Measures against water pollution in the iron and steel industry.

During the last ten years or so, a number of statutory provisions have been enacted with the eventual object of controlling and restricting the amount of pollution which can be permitted or tolerated in the water systems of the European Continent. Against this background the authors examine the iron and steel industry as it exists in France, tabulating the principal processes likely to be encountered in plants producing coke, coke-oven gas, ores. sinters. pig iron, cast iron, various slags and finished steel in a wide variety of forms. Estimates are given of probable amounts of pollutants which would be produced in the absence of purification treatment, and of water requirements in different kinds of plants. The cost of purification is high and it is emphasized that plants must be sited to give an acceptable compromise between cost of raw materials and water, and the benefits which may be derived either by way of end products or by reduction of need for water through adoption of recirculating systems wherever possible or through reduction of pollution by purification. The financial penalties incurred if pollution is caused are briefly discussed and it is emphasized that new more stringent administrative powers will be necessary to achieve a pollution-free environment. It is noted that biological treatments have to be used with care, it being too easy to allow 'poisonous' material to enter a purification circuit and render it useless, the special nature of coke plant effluents being a case in point. The work of Water and Atmospheric Pollution Committees is particularly noteworthy. It is stated that the latest iron and steel plant built in France has practically no discharge and does not pay any pollution tax, while old establishments can be charged considerable amounts. 1. NATURE OF THE INDUSTRY The iron and steel industry aims to put at the users' or manufacturers' disposal products composed mostly of iron, bonded or combined with a certain amount of elements, mainly carbon, which determine their properties. Starting with the ore—a more or less complex iron oxide compound—a complete series of operations is required to obtain the finished products (sheets, beams, rails, concrete rods, wire rod, various structural steel shapes). The works where all the operations of this series are accomplished are called integrated plants. However, in some plants, this series is incomplete, at least in part, and the best method is to break down the basic line into various elements and to describe each of them.