A liquid treatment system, in particular for concentrating milk, and method therefor. The system includes an inlet configured to receive fresh raw milk; and a pressure vessel connected to the inlet. The pressure vessel is provided with a pressure system configured to realize a pressure of at least 10 bar in the pressure vessel. A reverse osmosis membrane is included for filtering the raw milk. A pump is provided for pumping the raw milk under pressure out of the pressure vessel and through or along the reverse osmosis membrane. A permeate outlet is provided for the separated water and a milk outlet is provided for the concentrated milk.