Dear Carlos, ...

Dear Carlos,

Physicochemical methods  

Physicochemical methods   like coagulation with lime or iron salts, ultrafiltration etc. have not been very effective for color removal of pulp & paper mills effluents. Adsorption of activated carbon is a common method for color removal of industrial effluent but the high cost is a limitation for its use for pulp & paper mills. Therefore attempt has been to find out low-cost adsorbent material for removing color of effluents of the industries. Coal fly ash of power plants has been used as an adsorbent for removing metals like Hg,Pb,Cd, Zn and Fe from water (De, 2005; De & Lal, 1990).But use of coal fly ash for color removal of Pulp and paper effluents has not been reported. In the present investigation , coal fly ash has been  used for the color removal of pulp and paper mill effluents. Coal fly ash is an efficient adsorbent in removing color of pulp and paper mill effluents.100% color removal was achieved at pH 6.8 and above.

Effect of pH

Effect of pH Effect. of pH on  color removal of the paper mill effluent was studied using 0.5 M NaOH or 0.5 M HCl (Fig. 2). 100% color removal took place at pH 6.8 and above. This result is significant as normal pH of paper mill effluents are above 8.0,  the method may be used  for color removal of pulp and paper mill effluents without any pH adjustment.

Colour removal by active and gamma sterilized compost

Color removal experiments using active and gamma sterilized compost showed that the color removal capacity for both wastewaters was nine times higher when using active compost than for those reactors using gamma sterilized compost. Final decolorization for pulp mill upset tank and E stage filtrate was 91 and 83%, respectively, while only 33% decolorization was achieved with gamma sterilized compost. Kinetic tests also showed higher color degradation rates when using active compost compared to sterilized compost. Additional experiments demonstrated that biological color removal appears to be robust with respect to pH and is largely unaffected by pH over a range from pH 5 to 10, typical values for the effluents in paper mills. The effect of aging in sorption were tested and results showed that virgin compost could establish a microbial population in less than 50 days which resulted in a compost with sorption capacity similar to the aged compost.

Colour removal by Membrane

Membrane technology has become widely accepted in many seawater and brackish water  treatment applications and these days it is more often used also in variety of waste water treatment processes as the final treatment step of water re-use process. In addition to traditional use of membranes for desalination, new requirements have been challenging membrane manufacturers to develop special products for selective removal of hardness, natural organic matter, color, fats, proteins and other macromolecular species. Nanofiltration (NF) membranes are usually used for selective removal of certain species in applications when TDS reduction is not a priority.

Colour removal Coagulation Process

The pulp and paper mill effluent is one of the high polluting effluents amongst the effluents obtained from polluting industries. All the available methods for treatment of pulp and paper