Nitrogen and Organic Matter Removal from Slaughterhouse Wastewater in a Lab-Scale Aerobic Fixed-Film Bioreactor

Abstract

This paper presents the behaviour of a laboratory scale Aerobic Fixed-Film Bioreactor (Ae-FFB) with arranged media including its initial start up phase. It examines the viability of the Ae-FFB to remove nitrogen and organic matter from poultry slaughterhouse wastewater. After 12 days of operation while rapid growth of nitrifying bacteria took place, nitrogen and organic loading rates were increased progressively by up to 0.2 kg TKN m-3 day-1 and 0.8 kg COD m-3 day-1 respectively, reaching nitrogen and organic matter removal efficiencies of up to 92%. Heterotrophic bacteria, mainly placed in the suspended biomass accumulated at the bottom of the reactor, were found to be competing with nitrifying bacteria for oxygen, which limited nitrification efficiency. Despite operating with dissolved oxygen concentrations of around 3.5 mg l-1, an important contribution of the denitrification process was observed that removed up to 50% of oxidised nitrogen, depending on the availability of biodegradable organic matter.