Combining submerged membrane technology with anaerobic and ...

Chapter 2alkalinity (IA), which is the difference between TA (titration till pH 4.3) and PA, represents –in an approximate form – the alkalinity due to the VFA concentration (Ripley et al., 1986).Various authors established that the relation between IA and TA is an adequateparameter of the anaerobic digestion process, and should not exceed the value of 0.3(Ripley et al., 1986; Switzembaum et al., 1990; Soto et al., 1993; Wentzel et al., 1994) toavoid the accumulation of the VFA in the system.Determination of the alkalinity is performed according to the method 2320 of APHA-AWWA-WPCF (1998) and consists of the titration of the centrifuged or filtrated sample withH 2SO 4 (with titrated normality) at two points of pH: 5.75 (which corresponds to the partialalkalinity) and 4.30 (which corresponds to the total alkalinity).Values of the alkalinity are expressed as mg CaCO 3·L -1 and are calculated as follows(APHA-AWWA-WPCF, 1998):being:V: volume of the sample (25 mL)N: normality of H 2SO 4A: volume of H 2SO 4 (mL) necessary to reach pH 5.75B: volume de H 2SO 4 (mL) necessary to reach pH 4.32.2. Solid phase: Sludge characterisationeq. 2.4eq. 2.52.2.1. Mixed liquor total suspended solids (MLTSS) and mixed liquor volatilesuspended solids (MLVSS) concentrationSolids present in water can be organic or inorganic. Mixed liquor total solids (MLTS)is the term applied to the material residue left in the vessel after evaporation of a sampleand its subsequent drying in an oven at a defined temperature. MLTS includes mixedliquor total suspended solids (MLTSS), the portion of MLTS retained by a filter, anddissolved solids, the portion that passes thorough the filter. Mixed liquor volatile solids(MLVS) and mixed liquor volatile suspended solids (MLVSS) are the fraction of MLTS andMLTSS, respectively that are loss on ignition at a specified temperature. The determinationof MLVSS concentration is especially useful in the control of wastewater treatment plant74