A Comprehensive Review on Pulp and Paper Industries Wastewater Treatment Advances

Abstract

The pulp and paper industry generates vast amounts of wastewater, and its character heavily depends on various factors (raw material, the undertaken process, the final product, etc.). The wastewater from this sector, which originates from several sources in each mill and are mostly combined, is polluting and hazardous. This paper presents a state-of-the-art review of the physical, chemical, biological, and advanced hybrid treatment techniques, concerning their effectiveness in 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 presented and the proper method is introduced. Furthermore, numeric data regarding the effectiveness of each technique toward each pollutant are gathered from the literature and are available in the Supporting Information of the paper. Biological treatment processes using anaerobic–aerobic treatment mostly cure organic biodegradable contaminants (75–90% COD removal). Moreover, biological treatment using a consortium of microorganisms can potentially increase color removal efficiency (from 65 to 97%). Hybrid treatment is also among the candidates for color removal. To treat complex matters (lignin and AOX), physical and chemical treatments have shown promising performance, but they are generally expensive and impractical to treat huge amounts of wastewater. For the treatment of high molecular weight contaminants (lignin) advanced oxidation processes (AOPs), including ozonation and Fenton-based treatment, have shown great performance (90–99%); however, they are limited due to their maintenance and operation costs. To overcome these challenges, source separation of the wastewater streams in the pulp and paper industry is recommended. AOPs or membrane technologies or hybrid processes are suggested for the bleaching effluent (80% AOX removal), which is relatively low in amount, and a combination of conventional treatment processes would be preferred to treat wastewater streams that are more biodegradable. The biological performance can also be enhanced using granular activated carbon on the sequence. Finally, for treating black liquor, adsorption processes have proven to be the prime candidate.

Hydrodynamic Cavitation and Advanced Oxidation for Enhanced Degradation of Persistent Organic Pollutants: A Review

“…The utilization of cavitation as a pre-treatment method has been observed to effectively disrupt hemicellulose structures and enhance the digestibility of sludge, thereby increasing its solubility [16]. The utilization of cavitation as a pre-treatment method is highly advantageous owing to its cost-effectiveness, absence of supplementary chemical usage, and absence of additional waste generation, as reported in previous studies [8].…”

“…They employed a hybrid approach that combined ultrasound-assisted Fenton methodology with the conventional aerobic process. The study documented a notable increase in the biodegradability index from 0.15 to 0.36, which was successfully accomplished in a span of 40 min through the utilization of the ultrasoundassisted Fenton process [16]. Table 1 provides a comprehensive summary of the existing research that examines the efficacy of different hydraulic conductivity geometries and hybrid methodologies in the degradation of diverse water pollutants.…”

“…Moreover, the arrangement encompasses pressure gauges. In order to mitigate the ingress of air into the liquid, it is ensured that both lines are terminated at a position below the liquid level within the holding tank [16].…”

Electrocoagulation Process as a Consolidated Technology in the Treatment of Industrial Effluents and as a Promising Process in the Treatment of Effluents Generated by Car Washes: A Brief Review

“…As a result, the effluents generated by this industrial segment are difficult to treat because they are complex mixtures of dangerous and highly toxic elements and chemical products . These effluents have high concentrations of organic compounds and high levels of dark coloration. , They also show high values for COD, BOD, wood debris, and other contaminants, according to the type of process used in each industrial plant. − …”

“…With the EC process, Esmaeeli et al 172 evaluated the effect of the initial pH of the effluent, the distance between the electrodes, the electric current density, and the arrangement of electrodes, combining Al and Fe electrodes on the efficiency of the process of reducing the COD index of effluents from the pulp and paper industry effluents, with 2500 mg O2 •L −1 , using reactors with a stirring of 100 rpm. According to the author, it was possible to obtain an 85.0% reduction of the COD index with current density values of 4.0 mA•cm −2 and operating with Fe/Fe electrodes, with distances of 10.0 mm, after 120 min of treatment and with pH set at 7.0.…”