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1.
Water Sci Technol ; 82(5): 843-850, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33031064

RESUMO

Qualitative and quantitative analysis of trace organics in the condensate and its correlation with chemical oxygen demand (COD) is the key to the research on the reuse technology of condensate (condensate) from natural gas to hydrogen production process. The contents of anions, COD, total organic carbon (TOC) and total nitrogen (TN) were measured by ion chromatography and the TOC analyzer. Trace organics in the condensate and its correlation with COD was investigated in this paper. Results show that the contents of COD and TOC is 74.1 and 17.81 mg/L, respectively, and the anions in the condensate are mainly Cl-, I-, and SO42-, etc. The condensate mainly contains small molecule organics including methanol, ethanol and formic acid with the content of 41.4, 2.1 and 3.2 mg/L, respectively. The spiked recovery of methanol, ethanol and formic acid is 96.1%, 100.2% and 103.9% by high performance liquid chromatography (HPLC) and gas chromatography (GC), respectively. Methanol is the main source of COD in the condensate, and the contribution rate reaches up to 83.8%. The removal of trace methanol can significantly reduce the COD of the condensate. This work might provide basic data for reasonable recovery and utilization of condensate in the hydrogen production process.


Assuntos
Gás Natural , Poluentes Químicos da Água , Análise da Demanda Biológica de Oxigênio , Hidrogênio , Nitrogênio , Poluentes Químicos da Água/análise
2.
Water Sci Technol ; 82(5): 927-939, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33031071

RESUMO

UV/Vis spectrometers are powerful tools for online monitoring of wastewater constituents and processes. However, most studies only focus on typical parameters such as chemical oxygen demand (COD) and total suspended solids. This work presents a multi-parameter approach for calibration of a UV/Vis spectrometer for online monitoring of sewer systems. Parameters studied include soluble and total COD, nitrate, ammonium, sulphate and orthophosphate, as well as total dissolved sulphide, bisulphide and hydrogen sulphide, because they are one of the main causes for odour and corrosion in sewer systems. Two calibration methods are compared: multiple linear regression included in the manufacturer's software, and partial least square (PLS) computed using the pls package of the R library. Performance of the methods is evaluated for calibration and validation data sets employing four different criteria: relative root mean square error (RMSErel), RMSE-observations standard deviation ratio, Nash-Sutcliffe efficiency and percentage bias. A method-parameter dependency was revealed during the calibration phase but, when predicting new data, the PLS method showed higher robustness for almost all parameters. Both methods were able to predict concentration trends associated with sewer processes, some of which are strongly correlated to the sulphide species.


Assuntos
Águas Residuárias , Análise da Demanda Biológica de Oxigênio , Calibragem , Análise dos Mínimos Quadrados , Espectrofotometria Ultravioleta
3.
Water Sci Technol ; 82(6): 1184-1192, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055408

RESUMO

The influence of CO2 addition and hydraulic retention time (5 and 7 days) on removal of Pseudomonas aeruginosa, Clostridium perfringens, Staphylococcus sp., Enterococcus sp., and Escherichia coli was evaluated in a system with three parallel 21 L high rate algal ponds. Both the addition of CO2 and an increase in HRT had no significant influence on bacterial removal, but bacterial removal was higher than found in previous studies. The removal was 3.4-3.8, 2.5-3.7, 2.6-3.1, 2.2-2.6 and 1.3-1.7 units log for P. aeruginosa, E. coli, Enterococcus sp., C. perfringens, and for Staphylococcus sp., respectively. Although CO2 addition did not increase disinfection, it did significantly increase biomass productivity (by ≈60%) and settleability (by ≈350%). Additionally, even at the lower 5-day hydraulic retention time, CO2 addition improves removal of chemical oxygen demand (COD), total organic carbon (TOC), total organic nitrogen and phosphorus by 97, 91, 12 and 50%, respectively.


