References
  -  M.S. Fountoulakis, S.N. Dokianakis, M.E. Kornaros,
    G.G. Aggelis, G. Lyberatos, Removal of phenolics in olive mill
    wastewaters using the white-rot fungus Pleurotus ostreatus,
    Water Res., 36 (2002) 4735–4744. 
 
  -  B. Fezzani, R. Ben Cheikh, Two-phase anaerobic co-digestion
    of olive mill wastes in semi-continuous digesters at mesophilic
    temperature, Bioresour. Technol., 101 (2010) 1628–1634. 
 
  -  I. Angelidaki, B.K. Ahring, Codigestion of olive oil mill
    wastewaters together with manure, household waste or sewage
    sludge, Biodegradation, 8 (1997) 221–226. 
 
  -  A. Ranalli, The effluent from olive mills: proposals for re-use
    and purification with reference to Italian legislation, Olivae,
    38 (1991) 26–40. 
 
  -  J.A. Fiestas Ros de Ursinos, R. Borja, Use and treatment of
    olive mill wastewater: current situation and prospects in Spain,
    Grasas y Aceites, 2 (1992) 101–106. 
 
  -  B. Deepanraj, V. Sivasubramanian, S. Jayaraj. Effect of substrate
    pre-treatment on biogas production through anaerobic
    digestion of food waste, Int. J. Hydrogen Energy, 4 (2017)
    26522–26528. 
 
  -  R. Bouaita, K. Derbal, H. Zekri, Evaluation of ultrasonic
    pretreatment on anaerobic digestion of citrus orange peel waste
    for methane production, J. New Technol. Mater., 8 (2018) 76–81. 
 
  -  I. Angelidaki, B.K. Ahring, H. Deng, J.E. Schmidt, Anaerobic
    digestion of olive oil mill effluents together with swine manure
    in UASB reactors, Water Sci. Technol., 45 (2002) 213–218. 
 
  -  M. Shirzad, H.K.S. Panahi, B.B. Dashti, M.A. Rajaeifar,
    M. Aghbashlo, M.A. Tabatabaei, A comprehensive review on
    electricity generation and GHG emission reduction potentials
    through anaerobic digestion of agricultural and livestock/slaughterhouse wastes in Iran, Renewable Sustainable Energy
    Rev., 111 (2019) 571–594. 
 
  -  A.M. Aboulfoth, E.H. El Gohary, O.D. El Monayeri, Effect of
    thermal pretreatment on the solubilization of organic matters
    in a mixture of primary and waste activated sludge, J. Urban
    Environ. Eng., 9 (2015) 82–88. 
 
  -  M. Takashima, Examination on process configurations
    incorporating thermal treatment for anaerobic digestion of
    sewage sludge, J. Environ. Eng., 134 (2008) 43e9, 
    doi:10.1061/(ASCE)0733-9372(2008)134:7(543).  
  -  G. Kumar, P. Sivagurunathan, N.B.D. Thi, G. Zhen, T. Kobayashi,
    K. Sang-Hyoun, K. Xu, Evaluation of different pretreatments
    on organic matter solubilization and hydrogen fermentation
    of mixed microalgae consortia, 
    J. Hydrogen Energy, 41 (2016)
    21628–21640.  
  -  E. Mahfouf Bouchareb, D. Kerroum, E. Bezirhan Arikan,
    Z. Iski, N. Dizge, Production of bio-hydrogen from bulgur
    processing industry wastewater, Energy Sources, Part A, (2021)
    1877853, doi:10.1080/15567036.2021.1877853. 
 
  -  B. Rokaya, D. Kerroum, Z. Hayet, A. Panico, A. Ouafa, Fr. Pirozzi,
    Biogas production by an anaerobic digestion process from
    orange peel waste and its improvement by limonene leaching:
	  investigation of H2O2 
    pre-treatment effect, Energy Sources,
  Part A, (2019) 1692975, doi: 10.1080/15567036.2019.1692975.  
  -  Y.-Y. Li, T. Noike, Upgrading of anaerobic digestion of waste
    activated sludge by thermal pretreatment, Water Sci. Technol.,
    26 (1992) 857–866. 
 
  -  Ch. Ying-Chih, Ch. Cheng-Nam, L. Jih-Gaw, H. Shwu-Jiuan, Alkaline and ultrasonic pretreatment of sludge before
  anaerobic digestion, Water Sci. Technol., 36 (1997) 155. 
 
