Combining submerged membrane technology with anaerobic and ...

g DOC adsorbed / g PACChapter 77.4.2. Fed-batch experiments to study the optimum PAC dosage in theAnMBRDifferent PAC and GAC were tested (data not shown) in order to select the bestoption. Contrary to the affirmation stated in the introduction supported by some authors(Barker and Stuckey, 1999; Akram and Stuckey, 2008), GAC did exhibit good OAadsorption rates, similar than those obtained with the PAC tested.In figure 7.3 can be observed the adsorption isotherm of the selected PAC. This wasthe best of the PAC and GAC tested in terms of adsorption capacity. The adsorptioncapacity of the PAC was determined by adding different PAC doses to a certain volume ofpermeate and measuring the residual dissolved organic carbon concentration (DOC) after24 h. The selected PAC presented a good adsorption capacity, in the range of thosereported for the adsorption of organic compounds in activated carbon used in this kind ofapplications (BREF, 2003).0.250.200.150.100.050.000 250 500 750 1000DOC (mg·L -1 )Figure 7.3. DOC Adsorption isotherm of the selected PAC.The first experiments with PAC were performed using the permeate from the AnMBRin order to determine the adsorption capacity of possible foulants such as BPC or TEP aswell as the adsorption capacity of organic acids in case of shock load of the reactor. Ascan be observed in figure 7.4, all the studied parameters presented a very good removalwith PAC dosages of 1.5 g·L -1 . It has to be taken into account that the adsorption of CODwas not the objective of PAC dosage, but the improvement of filterability and the possiblemitigation of VFAs accumulation during a shock load event. Therefore, the dosage ofhigher amounts of PAC than 1.5 g·L -1 was not justified considering the adsorption of BPC,TEP and OA. In figure 7.4b the accumulation of organic acids in the flask without PAC can182