Treatment of
Wastes Originating from Metal Industries
DR. -ING. A. MONTENS,  Sanitary Engineer
Emschergenossenschaft
Essen, Germany
INTRODUCTION
The wastes of the metal industry, not only of ferrous metals but also of non-
ferrous metals, are different. Independent of the species of the manufactured
metals, wastes are derived in the process from rolling, pickling and by handling
the metal-surface, also called metal-finishing.
The raw material -- iron, steel or other metals --is primarily rolled into
belts, sheets, pipes or wires.   The rolling is performed either hot or cold.
In hot-rolling the wastes are polluted with undissolved iron and by oil and fats
from the roll-stands.
On the hot-rolled material a scale is formed, which must be removed before
further processing. The removing of scale may be realized by mechanical or
chemical means. But the mechanical descaling is not as effective and not sufficient in most cases for the further treatment and finishing. Therefore the metal-
surface is nearly always pickled in acids. The metals are most often pickled in
sulphuric or hydrochloric acid.
In pickling two kinds of wastes result: the concentrated pickling liquids, and
the rinsing-water. Both kinds of wastes are polluted by dissolved iron salts (sulphates or chlorides) and by free acids. But the concentration of both wastes is very
different. The iron content of the pickling liquid lies between 70 and 150 g/1,
the acid-content between 10 and 15 per cent. The rinsing waters have concentrations of five g/1 of acid and metal-contents of between 0. 5 and one g/1.
After the pickling the material is cold rolled or drawn. The rolls and cold
drawing machines must be lubricated and cooled and oil-emulsions are used for
this purpose. Finally the metal-surface is handled or finished. This is accomplished primarily by galvanization. The wastes of this process contain the used
electrolytes, degreasing agents and cyanides.
Other wastes may be derived from phosphatizing, hardening and buffing. They
are generally treated with the galvanization wastes.
Last year Dr. Rincke spoke at the Purdue Conference about the treatment of
pickling and plating wastes in particular plants in West Germany (1). In this paper
equipment and measures for the treatment of wastes other than those mentioned by
Dr. Rincke will be considered. Some additions will be made to the explanations
of Dr. Rincke.
EQUIPMENT FOR THE TREATMENT OF WASTES FROM HOT-ROLLING-MILLS
This waste must be cleansed of scale and oil. The conventional method to do
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