Effect of acid, heat and combined acid-heat pretreatments of anaerobic sludge on hydrogen production by anaerobic mixed cultures

Effects of pre-treatment technologies on dark fermentative biohydrogen production: A review

“…Physical technologies consist of mechanical pre-treatment, thermal pre-treatment (Assawamongkholsiri et al, 2013;Kim et al, 2009;Wang et al, 2003aWang et al, , 2003b, microwave (Abdelhalim et al, 2012;Thungklin et al, 2011) and ultrasound irradiation ; chemical technologies include the use of ionic liquids (ILs) (Nguyen et al, 2008), acids (Cui et al, 2009;Cui and Shen, 2012;Pattra et al, 2008), alkalis (Cui and Shen, 2012;Lo et al, 2010;De Vrije et al, 2002) and ozonolysis (Wu et al, 2013a(Wu et al, , 2013b; physicochemical technologies consist of steam explosion (Datar et al, 2007;Tang et al, 2013) and ammonia fibre explosion/ expansion (Cao et al, 2013) while biological technologies involve the use of fungi and enzymes (Cheng and Liu, 2012;Zhao et al, 2012b;Cui et al, 2010) as illustrated in Fig. 2.…”

“…Likewise, Wang et al (2011) observed that increasing the temperature of heat pre-treatment from 80 C to 100 C resulted in decreased H 2 yields and concluded that overheating was not beneficial to H 2 production, an observation shared by Nissil€ a et al (2011aNissil€ a et al ( , 2011b. The two parameters of pre-treatment during HST are heating temperature varying from 40 to 120 C (Wong et al, 2014b;Xiao and Liu, 2006;Baghchehsaraee et al, 2008;Guo et al, 2010b;Mu et al, 2007;Oh et al, 2003;Ravindran et al, 2010) and duration of heating ranging from 10 to 180 min (Karadag et al, 2009;Hu and Chen, 2007;Nissil€ a et al, 2011a;Chairattanamanokorn et al, 2009;O-Thong et al, 2009;Sivaramakrishna et al, 2010;Assawamongkholsiri et al, 2013;Bakonyi et al, 2014;Vijayaraghavan et al, 2006) as summarised in Table 1. For more studies on the use of heat for inoculum pre-treatment, refer to the review done by Wong et al (2014a).…”

“…Besides pre-treating inoculum, thermal pre-treatment has also been applied to lignocellulosic materials to assist in cell wall lysis and release of trapped components such as cellulose molecules into solution, thereby increasing solubilisation and promoting the accessibility of organics for enzymatic hydrolysis (Appels et al, 2008;Assawamongkholsiri et al, 2013). The major factor behind the bond breaking and cell wall lysis during thermal pre-treatment is the temperature employed whereby Appels et al (2008) stated a range of 150e200 C while Hendriks and Zeeman (2009) discussed that above 160 C, both lignin and hemicellulose are solubilised.…”

“…Jung et al (2011) heated Laminaria japonica under different conditions (20 min: 150e180 C and 170 C: 5e40 min) and obtained a maximum increase in H 2 yield of 63.0% (average at 170 C, 20 min) for pre-treated substrate (average: 110.2 mL g À1 COD) as opposed to the control (67.6 mL g À1 COD). More recently, Assawamongkholsiri et al (2013) heated anaerobic sludge in a hot air oven at 110 C for 15e60 min prior to DF with enriched seed sludge and reported an enhancement in H 2 yield of 22.2% for the 15 min pre-heated sludge while the other pretreatment durations did not improve H 2 yield. Bao et al (2013) heated corn starch at 100 C for 30 min and obtained an increase in H 2 yield by 40% for boiled corn starch relative to the control.…”

Long-term effect of acid and heat pretreatment of sludge from a sugarcane vinasse treatment plant on the microbial community and on thermophilic biohydrogen production

“…The conditions previously tested for the heat pretreatments were 100 C for 15 min and 60 min, and 80 C for 15 min and 60 min, as suggested in the literature [20e24]. For the acid pretreatments, the following conditions were assayed: pH 3 for 12 and 24 h. The combined pretreatment was tested at pH 3 for 24 h, which was followed by heat treatment at 80 C for 15 min [23]. These preliminary assays revealed that the following conditions enhanced H 2 production in shortterm tests: 80 C for 15 min followed by cooling to room temperature and maintenance of pH 3 for 24 h by addition of HCl at 5.0 mol/L.…”