Kinetic study of compost liquor nitrification

Abstract

This study is a first kinetic approach about the compost liquor treatment by activated sludge. This industrial wastewater is highly loaded in organic and nitrogen compounds (COD≈12,000 mg L−1 and NH4+-N≈4,000 mg L−1). The possibility of its treatment in an urban WWTP is studied measuring ammonia oxidation rate with non-acclimated sludge to the industrial effluent. Compost liquor appears as an inhibitor substrate. The ammonia oxidation rate can be modelled by the Haldane model: UMAX=0.180 d−1, KS=12.0 mgN.L−1 and KI=26.0 mgN.L−1. The ammonia oxidation rate also follows for a synthetic substrate which has the same pollutant load as the real substrate. In this case, the ammonia oxidation rate can be modelled by the Monod model: UMAX=0.073 d−1 and KS=4.3 mgN.L−1. This result confirms that the ammonia oxidising bacteria are inhibited by the real wastewater. The following-up of nitrate production shows also the inhibition of nitrite oxidising bacteria. The compost liquor treatment seems not possible in an urban WWTP (<50,000 p.e.). That’s why a specific WWTP is recommended and an acclimation step of activated sludge is essential.