2.4. Hydrodynamic experiments: tracer tests at different stages of AD
After the washing process, 10 L of 0.1 mol L−1 NaCl tracer solution was injected at ACY1215 constant flow rate of 1.6 L min−1 into each reactor. Then, two pore volumes of water were injected to elute the tracer and obtain a constant conductivity signal. Effluent conductivity was recorded over the course of each experiment and then converted to tracer concentration. Tracer breakthrough curves, BTCs, were determined by plotting the relative tracer concentration (C/C0) versus the taxonomy relative eluted volume (V/V0) at the reactor outlet, with C: time dependent concentration at the reactor outlet; C0: initial tracer concentration injected versus the relative eluted volume; V: time dependent volume; V0: total water volume in the reactor.
2.5. Analysis of elution curves and modeling
Zero and first order temporal moments of the solute concentration distributions (BTCs) were used to estimate tracer mass balance and retardation factors:equation(5)μ0=∫0+∞C(t)C0dt,μ1=∫0+∞tC(t)C0dt