Assuntos
Dióxido de Carbono , Eliminação de Resíduos Líquidos , Análise da Demanda Biológica de Oxigênio , Escherichia coli , Nitrogênio
4.
Water Sci Technol ; 82(2): 273-280, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941169

RESUMO

The objective of this study is to explore the optimal pre-treatment procedures and statistics methods for live/dead bacterial staining using nitrite oxidizing organism (NOO) as the research aim. This staining method was developed and widely utilized to evaluate activated bacterial survival situation, because it is direct and convenience to count live and dead bacteria amount by colour distinguishes (green/red) from pictures taken by microscope. The living cell (green colour) percentage and initial bacterial chemical oxygen demand (COD) could be used for accurate reaction rate calculation at the beginning of tests. While according to the physiological principles, the detection target was limited as the organism has a complete cell shape, that was applicable for the initial phase for decay stage (live cell → particulate dead cell), but it is impossible to evaluate the decayed soluble COD from particulate dead cell during whole reaction. To model the decay stage scientifically, a two-step decay model was developed to cater to the live/dead bacterial staining analysis of biological nitrite oxidizer under inhibition condition of high nitrite concentrations at 35 °C. As results of optimal pre-treatment, a three level ultrasonic wave with 45 seconds was explored, as a reasonable observed picture number, 30 sets with 95% confident interval for datasets statistics was summarized. A set of nitrite oxidizer inhibition test (total COD and oxygen uptake rates) under high nitrite concentrations was simulated using the above model and obtained experimental schemes. Additionally, the disintegration enhancement from particulate dead cell to soluble COD by nitrite was inspected and modelled on the basis of experimental datasets.


Assuntos
Nitritos , Esgotos , Bactérias , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Oxirredução
5.
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
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.
Bioresour Technol ; 317: 124049, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32871330

RESUMO

Using vertical flow constructed wetlands (VFCWs) with different influent wastewater volumes and feeding modes, this study aimed to identify the optimal operation strategy for dry seasons under wastewater deficiency. Using half the influent wastewater volume (HIWV) did not necessarily improve the removal efficiency (RE) of the chemical oxygen demand (COD), NH4+-N, NO3--N and total nitrogen. In the HIWV treatments, intermittent resting did not result in significantly different pollutant REs, whereas strategies involving partial saturation and prolongation of the hydraulic retention time (HRT) slightly decreased the pollutant REs compared with those obtained in the constant feeding mode. Of the three HIWV strategies, the intermittent resting mode achieved the highest anaerobic ammoxidation, the dominant pathway for nitrogen removal in the systems, and thus stimulated nitrogen transformation. The intermittent resting mode forms part of the recommended operation strategy for VFCWs in dry seasons with wastewater deficiency.


Assuntos
Águas Residuárias , Áreas Alagadas , Análise da Demanda Biológica de Oxigênio , Desnitrificação , Nitrogênio/análise , Estações do Ano , Eliminação de Resíduos Líquidos
8.
Ecotoxicol Environ Saf ; 202: 110939, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32800222

RESUMO

Pulp and paper mill wastewater (PPMWW) contains high concentrations of recalcitrant compounds that cause toxicity to organisms. Advanced oxidation processes (AOPs) have the ability to degrade these compounds and reduce overall toxicity. Physicochemical characterization and Lactuca sativa toxicity test were conducted to compare the effectiveness of two post-treatments: UV/H2O2 and photo-Fenton. A comparison of four phytotoxicity indexes was carried out. PPMWW from a Brazilian treatment plant was characterized by high values of phenols, color, integrated spectral area (ISA), and chemical oxygen demand (COD), and caused significant inhibition to seedling development. The use of both post-treatments allowed the removal of over 75% of phenols, color, ISA, and COD. Although UV/H2O2 was more effective in removing phenols and ISA, photo-Fenton better reduced phytotoxicity. The most sensitive phytotoxicity indexes were RGIC0.8 and GIC80%, whereas SGC0, REC-0.25 and REC-0.50 better showed the effectiveness of the post-treatments. We suggest the combined use of two phytotoxicity indexes: one that evaluates the effects on seed germination and, another, on root elongation, e.g., SGC0 and RGIC0.8. Additionally, we recommend the use of ISA for monitoring programs of wastewater treatments because it is a cost-effective approach that allows narrowing down the search and identification of compounds present in complex mixtures.


