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1.
Sci Total Environ ; 704: 135259, 2020 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-31780174

RESUMO

The industrialization of integrated algae-aquaculture systems entails appropriate information regarding environmental and economic assessments, field and laboratory analyses, and feasibility studies. Accordingly, Scenedesmus obliquus was cultivated in a raceway pond (300 m3), and the algal biomass was used as a protein source for the growth of Nile tilapia (Oreochromis niloticus). Nile tilapia fish was cultivated in five commercial-scale tanks for 44 weeks, having a productivity of 15-20 kg (live weight)·m-3. Among various algal-based fish meals, the diet containing 7.5% microalgae provided the largest body length (29 cm) and weight (402 g), as well as the optimum growth performance parameters. Scenedesmus obliquus was subjected to lipid extraction, and the defatted biomass was also used as a substitute for fishmeal in diets. Nile tilapia grown using the lipid-extracted algae had improved health status, and the biochemical composition was satisfactory. Further, two scenarios were economically investigated: Case 1, the direct use of algal biomass for fish production, and Case 2, the utilization of algae for biodiesel production followed by the application of residual biomass in fishmeal diets. Based on field experiments and financial information reported in the literature, the two options would offset their initial investment cost within payback periods of 7.5 and 6.8 yr, respectively.

2.
Sci Total Environ ; 702: 134733, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31734609

RESUMO

To develop future wastewater treatment systems, focus is to improve/investigate existing biological wastewater treatment processes for the concurrent treatment of conventional pollution parameters (essentially nitrogen) and micro pollutants. Majority of the existing biological wastewater treatment systems were not designed for the removal of micro pollutants. This study focuses on understanding the role of treatment configuration for efficient removal of nitrogen and priority phthalic acid esters (PAEs) from real municipal wastewater in an integrated biofilm activated sludge (IBAS) system. The reactor was operated in two phases: Run I, without external carbon source in anoxic reactor and Run II, a nitrogen removal process, with partial diversion of untreated wastewater in anoxic reactor. Nitrogen removal was 70 ±â€¯12% in both operational phases, however, during Run I, removal of PAEs fluctuated with an average removal of 60-78%. Comparatively, removal of PAEs in Run II varied over a smaller range with average removal increased to 89-95%. In both operational scenarios, secondary oxic tank contributed maximum to the overall removal of PAEs in treatment system. Mass balance calculations showed significant contribution of biodegradation towards overall removal of PAEs which was enhanced by the supply of external carbon source. Kinetics and model output supported the PAEs removal performance observed in different reaction environments of IBAS process. A correlation between food to microorganism (F/M) ratio and PAEs removal showed increase in PAEs removal with decrease in F/M ratio. The study showed that treatment configuration and F/M ratio may be one of the guiding parameters for efficient removal of PAEs in biological wastewater treatment.


Assuntos
Ácidos Ftálicos , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água , Biodegradação Ambiental , Ésteres , Nitrogênio , Esgotos
3.
Environ Technol ; : 1-16, 2019 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-31162991

RESUMO

Anaerobic ammonium oxidation (anammox) presents an efficient alternative for conventional nitrogen removal process. In this study, the effect of varying Substrate (ammonium to nitrite) ratios on reactor performance and microbial community structures within three anaerobic sequencing batch reactors (ASBRs) was investigated. Three 1 L ASBRs (Reactors 1, 2 and 3) were operated under similar operational conditions. By varying the ammonium to nitrite ratios, a significant variation in nitrogen removal was observed after 170 days of operation: nitrogen removal efficiencies of 67.17 ± 7.29%, 57.13 ± 11.18% and 56.26 ± 17.05% in Reactors 3, 2 and 1 respectively were achieved. Similarly, using quantitative PCR, an overall variation in the population of anammox bacteria, ammonia oxidizing bacteria (AOB), Nitrospira and copy numbers of nirS, hzo and hzs genes were observed with varying degrees of expression. High throughput sequencing analysis further showed a shift in microbial community structure with an overall increase in population of Planctomycetia from 0.76% to (3%, 25% and 26%) and Betaproteobacteria from 5.38% to (19%, 21% and 43%) within Reactors 1, 2 and 3, respectively. In conclusion, different substrates ratio showed a significant influence on the overall nitrogen removal rate as well as the abundances of the different microbial groups.

