The importance of wastewater treatment in the food industry is growing nowadays, because of the rising cost of water and because of environmental pollution. The aim of this study was to decrease the chemical oxygen demand (COD) of two different wastewaters originated from the food industry. If the treated water is drained into natural water, the COD has to be below 125 mgO(2)/L, if it is released into sewer the limit is 800 mgO(2)/L. Reverse osmosis and nanofiltration membranes were investigated for wastewater treatement. Experiments were carried out at constant temperature and recycle flow rate, the permeate flux, salt rejection and COD were measured continously. During concentration experiments the fouling of the membranes was observed.