Anaerobic biodegradation of two‐phase olive mill solid wastes and liquid effluents: kinetic studies and process performance

Abstract

The new two-phase olive oil mills produce three identifiable and separate waste streams, namely (1) the wash waters from the initial cleansing of the fruit, (2) the aqueous solid residues from the primary centrifugation and (3) the wash waters from the secondary centrifugation. As well as offering process advantages, they also consume less water. Therefore the solid residue, two-phase olive mill solid waste (OMSW), has a high organic matter concentration, giving it an elevated polluting load, and cannot be easily handled by traditional technology which deals with the conventional three-phase olive cake. In addition, the new two-phase olive mill effluents (TPOME) are made up of a mixture of effluents (1) and (3), the total volume of TPOME generated being ∼0.25 dm 3 kg −1 olives processed. This review aims to report the main features and characteristics of two-phase OMSW and TPOME as compared with the classical olive cake and olive mill wastewater (OMW) derived from the three-phase manufacturing process. The advantages and disadvantages of the two-phase decanting process are summarised. The anaerobic digestibility of two-phase OMSW using different influent substrate concentrations is reported. Kinetic studies of anaerobic digestion of two-phase OMSW are also reviewed and summarised, as well as mass balances to predict the behaviour of the reactor and simplified kinetic models for studying the hydrolysis, acidogenic and methanogenic steps of one-and two-stage anaerobic digestion of OMSW. The review also includes the following: assays of anaerobic digestion of wastewaters from the washing of olives, of olive oil and the two together using fluidised beds and hybrid reactors; the kinetics, performance, stability, purification efficiencies and methane yield coefficients.

Effects of co-substrate on biogas production from cattle manure: a review

“…The appropriate operation parameters of an anaerobic digestion related to the suitable factors are temperature, pH, volatile fatty acids, alkalinity, NH 3 -N, supplement of nutrients, trace elements, sulfides and heavy metals (Borja et al 2006;Sakar et al 2009;Yadanaparthi et al 2014, Kavitha et al 2015c. Hence, the stability parameters for a highly biogasification especially depend on temperature, HRT, OLR and substrate content in the feeding.…”

Bioremediation and biovalorisation of olive-mill wastes

“…This technique presents a number of advantages in comparison to the classical aerobic processes: (a) quite a high degree of purification with high-organic-load feeds can be achieved; (b) low nutrient requirements are necessary; (c) small quantities of excess sludge are usually produced; and (d) a combustible biogas is generated (Borja et al 2006;Wheatley 1990). However, the nutrient imbalance of OMWW, due mainly to its high C/N ratios (∼50), low pH (∼5), low alkalinity (∼0.6 g CaCO 3 per litre) and the presence of biostatic and inhibitory substances, represents a problem for the anaerobic degradation of these wastewaters (Boubaker and Cheikh Ridha 2007).…”

“…As mentioned above, anaerobic digestion is a practical alternative for the treatment of TPOMW, which produces biogas (Borja et al 2006;Antizar-Ladislao and Turrion-Gomez 2008). As it has been reported for other agroindustrial residues, such as potato pulp (Zhu et al 2008) or cattle manure (Güngör-Demirci and Demirer 2004), anaerobic processes applied to OMWs, whether in one or two stages, must be selected according to the C/N ratio of the residues in order to obtain a satisfactory anaerobic degradation.…”

“…As it has been reported for other agroindustrial residues, such as potato pulp (Zhu et al 2008) or cattle manure (Güngör-Demirci and Demirer 2004), anaerobic processes applied to OMWs, whether in one or two stages, must be selected according to the C/N ratio of the residues in order to obtain a satisfactory anaerobic degradation. The TPOMW is biodegradable by anaerobic digestion at mesophilic temperatures in stirred tank reactors, with COD removal efficiencies in the range of 72-89% and an average methane yield coefficient of 0.31 dm 3 CH 4 per gramme COD removed (Borja et al 2006). Similar production of hydrogen and methane has been reported using thermophilic reactors at 55°C (Gavala et al 2005) and in mesophilic anaerobic treatment of TPOMW in continuous and batch experiments, in which approximately 0.28 dm 3 CH 4 per gramme COD was removed, and hydrogen production was coupled with a subsequent step for methane production, giving the potential for production of 1.6 mmol H 2 per gramme of TPOMW (dry matter; Borja et al 2006).…”

Microbial Biotechnology in Olive Oil Industry

“…This technique presents a number of advantages in comparison to the classical aerobic processes: (a) a high degree of purification with high-organic-load feeds can be achieved; (b) low nutrient requirements are necessary; (c) small quantities of excess sludge are usually produced; and (d) a combustible biogas is generated (Dalis et al 1996;Zouari and Ellouz 1996;Borja et al 2006). Combined aerobic-anaerobic systems have also been used effectively in the bioremediation of OMWs (Hamdi and Garcia 1991;Borja et al 1995).…”