From table 2, we can see that the content of TP in the network decreases a little with the extend of hydraulic retention time.
This may be due to the two kinds of cause, firstly, The content of TP was consumed constantly by free bacteria and biofilm ;Secondly, TP were adsorbed by particles in the network and biofilm causing the content of TP to reduce.
But in individual sampling points TP increase, this might be relevant to the particles which were formed by biofilm desorption.