A Two-Stage SBR Process for Removal of Organic Substrate and Nitrogen via Nitrite-Type Nitrification–Denitrification

Abstract

A two-stage SBR process (TSSBR) was applied for the treatment of wastewater with high strength COD and nitrogen. Most of organic substrate was removed in the first stage SBR reactor (SBR1) under the aerobic condition. Subsequently the second stage SBR reactor (SBR2) firstly was operated under the aerobic condition for simultaneous nitrite-type nitrification and removal of a small amount of residual organic substrate. Nitrification was controlled to the nitrite-type nitrification. Then denitrification in which the wastewater was used as external carbon sources occurred in SBR2 under the anoxic condition. The experimental results indicated that two kinds of biomass with the different function were cultured in a TSSBR system, which was beneficial to increase the proportion of Nitrosomonas in the microorganism of SBR2. It avoided the inhibition of the high organic loading to nitrification and C/N was not the limiting factor affecting the nitrogen removal efficiency. The rate of COD degradation and nitrification was improved, 8 kg COD/kg MLSS/d and 0.25 kg -N/kg MLSS/d, respectively. The final effluent COD concentration further reduced because the organic substrate that was left in SBR1 effluent was removed in SBR2. Consequently, when compared to a single SBR process, a two-stage SBR (TSSBR) not only improved the treatment efficiency, but also saved the operational cost.

Keywords:

• A two-stage SBR process (TSSBR)
• Nitrite-type nitrification
• Denitrification

Acknowledgments

This research was one of the significant projects subsidized by China National Nature Science Foundation (50138010) and was supported by “863” key project of China (2003AA601010, 2003A06).