Closing water loop in a paper mill section for water conservation and reuse

Abstract

Water is critical to paper production and increasing competition from other users has reduced water availability to paper mills in recent years. The study was conducted at a large-scale integrated pulp and paper industry. The study conducted at laboratory for recycling of effluents was aimed at reducing water foot print of the paper mill. Paper machine section effluent was identified for treatment and reuse based on the flow and characteristics. Chemical aided clarification and simple membrane filtration systems were used for water recovery. Closing the water loop through suitable treatment for reuse of wastewater in the paper mills provides an assured and continuous source of water. Pollutant reductions at the rate of 87.5%, 75% and 89% were obtained on SS, COD and turbidity, respectively. Operational and capital costs were delineated for selection of treatment option and enhanced water recovery. Feasibility of micro/ultra filtration combination was assessed to reduce costs for water recovery. This combination removed up to 93% and 91.7% of SS and COD from the effluents. The treatment options assessed for water recovery reduced freshwater consumption by about 40% and the excess treated water was stored in ponds for process use during the lean season.