4.
Chemosphere ; 234: 885-892, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31252360

RESUMO

Removal of emerging contaminants (ECs) is a serious concern in wastewater industry especially for public acceptance of reclaimed water. Diethylhexyl phthalate (DEHP) is one of the ubiquitous and detectable plasticizers in municipal wastewater across the globe. Water Framework Directive (2000/60/EC) has prioritized it for the establishment of discharge regulations. A cost-effective strategy, especially for developing nations, may be the re-engineering of the existing biological process for the simultaneous removal of ECs and conventional pollutants. Wastewater treatment plants are one of the main sources for DEHP occurrence in surface water. In this study, possible role of activated sludge process operational parameters in effective removal of DEHP was assessed. Principal component analysis of occurrence data showed dissimilarity with the organic and nutrient characteristics of sewage. DEHP concentration in more than half (55%) of treated wastewater samples was more than environmental quality standard value for inland and surface water bodies (1.3 µg/L). At a mixed liquor suspended solid (MLSS) concentration range of 3461-4972 mg/L, overall removal was 23.9 µg/gMLSS.d (92 ±â€¯6%) with biodegraded portion as 22.4 µg/gMLSS.d (85 ±â€¯4%) and sorbed portion of 1.5 µg/gMLSS.d (7 ±â€¯4%). DEHP removal showed an increasing trend at higher oxygen uptake rates (OUR) of sludge with DEHP removal of 8.1  µg DEHP/gMLSS.d (70 ±â€¯6%), in the OUR range of 20-28mgO2/L/h. Increase in overall removal of DEHP showed a positive correlation (r2 = 0.7) with increasing sludge retention time (SRT) and so does the decreasing food to microorganism (F/M) ratio with increasing removal of DEHP (r2 = 0.8). A temperature decrease of 13 °C caused a decrease of 30% in overall removal of DEHP.


Assuntos
Dietilexilftalato/isolamento & purificação , Esgotos/química , Biodegradação Ambiental , Dietilexilftalato/análise , Plastificantes/análise , Plastificantes/isolamento & purificação , Águas Residuárias/análise , Purificação da Água
5.
PLoS One ; 14(5): e0216040, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31083664

RESUMO

Wastewater from different sources is contaminated by protozoan parasites including Cryptosporidium and Giardia. Many protozoan parasites are becoming resistant to chemical treatment. The challenge of finding alternatives is presented to researchers by exploring other methods of eliminating protozoan parasites from wastewater. The aim of this study was to assess the speciation and the viability of Cryptosporidium and Giardia in environmental samples with the specific objective of evaluating if effluent chlorination and UV affect the viability. Different doses of chlorine with different exposure times were experimented with both distilled water and waste water spiked with (oo)cysts derived from environmental samples. UV irradiation at different doses was also experimented using the same spiked samples. Two methods of quantification and detection, namely, microscopy and flow cytometry, were used in the experiment. Two vital dyes, Syto-9+PI and DAPI+PI, were the used for staining the collected wastewater samples. It was found that the (oo)cysts responded to chlorination and UV treatments with Giardia responding better than Cryptosporidium. Giardia responded very well to UV irradiations with almost 0 percent remaining viable after a low dose of UV. Cryptosporidium was found to be resistant to chlorination even at high doses but responded well to high UV doses. DAPI+PI dye gave a lower mean percentage viability values than Syto-9+PI. Flow cytometry gave higher mean percentage than microscopy from the results. It is concluded that UV is a promising alternative to Chlorine in removing Cryptosporidium and Giardia from waste water. Appropriate treatment method for wastewater is necessary to minimize water resources pollution when wastewater is released into water systems.


