The filtration of public water-supplies / Third edition, revised and enlarged.

Chapter 77: THE USE OF ASBESTOS.

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About This Book

This book presents a practical, engineering-focused treatment of water filtration for municipal supplies, combining historical perspective, design principles, and operational guidance. It explains types of filters, construction of beds and underdrains, selection and grading of sands and gravels, rates of filtration, head loss, and mechanisms for regulating flow. Procedures for cleaning, sand-washing, and intermittent operation are described alongside theoretical and bacteriological considerations that bear on efficiency. Methods for measuring and removing turbidity and color, the effects of suspended mud, coagulation practices, and numerous design examples and appendices illustrate how to plan, build, and maintain effective filtration works.

THE USE OF ASBESTOS.

It has been suggested by Mr. P. A. Maignen that the surface of sand filters should be covered with a thin layer of asbestos, applied in the form of a pulp, with the first water put onto the filter after scraping. The asbestos forms a sort of a paper on the sand which intercepts the sediment of the passing water. The advantage of the process is in the cleaning. When dried to the right consistency this asbestos can be rolled up like a carpet, and taken from the filter without removing any of the sand.

This procedure is almost identical with that which has occurred naturally in iron-removal plants, where algæ grow in the water upon the filters, and form a fibrous substance with the ferric oxide removed from the water, which can be rolled up and removed in the same way as the asbestos. The advantages of the process, from an economical standpoint, are less clear.