A process for the treatment of ligno-cellulosic biomass, comprising the steps of A) Introducing a liquid stream comprised of water and a feedstream comprised of ligno-cellulosic biomass solids comprised of cellulose, sugars, into a pre-soaking vessel, B) Pre-soaking the feedstream with the liquid stream at a temperature in the range of 10°C to 150°C, C) Separating at least a portion of liquid stream from the solids to create a first solids product stream and a pre-soaked liquid product stream, and D) Treating the first solids stream with a soaking step comprising the steps of 1) Soaking the first solids stream in vapor or liquid water or mixture thereof in the temperature range of 100°C to 210°C to create a second soaked biomass containing a dry content and a soaked liquid; 2) Separating at least a portion of the soaked liquid from the second soaked biomass to create a soaked liquid stream comprised of suspended solids, monomeric sugar, oligomeric sugars, acetic acid, and furfural and a second solid stream; wherein the second solid stream comprises the second soaked biomass, E) Separating at least a portion of the soaked liquid from the suspended solids of the soaked liquid stream comprising monomeric sugars, oligomeric sugars, acetic acid, and furfural, F) Filtering at least a portion of the acetic acid from the at least a portion of the soaked liquid to create a permeate and a retentate, wherein the filtering comprises nano-filtration. A) Introducing a liquid stream comprised of water and a feedstream comprised of ligno-cellulosic biomass solids comprised of cellulose, sugars, into a pre-soaking vessel, B) Pre-soaking the feedstream with the liquid stream at a temperature in the range of 10°C to 150°C, C) Separating at least a portion of liquid stream from the solids to create a first solids product stream and a pre-soaked liquid product stream, and D) Treating the first solids stream with a soaking step comprising the steps of 1) Soaking the first solids stream in vapor or liquid water or mixture thereof in the temperature range of 100°C to 210°C to create a second soaked biomass containing a dry content and a soaked liquid; 2) Separating at least a portion of the soaked liquid from the second soaked biomass to create a soaked liquid stream comprised of suspended solids, monomeric sugar, oligomeric sugars, acetic acid, and furfural and a second solid stream; wherein the second solid stream comprises the second soaked biomass, 1) Soaking the first solids stream in vapor or liquid water or mixture thereof in the temperature range of 100°C to 210°C to create a second soaked biomass containing a dry content and a soaked liquid; 2) Separating at least a portion of the soaked liquid from the second soaked biomass to create a soaked liquid stream comprised of suspended solids, monomeric sugar, oligomeric sugars, acetic acid, and furfural and a second solid stream; wherein the second solid stream comprises the second soaked biomass, E) Separating at least a portion of the soaked liquid from the suspended solids of the soaked liquid stream comprising monomeric sugars, oligomeric sugars, acetic acid, and furfural, F) Filtering at least a portion of the acetic acid from the at least a portion of the soaked liquid to create a permeate and a retentate, wherein the filtering comprises nano-filtration.