Assuntos
Cloro/farmacologia , Cryptosporidium/efeitos dos fármacos , Giardia/efeitos dos fármacos , Águas Residuárias/parasitologia , Água/parasitologia , Corantes/farmacologia , Criptosporidiose/prevenção & controle , Giardíase/prevenção & controle , Oocistos/efeitos dos fármacos , Raios Ultravioleta , Poluição da Água
6.
Artigo em Inglês | MEDLINE | ID: mdl-30938573

RESUMO

A study was conducted to characterize the raw wastewater entering a modern cost effective municipal WWTP in Poland using two approaches; 1) a combination of modeling and carbonaceous oxygen demand (COD) fractionation using respirometric test coupled with model estimation (RT-ME) and 2) flocculation/filtration COD fractionation method combined with BOD measurements (FF-BOD). It was observed that the particulate fractions of COD obtained using FF-BOD method was higher than those estimated by RT-ME approach. Contrary to the above, the values of inert soluble fraction evaluated by FF-BOD method was significantly lower than RT-ME approach (2.4% and 3.9% respectively). Furthermore, the values for low colloidal and particulate fractions as well as soluble inert fractions were different than expected from a typical municipal wastewater. These observations suggest that even at low load (10% of the total wastewater treatment inflow), the industrial wastewater composition can significantly affect the characteristics of municipal wastewater which could also affect the performance and accuracy of respirometric tests. Therefore, in such cases, comparison of the respirometric tests with flocculation/filtration COD/BOD measurements are recommended. Oxygen uptake rate profile with settled wastewater and/or after coagulation-flocculation, however, could still be recommended as a "rapid" control method for monitoring/optimising modern cost-effective wastewater treatment plants.


Assuntos
Análise da Demanda Biológica de Oxigênio , Esgotos/química , Eliminação de Resíduos Líquidos/economia , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Análise da Demanda Biológica de Oxigênio/métodos , Análise da Demanda Biológica de Oxigênio/normas , Calibragem , Compostos Inorgânicos de Carbono/química , Fracionamento Químico/métodos , Cidades , Análise Custo-Benefício , Monitoramento Ambiental/métodos , Monitoramento Ambiental/normas , Filtração , Floculação , Humanos , Oxigênio/química , Polônia , Purificação da Água/economia , Purificação da Água/métodos , Purificação da Água/normas
7.
J Environ Manage ; 240: 293-302, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30953982

RESUMO

This study investigated the dual application of Scenedesmus obliquus for wastewater phycoremediation and biochemical component accumulation in microalgal cells. The microalgae grown in wastewater showed micro-elements uptake and removal efficiencies of 71.2 ±â€¯3.5% COD, 81.9 ±â€¯3.8% NH4+, ∼100.0% NO3-, and 94.1 ±â€¯4.7% PO43-. The growth profile of Scenedesmus obliquus indicated a specific growth rate of 0.42 ±â€¯0.02 1·d-1 and carrying capacity of 0.88 ±â€¯0.04 g L-1. The lipid, protein, and carbohydrate yields (w·w-1 of dry weight) were 26.5 ±â€¯1.5%, 28.5 ±â€¯1.5%, and 27.5 ±â€¯1.6%, respectively. The de-oiled biomass was subjected to biochemical extraction, achieving protein and carbohydrate yields of 25.3 ±â€¯1.4% and 21.4 ±â€¯1.2%, respectively. Fourier transform infrared spectroscopy showed several functional groups (e.g., NH, CH3, CH2, CO, CN, PO, and SiO) on the biomass surface, confirming the accumulation of biochemical elements in microalgae. The thermal analysis of microalgal biomass depicted sequential stages of dehydration (60-190 °C), devolatilization (200-490 °C), and solid residue decomposition (490-600 °C). The cost-benefit analysis of microalgae cultivated in wastewater was derived regarding amortization and operating costs and energy and environmental benefits. The net profit of phycoremediation was 16885 US$·y-1, resulting in a payback period of 14.8 years (i.e., shorter than the project lifetime). Accordingly, the proposed phycoremediation process was economically viable.


