-nitrosodimethylamine (NDMA) and haloacetonitrile (HAN4) precursors. While tATP peaks in filter effluent were observed post backwash at both WTPs, temporary increases of effluent NDMA FP were only observed during filter ripening where particle-associated NDMA precursors served as the dominant contributor. Overall, biofilters examined in this study demonstrated a consistent removal of NDMA FP regardless of the filter ripening process.


Asunto(s)
Contaminantes Químicos del Agua , Purificación del Agua , Dimetilnitrosamina , Desinfección , Nitrógeno
9.
Waste Manag ; 105: 405-413, 2020 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-32126368

RESUMEN

The recalcitrance of green waste, caused by its high lignocellulose content, is a technical challenge for accelerating green waste composting. Adjusting the initial ratio of total carbon and total nitrogen (TC/TN) to the optimal range of 25-30:1 is a common strategy to accelerate the composting process. However, because microorganisms can only utilize hydrosoluble nutrients directly, we investigated whether maintaining the ratio of hydrosoluble carbon and hydrosoluble nitrogen (HC/HN) within the optimal range through continuous urea addition can better accelerate green waste composting. We conducted a pilot-scale composting experiment, in which the aforementioned maintaining started at the beginning of composting, or after the thermophilic phase. The results demonstrate that maintaining the optimal HC/HN ratio starting at both periods can, to some extent, direct the TC/TN ratio toward 25-30:1, and can also significantly improve heat generation, pH, lignocellulose degradation, and humification. Moreover, lignin degradation was improved by 3.15-7.33%, cellulose degradation was improved by 6.48-8.15%, and carbon content of humus was increased by 7.19-16.13%. Although the maturity assessment showed that none of the final compost reached maturity within the limited experimental period (48 days), based on the promoted lignocellulose degradation and humification, we conclude that maintaining the HC/HN ratio within the optimal range is a more efficient method to accelerate green waste composting, compared to the initial TC/TN adjustment only once.


Asunto(s)
Compostaje , Carbono , Nitrógeno , Suelo
10.
Waste Manag ; 105: 482-491, 2020 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-32143144

RESUMEN

Rapeseed meal (RSM) is a candidate for biopolymer production due to its abundance, low cost and potential integration with other rapeseed-derived products. However, existing studies pursuing such schemes are limited. The feasibility of different strategies for RSM valorization via protein extraction and polyhydroxyalkanoate production were evaluated. Nitrogen-limited RSM media was produced from hydrolysis of residues which had undergone extensive protein extraction using sodium hydroxide. A study of oxygen-limited fermentation was also performed on hydrolysate of untreated RSM via batch feeding. The typical strategy of using a high carbon-to-nitrogen ratio may not be the most suitable route for polyhydroxyalkanoate (PHA) production using nitrogen-rich biomass as a feedstock. Central composite design-based experiments show that due to mass transfer limitations protein extraction at 1-L scale could only achieve yields around 50% and 69%, at room temperature and 60 °C, respectively. Protein extraction yields reduced with successive extractions, meaning that whilst the RSM hydrolysate is viable for growth, designing a valorization scheme which has the fermentation step dictated by the protein extraction may not be practical/economical. A better route which utilizes oxygen-limitation to initially induce stationary phase was identified, giving accumulation of polyhydroxyalkanoate once the oxygen levels began to recover; 8.93% and 1.75% PHA accumulation in fed-batch cultures of synthetic and RSM media, respectively. The findings demonstrate that decoupling of protein extraction performance from PHA synthesis is feasible. This study provides important insight into the degrees of freedom available in the design of a holistic valorization scheme of rapeseed meal, and high protein lignocellulosic biomass in general.


