The 2 Volumes

Chapter 9. Pre-treatments (38 pages)

chapter 9: page example


Urban wastewater sewers carry a wide range of matter that is often bulky, especially in the case of combined systems.
A pre-treatment is necessary in order to protect raw water lifting systems and pipelines against blockages as well as other treatment equipment against abrasion and, more generally, to remove anything that might interfere with subsequent treatment.

The following constitute pre-treatment operations (a water treatment plant can comprise one or more of these operations, depending on its importance and raw water quality):

Similar operations can be carried out on:

On the other hand, sludge removal, required to protect certain settling tanks against a major inflow of suspended solids, is sometimes considered to be a pre-treatment whereas, in fact, it is really static settling; this aspect will be discussed:

We also need to highlight two major trends in modern plant:

This means that the only by-products that still have to be removed are those retained by the «dewatering» screen (similar to house-hold waste) and re-usable grit.

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