Development And Utilization Of Aerobic Granules For Treating Low Strength Domestic Wastewater
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Date
2012-03
Authors
Peyong, Yet Nee
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Aerobic granules were developed using low strength wastewater in sequencing batch
reactor (SBR). The changes in microbial morphologies and structures of aerobic
granules under different organic loading rates (OLR) and their tolerance towards free
ammonia (FA) and free nitrous acid (FNA) were studied. The development of
aerobic granules was carried out in 3 stages. In the first stage, aerobic granules were
cultivated using low strength synthetic domestic wastewater with OLR of 1.2
kg/m3day. Stable aerobic granules were formed after 60 days operation with an
average granule size of 2.2 mm. The mixed liquor suspended solid (MLSS)
concentration of aerobic granules was 1.2 g/L with the sludge volume index (SVI)
value of 78 mL/g and minimal settling velocity of 22.5 m/h. Subsequently, in the
second stage, low strength real domestic wastewater with OLR of 0.13 kg/m3day was
fed to the reactor. After 14 days operation, a mixture of compacted aerobic granules
and small debris resulted from the breakage of granules was observed. Biomass
concentration and settle ability were reduced to 0.17 g/L and 165 mL/g, respectively.
In the third stage, external carbon source was added to the domestic wastewater in
order to increase the OLR by 0.6 kg/m3day. Under this new condition, more aerobic
granules with excellent settle ability were formed with an average size of 2.0 mm,
SVI of 88 mL/g and maximum settling velocity of 110 m/h. Microscopic images
showed that different microbial morphologies and structures were found in aerobic
granules at the three different stages. The inhibitory studies of FA on the activity of
aerobic granules reveals that FA at a concentration up to 36.9 mg NH3-N/L did not
inhibit the specific oxygen uptake rate (SOUR) of aerobic granules. However, FNA
started to inhibit the SOUR at 0.015 mg HNO2-N/L and completely stopped the
oxygen consumption at around 0.134 mg/L HNO2-N/L. FNA inhibition of aerobic
granules was found to be reversible.
Description
Keywords
Aerobic granules were developed using , low strength wastewater in sequencing batch reactor