Effluent samples were collected on the same day and at the
same time, as well as collected from each bed every two and four
days in a 1-L amber glass bottles, which were transported refrigerated
(4 C) to the laboratory. The samples were immediately
analyzed to determine the reduction in concentration of the
general parameters, i.e., COD, ammonia-N (NH4þ-N), nitrate (NO3-
N), and total phosphorus (TP). General parameters were analyzed
using spectrophotometer (HACH-DR3800, USA) in accordance with
the standard methods (Standard Methods for Examination ofWater
and Wastewater - APHA, 1989). Temperature, dissolved oxygen
(DO), pH value and conductivity were measured using Multi-
Parameter Digital Meter (HACH e HQ40d, USA) directly.