NOVELTY - Converting ligno-cellulosic biomass feedstock having lignin and carbohydrates of glucans and xylans involves pretreating ligno-cellulosic biomass feedstock with treatment water, converting a portion of glucans and xylans to chemicals other than glucose and xylose to create ligno-cellulosic biomass stillage; converting the stillage to products other than lignin by exposing the stillage to hydrogen and first catalyst to produce liquid phase; recovering treated water; and using the treated water in waste water treatment process.    USE - For conversion of a ligno-cellulosic biomass feedstock containing lignin and carbohydrates of glucan and xylan (claimed) into polyester intermediates, which is used in polyester preforms and bottles.    ADVANTAGE - The process is a continuous process to convert lignin as found in ligno-cellulosic biomass before or after converting at least some of the carbohydrates; and has high yield for conversion of biomass feedstock i.e. approximately 80% of the lignin in the feedstock is recovered as usable products.    DETAILED DESCRIPTION - An integrated process for the conversion of a ligno-cellulosic biomass feedstock containing lignin and carbohydrates of glucans and xylans involves pretreating the ligno-cellulosic biomass feedstock with treatment water which includes steam explosion to create a pre-treated ligno-cellulosic biomass feedstock, converting at least a portion of the glucans and xylans to chemicals other than glucose and xylose and their respective glucose and xylose oligomers and polymers to create a ligno-cellulosic biomass stillage comprising lignin, a pre-treatment biological oxygen demand (BOD) concentration and a pre-treatment chemical oxygen demand (COD) concentration; converting the lignin of the ligno-cellulosic biomass stillage to products other than lignin by exposing the ligno-cellulosic biomass stillage to hydrogen and a first catalyst to produce a liquid phase at 25 degrees C; recovering a treated water from the liquid phase having a post-treatment BOD concentration and a post treatment COD concentration, both of which are 50% less than the pre-treatment BOD and COD concentration; and using the treated water in at least one of the steps selected from waste water treatment process and any process step preceding recovering the treated water from the liquid phase.