Combining submerged membrane technology with anaerobic and ...

Chapter 6Table 6.1. Main operational conditions of the bioreactor during the different periods.Period days Environment 1 R 2 CH 4 stripping 3I 0-84 Aerobic 1.0 noII 85-120 Anoxic 3.0 4 noIII 121-150 Anoxic 1.0 noIV 151-169 Anoxic 1.0 yesV 170-198 Anoxic 0.5-1.0 noVI 199-233 Anoxic 1.5-2.0 no1 In the first MBR chamber2 Internal recirculation ratio in the MBR3 Methane was stripped off from UASB effluent before entering the first MBR chamber4 From days 85 to 91 the recirculation rate was fixed at R=16.3.2. Analytical methodsTemperature, pH, alkalinity and the concentrations of dissolved oxygen, mixed liquorvolatile suspended solids (MLVSS), total and soluble chemical oxygen demand (COD),nitrite, nitrate and ammonia were determined according to the Standard Methods for theExamination of Water and Wastewater (APHA-AWWA-WPCF, 1998). Dissolved totalnitrogen (DTN) was determined with a DN 1900 analyser (Rosemount, Dohrmann). DTNwas referred to the sum of the measured nitrogen ions and soluble organic nitrogen.Volatile fatty acids (VFA) (i-butyric, n-butyric, i-valeric and n-valeric) were analyzed by gaschromatography (HP, 5890A) equipped with a flame ionization detector (HP, 7673A).Biogas production was measured using a Milli GasCounter MGC-10 (Ritter) and itscomposition was measured in a gas chromatograph HP 5890 Series II with the column ofPorapack Q 80/100 2m x 1/8” (SUPELCO).Remaining methane dissolved in the liquid phase was estimated by Henry´s law.Methane is characterized by a Henry constant of 1.5·10 -3 mol· L -1 ·atm -1 at 25ºC (Sander,1999). 300 mL of sample was hand-shaked in a 500 mL Erlenmeyer. After three minutes ofshaking gas phase was analyzed in the gas chromatograph.The difference in DOC concentration between the sludge mixture after filtrationthrough a 0.45 µm nitrocellulose membrane filters (HA, Millipore) and the permeate wasassigned to the colloidal fraction of biopolymer clusters (cBPC) in the liquid phase of the154