文档介绍：Engineering of Water Quality Control
Theory and Performance of
Deep-Bed Filtration
1. An overview of potable Water filtration
Concept of filtration

The filtration processes discussed in here are used primarily to remove particulate material from water.
the Classification of filtration:

filtration style: granular bed filtration, precoat filter
filter media: sand, anthracite coal , GAC, DE
filtration hydraulic: gravity filters, Pressure filters
rate of filtration: rapid granular bed filter, slow sand filter
distribution of deposit: depth filtration, cake filtration
Dominant Mechanisms, Performance, and Applications
(1) Cake filtration
Cake filtration of particulates involves physical removal by straining at the surface.
The mechanism of cake filtration is largely physical straining.
Chemical pretreatments such as coagulation and sedimentation are not generally provided.
The source water must be of quite good quality .
Slow sand filtration
The surface cake of accumulated particulates includes a variety of living and dead micro- and anisms.
The biological metabolism of anisms enhances removal of particulates.
As the filter cake develops, the cake itself assumes a dominant role in particulate removal.
Because of this, filtrate turbidity improves as the filter run progresses, and deterioration of the filtrate turbidity is normally not observed at the end of the filter cycle.
(3) Rapid granular deep-bed filtration
Depth filtration involves a variety plex mechanisms to achieve particulate removal.
The small particles could be captured in bed by transport and attachment process in series.
Transport process are needed to carry the small particles into contact with the surface of the individual filter grains.
Attachment mechanisms hold the particles to the surfaces.
Chemical pretreatment is essential to particulate removal in depth filtration.
Regulatory Requirements for Filtration
“community water systems must disinfect all surface waters and fi