AWWA JAW17204

The research described in this article addresses the problems of small water systems faced with the need to construct treatment facilities that are easy to operate and maintain and yet produce water that meets drinking water standards. Recent outbreaks of waterborne giardiasis are reviewed, and the need for more than one barrier (ie, chlorination) to disease transmission is emphasized. Characteristics of rapid and slow sand filtration are described and their strengths and weaknesses as second barriers for protecting public health are discussed. Results of a pilot study indicate that when raw water quality is high, slow sand filtration outperforms direct in-line filtration operating with alum or cationic polymer as a coagulant. This conclusion was substantiated by turbidity, particle count, and total coliform data. Enumeration of algae or a surrogate measure of algal population is essential for judging the acceptability of a raw water for slow sand filtration. For waters of poorer quality, direct in-line filtration can be used, but the system requires substantially more operational skill and attention. Both slow sand filtration and direct in-line filtration exhibited a period of poor filtrate quality at the beginning of filter runs, and therefore require a filtering-to-waste period if Giardia cysts are a concern. Includes 19 references, tables, figures.

Product Details

Edition:

Vol. 76 - No. 12

Published:

12/01/1984

Number of Pages:

12

File Size:

1 file , 3 MB