A mathematical model of a plane, steady state biofilm, with the use of a single substrate kinetics, was proposed. A set of differential equations was solved. In order to analyse the biofilm’s behaviour, a number of simulations were performed. The simulations included varying process parameters such as detachment coefficient and substrate loading. Two detachment models were taken into consideration: one describing the detachment ratio as proportional to the thickness of the biofilm, and the other one proportional to the thickness of the biofilm squared. The results provided information about substrate and live cell distribution in biofilm and the influence of certain parameters on biofilm behaviour.
Enterococcus hirae belongs in the Enterococcus faecium group within the genus Enterococcus. This species occurs naturally in the environment, commensally in the alimentary tracts of animals, and pathologically for example in humans with urinary infections. Some strains of E. hirae possess virulence factors, including biofilm formation. Biofilm growth protects bacteria against host de- fences; biofilm can be a source of persistent infection. Testing bacterial strains for their ability to form biofilm might therefore facilitate their treatment or prevention. This study focuses on bio- film formation by E. hirae strains derived from various animals. This kind of testing has never been done before. A total of 64 identified E. hirae from laying hens, ducks, pheasants, ostriches, rabbits, horses and a goat were tested by means of three methods; using Congo red agar, the tube method and microtiter plate agar. The majority of strains were found to form biofilm. 62.5% of strains were biofilm-forming, four categorized as highly positive (OD570 ≥1); most strains were low-grade biofilm positive (0.1 ≤ OD 570 < 1). Related to poultry, 55 E. hirae strains were tested nd found to produce biofilm; 24 strains did not form biofilm, 31 strains were biofilm-forming; 27 strains showed low-grade biofilm formation, and four strains were highly biofilm-forming. Four strains from hens and ostriches reached the highest OD570 values, more than 0.500. Rabbit-derived E. hirae strains as well as strains isolated from horses and the goat were low-grade bio- film-forming. Microtiter plate assay proved to be the best tool for testing the in vitro biofilm for- mation capacity of E. hirae strains from different species of animals.
The suitability of low-cost impedance sensors for microbiological purposes and biofilm growth monitoring was evaluated. The sensors with interdigitated electrodes were fabricated in PCB and LTCC technologies. The electrodes were golden (LTCC) or gold-plated (PCB) to provide surface stability. The sensors were used for monitoring growth and degradation of the reference ATCC 15442 Pseudomonas aeruginosa strain biofilm in invitro setting. During the experiment, the impedance spectra of the sensors were measured and analysed using electrical equivalent circuit (EEC) modelling. Additionally, the process of adhesion and growth of bacteria on a sensor’s surface was assessed by means of the optical and SEM microscopy. EEC and SEM microscopic analysis revealed that the gold layer on copper electrodes was not tight, making the PCB sensors susceptible to corrosion while the LTCC sensors had good surface stability. It turned out that the LTCC sensors are suitable for monitoring pseudomonal biofilm and the PCB sensors are good detectors of ongoing stages of biofilm formation.
The study concerns modeling and simulation of the growth of biofilms with heterogeneous structures with a discrete mathematical model based on theory of cellular automata. The article presents two-dimensional density distributions of biofilms for microbial processes: oxidation of ammonium by Nitrosomonas europaea bacteria and glucose utilization by Pseudomonas aeruginosa bacteria. The influence of limiting substrate concentration in the liquid phase on biofilm structure was determined. It has been shown that the value of death rate coefficient of microorganisms has the qualitative and quantitative influence on the density and porosity of the biofilm.
Azo dye wastewater treatment is urgent necessary nowadays. Electrochemical technologies commonly enable more efficient degradation of recalcitrant organic contaminants than biological methods, but those rely greatly on the energy consumption. A novel process of biofilm coupled with electrolysis, i.e., bioelectrochemical system (BES), for methyl orange (MO) dye wastewater treatment was proposed and optimization of main influence factors was performed in this study. The results showed that BES had a positive effect on enhancement of color removal of MO wastewater and 81.9% of color removal efficiency was achieved at the optimum process parameters: applied voltage of 2.0 V, initial MO concentration of 20 mg/L, glucose loads of 0.5 g/L and pH of 8.0 when the hydraulic retention time (HRT) was maintained at 3 d, displaying an excellent color removal performance. Importantly, a wide range of effective pH, ranging from 6 to 9, was found, thus greatly favoring the practical application of BES described here. The absence of a peak at 463 nm showed that the azo bond of MO was almost completely cleaved after degradation in BES. From these results, the proposed method of biodegradation combined with electrochemical technique can be an effective technology for dye wastewater treatment and may hopefully be also applied for treatment of other recalcitrant compounds in water and wastewater.
