RO treatment of waste waters from dairy industry

An important problem in the dairy industry is posed by the disposal of very polluting wastes like milk whey (COD 60 000+70 000 mg/1) and washing waters. Reverse osmosis can be used to concentrate milk whey (C.F. 2.5+3) in the dairy industry thus obtaining a water stream that can be re-used for the process needs and a concentrated milk whey stream that can be sent to large treatment plants, reducing the transportation costs. The concentration of milk whey has been tested at pilot plant scale, using a 6001/hr RO unit. Figures one and two show the flow rates of feed and permeate for the milk whey concentration and retenate and permeate volumes respectively. Reverse osmosis can be used also as part of the process that allows the final and economically feasible disposal of milk whey [1]. This process consists of: 1. A fermentaiton section, where the lactose of the concentrated milk whey is converted to yeast. 2. A downstream processing section, where the fermentation broth from the fermentation section is centrifuged for the recovery of yeast, which is then dried using a spray drier. 3. A reverse osmosis section where the water stream from the downstream processing section is concentrated (C.F.10). The permeate stream has a low COD (about 5000 mg/1) and can be discharged or re-used for the process needs. The retentate stream can be recycled back to the downstream processing section to produce dry yeast used in fodder formulation. In this contribution all the experimental results obtained with the RO pilot plant above mentioned will be presented and discussed.The disposal of polluting wastes like milk whey and washing waters poses a problem in the dairy industry. Reverse osmosis (RO) can be used to concentrate milk whey thus obtaining a water stream that can be re-used for the process needs and a concentrated milk whey that can be sent to large treatment plants. The RO process consists of: a fermentation section; a downstream processing; and a reverse osmosis section. The experimental results from a pilot plant using a 600 l/hr RO unit to concentrate milk whey are discussed.