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1.
Water Sci Technol ; 82(2): 281-291, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941170

RESUMO

Biofilters based on earthworms-microorganisms represent, particularly in developing countries, an interesting alternative for domestic wastewater treatment due to their easy operation and low cost. However, there are several operational aspects that should be better understood in order to improve their performance. This paper studies the effect of using intermittent hydraulic loading rates to improve organic matter and nutrient removal from domestic wastewater using these biofilters. Three laboratory-scale columns, operating at a 2.5 m3 m-2day-1 hydraulic loading rate, were used. The B1-24 h, B2-8 h, B3-4 h column loading rates indicate that the columns were operated continuously for 24, 8 and 4 h, respectively. Each column (biomass biofilm/earthworms, redox potential, and head loss) and its corresponding operational performance parameters (TCOD, NH4+, NO3-, NO2-, TP) were monitored. The results showed that the B2-8 h intermittent hydraulic loading rate results in the best global performance, with 74%, 57%, and 20% average removal efficiencies for TCOD, nitrogen, and phosphorus, respectively. Moreover, it showed the best biomass growth (biofilm and earthworms), activity (as redox potential changes) and the lowest clogging effects (up to -1.0 cm). The intermittent operation influences the behavior of the earthworm-microorganism biofilters and offers the possibility of optimizing its global performance and achieving a resilient technology.


Assuntos
Oligoquetos , Águas Residuárias , Animais , Reatores Biológicos , Filtração , Nitrogênio/análise , Nutrientes , Fósforo , Eliminação de Resíduos Líquidos
2.
Water Sci Technol ; 82(2): 303-314, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941172

RESUMO

The first full-scale semi-centralized wastewater treatment and resource recovery system based on source separation was implemented from 2014. To assess the operation performance, operating costs and resolve the problems faced in this system, the latest operation data from April 2017 to September 2018 was investigated. The results show that greywater and blackwater modules exhibited good removal performance for organics and nutrients, although misconnection between pipelines existed and influent loading rates fluctuated. The effluent could meet reuse standards. The biogas production rates of raw sludge could reach 7.27-10.9 m3 gas·per cubic raw sludge. The specific cost of treated water was higher than in a conventional treatment system. Power consumption made a major contribution to the total cost with a proportion of 55.3-94.2%. After optimizing and considering the comprehensive efficiencies, the costs would be affordable. The dewatered sludge of the anaerobic digestion module has been applied to agricultural and landscaping soil. It is suggested that organics in blackwater could be recovered as volatile fatty acids with high-efficiency anaerobic fermentation and used as an external carbon source for short-cut biological nitrogen removal. In conclusion, the semi-centralized system will be a feasible and sustainable alternative for conventional treatment systems in future.


Assuntos
Reatores Biológicos , Águas Residuárias , Ácidos Graxos Voláteis , Nitrogênio , Esgotos , Eliminação de Resíduos Líquidos
3.
Water Sci Technol ; 82(2): 330-338, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941174

RESUMO

Nitrogen removal in osmosis membrane bioreactor (OMBR) is important to its applications but remains a challenge. In this study, a bioelectrochemically-assisted (BEA) operation was integrated into the feed side of OMBRs to enhance nitrogen removal, and sodium acetate was served as a draw solute and supplementary carbon source for the growth of denitrifying bacteria due to reversed-solute. The effects of operation mode and influent ammonium (NH4+) concentration were systematically examined. Compared to a conventional OMBR, the integrated BEA-OMBR achieved higher total nitrogen removal efficiency of 98.13%, and chemical oxygen demand removal efficiency of 95.83% with the influent NH4+-N concentration of 39 mg L-1. The sequencing analyses revealed that ammonia-oxidizing bacteria (0-0.04%), nitrite-oxidizing bacteria (0-0.16%), and denitrifying bacteria (1.98-8.65%) were in abundance of the microbial community in the feed/anode side of integrated BEA-OMBR, and thus BEA operation increased the diversity of the microbial community in OMBR. Future research will focus on improving nitrogen removal from a high ammonium strength wastewater by looping anolyte effluent to the cathode. These findings have demonstrated that BEA operation can be an effective approach to improve nitrogen removal in OMBRs toward sustainable wastewater treatment.


