Search results for "extracellular polymeric substance"
showing 10 items of 34 documents
Granulation and microbial community dynamics in the chitosan-supplemented anaerobic treatment of wastewater polluted with organic solvents.
2018
Abstract The effect of chitosan on the development of granular sludge in upflow anaerobic sludge blanket reactors (UASB) when treating wastewater polluted with the organic solvents ethanol, ethyl acetate, and 1-ethoxy-2-propanol was evaluated. Three UASB reactors were operated for 219 days at ambient temperature with an organic loading rate (OLR) of between 0.3 kg COD m −3 d −1 and 20 kg COD m −3 d −1 . One reactor was operated without the addition of chitosan, while the other two were operated with the addition of chitosan doses of 2.4 mg gVSS −1 two times. The three reactors were all able to treat the OLR tested with COD removal efficiencies greater than 90%. However, the time required to…
Combination of the OSA process with thermal treatment at moderate temperature for excess sludge minimization
2019
Abstract This study investigated the chance to couple the conventional Oxic Settling Anaerobic (OSA) process with a thermic treatment at moderate temperature (35 °C). The maximum excess sludge reduction rate (80%) was achieved when the plant was operated under 3 h of hydraulic retention time (HRT). Compared with the conventional OSA system, the thermic treatment enabled a further improvement in excess sludge minimization of 35%. The observed yield coefficient decreased from 0.25 gTSS gCOD−1 to 0.10 gTSS gCOD−1 when the temperature in the anaerobic reactor was increased to 35 °C, despite the lower HRT (3 h vs 6 h). Moreover, the thermic treatment enabled the decrease of filamentous bacteria,…
The role of extracellular polymeric substances on aerobic granulation with stepwise increase of salinity
2018
Abstract A granular sequencing batch reactor (GSBR) worked for 164 days to study the effect of salinity on aerobic granulation. The feeding had an organic loading rate (OLR) of 1.6 kg COD⋅m −3 ⋅d −1 and a gradual increase of salinity (from 0.30 to 38 g NaCl − ⋅L −1 ) to promote a biological salt-adaptation. First aggregates (average diameter ≈ 0.4 mm) appeared after 14 days. Extracellular polymeric substances (EPSs) analyses revealed that proteins were mainly higher than polysaccharides, and microorganisms metabolized EPSs as additional carbon source, mostly in feast phase, to face the energy demand for salinity adaptation. No significant worsening of organic matter removal was observed. Th…
The role of extracellular polymeric substances (EPS) on aerobic granules formation: comparison between a case of synthetic wastewater supply and anot…
2017
The paper focused on the evolution and the comparison of the extracellular polymeric substances (EPSs) content during the granulation process in two Granular Sequencing Batch Airlift Reactors (GSBAR) (3,5 L) fed with synthetic (R1) and industrial wastewater (R2). The results showed that in both the reactors the EPSs, in particular proteins (PN), were mainly produced during the feast phase because of the high substrate availability, especially under conditions of metabolic stress. Then, the EPSs content reduced during the famine period, because of biodegradation by bacteria. More in detail, during the granulation process, a greater polysaccharides (PS) consumption occurred in both reactors, …
Evaluation of the antibacterial power and biocompatibility of zinc oxide nanorods decorated graphene nanoplatelets: New perspectives for antibiodeter…
2017
Background Nanotechnologies are currently revolutionizing the world around us, improving the quality of our lives thanks to a multitude of applications in several areas including the environmental preservation, with the biodeterioration phenomenon representing one of the major concerns. Results In this study, an innovative nanomaterial consisting of graphene nanoplatelets decorated by zinc oxide nanorods (ZNGs) was tested for the ability to inhibit two different pathogens belonging to bacterial genera frequently associated with nosocomial infections as well as biodeterioration phenomenon: the Gram-positive Staphylococcus aureus and the Gram-negative Pseudomonas aeruginosa. A time- and dose-…
Effect of biomass features on oxygen transfer in conventional activated sludge and membrane bioreactor systems
2019
Abstract The aim of the present study was to compare the oxygen transfer efficiency in a conventional activated sludge and a membrane bioreactor system. The oxygen transfer was evaluated by means of the oxygen transfer coefficient and α-factor calculation, under different total suspended solids concentration, extracellular polymeric substances, sludge apparent viscosity and size of the flocs. The oxygen transfer coefficient and α-factor showed an exponential decreasing trend with total suspended solid, with a stronger oxygen transfer coefficient dependence in the conventional activated sludge compared to the membrane bioreactor. It was noted that the oxygen transfer coefficient in the conve…
Intermittent operation of UASB reactors treating wastewater polluted with organic solvents: process performance and microbial community evaluation
2019
The effect of intermittent feeding on the treatment of wastewater polluted with ethanol, ethyl acetate and 1-ethoxy-2-propanol in anaerobic upflow sludge blanket reactors was investigated. Three laboratory-scale reactors, one periodically supplemented with chitosan, were operated in an intermittent pattern (16 hours per day; 5 days per week) during 5 months. Removal efficiencies higher than 94% were obtained at organic loading rates up to 50 kg COD m−3 d−1. The addition of chitosan positively affected the specific methanogenic activity of the granular sludge. Although partial deterioration of the granules was observed, it was not correlated with variations in the production of extracellular…
Experimental modeling of bacterially-induced Ca carbonate precipitation: new insights on possible mechanisms.
2015
The contribution of microorganisms, particularly bacteria, in carbonate mineral formation, the main natural processes controlling CO2 level in the atmosphere, has played an important role since the Archean Eon. In this study we review our recent experimental work on CaCO3 precipitation induced by two anoxygenic phototrophic bacteria (APB), Rhodovulum steppense A-20sT and Rhodovulum sp. S-17-65, and by cyanobacteria Gloeocapsa sp. f-6gl. These bacteria are representatives of two important groups of photosynthetic organisms present at the Earth surface both in the past and at the present times. The mechanisms of organomineralization deriving from APB and cyanobacteria activities are drastical…
The sludge dewaterability in advanced wastewater treatment: a survey of four different Membrane BioReactor pilot plants
2017
The wasted activated sludge dewaterability represents a major concern for Wastewater Treatment Plants (WWTPs) managers. Indeed, whereas the dewatered sludge could represents a re-usable matrix, the principal drawback related to the wasted sludge dewaterability is the high water content due to the presence of extracellular polymeric substances (EPS) that allow the trapping of water molecules within the bio sludge flocs. In order to provide an outlook of the dewaterability features of activated sludge derived from advanced WWTP, the present research reports a long term survey (over two years) aimed at assessing the principal dewaterability parameters of the sludge wasted from different Membra…
Evidence for a biogenic, microorganismal origin of rock varnish from the Gangdese Belt of Tibet
2010
In the present study we examined material from the Ashikule Basin of Tibet. Chemical analyses were performed by use of energy dispersive X-ray spectroscopy and electron probe microanalysis to clarify whether the varnish layers that had developed on the surface of the rhyolite are indeed composed of varnish bodies and silica glaze. Electron microscopic analyses revealed that the surface of the varnish is covered both by filamentous hyphae bacterial and cocci-shaped forms. Within the varnish mineral layer in those samples two forms of bacteria-like microorganisms exist; cocci as tightly packed bacterial aggregates [within varnish bodies], and bacillus-like microorganisms [within the varnish m…