文档介绍：Introduction:
We will start with an overview of treatment processes
1) Why do we treat water and wastewater?
The main objectives of the conventional wastewater treatment processes are the reduction in biochemical oxygen demand, suspended solids and anisms.
It also may be necessary to remove nutrients such as N and P, ponents, non-biologically pounds and dissolved solids. Removal of these materials are necessary for the simple reason that discharge to the environment will result in “damage” of some sort.
Of course the damage is a function of the type of pollutant discharged -- heavy metals = toxicity, organic matter = oxygen depletion, N or P- eutrophication, etc. In the case of water treatment the objective is to remove contaminants from the water which can result in health or aesthetic problems.
2) What are the materials in water and wastewater that we must remove?
There are a wide range of these pollutants (contaminants) ranging from municipal sewage to highly specific industrial wastes. The usual approach in discussing treatment schemes is to categorize pollutants into general classes so that a general class of treatment methods can be applied.
Note that many pollutants fall into several categories. For example, some anic matter (one category) is in the form of suspended solids (another category), so removal of SS sometimes results in the removal anic matter. As an example consider the content of typical municipal wastewater as represented by its solids content.
Total Solids ( 400 –1200 mg/L)
anic (ash)
50%
Organic (volatile)
50%
Dissolved . 35%
Suspended (>1 m) 45%
(15% ) (30% )
Dissol.
organic
20%
Non-settleable
anic
40%
Settleable (>10m)
25%(10% )
(15% organic)
Non-anic
35%
Each solids “type” may require a different type of treatment process. We generally try to remove large very settleable or screenable particles first and then proceed to the smallest and finally to the soluble species.
3) To what level do we need to remove contaminants?