Assuntos
Microalgas , Scenedesmus , Biocombustíveis , Biomassa , Águas Residuárias
8.
Microbiol Res ; 211: 47-56, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29705205

RESUMO

A novel halotolerant species of cyanobacterium of the order Chroococcales was isolated from hypersaline estuary in Kwa-Zulu Natal, South Africa. A comprehensive polyphasic approach viz., cell morphology, pigment composition and complete genome sequence analysis was conducted to elucidate the taxonomic position of the isolated strain. The blue-green oval to rod-shaped cells were 14-18 µm in size, and contained a high amount of phycocyanin pigments. The strain was moderate thermotolerant/alkalitolerant halophile with the optimum conditions for growth at 35 °C, pH 8.5 and 120 g/l of NaCl. Based on 16S rRNA gene sequence phylogeny, the strain was related to members of the 'Euhalothece' subcluster (99%). The whole genome sequence was determined, and the annotated genes showed a 90% sequence similarity to the gas-vacuolate, spindle-shaped Dactylococcopsis salina PCC 8305. The size of the genome was determined to be 5,113,178 bp and contained 4332 protein-coding genes and 69 RNA genes with a G + C content of 46.7%. Genes encoding osmoregulation, oxidative stress, heat shock, persister cells, and UV-absorbing secondary metabolites, among others, were identified. Based on the phylogenetic analysis of the 16S rRNA gene sequences, physiological data, pigment compositions and genomic data, the strain is considered to represent a novel species of Euhalothece.


Assuntos
Cianobactérias/classificação , Cianobactérias/citologia , Cianobactérias/genética , Cianobactérias/isolamento & purificação , Genótipo , Fenótipo , Filogenia , Água do Mar/microbiologia , Técnicas de Tipagem Bacteriana , Composição de Bases , Biomassa , DNA Bacteriano/genética , DNA Bacteriano/isolamento & purificação , Genes Bacterianos/genética , Tamanho do Genoma , Proteínas de Choque Térmico/genética , Concentração de Íons de Hidrogênio , Osmorregulação/genética , Estresse Oxidativo/genética , Ficocianina/metabolismo , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Tolerância ao Sal , Análise de Sequência de DNA , Cloreto de Sódio/metabolismo , África do Sul , Especificidade da Espécie , Temperatura Ambiente , Sequenciamento Completo do Genoma
9.
Biotechnol Adv ; 36(4): 1255-1273, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29673972

RESUMO

Algae are a group of ubiquitous photosynthetic organisms comprising eukaryotic green algae and Gram-negative prokaryotic cyanobacteria, which have immense potential as a bioresource for various industries related to biofuels, pharmaceuticals, nutraceuticals and feed. This fascinating group of organisms also has applications in modern agriculture through facilitating increased nutrient availability, maintaining the organic carbon and fertility of soil, and enhancing plant growth and crop yields, as a result of stimulation of soil microbial activity. Several cyanobacteria provide nitrogen fertilization through biological nitrogen fixation and through enzymatic activities related to interconversions and mobilization of different forms of nitrogen. Both green algae and cyanobacteria are involved in the production of metabolites such as growth hormones, polysaccharides, antimicrobial compounds, etc., which play an important role in the colonization of plants and proliferation of microbial and eukaryotic communities in soil. Currently, the development of consortia of cyanobacteria with bacteria or fungi or microalgae or their biofilms has widened their scope of utilization. Development of integrated wastewater treatment and biomass production systems is an emerging technology, which exploits the nutrient sequestering potential of microalgae and its valorisation. This review focuses on prospects and challenges of application of microalgae in various areas of agriculture, including crop production, protection and natural resource management. An overview of the recent advances, novel technologies developed, their commercialization status and future directions are also included.


Assuntos
Agricultura/métodos , Biotecnologia/métodos , Cianobactérias , Microalgas , Biomassa , Fertilizantes , Purificação da Água
10.
Environ Monit Assess ; 190(3): 151, 2018 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-29460191