Asunto(s)
Brassica napus , Polihidroxialcanoatos , Pseudomonas putida , Biomasa , Reactores Biológicos , Fermentación , Nitrógeno , Oxígeno
11.
Waste Manag ; 105: 520-530, 2020 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-32145685

RESUMEN

Characterizing the waste generated from different agro-industrial segments enables the strategic management of residues, with the goal of maximizing recovery within the premises of a circular economy. This research aimed to determine the coefficient of waste generated in broiler chick hatcheries as well as to characterize the waste, taking into account the points of culling and the ages of the laying hens. Furthermore, the waste was used in composting with sheep manure (SM) at increasing inclusion rates (0:100, 10:90, 20:80, 30:70, 40:60, and 50:50). On average, 0.16 kg (DM) of hatchery waste is generated per kg of broiler chicks born. At the hatchery, at least 79% of the total disposal occurs at the hatcher stage. This value is impacted by chicken age (P < 0.05), with birds of a late laying age generating waste with higher contents of carbon (C), volatile solids (VS), ether extract (EE), and nitrogen (N). Culling during egg reception and the manual transfer process account for only 1.8% of the total waste generated on average and thus contribute little to the composition of the overall residues. However, the mechanical transfer process may represent up to 19.0% of the total waste generated by hens of an intermediate laying age. According to the average of all the composting stages, the maximum reduction in solids and C from the hatchery waste was reached when the waste accounted for 50% of the windrow composition. Such conditions resulted in organic fertilizer with the highest N content (2.8%), equivalent to 40.0% more than that in the treatment with no added hatchery waste. The compost resulting from 50% hatchery waste inclusion also had the highest humic acid to fulvic acid (HA:FA) ratio and the highest calcium content due to the higher proportion of eggshells. These findings lead to the recommendation for the inclusion of hatchery waste in composting with SM at a 50% rate by mass.


Asunto(s)
Pollos , Compostaje , Animales , Femenino , Estiércol , Nitrógeno , Ovinos , Suelo
12.
Sci Total Environ ; 711: 135087, 2020 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-32000338

RESUMEN

Oxygen has not been purposely introduced to the autotrophic denitrification systems and simultaneous nitrification/autotrophic denitrification (SNAD) has not been proposed. In this study, oxygen was introduced into a micro-electrolysis-enhanced Fe0-supported autotrophic denitrification (mFe0AD) system. The nitrogen removal performance was investigated and the application potential of iron-scraps-supported simultaneous nitrification/mFe0AD was evaluated. The results showed that Fe0AD was surprisingly enhanced by oxygen together with nitrification at average dissolved oxygen (DO) of 0.08-1.56 mg/L. The ammonia oxidizing bacterial, nitrite oxidizing bacteria, facultative autotrophic denitrificans, and iron compounds transformation bacteria were markedly enriched. Average denitrification rate shifted from 0.116 to 0.340 kg N/(m3·d) with increase of average total nitrogen removal efficiency from 31.4% to 90.5%. Oxygen could enhance the biological conversion and storage of iron compounds, which was capable of reducing the coating of Fe0 surface.The accelerating of oxygen on  Fe0 passivation appeared when increasing the average DO from 1.56 to 2.17 mg/L. Therefore, the SNAD was recommended to be operated at the DO range of 0.08-1.56 mg/L. ME significantly enhanced Fe0AD, and the utilization of iron-scraps reduced its cost. The denitrification rate is comparable with methanol supported heterotrophic denitrification with 58.9% reduction on the cost. The iron-scraps supported SNAD is competitive in both denitrification rate and costs in the ammonia contaminated low-carbon water treatment.


Asunto(s)
Desnitrificación , Nitrificación , Reactores Biológicos , Electrólisis , Hierro , Nitrógeno , Oxígeno
13.
Sci Total Environ ; 711: 135108, 2020 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-32000343

RESUMEN

Submerged macrophytes are widely distributed primary producer that play important roles in maintaining healthy aquatic ecosystems. Generally, the relationships between macrophytes and environmental factors are complicated, so nonlinear nonparametric models with relatively flexible structures are optimal for macrophyte habitat simulation. In this study, generalized additive model (GAM) was used to evaluate the response of the submerged macrophytes biomass to water environmental factors in the Baiyangdian Lake. Forward stepwise method was used to implement model optimization. Likelihood ratio test was used to determine whether adding a variable enhances the model performance. Four individual variables (water depth, transparency, total nitrogen, and total phosphorus) and two interaction terms (water depth × transparency and water depth × total phosphorus) were included in the optimal GAM. The optimal model explained 70.5% of the biomass variation with a relatively low residual deviance value (22.40). There was a significant correlation between the measured and predicted data (R2 = 0.716, p = 0.0004). The response lines generated by the model indicated that macrophyte biomass had a positive correlation with transparency but negative correlations with total nitrogen and nitrite nitrogen in water. The response patterns of macrophyte biomass to water depth and total phosphorus were unimodal. The biomass reached the maximum value when the water depth was about 2.1 m and the total phosphorus concentration was 0.07 mg/L. Water depth and transparency, which affect light availability, are critical physical variables affecting the conditions associated with the submerged macrophytes, and excess nitrite and phosphorus limiting macrophyte biomass.