Assuntos
Desnitrificação , Nitrogênio , Reatores Biológicos , Osmose , Águas Residuárias
4.
Water Sci Technol ; 82(2): 339-350, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941175

RESUMO

This paper presents the sensitivity and uncertainty analysis of a plant-wide mathematical model for wastewater treatment plants (WWTPs). The mathematical model assesses direct and indirect (due to the energy consumption) greenhouse gases (GHG) emissions from a WWTP employing a whole-plant approach. The model includes: (i) the kinetic/mass-balance based model regarding nitrogen; (ii) two-step nitrification process; (iii) N2O formation both during nitrification and denitrification (as dissolved and off-gas concentration). Important model factors have been selected by using the Extended-Fourier Amplitude Sensitivity Testing (FAST) global sensitivity analysis method. A scenario analysis has been performed in order to evaluate the uncertainty related to all selected important model factors (scenario 1), important model factors related to the influent features (scenario 2) and important model factors related to the operational conditions (scenario 3). The main objective of this paper was to analyse the key factors and sources of uncertainty at a plant-wide scale influencing the most relevant model outputs: direct and indirect (DIR,CO2eq and IND,CO2eq, respectively), effluent quality index (EQI), chemical oxygen demand (COD) and total nitrogen (TN) effluent concentration (CODOUT and TNOUT, respectively). Sensitivity analysis shows that model factors related to the influent wastewater and primary effluent COD fractionation exhibit a significant impact on direct, indirect and EQI model factors. Uncertainty analysis reveals that outflow TNOUT has the highest uncertainty in terms of relative uncertainty band for scenario 1 and scenario 2. Therefore, uncertainty of influential model factors and influent fractionation factors has a relevant role on total nitrogen prediction. Results of the uncertainty analysis show that the uncertainty of model prediction decreases after fixing stoichiometric/kinetic model factors.


Assuntos
Gases de Efeito Estufa , Águas Residuárias , Análise da Demanda Biológica de Oxigênio , Nitrogênio , Incerteza , Eliminação de Resíduos Líquidos
5.
Water Sci Technol ; 82(2): 351-363, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941176

RESUMO

The migration of nitrogen (N) and phosphorous (P) from farmland to river not only results in fertilizer inefficiency, but also aggravates water pollution and eutrophication. It is of great significance to construct a reasonable vegetation buffer zone between the river and farmland to protect water quality. By using constructed buffer strips and runoff hydrometric devices, quantitative research was conducted on removal loads of N and P in a field experiment of different vegetated and slope strips. Results showed that removal rates of TN, NH4+-N, and TP by different vegetated strips were 2-3 times higher than the control group. The removal ratios of seepage accounted for 73.6%, 66.9%, 73.9% of total seepage and runoff in three vegetated strips, respectively. On the 2% gradient strips with Cynodon dactylon, the removal ratios of TN, NH4+-N, and TP were 36%, 34%, 37%, which were higher than that with 5% gradient, respectively. And removal ratios from the seepage of 2%, 3%, 4%, and 5% gradient strips were 71.66%, 68.14%, 64.39%, and 61.93% of the total, respectively. The conclusion can provide the basis of vegetation and slope optimization for the design and construction of a riparian buffer zone, so as to control non-point source pollution effectively.


Assuntos
Nitrogênio/análise , Fósforo , Fertilizantes , Rios , Poluição da Água
6.
Water Sci Technol ; 82(2): 364-372, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941177

RESUMO

Aerobic granular sludge process as a promising biotechnology has been one of the research hotspots in the area of wastewater treatment during the last two decades. In our study, after around 60 days' operation, filamentous granular sludge (FGS) was formed under low aeration (SAV = 0.085 cm/s) and multi-feeding conditions. The characteristics of FGS and the performance of the FGS system for organic matter and nutrients removal were investigated. The results showed that chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies were relatively stable, while COD removal efficiency increased from 82% to 94% in the presence of sulfamethoxazole (SMZ) at low concentration (1 mg/L). At the same time, the TP removal efficiency could be improved and maintained at around 75%, while TN removal efficiency was flocculated at around 50%. The analysis of microbial diversity showed that Thiothrix and Trichococcus as typical filamentous species were detected and dominant in the FGS system. The abundance of Thiothrix increased from 15% to 34%, while Trichococcus decreased from 23% to 3% in the presence of SMZ.