Assuntos
Papel , Fenóis/toxicidade , Eliminação de Resíduos Líquidos/métodos , Análise da Demanda Biológica de Oxigênio , Brasil , Cor , Corantes/toxicidade , Peróxido de Hidrogênio/química , Resíduos Industriais/análise , Oxirredução , Fenóis/análise , Plantas/efeitos dos fármacos , Águas Residuárias/química
9.
Water Sci Technol ; 81(11): 2432-2440, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32784286

RESUMO

By providing the key carbon and nitrogen elements needed for eutrophication, the potential toxicity of ethylenediaminetetraacetic acid (EDTA) prompts the exploration of effective treatment methods to minimize the amount of EDTA released into the environment. In this study, Fe3O4 magnetic nanoparticles (MNPs) were prepared and used as catalysts to study the mineralization of EDTA in Fenton-like reactions under neutral pH. Fe3O4 MNPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET). The effects of pH, ferric ion leaching, and H2O2 concentration on chemical oxygen demand (COD) removal of EDTA were investigated. The morphological characterization of the nanoparticles suggests a quasi-spherical structure with small particle size and a surface area of 49.9 m2/g. The results show that Fe3O4 MNPs had good catalytic activity for the mineralization of EDTA under pH 5.0-9.0. The optimum conditions for the COD removal of 45% at pH 7.0 were: 40 mM H2O2, 10 mM Fe3O4, and 1 g/L EDTANa2·2H2O at 303 K. Fe3O4 MNPs maintained high catalytic activity after five cycles of continuous degradation of EDTA. According to reactive oxidizing species measurements obtained by electron spin resonance (ESR), it was confirmed that HO· free radicals, presented in the H2O2/Fe3O4 MNPs heterogeneous Fenton-like reaction, were the primary active group in the removal of EDTA. These features can be considered beneficial to the application of Fe3O4 MNPs towards industrial wastewater treatment.


Assuntos
Peróxido de Hidrogênio , Poluentes Químicos da Água/análise , Análise da Demanda Biológica de Oxigênio , Catálise , Ácido Edético , Concentração de Íons de Hidrogênio
10.
Water Sci Technol ; 81(11): 2459-2470, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32784289

RESUMO

This study investigated the removal of chemical oxygen demand (COD), NH4-N, and perfluorinated compounds (PFCs) in the effluent from a wastewater treatment plant (WWTP) using ZnO coated activated carbon (ZnO/AC). Results suggested that the optimal dosage of the ZnO/AC was 0.8 g/L within 240 min of contact time, at which the maximum removal efficiency of COD was approximately 86.8%, while the removal efficiencies of PFOA and PFOS reached 86.5% and 82.1%. In comparison, the removal efficiencies of NH4-N, PFBA, and PFBS were lower, at approximately 47.9%, 44.0%, and 55.4%, respectively. In addition, COD was preferentially adsorbed before PFCs and NH4-N, when the contact time ranged from 0 to 180 min, and the order of PFCs removal showed a positive correlation with C-F chain length. The kinetic study revealed that the removal of COD, NH4-N, and PFCs could be better depicted and predicted by the Lagergren quasi-second order dynamic model with high correlation coefficients, which involved liquid membrane diffusion, intraparticle diffusion, and photocatalytic reactions. The saturated ZnO/AC was finally regenerated using ultrasound for 3 h and retained excellent performance, which proved it could be considered as an effective and alternative technology.


