Use of Microbes for Black Liquor Clarification

Effluent from pulp and paper industry called as black liquor (BL). Black liquor contains salts and organic material. It is dark coloured and hazardous in nature. Precipitation of black liquor (BL) was studied. Different concentrations of hydrochloric acid attempted. 0.73, 1.46, 1.82, 2.19, 2.55, 2.92 % HCl was used. Precipitation observed. pH, residue amount and decolorization were studied. 2.55, 2.92% HCl were able to precipitate the black liquor (BL) to a maximum level. pH of the supernatant was 6.0 and 5.0 respectively. We have studied biodegradation of this undiluted black liquor at different pH 5 and 6. Different bacterial and yeast cultures were used for screening. 18 cultures used for biodegradation of black liquor at pH 6.0. Cell concentration was 2.5% (wet weight basis). 80% black liquor used. Biodegradation was carried out at 280C for 24h under shaking condition. Candida utilis NCIM 3055 has shown 9.81% decolorization. We have used pH 5.0 for screening at 280C for 24h under shaking condition. 21 cultures were used for screening. Among the 21 cultures, Pseudomonas putida NCIM 2205, Pseudomonas testosteronii NCIM 5099 and Saccharomyces carlsbergensis NCIM 3455 have shown 27.74, 37.74 and 24.57% decolorization. Pseudomonas testosteronii NCIM 5099 has shown maximum decolorization. It has produced clear liquid after treatment.