Papers by Keyword: Biofilm

Abstract: Two parallel biofilm reactors were developed and applied for treating the simulated wastewater. The experimental results showed that compared with a without electric-shocking biofilm, and a mean removal rate of COD increased by 18.82% by shocking of direct current. Which suggested that the electro-shocking can significantly increase the removal rate of COD.

Abstract: The aim of the present work was to assess the surface ability of three bioceramic materials (A: alumina BIOLOX^®forte; B: Si₃N₄; C: alumina matrix composite BIOLOX^®delta) to inhibit bacterial biofilm formation. For this purpose, ceramic disks at standardized roughness (Ra = 0,25 μm) were used as test materials while commercial polystyrene was considered as control. Two biofilm-producing bacterial strains (S. epidermidis ATCC14990, Escherichia coli ATCC25922) were used for experiments. The viable biomass was assessed by the metabolic MTT assay after 24h incubation. Morphological data regarding biofilms structure were obtained by scanning electron microscopy. In general, results revealed that all bioceramics materials were significantly less colonized compared to polystyrene. The degree of biofilm formation onto bioceramics ranged between about 30 to 60% less than the polystyrene control. Moreover, some differences were noticed by comparing the three bioceramics inhibition ratio: bioceramic A showed significanlty less S. epidermidis biofilm formation (p<0.005) compared to B and C that showed similar performance. Conversely, no difference were noted for E. coli biofilm amount for A, B and C. In conclusion, the tested materials showed capability to reduce biofilm formation to a different extent depending on the tested bacterial strains.

Abstract: We studied the effects of flushing on water quality and biofilm biomass in different daily flow patterns of distribution system. After building up steady biofilm layers in two flow velocity (0.25 m/s and 0.65 m/s) distribution systems consisting of PE pipe, then flushed by stepwise increased flow velocity. An increase flow velocity caused an immediate increase in turbidity and heterotrophic bacteria of water as a result of detachment of biofilms in the pipes, especially in low flow patterns distribution system. Three days later after flushing, water quality of two systems were generally lower and more stable than before flushing. Flushing strategies only limited biofilm growth to a certain extent and did not completely eliminate microorganisms from the systems.The low flow velocity distribution system was easily being disturbed by flushing.

Abstract: The aim of this study is to evaluate the effect of shear stress on detachment and nitrification process in a mixed-population biofilm. The biofilm was grown under constant flow condition with low C/N ratio. During the experiment, ammonium oxidation rate reached above 99%. Sloughing events happened mainly under constant hydrodynamic condition. Detachment experiment showed that it’s not possible to control the occurrence of sloughing events by controlling shear stress. Pyrosequencing analysis of the biofilm showed that Proteobacteria and Bacteroidetes were the two most abundant phyla, but detachment would influence the relative abundance of AOB and NOB in biofilm to affect the nitrification process.

Abstract: The objective of this work was to evaluate the performances of A lab-scale innovative sequencing batch biofilm reactor (SBBR) to treat domestic wastewater,in which a acryl cylinder (height 200 mm, diameter 70 mm) was equipped and many fiber threads were attached to the surface of the cylinder as the bacteria carrier. No time and volume for settling was required in this system. After one year’s operation, each parameter achieved the wastewater discharged criterion in 2 cycles (4 h). It was found that COD removal efficiency was up to 90% in 3 h, and ammonium nitrogen concentration approached the least value; total nitrogen removal efficiency reached 55%-71%. In this SBBR system simultaneous nitrification and denitrification was completed at the end of 2 cycles.