Assuntos
Esgotos , Eliminação de Resíduos Líquidos , Aerobiose , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Nitrogênio , Águas Residuárias
7.
Water Sci Technol ; 82(2): 373-385, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941178

RESUMO

To evaluate the enhancing of the biological nitrogen removal effectiveness by electromagnetic wave loading on returned sludge in the A/A/O reactor, some experiments were completed with the returned sludge loaded by 2,450 MHz electromagnetic wave. The excess sludge yield and pollutant removal effect of the system were evaluated. Results showed that stronger denitrification effect and less sludge yield were achieved. When 30% of the returned sludge was loaded by electromagnetic wave, the actual denitrification efficiency increased by 7% without dosage. The dissolution of carbon, nitrogen and phosphorus from loaded returned sludge was detected, thus providing the system with a supplemental carbon source of 4.6 g/d SCOD. The specific oxygen uptake rate of the oxic activated sludge increased by 14%, and the denitrification rate of the anoxic activated sludge increased by 29%. Illumina MiSeq analysis showed that the microbial richness increased obviously, and denitrifying bacteria (i.e. Dechloromonas, Zoogloea and Azospira, etc.) were accumulated.


Assuntos
Nitrogênio , Esgotos , Anaerobiose , Reatores Biológicos , Desnitrificação , Radiação Eletromagnética , Fósforo , Eliminação de Resíduos Líquidos
8.
Water Sci Technol ; 82(2): 386-400, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941179

RESUMO

For the utilization of nitrogen and phosphorus in rural sewage tailwaters after biological treatment, four systems were examined regarding their ability to purify tailwaters of rural domestic sewage: a hydroponic vegetable system (HV), a subsurface flow constructed wetland (SFCW), a compound system with HV followed by SFCW (HV-SFCW), and a compound system with SFCW followed by HV (SFCW-HV). Parameters of the four systems were optimized to maximize the utilization efficiency of nitrogen and phosphorus, and the characteristics and pollutant removal efficiency of the process were investigated. Moreover, the edible security of vegetables was also evaluated. Results showed that the optimal hydraulic loadings for the four systems were 0.2, 0.3, 0.3, and 0.3 m3/(m2·d) (the lowest being the HV), respectively. In the combined system of HV-SFCW, high contribution proportions of the HV unit to the removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were obtained, reaching 46.7%, 58.1%, and 53.7%. The heavy metal content of plants harvested met the standards of the National Food Safety Standard Limit of Pollutants in Food (GB 2762-2012). Overall, the compound HV-SFCW system achieved the best performance, ensuring that effluent water quality met national standards and realized the effective utilization of nitrogen and phosphorus.


Assuntos
Ipomoea , Esgotos , Hidroponia , Nitrogênio/análise , Fósforo , Verduras , Eliminação de Resíduos Líquidos , Áreas Alagadas
9.
Mar Environ Res ; 160: 104986, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32907724

RESUMO

Although eutrophication is considered a major driver for global seagrass loss with aquaculture effluents being a main factor, little is known about the effect on seagrass meadows in eastern Asia and their resilience to long-term nutrient impact. Seagrass meadows impacted by land-based aquaculture since the 1990s, were visited in 2008/2009 and revisited after another 9 years of effluent exposure. During that period seagrass aboveground biomass declined by 87%. Species diversity decreased with increasing effluent exposure. A δ15N of 9.0‰ of seagrass leaves and additional biogeochemical and biological indicators identify pond effluents as the driver of the observed eutrophication. When continuously exposed to dissolved inorganic nitrogen (DIN) concentrations exceeding a calculated threshold of 8 µM DIN seagrass meadows will disappear. Chronic nutrient pollution from aquaculture effluents can lead to a reduction of biodiversity and ultimately to a complete loss of seagrasses along the aquaculture-dominated coasts in E and SE Asia.


