NOVELTY - Method for manufacturing a hydroxycarboxylic acid product from lignocellulose-based raw material, involves using a first effluent used as a raw material, concentrating the raw material to provide a concentrate, treating the concentrate by a hydrolysis to form saccharides, fermenting the saccharides to form hydroxycarboxylic acid, and controlling the pH of the fermentation using a second effluent.    USE - The method or apparatus is useful for manufacturing hydroxycarboxylic acid product from lignocellulose-based raw material. The hydroxycarboxylic acid product is used as chemical, biochemical and/or polymer component. The hydroxycarboxylic acid product is chosen from glycolic acid, 3-hydroxypropanoic acid, lactic acid, succinic acid, xyloisosaccharine acid, anhydroisosaccharine acid, 3,4-dihydroxybutyric acid, 4-hydroxybutyric acid, glyceric acid, maleic acid, citric acid, oxalic acid and their combinations (all claimed).    ADVANTAGE - The method and apparatus utilize different types of pulp mill effluents which have not been utilized cost-effectively before to form valuable products. The second effluent is used as an adjust chemical in the pH controlling of the fermentation, and the second effluent includes carbohydrates, which are simultaneously a raw stock of the hydrolysis. The use of the alkaline bleaching filtrate as the second effluent in the pH controlling gives the technical effect that the hydrogen peroxide residues in the filtrate kill all the unwanted bacteria in the first effluent. The method and apparatus provide good product yield, and the products are provided cost-effectively and with low production costs.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) apparatus for performing the above-cited method, comprising an effluent feeding unit (20) for feeding a first effluent used as a raw material to the apparatus, a first concentration device (10) for concentrating the first effluent to provide a concentrate, a hydrolysis and fermentation unit for treating the concentrate by hydrolysis to form saccharides and for fermenting the saccharides to form hydroxycarboxylic acid, and a pH controlling unit for controlling the pH of the fermentation using a second effluent; and    (2) use of a bleaching filtrate in controlling the pH of hydrolysis and/or fermentation of a pulp mill effluent in hydroxycarboxylic acid product manufacturing.    DESCRIPTION OF DRAWING(S) - The drawing shows flow chart illustration of apparatus for manufacturing hydroxycarboxylic acid product from lignocellulose-based raw material.    First concentration device (10)    Hydrolysis device (11)    Fermentation device (12)    Second filtering device (14)    Second concentration device (15)    Dewaterer for removing water (17)    Effluent feeding unit (20)