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4.12.2. Radiotracer experiment(a) Laboratory batch sorption experimentsFor the sorption experiments, three representative wastewater samples were selected at differentstages of the digestion process at the anaerobic digestion unit of the WWTP of the sugar factory basedon a two phase's anaerobic digestion employing three hybrid reactors.The main advantages of this technology are, the reduction up to 90% of the effluent pollutioncharge, the production of biogas and the attain of sludge that constitutes an excellent fertilizer.Nevertheless, in order to generalize and widespread this technology to other sugar factory, first of all,designs and process modeling must optimize plant operation.Figure 79 gives the scheme of an industrial unit.FIG.79. Scheme of the industrial unit.W1 corresponds to the effluent that entry the unit; W2, the fluid circulating trough digester D 2and W3 the fluid that exit the unit. The flow is pumping from D2 to D3 whereas it is going by gravityfrom D 1 to D 3 and from D 2 to the outlet (Fig.79).A modification of batch experiment was used to evaluate the possible sorption of 99m TcO 4 - . Thefirst step of the experiment was the pre-heated of wastewaters to ~37 o C and the equilibration to theconditions founded during anaerobic digestion. For each sorption experiment, 200 mL of thewastewaters and 1 mL of the stock 99m TcO 4 - solution (42,3 MBq/mL) were filled into polyethylenebottles. Another bottle filled with 200 mL of distilled water and 1 mL of 99m TcO 4 - was used as blank.Bottles were hermetically sealed by tightly fitting stoppers and shake up at ~150 oscillations perminute. After certain periods of time (1, 2, 4, 8, 16, 24 and 48 hours) the wastewaters were centrifugedduring 10 minutes and filtrated through membrane filters of 0.45 μm pore size (Millipore). Threeindependent experiments were carried out with each wastewater and for each time and one furtherexperiment with the blank to check for wall adsorption. 1 mL of filtering solution was withdrawn forradioactive counting (