  -  K. Hwang, E. Shin, H. Choi, A mechanical pretreatment of
    activated sludge for improvement of anaerobic digestion
    system, Water Sci. Technol., 36 (1997) 111. 
 
  -  S. Sawayama, S. Inoue, T. Minowa, K. Tsukahara, T. Ogi,
    Thermochemical liquidization and anaerobic treatment of
    kitchen garbage, J. Ferment. Bioeng., 5 (1997) 451. 
 
  -  J.A. Müller, A. Winter, G. Strünkmann, Investigation and
    assessment of sludge pre-treatment processes, Water Sci.
    Technol., 49 (2004) 97–104. 
 
  -  L. Appels, J. Baeyens, J. Degrève, R. Dewil, Principles and
    potential of the anaerobic digestion 
    of waste-activated sludge,
    Prog. Energy Combust. Sci., 34 (2008) 755–781.  
  -  L. Appels, J. Lauwers, J. Degrève, L. Helsen, B. Lievens,
    K. Willems, J. Van Impe, R. Dewil, Anaerobic digestion in global
    bio-energy production: potential and research challenges,
    Renewable Sustainable Energy Rev., 15 (2011) 4295–4301. 
 
  -  S. Pérez-Elvira, M. Fdz-Polanco, F.I. Plaza, G. Garralón, F. Fdz-Polanco, Ultrasound pre-treatment for anaerobic digestion
    improvement, Water Sci. Technol., 60 (2009) 1525–1532. 
 
  -  C. Bougrier, C. Albasi, J.P. Delgenès, H. Carrère, Effect of
    ultrasonic, thermal and ozone pre-treatments on waste
    activated sludge solubilisation and anaerobic biodegradability,
    Chem. Eng. Process., 45 (2006) 711–718. 
 
  -  C. Bougrier, Optimisation of Anaerobic Digestion Using
    a Physicochemical Co-treatment: Application to Biogas
    Production from Wastewater Sludge, Ph.D. Thesis, Genie des
    procédés, Université Montpellier II, 2003, 258 p (in French). 
 
  -  APHA, Standard Methods for the Examination of Water and
    Wastewater, 19th ed., Washington, DC, 1995. 
 
  -  E. Elbeshbishy, G. Nakhla, H. Hafez, Biochemical methane
    potential (BMP) of food waste and primary sludge: influence
    of inoculum pre-incubation and inoculum source, Bioresour.
    Technol., 110 (2012) 18–25. 
 
  -  D.P. Chynoweth, C.E. Turick, J.M. Owens, D.E. Jerger,
    M.W. Peck, Biochemical methane potential of biomass and
    waste feedstocks, Biomass Bioenergy, 5 (1993) 95–111. 
 
  -  B. Wang, S. Strömberg, C. Li, I.A. Nges, M. Nistor, L. Deng,
    J. Liu, Effects of substrate concentration on methane potential
    and degradation kinetics in batch anaerobic digestion,
    Bioresour. Technol., 194 (2015) 240–246. 
 
  -  T.H. Erguder, E. Guven, G.N. Demirer, Anaerobic treatment of
    olive mill wastes in batch reactors, Process Biochem., 36 (2000)
    243–248. 
 
  -  U. Neis, K. Nickel, A. Tiehm, Enhancement of anaerobic sludge
    digestion by ultrasonic disintegration, Water Sci. Technol.,
    42 (2000) 73–80. 
 
  -  O. Achouri, A. Panico, M. Bencheikh-Lehocine, K. Derbal,
    D. Arias, F. Iasimone, R. Padulano, M. Bouteraa, A. Rebahi,
    F. Pirozzi, Role of H2O2 dosage on methane production from
    tannery wastewater: experimental and kinetic study, J. Water
    Process Eng., 43 (2021) 102313, doi: 10.1016/j.jwpe.2021.102313. 
 
  -  A. Ouafa, P. Antonio, BL. Mossaab, D. Kerroum, R. Amel, and
    P. Francesco, Alkaline pretreatment of tannery wastewater
    impact of biochemical potential tests: experimental study and
    kinetics modeling, J. Biomass Convers. Biorefin., (2021) 1–13,
    doi: 10.1007/s13399-021-01571-1. 
 
  -  B. Wang, Factors That Influence the Biochemical Methane
    Potential (BMP) Test Steps Towards the Standardisation of BMP
    Test, Ph.D. Thesis, Lund University, Lund, Sweden, 2016.