The application of advanced oxidation technologies to the treatment of effluents from the pulp and paper industry: a review

Abstract

Paper industry is adopting zero liquid effluent technologies to reduce fresh water use and meet environmental regulations, which implies water circuits closure and the progressive accumulation of pollutants that must be removed before water re-use and final wastewater discharge. The traditional water treatment technologies that are used in paper mills (such as dissolve air flotation or biological treatment) are not able to remove recalcitrant contaminants. Therefore, advanced water treatment technologies, such as advanced oxidation processes (AOPs), are being included in industrial wastewater treatment chains aiming to either improve water biodegradability or its final quality. A deep review of the current state of the art regarding the use of AOPs for the treatment of the organic load of effluents from the paper industry is herein addressed considering mature and emerging treatments for a sustainable water use in this sector. Wastewater composition, which is highly dependent of the raw materials being used in the mills, the selected AOP itself, and its combination with other technologies, will determine the viability of the treatment. In general, all AOPs have been reported to achieve good organics removal efficiencies (COD removal >40%; and about an extra 20% if AOPs are combined with biological stages). Particularly, ozonation has been the most extensively reported and successfully implemented AOP at an industrial scale for effluent treatment or reuse within pulp and paper mills; although Fenton processes (photo-Fenton particularly) have actually addressed better oxidative results (COD removal ≈65-75%) at lab scale, but still need further development at large scale.

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

“…The conventional Fenton process has been tested in the pulp and paper industry at laboratory scale to polish different mill effluents (from kraft pulp to recovered paper mills) reporting good oxidation removal efficiencies (COD removal > 60%; Hermosilla et al 2015), although the partially-oxidized composition of the treated wastewater did not show a reduction of toxicity to Artemia salina in comparison with the untreated effluent (Tambosi et al 2006). Figure 14 outlines the process sequence in a conventional Fenton system for wastewater treatment.…”

“…According to Hermosilla et al (2015), although Fenton processes seem to perform well under laboratory settings, they are not often implemented at industrial scale in comparison to ozone treatment, probably due to there being much more experience in the implementation of ozone processes. Other factors include the more frequent availability of ozone treatments for bleaching stages in paper mills, as well as some disadvantages of Fenton processes application, such as the production of iron sludge and the requirement of acidic conditions for optimal performance.…”

“…It is a highly energetic form of oxygen that has the capability of breaking down many hard-to-biodegrade organic compounds found in pulping and bleaching wastewaters in two ways, directly reacting with dissolved substances, and indirectly producing hydroxyl radicals; the reaction is improved under basic pH conditions, without the need to apply ultraviolet light, use a catalyst, or add iron compounds (Rice 1997;Alvares et al 2001;Pokhrel and Viraraghavan 2004;Hermosilla et al 2015). There have been many investigations devoted to the treatment of P&P wastewater using ozone by itself (Prat et al 1988;Heinzle et al 1992;Chen and Horan 1998; Rodrígues et al 1988; Heble et al 1999;Yeber et al 1999b;Freire et al 2000;Amat 2005b;Kreetachat et al 2007;Wang et al 2008b;de los Santos Ramos 2009;Kishimoto et al 2010;Merayo et al 2013;Cheng et al 2015;Hermosilla et al 2015). Enhanced biodegradation of contaminants owing to the inclusion of an ozone pretreatment of industrial wastewaters has been reported (Yeber et al 1999b;Heinzle et al 1992;Wang et al 2008b;de los Santos Ramos 2009;Tripathi et al 2011).…”

“…The main mechanism involving the application of such a catalyst is the formation of reactive oxygen barriers under which superoxide (·O2−) is produced as a result of the reduction of molecular oxygen (O2) (Turrens 2003). Such species are very reactive towards the pollutants in P&P mill wastewater.According to Hermosilla et al (2015), although Fenton processes seem to perform well under laboratory settings, they are not often implemented at industrial scale in comparison to ozone treatment, probably due to there being much more experience in the implementation of ozone processes. Other factors include the more frequent availability of ozone treatments for bleaching stages in paper mills, as well as some disadvantages of Fenton processes application, such as the production of iron sludge and the requirement of acidic conditions for optimal performance.…”

“…"Pulp & paper effluent," BioResources 11(3), 7953-8091. 7993to be very efficient, achieving over 90% removal of the COD present in the effluent after the biological treatment (Hermosilla et al 2015). …”