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Types as per
1. Volume
2. Purpose
3. Water type
Stages of the treatment process
- Mechanical processing systems
1- Filtration
2- Separate of oil
3- Homogenization ponds
- Physical therapy systems
1- Sedimentation
2- Flotation
- Chemical treatment systems
1- Oxidation
2- Chlorination
- Biological treatment systems
1- Activated Sludge
2- Secondary Ventilation
Sewage treatment stages:
Sewage is generally subject to the following main treatment stages:
1 - The primary treatment stage.
2- The initial treatment stage.
3- Secondary (biological) treatment stage.
4 - Triple treatment stage.
5- Sludge treatment.
Primary treatment stage
- This primary treatment aims to remove large-sized inorganic solids as well as fibers from sewage to protect mechanical installations and the various pumps present in the later stages of treatment.
- This stage also aims to homogeneity of this water, especially when the sewerage network Joint or when pouring into the station from time to time large quantities of industrial wastewater.
Stage components:
a) Strainers
Soft or rough and placed at the beginning of the station to reserve and remove large-sized solid materials.
b) Shredding devices
They are used to shred and cut solid materials (Stones) that have passed through the strainers and are placed before the pumping stations.
c) Sand deposits
Their purpose is to remove sand and fine gravel materials that have passed through the strainers and thus reduce the size of the sediments in the sedimentation basins
1. Horizontal runoff sand chambers
2. Vortex sand chambers
d) Modification basins
Their purpose is to reduce the severity of changes in the amount of flow or the intensity of the sewage that reaches the treatment plant in order to obtain a semi-constant flow rate and a semi-constant concentration of the pollutants in the sewage entering the treatment.
The Initial treatment stage
This treatment aims to reduce the values of pollutants in sewage, in particular the disposal of all easily deposited solid plankton and thereby reduce the concentration of suspended solids and organic pollution.
Stage components:
a) Flotation basins
They are used to remove grease and oils when they are present in a high percentage in sewage mostly from industrial sources, in order to avoid impeding treatment and the spread of unpleasant odors.
b) Primary sedimentation basins
To separate and completely remove the fully settable soft solids, which constitute a remarkable percentage of which are some inorganic materials that are a burden on the next biological treatment stage
Secondary (biological) treatment stage
- It is considered the most important stage of treatment that must be applied to the polluted water in the plant.
- This treatment aims to oxidize the various organic materials in sewage and convert them into stable compounds mostly of bacteria and some microorganisms that can be separated from the water and treated separately and thus obtain water practically free from pollution.
- Secondary treatment is carried out in two main units:
- Ventilation tanks
- Secondary sedimentation tanks.
Biological treatment types:
a) Activated sludge
Includes different types of aeration tanks
- Conventional
- Segmented feeding
- Complete mixing
- Extended ventilation
b) Fixation pools
c) Ventilated basin.
d) Biological filters.
e) Biological Turntables pool.
Triple treatment stage
Considered as an additional treatment in order to achieve the following:
1. Removing the soft suspended matter in the final treated water.
2. Reducing the concentrations of pathogens such as bacteria and others, so that any public health harm that can result from them is avoided.
3. Control and remove nutrients (phosphorous - nitrogen) and dissolved solids.
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