Comparative study between basic chemical and biological (sphagnum moss) method in decolourisation of paper mill effluent

The pulp and paper mill effluent is one of the high polluting industrial effluents. All the available methods for treatment of pulp and paper mill effluent have certain draw backs. This study involves comparison between the basic chemical precipitation and biological treatment for decolourisation of the effluent. For chemical precipitation, the metal salts of Aluminum (AlCl3) and Iron (FeCl3) were employed. For biological treatment, Sphagnum moss, known for its ability to act as biofilter was used. The color removal by aluminum chloride was effective in acidic conditions (pH 4.0-7.0) and the pH conditions close to 5.0 was optimal. A maximum color removal of 96.16% was achieved using aluminum chloride at pH 5.0 for the dosage 4.0 g/L. Ferric chloride was effective in removing color under acidic conditions in the pH range of 3.0- 6.0. The conditions close to pH 4.0 were found to be highly effective. A maximum color removal of 88.18% was observed at pH 4.0 for the dose of 2.0 g/L of ferric chloride. Effluent was treated with sphagnum moss for a period of 4.5 hours stand time; every 90min interval sample was eluted for testing and an exponential reduction in colour was observed. Stand time above 90 mins showed relatively less reduction. The conditions close to pH range of 5.5-6 with colour removal of 80.95% was achieved