A Comprehensive Review on Pulp and Paper Industries Wastewater Treatment Advances

The pulp and paper industry generates vast amounts ofwastewater,and its character heavily depends on various factors (raw material,the undertaken process, the final product, etc.). The wastewater fromthis sector, which originates from several sources in each mill andare mostly combined, is polluting and hazardous. This paper presentsa state-of-the-art review of the physical, chemical, biological, andadvanced hybrid treatment techniques, concerning their effectivenessin removing specific pollutants, namely, chemical oxygen demand, lignin,color, and adsorbable organo-halogens. Throughout the manuscript,at the end of each section, a conclusive comparison has been presentedand the proper method is introduced. Furthermore, numeric data regardingthe effectiveness of each technique toward each pollutant are gatheredfrom the literature and are available in the Supporting Informationof the paper. Biological treatment processes using anaerobic-aerobictreatment mostly cure organic biodegradable contaminants (75-90%COD removal). Moreover, biological treatment using a consortium ofmicroorganisms can potentially increase color removal efficiency (from65 to 97%). Hybrid treatment is also among the candidates for colorremoval. To treat complex matters (lignin and AOX), physical and chemicaltreatments have shown promising performance, but they are generallyexpensive and impractical to treat huge amounts of wastewater. Forthe treatment of high molecular weight contaminants (lignin) advancedoxidation processes (AOPs), including ozonation and Fenton-based treatment,have shown great performance (90-99%); however, they are limiteddue to their maintenance and operation costs. To overcome these challenges,source separation of the wastewater streams in the pulp and paperindustry is recommended. AOPs or membrane technologies or hybrid processesare suggested for the bleaching effluent (80% AOX removal), whichis relatively low in amount, and a combination of conventional treatmentprocesses would be preferred to treat wastewater streams that aremore biodegradable. The biological performance can also be enhancedusing granular activated carbon on the sequence. Finally, for treatingblack liquor, adsorption processes have proven to be the prime candidate.