Removal of microorganisms from water by columns containing sand coated with ferric and aluminum hydroxides

Tap water seeded with different microorganisms or untreated waste water was passed through columns containing sand modified by the in situ precipitati on of metallic hydroxides or unmodified sand. Columns (35.5 x 5.0 cm) packe d with 1 kg of sand modified with a combination of ferric and aluminum hydr oxide removed greater than 99% of Escherichia coli, Vibria cholerae, poliov irus 1 and coliphage MS-2 from dechlorinated tap water. This removal effici ency was consistent throughout the passage of 120 1 of water during a 30 da y test. After the passage of 1921 of tap water, these columns were still ab le to remove 99.9% MS-2, 80% E. coli and 90% of poliovirus 1. Columns conta ining modified sand efficiently removed microorganism from water samples at the various pH and temperature values tested while columns containing unmo dified sand did nor:. In addition, these modified sand filters were able to remove coliform bacteria and coliphage from raw sewage. More than a 4 log( 10) reduction in the numbers of these microorganisms was achieved at room: temperature. The modified sand seems to better remove microorganisms due to increased electrostatic: interactions. Neither E. coli nor MS-2 were inact ivated by the modified sand column effluents. The ml:tal used for coating t he sand could not be detected in the column effluents, indicating that the coatings were stable. (C) 1998 Elsevier Science Ltd. All rights reserved.