Latest revision as of 10:58, 19 June 2020

Abstract

The aim of this research is to identify the operational conditions and performance of low cost tubular digesters producing biogas from the slaughterhouse wastewater treatment. Three full scale sequenced tubular digesters (of more than ${\displaystyle 8m^{3}}$ each), operating in a slaughterhouse in Cochabamba (Bolivia), have been monitored during one year. The Organic Load Rate (OLR) varied from ${\displaystyle 0.04}$ to ${\displaystyle 1.13kgSV/m^{3}d}$ (${\displaystyle 0.04-1.07kgCOD/m^{3}d}$), and the Hydraulic Retention Time (HRT) from ${\displaystyle 3.2}$ to ${\displaystyle 87.4}$ days. The passive solar heating design considered drove the slurry temperature to ${\displaystyle 27^{o}C}$, ${\displaystyle 8^{o}C}$ more than mean ambient temperature. The first digester has been filled with soda bottle plastic rings in order to increase the internal effective surface and evaluate, obtaining that an increment in ${\displaystyle 67\%}$ of the internal effective surface, more than doubles the biogas production and enables higher OLRs. A Biogas Production Rate (BPR) peak of ${\displaystyle 0.2m^{3}/m^{3}d}$ was observed for ${\displaystyle OLR=0.37kgSV/m^{3}d}$, ${\displaystyle HRT=9.7d}$ and Specific Biogas Production (SBP) ${\displaystyle =0.55m^{3}/kgSV}$. COD removal achieves values above ${\displaystyle 70\%}$ from ${\displaystyle HRT>19}$ d. A comparison with other anaerobic digestion technologies demonstrates that low cost tubular digesters with biofilm carriers, are competitive for ${\displaystyle OLR<0.5}$ kg ${\displaystyle COD/m^{3}d}$ of biogas production, and for ${\displaystyle 0.25kgCOD/m^{3}d}$, when the focus is on COD removal.