Wastewater treatment in a pilot-scale submerged membrane bioreactor : study of hydrodynamics under constant operating pressure

A pilot-scale Submerged Membrane Bioreactor provided with PEI hollow fiber membranes was operated under constant pressure mode in order to evaluate the effects of hydrodynamic conditions on the process performance, such as air flow rate, module packing density and aeration configuration. For the three different air flow rates studied (2, 5 and 8 L/min), results showed a limit value for this parameter, in which above this value a better performance will not be obtained and can even be worse. The air flow rate of 5 L/min presented the best performance, followed by 8 and 2 L/min. The module packing density was studied for two diameters (0.75 and 1 inch); the best result was observed for the larger diameter module, because lower packing density causes more space between fibers, increasing the aeration homogeneity inside de fiber bundle. Both aeration geometric tested showed similar permeate fluxes, indicating they did not affect the process performance. For all hydrodynamic conditions, the removal of TOC and COD was 96% and 93%, respectively

Human dental pulp stem cell adhesion and detachment in polycaprolactone electrospun scaffolds under direct perfusion

Cell adhesion in three-dimensional scaffolds plays a key role in tissue development. However, stem cell behavior in electrospun scaffolds under perfusion is not fully understood. Thus, an investigation was made on the effect of flow rate and shear stress, adhesion time, and seeding density under direct perfusion in polycaprolactone electrospun scaffolds on human dental pulp stem cell detachment. Polycaprolactone scaffolds were electrospun using a solvent mixture of chloroform and methanol. The viable cell number was determined at each tested condition. Cell morphology was analyzed by confocal microscopy after various incubation times for static cell adhesion with a high seeding density. Scanning electron microscopy images were obtained before and after perfusion for the highest flow rate tested. The wall pore shear stress was calculated for all tested flow rates (0.005–3 mL/min). An inversely proportional relationship between adhesion time with cell detachment under perfusion was observed. Lower flow rates and lower seeding densities reduced the drag of cells by shear stress. However, there was an operational limit for the lowest flow rate that can be used without compromising cell viability, indicating that a flow rate of 0.05 mL/min might be more suitable for the tested cell culture in electrospun scaffolds under direct perfusion

Dobivanje koncentriranih i pročišćenih fruktooligosaharida iz korijena biljke Smallanthus sonchifolius pomoću membranske tehnologije

Yacon is a perennial plant originating from the Andean region whose roots have been receiving increased att ention due to their high content of prebiotic fructooligosaccharides (FOS). Apart from many health benefi ts, FOS have interesting characteristics as food ingredients, so are used as sugar substitute, and their extraction from yacon roots may be an alternative to commercially available FOS. This work evaluates membrane technology for concentration and purifi cation of FOS from yacon root extract, combining ultrafiltration (UF) with nanofi ltration (NF), with and without the use of discontinuous diafi ltration (DF). After UF, 63.75 % of the saccharides from the initial feed were recovered in total permeate. DF did not largely infl uence FOS retention during NF (it increased from 68.78 % without DF to 70.48 % with DF), but decreased glucose and fructose retentions, from 40.63 to 31.61 % and 25.64 to 18.69 %, respectively, which was desirable, allowing greater purification of FOS in the retentate. The yield of total saccharides in the final retentate after combined UF and NF processes was 50.89 % and of FOS was 51.85 %, with 19.75 % purity. The results indicate that the combined UF and NF is a promising technique for concentrating yacon saccharides, but more diafi ltration steps are required for the improvement of FOS purity.Biljka Smallanthus sonchifolius je trajnica iz područja Anda, čiji je korijen bogat prebiotičkim fruktooligosaharidima, zbog čega je zanimljiva kao sirovina za prehrambenu industriju. Osim što pozitivno utječu na zdravlje, fruktooligosaharidi se zbog svojih svojstava mogu upotrijebiti kao dodatak hrani, te kao zamjena za šećer. Fruktooligosaharidi dobiveni ekstrakcijom iz korijena južnoameričke biljke Smallanthus sonchifolius mogu se upotrijebiti kao zamjena za komercijalno dostupne fruktooligosaharide. U ovom je radu ispitan postupak dobivanja koncentriranih i pročišćenih fruktooligosaharida iz ekstrakta korijena biljke, i to pomoću ultrafiltracije i nanofiltracije, u kombinaciji s diskontinuiranom dijafiltracijom ili bez nje. Nakon ultrafiltracije, 63,75 % se početne količine saharida zadržalo u permeatu. Diskontinuirana dijafiltracija nije bitno utjecala na udjel fruktooligosaharida u retentatu nakon nanofiltracije (bez dijafiltracije udjel je bio 63,78 %, a sa dijafiltracijom 70,48 %), ali je smanjila udjel glukoze, i to s 40,63 na 31,61 %, i fruktoze s 25,64 na 18,69 %, čime je omogućeno bolje pročišćavanje fruktooligosaharida iz retentata. Prinos ukupnih saharida u retentatu nakon kombiniranog tretmana ultrafiltracijom i nanofiltracijom bio je 50,89 %, a fruktooligosaharida 51,85 %, uz čistoću od 19,75 %. Rezultati pokazuju da je kombinacija ultra- i nanofiltracije prikladna metoda dobivanja koncentriranih saharida iz korijena biljke Smallanthus sonchifolius, ali da su za poboljšanje čistoće fruktooligosaharida potrebni su dodatni koraci u postupku dijafiltracije

Evaluation of membrane microfiltration fouling in landfill leachate treatment

 The membrane separation capacity allows the retention of the remaining organic matter that could not be removed by the biological process, increasing the treatment efficiency. The aim of this study was to evaluate the microfiltration (MF) process in a tertiary treatment system for landfill leachate from the Rincão das Flo-res, Caxias do Sul/RS/Brazil. The microfiltration system of commercial hollow fiber membrane poly(ether-imide) was tested in oder to promote leachate treatment. The tests carried out were leachate permeation, con-centration factor, determination of fouling and obtention of the values of the resitance to the flux. The re-sistance due to fouling and flux decline were evaluated to determine the best operating conditions. The poten-tial for fouling was 53% and was evaluated by comparing the pure water permeability before and after the leachate filtration. It was observed that the resistance due to fouling express 32% of the total resistance. The results showed that the MF process allows the elimination of up to 43% of the organic matter measured as chemical oxygen demand (COD) and 63% of that measured as biological oxygen demand (BOD5).Keywords: leachate; microfiltration; fouling; membrane resistance