• Wang, Lawrence K. and Wang, Mu-Hao Sung (2022). Closed water systems for recycling water and fibers in forest and paper industry with flotation and spray filtration. In: “Evolutionary Progress in Science, Technology, Engineering, Arts, and Mathematics (STEAM)”, Wang, Lawrence K. and Tsao, Hung-ping (editors). Volume 4, Number 7B, July 2022; pp.71. Lenox Institute Press, MA, USA. STEAM-VOL4-NUM7B-JULY2022. ISBN 978-0-9890870-3-2. …………ABSTRACT: The general technical approach of two total process water recycle systems in paper mills are introduced and discussed in this publication: (a) single-cylinder tissue or board machine closed water system; and (b) tissue machine closed water system using secondary fibers . The former (single-cylinder tissue or board machine) involves the use of a high rate dissolved air flotation (DAF) clarifier and conventional safety filters for treating white water, recycling the clean DAF effluent to felt pit and vacuum pumps, and recycling the DAF floated sludge containing concentrated usable fibers to machine chests for making more tissues. The latter (tissue machine) uses DAF for process water recycle, uses rapid spray filters for recovering all usable fibers and discharges the DAF floated sludge to waste when waste paper with high clay or ink content is used. Also introduced and discussed are the two innovative process equipment: (a) high rate DAF and (b) rapid spray filtration, which both were developed by the Lenox Institute of Water Technology (LIWT), but manufactured by Krofta Engineering Corporation (KEC) and its associated companies. Both high rate DAF and rapid spray filtration are introduced in detail. One case history is presented. This publication is one of many LIWT-KEC memoirs written for documentation of the organizations’ academic accomplishments in humanitarian advanced education and innovative process equipment development.