Wastewater Treatment Method Selection for Small-Scale Pulp and Paper Mills

Black liquor, a toxic byproduct from the kraft pulping process in pulp and paper mills, is traditionally treated by being passed through multiple effect evaporators and burned in a recovery boiler to produce energy and recover chemicals. However, traditional treatments of black liquor are not viable for small-scale Kraft paper mills in Muzaffarnagar, India, due to the low alkali and total solids concentration of their black liquor.

In this research, alternative treatment methods, including low temperature incineration and membrane filtration, are explored to determine their effectiveness and economic viability for industrial scale black liquor treatment. For low temperature incineration, field surveys will be carried out to determine how total expense varies with operating conditions. Membrane filtration will be studied on a lab scale to determine its effectiveness of treatment by considering the associated cost for filtering out lignin from black liquor and the benefit from the value of lignin.

In the short run, we hope to focus on the viability of membranes as a treatment method. In the long run, a strategy for selecting treatment methods including traditional recovery boilers, low temperature incinerator and membrane filtration based on the different pulping and mill operation conditions can be developed, and recommendations for the optimal treatment method will be made accordingly for the small-scale Kraft paper mills in Muzaffarnagar.

We hope that with the help of the Central Pollution Control Board, this method selection guidance can serve small-scale pulp and paper mills across the landscape in their wastewater treatment planning, encourage them to select the most effective method that minimizes their cost of treatment, and overall reduce the emissions of black liquor across India.