Combining submerged membrane technology with anaerobic and ...

Chapter 7Table 7.1. Characteristics of PACParameter Unit PAC CX1Mean particle size µm 30Specific surface m 2·g -1 1000Methylene blue number mL·100g -1 11Iodine number cg·g -1 1007.3.4. Analytical methodsMixed liquor volatile total solids (MLVTS) and MLTS were determined according tothe German standard DIN 38409-1 using a porcelain melting pot. Concentration ofchemical oxygen demand (COD), total nitrogen (TN), total phosphorous, organic acids(OA) and total organic carbon (TOC) were measured with selective Hach-Lange tests.Total alkalinity (TA), partial alkalinity (PA) and intermediate alkalinity (IA) were determinedfollowing the Standard Methods for the Examination of Water and Wastewater (APHA-AWWA-WPCF, 1998). Concentration of methane, CO 2 and nitrogen were measured usinga gas chromatograph (SRI-Instruments).With respect to the membrane operation, transmembrane pressure (TMP) andpermeability were measured continuously. The difference in TOC concentration betweenthe mixed liquor after filtration through a 0.45 µm nitrocellulose membrane filters (HA,Millipore) and the permeate was assigned to the colloidal fraction of biopolymer clusters(cBPC) in the liquid phase of the sludge suspension (Sun et al., 2008). The analysismethod used for the determination of the transparent exopolymer particles (TEP)concentration (de la Torre et al., 2008) is based on the protocol developed for TEPquantification in sea water (Arruda et al., 2004). The critical flux was determined accordingto the modified flux-step method proposed by van der Marel et al. (2009). The criterionemployed was that the increment of transmembrane pressure (TMP) with respect to timewas higher than 10 Pa·min -1 (Le-Clech et al., 2003).The specific resistance to filtration of a sludge sample was determined by a deadendfilterability test. The test was conducted at 25ºC in a 200-mL pressurized cylinder(Model Sartorius SM 16249) using a 0.2 µm flat-sheet cellulose acetate membrane filterwith a diameter of 47 mm (12587-47-N Sartorius). Using the Carman-Kozeny equation tocalculate the pressure drop of a fluid flowing through a packed bed of solids in laminar flow178