| 摘要 |
<p>A particulate material suitable for forming a bed for waste water treatment comprises pellets of a plastics material, e.g. high density polyethylene, whose surface is at least partially coated with smaller particles of sand and salt. The material may be made by mixing pellets of the plastics material with a mixture of sand and salt that has been preheated to a temperature between that at which surface melting of the pellets takes place and that at which a substantial proportion of the pellets agglomerate. After mixing the particulate material is separated from the sand and salt, and the pellets of plastics material having sand and salt embedded in their surface are recovered. On washing, the salt is removed to form voids which provide a habitat for microorganisms, and the material can be used in static or fluidised bed waste water treatment.</p> |
