Pretreatment and in Situ Fly Ash Systems for Improving the Performance of Sequencing Batch Reactor in Treating Thermomechanical Pulping Effluent

In this work, two methods were applied for improving the performance of activated sludge in treating the effluent of the thermomechanical pulping process. In one attempt, the effluent of the pulping process was pretreated with 0.2 wt % of fly ash (FA) at room temperature and 100 rpm for 1 h, and the FA-pretreated samples were further processed by a sequencing batch reactor (SBR) system. In another work, FA (0.2 wt %) and activated sludge were mixed with the effluent simultaneously in an in situ system. The results showed that FA assimilation would benefit the removal of nonbiodegradable substances and thus facilitate the decomposition of contaminants by activated sludge in both systems, especially in the in situ system. The removal efficiencies of 96.1%, 99.1%, 95.2%, 90.51%, and 99.5% were achieved for COD, BOD, TOC, lignin, and sugar from the effluent, respectively. In addition, the sludge volume index (SVI) of the FA-pretreated and in situ systems decreased to 100.7 and 75.5 mL/g and the effluent suspended solids (ESS) decreased to 67.9 and 55.5 mg/L, respectively, indicating that the use of FA improved activated sludge settling and flocculation affinity. These results are attributed to the adsorption of lignocelluloses on fly ash and decomposition of lignocelluloses by activated sludge. Moreover, as under-valued biomass-based fly ash was utilized as an efficient adsorbent, the developed technique is green and promising for application in wastewater treatment systems

Cationic Hemicellulose As a Product of Dissolving Pulp Based Biorefinery

In the present technology practiced, hemicelluloses dissolved in the prehydrolysis liquor (PHL) of the kraft-based dissolving pulp production process is mixed with black liquor and incinerated in the kraft mill. In this study, solvent precipitation was used for isolating lignin and hemicelluloses from PHL. The results showed that acetone was a more effective and selective solvent than ethanol to isolate hemicelluloses. Furthermore, the cationization of hemicelluloses with glycidyl-trimethylammonium chloride resulted in cationic hemicelluloses with the charge density of 2.3 meq/g and molecular weight of 6330 g/mol. Based on these results, an integrated dissolving pulp-based biorefining process was proposed that would produce dissolving pulp and cationic hemicellulose as main products