Aspects of Expanded Bed Nitrification Including Treatment of Oil Refinery Wastewaters

Akhidime, Iduma Devine (2009) Aspects of Expanded Bed Nitrification Including Treatment of Oil Refinery Wastewaters. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

The original aim of this study was to investigate the nitrification of oil refinery wastewater using the novel expanded bed technology. Nitrification is the oxidation of ammonia to nitrate by the nitrifying bacteria and is an important part of wastewater treatment processes (Gray, 1989; Nielsen et al., 2009). This study involved the establishment of a lab-scale expanded bed bioreactor for the nitrification process. However, initial samples of oil refinery wastewaters obtained from the industry effluent showed low concentrations of ammonia (below 2 mg L-1 ); much lower than the concentration reported in the literature (e.g. Xianling et al., 2005 reported concentrations of 56 – 125 mg L -1 NH4 + -N). Therefore, synthetic wastewater employed in nitrification processes from literature was used to establish the lab-scale expanded bed bioreactor. Utilizing synthetic wastewater enabled the study of the bioreactor processes in controlled conditions before exposing the nitrifying community to oil refinery wastewaters. The investigations carried out to broaden the understanding of the expanded bed technology and of the nitrifying bacteria involved in the process included methods to determine the biomass concentration, the determination of the maximum and specific nitrification rates and the measurement of the biofilm thickness of the nitrifying biofilms. The ammonia and nitrite oxidizers of the 22 biofilms were also quantified using Fluorescent in situ hybridization (FISH) techniques (Nielsen et al., 2009). The study therefore included different aspects of expanded bed nitrification with a focus on the influence of biofilm thickness on nitrification process and the effect of oil refinery wastewater treatment on the nitrifying biofilm.