AEROBIC GRANULES FOR WASTEWATER AMMONIA NITROGEN AND NITRATE REMOVAL

Abstract

For 203 days, the performance of an aerobic granules laboratory-scale reactor for the removal of COD, ammonia and nitrate under different conditions was evaluated. The experiment was divided in four stages: 1) initially aerobic for the formation of the granules (0.36 kgCOD/kgTSS∙d); 2) aerobic/anoxic under a high organic load (0.43 kgCOD/kgTSS∙d); 3) aerobic/anoxic under a low organic load (0.26 kgCOD/kgTSS∙d) and 4) aerobic under a very low organic load (0.17 kgCOD/kgTSS∙d). The results show that under higher organic loading rate and aerobic conditions (stage 1) a dissolved COD removal of 88% was obtained. Under organic loadings between 0.15 and 0.2 kgCOD/kgTSS∙d (stage 2) the dissolved COD removal decreased near to 80%. The ammonia nitrogen removal resulted inversely proportional to the ammonia-loading rate. With loads close to 0.01 kgNH4-N/m3∙d, ammonium removal of approximately 90% was obtained and with loads near 0.04 kgNH4-N/m3∙d the nitrogen removal decreased to 10%. Under alternating aerobic/anoxic conditions, with organic loads from 0.26 and 0.43 kgCOD/kgTSS∙d, complete denitrification without the addition of an external carbon source was not achieved.

Key Words: Aerobic granules, denitrification, nitrification, sequential airlift reactor.