Assuntos
Poluentes Químicos da Água , Óxido de Zinco , Análise da Demanda Biológica de Oxigênio , Carvão Vegetal , Eliminação de Resíduos Líquidos , Águas Residuárias
11.
J Environ Manage ; 272: 111115, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32738758

RESUMO

Aerobic granular sludge (AGS) is a type of biofilm with good sedimentation and density, high biomass, high organic load tolerance and toxicity resistance. Oxytetracycline (OTC) is an antibiotic widely used in livestock and aquaculture, and its low absorption and high residue bring many risks and harms to the ecological environment. In this study, an OTC-degrading strain TJ3 was isolated from AGS and identified as Pandoraea sp. The biodegradation characteristics of OTC by strain TJ3 under different environmental conditions were also investigated. The results showed that the optimal initial pH value and temperature for the culture strain were 6.0 and 30 °C, respectively. At an inoculation dose of 6% (v/v), the removal rate of OTC by strain TJ3 was remarkable (59.4%). Furthermore, when the sodium acetate was present as an additional substrate, the biomass and the OTC removal rate of strain TJ3 were improved. The biodegradability of strain TJ3 to OTC was proved by LC-QTOF/MS, and two possible biotransformation products, i.e. m/z 416 and 219, were identified. In the bioaugmentation experiments of AGS by strain TJ3, the average OTC removal rate was 92.89% after the stable operation of bioreactor. The chemical oxygen demand (COD), ammonium nitrogen (NH4+-N) and total phosphorus (TP) were efficiently removed. The microbial community structure had significantly changed at the genus level, and the relative abundance of Zoogloea, Pandoraea, Cloacibacterium and Desulfovibrio increased evidently. These results implied that the OTC removal performance and the structural stability of AGS were improved. In this study, Pandoraea sp. TJ3 was applied to removal OTC for the first time, and results showed that Pandoraea sp. TJ3 may be a new auxiliary bacterial resource for the biodegradation of OTC and a potential candidate in the treatment of antibiotic wastewater.


Assuntos
Oxitetraciclina , Esgotos , Aerobiose , Bactérias , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Nitrogênio , Eliminação de Resíduos Líquidos
12.
Water Sci Technol ; 81(12): 2488-2500, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32857737

RESUMO

This paper offers a feasible solution for the treatment of membrane concentrate produced from the textile industry, using the Fenton, Advanced Fenton (AF), ozonation and hydrodynamic cavitation (HC) and combination of these processes. The study investigated the optimum oxidant and catalyst concentrations, optimum operational conditions and comparison of these processes. The potential formation of chlorinated organic compounds after oxidation of membrane concentrate was also investigated by analyzing total organic halogen (TOX) and polychlorinated biphenyl (PCBs). Also, toxicity analysis was performed with Vibrio fischeri photobacteria to identify the production possibility of oxidation intermediates that are more toxic and difficult to treat than the targeted contaminants. Maximum removal efficiencies in chemical oxygen demand (COD) and color were 18.8% and 60.7% respectively using HC alone at a cavitation number (CN) of 0.1. Maximum COD, total organic carbon (TOC), and color removal efficiency at molar concentrations of 175 mM H2O2 and 35 mM Fe2+ and pH 3 after 30 min was 87.1, 80.8 and 99%. Combined HC with Fenton showed the highest removal efficiency in terms of COD, TOC, and color. It was also stated that the use of high oxidant concentrations masks the synergistic effect of HC on Fenton processes due to the scavenging effect.


Assuntos
Peróxido de Hidrogênio , Poluentes Químicos da Água , Análise da Demanda Biológica de Oxigênio , Oxirredução , Indústria Têxtil
13.
Water Sci Technol ; 81(12): 2650-2663, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32857750

