Measures against water pollution in industries producing edible oils and fats.

Edible fats and oils are produced by three main industries: oil, margarine and rendering. As margarine manufacture requires only substances that have already undergone refining, the only waste water comes from rinsing the equipment and premises. The oil industry with its different phases of refining uses large quantities of water but could cut its consumption by a more rational organization of the different circuits. Animal fats processing (rendering), treating raw materials which are easily and rapidly decomposable, uses large quantities of water, not only for washing the raw material but also for thorough cleaning of the premises. This industry could reduce pollution through appropriate improvement in the preparation of the raw material and its collection. In any case, the successful treatment of polluted water lies in the correct application of modern processes for filtration, settling, precipitation, and other and chemical and biological treatments. Through them, the solid particles in suspension are eliminated, the fatty matter carried off is separated and recovered, emulsified matter is precipitated by flocculation, and the discarded water conforms to prevailing regulations on the discharge of waste water into sewers and streams. In order to decide upon the exact measures to be taken against water pollution in industries producing edible fats and oils, it is first necessary to know the precise causes and nature of the pollution. Then, we shall study methods of eliminating it or reducing it, in general and in specific cases. These examinations will be undertaken successively for the three classes of industries producing edible fats and oils: oil factories, the raw materials of which are oleaginous seeds and the pulp of certain fruits; margarine factories, which use oils and animal fats; animal fats factories, treating animal fats: land (tallow, lard) and sea. OIL INDUSTRIES Nature and proportion of the different types of waste water Until recent years, all waste water was disposed of, even if it had been used only for the production of steam or for heat exchange. At the present time, we are obliged to discharge as little waste water as possible, which leads us to consider three types of water: (a) Water returned from the heating system of the equipment (non-polluted).