A novel horizontal-flow biofilm
reactor (HFBR) and a novel alternating pumped-flow biofilm reactor (APFBR) were
investigated for the removal of nutrients from domestic–strength synthetic
wastewater (DSWW) in the laboratory and from municipal wastewater on-site. The
HFBR technology is suitable for the removal of organic carbon and nitrogen in
wastewaters from single houses while the APFBR technology is suitable for the
removal of organic carbon, nitrogen and phosphorus from municipal wastewaters
from villages and towns. The HFBR comprised a stack of 60 horizontal polystyrene
sheets along which the wastewater flowed, over and back on alternate sheets,
and down through the stack. The laboratory HFBR was fed with DSWW for 10
minutes each hour at a footprint loading rate of 418.4 L/m2.day,
which was applied at Sheet 1 (67 % of the flow), and at Sheet 38 (33 % of the
flow) to facilitate denitrification. Removals of 85.7 % chemical oxygen demand
(COD), 97.4 % 5-day biochemical oxygen demand (BOD5) and 61.7 % total
nitrogen (TN) were recorded for the HFBR. The laboratory APFBR comprised two 16.5 L reactor tanks (Reactors 1 and 2) with
two identical biofilm modules of vertical tubular plastic media, one in each
tank with a surface area of 2 m2. The APFBR operating cycle had
fill, anaerobic, aerobic and draw phases, in sequence. During the fill phase,
Reactor 1 was half-filled with DSWW. In the anaerobic phase, most of the
phosphorus release occurred from the submerged biofilm in Reactor 1. In the extended
aerobic phase, the wastewater was circulated by pumps between Reactors 1 and 2,
resulting in denitrification at the start of this phase due to low oxygen
concentrations, followed by nitrification and luxury uptake of phosphorus when
oxygen concentrations increased. During the draw phase, Reactor 2 was
half-emptied of the treated water. At the COD, TN and total phosphorus (TP)
loading rates on the total biofilm area of 3.20 g COD, 0.33 g TN and 0.06 g TP /m2
.d, removals were 97% COD, 85% TN and 92% TP. Preliminary on-site studies
confirmed the efficacy of the HFBR and APFBR technologies.