Combining submerged membrane technology with anaerobic and ...

Chapter 22.2.3. Sludge volumetric indexThe sludge volumetric index (SVI) determination is defined in the Standard Methodsfor the Examination of Water and Wastewater (APHA-AWWA-WPCF, 1998) as the volumein mL occupied by 1 g of a suspension after 30 min settling.2.2.4. Sludge settling rateThe sludge settling rate (SSR) was determined by measuring the velocity ofsedimentation of the mixed liquor (1 g·L -1 ) in a 100 mL measuring cylinder.2.3. Gas phaseTo measure biogas composition a gas chromatograph HP 5890 Series II with thecolumn of Porapack Q 80/100 2m x 1/8” (SUPELCO) is used. 1 mL of well-mixed sampleshould be injected through the septum at the following conditions: oven temperature(column) at 35 °C; injector and the detector temperature at 110 °C. The obtained peakscorrespond to the percentage of the N 2, CH 4, CO 2 and H 2S content in the sample. Biogasproduction was measured using a Milli GasCounter MGC-10 (Ritter, Germany), whichbasically consists in a tilting body inside a container with a special packing liquid. Theentrance of gas bubbles led the tilting body to change its position. Each change is countedwith a magnet and a counter and the internal calibration give the gas flow in the display.2.4. Membrane performance2.4.1. Flux and permeabilityMembrane flux can be calculated as:where:J: flux expressed in L·m -2 ∙h -1 ,Q: flow expressed in L·h -1 ,A: membrane area expressed in m 2 .Therefore, permeability can be calculated as:eq. 2.676