RESUMO

The effects of different operating parameters on the treatment efficiency of oily wastewater in terms of biological oxygen demand (BOD) and chemical oxygen demand (COD) were measured. The analyses of BOD using OxiTop biosensors are reviewed regarding performance characteristics like linearity, response time, precision, agreement between BOD28 values obtained from the biosensors and the ultimate BOD (UBOD), as well as toxic resistance and COD. The wastewater samples were seeded with the bacteria, which were isolated in the current study from Kuwaiti oil-contaminated sand, such as Bacillus mycoidesis and Bacillus subtilis. After 18 days, the margin for saponin solution and oily wastewater using either Rhododcoccus (R), a mixture of Bacillus mycoidesis and Bacillus subtilis (M) or a mixture of R&M exhibited the maximum rate of BOD. It was found that the corresponding COD of the saponin solution (SS) ranged from 1,525 mg/l to 3,890 mg/l by distilled water and the mixture (RM), respectively. The COD of oily wastewater (WW) ranged from 2,900 mg/l to 4,450 mg/l by distilled water and the mixture of (RM), respectively. Moreover, the higher values of BOD28 were recorded when mixtures of bacteria were added together with the saponin solution or oily wastewaters. Furthermore, the average values of UBOD for the oily wastewater with RM or with amendment substance were increased by about 33.5% and 49.5%, respectively. However, BOD28/COD ratios for all the selected have been found to be less than 0.4, indicating low aerobic degradability.


Assuntos
Bacillus , Águas Residuárias , Análise da Demanda Biológica de Oxigênio , Hidrocarbonetos , Óleos , Eliminação de Resíduos Líquidos
14.
Environ Pollut ; 266(Pt 3): 115417, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32823067

RESUMO

The Sürgü Stream, located in the Euphrates River basin of Turkey, is used for drinking water source, agricultural irrigation and rainbow trout production. Therefore, water quality of the stream is of great importance. In this study, multivariate statistical techniques (MSTs) and water quality index (WQI) were applied to assess water quality of the stream affected by multiple stressors such as untreated domestic sewage, effluents from fish farms, agricultural runoff and streambank erosion. For this, 16 water quality parameters at five sites along the stream were monitored monthly during one year. Most of parameters showed significant spatial variations, indicating the influence of anthropogenic activities. All parameters except TN (total nitrogen) showed significant seasonal differences due to high seasonality in WT (water temperature) and water flow. The spatial variations in the WQI were significant (p < 0.05) and the mean WQI values ranged from 87.6 to 95.3, indicating "good" to "excellent" water quality in the stream. Cluster analysis classified five sites into three groups, that is, clean region, low polluted region and very clean region. Stepwise temporal discriminant analysis (DA) identified that pH, WT, Cl-, SO42-, COD (chemical oxygen demand), TSS (total suspended solids) and Ca2+ are the parameters responsible for variations between seasons, and stepwise spatial DA identified that DO (dissolved oxygen), EC (electrical conductivity), NH4-N, TN (total nitrogen) and TSS are the parameters responsible for variations between the regions. Principal component analysis/factor analysis revealed that the parameters responsible for water quality variations were mainly associated with suspended solids (both natural and anthropogenic), soluble salts (natural) and nutrients and organic matter (anthropogenic).


Assuntos
Poluentes Químicos da Água/análise , Qualidade da Água , Análise da Demanda Biológica de Oxigênio , Monitoramento Ambiental , Rios , Turquia
15.
Environ Pollut ; 266(Pt 2): 115373, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32827985

RESUMO

Effective utilization of harmful algal biomass from eutrophic lakes is required for sustainable waste management and circular bioeconomy. In this study, Microcystis aeruginosa derived biomass served as an electron donor in the microbial fuel cell (MFC) for waste treatment and electricity generation. Bioelectrochemical performance of MFC fed with microalgae (MFC-Algae) was compared with MFC fed with a commercial substrate (MFC-Acetate). Complete removal of microcystin-LR (MC-LR) and high chemical oxygen demand (COD) removal efficiency (67.5 ± 1%) in MFC-Algae showed that harmful algal biomass could be converted into bioelectricity. Polarization curves revealed that MFC-Algae delivered the maximum power density (83 mW/m2) and current density (672 mA/m2), which was 43% and 45% higher than that of MFC-Acetate respectively. Improved electrochemical performance and substantial coulombic efficiency (7.6%) also verified the potential use of harmful algal biomass as an alternate MFC substrate. Diverse microbial community profiles showed the substrate-dependent electrogenic activities in each MFC. Biodegradation pathway of MC-LR by anodic microbes was also explored in detail. Briefly, a sustainable approach for on-site waste management of harmful algal biomass was presented, which was deprived of transportation and special pretreatments. It is anticipated that current findings will help to pave the way for practical applications of MFC technology.


