122
5.2.2.17 Chemical Precipitation
Chemical precipitation is used for removal of organic compounds, phosphorous, as
well as nitrogen using precipitating agents. Electrocoagulation is achieved to
remove impurity by precipitation by passing ions into water from a dissolving anode
(typically iron or aluminium) with application of electric current.
Chemical precipitation normally involves the following steps:
1. Addition of reagents and adjustment of pH
2. Flocculation
3. Sedimentation
4. Solid–liquid separation
5.2.2.18 Filtration
Wastewater treated up to secondary stage will still have suspended solids and needs
further treatment if it needs to be reused. The wastewater treated in secondary stage
is filtered to remove suspended solids. Filtration is explained in Sect. 5.2.1.4.
Figure 5.12 shows examples of pressure sand filter and activated carbon filter.
5.2.2.19 Activated Carbon Filter
The wastewater after filtration is passed through activated carbon filter if the
standard demands further reduction in organic content for reuse or as a pretreatment before reverse osmosis. Proper granular activated carbon selection can
Fig. 5.12 Pressure sand filter and activated carbon filter
5 Water and Wastewater Treatment
5.2.2.17 Chemical Precipitation
Chemical precipitation is used for removal of organic compounds, phosphorous, as
well as nitrogen using precipitating agents. Electrocoagulation is achieved to
remove impurity by precipitation by passing ions into water from a dissolving anode
(typically iron or aluminium) with application of electric current.
Chemical precipitation normally involves the following steps:
1. Addition of reagents and adjustment of pH
2. Flocculation
3. Sedimentation
4. Solid–liquid separation
5.2.2.18 Filtration
Wastewater treated up to secondary stage will still have suspended solids and needs
further treatment if it needs to be reused. The wastewater treated in secondary stage
is filtered to remove suspended solids. Filtration is explained in Sect. 5.2.1.4.
Figure 5.12 shows examples of pressure sand filter and activated carbon filter.
5.2.2.19 Activated Carbon Filter
The wastewater after filtration is passed through activated carbon filter if the
standard demands further reduction in organic content for reuse or as a pretreatment before reverse osmosis. Proper granular activated carbon selection can
Fig. 5.12 Pressure sand filter and activated carbon filter
5 Water and Wastewater Treatment