Asunto(s)
Biomasa , Lagos , Nitrógeno , Fósforo
14.
Waste Manag ; 105: 110-118, 2020 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-32044549

RESUMEN

Antibiotic-resistant bacteria are a threat to human and animal health. In recent years, the presence of extended-spectrum-ß-lactamase (ESBL)-producing Escherichia (E.) coli in chicken manure, which is used as organic fertilizer, is a concern. The aim of the present study was to determine the effects of the carbon/nitrogen (C/N) ratio and moisture content (MC) on the survival of ESBL-producing E. coli during laboratory-scale composting of chicken manure. Nine different compost mixtures were enriched with an ESBL-producing E. coli strain to an initial concentration of 7 log10 CFU/g, and the number of E. coli, temperature, and chemical conditions during composting were determined. The fastest decrease in E. coli occurred for all mixtures with a C/N ratio of 10:1. Additionally, dry mixtures with an MC of 20% and a C/N ratio of either 10:1 or 40:1 exhibited faster reductions in E. coli than the moist mixtures did, despite having lower maximum temperatures within the bioreactors. The decimal reduction times ranged from 0.27 days in a mixture with a C/N ratio of 10:1 and 40% MC to 4.82 days in a mixture with a C/N ratio of 40:1 and 40% MC. Both the C/N ratio and MC had a significant effect on the number of ESBL-producing E. coli and on temperature development; the C/N ratio additionally affected the pH value and content of ammoniacal nitrogen during chicken manure composting. The results of this study demonstrate a considerable range of mechanisms involved in the inactivation of E. coli during chicken manure composting.


Asunto(s)
Compostaje , Animales , Carbono , Pollos , Escherichia coli , Estiércol , Nitrógeno , Suelo
15.
Waste Manag ; 105: 190-197, 2020 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-32078983

RESUMEN

Analyzing diazotrophic community may help to understand nitrogen transformation in composting and improves the final compost quality. In this study, diazotrophic community dynamics were investigated in terms of nifH gene during dairy manure and corn straw composting with biochar addition using high-throughput sequencing. Biochar decreased the diversity of diazotrophic community and altered diazotroph community structure during composting. At phylum level, Proteobacteria, Actinobacteria and Firmicutes were dominant diazotrophic communities throughout composting process. Biochar addition registered higher correlation coefficient (R) between physicochemical factors (temperature, ammonium (NH4+-N) and nitrate (NO3--N)) and diazotroph community composition. Rhodopseudomonas and Pseudoxanthomonas was the key diazotrophic communities influencing NH4+-N transformation in control (CK) and biochar compost (BC), respectively, while for NO3--N transformation Clostridium and Bradyrhizobium in CK, Azospira and Methylocystis in BC served as predominant factors. These results indicated that addition of biochar altered the key diazotroph communities influencing nitrogen transformation. Furthermore, some diazotrophs (e.g. Rhodopseudomonas, Bradyrhizobium and Azospira) affecting NH4+-N and NO3--N transformation were also observed to be mediating total nitrogen (TN). Interestingly, interactions between diazotrophic communities were observed and these interactions could also influence nitrogen transformation.


