Anaerobic co-digestion assessment of olive mill wastewater and food waste: Effect of mixture ratio on methane production and process stability

• Published in: Journal of environmental chemical engineering Vol. 8; no. 4; p. 103874
• Main Authors: El Gnaoui, Y., Sounni, F., Bakraoui, M., Karouach, F., Benlemlih, M., Barz, M., El Bari, H.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2020
• Subjects: Anaerobic co-digestion; Food waste; Methane production; Olive mill wastewater; Process stability; Food waste; Anaerobic co-digestion; Olive mill wastewater; Process stability; Methane production
• ISSN: 2213-3437; 2213-3437
• DOI: 10.1016/j.jece.2020.103874

[Display omitted] •The co-digestion at the mixture 20 % OMWW: 80 % FW improved the process stability in terms of ALK, pH and VFA/ALK ratio.•The methane yield achieved the maximum of 302.16 mLSTP CH4. g VS−1 with the addition of 80 % FW.•The methane yield increased by 37 % with 20 % OMWW: 80 % FW compared to control.•The biodegradation rate enhanced by 56 % with 80 % FW. The Olive oil industry is one of the most important agro-industrial sectors in the Mediterranean countries, in which Morocco is the world's 5th largest olive oil producer. By-products of this agro-industry such as OMWW and olive mill pomace represent a major challenge for the environment. The high concentration of polyphenols in OMWW and the lack of nitrogen make AD of this substrate difficult. AcoD of OMWW with other substrates is an alternative solution to fill this gap. In the present study, AcoD of OMWW with FW from the Ibn Tofail University campus restaurant was investigated, in order to enhance AD of OMWW in terms of methane production and process stability. Different co-substrates were prepared and tested, in which the content of OMWW varied from 20 to 80 %.The MY and biodegradability were optimal at the mixture 20 % OMWW: 80 % FW showing the values of 302.16 ± 3.04 mLSTP CH4.gVS−1 and 86.0 ± 4.1 % respectively. The process stability was investigated through the alkalinity and the volatile fatty acids ratio VFA/ALK, and the results show that all mixtures were stable except the control test mono AD of OMWW. This stability might be due to the simultaneous presence of ammonia ions from the decomposition of proteins contained in FW and bicarbonate ions. The OLR increased when the added loads increased throughout the conducted experiments. The OLR of the mixture 20 % OMWW: 80 % FW was 2.0 ± 0.1 kg VS. m-3.d−1) higher than OLR of control test (1.45 ± 0.05 kg VS.m-3.d−1). Furthermore, two kinetics models were applied (modified Gompertz model and the Logistic model). The results shown that both models had a good conformity, and the modified Gompertz model was the more appropriate showing a higher values of R2 than logistic model. Moreover, the lag time decreased when the OMWW proportion increased.