Decrease of Pollutant Level of Bleaching Effluents and Winning Valuable Products by Successive Flocculation and Microbial Growth

Abstract

The bulk of organic matter from spent bleaching effluent (SBE), either from chlorination and extraction stages or a mixture of both, can be precipitated with polycationic polymers. The mixtures of polyethy-lenimine and modified (containing cationic side groups) starches, can precipitate from bleaching effluent about 75% of adsorbable organic chlorine (AOX), 59% of chemical oxygen demand (COD) and 80% of colour. These mixtures contained less polyimine in comparison to when polyimine was used aline thus saving material costs. After removal of chloroorganics of high molecular mass by precipitation growth of microorganisms in SBE was facilitated. The supernatant of the treated SBE supplemented with glucose and ammonium sulfate supported active growth of fungi from different genera, particularly from Aspergillus spp., Penicillium spp., Basidiomycetes, Aureobasidium. The fungi tested showed appreciable degradation activity regarding monochlorophenols,as well as additional reduction of AOX. During the growth in the treated SBE, Aureobasidiumpullulans decreased the content of AOX remaining after precipitation, and at the same time synthesized and excreted in a surrounding media exopolysaccharides. Pullulan, synthesized in appreciable level by Aureobasidium sp, could easily be isolated from the media. Isolated exopolysaccharides did not contain organochlorine. Fungal polysaccharides synthesized in SBE might be considered as an additional benefit that eventually will be able to reduce further the running costs of the SBE treatment.