Study On The Acid-producing Character Of White Rot Fungus And The Black Liquor Treatment

Black liquor of alkali papermaking is a kind of industry wastewater with high COD, high concentration of lignin and high pH. It is the primary source of the sullage from paper mills . The current treatment methods applied to treat the black liquor discharged by small and medium size paper mills are neither effective nor economical. The biologic characteristic, especially acid-producing and growth of WFR C were studied. The results showed that the growth and acid-producing was deeply affected by initial pH of media and the stable pH of buffer. The optimum pH for growth of WRF C was 2.86, and the highest pH which the fungi could endure was between 5.88 and 6.85, so the conclusion could be drawn that WRF C was a strain of acidophilic fungus. Not only pH, but also temperature, the concentration of nutriment, the metabolized produce, inoculated volume and the content of mycelium could influence growth and acid-producing of WRF C .The optimum temperature was 25℃, and high concentration of nutriment was beneficial for acid-producing. The metabolized produce of WRF C incubated in PDY media could restrain growth, and keeping too much biomass was a great disadvantage for acid producing . Anaerobic microbiocal acidification, and filtrated by straw and treated by alkali-resistant fungi were three pretretment methods used in the protreatment. All of them could decrease pH of black liquor. When 20 percent black liquor was renewed everyday, pH could be lowered from 12.3 to about 11.3 after it was treated by anaerobic microbiocal acidification for one day, filtrated by straw followed, then pH could drop to about 10.3. At last, treated by alkali-resistant, pH could reduce 0.8. In the process of black liquor treated by WRF C, high concentration of black liquor could restrain growth and acid-producing. The supplying of oxygen had a primary influence on the time of COD and chroma removal, and if enough oxygen supplied, COD and chroma removaled more qiuckly. Diosgenin wastewater was abundant in nutrition and acid. The mixed wastewater of diosgenin wastewater and black liquor could supply enough nutrition and neuter pH, which could be treated effectively by WRF C. The results showed that it could effectively counteracted the alkaline of black liquor and the acidity of Diosgenin wastewater . The COD and chroma and the content of lignin of the mixed wastewater decreased 88.43%,86.0%,70.1%, and pH was lowered from about 6 to 3.7. All this will made it possible to treat the final outflow with the other wastewater from paper mill. To sum up, WRF C could produce organic acid effectively, and it was feasible to treat black liquor by WRF C. This might be a new and economical mothod for black liquor treatment.