RESUMO

This study presented a comprehensive analysis of heavy metal contents in foodstuffs and the associated health risk for the residential population in Durban, South Africa. The concentrations of elements in fruits and vegetables, respectively, were (in mg kg-1 dry weight) Cu, 0.52-1.47 and 0.27-2.25; Zn, 0.30-3.05 and 0.56-6.24, Fe, 1.70-22.60 and 0.73-44.90; Mn, 0.37-28.50 and 0.67-13.70; Cr, 0.47-1.47 and 0.37-3.06; Ni 0.03-1.14 and 0.11-2.5;, and Pb, 1.52-3.45 and 1.57-4.52. Multivariate analysis revealed that pineapple in fruits and turnip and carrot in vegetables contained remarkable components of trace metals. The target hazard quotient (THQ) values for heavy metals were arranged in the order of Pb > Mn > Cu > Ni > Zn > Cr. No potential health risks were reported for individual elements over a lifetime of exposure, except children's exposure to Mn in pineapple and Pb in banana, orange small, guava, grape green, grape red, yellow-orange, and kiwifruit. The total THQ due to the dietary intake of multiple metals demonstrated unsafe limits in banana, pineapple, orange small, guava, grape green, grape red, yellow-orange, kiwifruit, and spinach leaf for children and pineapple for adults.


Assuntos
Exposição Dietética/estatística & dados numéricos , Monitoramento Ambiental , Metais Pesados/análise , Medição de Risco , Poluentes do Solo/análise , Adulto , Criança , Frutas/química , Humanos , Análise Multivariada , África do Sul , Oligoelementos/análise , Verduras
11.
Arch Microbiol ; 200(3): 493-503, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29197951

RESUMO

Occurrence of epibiont attachment on filamentous bacteria is a common phenomenon in activated sludge. In this study, an attempt has been made to elucidate the intrinsic nature of the attachment between the epibionts and filamentous bacteria based on microscopic observations. Characterization of the epiflora based on fluorescence in situ hybridization using group level probes revealed that the epibionts colonizing these filamentous bacteria largely belongs to the class Alphaproteobacteria, followed by Beta and Gammaproteobacteria. The ultrastructural examination using transmission electron microscopy pointed to the existence of a possible cell-to-cell interaction between epibionts and the selected filaments. Common bacterial appendages such as pili and fimbria were absent at the interface and further noted was the presence of cell membrane extensions on epibiont bacteria protruding towards the targeted filamentous cell. Fibrillar structures resembling amyloid-like proteins were observed within the filament cells targeted by the epibionts. An interaction was apparent between amyloid such as proteins and epibionts with regards to the direction of fibrillar structures and the distance of approaching epibiont bacteria. Due to the lack of visual evidence in support of penetration, the role of these amyloid-like fibrils as potential attachment sites for the epibionts was taken into consideration, and required further validation using conformational antibodies.


Assuntos
Alphaproteobacteria/ultraestrutura , Betaproteobacteria/ultraestrutura , Gammaproteobacteria/ultraestrutura , Alphaproteobacteria/genética , Alphaproteobacteria/crescimento & desenvolvimento , Betaproteobacteria/genética , Betaproteobacteria/crescimento & desenvolvimento , Gammaproteobacteria/genética , Gammaproteobacteria/crescimento & desenvolvimento , Hibridização in Situ Fluorescente , Microscopia Eletrônica de Transmissão , Esgotos/microbiologia
12.
Bioresour Technol ; 243: 1078-1086, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28764114

RESUMO

A Chlorella sp. was cultivated in a photobioreactor under different experimental conditions to investigate its acclimation to high-CO2 exposures. When the microalgae was grown under controlled flue gas sparging and optimised nutrients, the biomass concentration increased to 3.415±0.145gL-1 and the maximum protein yield was obtained (57.500±0.351% ww-1). However, when the culture was exposed to continuous flue gas, the lowest biomass growth (1.665±0.129gL-1) was noted. Under these conditions, high carbohydrate and lipid values were recorded (38.600±1.320% ww-1 and 30.200±0.150% ww-1), respectively. A Sugeno-type fuzzy model was employed to understand the correlation between peak biomass concentration (Bmax), CO2 uptake rate (qCO2), and maximum relative electron transport rate (rETRmax) as inputs and carbohydrate, protein, and lipid yields as outputs. Results of the model were in agreement with the experimental data (r2-value >0.985).


