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    A comparison of a blower and a Venturi aeration system in a submerged membrane bioreactor
    (Desalination Publ, 2017) Kayaalp, Necati; Ozturkmen, Gokmen; Gul, Ertugrul; Gunay, Elif
    A novel aeration method for submerged membrane bioreactors (MBR) was developed in this study. This method uses a Venturi injector to supply the air to the MBR. Short term experiments were performed to determine the technical applicability of integrating a venturi device into a submerged MBR. A flat-sheet, 0.1-mu m polyvinylidene fluoride membrane was used to operate the MBR. Real wastewater taken from Diyarbakir Municipal Wastewater Treatment Plant was used as feed. Membrane fouling was evaluated under three different fluxes (18, 32, and 50 L/m(2) . h) and 3 L/min aeration rate for both blower-and venturi-aerated MBR systems. Transmembrane pressure (TMP), chemical oxygen demand (COD), mixed liquor suspended solids, mixed liquor volatile suspended solids, pH, dissolved oxygen, and temperature were measured in the experimental setup. The COD removal rate was between 75-92% for blower system and 85-87% for venturi system. Effluent NH4-N concentration was between 0.0-14.7 mg/L for blower system and 0.0-0.7 for venturi system. While the effluent NO3-N was between 3.1-27.4 mg/L for blower system, it was 33.3-37.8 mg/L for venturi system. At 3 L/min aeration rate, the dissolved oxygen concentration in MBR was between 0.42-3.43 mg/L for blower-aerated system and between 6.43-7.07 mg/L for venturi-aerated system. TMP development at different fluxes in blower and venturi systems showed that integration of a venturi device with a submerged MBR improved filtration capacity significantly. The rate of TMP increase in blower-aerated system was higher than that of venturi-aerated system at the same aeration rate of 3 L/min for both systems. At the highest filtration flux tested (50 L/m(2) . h), venturi-aerated system operated three times longer than the blower system.
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    Öğe
    Optimizing pectin lyase production using the one-factor-at-a-time method and response surface methodology
    (Wiley, 2024) Gul, Ertugrul; Dursun, Arzu Yadigar; Tepe, Ozlem; Akaslan, Gonca; Pampal, Fadile Gul
    Pectinases are commonly industrially synthesized by molds. This study aimed to optimize pectin lyase synthesis by a bacterium, Pseudomonas fluorescens, using both the one-factor-at-a-time (OFAT) method and response surface methodology. First, on optimization of pectin lyase fermentation by the OFAT method, the effects of pectin, peptone, yeast extract, (NH4)(2)SO4, pH, and salts were investigated. The highest pectin lyase activity was determined to be 28.63 U/mL at pH 8, 30 degrees C, with 1% (w/v) pectin and 0.14% (w/v) (NH4)(2)SO4 concentration at the 90th hour. The effect of substrate inhibition on the microbial growth was also investigated, and the results showed that the process can be described by noncompetitive inhibition model. The values of kinetic constants were determined as mu (m) = 0.175 h(-1), K-S = 6.931 g/L, and, K-I = 6.932 g/L by nonlinear regression analysis. It was reported that pectin lyase enzymes exhibited peak activity at 50 degrees C and pH 8. Finally, response surface methodology (RSM) was utilized to optimize pH, concentrations of ammonium sulfate, and pectin, which were chosen as independent variables. The interactions between these variables were also examined. According to RSM, the optimum values of the parameters to achieve a maximum pectin lyase activity of 35.62 U/mL were determined to be pH 7.97, 1.25% (w/v) pectin concentration, and 0.25% (w/v) (NH4)(2)SO4 concentration.