Over the last 5 years, the Green Bay Packaging corrugating medium mill has converted to an essentially closed process water system. The mill is a net consumer of water. This is due to the greater amount of water carried out of the system with the sheet compared to the lower water content entering the process system in raw materials. Many small dilute water streams are accepted into the process without upsetting the water balance. When extraneous water inputs do upset the system balance, the condition is correctable by thermal evaporation or reverse osmosis. The reverse osmosis plant design operating performance and economics are described. Although many reverse osmosis operating problems have been solved, flux rates are somewhat lower than had been predicted. Other system additions and revisions for process water entrapment, recycle, and surge protection are described. When a spill cannot be prevented, a monitoring system is used by production personnel for early detection and correction. Included in key areas is redundant equipment to help correct failures quickly. Levels of BOD loss have been reduced from the 20,000 pounds per day range (9072 kg/day)--1971-- to less than 1000 pounds per day (454 kg/day)--monthly average-- for 1975. The daily maxima of 4000 pounds per day (1814 kg/day) has not been exceeded in any mill operating day during 1975. This report covers a period from July 19, 1972, through February 2, 1976.

This report was submitted in fulfillment of Grant no. S-800520 under (partial) sponsorship of the Office of Research and Development, U.S. Environmental Protection Agency.