Assuntos
Biomassa , Chlorella , Dióxido de Carbono , Lógica Fuzzy , Microalgas
13.
J Water Health ; 15(4): 505-508, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28771147

RESUMO

Despite advances in microbial detection that quantitative polymerase chain reaction (qPCR) has led to, complex environmental samples, such as sediments, remain a challenge due to presence of PCR inhibitors. Aquatic sediments accumulate particle-bound microbial contaminants and thereby reflect a cumulative microbial load over time. The relatively new droplet digital PCR (ddPCR) has emerged as a direct quantitative method, highly tolerant to PCR inhibitors and relinquishing the necessity for calibration/standard curves. Information is virtually absent where ddPCR has been applied to detect pathogenic organisms in aquatic sediments. This study compared the efficacy of ddPCR with qPCR, for quantification of Salmonella in sediments from the Palmiet River near an informal settlement in Durban, South Africa. ddPCR significantly improved both analytical sensitivity and detection of low concentrations of Salmonella as compared to qPCR. The expected copy numbers measured from both qPCR and ddPCR showed good R2 values (0.999 and 0.994, respectively). The site mostly affected by the informal settlements exhibited Salmonella in the range of 255 ± 37 and 818 ± 30 Salmonella/g (p ≤ 0.0001) in qPCR and ddPCR, respectively. The improved detection of Salmonella in sediments with ddPCR makes it a promising technical method for the quantification of Salmonella in multifarious environmental samples.


Assuntos
Proteínas de Bactérias/análise , Monitoramento Ambiental/métodos , Sedimentos Geológicos/microbiologia , Reação em Cadeia da Polimerase/métodos , Salmonella/isolamento & purificação , Rios/microbiologia , África do Sul
14.
J Environ Manage ; 203(Pt 1): 299-315, 2017 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-28803154

RESUMO

Microalgae are recognized as one of the most powerful biotechnology platforms for many value added products including biofuels, bioactive compounds, animal and aquaculture feed etc. However, large scale production of microalgal biomass poses challenges due to the requirements of large amounts of water and nutrients for cultivation. Using wastewater for microalgal cultivation has emerged as a potential cost effective strategy for large scale microalgal biomass production. This approach also offers an efficient means to remove nutrients and metals from wastewater making wastewater treatment sustainable and energy efficient. Therefore, much research has been conducted in the recent years on utilizing various wastewater streams for microalgae cultivation. This review identifies and discusses the opportunities and challenges of different wastewater streams for microalgal cultivation. Many alternative routes for microalgal cultivation have been proposed to tackle some of the challenges that occur during microalgal cultivation in wastewater such as nutrient deficiency, substrate inhibition, toxicity etc. Scope and challenges of microalgal biomass grown on wastewater for various applications are also discussed along with the biorefinery approach.


Assuntos
Microalgas , Águas Residuárias , Animais , Biocombustíveis , Biomassa , Biotecnologia
15.
Environ Sci Pollut Res Int ; 24(18): 15299-15307, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28502047

RESUMO

Microalgae have tremendous potential to grow rapidly, synthesize, and accumulate lipids, proteins, and carbohydrates. The effects of solvent extraction of lipids on other metabolites such as proteins and carbohydrates in lipid-extracted algal (LEA) biomass are crucial aspects of algal biorefinery approach. An effective and economically feasible algae-based oil industry will depend on the selection of suitable solvent/s for lipid extraction, which has minimal effect on metabolites in lipid-extracted algae. In current study, six solvent systems were employed to extract lipids from dry and wet biomass of Scenedesmus obliquus. To explore the biorefinery concept, dichloromethane/methanol (2:1 v/v) was a suitable solvent for dry biomass; it gave 18.75% lipids (dry cell weight) in whole algal biomass, 32.79% proteins, and 24.73% carbohydrates in LEA biomass. In the case of wet biomass, in order to exploit all three metabolites, isopropanol/hexane (2:1 v/v) is an appropriate solvent system which gave 7.8% lipids (dry cell weight) in whole algal biomass, 20.97% proteins, and 22.87% carbohydrates in LEA biomass. Graphical abstract: Lipid extraction from wet microalgal biomass and biorefianry approach.