Assuntos
Aquicultura , Eutrofização , Nitrogênio , Biodiversidade , Biomassa
10.
Sci Total Environ ; 740: 139740, 2020 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-32927530

RESUMO

Most wetlands have been subject to changes in flooding regimes by climate change and human activities, resulting in widespread alteration of wetland plants at different organizational levels. However, scaling the responses of wetland plants to changes in flooding regimes is still challenging, because flooding could indirectly affect wetland plants through affecting environment factors (e.g. soil properties). During the non-flooding period, we investigated leaf N and P stoichiometry at three organizational levels (intra-species, inter-species, inter-community) along a flooding duration gradient in a lakeshore meadow of Poyang Lake floodplain, China. At the intra-species level, leaf N and P stoichiometry showed species-specific responses to flooding duration. At the inter-species level, leaf N or P contents or N:P ratio showed no significant response to flooding duration. At the inter-community level, leaf N and P contents significantly increased with flooding duration, while leaf N:P ratio decreased. At each organizational level, leaf N and P stoichiometry showed poor correlation with soil N and P stoichiometry. Moreover, intra-specific responses of leaf N and P contents to flooding duration and soil nutrient content increased with mean flooding duration of species distribution, which was the index of species hydrological niche. Intraspecific variation had lower contribution than species turnover to variations in community leaf nutrient stoichiometry. In all, flooding duration affected leaf N and P stoichiometry mainly through direct pathway at the intra-species and inter-community level, rather than the indirect pathway via soil nutrient stoichiometry. Therefore, our results have implications for scaling up from environmental conditions to ecosystem processes via wetland plant communities.


Assuntos
Ecossistema , Nitrogênio/análise , China , Nutrientes , Fósforo , Folhas de Planta/química , Solo
11.
Sci Total Environ ; 740: 140169, 2020 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-32927550

RESUMO

Hydrological extremes of unusually high or low river discharge may deeply affect the biogeochemistry of coastal lagoons, but the effects are poorly explored. In this study, microbial nitrogen processes were analyzed through intact core incubations and 15N-isotope addition at three sites in the eutrophic Sacca di Goro lagoon (Northern Adriatic Sea) both under high discharge (spring) and after prolonged low discharge (late-summer) of the main freshwater inputs. Under high discharge/nitrate load, denitrification was the leading process and there was no internal recycling. The site located at the mouth of the main freshwater input and characterized by low salinity exhibited the highest denitrification rate (up to 1150 ± 81 µmol N m-2 h-1), mostly sustained by nitrification stimulated by burrowing macrofauna. In contrast, we recorded high internal recycling under low discharge, when denitrification dropped at all sites due to low nitrate concentrations, reduced bioturbation and nitrification. The highest recycling was measured at the sites close to the sea entrance and characterized by high salinity and particularly at the clams cultivated area (up to 1003 ± 70 µmol N m-2 h-1). At this site, internal recycling was sustained by ammonification of biodeposits, bivalve excretion and dissimilatory nitrate reduction to ammonium (DNRA), which represented 30% of nitrate reduction. Flash floods and high nitrate loads may overwhelm the denitrification capacity of the lagoon due to the reduced residence time and to the saturation of microbial enzymatic activity, resulting in high transport of nitrate to the sea. Prolonged dry periods favor large internal recycling, due to a combination of high temperatures, low oxygen solubility and low bioturbation, which may prolong the extent of algal blooms with negative effects on lagoon biogeochemical services. We conclude that hydrological extremes, which are expected to become more frequent under climate change scenarios, strongly alter N cycling in coastal sediments.


