Manufacturing Publications : RECYCLING OF WHITE WATER AT SWEETWATER PAPER
Sweetwater paper reduced white water discharge by recycling wastewater in their manufacturing process.
Sweetwater Paper produces wallboard backing made from recycled paper. The paper is not deinked. Waste paper is repulped; new backing board is then made on a paper machine. Water removed from the board during sheet forming and drying is sent to a wastewater treatment plant where it undergoes clarification and pH adjustment. The majority of the water is then recycled with a small discharge of 180 gallons per minute. Sweetwater manufactures approximately 320 tons per day of wallboard backing.
Calcium sulfate is the most problematic component in the recycled water stream. Calcium sulfate is brought into the plant as a component of the waste paper. If the concentration becomes too great, calcium sulfate crystals can form within the plumbing system resulting in blockages. Sweetwater maintains solubility by adjusting pH and limiting water discharge to prevent crystallization.
Sweetwater discharges 810 gallons per ton of product, which is two to four times lower than is expected for this type of mill. In addition to recycling water, clarifier sludge is added back to the process. The only solid waste generated is from foreign materials such as plastic strapping present in the incoming waste paper.