Large amounts of wastewater derive from the food industry. Water recycling by means of membrane tech- nology may offer promising cost savings, although it might involve some problems. Wastewater deriving from the treatment of fruits and vegetables, the processing of milk, and the slaughtering of cattle and sheep can be highly polluted by dissolved organic compounds. The higher the organic load expressed as chemical oxygen demand (COD), the lower the treatment efficiency is. High COD of the wastewater results in reduced filtrate flux and permeate flux of the membranes for microfiltration, ultrafiltration and reverse osmosis, and also re- duces the selectivity of the membranes for reverse osmosis. In order to upgrade dairy farm wastewater with a COD of 984 mg/l, microfiltration combined with reverse osmosis is sufficient to guarantee the limiting values for discharge into surface waters and to obtain a water quality which allows reuse as process water. The treat- ment of slaughterhouse wastewater (COD = 1,737 mg/l), however, requires a second stage of re-verse osmosis. The results of this study represent benchmarks, which may be utilised for long-term studies on a technical scale in order to design full-scale equipment.