Assuntos
Compostos de Amônio/análise , Animais , Desnitrificação , Sedimentos Geológicos , Hidrologia , Nitratos/análise , Nitrogênio/análise
12.
J Environ Manage ; 263: 110333, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883470

RESUMO

The Total Maximum Daily Load (TMDL) program established by the United States Environmental Protection Agency (US EPA) to improve America's water quality is being applied to the Chesapeake Bay watershed to mitigate the "dead zone" problem. Agricultural activities are the major nonpoint source of nitrogen (N), contributing 44% of total N to the Bay. Best Management Practices (BMPs) are recognized as an effective way to mitigate N loss of agricultural activities. However, because of physical and economic heterogeneity in agricultural regions, targeting BMPs to areas that produce disproportionate nutrient losses has the potential to reduce the costs of achieving water quality goals. The purpose of this study is to examine the potential to reduce costs of meeting a regional water quality goal by targeting N load reductions within- and across-counties. Based on TMDL developed by the US EPA in 2010 for the Chesapeake Bay watershed, the N reduction goal is 35% for Pennsylvania by 2025. We examine the effects of targeting the required reductions within counties, across counties, and both within and across counties for the Susquehanna watershed. Using the uniform strategy to meet 35% N reduction as the baseline, results show that costs of achieving a regional 35% N reduction goal can be reduced by 13%, 31% and 36% with cross-county targeting, within-county targeting and within and across county targeting, respectively. Cost effectiveness of government subsidy programs for water quality improvement in agriculture can be increased by targeting them to areas with lower N abatement costs.


Assuntos
Nitrogênio , Qualidade da Água , Agricultura , Análise Custo-Benefício , Pennsylvania
13.
J Environ Manage ; 263: 110353, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883472

RESUMO

Nowadays, as the world population is in need of creating alternative materials that can replace conventional plastics, microalgae biomass may be identified as a viable source for producing more environmentally friendly materials. Scenedesmus sp and Desmodesmus sp are the main components (~80%) of a microalgae consortium (MC) that first has been used to remove Nitrogen and Phosphorus from wastewater. The potential to develop bioplastic materials from MC considering its relatively high protein content (~48%) has been assessed in the present manuscript, using as a reference a commercial biomass rich an Arthrospira specie (AM) also present in the studied consortium. Bioplastics were obtained through injection moulding of blends obtained after mixing with different amounts of glycerol, and eventually characterized using Dynamic Mechanical Thermal Analysis (DMTA), water immersion and tensile tests. All bioplastics displayed a glass transition temperature around 60 °C, showing a thermoplastic behavior which is less pronounced in the CM based bioplastics. This would imply a greater thermal resistance of bioplastics produced from the biomass harvested in wastewater. Moreover, these bioplastics showed a lower ability to absorb water when immersed, due to the lower deformability displayed in the tensile tests. The mechanical properties of all samples, independently of the nature of the biomass, were improved when the presence of the biomass was higher. Therefore, results here presented prove the potential of valorisation of microalgae consortia used in the effective treatment of wastewater through the development of bioplastic materials.


Assuntos
Microalgas , Scenedesmus , Biomassa , Nitrogênio/análise , Fósforo , Águas Residuárias
14.
J Environ Manage ; 263: 110395, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883477

