The C/N ratio of the RAS effluent was obtained by dividing the
concentrations of total organic carbon (TOC) by TN. The TOC concentration was measured by the summation of the concentrations
of particulate organic carbon (POC) and dissolved organic carbon
(DOC) (Gao et al., 2012). POC was collected using pre-combusted
(450
◦
C for 2 h) and pre-weighted filters (Whatman GF/F) and
exposed to HCl fumes (overnight) to purge the inorganic carbon.
It was then dried, weighed and sent for carbon element analysis
(Elementar vario MAX CNS, Elementar Analysensysteme Co., Ltd