Treatment of dairy industry wastewater by reverse osmosis for water reuse

The dairy industry is among the most polluting of the food industries in volume in regard to its large water consumption. The present work was related to investigations about practices of water management of 11 dairy plants. Treatment of the process water produced in the starting, equilibrating, stopping and rinsing processing units was proposed to produce water for reuse in the plant and to lower the effluent volume. Reverse osmosis of such wastewaters, collected in dairy plants, was performed after a prior check of their stability during storage. Filtration performances were focused on permeate flux versus water recovery and on water quality (TOC, conductivity). Reverse osmosis water similar to available vapour condensates (produced in drying processes) can be achieved allowing this water to be reused for heating, cleaning and cooling purposes. A 540 m2 RO unit is required to treat 100 m3/d of wastewater with 95% water recovery.