Suwasa Kantawanichkul and Suparurk Wannasri

pp. 599 - 603

Abstract

The study was carried out in 4 concrete beds: two vertical subsurface flow beds (dimension of 1x1.4 x 0.6 m³
) and two
horizontal subsurface flow beds (dimension of 0.6 x 2.3x 0.6 m³
) planted with Cyperus alternifolius L. Under the average
wastewater temperature of 27°C, the hydraulic loading rates (HLR) were varied from 5 to 20 cm/d in order to obtain the
optimum operating conditions and compare the removal efficiency. The wastewater was intermittently fed into the vertical
subsurface flow beds (5 minutes on and 55 minutes off), and continuously into the horizontal subsurface flow beds. The
maximum removal efficiencies were found at the lowest hydraulic loading rate for both systems. The horizontal subsurface
flow system had a higher removal rate than the vertical subsurface flow system in terms of COD (the removal rates at 5-20
cm/d were 9.6-33.9 g/m²
.d). The vertical subsurface flow system showed higher removal efficiency for TKN and NH4⁺-N, in
every hydraulic loading rate and the removal rates for TKN and NH4⁺-N were 0.4-1.1 g/m²
.d, respectively. Furthermore, it was
found that the uptake of N by plants in the horizontal flow system was higher than in the vertical flow system for every
hydraulic loading rate (HLR) but the loss of N via adsorption/denitrification was higher in the vertical flow system than in
the horizontal flow system, at 20 cm/d HLR. The removal rate constants in the horizontal subsurface flow system for COD and
NH4⁺-N were 0.0166 and 0.0188 m/d and 0.0204 and 0.0287 m/d for the vertical subsurface flow system, respectively