Assuntos
Fontes de Energia Bioelétrica , Gerenciamento de Resíduos , Análise da Demanda Biológica de Oxigênio , Biomassa , Eletricidade , Eletrodos , Águas Residuárias
16.
Chemosphere ; 260: 127600, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32758769

RESUMO

Granules initiation and development is the backbone of aerobic granular sludge technology. Feed composition can notably affect initiation and development of aerobic granules, and yield aerobic granules with distinct microbial community, morphology and structure. This paper reports an unexpected formation of aerobic granules in an aspartic acid fed SBR under unfavorable hydrodynamic selection conditions. Detailed characteristics of these aerobic granules were investigated in terms of morphology, structure, bioactivity and EPS. The results showed that due to the absence of favorable hydrodynamic selection pressure, the formed aerobic granules had an irregular shape with a rough outline and loose internal structure, which was quite different from mature aerobic granules. Bacteria in these aerobic granules were mainly presented in the form of microcolony with calcium and ß-polysaccharides responsible for its mechanical stability. The high N/C ratio of aspartic acid enabled the enrichment of significant amount of nitrifiers within aerobic granules and thus resulted in high nitrification activity of these aerobic granules. The negatively charged and hydrophilic aspartic acid also induced the bacteria to secrete more exopolysaccharides for contributing to more neutral and hydrophilic surface of the aerobic granules, which was beneficial for aspartic acid capture. As a result, polysaccharides, rather than proteins, became the major components of EPS in these aerobic granules. This paper provides us a foundation to better understand the granulation potential of proteinaceous substrates that is frequently encountered in industrial wastewaters.


Assuntos
Ácido Aspártico/química , Reatores Biológicos/microbiologia , Esgotos/microbiologia , Purificação da Água/métodos , Aerobiose , Análise da Demanda Biológica de Oxigênio , China , Matriz Extracelular de Substâncias Poliméricas/química , Hidrodinâmica , Microbiota , Modelos Teóricos , Nitrificação , Proteobactérias/isolamento & purificação , Esgotos/química , Propriedades de Superfície , Águas Residuárias/química
17.
Water Sci Technol ; 81(9): 1914-1926, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32666945

RESUMO

Membrane bioreactor (MBR) has been proven to be an efficient technology capable of treating various industrial effluents. However, the evaluation of its performances in the case of olive mill wastewater (OMW) over a conventional activated sludge (CAS) have not been determined yet. The present study aims to compare OMW treatment in two laboratory scale pilots: an external ceramic MBR and CAS starting with an acclimation step in both reactors by raising OMW concentration progressively. After the acclimation step, the reactors received OMW at 2 gCOD/L with respect to an organic loading rate of 0.2 and 0.3 kgCOD/kgMLVSS/d for MBR and CAS, respectively. Biomass acclimation occurred successfully in both systems; however, the MBR tolerated more OMW toxicity than CAS as the MBR always maintained an effluent with a better quality. At a stable state, a higher reduction of 95% chemical oxygen demand (COD) was obtained with MBR compared to CAS (86%), but both succeeded in polyphenols removal (80%). Moreover, a higher MLSS elimination from the MBR treated water (97%) was measured against 88% for CAS. Therefore, CAS was suitable for OMW treatment and MBR could be proposed as an alternative to CAS when a better quality of treated water is required.