Abstract: This 3 phase study examined (1) the effect of microwave irradiation on the adhesion and (2) biofilm formation of 4 candidal species on heat polymerized polymethyl methacrylate (PMMA) specimens. Lastly, (3) the flexural strength of heat polymerized PMMA was tested.C. albicans (ATCC 10231), C. glabrata (ATCC 22019), C. krusei (ATCC 6258) and C. parapsilosis (ATCC 90030) were used. The flexural strength of the PMMA resin after microwave irradiation was tested in accordance with ISO 20795-1 specifications. A one-way ANOVA statistical analysis was used for all the results.The maximum effect of 94% to 98% reduction in adhesion and biofilm counts was seen with microwave irradiation at 850 W and 1000 W for 120 sec. There was no significant difference between the control and irradiated specimens in terms of flexural strength. Reduction of candida adhesion and biofilm on PMMA resin can be achieved with microwave irradiation.

Abstract: Due to the existence of some kinds of minim organic matters in drinking water distribution systems, biofilms are commonly found on the inner walls of pipe networks, and it can contribute to the deterioration to water quality and influence water supply security. The current situations of the study of the biofilm are summarized. Two typical kinds of reactors often used in laboratories are stated. And numerous environmental factors influencing biofilm formation, including hydraulic condition, water temperature, pipe material, water temperature, disinfectant residuals and nutrient element, are reviewed. Furthermore, some key aspects for future research to control the development of biofilms are proposed. Keywords: drinking water distribution system; biofilm; simulation system; disinfectant residual

Abstract: Algae are amongst the most photosynthetically efficient organisms harnessing solar energy for all its metabolic life-supporting activities. The solar energy is transformed into chemical energy in a normally wasteful process. In this study, this excess wasted energy may be directed towards electricity generation in a biophotovoltaic platform. This is a new approach in renewable energy production from algae. As an initial step, algal biofilms are established on indium tin oxide (ITO) anodes. Two microalgae, the unicellular Chlorella UMACC 313 and the filamentous Spirulina UMACC 159 were used to form biofilm on ITO anodes under three different treatments (T₁: unmodified smooth surface , T₂: modified surface etched with interval of 2.5 mm between lines and T₃: modified surface etched with interval of 1 mm between lines). Results show significantly higher biofilm coverage on the etched anodes compared to the smooth ones. Anodes of T₃ registered the highest biofilm coverage of 99.46% for Chlorella. For Spirulina, highest biofilm coverage (80.70%) was observed on T₂ anodes. The increase in biofilm coverage successfully resulted in increase of photosynthetic efficiency for both strains. Spirulina registered the highest maximum relative electron transport rate at 153.507 μmol electrons m^-2s^-1 compared to Chlorella (140.796 μmol electrons m^-2s^-1). This was correlated to pigment content. Biofilms established on the ITO anodes and the resulting high rate of photosynthetic efficiency achieved in these experiments are expected to enable electrical energy production from biophotovoltaic platforms.

Abstract: This work evaluates the feasibility of the biodegradable polymers (BDPs) bioreactor concept for removal of perchlorate from groundwater; and the likely impacts of nitrate and pH were also examined. Batch experiments demonstrated clearly that ClO₄^- was eliminated from the aqueous phase readily under appropriate surface biofilm of enriched mixed consortium on PBS, a new kind of BDPs, with the PBS granules as the sole chemical and physical substrate for the microorganism. Simultaneous perchlorate and nitrate degradation were occurring with the PBS granules degradation to supply conbon source. The optimal pH of perchlorate reduction was at 6.7. Morphological observation indicated the microbes in biofilm decomposed PBS through metabolism and provided carbon source for themselve by releasing small organic molecules.

Abstract: A kind of controlled-release carbon source, starch / polyvinyl alcohol blends (SPVA), was used as both carbon source and biofilm supporter in laboratory-scale fluidized-bed biofilm reactors (FBBRs) to remove nitrate from groundwater. Results show: when the influent nitrate concentration was 100 mg-N /L, FBBRs packed with SPVA can effectively remove nitrate from groundwater at the condition of temperature 20 °C, hydraulic resident time (HRT) 4 h. The effluent nitrate can meet with the Chinese drinking water standards at low temperature (15-2 °C) by adjusted the HRT of FBBRs. The denitrification rate declined nonlinearly with the decrease of temperature and changed sharply in the range of 20-15 °Cand 10-5 °C.