Anaerobic digestion of alkaline bleaching wastewater from a kraft pulp and paper mill using UASB technique

Abstract

Anaerobic digestion of alkaline kraft elemental chlorine-free bleaching wastewater in two mesophilic, lab-scale upflow anaerobic sludge bed reactors resulted in significantly higher biogas production (250±50 vs. 120±30 NmL g [Formula: see text]) and reduction of filtered total organic carbon (fTOC) (60±5 vs. 43±6%) for wastewater from processing of hardwood (HW) compared with softwood (SW). In all cases, the gas production was likely underestimated due to poor gas separation in the reactors. Despite changes in wastewater characteristics, a stable anaerobic process was maintained with hydraulic retention times (HRTs) between 7 and 14 h. Lowering the HRT (from 13.5 to 8.5 h) did not significantly affect the process, and the stable performance at 8.5 h leaves room for further decreases in HRT. The results show that this type of wastewater is suitable for a full-scale implementation, but the difference in methane potential between SW and HW is important to consider both regarding process dimensioning and biogas yield optimization.

Wastewater Treatment and Reclamation: A Review of Pulp and Paper Industry Practices and Opportunities

“…Pollutants from various stages of bleaching of kraft pulps are among the most difficult to remove from wastewater (Prat et al 1988;Kemeny and Banerjee 1997;Vidal et al 1997;Yeber et al 1999b;Kansal et al 2008;Uğurlu and Karaoğlu 2009;Quezada et al 2014;Larsson et al 2015). Many of these compounds may have some adverse effects on the receiving media, such as formation of slime and scum, toxic effects to the exposed living organisms, and thermal impacts ( …”

“…20. Due to the value of methane as a fuel, and perhaps also the importance of avoiding its release into the atmosphere (Weiland 2010), much research has been devoted to its generation during anaerobic treatment of P&P mill wastewater (Maat and Habets 1987;Korczak et al 1991;Minami et al 1991;Sierraalvarez et al 1991;Vidal et al 1997;Kortekaas et al 1998;Ahn and Forster 2002;Buzzini and Pires 2007;Yilmaz et al 2008;Tabatabaei et al 2010;Lin et al 2011;Saha et al 2011;Elliott and Mahmood 2012;Bayr et al 2013;Ekstrand et al 2013;Hagelqvist 2013;Hassan et al 2014;Meyer and Edwards 2014;Larsson et al 2015). …”

“…Also there have been review articles devoted to the treatment of P&P mill effluents using anaerobic conditions (Graves and Joyce 1994;Rintala and Puhakka 1994;Savant et al 2006;Meyer and Edwards 2014;Kamali and Khodaparast 2015). Many other authors have reported evaluations of factors affecting the anaerobic treatment of P&P mill wastewaters (Sierraalvarez et al 1991;Korczak et al 1991;Vidal et al 1997;Kortekaas et al 1998;Bengtsson et al 2008a;Ruas et al 2012;Krishna et al 2014;Larsson et al 2015).A plus side of anaerobic treatment is that one does not need to pay for the pumping of air into the system (Maat and Habets 1987), and, according to many reports, the amounts of sludge produced are generally less than in conventional aerated biological treatment systems (Ashrafi et al 2015;Kamali and Khodaparast 2015). Anaerobic processes produce gases such as methane, requiring their collection and safe disposal.…”

“…In addition, conventional bleaching technologies, based on chlorine dioxide, sodium hypochlorite, and related chemicals, yield wastewaters that would be excessively corrosive to the equipment used for chemical recovery, hence discouraging the recovery of pulping chemicals from such wastewater streams. The condensate collected during evaporative concentration of spent pulping liquor is a notable source of toxicity and odor, which needs to be treated (Wagner and Nicell 2001;Tielbaard et al 2002).Pollutants from various stages of bleaching of kraft pulps are among the most difficult to remove from wastewater (Prat et al 1988;Kemeny and Banerjee 1997;Vidal et al 1997;Yeber et al 1999b;Kansal et al 2008;Uğurlu and Karaoğlu 2009;Quezada et al 2014;Larsson et al 2015). Many of these compounds may have some adverse effects on the receiving media, such as formation of slime and scum, toxic effects to the exposed living organisms, and thermal impacts ( …”

Techno-economic assessment of anaerobic digestion in a typical Kraft pulp mill to produce biomethane for the road transport sector

“…Considering recent advances in technology and knowledge with regard to anaerobic treatment of waste streams from bleached Kraft pulp mills (Ekstrand et Larsson et al 2015), the aim of this article is to assess the technical potential for production of liquid biogas in a typical Swedish Kraft pulp mill as well as the economics of such an investment. The two mentioned possibilities for anaerobic treatment and biogas production, high rate integrated reactor or external reactor, are evaluated separately as described in sections 2.2 and 2.3.…”