Assuntos
Biocombustíveis , Lipídeos/isolamento & purificação , Microalgas , Solventes , Biomassa
16.
Bioresour Technol ; 234: 320-326, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28340436

RESUMO

Dried powdered algae (SDPA), heat treated algae (MHTA), lipid extracted algae (LEA) and protein extracted algae (PEA) were digested to determine biomethane potential. The average CH4 production rate was ∼2.5-times higher for protein and lipid extracted algae than for whole algae (SDPA and MHTA) whilst the cumulative CH4 production was higher for pre-treated algae. Highest cumulative CH4 production (318.7mlCH4g-1VS) was observed for MHTA followed by SDPA (307.4mlCH4g-1VS). CH4/CO2 ratios of 1.5 and 0.7 were observed for MHTA and LEA respectively. Pre-treatment processes disrupted the algal cell wall, exposing intracellular material which remained intact as opposed to product extraction processes which broke down the intracellular compounds resulting in changes in elemental composition and decreases the cumulative gas yield and CH4/CO2 ratio. Comparative analysis determined that the most profitable route of biomass utilisation was protein extraction followed by biogas production giving ∼2.5-times higher return on investment.


Assuntos
Biomassa , Metano/biossíntese , Anaerobiose , Biocombustíveis , Lipídeos
17.
Environ Sci Pollut Res Int ; 24(9): 8790-8804, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28213710

RESUMO

Batch dark fermentation experiments were conducted to investigate the effects of initial pH, substrate-to-biomass (S/X) ratio, and concentrations of Fe2+ and magnetite nanoparticles on biohydrogen production from sugarcane bagasse (SCB) hydrolysate. By applying the response surface methodology, the optimum condition of steam-acid hydrolysis was 0.64% (v/v) H2SO4 for 55.7 min, which obtained a sugar yield of 274 mg g-1. The maximum hydrogen yield (HY) of 0.874 mol (mol glucose-1) was detected at the optimum pH of 5.0 and S/X ratio of 0.5 g chemical oxygen demand (COD, g VSS-1). The addition of Fe2+ 200 mg L-1 and magnetite nanoparticles 200 mg L-1 to the inoculum enhanced the HY by 62.1% and 69.6%, respectively. The kinetics of hydrogen production was estimated by fitting the experimental data to the modified Gompertz model. The inhibitory effects of adding Fe2+ and magnetite nanoparticles to the fermentative hydrogen production were examined by applying Andrew's inhibition model. COD mass balance and full stoichiometric reactions, including soluble metabolic products, cell synthesis, and H2 production, indicated the reliability of the experimental results. A qPCR-based analysis was conducted to assess the microbial community structure using Enterobacteriaceae, Clostridium spp., and hydrogenase-specific gene activity. Results from the microbial analysis revealed the dominance of hydrogen producers in the inoculum immobilized on magnetite nanoparticles, followed by the inoculum supplemented with Fe2+ concentration. Graphical abstract ᅟ.


Assuntos
Biocombustíveis/análise , Celulose/metabolismo , Fermentação , Hidrogênio/análise , Nanopartículas de Magnetita/química , Saccharum/metabolismo , Anaerobiose , Análise da Demanda Biológica de Oxigênio , Biomassa , Células Imobilizadas/metabolismo , Clostridium/metabolismo , Enterobacteriaceae/metabolismo , Hidrogênio/química , Concentração de Íons de Hidrogênio , Hidrólise , Nanopartículas de Magnetita/microbiologia , Saccharum/crescimento & desenvolvimento , África do Sul , Propriedades de Superfície
18.
Bioresour Technol ; 227: 82-92, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28013140

RESUMO

Wastewater utilization for microalgal biomass production is potentially the most economical route for its fuel and feed applications. In this study, suitability of various wastewater streams within a domestic wastewater treatment plant was evaluated for microalgal cultivation. Pre-treatment methods were evaluated to minimize bacterial load. Biomass, cell physiology, nutrient removal efficiencies and biochemical constituents of Chlorella sorokiniana were investigated in influent (INF) and anaerobic tank centrate (AC) under mixotrophic (Mixo) and heterotrophic (Hetero) cultivation. Promising biomass (77.14mgL-1d-1), lipid (24.91mgL-1d-1), protein (22.36mgL-1d-1) and carbohydrate (20.10mgL-1d-1) productivities were observed in Mixo AC with efficient ammonium (94.29%) and phosphate (83.30%) removal. Supplementation of urea at a concentration of 1500mgL-1 further enhanced biomass (162.50mgL-1d-1), lipid (24.91mgL-1d-1), protein (22.36mgL-1d-1) and carbohydrate (20.10mgL-1d-1) productivities in Mixo AC. Urea supplemented mixotrophic cultivation of microalgae in AC is developed as a biomass production strategy.


