Combining submerged membrane technology with anaerobic and ...

Chapter 6mL of suspended biomass (2 gMLVSS·L -1 ) and 20 plastic carriers Kaldnes K3 (40% ofapparent volume). In the other the four bottles were filled with 50 plastic carriers KaldnesK3 and 400 mL of phosphate buffer (KH 2PO 4: 0.143 g·L -1 ; K 2HPO 4: 0.740 g·L -1 ).Both biofilm and suspended biomass were taken from the anoxic chamber of thereactor, settled for at least 12 h and washed three times with phosphate buffer in order toassure the absence of organic matter or nitrogen. The absence of any soluble carbonsource in the supernatant was confirmed by COD measurement. After inoculation, theflasks were flushed for 5 min using nitrogen or methane depending on the conditions (table6.2), to guarantee anaerobic atmosphere.5 mL of NaC 2H 3O 2·3H 2O 0.9M were spiked as a carbon source in the correspondingflasks (table 6.2). 1 mL of KNO 3 0.86M was spiked to each bottle at the beginning of theexperiment.The flasks were incubated at 25 ºC and stirred in a shaker at 150 rpm during fivehours. 5 mL liquid samples were taken each hour with a syringe through a septum andfiltered through 0.45 µm nitrocellulose membrane filters (HA, Millipore). All control assayswere performed in duplicate. These batch experiments were carried out during period VIand thus the biomass conditions were specific from that period (table 6.1).Table 6.2. Denitrification batch experiments conditionsFlask Headspace Carbon SourceBlank N 2 NoneMethane CH 4 CH 4Acetate N 2 AcetateMethane + Acetate CH 4 Acetate + CH 46.3.4. Determination of methane and oxygen transfer in the first MBRchamberThe methane emissions to the environment in the first (anoxic) chamber wereestimated by closing the headspace with parafilm (Pechiney Plastic Packaging, USA) andmonitoring the methane build-up in this headspace during 3 hours. Samples of 1 mL weretaken in duplicate each 30 minutes and its composition was measured in a gaschromatograph HP 5890 Series II with the column of Porapack Q 80/100 2m x 1/8”(SUPELCO). The flow of methane desorbed was calculated, according to equation 6.3, by156