Kinetic study of the methanogenic step of a two-stage anaerobic digestion process treating olive mill solid residue

Abstract A kinetic study of the methanogenic step of a two-stage anaerobic digestion process treating two-phase olive oil mill solid residue (OMSR) was conducted at mesophilic temperature (35 °C). The anaerobic digestion of OMSR was carried out in two different steps. After a hydrolytic–acidogenic stage, working at an organic loading rate (OLR) of 12.9 g COD L −1  day −1 (COD: chemical oxygen demand), the effluents or acidified OMSR obtained were employed for feeding a second or methanogenic step. For the methanogenic step, OLRs of between 0.8 and 22.0 g COD L −1  day −1 were studied (corresponding to hydraulic retention times (HRTs) of between 142.9 and 4.6 days). The substrate treated in the second phase (acidified OMSR) had a high total concentration in volatile fatty acids (14.5 g CH 3 COOH L −1 ) and a high percentage of acetic acid as the main methane precursor (57.5% of the total concentration). As a consequence of the first step a high stability in the methanogenic stage was achieved. A total chemical oxygen demand balance was developed over the methanogenic step. For this model two considerations were taken in account: (1) volumetric flow constant during the experiments (the volume of effluent that was taken from the methanogenic reactor every day was equal to the volume of acidified OMSR fed). (2) Constant concentration of methanogenic microorganisms during the experiments (the slow growing rate of the methanogenic microorganisms makes it possible for the concentration of microorganisms over the process to remain constant). The cellular maintenance coefficient ( m ) and methane yield coefficient ( Y G / S ) were found to be 0.016 g COD removed g −1  VSS day −1 and 0.261 L CH 4  g −1 COD removed, respectively.

[1]  W. Gujer,et al.  Conversion processes in anaerobic digestion , 1983 .

[2]  Joan Mata-Álvarez,et al.  Anaerobic digestion of organic solid wastes. An overview of research achievements and perspectives , 2000 .

[3]  Jonatan Andersson,et al.  Evaluation of straw as a biofilm carrier in the methanogenic stage of two-stage anaerobic digestion of crop residues. , 2002, Bioresource technology.

[4]  L. Miles,et al.  2000 , 2000, RDH.

[5]  M. Martín,et al.  Study and optimisation of the anaerobic acidogenic fermentation of two-phase olive pomace , 2005 .

[6]  C. Romero,et al.  Hydroxytyrosol 4-beta-D-glucoside, an important phenolic compound in olive fruits and derived products. , 2002, Journal of agricultural and food chemistry.

[7]  Effect of rapid temperature change and HRT on anaerobic acidogenesis , 1997 .

[8]  A H Veeken,et al.  Effect of substrate-seed mixing and leachate recirculation on solid state digestion of biowaste. , 2000, Water science and technology : a journal of the International Association on Water Pollution Research.

[9]  D. T. Hill,et al.  Using volatile fatty acid relationships to predict anaerobic digester failure. , 1987 .

[10]  R. Borja,et al.  Effect of the organic loading rate on the performance of anaerobic acidogenic fermentation of two-phase olive mill solid residue. , 2008, Waste management.

[11]  Rafael Borja,et al.  Kinetics of mesophilic anaerobic digestion of the two-phase olive mill solid waste , 2003 .

[12]  R. Borja,et al.  Evaluation of the methanogenic step of a two-stage anaerobic digestion process of acidified olive mill solid residue from a previous hydrolytic-acidogenic step. , 2009, Waste management.

[13]  B. Ahring,et al.  Volatile fatty acids as indicators of process imbalance in anaerobic digestors , 1995, Applied Microbiology and Biotechnology.

[14]  Göksel N. Demirer,et al.  Two-phase anaerobic digestion of unscreened dairy manure , 2005 .

[15]  N. L. Ricker,et al.  Mathematical modeling of an anaerobic butyrate degrading consortia : predicting their response to organic overloads , 1993 .

[16]  S. Han,et al.  Performance of UASB reactor treating leachate from acidogenic fermenter in the two-phase anaerobic digestion of food waste. , 2001, Water research.

[17]  M. Martín,et al.  The effect of organic loading rate on the anaerobic digestion of two-phase olive mill solid residue derived from fruits with low ripening index , 2007 .

[18]  Iván López,et al.  Modelling a full scale UASB reactor using a COD global balance approach and state observers , 2009 .

[19]  Rafael Borja,et al.  Influence of organic loading rate and hydraulic retention time on the performance, stability and microbial communities of one-stage anaerobic digestion of two-phase olive mill solid residue , 2008 .

[20]  Orhan Yenigün,et al.  Two‐phase anaerobic digestion processes: a review , 2002 .

[21]  E. Sánchez,et al.  Comparative effect of different aerobic pretreatments on the kinetics and macroenergetic parameters of anaerobic digestion of olive mill wastewater in continuous mode , 1998 .

[22]  A. E. Greenberg,et al.  Standard methods for the examination of water and wastewater : supplement to the sixteenth edition , 1988 .