RESUMO

One of the main drawbacks of upflow anaerobic sludge blanket (UASB) reactors that treat low-strength sewage at room temperature is related to the low quality of their effluents in terms of dissolved methane, organic matter, and nitrogen content. The present study aims to evaluate the feasibility of using an integrated fixed-film activated sludge (IFAS) system as an alternative post-treatment technology to mitigate the environmental impact of such effluents. For this purpose, a pilot plant composed of a UASB (120 L) followed by an IFAS (66 L) system was operated for 407 days. Special attention was paid to the suspended biomass retention capacity and the dissolved methane and nitrogen removal potential of the IFAS post-treatment system. Furthermore, the role of carriers on denitrification and nitrification processes and the microbial communities present in the biofilm were also analyzed. Average total chemical oxygen demand (CODT) and ammonium removal efficiencies of 92 ± 3% and around 57 ± 16% were attained throughout the entire operation, respectively. During a first period in which biomass was maintained in both biofilms and suspension, and nitrite was the main electron acceptor, maximum nitrogen removal and methane removal efficiencies of 32.5 mg TN L-1 and 93% were observed in the IFAS system, respectively. However, throughout the second period, in which suspended biomass was completely washed out from the IFAS system, and nitrate became the main electron acceptor, these values decreased to 18 ± 4 mg TN Lfeed-1 and 77 ± 12%, respectively. Surprisingly, throughout the entire operation, it was observed that around 50 and 41% of the total nitrogen and methane removals observed in the IFAS system, respectively, were carried out in the aerobic compartment. Aerobic methane oxidizers and anammox were detected with significant relative abundances in the biofilm carriers used in the anoxic and aerobic compartments using 16S rRNA gene amplicon sequencing analysis. Therefore, the use of an IFAS system could be suited to diminish greenhouse gas emissions and nutrients concentration for those sewage treatment plants that used UASB systems, especially in countries with temperate and warm climates.


Assuntos
Nitrogênio , Esgotos , Anaerobiose , Reatores Biológicos , Metano , RNA Ribossômico 16S , Eliminação de Resíduos Líquidos
15.
Sci Total Environ ; 741: 140480, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32886969

RESUMO

The co-treatment of two synthetic faecal sludges (FS-1 and FS-2) with municipal synthetic wastewater (WW) was evaluated in an aerobic granular sludge (AGS) reactor. After characterisation, FS-1 showed the following concentrations, representative for medium-strength FS: 12,180 mg TSS L-1, 24,300 mg total COD L-1, 93.8 mg PO3-P L-1, and 325 mg NH4-N L-1. The NO3-N concentration was relatively high (300 mg L-1). For FS-2, the main difference with FS-1 was a lower nitrate concentration (18 mg L-1). The recipes were added consecutively, together with the WW, to an AGS reactor. In the case of FS-1, the system was fed with 7.2 kg total COD m-3d-1 and 0.5 kg Nitrogen m-3d-1. Undesired denitrification occurred during feeding and settling resulting in floating sludge and wash-out. In the case of FS-2, the system was fed with 8.0 kg total COD m-3d-1 and 0.3 kg Nitrogen m-3d-1. The lower NO3-N concentration in FS-2 resulted in less floating sludge, a more stabilised granular bed and better effluent concentrations. To enhance the hydrolysis of the slowly biodegradable particulates from the synthetic FS, an anaerobic stand-by period was added and the aeration period was increased. Overall, when compared to a control AGS reactor, a lower COD consumption (from 87 to 35 mg g-1 VSS h-1), P-uptake rates (from 6.0 to 2.0 mg P g VSS-1 h-1) and NH4-N removal (from 2.5 to 1.4 mg NH4-N g VSS-1 h-1) were registered after introducing the synthetic FS. Approximately 40% of the granular bed became flocculent at the end of the study, and a reduction of the granular size accompanied by higher solids accumulation in the reactor was observed. A considerable protozoa Vorticella spp. bloom attached to the granules and the accumulated particles occurred; potentially contributing to the removal of the suspended solids which were part of the FS recipe.


Assuntos
Esgotos , Águas Residuárias , Reatores Biológicos , Nitrogênio , Eliminação de Resíduos Líquidos
16.
Sci Total Environ ; 741: 140451, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32886973

