Authors: Gonçalves, M.; Bastos, E.; Alves, M.M.; Correia, J.P.; Marques, I.P.

Source: Environmental Technology, Volume 27, Number 11, November 2006 , pp. 1289-1295(7)

Publisher: Taylor and Francis Ltd

Abstract:

Electrochemical pre-treatment of oleate on anaerobic digestion was investigated using two anaerobic filters (AF and AFm) working, respectively, with increasing concentrations of electrochemically pre-treated oleate and oleate. Influents containing 25% and 50% of chemical oxygen demand (COD) of these substrates did not cause relevant alterations in either digester's performance. Comparatively, the pre-treated oleate unit (AF) showed a higher gas production but a lower COD removal than AFm (2.0 vs 1.5 m³ CH₄ m⁻³ d⁻¹; 76-85 vs 91-93% COD removal). The raised AFm COD removal together with the larger proportion of VSS in its effluent than in AF (5.69 vs 0.26 kg m⁻³) indicate that the biomass washout can be a consequence of the encapsulated solids by lipidic compounds that were not fairly degraded. Further increases of oleate in AFm feed (75 and 100% COD) led to decreases of biogas production to half and COD removal from values higher than 90% to 83-75%. The simultaneous increase of effluent VSS concentrations to 10-12 kg m⁻³ emphasizes the oleate negative effect. The use of pre-treated oleate as the only carbon source did not influence negatively the AF behaviour in terms of methane production. COD removal was maintained at values higher than 80% and the effluent VSS at low concentrations (0.15 kg m⁻³). The significantly higher methane yield achieved by AF than AFm indicates a higher accumulation of oleate than pre-treated oleate. Therefore, electrochemical process stands for a suitable pre-treatment for lipid rich effluents, allowing the application of higher organic loads keeping a higher methane yield.

Keywords: ELECTROOXIDATION OF OLEIC ACID; ANAEROBIC TREATMENT; LIPIDS; OLEATE; ANAEROBIC FILTER

Document Type: Research article

Publication date: 2006-11-01

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