Asunto(s)
Compostaje , Carbón Orgánico , Estiércol , Nitrógeno , Suelo
16.
Water Res ; 174: 115604, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32088388

RESUMEN

Microorganism-derived dissolved organic nitrogen (mDON) represents a significant and inevitable portion of dissolved organic nitrogen (DON) in the wastewater biotreatment processes. In the existing method, mDON concentrations are indirectly measured by the values of DON concentrations from the reactors with DON-free influent. However, this becomes problematic when influent contains DON. Especially when the real wastewater is involved, the paucity of the direct methods to quantitatively measure mDON is a major barrier to further research. This limitation is due to the difficulty of segregating mDON from the other nitrogenous organics, e.g., influent DON. In this study, we propose the ASM-mDON model based on ASM #1, which incorporates the production and consumption of mDON in the activated sludge processes to predict the mDON concentrations. In four independent lab-scale tests, our model was established and calibrated to obtain the accurate values of mDON (R2 = 0.929, p < 0.05), and the validity and applicability of the model were successfully examined by comparing the simulated and measured data. Moreover, the universality of the ASM-mDON model was further confirmed by simulating mDON production in a full-scale wastewater treatment plant. A reasonable prediction of mDON formation was shown in a full-scale test (1.98 ± 0.71 mg/L in June and 1.51 ± 0.54 mg/L in July) and is indirectly supported by an algal bioassay (p < 0.05, t-test). This study provides a useful approach to the efficient and accurate evaluation of mDON formation, which will improve current strategies designed to minimize the effluent mDON in wastewater bioprocesses.


Asunto(s)
Nitrógeno , Aguas del Alcantarillado , Eliminación de Residuos Líquidos , Aguas Residuales
17.
Water Res ; 174: 115632, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32105998

RESUMEN

The granulation of anaerobic ammonium oxidation (Anammox) biomass plays a key role in high rate performance of upflow-type Anammox reactors. However, the formation of cavitation inside granules may result in sludge flotation problem, which negatively affects the operation stability. For quantitative evaluation of the Anammox granules flotation in upflow reactors, an integrated mathematical model was formulated based on the principles that the limitation of substrate diffusion would result in bacterial starvation, lysis and subsequently aiding the formation of cavitation in the inner zone of granules. The proposed model is used to investigate the possible mechanism of cavitation formation and granules flotation. The combined modelling and experimental results showed that the model predictions matched well with the actual floating behavior of granules (R2 = 0.83 for settled sludge and 0.76 for floating sludge). Based on the model results, the granule flotation could be divided into three zones namely (i) no-flotation zone (no flotation occurrence), (ii) transition zone (flotation with a part of granules), and (iii) flotation zone (inevitable flotation occurrence). The floating behavior of granules was mainly influenced by granule diameter (2.5-4.5 mm) and substrate concentration (NO2-N, 50-250 mg/L) in the transition zone. The optimum granule diameter to avoid flotation but with excellent settling performance was identified around 2.5 mm. Additionally, the granule size is more sensitivity to flotation than substrate concentration. Hence, controlling the size of granules is more important to alleviate granule flotation in Anammox reactors' operation.


Asunto(s)
Reactores Biológicos , Aguas del Alcantarillado , Anaerobiosis , Bacterias , Modelos Teóricos , Nitrógeno , Oxidación-Reducción
18.
Sci Total Environ ; 713: 136404, 2020 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-32019008

RESUMEN

A two-stage treatment system that included vertical flow (VF) and free-water surface (FWS) constructed wetlands was investigated for the dual purposes of sewage treatment and reuse. The VF included four layers (biochar, sand, gravel, and sandy soil), and the FWS was installed after the VF and used as a polishing tank. Two types of local plants, namely Colocasia esculenta and Canna indica, were planted in the VF and FWS, respectively. The system operated for approximately six months, and the experimental period was categorized into four stages that corresponded to changes in the hydraulic loading rate (HLR) (0.02-0.12 m/d). The removal efficiencies for total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD5), ammonia (NH4-N), and total coliform (Tcol) were 71 ± 11%, 73 ± 13%, 79 ± 11%, 91 ± 3%, and 70 ± 20%, respectively. At HLRs of 0.04-0.06 m/d, the COD and BOD5 levels satisfied Vietnam's irrigation standards, with removable rates of 64% and 88%, respectively, and the TSS and Tcol levels satisfied Vietnam's standards for potable water. Furthermore, the NO3-N levels satisfied the reuse limits, whereas the NH4-N levels exceeded the reuse standards. At high HLRs (e.g., 0.12 m/d), all the effluent parameters, except Tcol and NO3-N, exceeded the standards.


