Abstract
The effect of ultrasound (US) pretreatment on two-phase olive mil solid waste (OMSW) composition and subsequent anaerobic biodegradation was evaluated by chemical oxygen demand solubilization and biochemical methane potential (BMP) tests. OMSW was ultrasonically pretreated at a power of 200 W and frequency of 24 kHz for time periods of 20, 40, 60, 90, 120, and 180 minutes, corresponding to specific energies of 11367, 21121, 34072, 51284, 68557, and 106003 kJ/kg total solids, respectively. In order to evaluate the US pretreatment, a low, medium, and high exposure time, that is, 20, 90, and 180 min, were selected for BMP tests. Methane yields of 311 ± 15, 393 ± 14, and 370 ± 20 mL CH4/g VSadded (VS: volatile solids) were obtained for 20, 90, and 180 minutes, respectively, while the untreated OMSW gave 373 ± 4 mL CH4/g VSadded. From a kinetic point of view, the BMP tests showed a first exponential stage and a second sigmoidal stage. In the first stage, the kinetic constant obtained for US pretreated OMSW at 20 minutes was 46% higher than those achieved for the pretreated OMSW at 90 and 180 minutes and 48% higher than that for untreated OMSW. The maximum methane production rate achieved was 12% higher than that obtained for untreated OMSW.
Highlights
The two-phase olive mill solid waste (OMSW) is the main waste produced after primary centrifugation in the two-phase olive oil mills
The maximum methane production rate achieved was 12% higher than that obtained for untreated olive mil solid waste (OMSW)
For the ultrasound pretreatment at 90 min the kinetics was the quickest; 70.5 mL CH4/(g VSadded⋅day) was produced, a value 12% higher than that obtained for untreated OMSW
Summary
The two-phase olive mill solid waste (OMSW) is the main waste produced after primary centrifugation in the two-phase olive oil mills. Two-phase OMSW is the main waste produced and has a high organic matter concentration It is a very wet waste (60–70% humidity), containing 3% of olive oil and a complex structure formed mainly by lignin (42.6%), cellulose (19.4%), and hemicellulose (35.1%) [2]. These characteristics result in an elevated polluting load. The quantities of OMSW generated are very large; every year from two to four million tonnes are produced in countries like Spain. Both composition and quantity produced make two-phase OMSW an important environmental problem [3]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