RESUMO

The present study aimed to determine the spatial and temporal variations in trophic state and identify potential causes for these variations in 60 Korean reservoirs. Empirical models were developed using the relations of nutrients (total phosphorus, TP, and total nitrogen, TN) with chlorophyll-a (CHL-a) for efficient lake managements. The empirical models indicated that TP was the key regulating factor for algal growth in agricultural (R2 = 0.69) and power generation (R2 = 0.50) reservoirs. The CHL-a:TP and TN:TP ratios, indicators of phosphorus limitation, were used to validate the phosphorus reduction approach. The mean CHL-a:TP ratio of agricultural reservoirs was 0.60, indicating that algal chlorophyll is potentially limited by TP than any other factors. Agricultural, multipurpose, and power generation reservoirs, based on the N:P ratios, were more P- limited systems than natural lakes and estuarine reservoirs. The trophic state index (TSI) of Korean reservoirs varied between mesotrophy to hypereutrophy based on values of TSI (TP), TSI (CHL-a), and TSI (SD). Agricultural reservoirs were hypereutrophic using the criteria of TSI (CHL-a) and blue-green algae dominated the algal community. Analysis of trophic state index deviation (TSID) indicated that agricultural reservoirs were primarily P limited and other factors had minor effect. In contrast, the trophic status of estuarine and power generation reservoirs and natural lakes was largely modified by non-algal turbidity. Our outcomes may be effectively used for Korean lakes and reservoirs management.


Assuntos
Monitoramento Ambiental , Eutrofização , China , Clorofila/análise , Lagos , Nitrogênio/análise , Nutrientes , Fósforo/análise , República da Coreia
17.
Sci Total Environ ; 741: 140494, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32886976

RESUMO

Here, we examined the effects of low and high concentrations of perfluorooctanesulfonate (PFOS) on rhizosphere soil N cycling processes in the presence of Lythrum salicaria and Phragmites communis over 4 months. Compared with the control group, the nitrate nitrogen (NO3--N) content of the bulk soil in the low PFOS (0.1 mg kg-1) treatment significantly decreased (27.7%), the ammonium nitrogen (NH4+-N) content significantly increased (8.7%), and the pH value and total organic carbon (TOC) content slightly increased (0.3% and 1.1%, respectively). Compared with the low PFOS treatment, the content of NO3-N, NH4+-N and pH value in the bulk soil of the high PFOS treatment (50 mg kg-1) significantly increased (1.0%, 53.8% and 61.8%, respectively), and the TOC content significantly decreased (8.2%). Soil protease levels were high in the low PFOS treatment, but low in the high PFOS treatment. PFOS produced inverted U-shaped responses in the potential nitrification (1.5, 3.0, and 1.1 mg N d-1 kg-1 in no, low, and high PFOS, respectively), denitrification (0.19, 0.30, and 0.22 mg N d-1 kg-1 in no, low, and high PFOS, respectively), and N2O emission rates (0.01, 0.03, and 0.02 mg N d-1 kg-1 in no, low, and high PFOS, respectively) of bulk soil. The abundance of the archaea amoA gene decreased with increasing PFOS concentration, whereas that of bacterial amoA increased; inverted U-shaped responses were observed for narG, nirK, nirS, and nosZ. In the PFOS-contaminated rhizosphere soil, the observed changes differed from those in the bulk soil and differed between treatments. P. communis tended to upregulate each step of the nitrogen cycle under low PFOS conditions, whereas L. salicaria tended to inhibit them. Under high PFOS conditions, both test plants tended to act as inhibitors of the soil N-cycle; thus, the effects of PFOS on soil N transformation were plant-specific.


Assuntos
Rizosfera , Solo , Ácidos Alcanossulfônicos , Desnitrificação , Fluorcarbonetos , Nitrificação , Nitrogênio/análise , Ciclo do Nitrogênio , Microbiologia do Solo
18.
Sci Total Environ ; 741: 140488, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32887004

