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

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

Chapter 71: AVERAGE RESULTS OBTAINED WITH VARIOUS QUANTITIES OF SULPHATE OF ALUMINA.
By Allen Hazen
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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.

AVERAGE RESULTS OBTAINED WITH VARIOUS QUANTITIES OF SULPHATE OF ALUMINA.

As it appears that neither the turbidity nor the number of bacteria in the raw water has a material influence upon the percentage bacterial efficiency obtained, we can take the results given above, which include all the results obtained (except a very few abnormal ones) for computing the various efficiencies obtained with various quantities of sulphate of alumina. These results are graphically shown by Fig. 21, p. 167, on which lines have been drawn indicating the normal efficiencies from various quantities of sulphate of alumina as deduced from our experiments.

In computing the amount of sulphate of alumina which it would be necessary to use in operating a plant at a given place to give these efficiencies, the quantities of sulphate of alumina shown by the diagram can be taken as those which it would be necessary to use during those days in the year when the raw water was clear, or sufficiently clear, so that the amounts of sulphate of alumina mentioned would suffice to properly coagulate it.