Scientists at the Centre for Advanced Studies in Botany from University of Madras successfully evaluated the efficacy of white rot fungus Ganodema lucidum for reduction of the colour of paper mill effluents under various growth conditions. Results indicated Ganodema lucidum decolourises the paper mills effluents that were recognised as environmental hazards.

The untreated effluents from pulp of paper mills discharged into water bodies damages the water quality. The brown colour imparted to water due to addition of effluents is detectable over long distances. The effluents have a high biological and chemical oxygen demand (BOD and COD), lignin compounds and their derivatives. The dark brown colour is due to the formation of lignin degradation products during the processing of Lignocell Ulosics for paper and pulp manufacture. As the lignin derivatives are highly resistant to microbial attack, they escape the wastewater treatment. Because of their ability to degrade lignin, several microorganisms have been tried for biological treatment of such effluents.

K Perumal, K Murugesan and P T Kalaichelvan collected effluents from Karur Paper Mill at three different places and filtered them through a sieve to remove suspended particles. They then studied the physiochemical characteristics of the effluents before and after treatment with fungal strains under various growth conditions.

Effect of different carbon sources, nitrogen source, different pH, temperatures and various inoculum concentrations on de-colourisation of effluents, BOD, COD and. lignin contents were also studied. Maximum colour reduction (89 per cent) was observed on the 18th day of fungal growth with pH adjusted to 6.5 at 35 degrees Celsius. Peak reduction of BOD and COD along with maximum removal of lignin were also observed on 18th day.

The scientists found activity of enzymes lignin peroxisdase and laccase in the effluents treated with fungus. They also found that the two enzymes were produced extra-cellularly by the fungus.

Addition of carbon sources stimulated the fungus to maximise decolourisation and reduction of COD and lignin content in the effluents. The highest growth of fungus was observed with addition of glucose, maltose and xylose.

Source: Search, May 2001