Hi,
This is a bi-exponential or double-first-order in parallel
(DFOP) model: (C = C0(ge−k1t + [1 − g]e−k2t))
where C is the concentration at time t, C0 is the initial
concentration at time 0, k1 values are degradation rate constants at compartment 1 (rapid phase) and k2 is for compartment 2 (slow phase), g is
the fraction of C0 applied to compartment 1.
Often the value should come k1>k2, which means rate is higher in rapid phase.I only saw one article who obtained k2>k1. I am also getting k2>k1, actually means show degradation has higher rate than rapid degradation. On the other hand, I am getting g value 60% which means ~60% of initial concentration is being degraded at compartment 1 i.e. in rapid phase. Is this a contradictory? Could anyone please share your experience and expertise here? it was a biodegradation of PAH in soil and this model is fitting with very good-fitting than single first-order, except this confusing explanation. Thank you
I generally apply this equation to the waste water degradation to calculate the Biological Demand in Oxgen (BDO). The first compartment (rapid phase) concern the water Carbon pollution degradation during about 15 days and the second one (slow phase) concern the water Nitrogen pollution degradation during about 6 days. The coefficient k2 >k1 means that Nitrogen degradation process has higher rate and I agree with tour interpretation on this point. The C0 value refers only to your own conditions and do not interfer in the degradation kinetic
If I understand correctly, you might be putting too much emphasis on the "meaning" of the coefficients. You can switch the values of k1 and k2 if you also switch the values of g and (1-g), so either compartment can be the compartment 1.
Thank you very much Dr Salvatore and Dr Tarik for sharing your expertise.
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