Performance of an Anaerobic Reactor Treating Poultry Abattoir Wastewater with High Fat Content After Enzymatic Hydrolysis

Abstract

Abstract

Effects of a lipase-rich solid enzymatic preparation produced by the fungus Penicillium restrictum in solid-state fermentation were evaluated in up-flow anaerobic sludge blanket reactors treating poultry slaughterhouse wastewater with 800 mg oil and grease (O&G)/L. Reactors operated at 30°C under two organic load rates (3.9 and 7.3 kg chemical oxygen demand [COD]/m³·day). The reactor fed with previously hydrolyzed wastewater showed higher methane production values, as well as high COD removal levels (367 and 882 mL CH₄/day and 90.4% and 93.5% at 1st and 2nd regimen, respectively). In the reactor fed with raw wastewater, 178 and 642 mL CH₄/day and 89.8% and 91.0% of COD removal were verified at 1st and 2nd regimen, respectively. Although differences are not so significant in terms of COD removal and biogas production, the greatest impact on the implementation of solid enzymatic preparation in the prehydrolysis step was the better operating conditions: in the control reactor, frequent episodes of clogging of the effluent and biogas outputs by scum accumulated on the liquid surface were verified, what did not occur in the reactor fed with the previously hydrolyzed wastewater, even after 276 days of continuous operation. Analysis of O&G in the scum and biomass collected from different heights of the sludge bed and photos of the three-phase separator and liquid surface at the end of the operation period from both reactors showed an accumulation of fat significantly higher in the control reactor. Results confirm the effectiveness of the prehydrolysis step in the treatment of wastewater with high fat content.