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A Sequencing Batch Reactor Achieving Enhanced Nitrogen Removal from Municipal Wastewaters through Bypassing Nitrite Oxidation - a Pilot Scale Study

Gerasimos Lyberatos, Michael Kornaros, and Constantina Marazioti. Chemical Engineering, University of Patras, 1 Karatheodory st., Panepistimioupoli, Patras, Greece

Sequencing batch reactors are usually preferred as small wastewater treatment systems. We have demonstrated that using frequent enough switching between aerobic and anoxic conditions, it is possible to by-pass the second step of nitrification. Ammonia is oxidized to nitrite and then is subsequently reduced to nitrogen gas, without producing nitrate. The reason is that nitrite oxidizers have a long recuperation time following an anoxic phase. This type of operation leads to reduced capital and operating costs. In this work we present the results of a pilot-scale SBR built at the municipality of Patras, Greece operated in both 8-hour and 12-hour cycles. It is demonstrated that three pairs of aerobic/anoxic phases with a relative duration of 1:2 (8-hour cycle) and 2:3 (12-hour cycle) secures the desired by-pass of nitrate production.