Simultaneous removal of carbon and nutrients in single upflow aerobic/anoxic sludge bed bioreactor

The simultaneous removal of carbon, nitrogen, and phosphorus (CNP) nutrients in a single bioreactor is highly significant for energy consumption and controlling the reactor volume.

The removal of nutrients is dependent on the ratio of biochemical oxygen demand to chemical oxygen demand (BOD5/COD). Thus, this study investigated the treatment of an industrial estate wastewater with low BOD5/COD ratio in an upflow aerobic/anoxic sludge bed (UAASB) bioreactor, with an intermittent aeration and discharge regime.

A hydraulic retention time (HRT) of 12–36 h and aeration time of 40–60 min/h were selected as the operating variables to analyse, optimise, and model the process. To analyse the process, 13 dependent parameters were studied as the process responses.

From the results, it was found that increasing HRT leads to decreasing CNP removal efficiencies. However, by increasing the BOD5 fraction of the feed, the total COD (TCOD), slowly biodegradable COD (sbCOD), readily biodegradable COD (rbCOD), total nitrogen (TN), and total phosphorus (TP) removal efficiencies were increased significantly.

The population of heterotrophic, nitrifying, and denitrifying bacteria showed good agreement with the results obtained for TCOD and TN removal. The optimum conditions were determined as HRT of 12–15 h and aeration time of 40–60 min/h.

Water Research, Volume 46, Issue 15, 1 October 2012, Pages 4587–4598.