Assuntos
Olea , Águas Residuárias , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Resíduos Industriais , Esgotos , Eliminação de Resíduos Líquidos
18.
Water Sci Technol ; 81(9): 1972-1982, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32666950

RESUMO

This study evaluated the effects of temporary external voltage on the performance of two-chambered microbial fuel cells (MFC) that use nitrate wastewater as a substrate. Results indicate that the external voltage affected the performance of the MFC during their operation, and this effect remained even after the voltage was removed. The degradation efficiency of the chemical oxygen demand increased in the MFC under external voltages of 0.5, 0.8, and 1.1 V, and the optimal applied voltage was 1.1 V. Compared with the control group without external voltages, the MFC under a voltage of 1.1 V achieved higher current densities and efficiency of nitrate removal during their operation. The MFC with an applied voltage of 1.1 V also achieved the highest maximum power density of 2,035.08 mW/m3. The applied voltages of 0.5 and 0.8 V exerted a positive effect on the performance of the MFC. High-throughput sequencing was used to explore the anode and cathode biofilms. Results showed that the influence was highly associated with microbial community in bio-anode. The predominant functional family changed from Methanotrichaceae during start-up to Flavobacteriaceae in a steady phase.


Assuntos
Fontes de Energia Bioelétrica , Biofilmes , Análise da Demanda Biológica de Oxigênio , Eletricidade , Eletrodos , Águas Residuárias
19.
Water Sci Technol ; 81(9): 2011-2022, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32666954

RESUMO

Chemical pollution poses a threat to the aquatic environment and to human health. Wastewater treatment plants are the last defensive line between the aquatic environment and emissions of pollutants. This study focuses on identification of most relevant hazardous substances in Estonian municipal wastewater and their fate in the treatment process. During this study, seasonal wastewater and sewage sludge samples were collected from nine municipal wastewater treatment plants and analyzed for 282 hazardous substances, including EU (n = 45) and Estonian (n = 31) priority substances. Results of this study show that several substances that are subject to international restrictions (e.g. Stockholm Convention) are still present in untreated sewage. Wastewater treatment systems that had a greater level of complexity (TEC >5) were more successful in removing hazardous substances. Statistical analyses showed that removal efficiency of organic hazardous substances had significant (p-value <0.05) linear correlation with removal efficiencies of chemical oxygen demand (COD) and total suspended solids (TSS), but a monotonic relationship with operators' competency. This study showed that operators' competency had a strong influence on the stability of the wastewater treatment efficiency and removal of organic hazardous substances.


Assuntos
Eliminação de Resíduos Líquidos , Águas Residuárias , Análise da Demanda Biológica de Oxigênio , Substâncias Perigosas , Esgotos
20.
Environ Monit Assess ; 192(8): 536, 2020 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-32696135

RESUMO

Water and energy are closely interlinked during their production and consumption processes. The limited and temporary distribution of energy and water resources poses a significant environmental challenge. Industrial wastewater treatment plants are essential elements of water production and also significant energy consumers. This study proposes a methodology for energy management of a wastewater treatment plant. Specifically, it examines the impact of optimum operating conditions on energy costs for a dairy wastewater treatment plant using a dissolved air flotation process. Monte Carlo simulation was used to optimize the parameters and to determine the reuse potential of dairy effluent. Firstly, the optimum operating conditions were determined. The results revealed a maximum fat, oil, and grease removal efficiency of 97% and a chemical oxygen demand removal efficiency of 70%. The optimum conditions were pH of 8, a saturation pressure of 5 bars, and a recirculation ratio of 33%. The optimum concentrations of coagulant and flocculant that contain polyaluminum chloride and cationic polymer were 20 mg/L and 25 mg/L, respectively. The results of the simulation study gave a recirculation ratio of 26.31%, a polyaluminum chloride concentration of 42.5 mg/L, a cationic polymer concentration of 36.31 mg/L, and a saturation pressure of 4.61 bars. Finally, energy cost assessment was performed using a newly developed model which showed that the energy cost indicator of the existing process was lower than optimum operating conditions. The reuse potential of dairy effluent as cooling water was found to be 52%.


Assuntos
Eliminação de Resíduos Líquidos , Águas Residuárias , Análise da Demanda Biológica de Oxigênio , Indústria de Laticínios , Monitoramento Ambiental
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