As stated by Smith in reference , recovering of caustic from mercerizing operations is also practical. Because mercerization is always a continuous process, these waste streams are easy to segregate . According to references  and , caustic can be recovered using double effect evaporators. As stated by Jones, , the effluent contains 5% NaOH and may be evaporated to 25 to 40% and then pumped to storage for reuse. According to reference , caustic strength is increased by evaporation to usable levels, approximately 30% by weight, followed by settling in conical settlers, reporting a caustic reclamation of up to 98% . The minimum levels of caustic strength and annual quantity needed for cost-effective reuse are about 2% and 400 tons, respectively as stated in . Jones considers that caustic recovery becomes economic when caustic use exceeds 11,300 tonnes per year of 100% cotton goods or 22,700 tonnes per year of 50/50 cotton polyester fabrics .
References from reviewed literature:
In : J.S.Badin and H.E. Lowitt, The U.S. Textile Industry: An Energy Perspective, DOE/RL/01830/T-56, prepared by Energetics, Inc. for Pacific Northwest Laboratory, Richland, Washington, 1988