Assuntos
Chlorella/crescimento & desenvolvimento , Meios de Cultura/química , Microalgas/crescimento & desenvolvimento , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Compostos de Amônio/metabolismo , Anaerobiose , Biomassa , Carboidratos/biossíntese , Chlorella/metabolismo , Processos Heterotróficos , Lipídeos/biossíntese , Microalgas/metabolismo , Águas Residuárias/microbiologia
19.
Bioresour Technol ; 219: 749-752, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27528269

RESUMO

Chlorella pyrenoidosa was cultivated in secondary wastewater effluent to assess its nutrient removal capabilities. Wastewaters were obtained from a wastewater treatment plant located in Ouargla, Algeria. The experiments were conducted in winter under natural sunlight in an outdoor open raceway pond situated in the desert area. The highest biomass of the microalgae was found to be 1.71±0.04g/L. Temperatures ranged between 18 and 31°C. The average annual insolation was no less than 3500h with an annual solar irradiance of more than 2000kWh/m(2). Analyses of different parameters including COD, NH4(+)-N and TP were conducted throughout the cultivation period. Their average removal efficiencies were 78%, 95% and 81% respectively. The results demonstrated the potential of nutrient removal by microalgae grown on secondary wastewater in arid areas.


Assuntos
Chlorella/crescimento & desenvolvimento , Microalgas/crescimento & desenvolvimento , Eliminação de Resíduos Líquidos/métodos , Argélia , Amônia/metabolismo , Análise da Demanda Biológica de Oxigênio , Biomassa , Chlorella/metabolismo , Clima Desértico , Microalgas/metabolismo , Nitrogênio/metabolismo , Tanques , Temperatura Ambiente , Águas Residuárias/química
20.
Microb Ecol ; 72(1): 49-63, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-26906468

RESUMO

Nitrification at a full-scale activated sludge plant treating municipal wastewater was monitored over a period of 237 days. A combination of fluorescent in situ hybridization (FISH) and quantitative real-time polymerase chain reaction (qPCR) were used for identifying and quantifying the dominant nitrifiers in the plant. Adaptive neuro-fuzzy inference system (ANFIS), Pearson's correlation coefficient, and quadratic models were employed in evaluating the plant operational conditions that influence the nitrification performance. The ammonia-oxidizing bacteria (AOB) abundance was within the range of 1.55 × 10(8)-1.65 × 10(10) copies L(-1), while Nitrobacter spp. and Nitrospira spp. were 9.32 × 10(9)-1.40 × 10(11) copies L(-1) and 2.39 × 10(9)-3.76 × 10(10) copies L(-1), respectively. Specific nitrification rate (qN) was significantly affected by temperature (r 0.726, p 0.002), hydraulic retention time (HRT) (r -0.651, p 0.009), and ammonia loading rate (ALR) (r 0.571, p 0.026). Additionally, AOB was considerably influenced by HRT (r -0.741, p 0.002) and temperature (r 0.517, p 0.048), while HRT negatively impacted Nitrospira spp. (r -0.627, p 0.012). A quadratic combination of HRT and food-to-microorganism (F/M) ratio also impacted qN (r (2) 0.50), AOB (r (2) 0.61), and Nitrospira spp. (r (2) 0.72), while Nitrobacter spp. was considerably influenced by a polynomial function of F/M ratio and temperature (r (2) 0.49). The study demonstrated that ANFIS could be used as a tool to describe the factors influencing nitrification process at full-scale wastewater treatment plants.


Assuntos
Inteligência Artificial , Bactérias/classificação , Nitrificação , Esgotos/microbiologia , Amônia/metabolismo , Bactérias/isolamento & purificação , DNA Bacteriano/genética , Hibridização in Situ Fluorescente , Modelos Teóricos , Nitrobacter/classificação , Reação em Cadeia da Polimerase em Tempo Real , Temperatura Ambiente , Gerenciamento de Resíduos
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