The effect of aeration rate on nutrient
removal from slaughterhouse wastewater was examined
in two 10-L laboratory-scale sequencing batch reactors
(SBRs—SBR1 and SBR2) operated at ambient temperature. The contaminants in the slaughterhouse
wastewater had average concentrations of 4,000 mg
chemical oxygen demand (COD) L−1
, 350 mg total
nitrogen (TN) L−1 and 26 mg total phosphorus (TP)
L−1
. The duration of a complete SBR operation cycle
was 8 h and comprised four operational phases: fill
(7 min), react (393 min), settle (30 min) and draw/idle
(50 min). During the react phase, the reactors were
intermittently aerated four times at 50-min intervals,
50 min each time. DO, pH and oxidation–reduction
potential (ORP) in the reactors were real-time monitored. Four aeration rates—0.2 L air min−1 in SBR1 for
70 days, 0.4 L air min−1 in SBR1 for 50 days, 0.8 L air
min−1 in SBR2 for 120 days and 1.2 L air min−1 in
SBR1 for 110 days—were tested. When the aeration
rate was 0.2 L air min−1
, the SBR was continuously
anaerobic. When the aeration rate was 0.4 L air min−1
,
COD and TP removals were 90% but TN removal was
only 34%. When the aeration rates were 0.8 and 1.2 L
air min−1
, average effluent concentrations were 115 mg
COD L−1
, 19 mg TN L−1 and 0.7 mg TP L−1
, giving
COD, TN and TP removals of 97%, 95% and 97%,
respectively. It was found that partial nitrification
followed by denitrification occurred in the intermittently aerated SBR systems.