A model of bacterial filtration on fibrous filter media is developed. The single fibre efficiency as well as the efficiency of the whole filter - at the onset of the process and the evolution of those quantities - are analysed. The differences between the numerical modelling of colloidal particles and bacteria are stressed in detail. The main differences are the active motion ability of bacteria and biofilm formation. The parameters of the model were identified based on the literature data.
A mathematical model for a two-phase fluidised bed bioreactor with liquid recirculation and an external aerator was proposed. A stationary nonlinear analysis of such a bioreactor for an aerobic process with double-substrate kinetics was carried out. The influences of a volumetric fraction of solid carriers in the liquid phase, the rate of active biomass transfer from the biofilm to the liquid, the concentration of carbonaceous substrate, the mean residence time of the liquid and the efficiency of the external aerator on the steady state characteristics of the bioreactor were described. A method for determination of the minimal recirculation ratio related to oxygen demand and fluidised bed conditions was presented. On the basis of the obtained results, it is possible to choose reasonable operating conditions of such plants and to determine constraints, while considering acceptable concentrations of a toxic substrate being degraded.
Results of the studies for determining fractions of organic contaminants in a pretreated petrochemical wastewater flowing into a pilot Aerated Submerged Fixed-Bed Biofilm Reactor (ASFBBR) are presented and discussed. The method of chemical oxygen demand (COD) fractionation consisted of physical tests and biological assays. It was found that the main part of the total COD in the petrochemical, pretreated wastewater was soluble organic substance with average value of 57.6%. The fractions of particulate and colloidal organic matter were found to be 31.8% and 10.6%, respectively. About 40% of COD in the influent was determined as readily biodegradable COD. The inert fraction of the soluble organic matter in the petrochemical wastewater constituted about 60% of the influent colloidal and soluble COD. Determination of degree of hydrolysis (DH) of the colloidal fraction of COD was also included in the paper. The estimated value of DH was about 62%. Values of the assayed COD fractions were compared with the same parameters obtained for municipal wastewater by other authors.
In this study, a pilot-scale subsurface wastewater infiltration system (SWIS) was deployed to study landscape water treatment. The goal of the study was to investigate the effects of hydraulic loading on pollutant removal and the spatial distribution of biofilm properties in SWIS. Results showed that the efficiencies of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal degraded as hydraulic loading increased. Furthermore, quantities of the biofilm properties parameter s increased with the hydraulic loading. Polysaccharide and protein levels ranged from 560 to 1110 μg/g filler and 60 to 190 μg/g filler, respectively, at a hydraulic loading of 0.2 m/d. At a hydraulic loading of 0.4 m/d, the quantities of polysaccharide and protein ranged from 1200 to 3300 μg/g filler and 80 to 290 μg/g filler, respectively. Biofilm intensity and biofilm activity per unit weight decreased with the increase in hydraulic loading.
The aim of the study was to determine the impact of selected factors on the reduction of organic pollutants, expressed in BOD5 and CODCr, in wastewater treated in a laboratory scale model of moving bed biofilm reactor (MBBR). The factors included in the experiment: the degree of filling the fluidized bed with biomass carriers, hydraulic load, and aeration intensity. The tested model of the bioreactor consisted of five independent chambers with diameter D = 0.14 m and height H = 2.0 m, which were filled with biomass carriers at 0%, 20%, 40%, 60%, 70% of their active volume. During the test period, hydraulic loads at the level of Qh1 = 0.073 m3·m-2·h-1 and Qh2 = 0.036 m3·m-2·h-1 were applied, which ensured one-day and two-day sewage retention, respectively.The said reactors were subjected to constant aeration at P1 = 3.0 dm3·min-1 and P2 = 5.0 dm3·min-1. The highest efficiency of the reduction of the analysed indicators was demonstrated by reactors filled with carriers in the degree of 40–60%. Based on the statistical analyses (the analyses of the ANOVA variations and the Kruskal-Wallis test) carried out, it was found that the studied factors significantly modified the mutual interaction in the process of reducing BOD5 in treated wastewater of the reactors tested. The significance of the impact of the discussed factors on the values of the studied indicators in treated wastewater depends on mutual interactions between the investigated factors.
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