Asunto(s)
Aguas del Alcantarillado , Humedales , Análisis de la Demanda Biológica de Oxígeno , Carbón Orgánico , Nitrógeno , Vietnam , Eliminación de Residuos Líquidos , Agua
19.
Sci Total Environ ; 713: 136635, 2020 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-32019022

RESUMEN

Biochar application in agricultural soils can be highly beneficial to plant productivity. However, how plant productivity response (PPR) [% change of plant yield from control (without biochar application)] to biochar application is affected by biochar properties, soil conditions, and their combinations is still unclear. Therefore, a meta-analysis based on 1254 paired comparisons from 153 published studies was conducted. The grand mean of PPR was estimated to be 16.0 ± 1.3%, regardless of biochar/soil conditions. Meanwhile, a large variation of PPR from -31.8% to 974% was also observed under different biochar or/and soil conditions. Specifically, biochar properties including pH, cation exchange capacity (CEC), contents of carbon and ash, bulk density, and soil conditions including texture, pH, CEC, nitrogen content, and C/N ratio significantly affected the results of PPR to biochar addition. Furthermore, the liming effect, improvement in soil physical structure, and increased nutrient use efficiency were suggested as the key mechanisms for the positive PPR in biochar-amended soils. Moreover, PPR could be significantly affected (strengthened or weakened) by the combined effect of biochar properties and soil conditions. Overall, the application of biochars with high ash content (or low carbon content) into sandy soils or acidic soils is highly recommended for increasing plant productivity. This meta-analysis will provide helpful information to elucidate the combined effect of biochar properties and soil conditions on plant growth, which is critical for developing engineered biochar with specific functionality to promote plant production and food security.


Asunto(s)
Carbón Orgánico , Suelo , Nitrógeno , Desarrollo de la Planta
20.
Sci Total Environ ; 713: 136677, 2020 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-32019033

RESUMEN

Crop residues are produced from agriculture in large amounts globally. Crop residues are known to be a source of nitrous oxide (N2O); however, contrasting results have been reported. Furthermore, the effect of crop residues on nitric oxide (NO) and methane (CH4) fluxes has not been well studied. We investigated N2O, NO, and CH4 fluxes after low C/N crop residue (cabbages and potatoes) inputs to lysimeter fields for two years using with automated flux monitoring system. Lysimeters were filled with two contrasting soil types, Andosol (total C: 33.1 g kg-1; clay: 18%) and Fluvisol (17.7 g kg-1; 36%). Nitrogen application rates were 250 kg N ha-1 of synthetic fertilizer and 272 kg N ha-1 of cow manure compost for cabbage, and 120 kg N ha-1 of synthetic fertilizer and 136 kg N ha-1 of cow manure compost for potato, respectively. Large N2O peaks were observed after crop residues were left on the surface of the soil for 1 to 2 weeks in summer, but not in winter. The annual N2O emission factors (EFs) for cabbage residues were 3.02% and 5.37% for Andosol and Fluvisol, respectively. Those for potatoes were 7.51% and 5.10% for Andosol and Fluvisol, respectively. The EFs were much higher than the mean EFs of synthetic fertilizers from Japan's agricultural fields (0.62%). Moreover, the EFs were much higher than the Intergovernmental Panel on Climate Change (IPCC) default N2O EFs for synthetic fertilizers and crop residues (1%). The annual NO EFs for potatoes were 1.35% and 2.44% for Andosol and Fluvisol, respectively, while no emission was observed after cabbage residue input. Crop residues did not affect CH4 uptake by soil. Our results suggest that low C/N crop residue input to soils can create a hotspot of N2O emission, when temperature and water conditions are not limiting factors for microbial activity.


Asunto(s)
Compostaje , Agricultura , Animales , Bovinos , Femenino , Fertilizantes , Japón , Metano , Óxido Nítrico , Nitrógeno , Óxido Nitroso , Suelo
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