RESUMO

Nitrogen fertilization significantly increases greenhouse gases (GHGs) emission, when applied from inorganic or organic sources. Minimizing GHGs from agroecosystems without compromising crop yield for stabilization of green production systems remains a challenge. Being an integral component of wheat production technology, the nitrogen (N) application deems to be indispensable. Thus, to reduce the application of N fertilizer and keep in view the minimization of GHGs emission, without compromising soil fertility and wheat production, field experiments were performed with treatments included maize straw mulch (S1: 0, S2: 4500, S3: 9000 kg ha-1) and nitrogen fertilizer (N1: 0, N2: 192 and N3: 240 kg ha-1) during 2015-17. Results showed that the cumulative CO2 and N2O emission from 9000 kg ha-1 of maize straw mulch with 192 kg N ha-1 (S3N2) significantly decreased by 0.67% and 33.7%, respectively, averaged over two years compared with that of 9000 kg ha-1 of maize straw mulch with 240 kg N ha-1 (S3N3). Likewise, the average soil moisture content significantly increased by 10% and 10.6% for S3N2 and S3N3 treatments at 0-10 cm soil depth, respectively, compared to S1N1. Similarly, the S3N2 and S3N3 treatments had lowered the soil temperature by 0.2 and 0.1 °C, respectively, over S1N1 in wheat grown fields. The grain yield of wheat was increased by 45% and 45% under S3N3 and S3N2 treatments than S1N1, respectively. The S3N2 treatment was more economical than S3N3 for wheat crop. Therefore, maize straw mulch (S3) combined with 20% less N fertilizer (N2) from commercial source were considered as a viable production technology to improve crop yield, and reduce soil CO2 and N2O emissions.


Assuntos
Fertilizantes/análise , Triticum , Agricultura , Dióxido de Carbono , China , Nitrogênio/análise , Óxido Nitroso/análise , Solo , Zea mays
19.
Water Sci Technol ; 82(1): 107-119, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32910796

RESUMO

Dissolved organic matter (DOM) has an important impact on the water treatment and reuse of petroleum refinery wastewater. In order to improve the treatment efficiency, it is necessary to understand the chemical composition of the DOM in the treatment processes. In this paper, the molecular composition of DOM in wastewater samples from a representative refinery were characterized. The transformation of various compounds along the wastewater treatment processes was investigated. A total of 61 heteroatomic class species were detected from the DOM extracts, in which CHO (molecules composed of carbon, hydrogen, and oxygen atoms) and CHOS (CHO molecules that also contained sulfur) class species were the most abundant and account for 78.43% in relative mass peak abundance. The solid phase extraction DOM from the dichloromethane unextractable fraction exhibited a more complex molecular composition and contained more oxygen atoms than in the dichloromethane extract. During wastewater treatment processes, the chemical oxygen demand (COD) and ammonia-nitrogen were reduced by more than 90%. Volatile organic compounds (VOCs) accounted for about 30% of the total COD, in which benzene and toluene were dominant. After biochemical treatment, the VOCs were effectively removed but the molecular diversity of the DOM was increased and new compounds were generated. Sulfur-containing class species were more recalcitrant to biodegradation, so the origin and transformation of these compounds should be the subject of further research.


Assuntos
Águas Residuárias , Purificação da Água , Biodegradação Ambiental , Carbono , Nitrogênio
20.
Water Sci Technol ; 82(1): 157-169, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32910800

RESUMO

The dynamic characteristics of N2O emissions and nitrogen transformation in a sequencing batch biofilm reactor (SBBR) using the completely autotrophic nitrogen removal over nitrite (CANON) process coupled with denitrification were investigated via 15N isotope tracing and thermodynamic analysis. The results indicate that the Gibbs free energy (ΔG) values of N2O production by the nitrifier denitrification and heterotrophic denitrification reactions were greater than that of NH2OH oxidation, indicating that N2O was easier to produce via either nitrifier and heterotrophic denitrification than via NH2OH oxidation. Ammonia-oxidizing bacteria (AOB) denitrification exhibited a higher fs0 (the fraction of electron-donor electrons utilized for cell synthesis) than NH2OH oxidation. Therefore, AOB preferred the denitrification pathway because of its growth advantage when N2O was produced by the AOB. The N2O emissions by hydroxylamine oxidation, AOB denitrification and heterotrophic denitrification in the SBBRs using different C/N ratios account for 5.4-7.6%, 45.2-60.8% and 33.8-47.2% of the N2O produced, respectively. The total N2O emission with C/N ratios of 0, 0.67 and 1 was 228.04, 205.57 and 190.4 µg N2O-N·g-1VSS, respectively. The certain carbon sources aid in the reduction of N2O emissions in the process.


Assuntos
Nitritos , Óxido Nitroso , Desnitrificação , Nitrogênio , Termodinâmica
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